Effect of shear keys on seismic response of irregular bridge configurations

Shear keys play an important role in constraining the relative transverse movement between the deck of a bridge and its abutments. Shear keys are normally regarded as secondary components, and their influences on bridge seismic responses are generally neglected. However, the seismic demands and structural response of bridges can be significantly affected by shear keys. This paper assesses and compares the seismic response of various regular and irregular bridge configurations and geometry with and without shear keys. Two different capacities of shear keys (25% and 75% of the abutment lateral pile capacity) are considered and seismic demands are evaluated under weak, moderate, and severe ground motion intensity levels. The following bridge configurations are considered: straight single-frame bridge, skewed single-frame bridge, skewed multiframe bridge with equal and unequal pier heights, and curved multiframe bridge with equal and unequal pier heights. Nonlinear time history analysis (NTHA) was conducted on a three-dimensional finite element model of each prototype bridge by using the Open System for Earthquake Engineering Simulation, or OpenSees, program. NTHA results showed that shear keys were effective in reducing seismic demands; that the effect of shear keys was dependent on the bridge configuration but could significantly affect the response of irregular bridges, especially in the longitudinal direction; and that the shear keys played an important role in controlling the overall bridge behavior, especially in cases of moderate-intensity ground motions rather than in weak-and strong-intensity cases.