Dynamic Axial Response of Tapered Piles Including Material Damping

Tapered piles are used in place of cylindrical piles for their improved geotechnical performance. When tapered piles are subjected to axial dynamic loading, as is the case with machine foundations, an appropriate theoretical formulation must be used to obtain an accurate representation of the dynamic response. Material damping, which is the energy loss due to particle deformations, friction, and heat, is often neglected in analyses for simplicity. However, previous researchers have not quantified the implications of neglecting material damping during the dynamic design of tapered piles. The present study uses advanced symbolic computation techniques to introduce material damping within the existing theoretical formulations reported in the literature. Numerous hypothetical case studies are defined to represent a range of realistic site conditions, and the influence of material damping on the dynamic axial response is assessed. It is shown that in all cases, material damping acts to reduce the resonant amplitude and increase the resonant frequency, with the shift in resonant peak being more pronounced for piles founded in soft soils. Provided that adequate dynamic site data are available, material damping should be incorporated within the dynamic axial analyses of tapered piles to produce a more comprehensive representation. (c) 2020 American Society of Civil Engineers.