混凝土受力状态下超声波传播特性研究

本文研究了混凝土在单轴向压力下超声波速、幅值及主频的变化规律。试验表明，波速对混凝土构件中的应力变化敏感度较低，在７０％的极限应力范围内，波速基本保持稳定。因此在工程实际中利用超声波速－强度率定曲线推测混凝土承力构件的强度时，波速无需修正。与波速相比，超声幅值衰减量对检测裂筵开展则具有较高的灵敏度。为提高超声检测的精度，本文采用波速、幅值、频率综合判断法，提出了损伤系数的概念，对混凝土的损伤程度作出定量评价，文中结果对进一步提高混凝土无损检测精度，评估混凝土结构在受力、收缩、徐变等因素影响下的损伤程度有一定的应用价值。

ULTRASONIC PULSES BEHAVIOR IN CONCRETE DURING COMPRESSIVE LOADING

The paper investigates the variation of ultrasonic pulse velocity, attenuation and frequency in concrete udder uniaxial compressive loading Experimental results indicate that the pulse velocity in concrete is independent of the stress level to a large extent, up to about 70% of the compressive strength. This means, in practical terms, that stresses prevailing in the concrete of a structure do not have to be taken into account when pulse velocity data are used for the evaluation of the quality of concrete. Compared with velocity, the amplitude of ultrasonic waveform has higher sensitivity to the extent of cracking. In order to improve the reliability of measurement, thepaper combines velocity, amplitude and frequency to propose a damage coefficient D as anindicator of crack growth. The results proposed in this paper are useful for improving reliability of non-destructive test of concrete, and determining the extent of damage due to load, creep, shrinkage,and other environmental effects.