Probabilistic Seismic Design of Soil-Pile Raft-Superstructure System

Abstract

Sustainable design of foundations and structural members requires safe and environmental friendly structure with minimum material use. Piled-raft foundations are commonly used to support heavy structures in soft soil. Traditionally, seismic design of such structure is carried out considering fixity at base level in a soil-pile raft-structure system while pile head is considered to be fixed for design of pile. Major drawback of this fixed base assumption is that it cannot capture soil structure interaction (SSI) effect. Incorporation of SSI may result in increased or decreased transmitted shear to the pile and column as compared to fixed base shear which may lead to unsafe or over-safe pile design. Since natural soil properties vary at different points within geologically distinct layers. As a result, transmitted shear to the pile and column depends on in situ variability of design soil parameters, thus leads to transformation of the whole problem to reliability based SSI design problem. Thus, precise estimation of safety margin is needed for rational and sustainable design of pile. Hence, a probabilistic analysis incorporating SSI is performed in present study to develop insight into the problem for refining the existing design guidelines.