基于空气耦合非线性共振频率偏移的混凝土损伤评估

摘要

针对受损混凝土的整体损伤评估,提出并验证了基于空气耦合的非线性共振频率偏移法.首先通过对混凝土试件进行逐级加载实现了试件损伤的累积,之后利用空气耦合传感器代替传统的接触式传感器进行了试件振动信号采集.研究了距离对空气耦合漏泄波强度的影响;并对两种传感器采集信号的频谱特性进行了对比分析.最后构建非线性共振频率偏移损伤指标迟滞非线性系数对受损混凝土构件的损伤过程,进行了跟踪分析与刻画;并与以纵波波速和固有频率作为线性损伤指标的损伤评估方法进行了对比.实验结果表明,空气耦合方法可快速有效地进行试件振动信号采集;随着试件损伤的累积,非线性损伤指标和线性损伤指标均发生了变化,但迟滞非线性系数的变化更为显著.研究成果为混凝土损伤识别提供了新方法和新思路.%A novel nonlinear acoustic technique, air-coupled nonlinear resonance frequency shift, was devel-oped and used to characterize the compressional damage in concrete.The damage was induced by step compression-al loading to a concrete prism and instead of contact sensor,air-coupled non-contact sensor was used for signal ac-quisition.The effect of sensor height to signal amplitude, as well as the spectrum distribution of signals obtained from both contact and non-contact sensors,were investigated.The hysteretic nonlinearity coefficient,as the nonlin-ear resonance frequency shift index,was used to track the damage process of the concrete prism.For comparison purposes,two linear damage indicators, compressive wave velocity and linear resonance frequency were measured parallel to the nonlinear damage indicator during the test.The results show that the air-coupled sensor could catch the leaky resonant waves effectively and the hysteretic nonlinearity coefficient is more sensitive to the linear damage indicator.The research provides a new means and new idea for damage identification of concrete.