International Journal of Engineering and Technology

The concession period of man-made structures is limited and not eternal under any circumstances. Various internal and external factors cause the components of the structure to be damaged and the structure to be in serious trouble and even completely destroyed under the service load. The identification of damage to a structure has become a matter of interest to many researchers in recent decades, because catastrophic destruction of structures can be prevented by early damage detection. In addition, the service life of the structures can be increased if the defects and damages are timely eliminated. In present study, the damage to a cantilever beam constructed in the laboratory is detected based on the data from frequency response function. To do this, changes in the stiffness and natural frequencies of a structure are considered as factors in searching for a damage to the beam. The present study is carried out in two empirical and analytical phases. In the empirical phase, a physical model of cantilever beam is developed according to the requirements for damage detection. Then, the modal testing is planned to obtain the empirical frequency response functions of the cantilever beam. In the analytical phase, damage is detected using a finite element model of cantilever beam and considering the damage as a vector (including position and intensity of damage) in the cantilever beam element stiffness matrix as well as solving an optimization problem using a genetics algorithm. After conducting modal analysis on a healthy and damaged beams and obtaining frequency response functions, a finite element model updating is performed to consider the behavior of the frame connected to the cantilever beam. It can be seen that the program written in the theoretical phase of damage detection is very accurate so that it can detects damage at several points and at different intensities. In the empirical phase, damage detection is presented in a sample damaged at one point and the program is able to accurately detect the position and intensity of the damage. In the scenario of being damaged at two different points, in addition to the detection of damaged elements, the method considers a small percentage of damage for the healthy elements. In general, the proposed method is an accurate and appropriate method for detecting the damage to the cantilever beams.