Fibre Bragg grating sensor investigation on bond stress of steel-carbon fibre reinforced concrete

Understanding the bonding stress distribution and reinforcement strain distribution between steel and carbon-fibre-reinforced polymer composite bars and concrete is essential to the design of concrete reinforced with such bars. Currently, the bond stress and reinforcement strain distribution patterns are not clear. Therefore, a series of pull-out tests was undertaken on concrete reinforced with steel and carbon-fibre-reinforced polymer composite bars, carbon-fibre-reinforced polymer bars and steel bars. With the help of fibre Bragg grating sensing technology, the reinforcement strain and bonding stress distribution were studied. The results showed that, for all specimens, the bond stress between the reinforcement and concrete was neither uniformly distributed nor reduced linearly along the bond length. For the steel and fibre-reinforced polymer composite reinforcement, the steel core strain value was less than the carbon fibre strain value at the same position. Based on the test results, a bonding stress model and bond stress distribution model were established. The two models agreed well with the test data and can be used to predict bond stress and bond stress distribution.