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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenThu, 30 Nov 2023 19:40:51 +0000Analytical Studies of the Dynamic Response of Certain Structures to Assumed Ground Movements
https://resolver.caltech.edu/CaltechETD:etd-09112007-075818
Authors: White, Merit Penniman
Year: 1935
DOI: 10.7907/3Y5W-NG36
This investigation is chiefly concerned with the effects of earthquakes upon various structures. Several of the chapters are quite far afield but are included with the thought that they deal either with earthquakes or with structures, and are, at least to some extent, related to the principal subject of this discussion.
https://thesis.library.caltech.edu/id/eprint/3466The Analysis of Stresses in a Thin Cylindrical Shell of Circular Cross-Section
https://resolver.caltech.edu/CaltechETD:etd-06192007-131244
Authors: Byrne, Ralph Edward
Year: 1940
DOI: 10.7907/4542-J330
In Part I., the equations of equilibrium and expressions for the strain components are set up, for a thin shell of a general shape, by the use of the methods of vector analysis. The simplicity of the vector method of approach to this problem is shown.
In Part II., the theory developed in Part I. is particularized for the case of a circular cylindrical shell. Expressions for force components are obtained in terms of the deformation components, and three equations of equilibrium in terms of the three deformation components are derived.
In Part III., the expression for strain energy for a circular cylindrical shell is set up, and, by means of the Principle of Virtual Work, equilibrium equations and boundary conditions for a general type of boundary are deduced. The boundary conditions are then particularized for the cases in which the boundaries are parametric curves.
In Part IV., an exact solution of the differential equations derived in Parts II. and III. is obtained. This solution is applicable to circular cylindrical shells of the type which occurs in the problem of the design and construction of barrel roofs.
In Part V., the exact solution of Part IV. is carried out numerically for two particular cases.
In Part VI., an account of several approximate methods of solution of this problem is given. A brief summary of some of the 1iterature on this subject is included. The thesis is concluded with a rather detailed account of several of the methods by which the author attempted to obtain short and approximate solutions of this problem.https://thesis.library.caltech.edu/id/eprint/2648An Investigation of the Effects of Earthquakes on Buildings
https://resolver.caltech.edu/CaltechETD:etd-05092003-152001
Authors: Housner, George William
Year: 1941
DOI: 10.7907/CTJR-HD62
The forces induced in buildings by earthquakes are here investigated. The effects of some of the physical properties of structures are determined and from an analysis of earthquake records the general character of earthquakes is deduced. An investigation is also made of the dissipation of energy of vibration to the propagation of elastic waves in the ground.
This thesis was written to contribute to the program of earthquake research that Professor Martel has been carrying on for the past ten years. As such, it is a continuation of the work done by M. A. Biot and M. P. White. Acknowledgment is made of the financial support of the County of Los Angeles which made possible the analysis of the earthquake records.
Sincere appreciation is expressed to Professor R. R. Martel for the advice he has given and the interest he has shown.
SUMMARY
All the earthquakes analysed are of the same general character. There are no special features distinguishing any one earthquake from another. There is no evidence that the physical properties of the ground have any effect on the character of the earthquake.
In the range of periods from 2/10 seconds to 2 seconds, all ground waves are of approximately equal importance. There are no predominating periods of ground waves.
The analysis of records provides a convenient method of measuring the intensities of earthquakes. A scale of intensities constructed in this manner is shown in the following table:
Scale of Earthquake Intensities
El Centro, May, 1940 -- 100
Long Beach, March, 1933, (at Vernon) -- 65
El Centro, December, 1934 -- 60
Helena, Montana, October 31, 1935 -- 55
Ferndale, September, 1938 -- 40
Los Angeles, October, 1933 ? 17
The analysis of the records shows that there is no so-called "dominant ground period".
For undamped structures, with periods of vibration longer than about 2/10 of a second, the maximum shearing force at the base is, for practical purposes, independent of the height of the structure and independent of the period of vibration.
For such structures the maximum shearing forces are independent of the total mass of the structure but for ordinary construction vary in direct ratio as the mass per floor level.
When the height of a structure is increased, the shearing forces in the upper portions of the structure are increased.
Only the first few modes of vibration are of importance in producing shearing forces.
For undamped structures flexibility and lightness of construction will reduce the magnitudes of the shearing forces. However, the flexibility of the first story alone has little effect upon the maximum shearing force at the base of the structure, although it does reduce the shearing forces in the upper portions of the structure.
Considerable elastic yielding of the ground may take place at the base of a structure without having sufficient effect on the accelerogram to be distinguished by analysis of the record.
The energy dissipated into the ground may be an important factor in reducing the shearing forces. The analysis shows that the reduction in shearing forces due to energy lost in wave propagation is greater for high frequencies than for low frequencies, and is greater for ground of low rigidity than for ground with high rigidity. Tables are constructed which indicate that structures with high frequencies may have their shearing forces appreciably reduced by this energy dissipation. It appears, however, that structures with periods of about 1 second will be little affected.https://thesis.library.caltech.edu/id/eprint/1694A Study of the Effects of Rapidly Applied Loads and Repeated Loads on Countersunk Riveted Joints
https://resolver.caltech.edu/CaltechETD:etd-12192008-111017
Authors: Soli, Orlan Alton; Ditch, William Earl
Year: 1947
DOI: 10.7907/WEWA-8A78
A number of tests were conducted at Daniel Guggenheim Aeronautical Laboratory to determine the effects of rapid loading and repeated rapid loading on countersunk riveted joints. This investigation was conducted to indicate the importance and possibilities of future study in this field.
The rapid loading test results are compared to slow loading tests and to ANC-5 and Aircraft Industries Association of America values.
A hydraulic testing machine designed for these specific tests was constructed and placed in operation. A general discussion of the testing machine and its operation is included.
https://thesis.library.caltech.edu/id/eprint/5080An Investigation of Inspection Criteria for Countersunk Rivets
https://resolver.caltech.edu/CaltechETD:etd-12082008-091447
Authors: Sanders, Lewis B.
Year: 1947
DOI: 10.7907/X2ZV-8G18
An investigation was made of the existing flush rivet inspection criteria and inspection methods to establish a norm for commercial flush riveted joints. Studies were made of thirty-four flush riveted joint load deformation curves to obtain their general characteristics and to establish some correlation of yield load as defined in ANC-5 and as defined in Report on Flush Riveted Joint Strength by ARC Rivet and Screw Allowables Subcommittee (Airworthiness Project 12). The specimens corresponding to the load deformation curves were comprised of 18 machine countersunk joints, 12 double dimple joints and four sub-countersunk joints. Within each type of joints the specimen varied in series of sheet material and thickness, rivet material and rivet size.
It is shown that yield load, defined as load giving four percent of rivet diameter joint set, is dependent on d/t ratios, the yield load lowering at increasing d/t values. Also, there are indications that as softer rivet material is used with a given sheet material, the increasing d/t ratios have less adverse effects.
There could be made no particular correlation of yield load as defined by load at .005" set with any of the varying parameters.
In the case of the double dimple and sub-countersunk joints, no particular conclusions could be reached as the test data was confined to a small range of d/t values.
It was concluded from the countersunk rivet data that permanent set based on rivet diameter is a more reasonable yield criterion than permanent set based on an arbitrary constant.
https://thesis.library.caltech.edu/id/eprint/4879An Investigation in the Reduction of Tabulated Loads for Bolted Joints Fabricated of Green Douglas Fir
https://resolver.caltech.edu/CaltechETD:etd-10062005-130130
Authors: Harris, Robert Blynn
Year: 1947
DOI: 10.7907/4D9Y-VF55
Because of restrictions and shortages of materials and labor caused by World War II, the lumber industry has been forced to place on the market a great deal of lumber that is in a green condition. Consequently designers and engineers have been required to make use of this material.
Specifications currently being used for the design of bolted joints in wood structures require that the allowable loads as tabulated therein be reduced when the material used is green. In most cases this reduction is in the order of two thirds the tabulated value, that is to say the allowable working stress is one third the tabulated value. The conservativeness of this requirement has been questioned and it has been the purpose of this investigation to attempt to arrive at a load reduction ratio which would give a greater allowable load and a subsequent saving in labor and materials.https://thesis.library.caltech.edu/id/eprint/3943A Fourier Integral Approach to an Aeolotropic Medium
https://resolver.caltech.edu/CaltechETD:etd-04142009-143250
Authors: Quinlan, Patrick Michael
Year: 1949
DOI: 10.7907/CTQV-V186
Chapter I: The equations of equilibrium in terms of the displacement components for an axially symmetric aeolotropic medium are developed from the strain-energy function of the medium. Then follows a discussion of the literature of the subject, and an outline of the scope of the present thesis.
Charter II: The solution is carried through using Fourier Integral technique for the two dimensional plane strain case. Stresses and displacements are obtained for a concentrated line load.
Chapter III: The results of Chapter II are applied to determine the surface settlements, vertical pressures, and shears for a symmetrically loaded strip called "the unit strip" of width two units. The following special load distributions are investigated: concentrated, uniform, parabolic, inverted parabolic, hollow wall, and rigid wall. Extension is then made to a strip of any arbitrary width 2a, and settlements are obtained by means of influence factors, (Graph I). An examination is made of the influence of the type of load distribution, demonstrating St. Venant's principle of equipollent loads.
Chapter IV: The equations of Chapter I are solved for an axially symmetric loading by transforming to polar co-ordinates and using Fourier-Bessel Integral technique. The solution is carried through for the concentrated load case, and the results check those given by Mitchell (6).
Chapter V: An investigation similar to that made in Chapter III is made for a loaded circular area of unit radius. The results are then extended to a circle of any arbitrary width a. Surface settlements are obtained quickly by means of influence factors (Graph II). In the latter part of the Chapter series expansions are obtained for the stresses and displacements at any point in the mass, and application is made to some of the more practical load distributions.
Chapter VI: Corresponding results for an elastic isotropic medium, to those given in above chapters, are obtained by the application of a limiting technique to above results. The ease with which the results are obtained is striking. A discussion is given of the infinite surface displacements that are usually obtained in two-dimensional problems.
Chapter VII: In this chapter a review is made of the literature of the three constant medium. The physical significance of the assumptions and the measure of fulfillment of these assumptions by some types of wood, and by some crystals, is examined. Some errors are noted, and corrected. Finally all are shown to be just particular cases of the medium of Chapter II, without having the redeeming feature of simplicity over the more general theory.
Chapter VIII: Results for Orthotropic plates are deduced from those given in Chapter II by a change of constants.
Chapter IX: Typical problems in soil mechanics connected with a loaded column, and with a loaded wall, are worked out in detail. Graph III shows for a particular case the effect aeolotropy may have on the vertical stress distributions in a loaded soil. A brief outline is made of some other problems in an aeolotropic medium capable of solution by the methods of this thesis.
Appendix F: Practical methods are given for the determination of the required constants. The value of skew samples is shown. The results obtained in this thesis for an aeolotropic medium, apart from the concentrated case given by Mitchell(6), are new. A good test of the accuracy of the work is provided by the known isotropic elastic results obtained by a limiting procedure in Chapter VI. As far as the author is aware, some of the results of Chapter VI are new also. The direct application of Fourier Integral technique to the displacement equations of equilibrium is very rare in elastic problems. This thesis illustrates the power and simplicity of such an approach. Finally, as shown in Chapter IX the results are very readily adapted to practical use.https://thesis.library.caltech.edu/id/eprint/1388The Effect of pH on the Workability of Concrete
https://resolver.caltech.edu/CaltechTHESIS:12042017-111708147
Authors: Linderman, Robert Bruce
Year: 1952
DOI: 10.7907/C141-5S39
<p>It was believed that the pH of concrete would affect
the workability. The effect of pH on the workability was
determined experimentally by adding chemical admixtures
to a cement mortar mix, measuring the pH and workability.</p>
<p>pH was measured by a Beckman Glass Electrode pH
Meter equipped with a standard Calomel electrode and a
special type "42" glass electrode. The use of the type "42"
glass electrode made it possible to place the electrodes in
wet cement mortar without damage.</p>
<p>The workability was determined by measuring the
penetration of a three inch diameter cylinder with a
hemispherical tip. This ball penetration measure of workability
has a linear relationship to that measured by the slump test.</p>
<p>From these tests it was found that the pH has no effect
on the workability of cement mortar. The admixtures changed
both the pH and the workability, however, the variations in pH
and workability were independent of each other. It is believed
that the major factor which affects the workability of concrete
is the dispersing effect of the admixture on the cement.</p>https://thesis.library.caltech.edu/id/eprint/10578A Rational Design Procedure for Machine Foundations
https://resolver.caltech.edu/CaltechTHESIS:12012017-090837077
Authors: Pauw, Adrian
Year: 1952
DOI: 10.7907/MZVV-X944
<p>The problem involved in the design of machine foundations are
discussed, followed by a short review of the literature of the subject.
The general theory of vibration for single and multiple degree of freedom
systems is briefly reviewed, with special emphasis on its application
to machine foundation design. A procedure for the analysis of machine
foundations is then developed on the basis of a simplified equivalent
system. Procedures for determining the elastic coefficients and the
inertia parameters of the soil are next considered.</p>
<p>The purpose and extent of the experimental investigations are
discussed, followed by a description of the instrumentation used and
the nature and accuracy of the data obtained. The data is then
analyzed and checked against the theory presented. The data required for
the design of machine foundations is discussed, and a procedure for
design and analysis is recommended. In conclusion recommendations for
further study and research are made.</p>https://thesis.library.caltech.edu/id/eprint/10575