Showing papers on "Soil structure interaction published in 1983"

Dynamic Behavior of Pile Groups

Abstract: The semi‐analytical solution of the dynamic behavior of vertical pile groups is presented. The solution accounts for the pile‐soil‐pile dynamic interaction and is based on modeling the soil as a plane strain continuum and the piles as a set of finite elements. The method is generally enough to model any pile group geometry in a layered soil. The proposed method is simple since it needs no special soil modeling, accurate since its results compared well with the results of finite elements method, and cheaper to use than the finite element method. Some case studies are presented which show that the dynamic pile‐soil‐pile interaction is important for longer distances between the piles than the static case. It is shown also that correction factors due to dynamic pile‐soil‐pile interaction is frequency dependent.

Effect of soil-structure interaction on damping of structures

Abstract: Damping of structures resting on flexible foundations is affected by soil-structure interaction in two ways: (1) the structure gains damping through energy dissipation in soil, and (2) the damping the structure would have on a rigid foundation is reduced. These effects are evaluated using two approaches: an energy consideration which is a simple but approximate approach, and the complex eigenvalue analysis which is mathematically accurate but uses damped, non-classical vibration modes. These two methods are compared and the accuracy of the more convenient energy approach is assessed. Examples of modal damping are given for rigid structures, buildings and towers.

Dynamic Group Effect in Axial Responses of Grouped Piles

Abstract: Analytical expressions for soil stiffness for a group of piles were obtained for both plane strain and three dimensional conditions. A comparison between these two expressions revealed that a concept of a Winkler soil model could be applicable to pile group problems for the frequency range higher than the fundamental natural frequency of the soil deposit. A simple solution of dynamic pile group response was developed using a Winkler soil model extended to pile group problems and a transfer matrix method. Natures of dynamic group effect were studied for various cases. Using a simple structure supported by a pile group, it was demonstrated how the dynamic conditions in a group effect affects dynamic response of a pile-supported structure.

Non‐linear seismic response analysis of soil‐structure interaction systems

Abstract: This paper presents an effective analysis procedure for the dynamic soil-structure interaction problem considering not only the sliding and separation phenomena but also the non-linear behaviour of soil by the finite element method. Soil is assumed to be an elasto-plastic material and the contact surface between the soil and structure is modelled by the joint element. The load transfer method is adopted to carry out dynamic non-linear response analysis. The method is applied to the response analysis of a nuclear reactor building resting on the ground surface. The effects of non-linear behaviour of soil on the safety against sliding of the structure are examined. The numerical computations reveal the following results: that the non-linear behaviour of soil reduces the response of the system and the magnitude of sliding of the structure, and that the safety against sliding obtained by the proposed method is higher than the safety obtained by classical methods. This implies the possibility of a more rational and economical design of large structures; it can be said that the proposed method provides useful information for the stability analysis of important and large structures.

Vibration of Asymmetrical Building‐Foundation Systems

Abstract: The vibrational effect caused by an earthquake on an asymmetrical building foundation system is determined by reducing the governing equations of motion to a set of coupled integro‐differential equations involving only the interaction displacements, with the degrees of freedom of the superstructure being eliminated by the modal analysis technique. The formulation facilitates to discard the insignificant modes of the superstructure and, as such, the effort involved in the solution of the eigenvalue problem required for the modal analysis is minimal, especially for a particular class of torsionally coupled buildings. The influence of the eccentricity, shear wave velocity, and the direction of earthquake on the dynamic response of the system is investigated; as the direction of the earthquake is not known a priori, an upperbound solution for the maximum response of the system is presented. It is found that this upperbound solution is satisfactory at low shear wave velocities. At high shear wave velocities, t...

Nonlinear torsional dynamic response of footing

Abstract: A physical experiment was conducted in which dynamic torsional loadings were applied to a rigid circular model footing resting on a surcharged granular test bed. High amplitudes of strain, such as those encountered in large earthquakes, were developed. The torsional response of the footing and of selected locations within the test bed were measured. A newly developed numerical procedure, capable of solving the three‐dimensional axisymmetric nonlinear torsional wave equation, was used to simulate the experiment. The footing and test bed were modeled as a rigid disk resting on a nonlinear inelastic half space with slip permitted along the interface and on a linear elastic half space. Generally, experimental and nonlinear numerical results agreed well. It was concluded that to predict accurately the response of a soil‐foundation system when large shearing strains develop, nonlinear inelastic behavior of the soil must be taken into account. Also, it was concluded that the numerical procedure could predict acc...

Earthquake-soil structure interaction, spring and dashpot models, and real soil behaviour

Abstract: The earthquake response of a simple soil-structure interaction system is discussed. The nonlinear hysteretic properties of the soil, on which the structure is founded, are modelled. It is found that the nonlinear soil behaviour leads to a reduction in the response of the structure.

Effect of soil structure interaction on seismograms

Abstract: This paper discusses the effect of soil structure interaction on seismograms. In particular, seismograms of the 1979 Imperial Valley earthquake, taken from two instruments located close together, are discussed. One of these instruments is down hole and the other one is housed inside the recorder structure. It is shown that soil structure interaction theory accounts well for the differences in the measured vertical accelerations but not so well for the horizontal accelerations. 9 refs., 10 figs.