Damage detection in structures by modal vibration characterization

A nondestructive methodology is presented for detecting structural damage i n structural systems. The procedure is based on using experimentally measur ed modes and frequencies in conjunction with vibratory residual forces and a weighted sensitivity analysis to estimate the extent of mass and/or stiff ness variations in a structural system. Determination of the residual force s and weighted sensitivity analysis involves the use of an analytical model that is correlated to the experimental baseline data from a reference stat e. This reference state defines the undamaged structural configuration. The method is demonstrated by using a ten-bay space truss as an experimental t est bed for various damage scenarios. The experimental results show that th e method can accurately predict the location and severity of stiffness chan ge as well as any change in mass for different damage scenarios. The use of an analytical model that is correlated to the baseline test data is shown to improve the prediction; however, reasonable results are also obtained us ing an uncorrelated analytical model.