Condition and damage assessment: Issues and some promising indices

Critical issues related to damage and condition assessment are discussed. The distinction between global and local state properties, linearized and nonlinear condition indices and experimental constraints are discussed along with a classification of condition assessment techniques. Brief examples from research results on steel stringer highway bridges and a long span bridge are presented in order to exemplify the interrelation between structural condition, damage, and some of the promising damage indices. The indices that are discussed in this paper are influence coefficients for displacement and strain, and redistribution of intrinsic strains measured by continuous long term monitoring. A discussion of these indices is introduced with application examples from the bridges, which were utilized as a test bed to evaluate the applicability of the indices. Tools and technologies for successful measurement of influence coefficients are presented. It is shown that if a spectrum of appropriate experiments and indices are integrated within a structural identification framework, and the structure is monitored for a sufficiently long time, it is possible to accomplish successful condition and damage assessment.