Mechanical Properties of Steel-FRP Composite Bar under Uniaxial and Cyclic Tensile Loads

This paper introduces a newly developed steel-fiber-reinforced polymer (FRP) composite bar (SFCB) and proposes the ideal configuration based on a large number of exploratory tests on handmade products. Based on factory production of SFCB, uniaxial tensile tests and cyclic tensile tests were conducted to determine the initial elastic modulus, postyield stiffness, yield strength, ultimate strength, unloading stiffness, and residual deformation. Test results showed that the stress-strain curve of the SFCB was bilinear before the fiber fractures. After the inner steel yielded, the SFCB showed a stable postyield stiffness, small residual deformation, and good reparability. Because the theoretical model for the stress-strain curve of SFCB under a uniaxial load based on the mixture rule had large error with data from cyclic tests, the corresponding restoring force model under cyclic tensile loading was constructed by statistical analysis of the stress-strain test curve under cyclic tension. The generated restoring force model accurately displayed the trend of unloading stiffness of SFCB degradation with cyclic loads. Furthermore, the predicted results were in good agreement with the experimental results, which proved that the mechanical properties of SFCB could be predicted and designed by the proposed model.