Shear behaviour of steel fibre-reinforced high strength lightweight concrete beams without web reinforcement

Alzahrani, Fahad (2018) Shear behaviour of steel fibre-reinforced high strength lightweight concrete beams without web reinforcement. Masters thesis, Memorial University of Newfoundland.

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Abstract

The main objective of this investigation was to determine the influence of adding two different shapes with different lengths of steel fibres on the shear behaviour of lightweight and normal weight concrete beams with normal and high concrete grades. Thirty-six prisms of (100 mm wide, 100 mm deep, and 400 mm long) and seventy two cylindrical samples of (100 mm diameter  200 mm high) were cast and tested to determine the concrete mechanical properties for specimens. These samples were tested in order to discover the role of steel fibres on enhancing concrete properties in general. The modulus of rupture, flexural toughness, toughness, compressive strength and splitting tensile strength were inspected based on the small-scaled material samples. In the structural experiment, a group of twelve large-scaled reinforced concrete beams without shear reinforcement were primarily analyzed, designed and tested in the structures lab at Memorial University of Newfoundland (MUN). These specimens were built to study the load-deflection curves, shear and flexural behaviour, concrete and steel strains and the ultimate load resistance. Simply supported beams with dimensions of (200 mm wide, 400 deep, and 2900 mm long) were structurally tested, analyzed and discussed. in order to investigate the previous responses. Three factors were proposed in this experiment. The first factor was the type of the aggregates and the second parameter taken into consideration was the concrete compressive strength that divided the beams into two groups of high and normal strengths. Thirdly, two different lengths of steel fibres with different end-shapes were considered as the third variable in order to evaluate the effects of the length of the steel fibres on the shear behaviour. All beams contained 1.46% of longitudinal tension reinforcement ratio. Besides this, a fixed concrete cross section was suggested for all beams. Testing specimens were setup on a specified constant shear span-to-depth ratio of 3. According to a recommendation by ACI, a fixed volume fraction of 0.75% of steel fibres was added to SFRC beams. The specimens with long fibres resisted higher shear stresses and were more ductile than the ones reinforced with shorter fibres. Overall, the presence of both short and long steel fibres improved beams shear resistance by a range varied from 35% to 72% compared to reference RC beams. However, shear strength of beams with long steel fibres enhanced more by an average amount of 10% in contrast with short SFs beams.

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