Experimental study on the bending performance of a precast, pretensioned high-strength concrete I-girder with pretensioned double broken strands.

Precast, pretensioned concrete girders are extensively used in bridge engineering to prevent damage to concrete girders, such as the loss of prestress and the corrosion of strands. Existing studies of the mechanical performance and failure characteristics of bridge girders had shortcomings, resulting in potential safety hazards. This study conducted a full-scale model experiment and theoretical analysis of the bending performance of a 35-m long precast, pretensioned concrete I-girder with pretensioned double broken strands. The cracks and bending damage were investigated. The results showed that the maximum vertical displacement of the composite girder was much lower than the required standard value, with a crack factor and bearing capacity factor of 1.31 and 1.54, respectively. The bending stiffness of the composite girder decreased by 70%. Many cracks occurred in the concrete, resulting in excess stress of the steel bars and prestressed strands. The crack width during loading was much smaller than the theoretical one in the Specifications for Highway Reinforced Concrete Prestressed Concrete Bridge Culverts (JTG 3362-2018). Therefore, the girder exhibited optimum bending stiffness, sufficient crack resistance, acceptable ultimate bending capacity, and ductile failure performance. The mechanical behavior and failure mechanism during loading were investigated. This study provides recommendations for the design, maintenance, and damage assessment of this bridge type to improve the service lives of bridges.