Behavior of steel girder bridges damaged by vehicular collision

Abstract

Vehicles often collide with girders of low-clearance bridges, yet there is a knowledge gap in understanding the behavior of damaged steel girders. This paper addresses this gap by performing non-destructive field testing on four damaged steel girder bridges. The focus is on two- and three-span continuous multi-girder steel bridges for which an exterior girder has sustained Category T damage, i.e., torsion about the longitudinal direction. The behavior of damaged girders, symmetric undamaged girders, and adjacent girders under quasi-static truck loading is monitored using digital image correlation (DIC). Specifically, the measured strains of damaged girders are compared to the strains of corresponding symmetric undamaged girders to investigate the effect of the damage on behavior for each bridge. Strain gauges were used to monitor the behavior of one bridge under quasi-static truck loading, as well as speed and crawl tests. The strain gauge readings are also used to validate DIC strain measurements for field monitoring of bridges. The measured strains are used to validate finite element (FE) numerical models. A parametric study investigates the effect of varying shapes and locations of damage on the load-deflection behavior of a single girder as well as two- and three-span continuous bridges. Overall, this study found that measured strains in all girders are less than 200 microstrain or approximately 40.0 MPa (5.80 ksi). Results indicate that vehicular damage may affect composite behavior, bridge railings participate in carrying live load, damaged girders may have increased live load amplification factors, and damage at the center of a span with a large rotation angle of the web results in the greatest loss of stiffness.