Structural damage identification using assigned partial eigenstructure

A method of identifying damaged structural elements from measured modal data using an incomplete measurement set is presented. The method uses a mathematical optimization strategy to minimize deviations between measured and analytical modal frequencies and partial mode shapes. Damage is identified by determining the stiffness change to a finite element model required to match the measured data of the damaged structure, Damaged elements are obtained directly from the results of the cost-function minimization because the allowed structural changes are consistent with the original finite element formulation. The cost-function minimization is based on an assigned partial eigenstructure algorithm in which the physical properties of the structural elements are treated as control variables, which are chosen to achieve the measured partial eigenstructure. An iterative solution is used to solve the nonlinear optimization problem. Experimental results are reported for a cantilevered eight-bay truss assembly consisting of 104 elements.