Evaluation of Combination Rules for Orthogonal Seismic Demands in Nonlinear Time History Analysis of Bridges

Abstract

One of the parameters that directly affects the seismic demand on a bridge is the excitation angle of the ground motion. Since analyzing a bridge with all possible excitation angles is impractical, combination rules have been used for computation of seismic demands. Provisions and specifications recommend the use of combination rules for computation of displacements and elastic forces, but they do not clearly suggest any combination rules for nonlinear time history analysis of bridges. This paper evaluates the