钢管混凝土界面黏结破坏的声发射特征及时空演化机制

Investigation on acoustic emission characteristics and time-space evolution mechanism of interface bond failure of concrete-filled steel tube

为研究钢管混凝土界面黏结-滑移的破坏机制,采用声发射(AE)监测系统对9个钢管混凝土试件的推出试验进行了声发射测试,获得了撞击计数、能量释放和频谱特征等AE信号特性。结果表明:荷载-滑移曲线可分为胶结段、非线性滑移段和滑移段。AE撞击计数率、能量释放率与黏结-滑移演化过程形成良好的对应关系。AE频谱特征中,胶结段的AE信号较少,其峰频和幅值分布带在0~80 kHz和0~55 dB区间;非线性初滑移段的AE信号不断增多,主要来自黏结界面中不断拓展的破坏裂纹,出现高频高幅值AE信号,其分布带集中于150~400 kHz和60~90 dB区间,非线性初滑移段中高频高幅值信号可作为界面发生黏结破坏的前兆信息;滑移段的AE信号较多,主要来自界面滑移摩擦,以低频低幅值信号为主,其峰频和幅值分布带集中于0~150 kHz和0~60 dB区间。AE信号源柱面定位结果揭示了推出试验下钢管混凝土界面黏结破坏裂纹从两端开始形成、逐渐向中部拓展的时空演化机制。

In order to study the mechanism of interface bond-slip failure in concrete-filled steel tube(CFST).The acoustic emission(AE)tests were carried out on the push-out test of nine CFST specimens by the AE monitoring system.AE impact counting,energy release,and frequency spectrum characteristics were obtained.The test results show that the load-slip curves consist of the adhesive stage,the nonlinear initial sliding stage,and the sliding stage.The evolution process of bond-slip corresponds well with the AE impact counting ratio and energy release ratio.In frequency spectrum characteristics of AE signals,the number of AE signals is less at the adhesive stage and its distribution regions of frequency and amplitude are in the range of 0-80 kHz and 0-55 dB.At the nonlinear initial sliding stage,the number of AE signals from expanding cracks of bond interface is increasing,and the distribution regions of AE signals with high frequency and high amplitude are in the range of 150-400 kHz and 60-90 dB.The AE signals with high frequency and amplitude in the nonlinear initial sliding stage could be used as the warning information of bond failure.The sliding stage is dominated by low frequency and low amplitude signals.The AE signals are more and mainly from interface sliding and friction.Its distribution regions of AE signals with low frequency and low amplitude are mainly in the range of 0-150 kHz and 0-60 dB.Cylindrical location results of AE signal source reveal the time-space evolution mechanism that the failure crack of bond interface firstly forms from two-ends and gradually expands to the middle part of CFST.