WEB CRUSHING CAPACITY OF HOLLOW RECTANGULAR BRIDGE PIERS

This paper outlines an approach to assessing the horizontal shear capacity of the hollow rectangular bridge piers designed to support three new toll bridges in the San Francisco Bay Area under seismic loads. The approach focuses on the piers' capacity in diagonal compression, or their "web crushing capacity," as it relates to the fanning crack pattern inside the plastic hinge region. In contrast to existing web crushing models that assume a uniform distribution of shear stresses across an effective section, this approach assesses the capacity of and demand on individual struts inside the plastic hinge region as the plasticity spreads up the height of the pier. Analytical results based on this flexure-shear approach to web crushing are compared to results from 12 large-scale tests conducted by the authors at the University of California, San Diego between 1999 and 2001 and by Oesterle et al. at the Portland Cement Association between 1976 and 1983.