Contributing factors to seismic force demand on in-span shear keys in multi-frame bridges

Abstract

In-span hinge shear keys are critical to the transverse seismic performance of multi-frame bridges2. The demand parameters of in-span shear keys such as the bridge geometry, relative stiffness of adjacent frames, ground motion characteristics, transverse impact, and non-uniform base excitation on the seismic design force demands of the in-span shear keys are not well understood. To address this knowledge gap, a large number of straight non-skew prototype models were designed for different levels of seismicity and site class per the seismic design practice in California. These realistically designed models were analysed under a series of ground motions corresponding to the design spectrums, to estimate the in-span shear key force demands in relation with factors of interest. It was found that high-frequency modes of vibration may significantly contribute to the force demands. The relative location of in-span hinge to the stiffer frame on the shear key force is more effective than relative stiffness of adjacent frames. The current displacement-based analysis, such as pushover and elastic dynamic analysis, does not provide reliable results. The transverse impact and non-uniform base excitation significantly increase the shear key force. The findings may contribute to development of a reliable design guidelines for in-span shear keys through further research.