Abstract: In uniaxial tensile tests, steel fiber reinforced concrete (SFRC) manifests two tensile strength peaks in the stress-strain curves, a phenomenon already revealed in a number of observations and different from the plain concrete case of a single strength peak. This study considers the effect of fibers bridging a crack using the bond-slip model for the interaction between the fibers and matrix, and formulates a relationship of steel fiber reinforcement stress versus crack width. The sum of the softening modulus of the matrix and the reinforcement modulus of the fiber is used for judging the occurrence of the second peak. When the sum is always non-negative, the SFRC stress-strain curve has a unique stress peak; otherwise, this curve will have two tensile strength peaks. Hence, we suggest three peak strength cases for SFRC, construct a finite element model to simulate its tensile tests, and examine the effects of fiber contents and fiber aspect ratios on its mechanical properties under the occurrence of concrete cracking. A calculation formula for the tensile strength of SFRC is given, which shows effective predictions.

Key words: fiber reinforced concrete, bond-slip model, second peak strength, tensile strength