Spatial shape identification of long-span suspension bridges using 3d laser scanning technology

Nowadays, terrestrial laser scanning (TLS) technology is increasingly utilized in the field of bridge maintenance, because of its efficiency and speed of execution. However, challenges still remain for the practice of long-span bridges. In fact, for long-span bridges, the accuracy of point cloud data can be specially affected by the scan geometry. Long-span bridges such as suspension bridges, cable-stayed bridges or arch bridges are often used to cross rivers or valleys, which means that they are less sheltered by the natural environment, the main girders are extremely long, their length is close to the range of the scanner, and the conditions for setting up measurement stations often do not exist below the main span. This state of affairs forces us to adopt unfavorable scanning geometry, making scanning with small angles of incidence unavoidable, which may result in points cloud missing and inaccurate point cloud information for distant bridge components. To eradicate this challenge, we developed herein a portable auxiliary reflector to assist TLS scanner to obtain the intact and accurate point cloud data of a long-span bridge in unfavorable scan geometry conditions. In-filed tests have been conducted on the Ma'anshan Yangtze River Bridge with two 1080m spans for three consecutive years. We provide details about the whole scanning process, together with the identified results of bridge spatial deformation. Results show that the distant girder and cable points cloud data can be obtained entirely with high precision. Then, further comparative deformation analysis can be guaranteed based on the integrated points cloud data.