Shear-friction theory applied to steel fibre reinforced concrete and push-off tests

Abstract

Steel fibre reinforced concrete (SFRC) may be adopted for structural design when it meets the conditions established by structural concrete regulations. These conditions are based on residual strength values obtained by three-or four-point bending tests in order to obtain residual flexural tensile strengths. However, the strengths obtained may not be suitable when subjected to other loading conditions such as shear. To study the shear behaviour of SFRC, two main types of studies have been carried out, according to published literature: by bending and shear beams and by direct shear tests. These research studies have provided relevant data such as the possible reduction or even elimination of traditional stirrups by using structural fibres. Despite the studies developed, the study of the resistant mechanisms of aggregate interlock and dowel action according to shear-friction theory remains a field of research for SFRC. It should be noted that fibres improve the behaviour of the material as they prevent the collapse of the concrete element by bridging the cracks. On this scientific basis, a study on SFRC was carried out to obtain the relative displacements between the sides of the cracks on push-off specimens. In order to correlate them with the Walraven’s shear-friction model, video-extensometry system was used. A high degree of agreement was observed when the experimental results were compared with the kinematics of the shear discontinuity proposed by the shear-friction analytical model adapted to SFRC. © Fédération Internationale du Béton (fib) – International Federation for Structural Concrete.