A large rupture strain (LRS) fiber reinforced polymer (FRP), with a rupture strain value of more than 5%, is a promising alternative to traditional FRPs with a 1–3% rupture strain for seismic retrofitting of reinforced concrete (RC) structures. The LRS FRPs provide a bilinear stiffness around concrete columns while this feature is linear for traditional FRPs (e.g., carbon FRP). This paper presents a careful analysis of the compressive behavior of LRS FRP wrapped square column, especially since their confining stress is nonuniformly distributed. A total of 66 square concrete columns, measuring 150 × 150 × 300 mm with varied corner radii from 0 to 75 mm were tested under monotonic axial compression. The experimental results, in terms of full stress–strain behavior, compressive strength, hoop strain distribution, and dilation behavior were systematically investigated. As the corner radius increases, the strength enhancement after LRS FRP confinement also increases, and the hoop strain is more uniformly distributed. The stress–train curves exhibit a triple-section pattern with a smooth transition zone. The peak dilation rate of LRS FRP-confined concrete is higher than that of traditional FRP-confined concrete, and the curve of dilation rate versus axial strain exhibits a remarkably long stable response. Moreover, results show that most existing models of FRP-confined concrete can provide conservative predictions for an improved compressive strength of LRS FRP-confined square concrete columns.

中文翻译：

---

大断裂应变 (LRS) FRP 约束方形混凝土柱的压缩行为：实验研究和模型评估

断裂应变值超过 5% 的大断裂应变 (LRS) 纤维增强聚合物 (FRP) 是传统 FRP 的有前途的替代品，断裂应变为 1-3%，用于钢筋混凝土 (RC) 结构的抗震改造. LRS FRP 在混凝土柱周围提供双线性刚度，而此特征对于传统 FRP（例如碳 FRP）是线性的。本文详细分析了 LRS FRP 包裹方柱的压缩行为，特别是因为它们的围压分布不均匀。在单调轴压下测试了总共 66 根方形混凝土柱，尺寸为 150 × 150 × 300 毫米，角半径从 0 到 75 毫米不等。实验结果，在全应力-应变行为、抗压强度、环向应变分布方面，和扩张行为进行了系统的研究。随着拐角半径的增加，LRS FRP约束后的强度增强也随之增加，环向应变分布更加均匀。应力-列车曲线呈现出具有平滑过渡区的三段模式。LRS FRP约束混凝土的峰值膨胀率高于传统FRP约束混凝土，膨胀率与轴向应变的曲线表现出非常长的稳定响应。此外，结果表明，大多数现有的 FRP 约束混凝土模型可以为 LRS FRP 约束方形混凝土柱的抗压强度提高提供保守的预测。应力-列车曲线呈现出具有平滑过渡区的三段模式。LRS FRP约束混凝土的峰值膨胀率高于传统FRP约束混凝土，膨胀率与轴向应变的曲线表现出非常长的稳定响应。此外，结果表明，大多数现有的 FRP 约束混凝土模型可以为 LRS FRP 约束方形混凝土柱的抗压强度提高提供保守的预测。应力-列车曲线呈现出具有平滑过渡区的三段模式。LRS FRP约束混凝土的峰值膨胀率高于传统FRP约束混凝土，膨胀率与轴向应变的曲线表现出非常长的稳定响应。此外，结果表明，大多数现有的 FRP 约束混凝土模型可以为 LRS FRP 约束方形混凝土柱的抗压强度提高提供保守的预测。