Sensitivity of seismic response of pile-supported, multi-span viaduct bridges to interaction between soil-foundation and structural parameters

Soil-structure interaction (SSI) in pile-supported bridges coupled with non-linear behavior of the structural bridge elements is a complex problem. A sub-structuring technique that accounted for the kinematic and inertial SSI effects and non-linear finite element method (FEM) numerical model in the software SAP2000 were employed to investigate the response of a typical 4-span continuous bridge in two orthogonal directions founded in five soil profiles belonging to AASHTO site classes C and D. The FEM analysis results were disaggregated to delineate the effect of SSI and pier column inelasticity (PCI) on three output quantities, i.e., bridge deck acceleration (A), bridge displacement (delta), and pier column shear force (V). Sensitivity analysis, conducted using Morris method, ascertained the influence of SSI and PCI on the output quantities. It was revealed that all three response quantities were more sensitive to PCI in both orthogonal directions in all soil profiles compared to SSI. However, sensitivity of the response quantities to SSI was significant in the transverse bridge direction in all but one soil profile, which was explained through a lumped parameter model. Contrary to the current AASHTO code requirement, the inclusion of SSI for the design of pile-supported bridges in all seismic design categories (SDCs) is recommended for the bridge typology studied herein.