Dynamic response of a steel arch bridge due to traffic load : A CASE STUDY OF VÄSTERBRON

Sammanfattning: The purpose of this master thesis was to study the dynamic response of the bridge Västerbron. The bridge is situated in Stockholm and is considered being of critical significance for the infrastructure. The thesis consists of both field measurements and analyses of a finite element model. A stochastic load model was created that is intended to simulate different realistic traffic situations based on parameters as velocity, vehicle type and amount of traffic. The traffic load model was implemented in a finite element model to study if the response was similar to the measurements. With comparisons of the dynamic properties the validity of the model can be assessed. Parameters as stiffness, mass and boundary conditions also often needs to be updated to describe the real behaviour of the bridge. With these updates a model can be created that could better predict problematic behaviour as fatigue. The field measurements were made with accelerometers and analysed in Matlab. The stochastic load model is also scripted in this environment. The FE-model was created using Python scripts that were implemented in BRIGADE/Plus. No conclusive results regarding the mode shapes of Västerbron could be found, however possible eigenfrequencies were identified and presented. The load model was implemented in the FE-model and the influence of different parameters were discussed. The results were consistent with structural dynamics theory and in the same order of magnitude as the measurements. This implies that the traffic load model can be used for further studies regarding dynamic analyses.