Modeling of temperature variations and response in a mining road bridge in Kiruna

University essay from Lunds universitet/Avdelningen för Konstruktionsteknik

Abstract: This thesis treats a concrete bridge located in Kiruna, in the north of Sweden, which was used for the mining industry. A finite element model has been created with the finite element software Abaqus to find out if it accurately can describe the variation of the temperature and deformation within the bridge over time. The temperature variations and deformations have been studied with respect to climate effects. The climate is complex and affects the temperature within the bridge in different ways. During daytime the bridge is exposed to radiation from the sun and the air temperature which is relatively high during the studied time period. During the night the bridge will cool down due to outgoing longwave radiation and the absence of the sun. The temperature in the bridge is also affected by convection mainly caused by wind. The used finite element model has previously been verified for two-dimensional temperature variation in concrete structures without overhangs. In this work the temperature variation will be studied in a cross section of the bridge using a two-dimensional model including overhang and paving layer. The temperature variation was studied for June 2009, August 2010, and a short period during June 2014. The strain was studied in a three dimensional model for June 2009. The finite element model calculates the temperature variations within a structure based on climate input data. This data consists of hourly values of air temperature, long wave radiation and global radiation. The temperature input data was received from the Swedish Meteorological and Hydrological Institute which have weather stations placed across Sweden. The temperature variations lead to deformations. An increase in temperature will force the concrete to expand, and a decrease in temperature will force the concrete to contract. The modelled deformations within the structure are also affected by how the supports are modelled and the choice of material properties. After calculating the temperature variations it is possible to calculate the deformations based on the temperature calculation results. The temperature- and deformation results were compared to measurements from temperature and strain gauges by M.Sc. Niklas Bagge and his co-workers from Luleå Technical University. The results show that the 2D temperature model captures the temperature variation very well. Further the results show that the 3D strain model captures the strain variation fairly well and the 2D strain model shows unreliable results.

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