Abstract This paper presents a detailed study on the development of axial, lateral and Von Mises strains measured by contact and non-contact methods under axial compression fiber reinforced polymer (FRP) confined and unconfined concrete specimens. The focus of the study was on the correlation between macro responses and localized deformations and the effects of FRP confinement on the localization of deformations. A total of 10 specimens were experimentally tested with a range of instrumentation to measure different types of strain. Digital image correlation (DIC) was used to obtain full-field strain evolution during compressive loading of concrete specimens confined with various fiber reinforced polymers. The effect of confinement material on the compressive behavior and strain distribution of FRP-confined concrete was investigated. The evolution of axial, lateral and Von Mises strains were recorded and examined during axial loading, including post-peak strain softening behavior. Data recorded by the typical contact method of linear variable displacement transformers (LVDTs) and strain gauges were used to validate the non-contact DIC method. The results obtained from DIC data in this study showed that expansion of shear zone for unconfined concrete is more localized than FRP-confined specimens. The results also show that specimens confined with CFRP induced homogenous compressive behavior, whereas GFRP and BFRP specimens with lower lateral stiffness displayed local strain concentration and less homogenous response. It was also observed that DIC provides a more accurate estimation of the ultimate condition compared to the contact methods due to the ability of DIC to capture the evolution of full-field strains.

中文翻译：

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使用数字图像相关性研究无侧限和 FRP 有侧限混凝土的压缩行为和破坏模式

摘要 本文详细研究了在轴向压缩纤维增强聚合物 (FRP) 有约束和无约束混凝土试件下通过接触和非接触方法测量的轴向、横向和 Von Mises 应变的发展。研究的重点是宏观响应与局部变形之间的相关性以及 FRP 限制对变形局部的影响。使用一系列仪器对总共 10 个样品进行了实验测试，以测量不同类型的应变。数字图像相关性 (DIC) 用于在受各种纤维增强聚合物限制的混凝土试样的压缩载荷期间获得全场应变演变。研究了约束材料对 FRP 约束混凝土的压缩行为和应变分布的影响。在轴向加载期间记录和检查轴向、横向和 Von Mises 应变的演变，包括峰值后应变软化行为。通过线性可变位移变压器 (LVDT) 和应变计的典型接触方法记录的数据用于验证非接触式 DIC 方法。在本研究中从 DIC 数据获得的结果表明，无侧限混凝土的剪切区膨胀比 FRP 有约束试件更局部化。结果还表明，受 CFRP 限制的试样引起均匀压缩行为，而具有较低横向刚度的 GFRP 和 BFRP 试样显示局部应变集中和较不均匀的响应。