Orthogonal Seismic Demand Estimation of Horizontally Curved RC Box-Girder Bridges in Time History Analyses Using Combination Rules

Analyzing a bridge with all possible excitation angles for design purposes is impractical. Combination rules have been developed as an alternative for computation of orthogonal seismic demands. The main goal of this paper is to evaluate the ۱۰۰/۳۰, ۱۰۰/۴۰, and SRSS combination rules for linear and nonlinear time history analyses of horizontally curved four-span RC box-girder bridges with seat-type abutments. Ground motion records are applied to the bridge models in two cases: ۱) only the major components of earthquake records are used; ۲) paired acceleration time histories are used. Results showed that the second case provides larger response predictions in comparison with the first case. Drift and displacement demands are best estimated using the ۱۰۰/۴۰ combination rule with the major components in both linear and nonlinear analyses. Depending on curvature, both the ۱۰۰/۴۰ and SRSS rules are suggested to predict internal force demands of the superstructure.

Keywords:

Curved bridge , Combination rules , Seismic response , Time history analysis