Non-contact Measurement Method For Structural Crack Identification And Bridge Drift Ice Monitoring

Bridges in cold region are often threatened by ice and frost disasters,which are mainly manifested in the damage and destruction of the bridge structure caused by the impact of ice on the bridge piers and the frost cracking of concrete.Carrying out research on drift ice parameters and the identification of concrete cracks,and establishing measurement techniques for ice and frost disasters in cold areas are essential to ensure the safety of bridge structures.The traditional ice and frost disaster measurement is mainly based on on-site manual measurement,which requires a lot of manpower and material resources,and has high risk coefficient and low accuracy.In recent years,computer information technology has developed rapidly,and machine vision has become more and more widely used in various fields.Compared with traditional measurement technology,non-contact measurement technology based on machine vision is more efficient and accurate.Therefore,this method shows more and more advantages in the field of structure detection.In this paper,the methods of theoretical research,laboratory test and field test are used to carry out the research of non-contact measurement technology for the ice and frost damage of Bridges in cold regions.The main works are as follows:(1)By extracting the crack width information,this paper discusses the applicable scope of object distance method and scale method,and establishes an integrated crack width identification method based on scale method and object distance method.Research shows that the integrated crack width identification method based on scale method and object distance method can accurately calculate the crack width greater than 0.10mm.Among them,the effect of object distance method is better for the cracks with width between 0.10mm and 0.20mm,and the scale method is better for cracks with a width greater than 0.20mm.(2)By extracting the length and shape information of the cracks,the reconstruction of concrete cracks can be achieved.Studies have shown that the "double-edge skeleton method"based on the statistics of pixel area by region can improve the pixel missing and pixel redundancy problems in the "central skeleton method" when calculating the crack length.The improved matching algorithm of scale invariant feature transform(SIFT)based on feature point association can solve the problem of mismatching and non-matching of feature points during image registration.(3)Discuss the non-contact measurement method suitable for drift ice area and speed by applying "scale method" to the large scene measurement of drift ice parameters,and establish a video monitoring system for drift ice parameters of bridges in cold regions.Study and analyze the ice thickness data during icing,and use the least square method to derive the functional relationship of ice thickness variation with time to estimate the thickness of drift ice.The results show that scale method can accurately measure the drift ice area and velocity,and the relation equation between ice thickness and time based on the least square method can accurately estimate the ice thickness.