Shear response of lightweight steel fiber reinforced concrete members without stirrups

Available studies on the shear strength of lightweight steel fiber reinforced concrete (SFRC) members without stirrups are scarce. Meanwhile, the overall depth of reported specimens in these prior studies did not exceed h = 300 mm, preventing verification of a so-called size effect in shear for lightweight SFRC. In this paper, the laboratory results of six large-scale lightweight SFRC specimens without stirrups having overall heights from 308 to 1,000 mm and shear span to effective depth ratios of 3.0 are reported. The specimens contained 1 % volume-fraction of hooked-end steel fibers and different longitudinal reinforcement ratios. It was observed that the normalized shear stress at failure decreases with an increase in the member depth. This indicates that a size effect in shear is present for lightweight SFRC members without stirrups. Nevertheless, for all specimens, the observed shear capacities were higher than the shear strengths predicted by the ACI 318-11 and CSA A23.3-04 standards for geometrically similar reinforced lightweight plain concrete members. The fib MC2010 models for lightweight SFRC gave more accurate predictions of strength compared to the ACI 318-11 and CSA A23.3-04 models for lightweight RC members without steel fibers.