Estimating extreme values of thermal gradients in concrete structures

Temperature variations due to climate changes are a major cause of movements in a concrete structure, both in the longitudinal and transversal directions and between different parts of the structure. If these movements are restrained, stresses will be induced which may contribute to cracking. The movements are caused by complex interactions of several factors such as solar radiation, air temperature, long-wave heat radiation and wind speed. To predict the varying thermal conditions in a concrete structure a finite element model has been used. A validation of the model has been performed using field measurements in a concrete slab together with climate data from the Swedish Meteorological and Hydrological Institute to be able to use the model for simulations over long time periods and for situations with no available local thermal data. The daily variations in the temperature distribution is captured by the model and it is well suited to be used for estimating extreme values for linear temperature differences based on climate data from meteorological stations. The analyses of extreme values for simulations with longer time periods show that the values for the positive linear temperature gradients in the Eurocode are underestimated for the investigated conditions. There is also a tendency towards geographical differences which has not been included before. An asphalt paving layer increases positive linear temperature gradients while they decrease with a concrete paving