Full-field Displacement Measurement Method for Large-scale Structures by Using Tile Patterns

Abstract

   Imaging based nondestructive monitoring systems are important to evaluate the integrity of large-scale infrastructures. This paper presents a novel accurate displacement measurement method based on imaging technique. The tile patterns existing on the surface of a monitored structure are utilized to measure the displacement distribution through the sampling Moiré method. In our proposed method, the displacement is calculated from the components of both fundamental and higher frequencies of the Fourier series of the tile patterns. Compared with the conventional sampling Moiré method where only the fundamental frequency component is considered, the developed method features high-resolution, accurate, fast, low-cost, and being easy to implement. The principle of in-plane displacement measurement method is presented. The effectiveness of this method was confirmed by displacement experiments performed in both indoor and outdoor. The displacement distribution with an accuracy of sub-millimeter could be evaluated from the picture taken more than 20 meters away from the measuring object.