Residual displacement and residual strain measurement for steel frame under seismic load by integrated dot centroid tracking method

Abstract

The applicability of the image-based method for residual displacement and strain measurement in a structure which is damaged by seismic load was experimentally investigated. A specimen of steel frame was constructed and was subjected to seismic excitation in one direction. Residual displacement and strain field in a beam-to-column connection which suffered from seismic load was measured by Integrated Dot Centroid Tracking (IDCT) method which is one of the image-based methods. A statistical processing result showed the measurement was achieved with a smaller resolution than residual displacement under a minimum seismic load case. The residual displacement due to local tensile and shear force explained with the deformed triangular mesh which made by the centroids of dots. As a comparison with other measurement methods, an elongation between two centroids of dots on beam and column was compared using a displacement transducer installed inside the beam. The measurement result by the displacement transducer validated compared with a calculated displacement waveform using acceleration. As the number of measurements is increased, both measurement results showed a tendency to increase. Differences of residual displacement by two types measuring method was within 15–20%. The series of experiment in this study revealed the applicability of measurement for real structure using IDCT method.