Research On Crack Detecting In Concrete Structure With Ultrasonic Single Plane Detecting Method

Sometimes, because of the omission in working management, environment and natural disasters, there are cracks come out of the concrete and ferroconcrete. The destruction of many structures begin with the cracks, so how to detect the character, extent and size of the cracks? This is an important issue in constructional engineering.This paper discourses on the development, existing conditions and basic theory of the ultrasonic nondestructive testing, and points out the advantage and application of single plane detecting. On the existing theory basis, this paper does some profound research in the ultrasonic nondestructive testing:(1)Brought up the concept of inclined crack. The existing ultrasonic single plane detecting only consider the vertical cracks, but in actual construction, the inclined cracks are usual, and vertical cracks are just the special cases. Therefore, it is necessary to research the detecting method and computing formula for the inclined crack, so that the ultrasonic single plane detecting can be more accurate.(2)Researched the velocity of ultrasonic in single plane detecting. By the ultrasonic velocity experiment on a concrete model, found out that it is accurate to use the velocity tested through the concrete rather than on the surface of the concrete in calculation. In essence, the first wave detected when testing on the surface is transverse wave, but when testing through the concrete, the first wave is longitudinal wave.(3)Designed a new detecting method for the inclined crack—trigonal cosine equation method. Using this new method and a traditional method to detect the same concrete model with inclined crack respectively, the result validated the rationality of this new method,and its error rate is much lower than the traditional method. So this new method has high accuracy, it can be used to detect the obliquity and length of single inclined crack.(4)Discussed the problems in single plane detecting and looked forward to the future research direction. Such as the effect of reinforcing steel when testing the ferroconcrete, the problem of testing more inclined cracks, and the possibility of using rayleigh wave to detect long cracks(≥500mm).