Rehabilitation assessment of a centenary steel bridge based on modal analysis

This paper presents the ambient vibration tests conducted on a centenary through-truss steel bridge before and after its rehabilitation, with the purpose of evaluating the changes in its dynamic properties as a result of the adopted strengthening strategy. The implemented testing program, experimental setup, data processing and modal identification technique are described. Field data validated numerical models for the analysis of the structural changes produced by the strengthening process are presented. Significant conclusions were drawn by comparing the experimental and numerical results between the pre and post-rehabilitation conditions, namely in what concerns the vibration level experienced by the structure, its stiffness variation and suitability of the adopted modelling methodology. Furthermore, an unexpected coupled behaviour of the simply supported spans that constitute the bridge, translated by a global vibration mode, could even be detected and validated.