The impact of a crack existence on the inertial effects of moving forces in thin beams

Presence of crack in the girders of a bridge may significantly change its static and dynamic response, deteriorate its performance, decrease its safety, and eventually lead to its failure. Therefore, it is vital to examine the impact of cracks on the behavior of bridges. To this end, in this paper, the effect of parameters, such as the crack's depth, magnitude and speed of the moving force, and its inertial effects on the dynamic behavior of a simply-supported Euler-Bernoulli beam, representing the bridge girder, are scrutinized. The results are obtained by the Galerkin Method (GM) and Finite Element Method (FEM) and are validated with those achieved by Finite Element Analysis in ANSYS software. Finally, the parameters that affect the dynamic behavior of the cracked beam are normalized and the analyses are performed by adopting the Galerkin Method. The results of this study revealed that in the case of a moving mass, the stiffness reduction due to the presence of a crack has a marginal impact on altering the beam response in comparison with the moving load model. It is also demonstrated, for certain values of the crack's depth, the response of the structure under a moving mass is not always greater than that of a moving load, especially for the relatively large moving forces with high velocities. On the other hand, existence of the cracks is proved to be crucial as it may cause a complete elimination of the inertial effects for some certain values of the moving force weight and velocity. (C) 2020 Elsevier Ltd. All rights reserved.