Damage assessment of the historical Széchenyi Chain Bridge

The Széchenyi Chain Bridge is a 170-year-old historical structure located in the downtown of Budapest. The superstructure of the bridge was reconstructed several times in its history and currently the renewal process of the bridge is under consideration. According to the current plans main girders, chain elements and cross-girders will remain the old structure and the deck system will be replaced by a new orthotropic steel deck. The Budapest University of Technology and Economics, Department of Structural Engineering was involved in the design process and in the assessment of the remaining elements’ condition within the last 5 years. During the project authors were faced with numerous specific important and challenging structural problems, modelling specialties, advanced design methods and research interest. The main part of these unusual characteristics come from the layout of the historical structure, long time traffic and corrosion problems. One of the most important questions during the structural analysis is the condition and rotational capacity of the pins between the chain elements. The chain system is more than 100 years old and the rotational capacity of the pins is questionable due to corrosion and friction. This phenomenon significantly influences the static behaviour of the chain elements and the whole suspending system. The current paper presents the numerical and on-site experimental program on the investigation of the rotational capacity of the pins. A second important question was related to the condition of current deck system. Significant corrosion damage was observed on the steel stringers which might cause damage or local collapse of the bridge deck under public transportation loads. Advanced numerical model using probabilistic analysis (FORM) and measurement based corrosion models are applied to make a risk assessment of the deck system's capability to maintain and keep the current traffic on the bridge before the deck will be replaced. Via this bridge inspection and investigation project the authors would like to demonstrate the application of advanced numerical modelling based design techniques and the industrial application of research models for lifetime assessment and risk analysis of historical structures.