Interfacial stresses of beams hybrid strengthened by steel plate with outside taper and FRP pocket

This study proposes a new hybrid strengthening method, for which the reinforced concrete (RC) beams are strengthened in flexure by externally bonding a steel plate with variable thickness and an FRP pocket with end-anchorage. To investigate the influence of the stress distribution along the bondline on the strengthening effect, this paper develops an interfacial stress analysis model for RC beams strengthened with the proposed method under arbitrary loads. Based on the assumptions of linear elasticity, deformation coordination and static equilibrium conditions, the expressions of normal and shear stresses at the steel-concrete and FRP-steel interfaces of the strengthened RC beams under different loads and boundary conditions are derived. Finally, fourpoint bending tests on RC beams strengthened in flexure by using the proposed method were carried out. The steel plate with a fillet is beneficial to prevent the end debonding since it can significantly reduce the interfacial stresses at the end of the steel plate. Also, the results show good agreement between the calculated and tested results, which verified the applicability of the proposed model.