Abstract: The purpose of this paper is to establish a mechanical model that can predict the width of crack opening in steel fiber reinforced concrete (SFRC) beams with longitudinal steel bar reinforcement (R-SFRC) under loading. We develop a tensile stress-crack width constitutive model of SFRC beams considering the effective width of cracks and the effective pull-out angle of steel fibers, and then a SFRC flexural strength model based on fracture mechanics. And we formulate a calculation model that, taking the effect of reinforcement into account, can be used to analyze the bending moments and crack widths of R-SFRC beams and simulate their bending failure process. This calculation model, along with the standard methods of CECS 38—2004 and RILEM TC 162-TDF, is used to calculate the crack width of the collected 12 R-SFRC beams at service loads. The results demonstrate that the calculation results of the two standard methods are conservative and discrete, while our method gives predictions in a good agreement with experimental measurements and can effectively predict the crack width of R-SFRC beams and its variation over the loading process with a good accuracy and small coefficients of variations.

Key words: steel fiber reinforced concrete beam, flexural strength, crack opening, fracture mechanics, theoretical analysis