Crack identification in frame structures

In this paper the problem of crack depth and position identification in frame structures is examined, using eigenfrequency measurements. It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the crack size and position. The basic idea is to present in contour graph form the dependency of the first two structural eigenfrequencies on crack depth and location, using the finite element method. To identify the location and depth of a crack in a frame structure, one only needs to determine the intersecting point of the superposed contours that correspond to the measured eigenfrequency variations caused by the crack presence. A number of beam and frame examples are included in the present paper to verify the applicability of this combined computational-graphical or experimental-graphical method. (C) 1997 Civil-Comp Ltd and Elsevier Science Ltd.