Experimental investigation on the flexural behavior of concrete beams reinforced with HRB635 high-strength steel reinforcement

High-strength steel reinforcement offers promising application prospects in buildings with large spans and loads, as it can reduce steel congestion and simplify construction process. To investigate the mechanical behavior of flexural members reinforced with high-strength steel and measures to control crack width, in this study, static loading tests were conducted on 17 full-scale reinforced concrete (RC) beams with HRB635 high-strength steel reinforcement, six of which were reinforced with steel fiber. The failure mode, flexural strength, ductility, crack width, and deflection of the specimens were investigated, and the effects of different key parameters, including the reinforcement ratio and diameter, concrete strength, and steel fiber volume fraction were also analyzed. Test results indicated that the tensile strength of HRB635 reinforcement could be fully utilized, while the ductility ratios of high-strength steel reinforced concrete (HSS-RC) beams were less than those of beams with normal strength reinforcement. The maximum crack widths of most specimens without steel fibers exceeded the threshold defined in GB 50010-2010, indicating that the design of HSS-RC beams may be controlled by the requirements of serviceability limit state. Furthermore, the crack widths predicting methods defined in GB 50010-2010 and EN 1992-1-1 are more accurate for HSS-RC beams, while the deflection predicting methods defined in GB 50010-2010 and ACI 318-19 both underestimated the deflection of HSS-RC beams. This study could provide a theoretical basis for the engineering application of HRB635 high-strength steel reinforcement.