Structural modal identification using a portable laser-and-camera measurement system

Abstract

Vision-based techniques for modal analysis of full-scale civil infrastructure have been constrained by the challenge of collecting measurements of all points on a large structure using limited-resolution video devices. This paper proposes a portable, simple-to-assemble laser-and-camera (LAC) system capable of measuring multipoint displacements at a low cost. An efficient video processing flow with an improved binarization strategy for pinpointing the laser spot's center is provided to extract the displacement from the video collected by LAC devices. In addition, the laser-assisted vision-based measurement technique is implemented for structural modal identification for the first time. To evaluate the performance of LAC devices in displacement measurement and structural modal identification, an error analysis test, a measurement accuracy test, and a scaled bridge model experiment are conducted in succession. The results with different types of laser receiving panels and under variable light environments demonstrate the feasibility and application potential of the proposed LAC system and approach for structural health monitoring.