Steel fibrous RC beams subjected to cyclic deformations under predominant shear

Abstract

The influence of steel fibres in shear-critical reinforced concrete beams subjected to monotonic and cyclic loading is experimentally investigated. Seven short beams with shear span to effective depth ratio equal to 2 were constructed by steel fibrous concrete and by plain concrete as reference specimens. Hook-ended steel fibres with an aspect ratio equal to 75 and using two different volume fractions (0.5% and 0.75%) have been added in the fibrous concrete beams as shear reinforcement. Supplementary compression and direct tension tests have also been performed to determine the compressive and the tensile behaviour of the used concrete mixtures. Experimental results concerning the hysteretic response, the shear strength at cracking and at ultimate, the energy dissipation capabilities, the cracking patterns and the failure mode of the tested beams are presented and discussed. The application of steel fibres as the only shear reinforcement is also reported, in an attempt to examine the effectiveness of fibres as a potential replacement of stirrups. Analytical model of the tensional behaviour of the steel fibrous concrete, calculations of the shear stresses at the first flexural cracking, at the onset of the shear cracking and at the maximum shear capacity, along with the predictions of the potential failure mode of the beams are also included. Research results indicate that the steel fibrous beams exhibited improved shear performance with higher shear strengths, enhanced absorbed energy capabilities and ameliorated crack patterns with respect to the non-fibrous reference specimens. Further, an attempt to estimate a minimum value for the fibre factor of the steel fibres in order to alter the brittle shear failure to a ductile one is also demonstrated. This effort is based on the test data of 51 beams from the present study and the literature.