Destructive testing and computer modeling of a scale prestressed concrete I-girder bridge

•Construction and testing of a scale prestressed concrete bridge is described.•The bridge was modelled as a grillage, 2D FEM, and 3D FEM.•The failure mode of the bridge indicated some two-way bending.•The diaphragms provided load transfer during failure.•A 2D FEM balanced model simplicity and accuracy in predicting shear distribution factors. Currently, there is a limited amount of published information on failures of prestressed concrete bridges subjected to shear and moment. A scale prestressed concrete bridge was constructed to investigate the ultimate behavior of the bridge with particular focus on load distribution after cracking and on contribution of full-depth diaphragms to structural capacity. A point load was applied at the quarter-span point of the bridge over an interior girder. As the loaded girder failed, the diaphragm-girder connection cracked. Torsion was observed to cause cracking in the exterior girder and the end diaphragm rotated away from the bridge as the deck deformed. A punching shear failure ended the test, however damage indicative of two-way slab behavior was observed in the deck. This failure suggests that post girder failure, the diaphragms provide an important means of load transfer, allowing moment redistribution in the deck and potentially increasing capacity. Testing in the elastic range compared favorably with respect to deflections and shear distribution factors from a grillage model, a 2-D finite element model and a 3-D finite element model.