Effects of Soil–Structure Interaction on Dynamic Response of Framed Machine Foundation Resting on Raft and Piles

Abstract

Framed-foundations supporting rotary machines are either supported on a raft foundation or on a pile foundation, depending on the type of soil conditions, loadings, and other functioning requirements. Influence of soil–structure interaction (SSI) is either completely neglected or rigorously considered in the practice. Neglecting the SSI may not always be safe, and on the other hand, rigorous analyses are computationally expensive. In this paper, the SSI problem in the machine foundation is formulated using an analytical model with a lumped-mass approach and the results are compared with a three-dimensional (3D) finite-element (FE) model. The results obtained through the FE modeling technique are validated using existing results and then adopted in further analysis. From the results, it is found that simplified methods can be used for foundations resting on rock-to-dense-soil condition; however, the FE analysis is mandatory in the case of stiff-to-soft-soil conditions. It is also observed that the effects of SSI reduce the natural frequency significantly in the case of a raft-supported framed-foundation resting on soft soil strata. Pile-supported framed-foundations are considered to be a better solution in the case of soft soil conditions to control the vibrations of the framed-foundation in comparison with the raft foundations. The suitability of each foundation type for different soil conditions for limiting the displacement within the permissible values is also discussed.