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A simple image-based strain measurement method for measuring the strain fields in an RC-wall experiment



A simple image-based method for measuring plane strain fields on the surface of specimens in earthquake engineering experiments was developed. This method integrated camera calibration, stereo triangulation, image metric rectification and image template matching techniques to develop a method that was cost-effective, easy to apply and provided a satisfactory level of measurement accuracy. A zero-strain test conducted using this method showed that the measurement accuracy achieved was 0.04 pixels. That is, the relative displacement accuracy achieved was 0.005 mm and the strain accuracy was 0.001. This level of accuracy was achieved using eight-mega-pixel digital cameras to measure a 17 cm × 28 cm measurement region. Cracks that were 0.012 mm wide were identified in the concrete by examining the displacement fields calculated through the application of this image-based method in an RC-wall experiment. Copyright © 2011 John Wiley & Sons, Ltd.

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