Department of Civil Engineering, Sharif University of Technology, Tehran, Iran
The aim of this article is twofold: (1) to provide more insight into the pattern of changes in modal parameters, including natural frequencies and mode shapes, of beams and girders resulting from the increasing of damage level and (2) verification of numerical modelling of the problem using data from experiments on an Aluminum box beam. To this end, first an impact hammer test has been conducted on the 2.6 meter long single span aluminum beam while a progressive damage has been applied at several stages. The modal parameters of the undamaged and damaged beam at different intensities have been extracted and the trend of their changes with respect to the increase in damage level has been studied. Then this process has been simulated numerically by Dynamic Finite Elements Method (DFEM) and the modal parameters have been extracted from numerical simulation. Finally the similarity between the experimental and numerical results has been investigated. The results show that at low levels of damage the modal parameters change very slightly, especially when just a part of the flange has been damaged, but when the damage has been extended to penetrate the beam web, the modal parameters have shown considerable sensitivity to the damage. Also the sensitivity of the different modes to damage has not been the same though relatively good agreement has been observed between the trend of changes in the modal parameters obtained from experimental and numerical studies, except for a number of modal parameters at very extensive damage level.