A B S T R A C TThis paper studies the effects of the use of inclined pile foundations on the seismic response of bridges, andshows that this type of foundation is able to promote significant reductions in the ductility demand of reinforcedconcrete piers. To this end, a set of nine multi-span roadway viaducts with different pier heights and span lengthsis defined. Each configuration is designed and dimensioned in detail following a displacement-based approach, considering both linear and non-linear expected behaviours and assuming different target ductilities for piers.The systems are assumed to be founded on a specific soil profile, and suitable pile foundation layouts anddimensions are determined for each case, with four different pile rake angles (including the vertical case) in each configuration. Soil-structure interaction phenomena are incorporated through the corresponding frequencydependent impedance functions and kinematic interaction factors. The transverse response of the viaducts, subject to a set of seven suitable scaled real accelerograms, is computed and analysed making use of a substructuring approach and non-linear time-domain analysis in which a lumped parameter model is adopted to represent the foundation response. Results, presented not only in terms of ductility demand but also of energy dissipated in the structural system by damping or by yielding, suggest that inclined piles are clearly beneficial tothe seismic response of bridges, contributing to significant reductions in ductility demand due to the particular kinematic seismic response of this type of foundations and associated reductions in the input seismic energy to the system. https://doi.org/10.1016/j.engstruct.2019.109873

SummaryThis paper presents a wide parametric study aimed at elucidating the influence, on the computed seismic response of bridge piers, of two related aspects of the model: (1) the adoption of the classical hysteretic or the causal Biot's damping models for the soil and (2) the use of two different lumped parameter models of different complexity and accuracy to approximate the impedances of the pile foundation. A total of 2072 cases, including different superstructures, pile foundations, soil deposits, and seismic input signals, are studied. The results arepresented so that the influence of the different parameters involved in the analysis can be assessed. From an engineering point of view, both lumped parametermodels provide, in general, sufficiently low errors. The choice of the most adequate model for each case will depend not only on the configuration of the structure and the soil-foundation system but also on the assumed soil damping model, whose influence on the computed seismic responses is relevant in many cases. The nonphysical behaviour provided by the classical hysteretic damping model for the soil at zero frequency generates issues in the process of fitting the impedance functions. It is also found that larger deck displacements are predicted by Biot's model due to the higher damping at low frequencies provided by the classical hysteretic damping model. https://doi.org/10.1002/eqe.3137