Climatic Thermal Stresses in the Vätösund Box-Girder Concrete Bridge

Severe cracks have been found in several box-girder bridges in Sweden, with the cracks being more frequent on the south side than the north. This indicates that solar radiation has a large impact on the stress field of these bridges, since this is the only factor that is significantly different between the walls. In this study the Vätösund Bridge has been modelled in a 3D FE-model to analyse the thermal stresses that occur due to climatic exposure. Meteorological data have been used to simulate the time variation of the temperature field, which is in turn used to simulate the resulting thermal stresses. The results show that the largest tensile stresses appear on the inside of the south wall, with a clear difference compared to the north. Large stresses appear both in the top and in the bottom parts of the south wall; this indicates that the cracks, which mainly appeared in the lower parts, at least partly originates from thermal effects. The boundary conditions at mid span have a large impact on the location and magnitude of the thermal tensile stresses. The results show that it is possible to predict where thermal stresses appear in a box-girder bridge using 3D FE-analysis