Modal displacement vs Curvature functions as damage identifier for masonry structures

Identification of crack location and severity is a vital step in assessment of deteriorated structures. The current research addresses the sensitivity of using modal displacement, modal curvature, and modal strain energy functions as Damage Indices (D.I.s) for crack detection. Comparison of these indicators at cracked and undamaged conditions was performed. Firstly, Damage Index (D.I.) method was utilized on synthetic data obtained with the aid of finite element modelling on different flexural elements. The technique was again used to identify cracks for physical scaled-down masonry walls. Three clayey bricks walls with different thicknesses and crack configurations were prepared for this purpose. Each wall was tested in its virgin and damaged states. Formal modal analysis was conducted. It was concluded that all the used D.I.s were accepted as damage indicators. It can also be stated that the relative severity between cracks can be obtained. Numerically, D.I. method was found effective in cases of multiple or inclined cracks. Generally, the identification based on curvature functions, were better than displacement functions for the same number of monitoring points and crack severity. Curvature can’t, however, be easily obtained for sophisticated structures with limited data. Moreover, the detection process became easier as the crack dimensions increased.