Effect of Superstructure on the Dynamic Response of Nonconnected Piled Raft Foundation Using Centrifuge Modeling

Abstract

In this research, a series of centrifuge modelings, including those with two different superstructures supported by a nonconnected piled raft foundation system (NPRS) in a dry sand bed, was conducted. The superstructures were simulated by 2 one-degree-of-freedom systems under two different natural frequencies. Using a shaker positioned on a centrifuge base, the sinusoidal waves with two amplitudes (.14 and .4 g) and two different motion frequencies (1 Hz and 2 Hz), as the main shaking events, were imposed to each model. A cushion layer consisting of crushed grained sand between the raft and the dry sand bed, provided secure resistance against the horizontal movement of the raft and superstructures during the shaking. The results of the modeling indicated that the internal forces, including axial forces and the bending moment, along the piles were small in the NPRS, and the effects of superstructure frequencies on these internal forces were minimal. The responses of each system at both levels of input acceleration were similar and independent of excitation frequency.