Stiffness and load sharing characteristics of piled raft foundations subjected to dynamic loads

Abstract

Evaluation of the impedance functions and internal forces in various modes of vibration form an important step in the design of pile supported structures subjected to dynamic loads. This study tries to assess the variation in impedance functions and load distribution characteristics when a ground contacting pile cap is introduced over single and group piles. A substructuring method-based soil structure interaction (SSI) analysis model is employed to study vertical and horizontal dynamic impedances of piled rafts (PR) in homogeneous and layered soil conditions. The amplitude and phase of the dynamic interaction factor, signifying the interaction between the raft and pile group for various PR area ratios and soil conditions are evaluated. For the 2 × 2 piled rafts analysed, the dynamic load sharing between pile and raft is found to be frequency dependent in the vertical mode and practically frequency independent in the horizontal mode.