Experimental investigation on strain distribution in reinforcement of RC specimens under tension loading

Abstract

The interaction of reinforcement and the surrounding concrete is fundamental to the understanding of the behaviour of reinforced concrete. There are a number of aspects to this problem which include an understanding of bond behaviour, cracking behaviour and the related problem of tension stiffening. The phenomenon of cracking and the structural behaviour of cracked reinforced concrete are topics of current investigation. This paper presents the use of a Fibre Bragg Grating optical system for measuring steel strains, bond stress and slip of a reinforcing bar relative to its surrounding concrete, between cracks. Tests were performed on concrete prisms of 260 mm length. Specimens were reinforced with 10 and 20 mm diameter ribbed bars. The bars had been instrumented along the edge to accommodate a longitudinal narrow groove in which two arrays of FBG sensors were installed. The obtained strain profiles of the specimens for various loading levels are presented. A brief description is given a newly proposed method to determine the mean crack spacing of RC ties. The experiments serve in part as a way to validate key assumptions of the proposed approach and in part as a way to test the Fibre Brag Grating optical sensing system for strain measurement.