Spatially uniform ground motion is an assumption that has often been made for structural analysis of arch dams. However, it has been recognized for many years that the ground motion in a canyon during an earthquake is amplified at the top of the canyon relative to the base. Pacoima Dam has been strongly shaken by the 1971 San Fernando earthquake and the 1994 Northridge earthquake. The acceleration records from both of these events demonstrate the spatial nonuniformity of the ground motion, but the amount and quality of the data made it difficult to study in detail. An opportunity to do so arose on January 13, 2001, when a relatively small magnitude 4.3 earthquake was recorded by an upgraded accelerometer array at Pacoima Dam.
\r\n\r\nFrequency-dependent topographic amplification is apparent at locations along both abutments at 80% height of the dam relative to the base. Also, the ground motion is delayed at the abutment locations compared to the base. The delays are consistent with seismic waves traveling upward along the canyon, and the waves appear to be dispersive since the delays are frequency-dependent. Both of these effects are quantified in this thesis by several approaches that involve varying degrees of approximation. A method for generating nonuniform ground motion from a single 3-component ground motion specified for one location in the canyon, e.g., at the base, is developed using transfer functions that quantify the amplification and phase delay. The method is demonstrated for the 2001 earthquake and the Northridge earthquake with several variations in the transfer functions.
\r\n\r\nThe 2001 earthquake records were also used for system identification. These results do not agree with results from a forced vibration experiment, which indicate a stiffer system. The earthquake must induce nonlinear vibrations, even though the excitation is quite small. This observation has implications for applications of structural health monitoring.
\r\n\r\nThe generated nonuniform ground motions are supplied as input to a finite element model. The results indicate that the method for generating nonuniform input produces ground motion that yields reasonable modeled responses, but there is some evidence that the time delays may be larger for stronger ground motion. Comparisons of the responses from ground motions generated with various implementations of amplification and time delays were made. For modeling purposes, accuracy of the amplification appears to be more important than the delays, which can be dealt with using a simpler approximation. The nonuniform input produces a response that is substantially different than the response produced by uniform input. The major difference is that while the pseudostatic response is a rigid body motion for uniform input, it causes deformation of the dam, mostly close to the abutments, for nonuniform input. In order to refine the proposed method for generating nonuniform ground motion, more data is required from Pacoima Dam and other structures with instrumentation coverage along the abutments.
" }, { "name": "Cua, Georgia B.", "degree": "PhD", "year": "2005", "title": "Creating the Virtual Seismologist: Developments in Ground Motion Characterization and Seismic Early Warning", "advisor": "Heaton, Thomas H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02092005-125601", "creators": [ { "name": { "family": "Cua", "given": "Georgia B." }, "id": "Cua-Georgia-B", "display_name": "Cua, Georgia B." } ], "advisors": [ { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "advisor", "display_name": "Heaton, Thomas H." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "chair", "display_name": "Beck, James L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Hauksson", "given": "Egill" }, "id": "Hauksson-E", "role": "member", "display_name": "Hauksson, Egill" } ], "option_major": [ "civileng" ], "doi": "10.7907/M926-J956", "abstract": "The Virtual Seismologist method for earthquake early warning uses a Bayesian approach to find the most probable magnitude and location estimates given the incoming ground motions envelopes from a rupturing earthquake. Ground motion ratios and ground motion envelope attenuation relationships are used to estimate magnitude and epicentral location as early as 3 seconds after the initial P wave detection. The use of prior information distinguishes this method from other proposed methods for seismic early warning. The state of health of the seismic network, previously observed seismicity, fault locations, and the Gutenberg-Richter relationship are the types of prior information useful in resolving trade-offs in the initial source estimates which are unresolved by the limited data. Short-term earthquake forecasts are ideal priors for seismic early warning.
\r\n\r\nHaving a high density of stations with real-time telemetry reduces the complexity involved in finding the most probable source estimates and communicating these estimates to early warning subscribers. The benefits of prior information are most evident for regions with low station density. Most early warning studies are focused exclusively on either the source estimation problem, or how subscribers use the warning information. The inclusion of prior information ultimately requires a level of coordination and communication between the network broadcasting the early warning information and the subscribers that is not consistent with this divide. The need for a more integrated approach to seismic early warning which considers the source estimation and user response as interacting and interrelated parts of a single problem is discussed.
\r\n\r\nA parameterization that decomposes observed ground motion envelopes into P-wave, S-wave, and ambient noise envelopes is developed and applied to a large suite of observed ground motion envelopes recorded within 200 km of 2.0 < M < 7.3 Southern California earthquakes. Separate attenuation relationships are developed to describe the magnitude, distance, and site dependence of various channels of P- and S-wave envelopes. The P-wave relationships allow the early warning source estimates to be obtained from observed P-wave amplitudes. Aside from early warning applications, these envelope attenuation relationships are used to investigate the average properties of ground motions recorded by the Southern California Seismic Network. Station-specific amplification factors for 150 Southern California Seismic Network stations were obtained for horizontal and vertical acceleration, velocity, and displacement amplitudes, and are included (Excel format) as external multimedia objects.
" }, { "name": "Clinton, John Francis", "degree": "PhD", "year": "2004", "title": "Modern Digital Seismology: Instrumentation, and Small Amplitude Studies in the Engineering World", "advisor": "Heaton, Thomas H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05202004-225044", "creators": [ { "name": { "family": "Clinton", "given": "John Francis" }, "id": "Clinton-John-Francis", "orcid": "0000-0001-8626-2703", "display_name": "Clinton, John Francis" } ], "advisors": [ { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "advisor", "display_name": "Heaton, Thomas H." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "civileng" ], "doi": "10.7907/DVSS-2290", "abstract": "The recording of ground motions is a fundamental part of both seismology and earthquake engineering. The current state-of-the-art 24-bit continuously recording seismic station is described, with particular attention to the frequency range and dynamic range of the seismic sensors typically installed. An alternative method of recording the strong-motions would be to deploy a velocity sensor rather than an accelerometer. This instrument has the required ability to measure the strongest earth motions, with enhanced long period sensitivity.
\r\n\r\nAn existing strong motion velocity sensor from Japan was tested for potential use in US seismic networks. It was found to be incapable of recording strong motions typically observed in the near source of even moderate earthquakes. The instrument was widely deployed near the M8.3 Sept 2003 Tokachi-Oki earthquake. The dataset corroborated our laboratory observations of low velocity saturations. The dataset also served to show all inertial sensors are equally sensitive to tilting, which is widespread in large earthquakes. High rate GPS data is also recorded during the event. Co-locating high-rate GPS with strong motion sensors is suggested to be currently the optimal method by which the complete and unambiguous deformation field at a station can be recorded.
\r\n\r\nA new application of the modern seismic station is to locate them inside structures. A test station on the 9th floor of Millikan Library is analysed. The continuous data-stream facilitates analysis of the building response to ambient weather, forced vibration tests, and small earthquakes that have occurred during its lifetime. The structure's natural frequencies are shown to be sensitive not only to earthquake excitation, but rainfall, temperature and wind. This has important implications on structural health monitoring, which assumes the natural frequencies of a structure do not vary significantly unless there is structural damage.
\r\n\r\nModerate to small earthquakes are now regularly recorded by dense, high dynamic range networks. This enhanced recording of the earthquake and its aftershock sequences makes possible the development of a Green's Function deconvolution approach for determining rupture parameters.
" }, { "name": "Krishnan, Swaminathan", "degree": "PhD", "year": "2004", "title": "Three-Dimensional Nonlinear Analysis of Tall Irregular Steel Buildings Subject to Strong Ground Motion", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02252004-181515", "creators": [ { "name": { "family": "Krishnan", "given": "Swaminathan" }, "id": "Krishnan-Swaminathan", "orcid": "0000-0002-2594-1523", "display_name": "Krishnan, Swaminathan" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Ravichandran", "given": "Guruswami" }, "id": "Ravichandran-G", "role": "member", "display_name": "Ravichandran, Guruswami" }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." } ], "option_major": [ "civileng" ], "doi": "10.7907/A00K-RQ42", "abstract": "Strong ground motion from a nearby fault has frequency content in the same range as the natural frequencies of tall buildings. This may have serious repercussions and is the topic of this dissertation.Buildings are designed per building code standards. But, are the code provisions adequate? Strong motion from large earthquakes has been recorded only in recent times in the near-source region. Have the current codes used this information to update tall structure design guidelines? Considerable damage has been observed in tall buildings from the Northridge, Kobe, Turkey, and Taiwan earthquakes. How will tall buildings designed per the latest code regulations perform if they were to be shaken by any of these earthquakes? This thesis attempts to answer these questions.
\r\n\r\nTall buildings by their nature are computationally intensive to analyze. They consist of thousands of degrees of freedom and when subjected to strong ground motion from a nearby source, exhibit inelastic response. Modeling this inelastic response requires an iterative approach that is computationally expensive. Furthermore, a large class of buildings, classified as irregular, exhibits complex behavior that can be studied only when the structures are modeled in their entirety. To this end, a three-dimensional analysis program, FRAME3D, has been developed incorporating two special beam-column elements -- the plastic hinge element and the elastofiber element that can model beams and columns in buildings accurately and efficiently, a beam-column joint element that can model inelastic joint deformation, and 4-noded elastic plane-stress elements to model floor slabs acting as diaphragms forcing the lateral force resisting frames in a building to act as one unit. The program is capable of performing time-history analyses of buildings in their entirety.
\r\n\r\nSix 19-story irregular steel moment frame buildings (with buildings 2A and 3A being variants of buildings 2 and 3, respectively) have been designed per the latest code (Uniform Building Code, 1997). Two of these buildings have reentrant corners and the other two have torsional irregularity. Their strength and ductility are assessed by performing pushover analyses on them. To assess their performance under strong shaking, FRAME3D models of these buildings are subjected to near-source strong motion records from the Iran earthquake (Mw = 7.3, Tabas Station) of 1978, the Northridge earthquake (Mw = 6.7, Sylmar Station) of 1994 and the Kobe earthquake (Mw = 6.9, Takatori Station) of 1995. None of the buildings collapsed under these strong events in the computer analyses. However, when compared against the acceptable limits for various performance levels in FEMA 356 document, the damage in terms of plastic deformation at the ends of beams and columns and at joints would render the buildings inadequate in terms f life safety in quite a few cases and would even indicate possible collapse in a couple of cases. Thus, in these terms, the code falls short of achieving its life safety objective, and the near-source factors introduced in the code in 1997 in recognition of the special features of near-source ground motion seem to be inadequate.
\r\n\r\nThe ductility demand, in terms of plastic rotation at the ends of beams and columns and in joints, on these buildings during this class of earthquakes is up to 6% of a radian, which is far greater than a typical limiting plastic rotation of 3% associated with fracture and consequent failure of large wide-flanged steel sections during experiments. Thus, if strength degradation due to fractures, local buckling, etc., were to be included in the analysis, then the results would likely to be worse, as far as the ability of these buildings to withstand these earthquakes without collapse is concerned.
\r\n\r\nDue to damage localization, the peak drifts observed in the structure far exceeded the inelastic drift limit in the code of 0.02 (in some cases up to 3 times). This points to serious non-structural damage to facades, interior dry wall, etc. Furthermore, large roof permanent offsets after the events indicate significant post-earthquake repair requiring considerable disruption and building closure.
\r\n\r\nColumn yielding was minimal thus validating the strong-column weak-beam criterion in the code. Redundancy factors used to assess the redundancy in the system need to take into account the case of torsionally sensitive structures where frames in both principal directions are simultaneously activated. Stress concentration was not observed at the reentrant corners in L-shaped buildings.
\r\n\r\nFinally, the data catalogued in this work could be useful for future code development and tall structure design guidelines.
" }, { "name": "Camelo, Vanessa Sabrina", "degree": "PhD", "year": "2003", "title": "Dynamic Characteristics of Woodframe Buildings", "advisor": "Beck, James L.; Hall, John F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06092003-150851", "creators": [ { "name": { "family": "Camelo", "given": "Vanessa Sabrina" }, "id": "Camelo-Vanessa-Sabrina", "display_name": "Camelo, Vanessa Sabrina" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "chair", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Porter", "given": "Keith A." }, "id": "Porter-K-A", "role": "member", "display_name": "Porter, Keith A." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Duron", "given": "Ziyad H." }, "id": "Duron-Z-H", "role": "member", "display_name": "Duron, Ziyad H." } ], "option_major": [ "civileng" ], "doi": "10.7907/GPHK-KA52", "abstract": "A database of dynamic characteristics of woodframe buildings was developed through analysis of recorded earthquake response and by forced vibration and shake-table testing. Modal identification was performed on eight sets of strong-motion records obtained from five buildings, and forced vibration tests were performed on five other buildings. The periods identified were sensitive to the amplitude of shaking, due to the reduction in lateral stiffness at stronger shaking levels. The equivalent viscous damping ratios were usually more than 10% of critical during earthquake shaking. A regression analysis was performed on the earthquake and forced vibration test data to obtain a simple, but reasonably accurate, period formula for woodframe buildings at low drift levels (less than 0.1%). Data obtained from the UC San Diego and UC Berkeley full-scale shake-table tests illustrate the shift in periods due to increasing shaking amplitude. Forced vibration tests of the UC Berkeley 3-story building before and after the shake-table tests showed how the periods and modeshapes shift due to damage. A simple analytical model of masses and springs was used to model the UC Berkeley test structure. The effects of diaphragm stiffness and mass distribution assumptions were evaluated and found to have a significant effect on the model torsional response. This model was used to find the equivalent wall stiffnesses giving frequency-response curves that best-fit the experimental data. These spring values were used to quantify the stiffness loss resulting from severe shaking of the structure, and the observed damage corresponded to stiffness losses of over 75%. The correlation between stiffness loss and damage to woodframe buildings has potential structural health monitoring implications." }, { "name": "Guyader, Andrew Charles", "degree": "PhD", "year": "2003", "title": "A Statistical Approach to Equivalent Linearization with Application to Performance-Based Engineering", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06012003-123539", "creators": [ { "name": { "family": "Guyader", "given": "Andrew Charles" }, "id": "Guyader-Andrew-Charles", "display_name": "Guyader, Andrew Charles" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Wallace", "given": "J. W." }, "id": "Wallace-J-W", "role": "member", "display_name": "Wallace, J. W." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "civileng" ], "doi": "10.7907/Z9HZ-9M41", "abstract": "A new methodology for calculating optimal effective linear parameters for use in predicting the earthquake response of structures is developed. The methodology is applied to several single-degree-of-freedom inelastic structural models subjected to a suite of earthquake acceleration time histories. Separately, far-field and near-field earthquakes are analyzed. Error distributions over a two-dimensional parameter space of period and damping are analyzed through a statistical approach with optimization criterion most applicable to structural design. Four hysteretic models are analyzed: bilinear, stiffness degrading, strength degrading and pinching. Initial structural periods are analyzed in groups for several second slope ratios (alpha) at different levels of ductility. It was discovered that as ductility increases, the accuracy of the effective parameters decrease but the consequences of bad parameter selection become less severe.
\r\n\r\nThe new effective parameters are intended for use in displacement-based structural analysis procedures as used in Performance-Based Engineering. Of the several procedures available, Nonlinear Static Procedures, such as the Capacity Spectrum Method, are widely used by structural engineers because the nonlinear characteristics of both structural components and the global structure are utilized without running a nonlinear time history analysis. Effective linear parameters are used in the Capacity Spectrum Method to calculate the expected displacement demand, or Performance Point, for a structure. Because several sources of error exist within the Capacity Spectrum Method, an analysis that isolates the error from the effective linear parameters is performed. The new effective linear parameters show considerable improvement over the existing effective linear equations. The existing linear parameters are extremely unconservative at the lower ductilities and conservative at the higher ductilities. The new parameters lead to a significant improvement in both cases.
\r\n\r\nA modification to the Capacity Spectrum Method is introduced to account for the new effective linear period. Currently, the Capacity Spectrum Method uses the secant period as the effective linear period. The modification preserves the basic Performance Point calculation. Finally, a new, entirely graphical solution procedure using a Locus of Performance Points provides crucial insight into the effects of strengthening, stiffening and increasing building ductility not available in the current procedure.
" }, { "name": "Yuen, Ka-Veng", "degree": "PhD", "year": "2002", "title": "Model Selection, Identification and Robust Control for Dynamical Systems", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02082012-113016272", "creators": [ { "name": { "family": "Yuen", "given": "Ka-Veng" }, "id": "Yuen-Ka-Veng", "orcid": "0000-0002-1755-6668", "display_name": "Yuen, Ka-Veng" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "chair", "display_name": "Beck, James L." }, { "name": { "family": "Burdick", "given": "Joel Wakeman" }, "id": "Burdick-J-W", "orcid": "0000-0002-3091-540X", "role": "member", "display_name": "Burdick, Joel Wakeman" }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Johnson", "given": "Erik A." }, "id": "Johnson-E-A", "role": "member", "display_name": "Johnson, Erik A." } ], "option_major": [ "civileng" ], "doi": "10.7907/YEV9-8X44", "abstract": "To fully exploit new technologies for response mitigation and structural health monitoring, improved system identification and controller design methodologies are desirable that explicitly treat all the inherent uncertainties. In this thesis, a probabilistic framework is presented for model selection, identification and robust control of smart structural systems under dynamical loads, such as those induced by wind or earthquakes. First, a probabilistic based approach is introduced for selecting the most plausible class of models for a dynamical system using its response measurements. The proposed approach allows for quantitatively comparing the plausibility of different classes of models among a specified set of classes.
\r\n\r\nThen, two probabilistic identification techniques are presented. The first one is for modal identification using nonstationary response measurements and the second one is for updating nonlinear models using incomplete noisy measurements only. These methods allow for updating of the uncertainties associated with the values of the parameters controlling the dynamic behavior of the structure by using noisy response measurements only. The probabilistic framework is very well-suited for solving this nonunique problem and the updated probabilistic description of the system can be used to design a robust controller of the system. It can also be used for structural health monitoring.
\r\n\r\nFinally, a reliability-based stochastic robust control approach is used to design the controller for an active control system. Feedback of the incomplete response at earlier time steps is used, without any state estimation. The optimal controller is chosen by minimizing the robust failure probability over a set of possible models for the system. Here, failure means excessive levels of one or more response quantities representative of the performance of the structure and the control devices. When calculating the robust failure probability, the plausibility of each model as a representation of the system's dynamic behavior is quantified by a probability distribution over the set of possible models; this distribution is initially based on engineering judgement, but it can be updated using the aforementioned system identification approaches if dynamic data become available from the structure. Examples are presented to illustrate the proposed controller design procedure, which includes the procedure of model selection, identification and robust control for smart structures.
" }, { "name": "Au, Siu-Kui", "degree": "PhD", "year": "2001", "title": "On the Solution of First Excursion Problems by Simulation with Applications to Probabilistic Seismic Performance Assessment", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03062014-085528325", "creators": [ { "name": { "family": "Au", "given": "Siu-Kui" }, "id": "Au-Siu-Kui", "orcid": "0000-0002-0228-1796", "display_name": "Au, Siu-Kui" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "chair", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Conte", "given": "Joel P." }, "id": "Conte-Joel-P", "orcid": "0000-0003-2068-7965", "role": "member", "display_name": "Conte, Joel P." }, { "name": { "family": "Katafygiotis", "given": "Lambros" }, "id": "Katafygiotis-Lambros", "orcid": "0000-0001-9275-9687", "role": "member", "display_name": "Katafygiotis, Lambros" } ], "option_major": [ "civileng" ], "doi": "10.7907/C0JQ-G051", "abstract": "In a probabilistic assessment of the performance of structures subjected to uncertain environmental\r\nloads such as earthquakes, an important problem is to determine the probability that the structural response exceeds some specified limits within a given duration of interest. This problem is known as the first excursion problem, and it has been a challenging problem in the theory of stochastic dynamics and reliability analysis. In spite of the enormous amount of attention the problem\r\nhas received, there is no procedure available for its general solution, especially for engineering\r\nproblems of interest where the complexity of the system is large and the failure probability is small.
\r\n\r\nThe application of simulation methods to solving the first excursion problem is investigated in this dissertation, with the objective of assessing the probabilistic performance of structures subjected to uncertain earthquake excitations modeled by stochastic processes. From a simulation perspective, the major difficulty in the first excursion problem comes from the large number of uncertain parameters\r\noften encountered in the stochastic description of the excitation. Existing simulation tools are examined, with special regard to their applicability in problems with a large number of uncertain parameters. Two efficient simulation methods are developed to solve the first excursion problem. The first method is developed specifically for linear dynamical systems, and it is found to be extremely efficient compared to existing techniques. The second method is more robust to the type of\r\nproblem, and it is applicable to general dynamical systems. It is efficient for estimating small failure probabilities because the computational effort grows at a much slower rate with decreasing failure probability than standard Monte Carlo simulation. The simulation methods are applied to assess the probabilistic performance of structures subjected to uncertain earthquake excitation. Failure\r\nanalysis is also carried out using the samples generated during simulation, which provide insight into the probable scenarios that will occur given that a structure fails.
\r\n" }, { "name": "Aagaard, Brad Thomas", "degree": "PhD", "year": "2000", "title": "Finite-Element Simulations of Earthquakes", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechThesis:04292016-090209111", "creators": [ { "name": { "family": "Aagaard", "given": "Brad Thomas" }, "id": "Aagard-Brad-Thomas", "display_name": "Aagaard, Brad Thomas" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." } ], "option_major": [ "civileng" ], "doi": "10.7907/T65C-9C94", "abstract": "This thesis discusses simulations of earthquake ground motions using prescribed ruptures and dynamic failure. Introducing sliding degrees of freedom led to an innovative technique for numerical modeling of earthquake sources. This technique allows efficient implementation of both prescribed ruptures and dynamic failure on an arbitrarily oriented fault surface. Off the fault surface the solution of the three-dimensional, dynamic elasticity equation uses well known finite-element techniques. We employ parallel processing to efficiently compute the ground motions in domains containing millions of degrees of freedom.
\r\n\r\nUsing prescribed ruptures we study the sensitivity of long-period near-source ground motions to five earthquake source parameters for hypothetical events on a strike-slip fault (Mw 7.0 to 7.1) and a thrust fault (Mw 6.6 to 7.0). The directivity of the ruptures creates large displacement and\r\nvelocity pulses in the ground motions in the forward direction. We found a good match between the severity of the shaking and the shape of the near-source factor from the 1997 Uniform Building Code for strike-slip faults and thrust faults with surface rupture. However, for blind thrust faults the peak displacement and velocities occur up-dip from the region with the peak near-source factor. We assert that a simple modification to the formulation of the near-source factor improves the match between the severity of the ground motion and the shape of the near-source factor.
\r\n\r\nFor simulations with dynamic failure on a strike-slip fault or a thrust fault, we examine what constraints must be imposed on the coefficient of friction to produce realistic ruptures under the application of reasonable shear and normal stress distributions with depth. We found that variation of the coefficient of friction with the shear modulus and the depth produces realistic rupture behavior in both homogeneous and layered half-spaces. Furthermore, we observed a dependence of the rupture speed on the direction of propagation and fluctuations in the rupture speed and slip rate as the rupture encountered changes in the stress field. Including such behavior in prescribed ruptures would yield more realistic ground motions.
" }, { "name": "Irfanoglu, Ayhan", "degree": "PhD", "year": "2000", "title": "Structural Design under Seismic Risk Using Multiple Performance Objectives", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechThesis:05052016-115652196", "creators": [ { "name": { "family": "Irfanoglu", "given": "Ayhan" }, "id": "Irfanoglu-Ayhan", "orcid": "0000-0001-8334-6717", "display_name": "Irfanoglu, Ayhan" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "chair", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "civileng" ], "doi": "10.7907/W5WE-TD86", "abstract": "Structural design is a decision-making process in which a wide spectrum of requirements, expectations, and concerns needs to be properly addressed. Engineering design criteria are considered together with societal and client preferences, and most of these design objectives are affected by the uncertainties surrounding a design. Therefore, realistic design frameworks must be able to handle multiple performance objectives and incorporate uncertainties from numerous sources into the process.
\r\n\r\nIn this study, a multi-criteria based design framework for structural design under seismic risk is explored. The emphasis is on reliability-based performance objectives and their interaction with economic objectives. The framework has analysis, evaluation, and revision stages. In the probabilistic response analysis, seismic loading uncertainties as well as modeling uncertainties are incorporated. For evaluation, two approaches are suggested: one based on preference aggregation and the other based on socio-economics. Both implementations of the general framework are illustrated\r\nwith simple but informative design examples to explore the basic features of the framework.
\r\n\r\nThe first approach uses concepts similar to those found in multi-criteria decision theory, and directly combines reliability-based objectives with others. This approach is implemented in a single-stage design procedure. In the socio-economics based approach, a two-stage design procedure is recommended in which societal preferences are treated through reliability-based engineering performance measures, but emphasis is also given to economic objectives because these are especially important to the structural designer's client. A rational net asset value formulation including losses from uncertain future earthquakes is used to assess the economic performance of a design. A recently developed assembly-based vulnerability analysis is incorporated into the loss estimation.
\r\n\r\nThe presented performance-based design framework allows investigation of various design issues and their impact on a structural design. It is a flexible one that readily allows incorporation of new methods and concepts in seismic hazard specification, structural analysis, and loss estimation.
\r\n\r\n" }, { "name": "Carlson, Anders Elof", "degree": "PhD", "year": "1999", "title": "Three-Dimensional Nonlinear Inelastic Analysis of Steel Moment-Frame Buildings Damaged by Earthquake Excitations", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02192014-110246738", "creators": [ { "name": { "family": "Carlson", "given": "Anders Elof" }, "id": "Carlson-Anders-Elof", "display_name": "Carlson, Anders Elof" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/7s2s-9r50", "abstract": "The Northridge earthquake of January 17, 1994, highlighted the two previously known problems of premature fracturing of connections and the damaging capabilities of near-source ground motion pulses. Large ground motions had not been experienced in a city with tall steel moment-frame buildings before. Some steel buildings exhibited fracture of welded connections or other types of structural degradation.
\r\n\r\nA sophisticated three-dimensional nonlinear inelastic program is developed that can accurately model many nonlinear properties commonly ignored or approximated in other programs. The program can assess and predict severely inelastic response of steel buildings due to strong ground motions, including collapse.
\r\n\r\nThree-dimensional fiber and segment discretization of elements is presented in this work. This element and its two-dimensional counterpart are capable of modeling various geometric and material nonlinearities such as moment amplification, spread of plasticity and connection fracture. In addition to introducing a three-dimensional element discretization, this work presents three-dimensional constraints that limit the number of equations required to solve various three-dimensional problems consisting of intersecting planar frames.
\r\n\r\nTwo buildings damaged in the Northridge earthquake are investigated to verify the ability of the program to match the level of response and the extent and location of damage measured. The program is used to predict response of larger near-source ground motions using the properties determined from the matched response.
\r\n\r\nA third building is studied to assess three-dimensional effects on a realistic irregular building in the inelastic range of response considering earthquake directivity. Damage levels are observed to be significantly affected by directivity and torsional response.
\r\n\r\nSeveral strong recorded ground motions clearly exceed code-based levels. Properly designed buildings can have drifts exceeding code specified levels due to these ground motions. The strongest ground motions caused collapse if fracture was included in the model. Near-source ground displacement pulses can cause columns to yield prior to weaker-designed beams. Damage in tall buildings correlates better with peak-to-peak displacements than with peak-to-peak accelerations.
\r\n\r\nDynamic response of tall buildings shows that higher mode response can cause more damage than first mode response. Leaking of energy between modes in conjunction with damage can cause torsional behavior that is not anticipated.
\r\n\r\nVarious response parameters are used for all three buildings to determine what correlations can be made for inelastic building response. Damage levels can be dramatically different based on the inelastic model used. Damage does not correlate well with several common response parameters.
\r\n\r\nRealistic modeling of material properties and structural behavior is of great value for understanding the performance of tall buildings due to earthquake excitations.
\r\n" }, { "name": "May, Bennett Scott", "degree": "PhD", "year": "1998", "title": "Probabilistic Robust Control: Theory and Applications", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03042014-093439011", "creators": [ { "name": { "family": "May", "given": "Bennett Scott" }, "id": "May-Bennett-Scott", "display_name": "May, Bennett Scott" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "chair", "display_name": "Beck, James L." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Doyle", "given": "John Comstock" }, "id": "Doyle-J-C", "role": "member", "display_name": "Doyle, John Comstock" } ], "option_major": [ "civileng" ], "doi": "10.7907/19jn-c337", "abstract": "In this work, the development of a probabilistic approach to robust control is motivated by structural control applications in civil engineering. Often in civil structural applications, a system's performance is specified in terms of its reliability. In addition, the model and input uncertainty for the system may be described most appropriately using probabilistic or \"soft\" bounds on the model and input sets. The probabilistic robust control methodology contrasts with existing H\u221e/\u03bc robust control methodologies that do not use probability information for the model and input uncertainty sets, yielding only the guaranteed (i.e., \"worst-case\") system performance, and no information about the system's probable performance which would be of interest to civil engineers.
\r\n\r\nThe design objective for the probabilistic robust controller is to maximize the reliability of the uncertain structure/controller system for a probabilistically-described uncertain excitation. The robust performance is computed for a set of possible models by weighting the conditional performance probability for a particular model by the probability of that model, then integrating over the set of possible models. This integration is accomplished efficiently using an asymptotic approximation. The probable performance can be optimized numerically over the class of allowable controllers to find the optimal controller. Also, if structural response data becomes available from a controlled structure, its probable performance can easily be updated using Bayes's Theorem to update the probability distribution over the set of possible models. An updated optimal controller can then be produced, if desired, by following the original procedure. Thus, the probabilistic framework integrates system identification and robust control in a natural manner.
\r\n\r\nThe probabilistic robust control methodology is applied to two systems in this thesis. The first is a high-fidelity computer model of a benchmark structural control laboratory experiment. For this application, uncertainty in the input model only is considered. The probabilistic control design minimizes the failure probability of the benchmark system while remaining robust with respect to the input model uncertainty. The performance of an optimal low-order controller compares favorably with higher-order controllers for the same benchmark system which are based on other approaches. The second application is to the Caltech Flexible Structure, which is a light-weight aluminum truss structure actuated by three voice coil actuators. A controller is designed to minimize the failure probability for a nominal model of this system. Furthermore, the method for updating the model-based performance calculation given new response data from the system is illustrated.
" }, { "name": "Chan, Eduardo", "degree": "PhD", "year": "1997", "title": "Optimal Design of Building Structures Using Genetic Algorithms", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechThesis:03132014-152131012", "creators": [ { "name": { "family": "Chan", "given": "Eduardo" }, "id": "Chan-Eduardo", "display_name": "Chan, Eduardo" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/4jea-yw44", "abstract": "A general framework for multi-criteria optimal design is presented which is well-suited for automated design of structural systems. A systematic computer-aided optimal design decision process is developed which allows the designer to rapidly evaluate and improve a proposed design by taking into account the major factors of interest related to different aspects such as design, construction, and operation.
\r\n\r\nThe proposed optimal design process requires the selection of the most promising choice of design parameters taken from a large design space, based on an evaluation using specified criteria. The design parameters specify a particular design, and so they relate to member sizes, structural configuration, etc. The evaluation of the design uses performance parameters which may include structural response parameters, risks due to uncertain loads and modeling errors, construction and operating costs, etc. Preference functions are used to implement the design criteria in a \"soft\" form. These preference functions give a measure of the degree of satisfaction of each design criterion. The overall evaluation measure for a design is built up from the individual measures for each criterion through a preference combination rule. The goal of the optimal design process is to obtain a design that has the highest overall evaluation measure - an optimization problem.
\r\n\r\nGenetic algorithms are stochastic optimization methods that are based on evolutionary theory. They provide the exploration power necessary to explore high-dimensional search spaces to seek these optimal solutions. Two special genetic algorithms, hGA and vGA, are presented here for continuous and discrete optimization problems, respectively.
\r\n\r\nThe methodology is demonstrated with several examples involving the design of truss and frame systems. These examples are solved by using the proposed hGA and vGA.
" }, { "name": "Gan, Wenshui", "degree": "PhD", "year": "1997", "title": "Earthquake Response of Steel Braces and Braced Steel Frames", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechThesis:03142014-103017013", "creators": [ { "name": { "family": "Gan", "given": "Wenshui" }, "id": "Gan-Wenshui", "display_name": "Gan, Wenshui" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Rosakis", "given": "Ares J." }, "id": "Rosakis-A-J", "role": "member", "display_name": "Rosakis, Ares J." } ], "option_major": [ "civileng" ], "doi": "10.7907/6zt3-2k51", "abstract": "This thesis consists of three parts. Chapter 2 deals with the dynamic buckling behavior of steel braces under cyclic axial end displacement. Braces under such a loading condition belong to a class of \"acceleration magnifying\" structural components, in which a small motion at the loading points can cause large internal acceleration and inertia. This member-level inertia is frequently ignored in current studies of braces and braced structures. This chapter shows that, under certain conditions, the inclusion of the member-level inertia can lead to brace behavior fundamentally different from that predicted by the quasi-static method. This result is to have significance in the correct use of the quasi-static, pseudo-dynamic and static condensation methods in the simulation of braces or braced structures under dynamic loading. The strain magnitude and distribution in the braces are also studied in this chapter.
\r\n\r\nChapter 3 examines the effect of column uplift on the earthquake response of braced steel frames and explores the feasibility of flexible column-base anchoring. It is found that fully anchored braced-bay columns can induce extremely large internal forces in the braced-bay members and their connections, thus increasing the risk of failures observed in recent earthquakes. Flexible braced-bay column anchoring can significantly reduce the braced bay member force, but at the same time also introduces large story drift and column uplift. The pounding of an uplifting column with its support can result in very high compressive axial force.
\r\n\r\nChapter 4 conducts a comparative study on the effectiveness of a proposed non-buckling bracing system and several conventional bracing systems. The non-buckling bracing system eliminates buckling and thus can be composed of small individual braces distributed widely in a structure to reduce bracing force concentration and increase redundancy. The elimination of buckling results in a significantly more effective bracing system compared with the conventional bracing systems. Among the conventional bracing systems, bracing configurations and end conditions for the bracing members affect the effectiveness.
\r\n\r\nThe studies in Chapter 3 and Chapter 4 also indicate that code-designed conventionally braced steel frames can experience unacceptably severe response under the strong ground motions recorded during the recent Northridge and Kobe earthquakes.
" }, { "name": "Hayen, Jeffrey Clyde", "degree": "PhD", "year": "1996", "title": "Response Control of Structural Systems Using Semi-Actively Controlled Interactions", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01032013-113224489", "creators": [ { "name": { "family": "Hayen", "given": "Jeffrey Clyde" }, "id": "Hayen-Jeffrey-Clyde", "display_name": "Hayen, Jeffrey Clyde" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Hunt", "given": "Melany L." }, "id": "Hunt-M-L", "role": "member", "display_name": "Hunt, Melany L." } ], "option_major": [ "appliedmech" ], "doi": "10.7907/2c70-e383", "abstract": "The objective of the research described herein is to demonstrate conditions under which controlled interactions between two structures or structural components can be made effective in reducing the response of structures that are subjected to seismic excitation. It is shown that the effectiveness depends upon such factors as the control\r\nstrategy implementation, the interaction element mechanical properties, and the parameters which characterize the dynamic behavior of the structural systems.
\r\n\r\nA study is conducted to examine the performance of a structural response control approach referred to as Active Interface Damping (AID). This control approach utilizes\r\ncontrolled interactions between two distinct structural systems or different components of a single structural system to reduce the resonance buildup that develops\r\nduring an external excitation. Control devices or elements may be employed to physically produce the interactions between the systems. The proposed control approach\r\ndiffers from some other control approaches in that the sensors, processors, and switching components all operate actively, whereas the interaction elements function passively. The major advantage of this semi-active control technology is that relatively large control forces can be generated with minimal power requirements, which is of prime importance for the control of relatively massive systems, such as structures.
\r\n\r\nIn the most simple form, the strategy of the control approach is to remove energy associated with vibration from only one system (the primary system). This process is\r\naccomplished through the transfer of energy to another system (the auxiliary system) by means of interaction elements, the dissipation of energy directly in the interaction elements, or a combination of both these methods. In a more complex form, the control strategy may be to minimize some composite response measure of the combined primary-auxiliary system. Only the most simple form of the control strategy is considered in the present study.
\r\n\r\nSeveral physical interpretations of the control approach are possible: one is that the systems represent two adjacent multi-story buildings; another is that the primary system represents a single multi-story building, while the auxiliary system could represent either an externally- situated resilient frame or a relatively small, unrestrained mass - or even be completely absent (in this latter scenario, the interaction elements are internally-mounted control devices). The interactions consist of reaction forces that are developed within and transmitted through the elements which are located between the two systems (or different points of a single system). The mechanical properties of these elements can be altered in real time by control signals, so the reaction forces applied to the systems may be changed, and the response control objective is achieved by actively changing the\r\ninteractions at the interface of the two systems (or different points of a single system).
\r\n\r\nInitially, a preliminary study of the proposed control approach is conducted within the specialized setting of linear single-degree-of-freedom (SDOF) primary and auxiliary\r\nsystems. Numerical simulations are performed for a series of control cases using horizontal ground accelerations from an ensemble of earthquake time histories as excitation input. Subsequently, a follow-on study of the proposed control approach is conducted for linear multiple-degree-of-freedom (MDOF) primary and auxiliary systems intended to represent actual structural systems. Based upon the investigation and insight obtained from the preliminary study, a limited number of control cases are considered\r\nwhich include those deemed most effective and implementable. Numerical simulations are again performed using the same excitation input as for the SDOF systems. The\r\ncontrol approach is targeted at reducing the response contribution from the fundamental or dominant mode of vibration associated with the primary system. Uniformly-discretized models of a 6-story primary structural system capable of only lateral deformations are considered in most cases. A few cases involving models of a 3-story primary\r\nstructural system are also examined.
\r\n\r\n" }, { "name": "Huang, Ching-Tung", "degree": "PhD", "year": "1996", "title": "On the Dynamic Response of Nonlinear Uncertain Systems", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10282019-124732191", "creators": [ { "name": { "family": "Huang", "given": "Ching-Tung" }, "id": "Huang-Ching-Tung", "display_name": "Huang, Ching-Tung" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "civileng" ], "doi": "10.7907/2xpp-3s50", "abstract": "This thesis presents an approach for performing second moment analyses of nonlinear dynamic systems with parameter uncertainty. The uncertain parameters are modeled as time-independent random variables. The set of orthogonal polynomials associated with the probability density function is used as the solution basis. When a deterministic excitation source is considered, the response variables are expanded in terms of a finite sum of these polynomials with time-dependent coefficients. The weighted residual method is employed to derive a set of deterministic nonlinear differential equations that can be solved numerically for evaluations of response statistics.
\r\n\r\nThis solution approach is further extended to nonlinear continuous systems involving inhomogeneous random media. A discrete representation is obtained via a spatial discretization procedure for the continuous response variables as well as the random continuum. Thus, the continuous random system can then be treated as in the case of the discrete random systems. The solution approach is applied to a study of a nonlinear random shear-beam model subjected to a near-field earthquake ground motion.
\r\n\r\nThe response uncertainty for nonlinear uncertain systems subjected to external stochastic excitation is also investigated. A general solution procedure based on equivalent linearization is presented. In this solution methodology, the instantaneous equivalent stiffness and damping matrices are approximated as quadratic random functions. The resulting Liapunov system with explicit random coefficients can then be solved using the newly developed solution approach. Applications to single-degree-of-freedom uncertain systems are given and the accuracy of the results is validated.
" }, { "name": "Halling, Marvin Wilford", "degree": "PhD", "year": "1995", "title": "Investigation of Base-Isolated Structures During Recent Earthquakes and Computer Simulations Utilizing Near-Source Long-Period Ground Motions", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10152007-141910", "creators": [ { "name": { "family": "Halling", "given": "Marvin Wilford" }, "id": "Halling-Marvin-Wilford", "display_name": "Halling, Marvin Wilford" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Wald", "given": "David J." }, "id": "Wald-D-J", "role": "member", "display_name": "Wald, David J." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "appliedmech" ], "doi": "10.7907/HWVH-DM02", "abstract": "Base isolation is a recently applied technology for building structures in the United States. To date, the three base-isolated buildings considered in this study have been subjected to earthquakes of varying magnitudes and epicentral distances. The records obtained from these instrumented buildings demonstrate low levels of excitation and small structural responses. In all cases, the maximum relative displacement of the roof to the foundation is less than 3 cm. However, an increasing quantity of near-source strong-motion records produces large spectral displacements of up to approximately 50-55 cm in the 2 to 2.5 sec period range for 15% damping. This suggests that long-period structures such as base-isolated structures would be vulnerable to these near-source ground motions.
\r\n\r\nThe current study contains two major parts. Part One consists of the identification and analysis of three existing base-isolated buildings in Southern California. The identification and analysis utilize the recorded motions of these structures from past earthquakes. System identification is useful for understanding the extent to which the structures enter the nonlinear realm and how much their properties change.
\r\n\r\nModels are constructed assuming completely elastic three-dimensional superstructures, with idealized bi-linear hysteretic elements for the isolating bearings. The properties used in the bearing models were taken from tests of the actual bearings before installation. The models were then verified by comparing their responses computed using the various recorded foundation ground motions, with the recorded responses of the actual structures. The models were adjusted to minimize the error of several response quantities.
\r\n\r\nPart Two contains computer simulations for the three structural models developed in Part One subjected to large-amplitude near-source ground motions. These structural models were subjected to two classes of ground motions. The first is a sampling of near-source recorded motion from past moderate-to-large earthquakes. The second is a group of synthetic near-source motions generated for a hypothetical M 7.0 earthquake. In some cases, the lateral response of the models exceeds the isolation gap, indicating that the displacement barrier would be impacted.
\r\n\r\nIn order to further study base-isolated buildings when the isolation bearings undergo large displacements, a typical base-isolated building (TBIB) model is used and the computer program 2D-BUMP is developed. This program includes the effects of a fully nonlinear superstructure, nonlinear springs acting as displacement barriers which engage at specified distances, and a tri-linear model for the elastomeric bearings. Using this model, several conclusions are drawn regarding the probable areal extent of damaging near-source ground motions from the M 7.0 event, as well as the behavior of base-isolated structures due to these near-source long-period ground motions.
" }, { "name": "Huang, Liping", "degree": "PhD", "year": "1995", "title": "Mode-Like Properties and Identification of Nonlinear Vibrating Systems", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12012011-113838877", "creators": [ { "name": { "family": "Huang", "given": "Liping" }, "id": "Huang-Liping", "display_name": "Huang, Liping" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Burdick", "given": "Joel Wakeman" }, "id": "Burdick-J-W", "role": "member", "display_name": "Burdick, Joel Wakeman" }, { "name": { "family": "Papadimitriou", "given": "Konstantinos" }, "id": "Papadimitriou-Konstantinos", "role": "member", "display_name": "Papadimitriou, Konstantinos" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/707b-jf67", "abstract": "A study is made of mode-like properties and identification of nonlinear systems and their applications in structural seismic analysis.
\r\n\r\nIn the thesis, mode-like behavior of nonlinear systems is examined. The modal frequencies and mode shapes of nonlinear systems are found to be dependent on the\r\nresponse. Based on approximation, amplitude-dependent mode shape is defined and approximate methods for calculation of modal frequencies and mode shapes (instantaneous and amplitude-dependent) are presented. Based on amplitude-dependent modal relationship, amplitude-dependent models of modal equations which are valid in large range of response\r\nand suitable for unique identification are proposed and the corresponding modal identification procedures are developed. The applicability of the new models and\r\nidentification algorithms is tested through the analysis of an ideal 3DOF nonlinear system.
\r\n\r\nAs applications, the seismic responses of a 47-story building and a 4-story building are investigated using the presented methods. The modal parameters and modal equations\r\nof the structures are identified.
" }, { "name": "Challa, Venkata Ramana Murty", "degree": "PhD", "year": "1992", "title": "Nonlinear seismic behaviour of steel planar moment-resisting frames", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10062011-075420910", "creators": [ { "name": { "family": "Challa", "given": "Venkata Ramana Murty" }, "id": "Challa-Venkata-Ramana-Murty", "display_name": "Challa, Venkata Ramana Murty" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." } ], "option_major": [ "civileng" ], "doi": "10.7907/jk1f-2d70", "abstract": "The nonlinear response of steel planar moment-resisting frames during strong earthquakes poses a strong need for accurately modelling inelastic behaviour and large displacements. This thesis attempts to provide realistic and efficient analytical tools to aid this study.
\r\n\r\nTwo large-displacement small-strain beam-column models are employed to include material and geometric nonlinearities. The first model assumes lumped plasticity, and discretises an element into segments. Axial force-Bending Moment strength interaction and flexural bowing are considered. Ten characteristic segment states are identified. An efficient numerical scheme is suggested to solve the nonlinear governing equations. This model only approximately represents the strength and stiffness of beam-columns.
\r\n\r\nA comprehensive finite element beam-column model is developed to more accurately model the strength and stiffness. A beam-column is discretised into segments, and further, each segment into one-dimensional fibres. A uniaxial cyclic constitutive law valid under arbitrary transient loading is proposed for structural steel. This physically motivated law incorporates the initial yield plateau, and provides explicit expressions for stress in terms of strain throughout the hysteretic path. This law is used to control the hysteretic loading of fibres.
\r\n\r\nA simple semi-empirical model is employed to analytically describe the highly nonlinear hysteretic behaviour of flexible joint panel zones in steel planar frames. Some modelling assumptions that may be made in frame analyses are evaluated. Numerical study of a building frame with flexible joints indicates that its collapse is sensitive to the joint panel zone design in addition to the ground motion.
\r\n" }, { "name": "Beck, Robert Teran", "degree": "PhD", "year": "1991", "title": "Fundamental Problems in the Application of Structural Identification Procedures to Damage Detection", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04112011-152332381", "creators": [ { "name": { "family": "Beck", "given": "Robert Teran" }, "id": "Beck-Robert-Teran", "display_name": "Beck, Robert Teran" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/ty3h-hz53", "abstract": "There are fundamental problems in the application of structural identification procedures to damage detection which still need to be resolved. The present study investigates the underlying issues and then provides a number of techniques which solve a series of unresolved problems. The techniques developed range from extensions and refinements of previous methods to the adaptation of novel homotopy methods.
\r\n\r\nThe results from simulated data show that ill-conditioning, non-uniqueness and temporal synchronization of the data are the most serious problems encountered. Criteria to resolve these are then put forth. From the experimental studies, however it becomes evident that modeling error is the most serious issue. The experimental results show, nonetheless, that even with large model errors, it is possible to localize the area of damage to within a sub-structure.
\r\n\r\nThe techniques are then applied to data obtained from a ten-story steel frame building. Previous studies on such structures have indicated large changes in the natural frequencies, especially during the San Fernando earthquake of February 9, 1971. The present study shows how changes in the natural frequencies and in the modeshapes are related to the degradation of the inter-story stiffness along the height of the building. Low amplitude forced vibration and ambient vibration test data yield one set of results: at these levels of motion the structure seems to retain much of its original uniform stiffness. This is true even after strong motion, leading to the notion that the building \"has healed\" with time. It is clear from the studies how this apparent stiffness is lost immediately once the strong motion of even moderate earthquakes has begun and it is thought t hat this is due to a combinations of effects. Results show that for the 1971 San Fernando earthquake, stiffness losses in the order of 50% occurred in the middle stories towards the end of the strong motion part of the seismic motion.
" }, { "name": "Katafygiotis, Lambros Solon", "degree": "PhD", "year": "1991", "title": "Treatment of Model Uncertainties in Structural Dynamics", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04252011-102457629", "creators": [ { "name": { "family": "Katafygiotis", "given": "Lambros Solon" }, "id": "Katafygiotis-Lambros-Solon", "display_name": "Katafygiotis, Lambros Solon" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/6s88-dn31", "abstract": "The uncertainties related to the modeling of the dynamic behavior of a structure are analyzed using a probabilistic approach.
\r\n\r\nFirst, the case of preliminary design is addressed, where the structure has not yet been built. A new efficient and accurate numerical method is proposed to investigate the resulting uncertainties in the structural response due to uncertainties in the modeling process, where engineering judgement is used to quantify the latter uncertainties.
\r\n\r\nSecond, the case where records of measured structural response are available to reduce the uncertainties in the structural models is addressed. The posterior probability distribution of the uncertain parameters is found to be very peaked at the values of some optimal parameters. These optimal parameters can be obtained by minimizing a positive-definite measure-of-fit function. A new efficient minimization algorithm is proposed to resolve difficulties in convergence of existing methods. The identifiability of the optimal parameters is also addressed. The problem of finding the whole set of the optimal models that have the same output at the observed degrees of freedom is resolved for the first time, by presenting an algorithm which methodically and efficiently searches the parameter space.
" }, { "name": "Papadimitriou, Konstantinos", "degree": "PhD", "year": "1991", "title": "Stochastic Characterization of Strong Ground Motion and Applications to Structural Response", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04142011-154846507", "creators": [ { "name": { "family": "Papadimitriou", "given": "Konstantinos" }, "id": "Papadimitriou-Konstantinos", "orcid": "0000-0002-9792-0481", "display_name": "Papadimitriou, Konstantinos" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/Y124-M904", "abstract": "This study addresses the problem of characterizing strong ground motion for the purpose of computing the dynamic response of structures to earthquakes. A new probabilistic ground motion model is proposed which can act as an interface between ground motion prediction studies and structural response studies. The model is capable of capturing, with at most nine parameters, all those features of the ground acceleration history which have an important influence on the dynamic response of linear and nonlinear structures, including the amplitude and frequency content nonstationarities of the shaking. Using a Bayesian probabilistic framework, a simple and effective statistical method is developed for extracting the \"optimal\" model from an actual accelerogram. The proposed ground motion model can be efficiently applied in simulations as well as analytical response and reliability studies of linear and inelastic structures.
\r\n\r\nThe random response of linear and nonlinear oscillators subjected to the proposed stochastic excitation is considered. The nonlinearity of the oscillator is accounted for by equivalent linearization. A formulation is developed which approximates the original lengthy expressions for the second-moment statistics of the transient response by much simpler expressions. The results provide insight into the characteristics of the nonstationary response and the effect of the ground motion nonstationarities. It is found that the temporal nonstationarity in the frequency content of the ground motion significantly influences the response of both linear and nonlinear structural models. Simulations are also used to study the sensitivity of inelastic structural response parameters to the details of the ground motion which are left \"random\" by the model. The results can also be used to provide a quantitative assessment of the expected structural damage associated with the ground motion described by the model.
\r\n" }, { "name": "Hou, Zhikun", "degree": "PhD", "year": "1990", "title": "Nonstationary Response of Structures and its Application to Earthquake Engineering", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechThesis:03112014-153421620", "creators": [ { "name": { "family": "Hou", "given": "Zhikun" }, "id": "Hou-Zhikun", "display_name": "Hou, Zhikun" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/db5g-6572", "abstract": "This thesis presents a simplified state-variable method to solve for the nonstationary response of linear MDOF systems subjected to a modulated stationary excitation in both time and frequency domains. The resulting covariance matrix and evolutionary spectral density matrix of the response may be expressed as a product of a constant system matrix and a time-dependent matrix, the latter can be explicitly evaluated for most envelopes currently prevailing in engineering. The stationary correlation matrix of the response may be found by taking the limit of the covariance response when a unit step envelope is used. The reliability analysis can then be performed based on the first two moments of the response obtained.
\r\n\r\nThe method presented facilitates obtaining explicit solutions for general linear MDOF systems and is flexible enough to be applied to different stochastic models of excitation such as the stationary models, modulated stationary models, filtered stationary models, and filtered modulated stationary models and their stochastic equivalents including the random pulse train model, filtered shot noise, and some ARMA models in earthquake engineering. This approach may also be readily incorporated into finite element codes for random vibration analysis of linear structures.
\r\n\r\nA set of explicit solutions for the response of simple linear structures subjected to modulated white noise earthquake models with four different envelopes are presented as illustration. In addition, the method has been applied to three selected topics of interest in earthquake engineering, namely, nonstationary analysis of primary-secondary systems with classical or nonclassical dampings, soil layer response and related structural reliability analysis, and the effect of the vertical components on seismic performance of structures. For all the three cases, explicit solutions are obtained, dynamic characteristics of structures are investigated, and some suggestions are given for aseismic design of structures.
" }, { "name": "Jensen, Hector A.", "degree": "PhD", "year": "1990", "title": "Dynamic Response of Structures with Uncertain Parameters", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechThesis:03112014-155226390", "creators": [ { "name": { "family": "Jensen", "given": "Hector A." }, "id": "Jensen-Hector-A", "display_name": "Jensen, Hector A." } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/5970-fp02", "abstract": "This thesis presents a technique for obtaining the response of linear structural systems with parameter uncertainties subjected to either deterministic or random excitation. The parameter uncertainties are modeled as random variables or random fields, and are assumed to be time-independent. The new method is an extension of the deterministic finite element method to the space of random functions.
\r\n\r\nFirst, the general formulation of the method is developed, in the case where the excitation is deterministic in time. Next, the application of this formulation to systems satisfying the one-dimensional wave equation with uncertainty in their physical properties is described. A particular physical conceptualization of this equation is chosen for study, and some engineering applications are discussed in both an earthquake ground motion and a structural context.
\r\n\r\nFinally, the formulation of the new method is extended to include cases where the excitation is random in time. Application of this formulation to the random response of a primary-secondary system is described. It is found that parameter uncertainties can have a strong effect on the system response characteristics.
" }, { "name": "Levine, Marie-Bernard P.", "degree": "PhD", "year": "1990", "title": "Accelerogram Processing Using Reliability Bounds and Optimal Correction Methods", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechThesis:03112014-160752285", "creators": [ { "name": { "family": "Levine", "given": "Marie-Bernard P." }, "id": "Levine-Marie-Bernard P", "display_name": "Levine, Marie-Bernard P." } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/vnh6-g135", "abstract": "This study addresses the problem of obtaining reliable velocities and displacements from accelerograms, a concern which often arises in earthquake engineering. A closed-form acceleration expression with random parameters is developed to test any strong-motion accelerogram processing method. Integration of this analytical time history yields the exact velocities, displacements and Fourier spectra. Noise and truncation can also be added. A two-step testing procedure is proposed and the original Volume II routine is used as an illustration. The main sources of error are identified and discussed. Although these errors may be reduced, it is impossible to extract the true time histories from an analog or digital accelerogram because of the uncertain noise level and missing data. Based on these uncertainties, a probabilistic approach is proposed as a new accelerogram processing method. A most probable record is presented as well as a reliability interval which reflects the level of error-uncertainty introduced by the recording and digitization process. The data is processed in the frequency domain, under assumptions governing either the initial value or the temporal mean of the time histories. This new processing approach is tested on synthetic records. It induces little error and the digitization noise is adequately bounded. Filtering is intended to be kept to a minimum and two optimal error-reduction methods are proposed. The \"noise filters\" reduce the noise level at each harmonic of the spectrum as a function of the signal-to-noise ratio. However, the correction at low frequencies is not sufficient to significantly reduce the drifts in the integrated time histories. The \"spectral substitution method\" uses optimization techniques to fit spectral models of near-field, far-field or structural motions to the amplitude spectrum of the measured data. The extremes of the spectrum of the recorded data where noise and error prevail are then partly altered, but not removed, and statistical criteria provide the choice of the appropriate cutoff frequencies. This correction method has been applied to existing strong-motion far-field, near-field and structural data with promising results. Since this correction method maintains the whole frequency range of the record, it should prove to be very useful in studying the long-period dynamics of local geology and structures." }, { "name": "Donlon, William Patrick, Jr.", "degree": "PhD", "year": "1989", "title": "Experimental Investigation of the Nonlinear Seismic Response of Concrete Gravity Dams", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05232007-074318", "creators": [ { "name": { "family": "Donlon", "given": "William Patrick, Jr." }, "id": "Donlon-William-Patrick-Jr", "display_name": "Donlon, William Patrick, Jr." } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "civileng" ], "doi": "10.7907/4mqw-6z67", "abstract": "The nonlinear seismic response of concrete gravity dams is investigated experimentally through the use of small-scale models. Of primary interest is crack formation, crack opening and closing, and sliding along crack planes. Also of concern is the stability of the structure after cracking. Three small-scale models (length scale - 115) of a single monolith of Pine Flat Dam are tested to determine the extent of such behavior and its effect on structural stability. The models are constructed of one polymer-based and two plaster-based materials developed for these experiments. The plaster-based materials fulfill the strength, stiffness, and density requirements established by the laws of similitude, while the polymer-based material fulfills only the stiffness and density requirements and is used only in the lower part of the dam where cracking is not expected. The excitation is a modified version of the N00E component of the 1940 Imperial Valley earthquake, applied to each model's base in the stream direction through a vibration table with high-frequency capability. Tests are performed with and without water in the reservoir. The response of each earthquake test is presented in the form of acceleration and displacement time histories, Fourier spectra, and frames taken from high-speed films of the model's response. The results of the experiments indicate that the neck region of a concrete gravity dam is most susceptible to cracking, although crack profiles can differ as a result of variations in excitation, material properties, and construction techniques. These results also indicate alternate design techniques which could improve the seismic stability of a cracked gravity dam.
" }, { "name": "El-Aidi, Bahaa", "degree": "PhD", "year": "1989", "title": "Nonlinear Earthquake Response of Concrete Gravity Dam Systems", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06072007-132404", "creators": [ { "name": { "family": "El-Aidi", "given": "Bahaa" }, "id": "El-Aidi-Bahaa", "display_name": "El-Aidi, Bahaa" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Leonard", "given": "Anthony" }, "id": "Leonard-A", "role": "member", "display_name": "Leonard, Anthony" } ], "option_major": [ "civileng" ], "doi": "10.7907/n2f8-rv33", "abstract": "The earthquake response of concrete gravity dam systems is investigated with emphasis on the nonlinear behavior associated with tensile concrete cracking and water cavitation. A single dam-monolith is considered and is assumed to respond independently as a two-dimensional system under plane stress conditions. The two-dimensional assumption is also extended to model the compressible water body impounded upstream of the dam. Standard displacement-based finite element techniques are used to spatially discretize the field equations and produce a single symmetric matrix equation for the dam-water system. Energy dissipation in the reservoir, through radiation in the infinite upstream direction and absorption at the bottom, is approximately accounted for, and a set of numerical examples is presented to demonstrate the accuracy of the present formulation in modeling the linear earthquake response of infinite reservoirs. An approximate procedure to account for dam-foundation interaction is incorporated based on the response of a rigid plate attached to a three-dimensional viscoelastic half-space.
\r\n\r\nWater cavitation is modeled by a smeared approach which uses a bilinear pressure-strain relation. It is shown that the water response becomes dominated by spurious high frequency oscillations upon closure of cavitated regions, and improved results can be obtained by using some stiffness-proportional damping in the water reservoir. As demonstrated in an example analysis of Pine Flat Dam (linear dam), cavitation occurs in the upper part of the reservoir along the dam face, unlike other investigations which show cavitated regions at considerable distances from the dam, and both the tensile pressure cutoffs and compressive impacts have a minor effect on the dam response.
\r\n\r\nTensile cracks are incorporated using the smeared crack approach, and sliding along closed cracks is allowed. Coupling effects inherent in the finite element formulation are explained, and their influence on open and closed cracks is investigated. Propagation of cracks is monitored in an interactive environment which uses an equivalent strength criterion and allows for user input; remeshing is avoided. The algorithm adopted here produces narrow cracks, unlike many other investigations which show large zones of cracking. An extensive numerical study of Pine Flat Dam demonstrates some interesting features of the nonlinear response of the system, identifies potential failure mechanisms, and reveals a number of difficulties that the analysis encounters. Although no instability of the dam occurs, the numerical difficulties will have to be overcome before definite conclusions regarding stability can be made. It is shown that cracking reduces the hydrodynamic pressures in the reservoir and, hence, reduces water cavitation.
" }, { "name": "Nowak, Paul Scott", "degree": "PhD", "year": "1989", "title": "Effect of Nonuniform Seismic Input on Arch Dams", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06042013-091930444", "creators": [ { "name": { "family": "Nowak", "given": "Paul Scott" }, "id": "Nowak-Paul-Scott", "display_name": "Nowak, Paul Scott" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "appliedmech" ], "doi": "10.7907/zbd0-ty45", "abstract": "Standard earthquake analyses of civil engineering structures use uniform ground motions even though considerable variations in both amplitude and phase can occur along the foundation interface for long-span bridges and large dams. The objective of this thesis is to quantify the effect that these nonuniformities have on the structural response.
\r\n\r\nThe nonuniform, free-field motions of the foundation interface are assumed to be caused by incident plane body waves. The medium in which these waves travel is a linear, elastic half-space containing a canyon of uniform cross section in which the structure is placed. The solutions for the free-field motions that are due to incident SH, P and SV waves are calculated using the boundary element method.
\r\n\r\nAn analysis of Pacoima (arch) dam located near Los Angeles, California, is performed for both uniform and nonuniform excitations. The important effect of nonuniformities in the free-field motions, sometimes leading to a decrease in the dam response and sometimes to an increase, is quantified.
" }, { "name": "Dowling, Michael John", "degree": "PhD", "year": "1988", "title": "Nonlinear Seismic Analysis of Arch Dams", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06112008-155515", "creators": [ { "name": { "family": "Dowling", "given": "Michael John" }, "id": "Dowling-Michael-John", "display_name": "Dowling, Michael John" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." } ], "option_major": [ "civileng" ], "doi": "10.7907/DJ4P-9393", "abstract": "A nonlinear finite element procedure for arch dams is described in which the gradual opening and closing of vertical contraction joints and predetermined horizontal cracking planes are considered. A special joint element approximately represents the deformations due to plane sections not remaining plane at each open joint and allows a single shell element discretization in the thickness direction to be used for the dam. Compressive and sliding nonlinearities are not included. Finite element treatments are also used for the water, assumed incompressible, and for the foundation rock, assumed massless, with all degrees of freedom (dof) off the dam condensed out. For efficiency in the computations, the condensed water and foundation matrices are localized in a way which maintains good accuracy. The response of Pacoima Dam to the 1971 San Fernando ground motion recorded on a ridge over one abutment and scaled by two-thirds is computed first for water at the intermediate level that existed during the 1971 earthquake and then for full reservoir. In the first analysis, the dam exhibits pronounced opening and separation of the contraction joints, allowing violation of the no-slip assumption. The presence of a full reservoir greatly increases the dam response, enough to bring some of the assumptions of the analysis into question. Reducing the ground motion scale to 0.44 with full reservoir drops the response back to a reasonable level, but the contraction joint separations remain.
\r\n\r\n" }, { "name": "Dur\u00f3n, Ziyad Hassan", "degree": "PhD", "year": "1988", "title": "Experimental and Finite Element Studies of a Large Arch Dam", "advisor": "Hall, John F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03142013-082003398", "creators": [ { "name": { "family": "Dur\u00f3n", "given": "Ziyad Hassan" }, "id": "Dur\u00f3n-Ziyad-Hassan", "display_name": "Dur\u00f3n, Ziyad Hassan" } ], "advisors": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "advisor", "display_name": "Hall, John F." } ], "committee": [ { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "chair", "display_name": "Hall, John F." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Raichlen", "given": "Fredric" }, "id": "Raichlen-F", "role": "member", "display_name": "Raichlen, Fredric" }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." } ], "option_major": [ "civileng" ], "doi": "10.7907/e0rt-g677", "abstract": "Forced vibration field tests and finite element studies have been conducted on Morrow Point (arch) Dam in order to investigate dynamic dam-water interaction and water compressibility. Design of the data acquisition system incorporates several special features to retrieve both amplitude and phase of the response in a low signal to noise environment. These features contributed to the success of the experimental program which, for the first time, produced field evidence of water compressibility; this effect seems to play a significant role only in the symmetric response of Morrow Point Dam in the frequency range examined. In the accompanying analysis, frequency response curves for measured accelerations and water pressures as well as their resonating shapes are compared to predictions from the current state-of-the-art finite element model for which water compressibility is both included and neglected. Calibration of the numerical model employs the antisymmetric response data since they are only slightly affected by water compressibility, and, after calibration, good agreement to the data is obtained whether or not water compressibility is included. In the effort to reproduce the symmetric response data, on which water compressibility has a significant influence, the calibrated model shows better correlation when water compressibility is included, but the agreement is still inadequate. Similar results occur using data obtained previously by others at a low water level. A successful isolation of the fundamental water resonance from the experimental data shows significantly different features from those of the numerical water model, indicating possible inaccuracy in the assumed geometry and/or boundary conditions for the reservoir. However, the investigation does suggest possible directions in which the numerical model can be improved.
" }, { "name": "Peng, Chia-Yen", "degree": "PhD", "year": "1988", "title": "Generalized Modal Identification of Linear and Nonlinear Dynamic Systems", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03132013-163747278", "creators": [ { "name": { "family": "Peng", "given": "Chia-Yen" }, "id": "Peng-Chia-Yen", "display_name": "Peng, Chia-Yen" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." } ], "option_major": [ "appliedmech" ], "doi": "10.7907/e70y-gz66", "abstract": "This dissertation is concerned with the problem of determining the dynamic characteristics of complicated engineering systems and structures from the measurements made during dynamic tests or natural excitations. Particular attention is given to the identification and modeling of the behavior of structural dynamic systems in the nonlinear hysteretic response regime. Once a model for the system has been identified, it is intended to use this model to assess the condition of the system and to predict the response to future excitations.
\r\n\r\nA new identification methodology based upon a generalization of the method of modal identification for multi-degree-of-freedom dynaimcal systems subjected to base motion is developed. The situation considered herein is that in which only the base input and the response of a small number of degrees-of-freedom of the system are measured. In this method, called the generalized modal identification method, the response is separated into \"modes\" which are analogous to those of a linear system. Both parametric and nonparametric models can be employed to extract the unknown nature, hysteretic or nonhysteretic, of the generalized restoring force for each mode.
\r\n\r\nIn this study, a simple four-term nonparametric model is used first to provide a nonhysteretic estimate of the nonlinear stiffness and energy dissipation behavior. To extract the hysteretic nature of nonlinear systems, a two-parameter distributed element model is then employed. This model exploits the results of the nonparametric identification as an initial estimate for the model parameters. This approach greatly improves the convergence of the subsequent optimization process.
\r\n\r\nThe capability of the new method is verified using simulated response data from a three-degree-of-freedom system. The new method is also applied to the analysis of response data obtained from the U.S.-Japan cooperative pseudo-dynamic test of a full-scale six-story steel-frame structure.
\r\n\r\nThe new system identification method described has been found to be both accurate and computationally efficient. It is believed that it will provide a useful tool for the analysis of structural response data.
" }, { "name": "Jayakumar, Paramsothy", "degree": "PhD", "year": "1987", "title": "Modeling and Identification in Structural Dynamics", "advisor": "Beck, James L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02272019-105053083", "creators": [ { "name": { "family": "Jayakumar", "given": "Paramsothy" }, "id": "Jayakumar-Paramsothy", "display_name": "Jayakumar, Paramsothy" } ], "advisors": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "advisor", "display_name": "Beck, James L." } ], "committee": [ { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "chair", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "civileng" ], "doi": "10.7907/1wwx-ca82", "abstract": "Analytical modeling of structures subjected to ground motions is an important aspect of fully dynamic earthquake-resistant design. In general, linear models are only sufficient to represent structural responses resulting from earthquake motions of small amplitudes. However, the response of structures during strong ground motions is highly nonlinear and hysteretic.
\r\n\r\nSystem identification 1s an effective tool for developing analytical models from experimental data. Testing of full-scale prototype structures remains the most realistic and reliable source of inelastic seismic response data. Pseudo-dynamic testing is a recently developed quasi-static procedure for subjecting full-scale structures to simulated earthquake response. The present study deals with structural modeling and the determination of optimal linear and nonlinear models by applying system identification techniques to elastic and inelastic pseudo-dynamic data from a full-scale, six-story steel structure.
\r\n\r\nIt is shown that the feedback of experimental errors during the pseudo-dynamic tests significantly affected the higher modes and led to an effective negative damping for the third mode. The contributions of these errors are accounted for and the small-amplitude modal properties of the test structure are determined. These properties are in agreement with the values obtained from a shaking table test of a 0.3 scale model.
\r\n\r\nThe nonlinear hysteretic behavior of the structure during strong ground motions is represented by a general class of Masing models. A simple model belonging to this class is chosen. with parameters which can be estimated theoretically, thereby making this type of model potentially useful during the design stages. The above model is identified from the experimental data and then its prediction capability and application in seismic design and analysis are examined.
" }, { "name": "Moser, Michael Anthony", "degree": "PhD", "year": "1987", "title": "The Response of Stick-Slip Systems to Random Seismic Excitation", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04122019-165004448", "creators": [ { "name": { "family": "Moser", "given": "Michael Anthony" }, "id": "Moser-Michael-Anthony", "display_name": "Moser, Michael Anthony" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." } ], "option_major": [ "appliedmech" ], "doi": "10.7907/ntjg-hg45", "abstract": "This thesis examines the response of stick-slip, or frictional, systems to harmonic and random excitation. Two frictional models are considered: constant slip force, or Coulomb, friction, and displacement dependent slip force, used to model a caster, or pivoting wheel. The response to harmonic excitation of systems exhibiting both frictional models is determined using the method of slowly varying parameters. Changes in the response amplitude of both systems caused by the addition of a linear centering mechanism are also examined.
\r\n\r\nThe response of the system with displacement dependent slip force is examined under Gaussian mean zero white noise excitation using the generalized equivalent linearization method. It is shown that a lower bound is obtained from the Coulomb friction system's response.
\r\n\r\nFor filtered random excitation, linearization methods are shown to predict erroneous displacement trends for the Coulomb system when the input has no spectral content at zero frequency. When the excitation is modeled as a Poisson pulse process, an approximate method exhibiting the proper displacement trends can be constructed. The method is shown to be accurate over a broad range of input parameters if overlaps in the input pulses are considered. A set of excitation parameters consistent with seismic events is then used to estimate final rms displacements as a function of coefficient of friction.
" }, { "name": "Paparizos, Leonidas G.", "degree": "PhD", "year": "1987", "title": "Some Observations on the Random Response of Hysteretic Systems", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04152019-163242410", "creators": [ { "name": { "family": "Paparizos", "given": "Leonidas G." }, "id": "Paparizos-Leonidas-G", "display_name": "Paparizos, Leonidas G." } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." } ], "option_major": [ "civileng" ], "doi": "10.7907/w5wv-5f87", "abstract": "In this thesis, the nature of hysteretic response behavior of structures subjected to strong seismic excitation, is examined. The earthquake ground motion is modeled as a stochastic process and the dependence of the response on system and excitation parameters, is examined. Consideration is given to the drift of structural systems and its dependence on the low frequency content of the earthquake spectrum. It is shown that commonly used stochastic excitation models, are not able to accurately represent the low frequency content of the excitation. For this reason, a stochastic model obtained by filtering a modulated white noise signal through a second order linear filter is used in this thesis.
\r\n\r\nA new approach is followed in the analysis of the elasto-plastic system. The problem is formulated in terms of the drift, defined as the sum of yield increments associated with inelastic response. The solution scheme is based on the properties of discrete Markov process models of the yield increment process, while the yield increment statistics are expressed in terms of the probability density of the velocity and elastic component of the displacent response. Using this approach, an approximate exponential and Rayleigh distribution for the yield increment and yield duration, respectively, are established. It is suggested that, for duration of stationary seismic excitation of practical significance, the drift can be considered as Brownian motion. Based on this observation, the approximate Gaussian distribution and the linearly divergent mean square value of the process, as well as an expression for the probability distribution of the peak drift response, are obtained. The validation of these properties is done by means of a Monte Carlo simulation study of the random response of an elastoplastic system.
\r\n\r\nBased on this analysis, the first order probability density and first passage probabilities for the drift are calculated from the probability density of the velocity and elastic component of the response, approximately obtained by generalized equivalent linearization. It is shown that the drift response statistics are strongly dependent on the normalized characteristic frequency and strength of the excitation, while a weaker dependence on the bandwidth of excitation is noted.
" }, { "name": "Peek, Ralf", "degree": "PhD", "year": "1986", "title": "Analysis of Unanchored Liquid Storage Tanks under Seismic Loads", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10232019-110854163", "creators": [ { "name": { "family": "Peek", "given": "Ralf" }, "id": "Peek-Ralf", "orcid": "0000-0002-2469-3644", "display_name": "Peek, Ralf" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "chair", "display_name": "Jennings, Paul C." }, { "name": { "family": "Babcock", "given": "Charles D." }, "id": "Babcock-C-D", "role": "member", "display_name": "Babcock, Charles D." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "civileng" ], "doi": "10.7907/w43k-hj54", "abstract": "Because of cost, cylindrical, ground supported liquid storage tanks are often not fixed to their foundation, even in seismic areas. For such an unanchored tank made of steel, the weight of the cylindrical shell is mostly insufficient to prevent local uplift due to seismic overturning moments. Although, for properly designed connecting pipes, uplift itself is not a problem, it results in larger vertical compressive stresses in the tank wall at the base, opposite to where the uplift occurs. These compressive stresses have often caused buckling, even in earthquakes which did not cause much damage to other structures.
\r\n\r\nVarious investigators have studied the behavior of unanchored tanks experimentally, but, due to the complexity of the problem, so far very little theoretical work has been done. Two methods of analysis for static lateral loads are presented: An approximate one in which the restraining action of the base plate is modeled by nonlinear Winkler springs, and a more comprehensive one in which the two dimensional nonlinear contact problem is solved by the finite difference energy method. The theoretical results are compared with existing experimental results and with the approach from current U.S. design standards. The theoretical peak compressive stresses are in good agreement with the experimental results, but in some cases exceed those calculated by the code method by more than 100%.
\r\n\r\nFinally, a new design concept, by which the tank wall is preuplifted all around its circumference by inserting a ring filler is described. It will be shown theoretically and experimentally that this preuplift method substantially improves the lateral load capacity.
" }, { "name": "Chelvakumar, Kasivisvanathan", "degree": "PhD", "year": "1985", "title": "A Simple Strain-Space Plasticity Model for Clays", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01022019-123640478", "creators": [ { "name": { "family": "Chelvakumar", "given": "Kasivisvanathan" }, "id": "Chelvakumar-Kasivisvanathan", "display_name": "Chelvakumar, Kasivisvanathan" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Coles", "given": "Donald Earl" }, "id": "Coles-D-E", "role": "member", "display_name": "Coles, Donald Earl" }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "mecheng" ], "doi": "10.7907/kcgf-c188", "abstract": "This thesis develops and demonstrates a simple strain-space constitutive model for wet clays. It has been seen that a strain-space formulation of the constitutive behavior of engineering materials facilitates the solution of boundary value problems involving these materials. Soil, because of its multi-phase granular constitution poses challenging problems in constitutive modeling. Although several stress-space plasticity models exist for soils, they are not used commonly in engineering practice due to their complexity. It is attempted herein to develop and test a simple model which could result in simplified solutions for some soil problems.
\r\n\r\nThe model is based on the experimentally observed physical behavior of soil. Certain approaches alien to conventional plasticity. Are employed so that the material behavior is closely predicted without sacrificing the simplicity of the model.
\r\n\r\nThe model is initially developed for triaxial load systems. Its predictions are then tested against other model predictions and experimental data. The model is then generalized. The generalization renders the model capable of handling general stress-strain states and finite deformations.
\r\n\r\nFinally, the generalized model is used to solve an idealization of a practical problem. The problem of a pile driven into a soil medium is idealized as an expanding cavity in a homogeneous infinite medium. The solution predicted by the strain-space model is compared with other model predictions and test results.
" }, { "name": "Cifuentes, Arturo O.", "degree": "PhD", "year": "1985", "title": "System Identification of Hysteretic Structures", "advisor": "Iwan, Wilfred D.; Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12192018-105342164", "creators": [ { "name": { "family": "Cifuentes", "given": "Arturo O." }, "id": "Cifuentes-Arturo-O", "orcid": "0000-0001-9689-3939", "display_name": "Cifuentes, Arturo O." } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "co-advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "chair", "display_name": "Jennings, Paul C." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "member", "display_name": "Iwan, Wilfred D." } ], "option_major": [ "appliedmech" ], "doi": "10.7907/p43n-j428", "abstract": "This thesis is concerned with the earthquake response of hysteretic structures subjected to strong ground acceleration. Several earthquake records corresponding to different instrumented buildings are analyzed. Based on these observations, a new model for the dynamic behavior of reinforced concrete buildings is proposed. In addition, a suitable system identification algorithm to be used with this new model is introduced. This system identification algorithm is based upon matching the restoring force behavior of the structure rather than the time history of the response. As a consequence, the new algorithm exhibits significant advantages from a computational point of view. Same numerical examples using actual earthquake data are discussed.
" }, { "name": "Jeong, Garrett Duane", "degree": "PhD", "year": "1985", "title": "Cumulative Damage of Structures Subjected to Response Spectrum Consistent Random Processes", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04052019-121036771", "creators": [ { "name": { "family": "Jeong", "given": "Garrett Duane" }, "id": "Jeong-Garrett-Duane", "display_name": "Jeong, Garrett Duane" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "orcid": "0000-0002-7863-5060", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Knauss", "given": "Wolfgang Gustav" }, "id": "Knauss-W-G", "role": "member", "display_name": "Knauss, Wolfgang Gustav" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/97b3-2427", "abstract": "A theoretical analysis of the effect of duration on the damage of structures subjected to earthquakes is presented. Earthquake excitation is modeled as a nonstationary random process. Estimates of the first-passage probability of a simple oscillator are employed to choose modulated Gaussian random processes consistent with a prescribed response spectrum. The response spectrum is assumed to be specified independent of the duration. Expressions for the mean damage of a structure are derived using an approach similar to the Miner-Palmgren rule for failure caused by cyclic loads. The expected damage expressions are then evaluated for a structure subjected to modulated Gaussian random processes of varying duration.
\r\n\r\nTwo types of structures are examined: a steel structure and a reinforced concrete structure. Results are presented for systems with constant linear stiffness and a particular form of softening behavior. The nonlinearity of the softening system is accounted for by statistical linearization. The level of expected damage is found to be a strong function of both the duration of the excitation and the ductility of the response.
" }, { "name": "Maragakis, Emmanuel", "degree": "PhD", "year": "1985", "title": "A Model for the Rigid Body Motions of Skew Bridges", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02132019-102055741", "creators": [ { "name": { "family": "Maragakis", "given": "Emmanuel" }, "id": "Maragakis-Emmanuel", "display_name": "Maragakis, Emmanuel" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "chair", "display_name": "Jennings, Paul C." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Wu", "given": "Theodore Yao-tsu" }, "id": "Wu-T-Y-T", "role": "member", "display_name": "Wu, Theodore Yao-tsu" } ], "option_major": [ "civileng" ], "doi": "10.7907/YWES-NJ36", "abstract": "This thesis investigates the rigid body motions of skew bridges, concentrating on the in-plane translational and rotational displacements of the bridge deck induced by impact between the deck and the abutments. Experience in the San Fernando Earthquake of February 9, 1971 demonstrates that this feature is particularly important for skew bridges.
\r\n\r\nA simple model, in which the bridge deck is represented by a rigid rod restricted by column and abutment springs is examined first. This model illustrates the mechanism by which in-plane rotational vibrations is triggered after the closure of the gap between the bridge deck and the abutment. It also shows that the force-deflection relations of the columns and the abutments are particularly important features for the response of the bridge. Methods for the exact and approximate estimation of the elastic stiffness of elastically founded, tapered bridge columns with octagonal cross section are presented next. The methods are applied to a bridge used later as an example. In addition, the yielding of the columns is examined and the force-deflection relations for bending about two orthogonal axes are estimated.
\r\n\r\nThe abutments are treated as rigid bodies and the soil embankments as Winkler Foundations with elastic spring constants increasing with depth. For the examination of the yielding of soil the Rankine theory is used. Based on these assumptions an approximate force deflection relation for the abutments is constructed.
\r\n\r\nThe response of a more complicated bridge model applied to a bridge near Riverside, California is examined at the end of the thesis and examples of the results are given. This model, in which the bridge deck is still represented as a rigid rod, has three in-plane degrees of freedom: two orthogonal displacements and a rotation, and is capable of capturing many of the more important features of the nonlinear, yielding response of skew bridges during strong earthquake shaking.
" }, { "name": "Pak, Ronald Y.S.", "degree": "PhD", "year": "1985", "title": "Dynamic Response of a Partially Embedded Bar Under Transverse Excitations", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01222019-152401456", "creators": [ { "name": { "family": "Pak", "given": "Ronald Y.S." }, "id": "Pak-Ronald-Y-S", "display_name": "Pak, Ronald Y.S." } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "chair", "display_name": "Jennings, Paul C." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Sternberg", "given": "Eli" }, "id": "Sternberg-E", "role": "member", "display_name": "Sternberg, Eli" }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." }, { "name": { "family": "Wu", "given": "Theodore Yao-tsu" }, "id": "Wu-T-Y-T", "role": "member", "display_name": "Wu, Theodore Yao-tsu" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/pp2r-fc10", "abstract": "This dissertation is concerned with the dynamic response of a finite flexible bar partially embedded in a half-space, under transverse loadings. The loadings are applied at the unembedded end of the bar and may, in general, be a combination of time-harmonic shear and moment. The problem is intended to serve as a fundamental idealization for the dynamic analysis of piles or other embedded foundations whose flexibilities are not negligible.
\r\n\r\nBy treating the bar as a one-dimensional structure and the half-space as a three-dimensional elastic continuum, the interaction problem is formulated as a Fredholm integral equation of the second kind. The essential tool required in the formulation is a group of Green's functions which describe the response of an elastic half-space to a finite, distributed, buried source which acts in the lateral direction. By means of a technique developed for a class of three-dimensional asymmetric wave propagation problems, the Green's functions are derived as integral representations. A numerical procedure for the computation of the semi-infinite Hankel-type integrals involved is presented which is free of the basic difficulties commonly encountered in such problems. Owing to the special nature of the kernel function, a numerical scheme which contains the essence of quadrature and collocation techniques is developed for the solution of the governing integral equation. Selected results for the interaction problem are presented to illustrate various basic features of the solution. In addition to furnishing the compliance functions commonly used in soil-structure interaction studies, the solution should prove useful in providing a basis for the assessment and improvement of approximate and numerical models currently employed for such analyses.
" }, { "name": "Huang, Moh-jiann", "degree": "PhD", "year": "1984", "title": "Investigation of Local Geology Effects on Strong Earthquake Ground Motions", "advisor": "Housner, George W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12122018-092221333", "creators": [ { "name": { "family": "Huang", "given": "Moh-jiann" }, "id": "Huang-Moh-jiann", "display_name": "Huang, Moh-jiann" } ], "advisors": [ { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "advisor", "display_name": "Housner, George W." } ], "committee": [ { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "chair", "display_name": "Housner, George W." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." }, { "name": { "family": "Knowles", "given": "James K." }, "id": "Knowles-J-K", "role": "member", "display_name": "Knowles, James K." }, { "name": { "family": "Knauss", "given": "Wolfgang Gustav" }, "id": "Knauss-W-G", "role": "member", "display_name": "Knauss, Wolfgang Gustav" }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "civileng" ], "doi": "10.7907/pm3k-w086", "abstract": "Accelerograms recorded at four stations in the Pasadena area during the 1971 San Fernando, the 1970 Lytle Creek, the 1968 Borrego Mountain and the 1952 Kern County earthquakes are analyzed to investigate local geology effects on strong earthquake ground motions. Spatial variations of the ground motions at two nearby stations are also investigated. It is found that the ground motions in this area caused by the local geology effects depend on the 3- dimensional configuration of the local geology and the direction of arriving seismic waves. Local geology effects are less evident on the leading portions of the accelerograms than the trailing portions, indicating the effects of local geology on surface wave propagations. Comparison of the Fourier amplitudes of the motions recorded at the same station during different earthquakes shows that there are no significant spectral peaks can be identified as site periods. Hence, it is not appropriate to characterize such local sites by a site period.
\r\n\r\nA two-dimensional model considering inclined propagating P and S waves in a horizontal-layered structure, which is more realistic and closer to the actual seismic environment within a local geology than the one-dimensional model of vertically propagating waves, is studied. The transfer functions between the free surface and the half-space outcrop for a single incident P, SV or SH wave from the half-space at an incident angle are defined and derived by a matrix method. Two numerical examples are given to demonstrate the effects of incident angle and material damping on the transfer function. It is found that the transfer function between the free surf ace motions and the bedrock outcrop motions to multiple incident waves having different amplitudes, angles and arrival times is quite different from that for a single incident wave. Completely satisfactory results cannot be expected when using the analytical model for evaluating the local geology effects on the motions during a nearby shallow-focus earthquake for which seismic waves emitted from different parts of the fault will approach the bedrock from different directions and at different angles.
\r\n\r\nThe analytical model for assessing local geology effects is evaluated in the light of the data recorded at stations in the Pasadena area during the 1971 San Fernando earthquake. The observed site transfer functions between the alluvial and the rock sites are obtained and compared with the computed results from a two-dimensional model with 7-layers overlying a half-space. Values of model parameters are optimally adjusted to give a best least-squares fit between computed and observed amplitude ratios. It is concluded that the analytical model oversimplifies the local geological structure in the Pasadena area and the actual seismic environment in the area during the 1971 San Fernando earthquake.
\r\n\r\nIt is concluded from these studies that the effects of the source mechanism and the seismic wave travel paths upon the site ground motion can be comparable to the effect of the local geology. The characteristics of the source mechanism, such as type of faulting, direction of fault-slip propagation, nature of stress drop across the fault surface, orientation of fault, depth beneath ground surface, etc., can appreciably influence the ground motion at the site. Also, the travel path can have a significant effect through influencing the types of waves that reach the site, and the directions of approach of the waves. The results of this study indicate that a better understanding of the spatial variation of ground motions, of the role played by different types of waves and their contributions to an accelerogram, and of the propagation directions of the waves is needed for assessing local geology effects on earthquake ground motions. A local array is desirable to provide data for giving a reasonably complete picture of the nature of ground motions in a local area.
" }, { "name": "Jain, Sudhir Kumar", "degree": "PhD", "year": "1983", "title": "Analytical Models for the Dynamics of Buildings", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08162019-113014700", "creators": [ { "name": { "family": "Jain", "given": "Sudhir Kumar" }, "id": "Jain-Sudhir-Kumar", "display_name": "Jain, Sudhir Kumar" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "chair", "display_name": "Jennings, Paul C." }, { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "member", "display_name": "Housner, George W." }, { "name": { "family": "Babcock", "given": "Charles D." }, "id": "Babcock-C-D", "role": "member", "display_name": "Babcock, Charles D." }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "civileng" ], "doi": "10.7907/4k04-ca84", "abstract": "This thesis investigates the significance of in-plane floor flexibility on the dynamics of buildings, and develops analytical models for structures that have flexible floor diaphragms. Experience with past earthquakes demonstrates that this feature is particularly important for long, narrow buildings and buildings with stiff end walls. In the method developed in this study, the equations of motion and appropriate boundary conditions for various elements of the structure are written in a single coordinate system and then are solved exactly.
\r\n\r\nOne- and two-story buildings with end walls are analyzed by treating their floors and walls as bending and shear beams, respectively. The resulting equations of motion and the boundary conditions are solved to obtain the dynamic properties of the structure. The expected low torsional stiffness of the end walls or frames is confirmed by analysis of a single-story example structure. Study of a similar two-story building showed that the first two modes, dominated by the floor and the roof vibrations, make the largest contributions to the total base shear in the structure.
\r\n\r\nFloors of multistory buildings with end walls (or frames) are idealized as equivalent, distributed beams while the walls or frames are treated as bending or shear beams. Analysis of a nine-story building showed that the structure possesses several lower modes in which floors vibrate essentially as pinned-pinned beams.
\r\n\r\nBuildings with large numbers of uniform stories and frames (or walls) are treated as vertically-oriented anisotropic plates. It is concluded that the floors in such buildings can be assumed rigid for seismic analysis, since the modes involving floor deformations are not excited by uniform ground motion.
\r\n\r\nThe approach can be generalized further to study more complex structures. An example is the Imperial County Services Building, which has two end walls in the upper stories and several walls in the ground story. The analytical model of this building predicts several important features of the complex dynamic behavior of the structure.
\r\n" }, { "name": "Lin, Albert Niu", "degree": "PhD", "year": "1982", "title": "Experimental Observations of the Effect of Foundation Embedment on Structural Response", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05162018-100416743", "creators": [ { "name": { "family": "Lin", "given": "Albert Niu" }, "id": "Lin-Albert-Niu", "display_name": "Lin, Albert Niu" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "chair", "display_name": "Housner, George W." }, { "name": { "family": "Babcock", "given": "Charles D." }, "id": "Babcock-C-D", "role": "member", "display_name": "Babcock, Charles D." }, { "name": { "family": "Brooks", "given": "Norman H." }, "id": "Brooks-N-H", "role": "member", "display_name": "Brooks, Norman H." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "civileng" ], "doi": "10.7907/ksr8-pf30", "abstract": "Ambient, ring-down, and forced vibration tests were used to determine the effect of foundation embedment on the response of a one-story model structure 10 ft square in plan and 11.4 ft high. The tests, conducted at the full-, half- and unembedded foundation conditions, led to the identification of the fundamental translatory mode in the primary (east-west) and secondary (north-south) directions, and two torsional modes. The forced vibration consisted of horizontally incident SH-waves generated at an excitation structure located 47.5 ft (center-to-center) away. During these tests, detailed measurements of the near-field ground motion and modal displacement ratios were obtained at the fundamental mode in the primary direction. The displacement ratios were used to calculate the structural and foundation-soil stiffnesses and damping coefficients for comparison to theoretical results. Foundation embedment increased the model frequencies and decreased the contribution of the foundation motion to the overall displacement of the superstructure. For the fundamental mode response, which consisted of translatory and rocking motions, the resonant frequency predicted by lumped parameter analysis was higher than that measured experimentally by 25% for the unembedded case. While the experimental and theoretical fundamental mode shapes were in close agreement, the calculated effect of embedment on the response was less than that measured. These results were consistent with the comparison of the impedances and embedment factors. Serious discrepancies between analytical and experimental results were found for the case of torsion; a simple two-degree-of-freedom model was consistent only with the first of the two measured resonant frequencies.
" }, { "name": "Cohen, Martin", "degree": "PhD", "year": "1981", "title": "Silent Boundary Methods for Transient Wave Analysis", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechThesis:08132021-221014507", "creators": [ { "name": { "family": "Cohen", "given": "Martin" }, "id": "Cohen-Martin", "display_name": "Cohen, Martin" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/xrgh-ag46", "abstract": "This thesis sets forth a dynamic model, designed to absorb infinitely radiating waves in a finite, computational grid. The analysis is primarily directed toward the problem of soil-structure interaction, where energy propagates from a region near a structure, outward toward the boundaries.
\r\n\r\nThe proposed method, called the extended-paraxial boundary, is derived from one-directional, wave theories that have been propounded by other authors. In this thesis, the theory is presented from a more general viewpoint and is studied for its stability properties. This work suggests some modifications to the method as it was first presented. Innovations are also put forward in the boundary's implementation for finite element calculations. These alterations render the boundary an effective wave absorber.
\r\n\r\nThe extended-paraxial boundary is then compared, both analytically and numerically, with two other transmitting (or silent) boundaries currently available -- the standard-viscous and unified-viscous methods. The analytical results indicate that the extended-paraxial boundary enjoys a distinct advantage in cancelling wave reflections; actual numerical tests revealed a small superiority over the viscous approaches.
\r\n\r\nVarious issues are also discussed as they relate to the silent boundaries. These include Rayleigh waves, spherically symmetric and axially symmetric waves, nonlinear waves, anisotropic media, and numerical stability.
" }, { "name": "Hall, Shawn Anthony", "degree": "PhD", "year": "1981", "title": "Vortex-Induced Vibrations of Structures", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02222018-150519570", "creators": [ { "name": { "family": "Hall", "given": "Shawn Anthony" }, "id": "Hall-Shawn-Anthony", "display_name": "Hall, Shawn Anthony" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "chair", "display_name": "Iwan, Wilfred D." }, { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "member", "display_name": "Housner, George W." }, { "name": { "family": "Hudson", "given": "Donald E." }, "id": "Hudson-D-E", "role": "member", "display_name": "Hudson, Donald E." }, { "name": { "family": "Sabersky", "given": "Rolf H." }, "id": "Sabersky-R-H", "role": "member", "display_name": "Sabersky, Rolf H." }, { "name": { "family": "Lorden", "given": "Gary A." }, "id": "Lorden-G-A", "role": "member", "display_name": "Lorden, Gary A." } ], "option_major": [ "mecheng" ], "doi": "10.7907/Y4QP-A998", "abstract": "Vortex-induced oscillations, often of concern when a bluff structure is exposed to fluid cross-flow, are considered herein using a semi-empirical modeling approach. Based on the fluid momentum theorem, the model involves a highly simplified abstraction of the complex flow field, and major assumptions concerning the nature of the coupling between the fluid and the oscillating structure.
\r\n\r\nThree prototype problems are studied, including harmonically forced cylinders, spring-mounted cylinders, and taut elastic cables; in each case the structure is assumed to be of circular cross-section and situated in a uniform cross-flow. Only oscillations transverse to the flow are considered. The problem of modal interaction for elastic cables, typically of interest when the fluid flow excites high-mode-number resonances, is given particular attention.
\r\n\r\nThe model produces a set of nonlinear, ordinary differential equations describing the coupled fluid/structure oscillations. Steady-state oscillatory solutions to these equations are found analytically and are examined for stability. Using various regression techniques, the steady-state solutions are then fit to experimental data for forced and spring-mounted cylinders. Finally, the model's predictions for elastic cables are used to postulate a qualitative picture of modal interaction, certain features of which have been observed experimentally.
" }, { "name": "Krousgrill, Charles Morton", "degree": "PhD", "year": "1981", "title": "A Linearization Technique for the Dynamic Response of Nonlinear Continua", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechThesis:08202021-231219519", "creators": [ { "name": { "family": "Krousgrill", "given": "Charles Morton" }, "id": "Krousgrill-Charles-Morton", "display_name": "Krousgrill, Charles Morton" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/d5wa-0v91", "abstract": "The efforts of this dissertation are directed toward the development of a technique for understanding the dynamic response of structural elements governed by nonlinear partial differential equations. This technique is based on the concepts of the equivalent linearization method which relies on obtaining an optimal linear set of equations to model the original nonlinear set.
\r\n\r\nIn this method, the linearization is performed at the continuum level. At this level, the equivalent linear stiffness and damping parameters are physically realizable and are defined in such a way that the method can be easily be incorporated into finite element computer codes.
\r\n\r\nThree different approaches to the method are taken with each approach based on the minimization of a distinct difference between the nonlinear system and its linear replacement, Existence and uniqueness properties of the minimizat4on solutions are established.
\r\n\r\nThe method is specialized for the treatment of steady-state solutions to harmonic excitation and of stationary response to random excitation. Procedures for solving the equivalent linearization are also discussed.
\r\n\r\nThe method is applied to three specific examples: one dimensional, hysteretic shear beams, thin plates governed by nonlinear equations of motion and the same nonlinear thin plates but with cutouts. Solutions via the equivalent linearization method using the stress difference minimization compare well with Galerkin's method and numerical integration. The last example is easily handled by the continuum equivalent linearization technique, whereas other methods prove to be inadequate.
" }, { "name": "Liu, Wing Kam", "degree": "PhD", "year": "1981", "title": "Development of Finite Element Procedures for Fluid-Structure Interaction", "advisor": "Hughes, Thomas J. R.", "url": "https://resolver.caltech.edu/CaltechThesis:08202021-235130206", "creators": [ { "name": { "family": "Liu", "given": "Wing Kam" }, "id": "Liu-Wing-Kam", "display_name": "Liu, Wing Kam" } ], "advisors": [ { "name": { "family": "Hughes", "given": "Thomas J. R." }, "id": "Hughes-T-J-R", "role": "advisor", "display_name": "Hughes, Thomas J. R." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/4yzv-q979", "abstract": "In this thesis the development of finite element procedures for fluid-structure interaction problems is presented. The areas upon which attention is focused are: numerical transient algorithms which emphasize implicit-explicit finite element concepts; finite element kinematical descriptions for modelling fluid subdomains in fluidstructure interaction problems; finite element methodology for nearly incompressible fluids and solids, and beam, plate and shell structures based upon theories which include transverse shear deformations; and finite rotation effects in numerical integration of rate constitutive equations arising in large-deformation analysis. All these nonlinear methodologies have been integrated into a working finite element computer code. A number of numerical examples are presented to demonstrate the effectiveness of these approaches." }, { "name": "Haroun, Medhat Ahmed", "degree": "PhD", "year": "1980", "title": "Dynamic Analyses of Liquid Storage Tanks", "advisor": "Housner, George W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08292019-100431566", "creators": [ { "name": { "family": "Haroun", "given": "Medhat Ahmed" }, "id": "Haroun-Medhat-Ahmed", "display_name": "Haroun, Medhat Ahmed" } ], "advisors": [ { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "advisor", "display_name": "Housner, George W." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/1J74-RH65", "abstract": "Theoretical and experimental investigations of the dynamic behavior of cylindrical liquid storage tanks are conducted to seek possible improvements in the design of such tanks to resist earthquakes. The study is carried out in three phases: 1) a detailed theoretical treatment of the liquid-shell system, 2) an experimental investigation of the dynamic characteristics of full-scale tanks, and 3) a development of an improved design-procedure based on an approximate analysis.
\r\n\r\nNatural frequencies of vibration and the associated mode shapes are found through the use of a discretization scheme in which the elastic shell is modeled by finite elements and the fluid region is treated as a continuum by boundary solution techniques. In this approach, the number of unknowns is substantially less than in those analyses where both tank wall and fluid are subdivided into finite elements. A method is presented to compute the earthquake response of both perfect circular and irregular tanks; it is based on superposition of the free lateral vibrational modes. Detailed numerical examples are presented to illustrate the applicability and effectiveness of the analysis and to investigate the dynamic characteristics of tanks with widely different properties. Ambient and forced vibration tests are conducted on three full-scale water storage tanks to determine their dynamic characteristics. Comparison with previously computed mode shapes and frequencies shows good agreement with the experimental results, thus confirming the reliability of the theoretical analysis. Approximate solutions are also developed to provide practicing engineers with simple, fast, and sufficiently accurate tools for estimating the seismic response of storage tanks.
" }, { "name": "McVerry, Graeme Haynes", "degree": "PhD", "year": "1980", "title": "Frequency Domain Identification of Structural Models from Earthquake Record", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechThesis:08232021-222545352", "creators": [ { "name": { "family": "McVerry", "given": "Graeme Haynes" }, "id": "McVerry-Graeme-Haynes", "display_name": "McVerry, Graeme Haynes" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/bpab-qq32", "abstract": "The usefulness of simple linear mathematical models for representing the behaviour of tall buildings during earthquake response is investigated for a variety of structures over a range of motions including the onset of structural damage. The linear models which best reproduce the measured response of the structures are determined from the recorded earthquake motions. In order to improve upon unsatisfactory results obtained by methods using transfer functions, a systematic frequency domain identification technique is developed to determine the optimal models. The periods, dampings and participation factors are estimated for the structural modes which are dominant in the measured response.
\r\n\r\nThe identification is performed by finding the values of the modal parameters which produce a least-squares match over a specified frequency range between the unsmoothed, complex-valued, finite Fourier transform of the acceleration response recorded in the structure and that calculated for the model. It is possible to identify a single linear model appropriate for the entire response, or to approximate the nonlinear behavior exhibited by some structures with a series of models optimal for different segments of the response.
\r\n\r\nThe investigation considered the earthquake records obtained in ten structures ranging in height from seven to forty-two stories. Most of the records were from the San Fernando earthquake. For two of these structures, smaller-amplitude records from more distant earthquakes were also analyzed. The maximum response amplitudes ranged from approximately 0.025 g to 0.40 g.
\r\n\r\nThe very small amplitude responses were reproduced well by linear models with fundamental periods similar to those measured in vibration tests. Most of the San Fernando responses in which no structural damage occurred (typically 0.2g-0.3g maximum accelerations) were also matched closely by linear models. However, the effective fundamental periods in these responses were characteristically 50 percent longer than in vibration tests. The average first mode damping identified from these records was about 5 percent of critical. Only those motions which produced structural damage could not be represented satisfactorily by time-invariant linear models. Segment-by-segment analysis of these records revealed effective periods of two to three times the vibration test values with fundamental mode dampings of 15 to 20 percent.
\r\n\r\nThe systematic identification technique generally achieves better matches of the recorded responses than those produced by models derived by trial-and-error methods, and consequently more reliable estimates of the modal parameters. The close reproductions of the measured motions confirm the accuracy of linear models with only a few modes for representing the behaviour during earthquake response of tall buildings in which no structural damage occurs.
" }, { "name": "Beck, James Leslie", "degree": "PhD", "year": "1979", "title": "Determining Models of Structures from Earthquake Records", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11212003-110242", "creators": [ { "name": { "family": "Beck", "given": "James Leslie" }, "id": "Beck-James-Leslie", "display_name": "Beck, James Leslie" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "chair", "display_name": "Jennings, Paul C." }, { "name": { "family": "Babcock", "given": "Charles D." }, "id": "Babcock-C-D", "role": "member", "display_name": "Babcock, Charles D." }, { "name": { "family": "Hudson", "given": "Donald E." }, "id": "Hudson-D-E", "role": "member", "display_name": "Hudson, Donald E." }, { "name": { "family": "Wu", "given": "Theodore Yao-tsu" }, "id": "Wu-T-Y-T", "role": "member", "display_name": "Wu, Theodore Yao-tsu" }, { "name": { "family": "Caughey", "given": "Thomas Kirk" }, "id": "Caughey-T-K", "role": "member", "display_name": "Caughey, Thomas Kirk" } ], "option_major": [ "civileng" ], "doi": "10.7907/JP7R-KF57", "abstract": "The problem of determining linear models of structures from seismic response data is studied using ideas from the theory of system identification. The investigation employs a general formulation called the output-error approach, in which optimal estimates of the model parameters are obtained by minimizing a selected measure-of-fit between the responses of the structure and the model. The question of whether the parameters can be determined uniquely and reliably in this way is studied for a general class of linear structural models. Because earthquake records are normally available from only a small number of locations in a structure, and because of measurement noise, it is shown that it is necessary in practice to estimate parameters of the dominant modes in the records, rather than the stiffness and damping matrices.
\r\n\r\nTwo output-error techniques are investigated. Tests of the first, an optimal filter method, show that its advantages are offset by weaknesses which make it unsatisfactory for application to seismic response. A new technique, called the modal minimization method, is developed to overcome these difficulties. It is a reliable and efficient method to determine the optimal estimates of modal parameters for linear structural models.
\r\n\r\nThe modal minimization method is applied to two multi-story buildings that experienced the 1971 San Fernando earthquake. New information is obtained concerning the properties of the higher modes of the taller building and more reliable estimates of the properties of the fundamental modes of both structures are found. The time-varying character of the equivalent linear parameters is also studied for both buildings. It is shown for the two buildings examined that the optimal, time-invariant, linear models with a small number of modes can reproduce the strong-motion records much better than had been supposed from previous work using less systematic techniques.
" }, { "name": "Mason, Alfred Barr", "degree": "PhD", "year": "1979", "title": "Some Observations on the Random Response of Linear and Nonlinear Dynamical Systems", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechThesis:08232021-215722701", "creators": [ { "name": { "family": "Mason", "given": "Alfred Barr" }, "id": "Mason-Alfred-Barr", "display_name": "Mason, Alfred Barr" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "mecheng" ], "doi": "10.7907/hvp8-jf64", "abstract": "First examined is the problem of obtaining the nonstationary stochastic response of a nonlinear system subject to deterministically modulated stationary Gaussian random excitation. An extension of the generalized method of equivalent linearization is used to obtain an approximation to this response. The accuracy of this approximate technique is investigated by means of Monte Carlo simulation.
\r\n\r\nAttention is then turned to the first passage problem for the stationary response of a lightly damped linear oscillator excited by white noise. A method is developed to generate approximate values for the limiting decay rate of the corresponding first passage probability density. This method is extended so that an approximate first passage probability distribution may be calculated when the oscillator response is nonstationary. The accuracy of this approximate distribution is examined.
\r\n\r\nAs a practical application, it is indicated how this technique may be used to determine an earthquake-like random process which generates a response spectrum consistent with given data. The accuracy and range of validity of the procedure are indicated by a simulation study.
\r\n\r\nThe approximate solution of the first passage problem is combined with the equivalent linearization technique to yield a procedure for computing approximate first passage probabilities of a weakly nonlinear oscillator. The errors introduced by this procedure are investigated.
" }, { "name": "Foutch, Douglas Allen", "degree": "PhD", "year": "1977", "title": "A Study of the Vibrational Characteristics of Two Multistory Buildings", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03312017-102214623", "creators": [ { "name": { "family": "Foutch", "given": "Douglas Allen" }, "id": "Foutch-Douglas-Allen", "display_name": "Foutch, Douglas Allen" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/X944-SG43", "abstract": "Forced vibration tests and associated analysis of two multistory\r\nbuildings are described. In one case, the dynamic properties of the\r\nbuilding measured during the tests are compared to those predicted by\r\nsimple analytical models. A three-dimensional finite element model\r\nof the second building was constructed for the purpose of evaluating\r\nthe accuracy of this type of analysis for predicting the observed\r\ndynamic properties of the structure.
\r\n\r\n\r\nForced vibration tests were performed on Millikan Library, a\r\nnine-story reinforced concrete shear wall building. Measurements of\r\nthree-dimensional motions of approximately 50 points on each of six\r\nfloors (including the basement) were taken for excitation in the N-S and\r\nE-W directions. The results revealed a complex interaction between\r\nlateral and vertical load carrying systems in both directions. The\r\nresults also suggest that a significant change in the foundation response\r\nof the structure occurred in the stiffer N-S direction during the San\r\nFernando earthquake. This phenomenon was investigated through the\r\nuse of two analytical models of the building which included the effects\r\nof soil-structure interaction.
\r\n\r\n\r\nThe Ralph M. Parsons world Headquarters building, a twelve-story\r\nsteel frame structure, was also tested. The natural frequencies,\r\nthree-dimensional mode shapes, and damping coefficients of nine modes\r\nof vibration were determined. Other features of this investigation\r\nincluded the study of nonlinearities associated with increasing levels\r\nof response and the measurement of strain in one of the columns of the\r\nstructure during forced excitation. The dynamic characteristics of\r\nthe building determined by these tests are compared to those predicted\r\nby a finite element model of the structure. The properties of primarily\r\ntranslational modes are predicted reasonably well; but adequate predictions\r\nof torsional motions were not obtained. The comparison\r\nbetween measured and predicted strains suggests that estimates of\r\nstress obtained from finite element analyses of buildings should be\r\nwithin 25 percent of those experienced by the structure for a known\r\nexcitation.
" }, { "name": "Gates, Nathan Craig", "degree": "PhD", "year": "1977", "title": "The Earthquake Response of Deteriorating Systems", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04212017-094508970", "creators": [ { "name": { "family": "Gates", "given": "Nathan Craig" }, "id": "Gates-Nathan-Craig", "display_name": "Gates, Nathan Craig" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/E3AQ-B348", "abstract": "This thesis is concerned with the earthquake response of\r\ndeteriorating systems. A model for stiffness degrading or\r\ndeteriorating systems is used to describe six different single-degree-of-freedom systems. A numerical investigation of the\r\nresponse of these six systems is performed using an ensemble of\r\ntwelve earthquakes. The response is studied at nine nominal\r\nperiods of oscillation. The numerical results are presented as\r\nresponse spectra corresponding to six different ductilities.
\r\n\r\nAn approximate analytical method for calculating the earthquake\r\nresponse of deteriorating systems from a linear response\r\nspectrum is presented. The method, called the average stiffness\r\nand energy method, is based upon the premise that a linear system\r\nmay be defined which is in some sense equivalent to the deteriorating\r\nsystem. The criterion for equivalence in this method is that\r\nthe average stiffness of the deteriorating system be equal to the\r\nstiffness of the linear system and the average energy dissipated\r\nby the linear system be the same as the average energy dissipated\r\nby the deteriorating system.
\r\n\r\nThe new analytical method is compared to existing methods.\r\nComparison with the numerical results is also made. Based upon\r\nthese comparisons, it is concluded that the average stiffness and\r\nenergy method represents a significant improvement over currently\r\navailable methods for predicting the earthquake response of\r\ndeteriorating and nondeteriorating systems.
" }, { "name": "Spanos, Polihronis Thomas Dimitrios", "degree": "PhD", "year": "1977", "title": "Linearization Techniques for Non-Linear Dynamical Systems", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10282024-225753505", "creators": [ { "name": { "family": "Spanos", "given": "Polihronis Thomas Dimitrios" }, "id": "Spanos-Polihronis-Thomas-Dimitrios", "display_name": "Spanos, Polihronis Thomas Dimitrios" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/bxg5-0375", "abstract": "This dissertation is concerned with the application of linearization techniques to the study of the response of non-linear dynamical systems subjected to periodic and random excitations.
\r\n\r\nA general method for generating an approximate solution of a multi-degree-of-freedom non-linear dynamical system is presented. This method relies on solving an optimum equivalent linear sub\u00adstitute of the original system.
\r\n\r\nThe applicability of the method for determination of the amplitudes and phases of the approximate steady-state solution of a multi-degree-of-freedom non-linear system under harmonic monofrequency excitation is considered. The implementation of the method for several special classes of non-linear functions is dis\u00adcussed in detail. In addition, the manner in which the method may be applied to generate an approximate solution for the covariance matrix of the stationary random response of a multi-degree-of\u00ad freedom dynamical system subjected to stationary Gaussian exci\u00adtation is outlined.
\r\n\r\nThe potential of the method to treat transient solutions of non-linear systems is indicated in the context of the non-stationary response of a lightly damped and weakly non-linear oscillator sub\u00adjected to monofrequency harmonic or to a Gaussian white noise disturbance. For both classes of excitation the method produces a first-order differential equation governing the response amplitude. The results pertinent to the harmonically excited oscillator are compared with existing solutions. A non-stationary solution of the Fokker-Planck equation associated with the stochastic differential equation governing the response amplitude of the randomly excited oscillator is accomplished by perturbation techniques; the stationary solution is determined without making any approximation in the Fokker-Planck equation.
\r\n\r\nThe new method for transient response is applied to the random response of a Duffing Oscillator and a Hysteretic System. The solution for the Duffing Oscillator is compared with data obtained by a Monte Carlo study.
" }, { "name": "Jensen, Arthur R.", "degree": "PhD", "year": "1976", "title": "Computer Simulation of Surface Water Hydrology and Salinity with an Application to Studies of Colorado River Management", "advisor": "List, E. John; Morgan, James J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01152026-221251934", "creators": [ { "name": { "family": "Jensen", "given": "Arthur R." }, "id": "Jensen-Arthur-R", "display_name": "Jensen, Arthur R." } ], "advisors": [ { "name": { "family": "List", "given": "E. John" }, "id": "List-E-J", "role": "advisor", "display_name": "List, E. John" }, { "name": { "family": "Morgan", "given": "James J." }, "id": "Morgan-J-J", "role": "co-advisor", "display_name": "Morgan, James J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "envreng" ], "doi": "10.7907/jmm5-0x29", "abstract": "Management of a large river basin requires information regarding the\r\ninteractions of variables describing the system. A method has been\r\ndeveloped to determine these interactions so that the resources management\r\nwithin a given river basin can proceed in an optimal way. The\r\nmethod can be used as a planning tool to display how different management\r\nalternatives affect the behavior of the river system. Direct\r\napplication is made to the Colorado River Basin.
\r\n\r\nThe Colorado River has a relatively low and highly variable streamflow.\r\nAllocated rights to the consumptive use of the river water exceed\r\nthe present long-term average flow. The naturally high total dissolved\r\nsolids concentration of the river water continues to increase due to the\r\nactivities of man. Current management policies in the basin have been\r\nthe products of compromises between the seven states and two countries\r\nwhich are traversed by the river or its tributaries. The anticipated\r\nuse of the scarce supply of water in the extraction and processing of\r\nenergy resources in the basin underwrites the need for planning tools\r\nwhich can illuminate many possible management alternatives and their\r\neffects upon water supply, water quality, power production, and the\r\nother concerns of the Colorado River water users.
\r\n\r\nA computer simulation model has been developed and used to simulate\r\nthe effects of various management alternatives upon water conservation,\r\nwater quality, and power production. The model generates synthetic\r\nsequences of streamflows and total dissolved solids (TDS) concentrations.\r\nThe flows of water and TDS are then routed through the major reservoirs\r\nof the system, Lakes Powell and Mead.
\r\n\r\nCharacteristics of system behavior are examined from simulations\r\nusing different streamflow sequences, upstream depletion levels, and\r\nreservoir operating policies. Reservoir evaporation, discharge, discharge\r\nsalinity, and power generating capacity are examined.
\r\n\r\nSimulation outputs show that the probability with which Lake Powell\r\nfails to supply a specified target discharge is highly variable. Simulations\r\nemploying different streamflow sequences result in probabilities\r\nof reservoir failure which differ by as much as 0.1.
\r\n\r\nThree levels of Upper Colorado River Basin demands are imposed on\r\nthe model: 3.8 MAF/yr (4.7 km3 /yr), 4.6 MAF/yr (5.7 km3/yr), and 5.5\r\nMAF/yr (6.8 km3/yr). Two levels of water demand are imposed below\r\nLake Mead: 8.25 MAF/yr (10.2 km3/yr) and 7.0 MAF/yr (6.8 km3/yr).
\r\n\r\nAlthough the effects of reservoir operations upon water quality\r\nare made uncertain by a lack of knowledge regarding the chemical\r\nlimnology of Lake Powell, two possible lake chemistry models have been\r\ndeveloped, and the predicted impacts of changes in reservoir operation\r\nupon water quality are presented.
\r\n\r\nThe current criteria for the operations of Lakes Powell and Mead\r\nare based upon 75 years of compromises and agreements between the various\r\nwater interests in the Colorado River Basin. Simulations show that\r\nLake Powell will be unable to conform to these operating constraints\r\nat the higher levels of water demand.
\r\n\r\nAn alternative form of reservoir operation is defined and compared\r\nto the existing policy on the basis of reliability of water supply, conservation\r\nof water, impact upon water quality, and the effect upon power\r\ngeneration.
\r\n\r\nIgnoring the current institutional operating constraints, and\r\nattempting only to provide a reliable supply of water at the locations\r\nof water demand, is shown to be a superior management policy. This\r\nalternate policy results in the conservation of as much as 0.25 MAF/yr\r\n(0.3 km3/yr) of water. The impact of the alternate operating policy\r\nupon hydroelectric power generation and the potential use of the conserved\r\nwater for development of energy resources is discussed.
" }, { "name": "Miller, Richard Keith", "degree": "PhD", "year": "1976", "title": "The Steady-State Response of Multidegree-of-Freedom Systems with a Spatially Localized Nonlinearity", "advisor": "Iwan, Wilfred D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03052014-104111406", "creators": [ { "name": { "family": "Miller", "given": "Richard Keith" }, "id": "Miller-Richard-Keith", "display_name": "Miller, Richard Keith" } ], "advisors": [ { "name": { "family": "Iwan", "given": "Wilfred D." }, "id": "Iwan-W-D", "role": "advisor", "display_name": "Iwan, Wilfred D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/M5NW-Z443", "abstract": "This thesis is concerned with the dynamic response of a\r\nGeneral multidegree-of-freedom linear system with a one dimensional nonlinear constraint attached between two points. The nonlinear constraint is assumed to consist of rate-independent conservative and hysteretic nonlinearities and may contain a viscous dissipation element. The dynamic equations for general spatial and temporal load distributions are derived for both continuous and\r\ndiscrete systems. The method of equivalent linearization is used to develop equations which govern the approximate steady-state response to generally distributed loads with harmonic time dependence.
\r\n\r\nThe qualitative response behavior of a class of undamped\r\nchainlike structures with a nonlinear terminal constraint is\r\ninvestigated. It is shown that the hardening or softening behavior of every resonance curve is similar and is determined by the properties of the constraint. Also examined are the number and location of resonance curves, the boundedness of the forced response, the loci of response extrema, and other characteristics\r\nof the response. Particular consideration is given to the\r\ndependence of the response characteristics on the properties of the linear system, the nonlinear constraint, and the load distribution.
\r\n\r\nNumerical examples of the approximate steady-state response of three structural systems are presented. These examples illustrate the application of the formulation and qualitative theory. It is shown that disconnected response curves and response curves which cross are obtained for base excitation of a uniform shear beam with a cubic spring foundation. Disconnected response curves are also obtained for the steady-state response to a concentrated\r\nload of a chainlike structure with a hardening hysteretic constraint. The accuracy of the approximate response curves is investigated.
\r\n" }, { "name": "Crouse, Charles Brian", "degree": "PhD", "year": "1974", "title": "Engineering Studies of the San Fernando Earthquake", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechThesis:08112021-192505383", "creators": [ { "name": { "family": "Crouse", "given": "Charles Brian" }, "id": "Crouse-Charles-Brian", "display_name": "Crouse, Charles Brian" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/17yn-bc14", "abstract": "A number of accelerograms obtained during the San Fernando earthquake were analyzed to investigate the nature of the strong motion. The particular features studied were soil-structure interaction and the relative influence of local site conditions versus the source mechanism and travel paths of earthquake waves.
\r\n\r\nEvidence of soil-structure interaction in the EW fundamental mode of the Hollywood Storage building is seen in the earthquake data. General agreement exists up to ~ 5 c.p.s. in both lateral directions between theoretical, base to free field transfer functions and transfer functions derived from accelerograms obtained in the basement and adjacent parking lot. There was no evidence of soil-structure interaction in the Millikan Library and Athenaeum buildings on the Caltech campus, and this effect could not account for the major differences in their accelerograms.
\r\n\r\nAccelerogram, Fourier Amplitude Spectra, and Response Spectra data were compared from a group of six tall buildings close together near Wilshire Blvd. and Normandie Ave. in Los Angeles and from seven surrounding buildings, two to three miles away. The data indicated that local site conditions and soil-structure interaction were not major contributors to the observed differences in the response at these sites. There was correlation between the degree of similarity in the response at two sites and their distance apart. A simple wave superposition model with numerical examples confirms this correlation.
" }, { "name": "Wood, John Holm", "degree": "PhD", "year": "1973", "title": "Earthquake-Induced Soil Pressures on Structures", "advisor": "Housner, George W.", "url": "https://resolver.caltech.edu/CaltechThesis:10152019-101037996", "creators": [ { "name": { "family": "Wood", "given": "John Holm" }, "id": "Wood-John-Holm", "display_name": "Wood, John Holm" } ], "advisors": [ { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "advisor", "display_name": "Housner, George W." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/MZWQ-BA46", "abstract": "The earthquake-induced pressures on soil-retaining structures are investigated. The study was motivated by the lack of suitable earthquake design data for relatively rigid structures on firm foundations in situations where the foundation, structure and retained soil remain essentially elastic.
\r\n\r\nPressures and forces on the walls of a number of idealized wall-soil problems are analyzed. The solutions obtained are evaluated for a range of the important parameters to give results useful for design. In the idealized problems the soil is represented by an elastic layer of finite length bonded to a rigid foundation or rock layer. The wall or structure is represented by a rigid element resting on the rock layer and is permitted to undergo rotational deformation about the base. The mass or moment of inertia of the structure and its rotational stiffness are included as parameters in the idealization. Static and dynamic solutions are obtained using both analytical and finite element methods. Solutions are evaluated for the assumption of perfectly rigid behavior of the wall. The general solution for the deformable wall case was developed by superposition of the solution for the perfectly rigid case and solutions derived for displacement forcing of the wall structure.
\r\n\r\nThe assumption of linear elastic behavior of the wall- soil system is likely to be approximately satisfied in situations where a building or other large civil engineering structure is founded on firm soil or rock strata. In contrast to the linearly elastic assumption made in this study, the commonly used Mononobe-Okabe method employs the assumption of sufficiently large wall deformations to induce a fully plastic stress condition in the soil. It was concluded that both the elastic theory and the Mononobe-Okabe method have valid applications in the design of wall structures subjected to earthquake motions, but that because of significant differences in the solutions obtained from each method, care is required in selecting the most appropriate method for a particular situation.
" }, { "name": "Udwadia, Firdaus Erach", "degree": "PhD", "year": "1972", "title": "Investigation of Earthquake and Microtremor Ground Motions", "advisor": "Hudson, Donald E.", "url": "https://resolver.caltech.edu/CaltechThesis:08262021-203716987", "creators": [ { "name": { "family": "Udwadia", "given": "Firdaus Erach" }, "id": "Udwadia-Firdaus-Erach", "display_name": "Udwadia, Firdaus Erach" } ], "advisors": [ { "name": { "family": "Hudson", "given": "Donald E." }, "id": "Hudson-D-E", "role": "advisor", "display_name": "Hudson, Donald E." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/4cv1-wy73", "abstract": "The nature of strong earthquake ground shaking has been investigated based on a study of 15 accelerograms recorded at El Centro in southern California. It is concluded that the characteristics of the source mechanism and the transmission path play a dominant role in determining the details of strong ground shaking at the site. No local site periodicities could be clearly identified, which suggests that source and transmission path effects overshadow the influence of local site conditions.
\r\n\r\nThe method of using microtremor measurements to determine local site characteristics has been tested by direct comparison with strong motion measurements. Microtremor ground motions were recorded at five sites in the El Centro area and measurements were repeated at three of these sites after a period of 24 hours. These low amplitude ground motions have been found to be widely different from the motions caused by strong earthquake ground shaking. Their nonstationary nature over a period of a day or so makes the interpretation of such data from a single microtremor measurement very unreliable. It has been concluded that these microtremor ground motions are forced oscillations of the ground caused by nearby sources of excitation. The microtremor acceleration spectra do not indicate prominent peaks that could be correlated with local site conditions. At this site the use of microtremor measurements to define local subsoil conditions would evidently not be feasible.
" }, { "name": "Adu, Randolph Ademola", "degree": "PhD", "year": "1971", "title": "Response and Failure of Structures Under Stationary Random Excitation", "advisor": "Housner, George W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11302017-155936522", "creators": [ { "name": { "family": "Adu", "given": "Randolph Ademola" }, "id": "Adu-Randolph-Ademola", "display_name": "Adu, Randolph Ademola" } ], "advisors": [ { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "advisor", "display_name": "Housner, George W." } ], "committee": [ { "name": { "family": "Housner", "given": "George W." }, "id": "Housner-G-W", "role": "chair", "display_name": "Housner, George W." }, { "name": { "family": "De Prima", "given": "Charles R." }, "id": "De-Prima-C-R", "role": "member", "display_name": "De Prima, Charles R." }, { "name": { "family": "Hudson", "given": "Donald E." }, "id": "Hudson-D-E", "role": "member", "display_name": "Hudson, Donald E." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Vreeland", "given": "Thad" }, "id": "Vreeland-T", "role": "member", "display_name": "Vreeland, Thad" } ], "option_major": [ "civileng" ], "doi": "10.7907/6304-3X27", "abstract": "The response of simple structural systems to stationary random excitation is considered under two criteria of failure. When failure is specified as the crossing of a maximum tolerable threshold by the response, the reliability of a structure is commonly measured by means of response spectra. These give the expected maximum value of the response parameter for a given excitation level. The statistical variations in these spectra are obtained here for viscously damped linear and elastoplastic single-degree of freedom systems by electronic analog simulation. The results obtained are compared with approximate statistical analyses; for example, the threshold crossing statistics of narrow-band oscillators. It is concluded that such methods give satisfactory, but conservative, estimates of the mean spectral values. It is significant that all the spectra obtained showed a very wide distribution about the mean. This was also true of the Fourier amplitude spectrum of the excita\u00adtion.
\r\n\r\nFor response that are so large that structures actually collapse, the linear model was replaced by an elastoplastic system, and the effect of gravity on the collapse time was considered. Experimental simulation showed that the structural response in this case is essentially that of a linear oscillator with yielding occurring at intermittent intervals. Gravity acts to increasingly bias this yielding in one direction, eventually causing instability in the system. Collapse of the system was sensitive to the distribution of peaks in the excitation and it was found that the wide dispersion in the collapse time can be reasonably represented by a Gamma distribution function.
\r\n\r\nAn analytic method for estimating the mean collapse time was derived by considering the energy distribution of the excitation and its effect on the yielding of the structure. The response process was thus modelled by that of an equivalent linear oscillator whose baseline is biased by the yielding in the structure. It was concluded that this procedure gives a good estimate of the failure time for excitations strong enough to cause failure in less than 20 seconds.
\r\n\r\nA two-degree of freedom elastoplastic hysteretic system with gravity was also simulated. In a certain sense, the qualitative behavior is similar to that of the single-degree of freedom system. It was thus possible to estimate the failure time of the structure from that of a single-degree of freedom system once the transmission of vibration is accounted for by considering a linear two-degree of freedom system.
" }, { "name": "Bielak, Jacobo", "degree": "PhD", "year": "1971", "title": "Earthquake Response of Building-Foundation Systems", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12062017-133056313", "creators": [ { "name": { "family": "Bielak", "given": "Jacobo" }, "id": "Bielak-Jacobo", "display_name": "Bielak, Jacobo" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/YEAJ-FN27", "abstract": "The influence of a deformable foundation on the response of \r\nbuildings to earthquake motion is examined. The study is divided into \r\ntwo parts; the vibration of the base of the building on the foundation \r\nmedium, and the response of the whole building-foundation system.
\r\n\r\nStudied first are the forced horizontal, rocking and vertical \r\nharmonic oscillations of a rigid dis c bonded to an elastic half-space, which \r\nis considered as a mathematical model for the soil. The problem,\r\nformulated in terms of dual integral equations, is reduced to a system \r\nof Fredholm integral equations of the second kind. For the limiting \r\nstatic case these equations yield a closed form solution in agreement\r\nwith that obtained by others.
\r\n\r\nUsing the force-deflection relations for the base, the equations of \r\nmotion of linear building-foundation systems are solved by both direct \r\nand transform methods.\tIt is shown that, under assumptions which \r\nappear to be physically reasonable, the earthquake response of the interaction \r\nsystem reduces to the linear superposition of the responses of \r\ndamped, linear one-degree-of-freedom oscillators subjected to modified \r\nexcitations. This result is valid even for systems that do not possess \r\nclassical normal modes. Explicit approximations in terms of the parameters \r\nof the system are obtained for the dynamic properties of\r\nthe one-degree-of-freedom oscillator which is equivalent to a single \u00adstory \r\nbuilding-foundation system. For multi-story buildings it is shown that the \r\neffect of an elastic foundation, as measured by the change in\r\nthe natural frequencies of the building, is negligible for modes \r\nhigher than the first for many types of building structures.
\r\n\r\n" }, { "name": "Hoerner, John Brent", "degree": "PhD", "year": "1971", "title": "Modal Coupling and Earthquake Response of Tall Buildings", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechThesis:10192017-153501109", "creators": [ { "name": { "family": "Hoerner", "given": "John Brent" }, "id": "Hoerner-John-Brent", "display_name": "Hoerner, John Brent" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "civileng" ], "doi": "10.7907/0H45-NM32", "abstract": "The major dynamic features of tall buildings are within the scope of a shear beam model. Herein the usual one-dimensional model is extended to three dimensions to include modes with translational and rotational components. The analysis is restricted to the continuous model with linear response.
\r\n\r\nA class of models for tall buildings is presented which possesses three sets of mutually orthogonal coupled modes. The amount of modal coupling is related to the eccentricities divided by the translational-torsional frequency differences. Strong modal coupling can occur if the eccentricities and frequency differences are small, as in a rectangular building with a smooth distribution of columns. A perturbation scheme is developed for buildings almost in this class. The perturbation method is applicable to buildings with nearly vertical mass and rigidity centers and with ith-modes of nearly the same shape.
\r\n\r\nRotational components of earthquake response in buildings primarily results from modal coupling, and it is shown that modal coupling can increase response on the building's perimeter. Furthermore, rectangular buildings with modal coupling can show a beating-type frequency response, for which the more usual r.m.s. combination should be replaced by an absolute sum. These effects can significantly increase certain response parameters. The corners of a rectangular building can have a 95% increase in shear, as compared with 30% implied by a 5% eccentricity in the codes. Base shears and overturning moments can be increased by 40%.
\r\n" }, { "name": "Skattum, Knut Sverre", "degree": "PhD", "year": "1971", "title": "Dynamic Analysis of Coupled Shear Walls and Sandwich Beams", "advisor": "Jennings, Paul C.", "url": "https://resolver.caltech.edu/CaltechThesis:10192017-151943526", "creators": [ { "name": { "family": "Skattum", "given": "Knut Sverre" }, "id": "Skattum-Knut-Sverre", "display_name": "Skattum, Knut Sverre" } ], "advisors": [ { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "advisor", "display_name": "Jennings, Paul C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedmech" ], "doi": "10.7907/SMJ0-W112", "abstract": "A study is made of the free vibration of planar coupled shear walls, a common lateral load-resisting configuration in building construction where two walls are coupled together by a system of discrete spandrel beams. The differential equations and boundary conditions are obtained by the variational method, and by assuming that the spandrels can be replaced by a continuous system of laminae, or small beams.
\r\n\r\nNatural frequencies and mode shapes are determined, and the results are presented in a number of figures from which the natural frequencies of any coupled shear wall can be extracted. The importance of including vertical displacement in the analysis is discussed, and a study of the effect of neglecting the vertical inertia term is given. These cases are illustrated with graphs and with one specific example. Investigations are also made of the asymptotic behavior of the system as the spandrels become weak, as they become stiff, and as the frequencies become large.
\r\n\r\nFinally, the theory of sandwich beams is presented and compared to that for coupled shear walls. It is observed that for most cases of constant properties, the differential equations (and boundary conditions) reduce to the same mathematical form for both theories.
" } ]