First insights on the effects of inclined pile foundations on the nonlinear seismic response of bridge piers

This paper presents first results of a research focused on the effects of piles layout and inclination on the nonlinear seismic response of bridge piers. In particular, some case studies are analysed highlighting some interesting aspects of the research. The analysis methodology, based on the substructure approach, is firstly presented. The soil-foundation system is studied in the frequency domain according to a numerical model developed by the authors that allows computing the frequency dependent impedances of the soil-foundation system as well as the foundation input motion. The inertial interaction analysis of the superstructures are performed in the time domain to capture the non-linear structural behaviour and a suitable lumped parameter model is used to approximate the frequency dependent behaviour of the soil-foundation impedances in the time domain analyses. The procedure is applied to some case studies constituted by single bridge piers found-ed on a soft clayed soil halfspace. Two pile group configurations, characterised by vertical and inclined piles are considered, as well as piers with different yielding bending moments of the base cross sec-tions, to simulate systems with different ductility capacity. The linear behaviour of the systems is also investigated for comparison. Effects of soil-structure interaction are evaluated considering results of fixed base piers as benchmark; analyses demonstrate that inclined pile foundations may have a significant impact on the superstructure re-sponse, reducing the pier head displacements and ductility demand.