Influence of Relative Lateral Stiffness and Dynamic Characteristics of Pile Foundation and Superstructure on SSPSI Response of Pile-Supported Structure: Experimental Study Using Shake Table

Abstract

The seismic design of pile foundation–supported structures has gained significant attention in the last few decades; there have been several failures during moderate to severe earthquakes. Seismic soil–pile foundation–structure interaction (SSPSI) was reported as the governing phenomenon behind the failure mechanism of such structures. In this context, in this study an attempt is made to investigate the influence of SSPSI (mainly the inertial part of the interaction) in a pile-supported structural system with variation in dynamic characteristics and the ratio of superstructure stiffness to pile foundation stiffness (Ks/Kp) through physical model experiments using a shake table. The primary aim in this study is to assess the extent of the effect of dynamic soil–structure interaction in a scaled-down pile foundation–supported bridge structure in nonliquefied ground with the help of a simplistic normalized parameter, i.e., Ks/Kp, for different ranges of the period of the superstructure system. The study primarily highlights variation of the normalized lateral period of the whole interaction between the superstructure and pile foundation as a function of the practicable range of Ks/Kp, which may be helpful for designers in predicting the dynamic characteristics of the system as a first step in seismic design. Similarly, the trend of normalized spectral acceleration and displacement response at the superstructure and pile head with respect to Ks/Kp is presented for the prediction of design forces. Finally, an idealized case study prototype design problem is used to verify the outcome of the study and illustrates simplified design steps for pile foundation–supported structures in general.