Fibre reinforced concrete under in-plane shear stresses

Abstract

Steel fibres have a positive influence on the shear behaviour of concrete elements, such as beams and walls, the more so as the developments in fibre reinforced concrete (FRC) technology allow reaching increasingly higher residual post-cracking strengths. The partial, or total, replacement of shear reinforcement by steel fibres allows increasing the construction speed and reducing labour costs, potentially offering economic benefits in the context of industrialized fabrication. However, the combined behaviour of steel fibres with reinforcement in shear critical elements is still not fully understood hindering the development of consistent design procedures.In this study, a detailed mechanical model based on the Cracked Membrane Model using fixed and interlocked cracks (F-CMM) is presented, which is capable of describing the behaviour up to failure of concrete panels reinforced with both steel fibres and rebars (R-FRC) subjected to in-plane shear and axial forces. The model explicitly considers all the individual mechanical phenomena governing shear behaviour of R-FRC and can serve as the basis for the development of methodologies for shear safety verifications.The model is validated against the existing experimental results from R-FRC panels subjected to in-plane shear loading. A calculation example is used to discuss in detail the model outcomes and the impact of the spatial variability in the fibre distribution. A parametric study is developed to understand the effects of fibres on the shear strength and failure modes, and its interactions with both the reinforcements and crack shear stress transfer mechanics.