先张后粘FRP的钢筋混凝土构件抗弯能力分析

针对钢筋混凝土结构外贴FRP进行加固时，FRP材料利用率较低的情况，采用对FRP先张拉再粘贴的办法，以提高构件使用阶段的性能、极限承载力和FRP强度利用率。在试验研究基础上，研究先张后粘FRP加固钢筋混凝土受弯构件的各种破坏类型、加固构件有效预应力、消压弯矩和开裂弯矩的计算方法；分析预应力FRP-RC复合截面多种可能的受弯极限应变组合状态，由界限破坏得出界限配纤率和界限弯矩；根据混凝土最大压应变得出FRP拉断相应的不同极限承我力表达式和混凝土压碎破坏时的极限承载力公式。研究结果表明，试验梁极限荷载计算值与实测值较吻合；所得出的抗弯分析方法和计算公式可供内嵌预应力FRP加固设计参考。

Analysis of flexural capacities for RC members bonded with pre-tensioned FRP

In practice of structural strengthening,the technique of externally bonding fiber-reinforced polymer(FRP) has been extensively employed.In order to make full use of the tensile strength of FRP and/or improve the stiffness under service load or crack-resistant capacity of a reinforced concrete(RC) bending member, FRP can be pre-tensioned before it is bonded to the member.Based on the experimental observation,various types of failure are studied for reinforced concrete members strengthened by externally bonding pre-tensioned FRP.Formula are presented to calculate the effective pre-stress,the bending moment at which the pre-compressive stress vanishes at extreme fiber of the critical section and the moment at cracking for the strengthened member.All possible strain combinations at ultimate limit state of flexure are analyzed for the FRP-RC composite section.Expressions are proposed to distinguish between two modes of flexural failure respectively due to fracture of FRP and crushing of concrete.A set of equations are suggested for prediction of the corresponding ultimate strength,and meanwhile the applicability of the proposed formula is validated by the good agreement of the analytical results with the measured values.In addition,the method and formula put forward in this paper can serve as references for design of strengthening by near-surface mounting(NSM) pre-tensioned FRP.