Abstract:

Bridges are built in a variety of locations, many of which are susceptible to multiple extreme hazards. New York City and South Carolina, for example, are regions susceptible to hurricanes and earthquakes, and bridges in all regions are susceptible to vehicle collisions and blasts. This exposure and vulnerability to multiple hazards underscores the need to develop an innovative design concept for bridges from a multi-hazard perspective, which is the objective of this research. Given that damage to bridge piers could lead to closure or, in extreme instances, to collapse of bridges, the focus of this research was on ductile and redundant pier systems. Accordingly, a bridge pier system incorporating the favorable qualities of steel plate shear walls (SPSWs) (e.g. ductility, redundancy, and ease of repair) capable of resisting multiple extreme hazards was sought.

This research considered four extreme hazards, namely, earthquakes, vehicle collisions, tsunamis (and indirectly storm surge), and blasts. A search for an integrative pier concept that simultaneously considered the constraints and demands germane to each hazard was conducted, resulting in a SPSW box pier concept. Through means of simplified analysis and design approaches, a detailed design of this concept was achieved, which was then analyzed for the demands of each hazard to investigate the system's anticipated global behavior and resistance to each hazard. For a better understanding of the system's behavior in resisting the hazards, nonlinear finite element analyses were conducted.

The proposed system was found to have adequate ductile performance and strength for each of the hazards. Investigation with finite element analyses demonstrated the system to behave as expected (based on simplified analysis) in resisting the seismic hazard. In resisting the collision hazard, the plates, which were conservatively neglected in the simplified analysis, were found to mitigate global deformation in the pier by developing tension field action. Moreover, the pier was observed to have significant capacity against the imposed tsunami demands, where the pier's plates were considered sacrificial, and where the pier's vertical boundary elements (VBEs) remained essentially elastic. Barring local failure, the VBEs were also observed to have significant deformation capacity for resisting the blast hazard, applied with statically distributed loads.