Behaviour of curved reinforcement bars

Abstract

Bended or curved reinforcement bars are often met in assessment of existing reinforced concrete structures and are used in design of nodal regions such as frame corners. Although being present in many tested reinforced concrete structures, only little experimental work has been devoted specifically to the behaviour of curved bars and its interaction with the surrounding concrete. To contribute to a better understanding of this behaviour and functioning of curved reinforcement bars, a preliminary experimental programme has been conducted, the results of which are presented in this paper. The tested specimens were all 90-degree V-shaped beams subjected to constant bending, with the frame corner representing the region of interest. The varied parameter was the statical-height of the adjoining beam segments. The application of optical fibres, mounted on the curved reinforcement, allowed for assessment of the interaction between the curved bars and the concrete. This includes strain/stress variations from which the corresponding tension forces are estimated. The bar/concrete-interaction is qualitatively assessed based upon the gradient of the tension force. Photogrammetric measurements allowed for a detailed study of the accompanying crack development, which showed an area with few cracks at the corner region and a change in inclination of cracks near the corner region.