Noncontact deflection distribution measurement for large-scale structures by advanced image processing technique

Ambient unexpected vibration in field experiment for large-scale structures is an essential problem to perform highly accurate displacement measurement. In this paper, an advanced image processing (AIP) technique combining the sampling moiré method and digital image correlation (DIC) method is developed for noncontact measuring deflection distribution of large-scale structures. This technique has demonstrated promising results in both laboratory and field experiments. Experimental results in laboratory show that the artificial vibration can be abated remarkably by DIC using a subset image of background without loading. Experimental results in field show that AIP technique can successfully measure the displacement distribution of a long crane with sub-millimeter deflection under natural vibration environment. The most attractive advantage of AIP technique is only each single image is required before and after deformation. This indicates the noncontact deflection distribution measurement is possible with high resolution and high accuracy by ease setup for the dynamic structural evaluation of infrastructures.