Development of a modal based bridge monitoring system

In recent years, the interest in modal based monitoring systems, especially for bridge constructions, has increased significantly. The aim is to detect damage processes at an early stage and to extend the service life of existing bridges and to minimize maintenance costs. The modal parameters, natural frequencies and mode shapes, are global parameters that depend on the stiffness and mass distribution of the structure. Assuming that damage processes are accompanied by a decrease in stiffness, they allow the detection and localization of damaged areas of a structure. In the context of this paper, laboratory tests are presented, in which the sensitivity of the modal parameters to increasing crack formation was investigated. In addition, the pre-damaged reinforced concrete beams were strengthened with externally bonded carbon fiber reinforced polymer (CFRP) laminates and subsequently loaded until failure. A high sensitivity of the modal parameters with respect to increasing crack formation can be detected. Moreover, the effect of the amplification system can be successfully proven by means of the modal parameters.