Cost-effective analysis technique for the design of bridges against strike-slip faulting

The paper studies the performance of a typical overpass bridge, with continuous deck and monolithic pier-deck connections, subjected to strike-slip faulting. A three-dimensional (3D) finite element (FE) model of the entire bridge-foundation-abutment-soil system is developed, accounting for soil, structure and geometric nonlinearities. Soil behaviour is simulated with a thoroughly validated strain softening constitutive model. The concrete damaged plasticity (CDP) model is implemented for piers, accounting for the interaction between axial force N, bending moment M, shear force Q and torsion T (NMQT); the model is validated against experimental results from the literature. The location of the fault rupture is parametrically investigated, confirming the vulnerability of indeterminate structural systems to large tectonic deformation. The deck is shown to sustain both in-plane and out-of-plane bending moments, as well as torsion; the piers are subjected to biaxial bending, shear and torsion. The response is highly dependent on the location of the fault rupture, emphasizing the need to develop cost-effective modelling techniques. Four such techniques are developed (with and without decoupling) and comparatively assessed using the detailed 3D FE model as benchmark. The best prediction is achieved by a coupled model, which includes the bridge superstructure, detailed 3D modelling of the soil-foundation system only for the pier directly affected by the fault, and nonlinear springs representing the foundations of all other piers. The proposed technique offers a computationally efficient means to parametrically analyse long multispan bridges subjected to faulting, for which full 3D FE modelling is impractical.