Performance of Composite Twin I-Girder Bridges with Fatigue-Induced Cracks

An experimental program was performed to investigate the postfracture performance of composite twin I-girder bridges in the fatigue crack condition. An intact specimen and a damaged specimen were tested under one-point load to understand the effect of fracture on the bridge response and safety. In addition, nonlinear numerical analyses were performed to study the mechanical behavior of the models. The results showed that the fracture of the entire web and bottom flange at the midspan section can result in a considerable increase in the shear strain on the studs near the middle section. The fracture of the bridge in the midspan section governed by bending failure is found to be most critical in terms of the remaining load-carrying capacity, and the fracture near the support location governed by shear failure is found to be brittle, which can result in a sudden collapse of the bridge system. The effects of the fatigue crack on the safety of the composite twin I-girder bridge can be mitigated by using a continuous span instead of a simply supported span or by using a stronger and thicker concrete slab. (C) 2017 American Society of Civil Engineers.