Abstract:In order to reveal the multi action composite working mechanism of HB FRP(hybrid bonded fiber reinforced polymer)to concrete structures, five sets of tests considering different bond combinations were designed. The characteristics of the composite interface were studied based on measured load slip relationship, strain distribution and bond slip relationship. A unified bond slip model for composite interface and bond load expression were proposed. The results show that the HB FRP reinforced concrete composite interface can be divided into FRP bonded concrete, pressure and FRP bonded steel plate. The development of bond stress in the composite interface is not synchronized, the debonding of FRP to concrete is prior to FRP to steel plate, the superimposed working order is different. The interfacial friction stress caused by lateral pressure increases with the development of interfacial stress and tends to be stable. The theoretical model results are in good agreement with the experimental results and can be used to calculate the bonding load of the composite interface.