Numerical modeling of seismic soil-pile-superstructure interaction in soft clay.

摘要

The prediction of structural performance of systems supported on pile foundations is of paramount importance in the seismic design and assessment of new and existing structures. The main focus of this dissertation is the formulation, implementation, and calibration of a coupled model for the analysis of the seismic soil-pile-superstructure interaction (SSPSI) problem. A series of large-scale SSPSI model tests previously performed on the large shaking table at the University of California, Berkeley was used to calibrate the proposed numerical technique.; The coupled formulation incorporates the Beam on Nonlinear Winkler Foundation (BNWF) model for the soil-pile-superstructure system and a nonlinear model for site response analysis. The nonlinear enhanced hysteretic model for site response analyses has only three material parameters and is able to closely reproduce experimental shear modulus degradation and damping curves for several soils, ranging from clays, silts and sands. To obtain the near field response of the model soil used in the shaking table test, laboratory pot-tests were also performed and showed that API design curves provided a reasonable and conservative approximation to the near field response of the model soil. A nonlinear one-dimensional element with gapping capabilities was formulated and implemented to simulate the experimental results.; The implementation of the coupled model was initially evaluated by comparison with measured response from a centrifuge test and provided practically identical results to those obtained using other validated computer codes. The coupled model formulation was then used to simulate the shaking table tests conducted at U.C. Berkeley. Numerical analyses showed that the new nonlinear model is superior to the equivalent linear procedure in predicting the observed free field behavior. Structural and near field soil response for systems supported on single piles were closely modeled by the proposed formulation. The coupled model was also applied to the analyses of pile groups using the equivalent pier concept and considering pile cap resistance. The numerical technique was calibrated with the observed superstructure responses and an intensity based equivalent p-y efficiency for the pile groups was developed.