Performance-Based Seismic Assessment and Design of Long-Span Concrete Deck Arch Bridges

Abstract

This study explored extending the performance-based seismic design method to three case study arch bridges with geometry and loading conditions representative of the long-span concrete deck arch bridge class. The force-based design method was first utilized to develop preliminary seismic designs of the three bridges and validate the assumption that bridges designed following the force-based design are protected against collapse under rare seismic events. The preliminary designs of the short spandrel columns failed to achieve code-specified performance objectives under longitudinal seismic loads and were thus revised. The three bridges with the revised details were analyzed using nonlinear time history analysis considering three suites of ground motions scaled to the code-specified hazard levels at the site of interest. The three suites of ground motions represented crustal, subcrustal, and subduction earthquakes. Under individual records associated with the subduction earthquakes, the revised designs of two bridges failed to achieve the code-specified performance objectives. Seismic fragility curves were generated for the bridges considering details based on force-based and performance-based design methods. The probabilities of the collapse of bridges designed following the force-based design method were near zero under rare events. The assumption that bridges designed following the force-based design method meet the collapse prevention limit state was thus found to hold true when extended to the special case of long-span concrete deck arch bridges. Such bridges, however, were found to be unlikely to meet low to intermediate levels of damage and performance criteria corresponding to low to moderate levels of seismicity. Despite being designed to achieve code-specified performance objectives, performance-based designed piers were also characterized by some probability of not meeting the damage levels and performance criteria, albeit to a much lesser extent than force-based designed piers. Considering demands associated with individual records with particular emphasis on those representatives of the dominating seismic hazard at the site of interest is thus recommended for performance evaluation of long-span concrete deck arch bridges.