Direct displacement-based design of skewed bridge isolated with LRBs

Skewed bridges often exhibit a complicated seismic response and are at a high risk of damage under strong earthquakes due to their irregular geometry. Specifically, when the substructures of a skewed bridge are bridge bents, the effective stiffness of the bridge bents in the longitudinal and transverse directions of the skewed bridge will change with the skew angle. This study proposed a direct displacement-based design method for skewed bridges supported by bridge bents and isolated with lead rubber bearings. First, double-column bents were taken as an example, and a method for calculating the effective stiffness of the double-column bents in the longitudinal and transverse directions of skewed bridges with various skew angles was developed. Afterward, the displacements were allocated to the piers and bearings based on the mechanical properties of the pier (abutment)-bearing series system. Thereafter, considering the pounding-induced displacement increment in the main girder, a displacement amplification factor was introduced to modify the design result. Finally, the limit state of the bearings was examined. The proposed method was applied in the design of five cases: a four-span highway skewed continuous girder bridge with skew angles of 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 60 degrees. To validate the feasibility of the proposed method, nonlinear time-history analyses were performed on these five cases under a group of near-fault pulse-type ground motions. The results of the nonlinear time-history analyses of these five cases were compared with the design results, which indicated that the proposed method is conservative and feasible.