Analysis and effect of piles on raft foundation for High-Rise framed structure under seismic loading

Abstract

In recent years, the usage of piled raft foundations has grown in popularity because the collective response of the raft with piles may enhance soil load carrying capacity, minimize the settling of soil, and the piles may be positioned for preventing unequal deformation in the mat. A stacked raft foundation is less expensive than a piled foundation. As piles are not required to reach the whole thickness of the clayey soil, they may be ended at upper altitudes. Raft foundation with piles is a novel idea by which the complete weight of the structure above is carried partially by the mat slab via soil interaction and partially carried through piles via surface friction. The seismic analysis of a stacked raft foundation is performed in this work utilizing CSI Safe software and response spectrum analysis load cases obtained from ETABS. For the analysis, the G + 10 story structure is taken and designed in ETABS and support reactions were transferred from ETABS to safe software. The analysis had been performed for different values of soil bearing capacities and different thicknesses, the diameter of the pile, and the length of the pile. The effect of different parameters had been analyzed on the foundation design. The results demonstrate that changing the diameter of piles from 200 mm to 400 mm and raft thickness from 300 mm to 500 mm, leads to a 68.66 % reduction in the deformation of the raft slab. After performing the study, it had been concluded that piles provided with raft foundation improve the performance and capacity of the raft foundation under seismic loading and this type of foundation can be used where soil bearing capacity is low.