Surrogate models for the prediction of sfsi relevance in earthquake-induced vibrations of buildings: A case study

This paper examines the seismic response of a reinforced concrete building founded on a pile group embedded in a deep layer of very soft lacustrine, cemented and structured clay. A complete multi-degree of freedom nonlinear model founded on a lumped-parameter model of the soil-foundation system is used as a benchmark. A surrogate model, where the building is idealized by a simple linear oscillator and the pile group is modelled through frequency dependent linear springs and dashpots, is used to predict whether SFSI should be considered in the full response model. To this aim, a multiple stripe analysis is employed, in which input signals are grouped into stripes characterized by a given value of the spectral acceleration at a fixed period of interest. Foundation impedances corresponding for the relevant degrees of freedom are evaluated for each stripe, based on mobilized soil shear stiffness and damping ratio (stablished by site response analysis). Finally, the behavior of the compliance model, expressed in terms of maximum roof displacement, relative to the foundation, is compared to that of the fixed base building. Comparison of the results from the surrogate and full models provides indications on the predictive ability of the former to assess the relevance of SFSI at the preliminary stage of the seismic vulnerability evaluation of a building founded on piles.