A modal parameter based technique to inspect welded reinforcement splices

The objective of this study is to investigate the technical feasibility of using a modal parameter based global nondestructive damage evaluation method to evaluate, quantitatively, welded reinforcement splices during the construction process. For the purpose of this study, an expression which predicts the strength of the weld, in terms of the yield strength of the steel and the effective stiffness change in the weld, is developed. Then, an experiment to nondestructively measure the fractional stiffness changes, using changes in modal parameters and a system identification technique, in the welded region of 27 welded reinforcing bars is performed. For comparative purposes, a conventional nondestructive testing (NDT) method, radiographic inspection, and destructive tensile tests are performed to evaluate the accuracy of the nondestructive strength prediction procedure. The predicted strengths of the weld systems, obtained from the strength–damage models and the nondestructively measured fractional stiffness change, are compared with those from the destructive tensile test. Also, areas for potential improvement for field implementation of the methodology are investigated.