Performance of Pipe Extender–Shear Key at In-Span Hinges of Multiframe Bridges

In multiframe bridges, shear keys are elements located at in-span hinges. They preserve the transverse integrity of adjacent frames during seismic events. In-span hinges must simultaneously accommodate longitudinal and transverse seismic deformations to prevent unseating and collapse. The California Department of Transportation has standardized a shear key detail known as the pipe extender–shear key (PE-SK). In some cases, cable restrainers pass through the PE-SK. This detail serves three functions: (a) it acts as a shear key for transverse motion, (b) it provides cable restraint to prevent unseating, and (c) it is a backup against unseating if the cables rupture. The transverse capacity and stiffness of this detail have not been fully investigated. In this paper, findings from finite element analyses performed to study the load–deformation behavior of the PE-SK with varying longitudinal gap sizes are discussed. A refined three-dimensional finite element model of the detail was developed with Abaqus. The model was validated by using data from previously conducted push-off experiments. The analyses demonstrated that (a) the pipe shear key detail is ductile under lateral loading and maintains its resistance under large transverse displacements, (b) the lateral capacity and stiffness of the pipe shear key vary with the size of the longitudinal gap, and (c) cyclic loading may significantly reduce the lateral stiffness of the element. Stresses and deformation in the concrete suggest that a steel collar may be useful in preventing concrete crushing at the contact surface. Tensile force in the cable restrainers has no effect on the transverse performance of the detail.