Evaluation of substructuring method for seismic soil-structure interaction analysis of bridges: Fid-Bau Portal

Evaluation of substructuring method for seismic soil-structure interaction analysis of bridges

Rahmani, Amin / Taiebat, Mahdi / Liam Finn, W.D. / Ventura, Carlos E.

Abstract This paper evaluates the commonly used substructuring method for analysis of bridge systems where the bridge is divided into two sub-systems: the bridge superstructure and the substructure including the pile foundations, abutments, and soil. Modeling of the soil-structure interaction (SSI) in the system is simplified by replacing the pile foundations, abutments, and soil with sets of independent equivalent linear springs and dashpots at the base of the superstructure. The main objective of the paper is to examine how well the substructuring method simulates the seismic response of a bridge system. The baseline data required for the evaluation process is derived from analyzing a fully-coupled continuum bridge model, already validated for the instrumented two-span Meloland Road Overpass. The same bridge system is also simulated using the substructuring method. The results from both approaches are compared, and it is shown that the differences between them can be significant. The substructuring method consistently overestimates the pier base shear forces and bending moments and the pier top deflections. Moreover, the spectral response of the bridge structure is mispredicted. The analyses are repeated for a three-span bridge system subjected to several ground motions, leading to a similar observation as before. Hence, the current state of practice for simulating seismic SSI in bridges using the substructure model is shown to be too simplified to capture the major mechanisms involved in SSI.

Highlights • The common substructuring method for simplified modeling of seismic SSI in bridges is explained in details. • The method is evaluated based on a validated continuum model of a two-span bridge and its extension to a three-span bridge. • Critical comparison of the analysis results for several ground motions reveals the weaknesses of the substructuring method.