Evaluation of shear performance of steel fibre reinforced concrete beams using a modified smeared-truss model

Numerous experimental and analytical investigations have been conducted on the shear strength of steel fibre reinforced concrete (SFRC) members. However, most existing strength evaluation models are empirical equations based on limited experimental results lacking in theoretical basis, and these models may lead to overly conservative, uneconomical designs owing to the assumption of 458 crack inclination. They also cannot be expanded to estimate load-deformation responses of SFRC members. In order to overcome these limitations in existing models, this study proposes a theoretical model in which the contribution of steel fibres to shear resistance mechanisms of SFRC members, considering the random distribution characteristics and directionality of fibres at the crack interfaces, is reflected in a smeared-truss model. In particular, the pull-out failure of fibres caused by bond failure between fibres and the surrounding concrete is considered. Shear tests on SFRC beams were also conducted in this study with the primary parameters of fibre volume fraction and compressive strength, and experimental results from the literature were used for validation purpose. The proposed model shows a high level of accuracy in strength evaluation for a total of 103 experimental results. The crack inclination angles estimated by the proposed model range from 228 to 308 and agree well with the experimental results of this work. This demonstrates that the 458 crack angle assumed in the existing shear strength evaluation models is unnecessarily conservative.