Digital image correlation for dynamic shake table test measurements

The identification of structural and seismic behavior using experimental methods has been the corner stone for investigating the earthquake resistance capability of any types of structures. Traditionally, shake table tests are monitored using LVDT, strain gages, and/or accelerometers that are hooked up to a Data Acquisition system (DAQ). This procedure is usually time-consuming due to instrumentation attachments and setup and the results are usually obtained for limited locations. On the other, Digital Image Correlation (DIC) is a relatively new technology that can be used to provide non-contact full-field measurement. In this paper, the global behavior of a small-scale steel frame structure tested on a small shake table was captured and compared using DIC and conventional DAQ measurements. The objective of this study was to demonstrate the potential application of DIC as a promising measuring technique with high-efficiency and high-accuracy comparable to existing instrumentation techniques for dynamic tests. A free vibration test, as well as earthquake tests using three different ground motions, were conducted and the time histories (displacement, velocity, and acceleration) of the structure were generated by 3D DIC. Two methods of application of DIC were considered: full-field measurements and discrete point tracking. The results from the DIC were compared to conventional instrumentation data collected from the DAQ. The results were very comparable which validated the DIC technology for earthquake shake table measurements.