Finite element simulation of a pre-stressed concrete girder bridge : influences of construction stages and ground settlements on Gruvbron in Kiruna

• Main Author: Galí Isus, Antoni
• Format: Bachelor Thesis
• Language: English
• Published: 2009
• Subjects: Technology; bridges; finite element method; rock; settlements; soil; Teknik; Kiruna; Kirunavaara; Luleå
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-48850

The railway line in Kiruna is planed to be moved before year 2012 due to expected cracking in the underlying rock. The cracking is initiated by the mining in the Kirunavaara-mine. The cracking is expected to cause increasing ground motions that affect the whole infrastructure in Kiruna. For one of the bridges, The Mine Bridge (Gruvvägsviadukten), settlements are expected in the future. Initially at its west side and further eastwards towards the city. An early assessment of the bridge showed that the bridge has enough load-carrying capacity but that the length of the reinforcement close to the interior columns probably is a little bit too short to fully compensate the prestressing force in top of the concrete girder. A certain worry has been expressed that the ground movements may cause some existing cracks to propagate upwards to the girders top i.e. that the cracks goes through the whole girder which may reduce the shear capacity remarkable. Luleå University of Technology is asked to perform a more thoroughly study of the bridge's capacity to resist different scenarios of settlements. This thesis is a part of the work and deals with non-linear finite element modelling and analysis of the bridge's capacity to resist the settlements and to evaluate limits for certain expected scenarios of settlements. To confirm the correctness of the final model, the displacements from the model is compared to measured displacement for a known truck load. The comparison shows that the model is somewhat weaker than in the reality. This is believed to depend mainly on a generalization of the deck's geometry and a stiffer construction during the field measurement. However, the model is still judge to be usable for studying what limits can be used for allowed settlements and the reason for why some cracks already exists. It is found that the most serious failure that can be expected is compression in bottom of the longitudinal girder, in middle of the considered span. This appears at a 25 mm settlement of the interior column raw in ...