Abstract

Many researchers worldwide have extensively used fibre-reinforced polymer (FRP) strengthening materials to enhance the shear and flexural strengths of reinforced concrete (RC) beams. However, Studies on strengthening of RC beam subjected to combined torsion and bending moment using both spiral and vertical strip configuration of CFRP that explored in this study is rare. This study aims to demonstrate the behaviour of RC beams strengthened with FRP sheets (strips) with different configurations and subjected to combined actions of torsion and bending moment. Eight beams with a dimension of 15 × 25 × 200 cm were cast. One of the beams was not strengthened, but the others were strengthened with carbon FRP. 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 were compared. Results showed a significant improvement in the torsional performance of RC beams using carbon FRP. The fully wrapped beams performed better than the beams with strip wrapping due to the influence of various wrapping configurations. Amongst the wrapping configurations of FRP fabrics, the 45° spiral strip wrapping configuration was the most effective for RC beam strengthening in terms of torsion resistance.

• Highlights

• Reinforced concrete (RC) beams strengthened with fiber reinforced polymer composite were tested under combined bending and torsional moment;

• The effect of composite orientation, spacing and number of plies on the torsional response;

• Ultimate torsional moments of RC beams;

• Twist angle of rotation of control and strengthened beams;

• Analytical prediction for CFRP material contributions to the ultimate torsional moment of strengthened RC beam.

摘要

世界各地的许多研究人员已广泛使用纤维增强聚合物 (FRP) 增强材料来提高钢筋混凝土 (RC) 梁的剪切和弯曲强度。然而，在本研究中探索的同时使用螺旋和垂直条形结构的CFRP加固RC梁的研究很少。本研究旨在展示采用不同配置的 FRP 板（条）加固并承受扭转和弯矩联合作用的 RC 梁的行为。铸造了八根尺寸为 15 × 25 × 200 cm 的梁。其中一根梁没有加固，但其他梁用碳 FRP 加固。扭矩间隔处的扭转角，第一次开启扭矩，比较了常规梁和加固梁在试验过程中的极限扭矩和极限扭转角。结果表明，使用碳 FRP 的 RC 梁的抗扭性能显着提高。由于各种缠绕配置的影响，完全缠绕的梁比带条缠绕的梁表现更好。在 FRP 织物的缠绕结构中，45° 螺旋带缠绕结构在抗扭强度方面对 RC 梁的加固最有效。

• 强调

• 用纤维增强聚合物复合材料加固的钢筋混凝土（RC）梁在弯扭组合力矩下进行了测试；

• 复合材料方向、间距和层数对扭转响应的影响；

• RC梁的极限扭转力矩；

• 控制和加强梁的扭转旋转角度；

• CFRP材料对加固RC梁极限扭转力矩贡献的解析预测。