Shear behaviour of macro-synthetic fibre-reinforced concrete beams GFRP reinforcement

Ebrahim, Yahia Ali Alam (2013) Shear behaviour of macro-synthetic fibre-reinforced concrete beams GFRP reinforcement. Masters thesis, Memorial University of Newfoundland.

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Abstract

The purpose of this study was to investigate the influence of macro synthetic fibre on the shear behaviour of Glass Fibre Reinforced Polymers (GFRP) reinforced concrete beams. The experimental program was carried out in two phases: material tests and structural investigation. -- In the material investigation, thirty two prisms (100 mm x 100 mm x 400 mm) and thirty six cylinders (100 mm x 200 mm and 150 mm x 300 mm) were cast to determine the mechanical properties of concrete containing macro-synthetic fibres. The samples were tested to investigate and to develop a clear understanding of the effect of the amount of macro synthetic fibre on the concrete properties. For the prisms, the investigation focused on the modulus of rupture, flexural toughness, toughness indices, while for the cylinders, the compressive strength and splitting tensile strength were investigated. -- In the structural investigation, sixteen reinforced concrete beams were tested up to failure at the structural laboratory of Memorial University (MUN) to study the behaviour of the beams in terms of deflection characteristics, shear and flexural behaviour, concrete and GFRP strains and ultimate load capacity. The dimensions of the simply supported beams were 250 x 350 x 2840, 250 x 350 x 2840, 250 x 500 x 3540 and 250 x 350 x 3540, measured in millimetres. The main variables in the structural investigation were the amount of synthetic fibre by volume, reinforcement ratio, effective depth, and shear span to depth ratio. -- The test results revealed that the inclusion of different volumes of macro synthetic fibre enhanced the shear failure behaviour of GFRP reinforced concrete beams, and increased the normalized shear strength of the reinforced concrete beams by an average of 35% for beams reinforced with 1.3 Ph and 1.5 Ph respectively. The increase in the normalized shear strength for the deeper beams with a depth of 441 mm was approximately 39 %. Furthermore, GFRP reinforced concrete beams an increase in the post cracked stiffness of the beams. As it was expected, the addition of fibre increased the increased the beams' maximum deformation by 35%, when it was compared to the control beams that had 0% of macro synthetic fibre. -- The capacity of the beams was compared to the predictions of the different models propsed I the literature for steel fibre reinforced beams. The model proposed by Greenough and Nehdi (2008) which gave the best predictions of the test results. -- Finally, a finite element analysis was carried out using ANSYS and a finite element model was developed. The FEA model was calibrated using the experimental results. All the necessary steps to create and calibrate the model are presented and explained. A comparison of the test results with the finite element model predictions was carried out in terms of the ultimate load capacity, the maximum deflection and the cracks pattern of the test specimens. The load-deflection characteristics obtained from the finite element solution at the center of the beam were in close agreement with the experimental test results at first cracking stage and at failure stage. In terms of, the initial crack, progressive cracking or the failure mechanism, the finite element model compared well to the experimental data obtained and the predicted failure load was very close to the measured load during experimental testing.

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