Analysis of the flexural performance of Precast Box Girders Reinforced with a combination of Steel-Slab-Concrete Plus Unbonded Prestressing

Due to the serious development of cracks in precast box girders, there is no reliable method to detect the loss of prestress and carry out effective reinforcement of box girders. This paper proposes a reinforcement method of steel plate - concrete with unbonded prestressing, and applies this method to a 30m reinforced concrete prestressed box girder bridge. This paper uses FEA software to carry out a comparative analysis of the load-deflection curve of the reinforced mid-span section by comparing with the conventional bonded steel reinforcement method and the load test data, and through the analysis results, the calculation formula of the flexural load capacity of the steel plate-concrete with unbonded prestressing reinforcement method is derived. The results show that the flexural load carrying capacity of the strengthened mid-span section is significantly improved, and the proposed calculation formulae deviate from the finite element simulation results within 5%, which can be applied to actual projects