Strain-based approaches to damage localization in civil structures

Despite the recent increase in the scientific literature on new vibration-based damage location techniques, it is commonly recognized that only methods that use mode-shape information are proven to be effective in Structural Health Monitoring of civil structures. Mere comparison of the modal shapes of a structure in the pre- and postdamage situations does not usually yield results useful for locating the damage, so the mode-shape information needs to be rearranged in a more appropriate form. The most common approaches proposed in the literature are based on concepts such as strain mode shape, flexibility matrix, Damage Locating Vectors (DLV), strain energy. In this contribution the authors show how the theoretical basis of most of the techniques proposed in the literature can be easily compared when the mechanical problem is recast in a generalized-strain coordinate system. The possibilities and limits of these approaches are first highlighted with simple numerical examples. The methods are then applied to the damage location in an experimental prototype of instrumented beam.