Browsing by Author "Holt, E. C."
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Item A new stiffness matrix for the analysis of the bending of plates using rectangular finite elements(1966) De Andrade, Jose Carneiro; Holt, E. C.A, new displacement function is obtained for the analysis of the bending of plates using rectangular finite elements which satisfies the conditions of compatibility across element boundaries as well as throughout the elements. The improvement in accuracy and convergence-is studied by com-paring the results of some problems with those obtained by Zienkiewicz and Cheung using a different displacement function. Also, some results are compared with known exact solutions and with the results obtained by other methods. Finally, a displacement function is proposed for the analysis of the bending of plates bounded by coordinate lines in polar coordinates, using elements consisting of annularsectors.Item An analysis of shells by a framework analogy(1964) Harris, Gilliam S; Holt, E. C.The lattice analogy for plates is extended to shells. The analogous structure is a space frame composed of pin jointed members which represent the shell and stiff jointed members which represent edge beams or stiffening ribs. It is analyzed by the displacement method. Effects due to foundation settlement and temperature change are simulated by use of the analogous structure. For a given shell and all applied conditions there may be determined the deflections, secondary stresses, reactions, edge beam forces (moments, axial forces, and shears), and for each element in the shell, the maximum average stress, and the maximum shear. A comparison of the stresses computed by this method with those given by ideal membrane theory is good.Item An analytical study of a space frame(1960) Leach, Richard Peter Parton; Thibodeaux, Murphy H.; Pfeiffer, Paul E.; Holt, E. C.Item Analytical study of a rigid jointed space frame on elastic supports(1961) Desai, Ardeshir R; Thibodeaux, Murphy H.; Wilhort, J. C., Jr.; Holt, E. C.Item Cost optimization of plate girders by dynamic programming(1967) Heithecker, Gary Lee; Holt, E. C.An algorithm is developed for the optimum design of a single span steel plate girder with equal flanges and unstiffened web. The height of the girder varies linearly. The flange width, flange thickness, and web thickness are discrete variables. The algorithm is formulated as a multilevel decision making process. The optimum values of the design variables are obtained subject to nonlinear behavior functions limiting stresses and deflection, and side constraints restricting the range and independence of the variables. A nonlinear objective function involving cost of material and fabrication is used as the criterion for optimization. Optimization procedures are formulated using dynamic programming. The characteristics of the algorithm are demonstrated by a number of design examples, and the designs produced by the algorithm are related to the traditional design procedure.Item Dynamic response of machine-foundation systems(1965) Marshall, Donald William; Holt, E. C.A method of analysis is presented for the dynamic response of large machine-foundation systems. The general case of several machines on a common flexible mat is considered. The origin and types of machine exciting forces are discussed. Particular emphasis is given to the unbalanced inertial forces in reciprocating gas compressors. It is with this type of machine that most serious foundation problems occur. The soil is assumed to be homogeneous and isotropic with both inertial and elastic properties. While this simplification is not compatible with the observed properties of most soils, it gives satisfactory results for this application. An outline of a theoretical method of vibration analysis is presented which can be adapted for use with a computer. The method is applied to the general machine-foundation system. An example analysis is made of a single engine driven gas compressor and its foundation. The natural frequencies and amplitudes of motion are calculated. Recommendations are made for the practical application of the analytical procedure based on the present limitations on the accuracy of dynamic soil data.Item Dynamic response of shear beam type buildings(1967) Goncalves da Silva, Manuel Americo; Holt, E. C.An analytical Investigation is made of the dynamic response of multi-degree-of-freedom shear beam type buildings excited by transient lateral motions of the base. The response quantities studied are the horizontal displacements of stories relative to the base, the interfloor deformations, the shear forces and induced overturning moments at the story levels. The contribution of the various natural modes of vibration to the response is extensively examined. A representative stiffness distribution is chosen for buildings with constant story masses and a wide range of fundamental frequencies considered. The input notions taken are piece-wise linear; a standard simple pulse and en earthquake motion wore selected for this study. The dependence of response quantities on the fundamental frequency of these structures is examined on as to provide a basis for anticipating the behavior which may be expected. The results are graphically summarized.Item Effect of costs on optimum proportions of plate girders(1969) Nickols, Robert Fred; Holt, E. C.The proportions of optimum steel plate girders are investigated using a dynamic programming scheme. The optimum properties are determined for realistic steel material and fabrication costs as well as for constant material cost, or minimum weight. Simply supported, uniformly loaded, unstiffened symmetric plate girders are considered. The effect of steel industry pricing practices on the optimum dimensions of a girder are illustrated. The effect of using commercially available plate sizes is also investigated. The optimum geometrical configuration is highly sensitive to pricing practices and available plate sizes; the overall girder weight and cost, however, are rather insensitive to changes in geometry caused by unit material cost differentials.Item Effect of girder flexibility on the dynamic response of buildings subjected to ground motion(1967) Olstad, Paul Melvin; Holt, E. C.An investigation is made of the effect of the flexibility of girders on the dynamic response of multistory buildings to lateral motions of the base. The response quantities examined are story displacements, interfloor deformations , and story shears; A numerical analysis is made on a realistic building designed in accordance with AC I code recommendations for constant floor masses and seismic shears as recommended by the Structural Engineers Association of California. Rotary inertia and vertical inertia of the joints are neglected. The building is approximated by two models. These are a frame model having flexible girders and extensible columns and the shear-beam model having infinitely rigid girders and inextensible members. A comparison is made of the behavior of the two models when excited by a half-cycle displacement pulse. The response quantities are shown in graphical form for a wide range of fundamental frequencies. It is found that the fundamental frequency of the building is substantially different in the two representations. The shears are found to be greatly underestimated by the shear-beam model for high frequencies. Displacements and deformations differ most markedly for the two models in the first story and are almost. identical in the top stories.Item Transient response of a harmonic oscillator with quadratic damping(1967) Goering, Kent LaVerne; Holt, E. C.An analytical investigation is made of the transient response of a harmonic oscillator with damping proportional to the square of the velocity. The input motions considered are the half-cycle velocity pulse and the half- cycle displacement pulse. The response quantities studied are the maximum displacement, velocity, arid acceleration of the system. Results were obtained by integrating the equation numerically and are summarized in the form of response spectra. The results are compared to those obtained with linear damping; a method for obtaining equivalent linear damping coefficients is given. The study indicates that quadratic damping is most effective in reducing responses in the range of frequencies for which the responses are the largest. For lightly damped systems, quadratic damping was found to be equally effective in reducing each of the three responses studied. But for heavily damped systems it is most effective in reducing velocities.