A Structural Damage Index Based on Operational Deflection Shapes

Damage index method for structural damage detection is based on measuring intact and damaged states of the structure and the key assumption is that for the ith mode, the fractional strain energy in the jth element is approximately the same before and after damage. In this method, a damage index is defined and evaluated in each element of the structure based on measured mode shapes. Elements associated withincreased index values are potential damaged regions. In this paper, the traditional method of using few experimentally extracted mode shapes, which are operational deflection shapes at resonance frequencies, is extended to broadband damage index defined in each exciting frequency. Mode shapes are special cases of operational deflection shapes which occur at resonance frequencies. In the proposed method, damage index isbased on all odds in the frequency range of interest rather than only in resonance frequencies. Statistical manipulating the resulting indices makes the damage detection method more promising and robust. A finite element model of a beam has been used to numerically verify the method. Comparative study has been investigated between the proposed and traditional methods. Modal test results of interstate-40 (I-40) bridge over the Rio Grande in Albuquerque, NM, USA have been used to experimentally verify the robustness of the proposed method. The results have beencompared with traditional damage index method ones presented by R. Farrar. Improvement of damage indication via proposed method is evident.

کلیدواژه ها:

Damage Detection ، Frequency Response ، Index