Full-Scale Destructive Bridge Test Allows Prediction of Ultimate Capacity

Contemporary bridge design is generally based on designing individual members for the maximum force effect that each member may experience. This approach ignores the system-level interactions of these individual members, which may greatly increase the ultimate strength of the complete structure. In an attempt to understand better the load redistribution mechanisms that lead to this increase in ultimate strength, the destructive testing of a skewed steel I-girder bridge was planned and executed. However, because of the enormous system-level reserve capacity of the structure, the structure generally responded elastically, despite being loaded with the equivalent of 17 HS-20 design vehicles. Thus, a validated finite element analysis (FEA) approach was used to predict the ultimate capacity of this structure and to analyze the force redistribution as the bridge's elastic limit was exceeded. The FEA results predicted that the equivalent of 41 HS-20 vehicles was needed to plastify fully the four girders of the subject bridge and show the significant amount of yielding that occurs in the cross-frames when the ultimate capacity of the girders is achieved.