NONLINEAR SEISMIC ANALYSIS OF A BRIDGE GROUND SYSTEM

Abstract eng:
This paper presents a two-dimensional yet advanced nonlinear finite element model of a real bridge system, the Humboldt Bay Middle Channel Bridge near Eureka in Northern California, and its response to a seismic input motion. The computational model of the Middle Channel Bridge is developed using the new software framework OpenSees developed by the Pacific Earthquake Engineering Research (PEER) Center to combine advanced structural and geotechnical seismic response simulation capabilities. The model incorporates soil-pile-structure interaction. Realistic nonlinear material models are used for the concrete (confined and unconfined), reinforcing steel, and soil materials under cyclic/dynamic loading. The materials in the various layers of the supporting soil medium are modeled using an effective-stress, multi-surface plasticity model incorporating liquefaction effects. A seismic response analysis is presented, with soil properties weaker than the actual ones, in order to test the robustness of the numerical framework, and explore potential effects of liquefaction on the various components of the bridge system. The simulated response shows that liquefaction-induced lateral spreading may have severe implications on the seismic demand imposed on the bridge structure (piers, piles, approach slab).

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