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Design of slabs without shear reinforcement is, in practice, based mainly on empirical codified methods, derived on the basis of a large number of tests. However, the vast majority of these tests involves simply supported beams, with substantial amounts of longitudinal reinforcement, subjected to three- or four point bending. This paper presents the results of a significant experimental programme comprising eighteen simply supported - cantilevered slabstrips without stirrup reinforcement, and with a light amount of longitudinal reinforcement. Stirrups in the surrounding parts founded a shear critical region located in the hogging region of the simple span. All beams failed in shear within this shear critical region, the slenderness of which was fixed for all the beams. The influence of the concrete strength, which is of special interest in relation to lightly reinforced members, was investigated by varying the concrete strength systematically within the test series. The influence of the concrete strength and mix with respect to crack roughness was further studied using a large number of concrete cores prepared with coloured epoxy. The cores were all extracted from various zones containing critical and "non-critical" shear cracks. Photogrammetric measurements (digital image correlation) and optical fiber measurements were conducted in the shear critical region on all tested specimens, and detailed analysis on the propagation and kinematics of critical cracks are presented. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]