Detection of damage in beams subjected to diffused cracking

This paper addresses the problem of identifying structural damage affecting one zone of a beam using measured frequencies. The beam model has a zone in which the stiffness is lower than the undamaged value. Damage is defined by three parameters: position, extension and degree, which need to be identified in the inverse problem. The solution of the direct problem is first obtained and the peculiarities of damage detection are examined. Two different procedures for damage identification are proposed, which use frequency measurements and take advantage of the peculiarities of the problem: the first procedure is based on the characteristic equation error and the second on the comparison between analytical and experimental frequency values. The identifiability and ill-conditioning properties are discussed by referring to cases with pseudo-experimental data. (C) 2000 Academic Press.