Dynamic analysis of piled raft foundations: Influence of superstructure and geometric parameters

Designers opt for piled raft foundations in response to the rise in demand for high-rise structures and significant infrastructure in metropolitan regions with low soil-bearing capacity. However, analytical and numerical studies that consider both the foundation and the superstructure are scarce in the literature. Considering the superstructure, even in its simplest form, is decisive for assessing the combined behavior of the piled raft. This study aims to examine how variations in several significant factors affect the dynamic behavior of a piled raft foundation structure system in loose sand. The combined piled raft system (CPRF) is modelled using the three-dimensional finite element software Plaxis 3D. An extensive parameter-based investigation is performed to appraise the impact of crucial factors such as raft thickness, pile spacing-to-diameter ratios, and varied pile lengths on the dynamic and seismic behavior of the combined piled raft foundation structural system. It is noted that the fundamental time period of the piled raft structure system is increased substantially when compared to a piled raft foundation without a structure and with reduced raft thickness. Additionally, there is a noticeable decrease in base shear at the head of the pile.