A study on the effects of piled-raft foundations on the seismic response of a high rise building resting on clayey soil

Abstract

Piled-raft foundations are often used to transfer the structural load to the depth of the soil and tall structures can be constructed on medium to soft soils by utilizing a group of piles. The static effects of a group of piles are quite evident while their dynamic effects are quite unknown and therefore, not considered in the design of the superstructure.In the present research, the performance of pile-raft foundations on the seismic response of a 20-story benchmark building resting on soft clayey soil has been investigated using a 2D finite difference model, namely FLAC. The study has been carried out by analyzing the seismic response of the structure with and without pile-raft foundations, on the surface and inside an excavation.The results show that when the structure is constructed on the surface, piled-raft foundations have a significant beneficial effect on the seismic response of the superstructure, for instance a 40% decrease in the base shear. In the case where the structure is located inside an excavation the use of piled-raft foundations are not noteworthy and do not have a considerable effect.The results of this study give an insight on the effects of pile-raft foundations on the seismic response of a superstructure to overcome the current shortage of information in this area and to better predict the behavior of tall structures in soft soil situations.