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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 80
PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: B.H.V. Topping and C.A. Mota Soares
Paper 125
Pile Group Effects in Seismic Soil-Pile-Structure Interaction D.M. Chu and K.Z. Truman
Department of Civil Engineering, Washington University in St. Louis, United States of America Full Bibliographic Reference for this paper
D.M. Chu, K.Z. Truman, "Pile Group Effects in Seismic Soil-Pile-Structure Interaction", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Fourth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 125, 2004. doi:10.4203/ccp.80.125
Keywords: soil-pile-structure interaction, radiation damping, pile group foundation, Drucker-Prager soil model.
Summary
Using a three-dimensional finite element model of a soil-pile foundation system, a
nonlinear analysis in the time domain is performed to provide a method for assessing
the seismic performance of the soil-pile foundation system. This research focuses on
kinematic seismic soil-pile-structure interaction by comparing the results of different
pile foundation configurations. Both harmonic and specific seismic excitations are
considered.
Material nonlinearity of the soil has significant effects on the seismic response of a soil-pile foundation system, as suggested by Bentley and Naggar [1] and Maheshwari et al. [2]. The Drucker-Prager plastic soil model is employed in this study to represent the nonlinear behavior of the soil. Associated flow rule of the Drucker-Prager model is considered with work-hardening behavior. The piles in the soil-pile system are considered to be linear concrete.
In order to determine an appropriate model dimension, a soil-single pile foundation
system with dynamic concentrated loads acting at the pile head is constructed. A
comparison of the pile head dynamic responses due to different finite element model
dimensions is implemented and this study suggests an analytical model with dimension
of 40m Radiation damping is defined as the energy dissipated from the finite element region of a soil-pile system by outwardly propagating waves. Chu and Truman [5] compared the dynamic response of a soil-pile foundation system using a frequency independent viscous dashpot boundary and an infinite element boundary, respectively. It was found that dynamic responses using an infinite element boundary agree with existing results of previous elastic analyses. Thus an infinite element boundary is considered in this study to represent the energy absorption by the far-field soil to avoid reflection of dilatational and shear wave energy back into the finite element model. The infinite elements are assumed to behave linearly.
Natural frequency extraction and dynamic analyses due to harmonic excitation are
performed in order to study the dynamic characteristics of both 2 The seismic soil-pile interaction problem can be explained from the perspective of energy transmission and dissipation as well. Energy from the earthquake is transmitted to the soil-pile system through the base excitation and is considered as external work acting upon the soil-pile system. The external work is transformed into internal energy and kinetic energy of the soil-pile system. The total energy of a soil-pile system is the difference between the external work and the sum of the internal energy and the kinetic energy. Internal energy is transformed into three parts: the energy lost to the quiet boundary, the strain energy and the energy due to plastic dissipation. The present study suggests that the majority of the external work is transformed into internal energy and the majority of internal energy is lost to the quiet boundary, indicating that radiation damping is predominate in the seismic analysis of soil-pile foundation systems. References
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