Behaviour of Reinforced Concrete Deep Beams

Abstract

As per IS 456:2000, beam with large depth in relation to span are called Deep Beam. They are useful in many structures i.e. tall buildings, foundations, offshore structures, water tanks, bunkers and several others. An attempt is made here to investigate the shear and flexure behaviour of deep beams having variable l/D ratio as well as addition of steel fibers. Literature suggests that less amount of experimental work is conducted on deep beams. Therefore, it is decided to study the behavior of such beams in details. The purpose of the investigation is to assess the behaviour of deep beam under variable L/D ratios, where the length and width are constant and only depth is varied to obtain the clear information regarding the shear distribution at mid span, which would provide deeper understanding of the fundamental nature of shear and flexure behavior during the cracking stage and deflection stage for deep beams. Steel fibers are added by about 1% of weight of concrete. The experimental investigation is carried out on total nine deep beams which are divided into two principle categories having with and without steel fibers. In categories-I five specimens are categories-II four specimens with various ℓ/D ratios of 2, 1.66, 1.47, 1.11 and 1 respectively. In second category where steel fibers are added the minimum percentage of reinforced is provided at the bottom of beams. The specimens are having dimensions of length 1100mm width 150mm overall depth varying from 500mm, 600mm, 700mm, 900mm & 1000mm respectively. HYSD bars are used for providing 0.3% of nominal reinforcement as main longitudinal tension reinforcement along with anchor bars where as mild steel bars are used to provide adequate shear reinforcement in all the beams as per the provision of IS 456: 2000. These deep beams of depth 500mm, 600mm & 700mm are tested in UTM where as beams of other depths are tested in loading frame. During testing of beam, strain readings are taken at support as well as mid span. Strains are measure by mechanical strain and electronic strain gauges, at each load increment strain III reading are taken. The crack patterns and mode of failure are observed in case of all the beams. Ansys software is use to compare with experimental result. Modeling in the Ansys includes, modeling, meshing, adding the structural elements as per the data, defining the structural properties and assigning those structural properties to the structural elements. For modeling, all dimensions are kept as per categories. After modelling, meshing is done to get more accurate results of strain and support conditions are as per the experimental setup and all properties are defined. These modelling and properties make realistic approach toward experimental work.