Seismic Response of Sacrificial Exterior Shear Keys in Bridge Abutments

This report describes an experimental program which studied the seismic behavior of shear keys. Shear keys are used in bridge abutments, providing transverse support for the superstructure. In this project, specimens were built at a 40% scale of the exterior shear keys of a prototype abutment. The report presents recommendations for design and construction details of sacrificial exterior shear keys based on test results. The design philosophy involved forcing a shear sliding failure at the interface of the shear key-abutment stem wall in order to control damage to the abutment walls and the piles under transverse seismic force. A number of were considered in this experimental program, such as: 1) including construction joints between the abutment stem wall and the shear key; 2) different amounts and configurations of the vertical reinforcement crossing the abutment stem wall-shear key interface; and, 3)different amounts and configurations of the horizontal reinforcement in the stem wall. Five specimens were built and tested, with each specimen including two exterior shear key test units. Experimental results of two of the specimens are included in the report.