Prognosis of structural health: Non-destructive methods

For the prognosis of structural health, non-destructive defect assessment procedures are under active development by the profession. Two such procedures now under development by the research team at the University of Arizona, are MILS-UI and GILS-EKF-UI. They indicate a considerable application potential. The unique feature of the algorithms is that they can identify members' properties and in the process access the health of a structural system using only dynamic responses completely ignoring the excitation information. Although mathematically elegant, their practical implemental potential to identify defect-free and defective (single or multiple defects) states need critical evaluation and is discussed in the paper. With the help of an illustrative example, it was shown that both the MILS-UI and GILS-EKF-UI methods can identify defect-free and defective states of a structure very well. Both methods successfully indentified the presence of multiple defects. Ignoring responses at vertical dynamic degrees of freedoms did not alter the outcomes ofthe nondestructive evaluation for the problem under consideration. Both methods also correctly identified less severe defect in terms of loss of area over a finite length. It can be concluded that the methods are capable of identifying small and large defects.