Development of structure and pavement inspection using mobile laser scanning point clouds: a case study of Thailand expressway

Infrastructures must be inspected regularly in order to ensure serviceability and public safety. In case of Thailand expressway, a 200 km of elevated structure must be inspected once a year. The visual inspection for detecting defects and structure movements cannot be performed due to several limitations Therefore, a mobile mapping 3D laser scanning (MLS) which is high resolution 3D laser scanners (Trimble MX-8) equipped on a vehicle was introduced. The scanning by MLS was performed on live traffic on expressways. Point cloud data was rectified and cleaned out of unwanted data by MLS operator. The dimension measurement by point cloud was validated with a total station. This study aimed to assess the performance of MLS in performing the health monitoring of a cable stayed bridge for the first time. A 450 m long cable stayed bridge deck profile, bridge deck twist angles, and pylon curvatures were measured using point cloud data. MLS scanning on expressway gave not only structure geometry data but also pavement point cloud data. Every road agency in Thailand relies on laser profilometer as a default machine. Each pavement segment was executed for IRI and rut depth using “Pavement inspection program” which is the program developed by Tokyo University and Shotoku engineering of Japan. Correlation between these two methods of IRI measurement were observed. Even though they have not much good agreement, MLS can be applied to estimate IRI. The results revealed that IRI and rutting depth measured by MLS were higher than those obtained by profilometer. However, empirical relations were proposed to transform MLS obtained IRI and rutting depth to their equivalent profilometer readings.