A NONLINEAR DYNAMIC SOIL FOUNDATION INTERACTION MODEL USING FIBER ELEMENT METHOD AND ITS APPLICATION TO NONLINEAR EARTHQUAKE RESPONSE ANALYSIS OF CABLE STAYED BRIDGE

摘要

This paper presents a multi-Winkler model for nonlinear dynamic response of foundations and its application to a nonlinear earthquake response analysis of cable-stayed bridge using the fiber element method. The nonlinear soil reactions to foundation motions are modeled by using the springs per unit area of interface between soil and foundation with 3 components corresponding to normal traction and two shear tractions on soil-foundation interface. The normal spring is modeled by a bilinear curve with no rigidity of tension and compressive capacity, for its skeleton, and a crack model, for its hysteresis loop. For the skeletons of the two shear springs, the bilinear curves with shear capacity following the Mohr-Coulomb yield criterion are used. By the Mohr-Coulomb yield criterion, the shear capacity is proportional to the normal traction and then the shapes of hysteresis loops of the two shear springs are automatically determined from the hysteresis loop of the normal traction. The resultant soil reacting forces and moments to the foundation motions are efficiently calculated by employing the fiber element method. Comparisons with the experimental hysteresis loops of rigid foundation demonstrate the potential capability of the proposed model. And also, an example of nonlinear earthquake response analysis of cable stayed bridge supported by the two caisson foundations is presented to demonstrate an applicability of the proposed model to a seismic analysis of entire system of substructure and superstructure.