LAUSR

Crack width plays an important role in the automated serviceability and safety monitoring of bridges and buildings. The proposed three-marker method (TMM) tries to improve the robustness and accuracy of the traditional image-based crack width monitoring by introducing the self-numbering markers. The methodology of the TMM technique for the crack width monitoring is introduced and the procedure of application is illustrated. Specifications and requirements of the markers utilized by the TMM technique are analyzed. Besides, the number system is constructed to uniquely identify the markers. The procedure for marker identification in the TMM technique is tested and compared with the caliper readings, and the accuracy of 0.1 mm is achieved when the crack width is in the range from 0 to 12.04 mm. The proposed method is simple, temperature, rotational and scaling invariant, which could potentially be incorporated into a non-contact monitoring system in the long-term monitoring of bridges and buildings.