Humboldt Bay Middle Channel Bridge: 3D bridge-foundations-ground system

none4Soil-Structure interaction may play a major role in the seismic response of a bridge structure. Specifically, a significant reduction in soil stiffness and strength may result in permanent displacement of the abutments and foundations, thus imposing important kinematic conditions to bridge structure. This paper is aimed at showing the effects of this behavior referring to the Humboldt Bay Middle Channel Bridge, in California. The Finite Element model and nonlinear solution strategy are built in the open-source software platform OpenSees. The 3D nature of bridge response imposes significant computational challenges. The soil is modeled as a nonlinear material with a Von Mises multi-surface kinematic plasticity model so as to reproduce elasto-plastic shear response. The results obtained using 1978 Tabas earthquake record shows that changes in properties of the superficial soil layers dictate significantly different time histories of dynamic excitation at the various support points of the bridge (piers and abutments).openTrombetti T.; Gasparini G.; Elgamal A.; Forcellini D.Trombetti T.; Gasparini G.; Elgamal A.; Forcellini D