Non-contact measurement of inter-story drift in three-layer RC structure under seismic vibration using digital image correlation

Abstract Earthquakes can cause the unexpected failure of buildings and other structures, and numerous experimental methods have been devised to estimate structural integrity and the likelihood of failure. Unfortunately, the retrofitting of old structures by attaching sensors within walls and columns can be prohibitively expensive, and the analysis of signals obtained from hundreds of devices is time-consuming. In this paper, we introduce a proprietary program based on digital image correlation (DIC) for the measurement of inter-story drift in reinforced concrete structures exposed to seismic vibrations. Inter-story drift refers to translational and angular displacement between floors. We applied the proposed DIC program to the measurement of biaxial deformation and probed inter-story drift in a three-layer structure under the effects of seismic waves. Theoretical modeling, experimental measurements, and numerical analysis were used to verify the accuracy of the measured results as well as the structural performance of the deformed structure. Our DIC results are consistent with those obtained using the infra-red motion capture system, linear variable differential transformers, and accelerometers. The proposed DIC metrology enables the simultaneous observation of displacement, acceleration, and drift angle. The ability to perform non-contact inspection and remote measurement makes this scheme applicable to the long-term monitoring of structural performance under seismic vibration. All associated analysis based on frequency spectra using the fast Fourier transform and short-time Fourier transform can be performed using an inexpensive digital camera and a laptop computer, thereby allowing the in-situ monitoring of structural performance under seismic vibration. The experimental setup of the DIC system takes only a few minutes, and the vision-based metrology can track registered patterns from a remote location. Compared with wired sensors, the DIC system provides a more prolonged and safer distance for observing the inter-layer drift of the RC structure under the reproduced TCU052 earthquake. Compared with an OptiTrack system, the DIC system is portable and can cooperate with a universal combination of optical lens, digital camera, and laptop computer. The accuracy and efficiency of the proposed scheme enable the rapid diagnosis of structures affected by earthquakes, while reducing the costs associated with post-earthquake estimates of damage.