To investigate the flexural performance of carbon fiber-reinforced polymer/plastic (CFRP) reinforced concrete encased steel composite beams, three steel reinforced concrete composite beams with CFRP bars were designed in this study. The comparison parameters included the main tensile bars with different elastic moduli and reinforcement ratios of the CFRP bars. The variation trends of the strain, deflection, crack development, and flexural bearing capacity of the steel-reinforced concrete composite beams with increasing load were determined through a static load test. The results indicate that the slip between the I-beam and concrete increases with the increase in load, leading to the non-conformance of the strain of the steel-reinforced concrete composite beam along the beam height direction with the plane section assumption. The flexural rigidity, crack resistance, and energy dissipation capacity of the test specimens can be improved by increasing the elastic moduli of the main reinforcement. The strength of the steel-reinforced concrete composite beams with CFRP bars following the yielding of the lower flange of the I-beam is greater than that of ordinary steel reinforced steel composite beams with the same flexural capacity, and the energy dissipation capacity is greater by 1.36 times. When the contact area between the main tensile reinforcement and concrete is maintained constant, increasing the reinforcement ratio of the composite beams can delay the crack development of the steel-reinforced concrete composite beams with CFRP bars, thereby improving the overall flexural performance and energy dissipation capacity of the composite beams. Based on the pure bending calculation theory of the beams, the cracking moment formula was derived, and the cracking moment influence coefficient was introduced to modify the calculation formula. The cracking moment influence coefficient of the ordinary steel-reinforced concrete composite beams is 0.73, and that of the CFRP-reinforced steel reinforced concrete composite beams is 0.43. Combined with the test in this study, the calculation results of the ultimate bearing capacity of the steel reinforced concrete composite beams according to domestic and foreign codes were compared and studied. The results indicate that the calculation results of the technical specifications for the steel reinforced concrete structures (YB 9082-2006), the code for the design of composite structures (JGJ 138-2016), and the American Code guide for the design and construction of concrete reinforced with FRP bars (ACI-440-1R) are smaller than the test results. However, the calculated values from the design guidelines for reinforced concrete structures (CH 3-78) and design principles of steel-concrete composite beams are in good agreement with the experimental values. Thus, the study findings provide a reference for the design and specification compilation of the same type of steel-reinforced concrete composite beams. © 2022, Editorial Department of China Journal of Highway and Transport. All right reserved.
