Effect of Test Setups on the Shear Transfer Capacity Across Cracks in FRC

Abstract

The shear transfer capacity of concrete across cracks is highly relevant in situations where the principal concrete stress directions are not aligned with the cracks. Fibres are effective in controlling the crack opening, thereby enhancing aggregate interlock and hence, the ability of transferring shear stresses across cracks. Compared to plain concrete, higher stresses can therefore be transferred across cracks in fibre reinforced concrete (FRC). However, the shear transfer across cracks in FRC has received much less attention over the past decades than the residual tensile stress transfer across orthogonally opening cracks, and no generally accepted model for this behaviour is available today. The shear transfer capacity and the calibration of most existing models are obtained from experimental tests which presume failures occurring in “pure shear”, being the most popular used test setups: (i) Z-type push-off specimen; (ii) modified JSCE-G 553; and (iii) FIP shear test method (asymmetrical four-point bending). However, significant differenced have been observed in the experimental resulting shear strength, depending on the test setup. These differences have not been evaluated systematically until now. In order to address this issue, the authors carried out an experimental campaign on specimens made from identical SFRC mixes with varying fibre dosage, testing each mix in all three mentioned setups. The paper presents the results of this experimental campaign.