Shear strength of composite beams with steel fiber-reinforced concrete

Composite beams of normal-strength concrete (NSC) and steel fiber-reinforced high-strength concrete (SFRC) are frequently used for strengthening existing buildings and precast concrete constructions. In this study, shear strength of NSC-SFRC composite beams was investigated. Twelve simply supported SFRC composite beams were tested to investigate the effect of steel fibers on the shear strength of the composite members. Test variables included area ratio of SFRC to NSC and the use of minimum reinforcement for horizontal shear transfer in concrete interface. Test results showed that vertical shear strength of SFRC composite beams with shear reinforcement increased as the area ratio of SFRC increased. On the other hand, SFRC composite beams without shear reinforcement were susceptible to horizontal shear cracking at the interface, which indicates that minimum reinforcement for horizontal shear transfer was required for the monolithic behavior of NSC-SFRC composite beams. Based on these test results, design recommendations were given to reasonably predict the shear strength of SFRC composite beams.