Finite-element analysis of a piled machine foundation

Abstract

A case study using finite-element software for the dynamic analysis and structural design of a machine foundation on piles in homogeneous sandy soil is reported. A parametric study was carried out to investigate the effect of the foundation geometry, the amplitude and frequency of the dynamic load, and the damping ratio. It is concluded that as the pile cap thickness increases the oscillation of displacement decreases due to material damping inherent in the concrete of the pile cap. There is a limit of the pile cap size at which its stiffness governs its dynamic response. Above this size the weight of the pile cap overrides its stiffness effect, and the additional weight leads to an increase in pile displacement. When the pile group size increases, the frequency at which maximum displacement occurs increases, and hence the system becomes more stable against resonance. In the case of changing the pile spacing, the maximum moment factor IM is always at the pile cap centre, where the load is applied. This factor increases when the pile spacing increases. The dimensionless displacement factor Iz decreases markedly as the pile cap length increases, reflecting the increase in displacement with pile cap length.