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Go to Editorial ManagerThis numerical study aimed to investigate the torsional behaviour of hollow cross section reinforced concrete members strengthened with steel fibers (end hooked and corrugated), subjected to pure torsion. The numerical results were compared with experimental results and show good agreement. The experimental study was conducted on ten steel fiber reinforced concrete specimens with low longitudinal reinforcement ratio to investigate the torsional behavior under pure torsion. For this analysis, a computer program (ANSYS 18.2) was used. The brick elements 8-nodes (SOLID65) were used to concrete simulation, while the steel bars simulated as axial members (link 180). The steel fibre was represented theoretically by the stress-strain relationship. The theoretical results indicated that the adopted smeared crack model is capable of making relatively acceptable estimations of cracking and ultimate torsional capacity of the members.
A large number of RC structures or at least some of their members need strengthening or rehabilitation. Among the typical failure modes, the shear failure is more dangerous and less predictable, because of usually brittle behavior and sudden collapse. Therefore, there are necessities for upgrading the shear capacity and the local ductility of reinforced concrete beams. In this study, four different techniques of concrete jacketing were used to improve the behaviors of the shear deficiencies beams. The four techniques used in this study to enhance the behavior of the beams were by using a Self-Compacted Fiber Reinforced Concrete jacket without stirrups (S.-J. + Steel Fiber), a concrete jacket of Self Compacted Concrete with stirrups (S.-J. + Stirrups), a concrete jacket of ferrocement jacket (S.-J. + Ferrocement), and a concrete jacket of ferrocement jacket with external steel reinforcing bars (S.-J. + Ferrocement + R). These techniques contributed to enhancing the load-carrying capacity and delaying the appearance of the first crack in tested beams compared with the control beam by a percentage of (35, 59, 30, 6) % and (18, 35, 81, 80) %, respectively. The specimen (S.-J. + Stirrups) showed the best performance in comparison with the other used strengthening techniques used in this study in terms of stiffness and the ultimate load-carrying capacity. The ferrocement jacket (S.-J. + Ferrocement) was found to be the most suitable jacketing system used to enhance the shear capacity in terms of cracking load.
This study investigates the effect of the shear span-to-effective depth ratio (a/d) on the behavior of high-strength steel fiber–reinforced concrete deep beams without stirrups containing circular web openings. A circular opening of 12.6 cm diameter was positioned at the center of the shear span, and beam performance was evaluated in terms of crack patterns, load–deflection response, and stress–strain behavior. Four specimens were tested experimentally. The control specimen consisted of a solid deep beam without openings and without steel fibers, while the remaining three specimens were reinforced with 1% steel fibers and included circular openings. All specimens were reinforced with 2Ø12 mm top bars, 3Ø16 mm bottom bars, and two stirrups at the supports to prevent local failure. The beams had different shear span ratios (a/d = 0.75, 1.0, and 1.5) and corresponding total lengths of 1025 mm, 1200 mm, and 1550 mm, respectively. All specimens were simply supported and subjected to two-point loading. The experimental results revealed that the optimal shear span ratio for maximum performance was a/d = 0.75 when combined with 1% steel fiber reinforcement. In addition, the ultimate strength of beams with circular openings decreased as a/d increased, with a strength increase of approximately 5.48% at a/d = 0.75 compared with a/d = 1.0.