应力历史影响下混凝土应力的激光超声检测

Laser Ultrasonic Detection of Concrete Stress under the Influence of Stress History

为了探讨应力历史对激光超声技术检测混凝土应力状况的影响及应用声弹性技术原理,开展了基于激光超声的混凝土试件单轴循环加载试验,分析了应力历史对声弹性效应的影响。试验结果表明,多次循环荷载作用后瑞利波速度与应力在荷载循环阶段表现出稳定的正比例关系。由实测瑞利波相对波速与应力拟合得到的声弹性系数可用于计算混凝土试件绝对应力,计算误差受历史应力影响,声弹性公式的应用表现出一定的局限性。根据试件从无应力状态重新加载直至破坏状态这一阶段非绝对线性的波速-应力曲线,利用70%的极限应力定义了混凝土构件的安全系数并构建了安全系数与应力状态的模型,提出了一种基于激光超声的混凝土应力状况判别方法,对混凝土绝对应力的计算结果加以补充判断,为混凝土应力状况的检测与评价提供参考。

In order to explore the influence of stress history on the detection of concrete stress by laser ultrasonic technology,a uniaxial cyclic loading test of concrete specimens based on laser ultrasonic technology was carried out based on the principle of acoustoelastic technology,and the influence of stress history on acoustoelastic effect was analyzed.The test results show that the Rayleigh wave velocity and stress show a stable and proportional relationship in the load cycle stage after repeated cyclic loading.The acoustic elastic coefficient obtained by fitting the measured relative wave velocity of Rayleigh wave and the stress can be used to calculate the absolute stress of the concrete specimen.The calculation error was affected by the historical stress,and the application of the acoustic elastic formula shows certain limitations.According to the non-absolute linear wave-stress curve of the specimen from the unstressed state to the failure state,the safety factor of the concrete member is defined by using the 70%ultimate stress,and the model of the safety factor and stress state was established.At the same time,A method of judging the stress state of concrete based on laser ultrasonic wass proposed,which supplements the calculation results of the absolute stress of the concrete,and provides a reference for the detection and evaluation of the concrete stress status.