Experimental and Numerical Investigation on the Flexural Behaviour of Concrete Beams Containing Steel Plates
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2022-02-10
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Strengthening is becoming the most popular way of enhancing the capacity of Reinforced Concrete (RC) beams. Steel plate is one of the most typical materials used for strengthening of RC structures. This research focuses on using the steel plates internally to improve the flexure performance of simply supported RC beams. Compared to other strengthening techniques, using steel plates provides very slight increase in the weight of the strengthened elements, in addition, this technique does not change in the structure's appearance. Furthermore, using it does not require high skills or special workers. In this research, experimental and numerical investigations on strengthening of RC beams with different configurations of internal steel plates were carried out and its contribution to flexural behaviour was obtained. Eighteen reinforced concrete beams were cast and cured for 28 days. The steel plates were fixed at the tension side of the RC beams to investigate their effect on the flexural behaviour of the tested beams. To achieve the research objectives, three configurations of the shape of steel plates were proposed: flat, curved and rounded. In addition, two holes were made in each piece of steel plates to enhance the bond between steel plates and concrete, and to decrease the weight of them. The results showed that the higher load-carrying capacity was achieved using flat steel plate by an average of 54% compared with the reference beam. Furthermore, using flat steel plates provided higher enhancements in flexural behaviours such as ductility, elastic stiffness, and toughness by 200, 22.84 and 621%, respectively, compared with the reference beam. Similarly, constrained the flat, curve, and rounded steel plates with lateral steel plates provided a high load-carrying capacity, ductility, elastic stiffness and toughness. For instance, constraining the flat steel plate with two inclined steel plates by 45o on both sides improved the ultimate load, ductility and elastic stiffness by 7.6, 3.16 and
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35.65%, respectively compared with non-constrained specimen. Regarding the effect of steel plate’s thickness, the load-carrying capacity and other flexural behaviours enhanced with the increase of thickness, except in the rounded steel plated specimens. The numerical part included modelling and verifying the results of eighteen reinforced concrete beams using (ABAQUS) finite element program. A parametric study included compressive strength of concrete, yield strength of steel plates, degree of curvature of steel plates and existence of holes in steel plates were also conducted. An acceptable match has been obtained between the experimental and numerical results, which proves the adequacy of the simulation process. And the maximum difference between the numerical and experimental ultimate loads was 6.13%. Also, there was an agreement in crack pattern and modes of failure between numerical and experimental beams. From the experimental and numerical investigations, it can be concluded that using flat steel plate with 6 mm thickness and constraining the plate with two 45o inclined steel plates enhances the bond between steel plates and concrete and results in improving the flexure behaviour. Also, in the case of using curved steel plates, it can be concluded that beams with curved steel plate showed improvement in the load-carrying capacity. However, it was slightly lower than its comparable flat steel plate. Furthermore, the height of the curve must be less than the neutral axis depth to achieve the best effect on flexure behaviour.