Flexural Ductility of High-Strength Concrete Members

Advances in concrete technology in many countries have now made the practical use of concrete with strengths 100 Mpa a possibility. HSC, due to its very high compressive strength, is less ductile and as such creates a less ductile response in the structural members. The current practice of structural member design recommends low tension steel ratio in order to ensure adequate ductility of the construction structure so that the necessary warning can be given prior to the failure of the member. Especially, the ductile failure mode is essential for the appropriate redistribution of the moment of earthquake-proof and statistically indeterminate structures. Ductility is an important parameter in the RC beams for proper redistribution of moments. In seismic areas, ductility is an important factor in the design of HSC members under flexure. HSC due to its very high compressive strength is less ductile and as such creates a less ductility response in the structural members. The investigation is carried out to understand the ductility behaviour of balanced and doubly reinforced beams. To understand the effect of tensile, compression reinforcement ratio and compressive strength of concrete and also the effect of (L/d) ratio on the ductility of balanced and doubly reinforced HSC beams. To understand the response of HSC beams in flexure with compression reinforcement, nine beams were tested. Three beams of M100 balanced section and six beams of M100 doubly reinforced with varying amount of longitudinal compression reinforcement were tested. The beams are of rectangular cross section with dimensions 100mm X 170mm and overall length of 2000mm, 2600mm, and 3200mm with an effective length of 1800mm, 2400mm, and 3000mm so that l/d ration is 15, 20 and 25. The ductility index is calculated using Bilinear method for all the analysed beams