Concept and flexural performance of non-prestressed steel plate-UHPC-NC composite girder bridge

A novel non-prestressed composite girder bridge, incorporating steel plates, ultra-high performance concrete (UHPC), and normal concrete (NC), is proposed for small and medium-span bridges. For the proposed steel plate-UHPC-NC composite bridge, UHPC girders are reinforced with steel plates on the bottom in lieu of part of closely-spaced rebars in the beam. Cast-in-situ NC deck slab is adopted to ensure its transverse integrity and to reduce costs in comparison with UHPC bridge deck. To verify the performance of the proposed novel composite bridge, three types of UHPC-NC composite beams with same reinforcement ratio (reinforced with only rebars, only steel plates, both rebars and steel plates) were first conducted with bending test. The impact of various reinforcement types on the flexural behaviors of UHPC-NC composite specimens was identified, including failure mode, crack distribution pattern, and crack width development. The findings demonstrated that the UHPC girder reinforced with both steel plates and rebars would significantly enhance the crack resistance of UHPC girders during bending in comparison with the other two. In addition, the composite girder reinforced with steel plates and rebars can achieve a nominal stress of 31.41 MPa at the serviceability limit state (with a UHPC crack width of 0.05 mm). The commercial software DIANA is then utilized to numerically simulate the mechanical properties of the proposed composite beam. The deviation between the finite element (FE) results and the experimental load-bearing capacity is within 1.9 %. Parameter analysis demonstrates that the bridge deck's strength has negligible influence on the load-carrying capacity of the proposed composite beam. Finally, a design scenario for a 30 m-span simple-supported bridge is conducted, and the initial cost analysis indicates that the proposed steel plate-UHPC-NC composite girder is 2 % lower than the conventional prestressed concrete T-girder. The proposed non-prestressed steel plate-UHPC-NC bridge presents notable benefits, including cost-effectiveness, strong crack resistance, and the prospect of complete prefabrication, offering a feasible alternative for small and medium-span bridges.