Effect of Abutment Shear Keys on the Seismic Response of Bridges

Seismic analysis results of typical post-tensioned concrete bridges are presented considering the nonlinear behavior of transverse abutment shear. Current Caltrans and AASHTO bridge design criteria present overly general assumptions for the boundary conditions provided by abutment shear keys. This work uses a suite of ground acceleration time histories to compare the code specified assumptions to a more rigorous abutment shear key model that includes the lateral gap between the superstructure and the keys as well as the non-linear material response of the key itself. With the exception of the abutment shear key elements, the bridges are modeled using linear-elastic frame elements, as is typical in practice. Results of a sensitivity analysis are presented for typical parameters, including: record variability, bridge skew, bridge length, and bent heights. The analysis results precede a discussion which demonstrates the necessity for experimental work on this topic to verify the adequacy of the existing design code.