Experimental investigations on the crack development in reinforced concrete members subject to uniaxial tensile strain

Abstract To investigate crack development, in particular the evolution of crack widths and crack spacing during the crack formation and stabilized cracking stage, an experimental campaign on reinforced concrete slabs under uniaxial tensile loading was conducted. The specimens were, prior to the campaign, subjected to restraint‐induced stress for 7 days, which resulted in initial cracking. Without allowing a stress reduction, the uniaxial tensile deformation was directly applied, leading to the superposition of the induced stress field. This allowed for a realistic representation of an actual concrete member under increasing tension. Variations in concrete strength and stiffness, specimen height, bar diameter, and reinforcement ratio allowed for a comprehensive evaluation of the crack development in relation to the induced strain and the resulting reinforcement stress. Using the approaches in the final draft of the new Eurocode 2 and the fib Model Code 2020, respectively, as well as the German and Austrian National Annexes to Eurocode 2 to predict the mean and maximum crack width and spacing, the performance of these code provisions was assessed in regard to crack width limitation. It is shown that the provisions are able to adequately predict the crack width as well as the necessity of a reasonable assumption of the effective reinforcement area for thicker members.