Influence of span to depth ratio (l/d) on strength, deformation and ductility behavior of high strength concrete beams

High Strength Concrete (HSC) is being produced using the local available materials with the addition of mineral and chemical admixtures. The change in the micro mechanism of HSC changes its mechanical properties. This change in the mechanical properties of HSC compared over the NSC becomes a key parameter for the change in behaviour of structural members. The existing stress strain models and the codal provisions, which are applicable to NSC, cannot be simply extended in understanding the behaviour of HSC beams. Therefore understanding of the strength, deformation and ductility behaviour of HSC beams in flexure is more important before it is put into practice. In most of the literature it has been observed that beams with span by depth ratios of 9, 10 and 12 were tested. With these span by depth ratios full potential of HSC beams is not reflected in the flexural behaviour. Therefore there is a need for the research in understanding the flexural behaviour of HSC beams with span by depth ratios 16 and 20. An experimental investigation was carried out using M100 concrete. A total of eight HSC beams were tested, four in each series with reinforcement ratio (rho = 1.0) and (rho = 2.4) respectively with span to depth ratio 9, 12, 16 and 20. It was observed, from the experimental investigations that parameter (rho/rho(b)), grade of concrete (f(1)c) and span to depth (l/d) ratio becomes dominant factor in the strength, deformation and ductility behaviour of HSC flexural members.