Direct Index Method of Damage Degree Identification Based on Local Strain Mode Shape Area of Damage Structure

The vibrotechnique may be applied to damage identification in civil engineering, but there are some technical problems. The identification precision of displacement mode shape is low; however it of strain mode shape is high. Although the present methods of strain modal parameters can be applied to detect damage location, only very few can rough detect damage degree. Furthermore, the precondition of the methods is that the modal parameters of original structure and damage structure must be obtained. It is very difficult for the original structure. Therefore, the direct index method of damage degree identification (the abbreviation is

I

LSMSA

) is advanced in the paper. It is based on local strain mode shape area of the damage structure. The strain modal parameters of original structure needn't be provided. The polynomial is applied to fit strain mode shape of the original structure. The mathematics models of optimization polynomial degree and

I

LSMSA

are founded. According to theoretical derivation and statistical analysis of numerical simulations, the four characteristics of

I

LSMSA

are obtained. First,

I

LSMSA

presents monotone increasing tendency with increasing damage degree. Secondly, it is independent of damage location. Thirdly, it is independent of the order of strain mode shape. Fourth, it is independent of normalization.