Damage detection based on damage force indicator using reduced-order FE models

Damage measures, one of the important parameters in Structural Health Monitoring (SHM), and useful in detecting the presence and location of cracks in beams, are developed in this article. This development is based on the reduced Finite element models for healthy and damaged structures. Finite element reduced-order model (ROM) methods like static condensation, system equivalent reduction expansion process (SEREP) and dynamic condensation have been used to generate reduced order models. ROM generated by static condensation are used to analyze beams under static loading while SEREP and dynamic condensation methods are used for dynamic loading. The developed damage measure is the force residue obtained from the stiffness relationship of healthy and damaged beam, which we call damage force indicator (DFI). For dynamic load cases, the measure is evaluated in the frequency domain. Sensitivity of orientation of crack prediction is performed by using different orientations of crack and comparing it with a crack of standard orientation. A general method to determine the approximate region of damage for a structure with no a priori knowledge of damage is also explained. Damage measures are verified using experimentally measured responses, to prove the efficiency of the approach