Abstract
Many researchers worldwide have extensively used fibre-reinforced polymer (FRP) strengthening materials and near-surface mounted (NSM) to enhance the shear and flexural strengths of reinforced concrete (RC) beams. However, studies on torsional strengthening are limited. Although a few studies have focused on torsional strengthening, none of them simultaneously investigated torsion with shear and/or bending moment. This study aims at demonstrating the behaviour of RC beams strengthened with FRP sheets (strips) with different configurations and NSM steel bars with different spacing that was subjected to combined actions of torsion and bending moment and making a comparison between them. Seven beams with a dimension of 15 × 25 × 200 cm were casted. One of the beams was not strengthened; three of them were strengthened with carbon FRP, and the others were strengthened with NSM steel bar. The angle of twist at torque intervals, first cracking torque, ultimate torque, and ultimate twist angle of the conventional and strengthened beams during the testing process are compared. Results show a significant improvement in the torsional performance of RC beams using carbon FRP and NSM steel bar. The test beams that were strengthened with CFRP wrapping showed better enhancement in the ultimate torsional moment as opposed to the beams that were strengthened with NSM steel bar.
Highlights
A considerable amount of torque can accumulate in many concrete members, including curved bridge elements, spandrel beams, horizontally curved members, and eccentrically loaded beams. e torsional capacity of these members needs to be maximized due to several factors, including structural damage, deterioration, and increased loading.Strengthening or upgrading of structural elements must be performed after a certain period to increase the service life of these elements [1, 2]
Strengthening materials can be applied to reinforced concrete (RC) structures in two ways, namely, (1) the externally bonded reinforcement (EBR) method, where the strengthening materials are externally applied to the concrete surface, and (2) the near-surface mounted (NSM) method, where the strengthening materials are inserted within grooves that are pre-cut into the concrete cover [3]
The results demonstrate the significant improvement of Tcr, Tu, and θu of the concrete beams with the use of fibre-reinforced polymer (FRP) sheets and NSM steel bar
Summary
E torsional capacity of these members needs to be maximized due to several factors, including structural damage, deterioration, and increased loading. Strengthening or upgrading of structural elements must be performed after a certain period to increase the service life of these elements [1, 2]. Several externally bonded reinforcement (EBR) methods of increasing the service life of RC structural elements are available; for example, fibre-reinforced polymer (FRP) strengthening sheets are used to wrap RC structural elements. Is technique is inexpensive and can be applied to completely degraded structures. Compared with traditional techniques, repairing concrete structures by using FRP sheets has many advantages. Changing the geometry of the structure is unnecessary when these sheets are used. A few studies focused on torsion strengthening [1, 2, 32,33,34,35,36,37,38,39,40]
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