Most existing studies on fiber reinforced polymer (FRP) confined concrete have focused on undamaged concrete that is subjected to uniaxial monotonic compression. However, FRP jackets are usually applied to concrete columns with existing material damage and potential future damage. This paper investigates FRP confinement on concrete with damage before and after FRP jacketing. A total of 32 FRP-confined concrete specimens were tested under axial compression in this work. The prior damage before FRP jacketing was implemented as predamaging by applying preloading and then release on the plain concrete specimens. The post damage after FRP jacketing was performed by applying cyclic axial compression loading on FRP-confined concrete specimens. The test results reveal that the concrete predamage levels have significant influences on the cyclic stress–strain curve and envelop stress–strain curve for FRP confined concrete under cyclic loading. Existing models on ultimate state, plastic strain, reloading and unloading moduli were evaluated and investigated in this work.

中文翻译：

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预损伤和循环荷载对纤维增强聚合物约束混凝土压缩行为的影响

大多数现有的关于纤维增强聚合物 (FRP) 约束混凝土的研究都集中在受单轴单调压缩的未损坏混凝土上。然而，FRP 护套通常应用于具有现有材料损坏和潜在未来损坏的混凝土柱。本文研究了在 FRP 护套前后 FRP 对损坏混凝土的约束。在这项工作中，共有 32 个 FRP 约束混凝土试件在轴向压缩下进行了测试。FRP 护套之前的先前损坏是通过施加预加载然后在素混凝土试件上释放来实现的预损坏。FRP 护套后的后损伤是通过对 FRP 约束混凝土试件施加循环轴向压缩载荷来进行的。试验结果表明，混凝土预损伤水平对循环荷载作用下FRP约束混凝土的循环应力-应变曲线和包络应力-应变曲线有显着影响。在这项工作中评估和研究了关于极限状态、塑性应变、重新加载和卸载模量的现有模型。