Three-dimensional nonlinear seismic soil-abutment-foundation-structure interaction analysis of skewed bridges

The purpose of this thesis is to investigate the nonlinear global seismic soil-abutment-foundation-structure interaction behavior of typical highway skewed-bridge structures subjected to near-fault ground motions with high velocity pulses.; Three-dimensional nonlinear finite element models of typical bridges with various skew angles were developed. The bridge deck was modeled using shell elements referred as "shell models" and beam elements referred as "spline models". The validity of the spline models was established by comparing results obtained from shell models. There is a very good agreement between the shell and the spline models. The bridge columns were modeled as beam elements with cracked sectional properties. The abutment-backfill and the transverse shear keys were simulated using nonlinear springs. The structural models were excited using seven sets of bilateral ground motions with the near fault effects.; The limit-equilibrium methods using mobilized Logarithmic- Spiral failure surfaces coupled with a modified Hyperbolic soil stress-strain behavior referred here as the "LSH" model is employed to capture the nonlinear abutment-backfill force-displacement relationship. The validity of the LSH model was established using experimental data and nonlinear continuum finite element models. The predicted results obtained using the LSH model is in good agreement with the experimental force-displacement capacity and the finite element model.; A nonlinear Hyperbolic Force-Deformation relationship referred here as the "HFD" model is developed as a powerful and effective tool for practicing bridge engineers to develop nonlinear abutment backbone curves for typical abutment backfill.; Case study based on the recorded response of a skewed-two-span reinforced concrete box girder under strong shaking was performed. The bridge system was subjected to the three-component recorded free-field earthquake motions. The resulting dynamic response of the bridge model was found to be in good agreement with most of the motions recorded at various locations of the bridge. This validates the practical application and the methodology developed in this dissertation for evaluating the seismic response of other skewed bridges that is realistic, repeatable and reliable.