Seismic analysis and assessment of a skew highway bridge

The seismic response of a skew reinforced concrete box girder bridge—the Foothill Boulevard Undercrossing—is analyzed and studied using finite element models. The effects of superstructure flexibility, substructure boundary conditions, structural skewness and stiffness eccentricity are assessed using spectral analyses. The results show that the internal forces and displacements of the supporting columns as well as the displacement of the deck will be underestimated if one neglects the flexibility of the bridge deck. The study also demonstrates that the seismic response of the bridge is affected quite noticeably by the boundary conditions of the bridge columns and the overall skewness of the bridge. Based on this study, a theory to explain the failure of this bridge is presented.