钢筋混凝土板裂缝对声发射波传播特征影响

目前利用声发射技术对混凝土结构进行裂缝定位或损伤检测时,并没有考虑已存在裂缝对声发射波传播特征的影响,这往往会使检测结果产生较大的偏差.为了探究裂缝参数对声发射波传播特征的影响,对3个不同保护层厚度的钢筋混凝土板试件进行了四点静力加载破坏试验和声发射测试,研究了裂缝深度、宽度、数量对钢筋混凝土板声发射波速和振幅衰减等传播特征的影响规律.试验和分析结果表明:裂缝深度对声发射传播特征的影响显著,声发射振幅衰减随裂缝深度增大而增大,声发射波速随裂缝深度增大而减小；声发射波速和振幅衰减几乎不随裂缝数量、宽度两参数变化而变化.在此基础上,提出考虑裂缝影响的修正波速时差定位法,进一步探讨了与采用传统时差定位法相比对钢筋混凝土损伤定位的影响,结果显示,基于修正波速的时差定位法对钢筋混凝土板进行损伤定位精度更高.

Influence of cracks in RC slabs on propagation properties of acoustic emission

The influence of existing cracks on acoustic emission (AE) wave propagation characteristics is not taken into account when using AE technology to locate cracks or detect damages in concrete structures, which often leads to large deviations in detection results. To explore the influence of crack parameters on the velocity and amplitude attenuation of AE wave in reinforced concrete (RC) slabs, four-point static loading test and AE test were carried out on three RC specimens with different protective layer thicknesses, and the influences of crack depth, crack width, and crack amount on the propagation properties of AE wave were analyzed. Tests and analysis results show that crack width and crack amount both had little effect on the velocity and amplitude attenuation of AE wave, while crack depth had significant effect. With the increase of the crack depth, the amplitude attenuation increased, and the velocity decreased. Then, a time-of-arrival location method based on variable velocity was proposed considering the effects of cracks, which was compared with traditional method in detecting crack locations. Results indicate that the proposed method had higher accuracy in detecting crack locations in RC structures.