Vulnerability Sensitivity of Curved Precast-Concrete I-Girder Bridges with Various Configurations Subjected to Multiple Ground Motions

Curved bridges provide a vital benefit to the nation’s infrastructure system by allowing for accessibility and ease of transition in irregular highway layouts. Curved bridges using straight prestressed concrete I-girders with curved decking can fulfill this need. A number of such bridges have been constructed both in seismically and nonseismically active zones. This paper determines the seismic vulnerability sensitivity of the bridges with vastly different configurations via use of conventional fragility-assessment techniques. Experimental design established a statistical setting using core variables to produce a wide variety of hypothetical bridges to represent both as-built and proposed bridge configurations. Each bridge was designed following the strength and serviceability limit states stipulated by current bridge design specifications. As part of the sensitivity analysis, nonlinear time history analyses (NLTHAs) using numerous synthetic ground motions were performed to establish seismic demands on critical bridge components. Using probabilistic seismic demand models (PSDMs), component and system-level fragility curves were generated. The resulting fragility data were scrutinized to explore the effects of the different design parameters on seismic vulnerability of the bridges. The results indicate that the shorter-span bridges with a tighter radius of curvature are less sensitive to seismic excitations than those with straighter decking, indicating that a span length-to-radius of curvature ratio (S/R) for both single and multispan bridges is statistically determined to be the most influential parameter.