An Image-based Automatic Calculation Algorithm for Bridge Crack Size

The crack is a serious disease of bridges and one of the important topics in the bridge detecting. Compared with the traditional manual methods for measuring crack size directly or indirectly, this paper proposes a new method based on Matlab toolbox for digital calculation of crack images. After preprocessing and detecting the original image, some morphological operation like corrosion and expansion have been used in this paper to improve the calculation accuracy. Relying on the connected region calculation, the stepped line is introduced to approach the real crack and obtain the number of pixels in length and width. Then through some calculations, the true size of the crack can be converted from pixel values, which provides a good basis for determining its hazard level. At the end of this paper, experiment results verify the accuracy and practicability of the method, and this method can be used as a subsequent part of crack identification to obtain crack size information.