A NEW PERFORMANCE-BASED DESIGN FOR SPIRALS IN BRIDGE COLUMNS

摘要

Performance-based design (PBD) is beginning to receive attention from the earthquake engineering design profession because of the versatility it offers to owners. While PBD provides considerable flexibility, there is no available widely accepted single measure of performance that can specifically correlate to quantifiable structural parameters. Among the measures have been used by researchers and engineers including displacement ductility, drift ratio, curvature ductility, concrete strain, and steel strain. Curvature ductility is a measure of local deformation in plastic hinges, and can serve as an appropriate index to signify performance under moderate and strong earthquakes. A simple confinement steel design method for spiral bridge columns was developed that proportions the spirals depending on the target curvature ductility capacity. Two quarter-scale spiral columns were constructed and tested on one of the University of Nevada, Reno Shake tables. The confinement steel in one column was designed based on existing codes and in the other using the proposed PBD. The shake table test results showed the superior performance of the latter with respect to repairable damage under moderate earthquakes and higher ductility capacity under strong earthquakes.