Monograph records
https://feeds.library.caltech.edu/people/Hall-J-F/monograph.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenMon, 15 Apr 2024 23:38:25 +0000Defensive design of concrete gravity dams
https://resolver.caltech.edu/CaltechEERL:1991.EERL-91-02
Authors: {'items': [{'id': 'Hall-J-F', 'name': {'family': 'Hall', 'given': 'John F.'}, 'orcid': '0000-0002-7863-5060'}, {'id': 'Dowling-M-J', 'name': {'family': 'Dowling', 'given': 'Michael J.'}}, {'id': 'El-Aidi-Bahaa', 'name': {'family': 'El-Aidi', 'given': 'Bahaa'}}]}
Year: 1991
Failure of a concrete gravity dam during an earthquake could occur as a sliding instability along an earthquake-induced crack, possibly assisted by uplift pressures from water flowing into the crack. Reliable assessment of the likelihood of such an event is thought to be difficult, and this suggests a need for designs which are less prone to cracking and uncertain behavior than are typical existing designs. Several schemes for reducing the potential for cracking during earthquake loading are investigated by finite element simulations: use of a sliding plane at the base of the dam, modification of the cross-sectional shape, use of a joint in the upper part of the clam, prestressing, and hydrodynamic isolation. The sliding plane, modified cross-section, and upper joint may only be applicable to new construction, while prestressing and hydrodynamic isolation could also be used to upgrade existing dams. While all of the schemes show potential, modification of the cross-sectional shape is probably the most practical considering acceptability, cost and effectiveness.https://authors.library.caltech.edu/records/cvt8x-67s08Parameter study of the response of moment-resisting steel frame buildings to near-source ground motions
https://resolver.caltech.edu/CaltechEERL:1995.EERL-95-08
Authors: {'items': [{'id': 'Hall-J-F', 'name': {'family': 'Hall', 'given': 'John F.'}, 'orcid': '0000-0002-7863-5060'}]}
Year: 1995
A parameter study is performed to investigate the effects of strong near-source ground motions from moderate-size earthquakes (Mw=7) on moment-resisting steel frame buildings. Two buildings, one 6 stories and the other 20 stories, are subjected to the Olive View Hospital free-field record from the Northridge earthquake and other ground motions from three earthquake simulations (Northridge earthquake, a hypothetical Mw7.1 Elysian Park blind-thrust earthquake, and another blind-thrust earthquake of Mw7.0). Parameters examined for the buildings include material yielding, weld fracture, presence of slab, accumulation of damage from a second earthquake, and vertical ground motion.
A significant fraction of the ground motions cause excessive amounts of deformations in the buildings, especially the 6-story one, even for the case where all welds are assumed to be perfect. These ground motions exceed the earthquake representation in the code, and, since they appear to be reasonable motions that should be considered in design, the implication is that the code design force levels need to be raised for locations in near-fault regions. Including weld fracture increases the displacements of the building and the potential for severe damage or collapse from column failure or excessive lateral sway. The buildings collapsed in several of the analyses. Including the floor slab increased the amount of column yielding and did not improve the behavior. A second earthquake such as a strong aftershock or subsequent main shock is a concern, especially if many welds are cracked from the initial event. However, a limited study of vertical ground motion showed it to be of minor importance. Strongly nonlinear building behavior is sensitive to many assumptions about features which are poorly understood, both structure and ground motion, and so the results need to be carefully interpreted.https://authors.library.caltech.edu/records/jqazq-bk791Efficient nonlinear seismic analysis of arch dams: User's manual for SCADA, Smeared Crack Arch Dam Analysis
https://resolver.caltech.edu/CaltechEERL:1997.EERL-96-01
Authors: {'items': [{'id': 'Hall-J-F', 'name': {'family': 'Hall', 'given': 'John F.'}, 'orcid': '0000-0002-7863-5060'}]}
Year: 1997
Linear earthquake analysis of a concrete arch dam, conducted either in the evaluation of an existing dam or in the design of a new one, typically shows large tensile stresses when the ground motion employed represents strong shaking. This result has spurred development of nonlinear analysis capabilities that attempt to model the opening and closing of contraction joints as well as cracks that are produced. Two recent computer programs (1a and lb, 2) both treat joints and cracks as zero-width zones of nonlinear springs connecting adjacent finite elements, but differ in detail.
ADAP-88 (la and lb) uses a multi-element discretization of solid elements through the thickness of the dam so as to be able to represent states of partial contact in the joints and cracks. Standard joint elements are used in the joint and crack planes. The program of reference 2 uses a single shell element discretization in the thickness direction with specially calibrated nonlinear rotational and axial springs to represent states of partial contact. The disadvantage of ADAP-88 is the relatively high computational effort required, while disadvantages of the formulation of reference 2 are some loss of accuracy and an inability to be generalized to include sliding in the joints and cracks. However, while sliding is straightforward conceptionally when using the standard joint elements such as employed in ADAP-88, including friction may lead to severe convergence difficulties.
At present, nonlinear analysis methods have not gained acceptance in the dam engineering community. Reliance is still based on the inadequate linear methods and ad hoc procedures to assess the high tensile stresses that are computed. Part of the problem is the difficulty of validating the nonlinear analysis capabilities. Some progress is being made, however, by different researchers taking different approaches of nonlinear analysis and then comparing results. In this spirit and also with the goal of developing a practical nonlinear analysis technique that attempts to reach a compromise between computational effort and model complexity, while still giving useful results, this simplified nonlinear earthquake analysis procedure for concrete arch dams is offered together with fully documented computer program.
The procedure is based on the "smeared" approach to model joints and cracks whereby the contact nonlinearities are incorporated through conditions placed on the stresses at the
integration points of the (shell) finite elements of the dam. This approach sacrifices some accuracy for computational efficiency. The faster computation comes about by a reduction in the number of degrees of freedom and an improvement in convergence even to the point of being able to handle frictional sliding. A typical computer run for an earthquake analysis of an arch dam to strong ground motion takes about one hour on a DEC 3000 Model 400 computer with a 100 MEPS processor. This efficiency allows parameter studies to be undertaken which are an essential part of any evaluation process.
As with the linear analysis methods, engineering judgment is still a necessary and important element. However, it is hoped that the gap between mathematical model and real-world situation is reduced enough with the offered program so that the engineer can now be confident in spanning between them.https://authors.library.caltech.edu/records/csa73-tvv57Seismic response of steel frame buildings to near-source ground motions
https://resolver.caltech.edu/CaltechEERL:1997.EERL-97-05
Authors: {'items': [{'id': 'Hall-J-F', 'name': {'family': 'Hall', 'given': 'John F.'}, 'orcid': '0000-0002-7863-5060'}]}
Year: 2001
Strong near-source ground motions contain large, rapid displacement pulses that can have severe effects on structures. In the U.S. it is generally agreed that our design codes do not adequately address this kind of ground motion, and changes are being made to increase the design force levels, which will result in stronger buildings. In Japan, the design force levels for buildings have for some time been considerably greater than in the U.S. Even so, Japanese engineers are also concerned about the adequacy of their design provisions for strong near-source ground motions.
The issue of building strength appropriate for near-source ground motions is investigated in this report. Two different heights of buildings are selected, 6 stories and 20 stories, and for each height, designs of two different strengths are produced. The first design is according to the 1994 Uniform Building Code (1), and the second design follows current Japanese provisions (2). All four buildings are steel moment frames.
One important part of assessing near-source ground motions is to quantify the size of the region that is affected. An aspect of this is that near-source effects are directional and so are confined to only a portion of the near-fault zone. In this study, ground motions at a grid of sites sufficient to cover the region of near-source effects are employed. This is accomplished by using simulated ground motions. Three earthquake simulations are run: one based on the 1994 Northridge earthquake (Mw 6.7), another for the 1995 Kobe earthquake (Mw 6.9), and the third of a hypothetical Mw 7.0 earthquake on the Elysian Park fault in Los Angeles. In addition, various recorded motions from actual earthquakes, including Northridge and Kobe, are employed.
Previous studies of strong near-source ground motions have shown the potential for large story drifts in buildings and even collapse (3-7). Future design measures for near-source ground motions will likely have to consider all contributions to the strength of a building in order to be feasible. It follows from this that since future design methods will be based on assessment studies like the present one, the assessments should also be done as realistically as possible and include all important contributions to the strength of a structure. Such an approach is followed here. In addition, since strong near-source ground motions will likely produce severely nonlinear responses, it becomes necessary to include structural degradation effects. In this study, due to the common occurrence of welded connection failure in the Northridge and Kobe earthquakes and because this behavior would seem to be an important degradation mode, treatment of connection fracture is included. As there is now wide-spread interest in fracture of welded connections, this is an important part of the present investigation.
The Appendix contains a description of the computer program used for the analyses. Some of the notation used in this report is defined in this Appendix.https://authors.library.caltech.edu/records/zew36-35m20Performance of Viscous Damping in Inelastic Seismic Analysis of Moment-Frame Buildings
https://resolver.caltech.edu/CaltechAUTHORS:20180416-115953567
Authors: {'items': [{'id': 'Hall-J-F', 'name': {'family': 'Hall', 'given': 'John F.'}, 'orcid': '0000-0002-7863-5060'}]}
Year: 2018
This report investigates the performance of several viscous damping formulations in the inelastic seismic response of moment-frame buildings. The evaluation employs a detailed model of a 20-story steel building. Damping schemes included in the study are Rayleigh, condensed Rayleigh, Wilson-Penzien, two versions of tangent Rayleigh and one implementation of capped damping. Caughey damping is found not to be computationally viable. Differences among the damping schemes, as quantified by amounts of plastic hinge rotations and story drifts, become noticeable once these quantities reach the 3% level. In order of least to greatest hinge rotations and drifts that occur under lateral response to horizontal ground motion, the damping schemes rank as Rayleigh (most damping action), condensed Rayleigh, Wilson-Penzien, the standard form of tangent Rayleigh and capped damping, which are about the same, and the elastic velocity version of tangent Rayleigh (least damping action). Performance of Rayleigh damping under vertical ground motion is discussed, including the effect of soil-structure interaction. The propensity of Rayleigh damping to generate excessive damping forces and moments during inelastic seismic analysis is explained, and a parameter is introduced that can predict the potential magnitude of the effect. A review of some literature on the role of viscous damping on the inelastic seismic response of moment frames is also presented.https://authors.library.caltech.edu/records/jq43r-40k43Comments on Philippe de la Hire's Memoir on Arch Abutment Design (1712)
https://resolver.caltech.edu/CaltechAUTHORS:20200213-143540977
Authors: {'items': [{'id': 'Hall-J-F', 'name': {'family': 'Hall', 'given': 'John F.'}, 'orcid': '0000-0002-7863-5060'}]}
Year: 2020
DOI: 10.7907/1GPB-EC73
Philippe de la Hire (1640-1718), a multi-disciplinary French scientist, is generally credited as being the first person to apply the principles of statics to the analysis and design of arches. Prior efforts employed geometric design rules that were based on experience. Thus, de la Hire plays an important role in the transition to scientifically based methods for civil engineering structures. Therefore, it is of historical interest to understand de la Hire's approach and perspective.https://authors.library.caltech.edu/records/x950r-xr114Effects of Fault Dip and Slip Rake on Near-Source Ground Motions: Why Chi-Chi Was a Relatively Mild M 7.6 Earthquake
https://resolver.caltech.edu/CaltechAUTHORS:20200518-124916954
Authors: {'items': [{'id': 'Aagaard-B-T', 'name': {'family': 'Aagaard', 'given': 'Brad T.'}}, {'id': 'Hall-J-F', 'name': {'family': 'Hall', 'given': 'John F.'}, 'orcid': '0000-0002-7863-5060'}, {'id': 'Heaton-T-H', 'name': {'family': 'Heaton', 'given': 'Thomas H.'}, 'orcid': '0000-0003-3363-2197'}]}
Year: 2020
This study focuses on how the fault dip and slip rake angles affect near-source ground motions as faulting transitions from strike-slip motion on a vertical fault to thrust motion on a shallow dipping fault. Ground motions are computed for five fault geometries with different combinations of fault dip and rake angles, and common values for the fault area and the average slip. With the fault reaching the surface in each scenario, the ground motions are dominated by Love and/or Rayleigh waves. The strike-slip faulting tends to generate Love waves, whereas the thrust faulting tends to generate Rayleigh waves. The degree to which the rupture reinforces these waves affects the severity of the shaking. For strike-slip faulting this directivity effect is most pronounced for unilateral rupture, while for thrust faulting it is most pronounced for up-dip rupture. These simulations suggest that the long-period ground motions in the 1999 Chi-Chi earthquake in Taiwan were not as severe as would be expected for other events of the same size with different styles of faulting or a deeper hypocenter.https://authors.library.caltech.edu/records/caray-a5v71