Damage Identification in Long-Span Cable-Stayed Bridges Under Multiple Support Excitations

Multiple support excitations (MSE) have been implemented to investigate their effects on the dynamic response of large-span cable-stayed bridges due to earthquake-related hazards. Different system identification methods including the mode shape curvature method and modal strain energy method have been applied as health monitoring techniques to control the performance of different structural systems and detection of any possible deficiencies. The ABAQUS software was employed for the dynamic analysis of the bridge and the obtained results were utilized to identify the dynamic characteristics of the bridge by applying ''Matlab'' Program. The verified method was used to detect some intentionally induced damages to the considered bridge. An existing coherency function is used to generate the required earthquake inputs to different supports of the bridge. Then, the strain response energy-based method is employed to detect some intentionally induced damages to a considered bridge under the effect of MSE. The results indicate that the strain energy-based method accurately detects the damages in all possible damage modes, and the effect of changes cannot be ignored. Furthermore, the difference in dynamic parameters of the bridge in two modes of single and multiple support excitations is trivial and the difference does not affect the results of the applied methods of health monitoring in this research. Generally, the mode shape curvature method would not be an exact method for detecting damages in the chosen model. Therefore, the energy index based on the acceleration responses method is not an exact method for detecting damages. Finally, the energy index based on the strain responses method is an exact method that detects damages in all possible damage modes, in comparison to other methods. According to obtained results, the maximum shear values at the two end supports of the bridge in the non-uniform excitation case have an average increase of about 25% and for the towers, an average of around 23% increase compared to the uniform excitation case. The maximum displacement of the tower in MSE mode is 33% more than in single support excitations (SSE) mode. When the bridge experiences MSE, the stress in cables has an average of 10% increase.