Shear behavior of pre-damaged RC beams strengthened with steel plate and UHPC

To address the deficiencies in the durability of the bonded connection, an innovative strengthening method combining steel plates with UHPC (ultra-high-performance concrete) is proposed. In this method, the UHPC layer is located between the steel plate and the original damaged RC (reinforced concrete) structures, mainly acting as a binder to enhance the bonding effect. To verify the effectiveness of the proposed method, five RC beams are manufactured and carried out to investigate the shear characteristics and capacity. In this experiment, some factors that may affect the strengthening effect are considered, such as the initial damage degree (represented by different crack widths), steel plate thickness, and strengthening method (two-side or one-side). The experiment results show that the proposed strengthening method can significantly improve the shear capacity (increased by at least 56%) of pre-damaged RC beams without significantly enlarging the cross-section and self-weight. In addition, during the load test, there is no peeling phenomenon for the steel plate-UHPC interface and the UHPC-RC interface. This demonstrates that it is feasible for the UHPC layer to replace epoxy resin glue as a bonding agent to enhance the bonding effect between steel plate and RC. The proposed strengthening method shows promising applications in strengthening old/defective bridges. Moreover, a simple formula for predicting the shear-bearing capacity of strengthened beams is derived. The shear-bearing capacity predicted by the proposed formula is in good agreement with the experimental results.