Abstract In recent years, small and medium-span reinforced concrete (RC) beams have suffered severe cracking at bearings and quarter span, and shear diseases have been a severe phenomenon for bridges. Currently, many methods are used for shear strengthening of RC beams, but some questions such as low reinforcement efficiency and poor durability still exist. Although externally bonded fiber reinforced polymer (FRP) has been widely used to strengthen concrete bridges, the utilization efficiency of FRP still needs to be improved. A closed FRP truss combining externally U-type and side bonded FRP is proposed, which aims to enhance the utilization efficiency of FRP and the shear capacity of RC beams in this paper. The calculation model is established to predict the shear capacity of RC beams strengthened with FRP truss by theoretical study, model tests and numerical simulations. FRP truss obviously enhances the shear capacity of RC beams and the utilization efficiency of FRP. Finite element method is used to analyze the influence of the stirrup ratio on the strengthening efficiency of FRP truss, which proves that reinforcement effects gradually increase with the decrease of stirrup ratio. Under ideal condition, FRP truss presents tensile failure when stirrup ratio is less than 0.18%.

中文翻译：

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碳纤维桁架钢筋混凝土梁抗剪承载力理论与试验研究

摘要 近年来，中小跨径钢筋混凝土(RC)梁在支座和四分之一跨处出现严重开裂，剪切病害已成为桥梁的严重现象。目前，钢筋混凝土梁的抗剪加固方法很多，但仍存在加固效率低、耐久性差等问题。尽管外粘结纤维增强聚合物（FRP）已广泛用于混凝土桥梁的加固，但FRP的利用效率仍有待提高。为了提高FRP的利用效率和钢筋混凝土梁的抗剪能力，提出了一种外U型与侧粘FRP相结合的封闭FRP桁架。通过理论研究，建立了FRP桁架加固RC梁抗剪承载力计算模型，模型试验和数值模拟。玻璃钢桁架明显提高了钢筋混凝土梁的抗剪能力和玻璃钢的利用效率。采用有限元方法分析了箍筋率对FRP桁架加固效率的影响，证明随着箍筋率的减小，加固效果逐渐增强。在理想条件下，当箍筋率小于0.18%时，FRP桁架出现拉伸破坏。