A strain modal flexibility method to multiple slight damage localization combined with a data fusion technique

Abstract The localization of multiple slight damage in engineering structure is very important and difficult in structural health monitoring. Slight damage in engineering structure will result in small variation of the modal parameters such as natural frequencies and mode shapes (also called displacement modes). Many of the methods based on displacement modes, such as flexibility approach, are insensitive to slight damage, and thus may fail to accurately locate the slight damage. Strain is the derivative of displacement and thus a slight variation in displacement data will be amplified by the differential process, resulting in a significant variation in strain modes. Compared with displacement modes, strain modes are claimed to be more sensitive to slight damage. On this premise, a strain modal flexibility method is presented to locate the slight damage. When multiple slight damage appears in a structure, dynamic response of the structure becomes more complex considering the relative position and degrees of damage. A data fusion (DF) technique, which based on Dempster − Shafer’s evidence theory combines information from different data sources, is introduced to improve the efficiency of the damage indicators in locating multiple damage. Thus, a novel method, which utilizes strain modal flexibility method combined with DF technique, is proposed to locate multiple slight damage. Numerical simulations on different steel beam models demonstrate that the proposed method can obtain more accurate results compared with traditional damage localization method. Experimental cases on a steel cantilever beam model verify the effectiveness of the proposed method in locating multiple slight damage.