Concrete-filled steel tube (CFST) widely applied in engineering structures due to its superior behavior requires monitoring and assessment for damage level. Here, the acoustic emission (AE) technique was used to monitor the fracture process of concrete core in CFST stub columns subjected to axial compression. Test and analyzed results show that the damage process of CFST specimens can be divided into four stages: compaction, elastic-plastic stage, strengthening and secondary strengthening. In the elastic-plastic stage, the evolutionary features of the AE event rate, cumulative energy, Ib-value and crack classification are capable of providing an early warning for cracked concrete core. Full crack propagation can be identified by the rapid increase in the proportion of shear cracks near the inflection point of load, which is impermissible in engineering structures. According to the analyses of the AE event rate and signal intensity in the elastic-plastic stage, the confinement of steel tube with thicker wall thickness or higher strength is delayed, which implies that this confinement is suggested to be triggered early. It is indicated that the AE technique has the potential to monitor and evaluate the damage process of CFST stub columns under axial compression, which can provide additional insight into the failure mechanism and assist in the scheme of repairs.

中文翻译：

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基于声发射的轴压钢管混凝土短柱损伤分析

钢管混凝土（CFST）因其优越的性能而广泛应用于工程结构中，需要对其损伤程度进行监测和评估。这里，声发射（AE）技术被用来监测受轴压作用的钢管混凝土短柱中混凝土核心的断裂过程。试验分析结果表明，钢管混凝土试件的损伤过程可分为压实阶段、弹塑性阶段、强化阶段和二次强化阶段4个阶段。在弹塑性阶段，AE事件率、累积能量、Ib值和裂缝分类的演化特征能够为混凝土核心裂缝提供早期预警。完全裂纹扩展可以通过荷载拐点附近剪切裂纹比例的快速增加来识别，这在工程结构中是不允许的。根据弹塑性阶段AE事件发生率和信号强度的分析，壁厚较厚或强度较高的钢管的约束被延迟，这意味着这种约束建议提前触发。这表明AE技术具有监测和评估轴压下钢管混凝土短柱损伤过程的潜力，可以为破坏机制提供额外的见解并协助制定修复方案。