Point Thermal Transmittance of Rib Intersections in Concrete Sandwich Wall Panels

摘要

Concrete sandwich panels are building elements made by two concrete wythes separated by a layer of lightweight material: the central layer is inhomogeneous due to the presence of concrete ribs which tie the external wythes and act as thermal bridges. This paper deals with the problem of determining point thermal transmittance associated with rib intersections. Together with previous results by the authors, it allows accurate calculation of thermal transmittance of sandwich panels according to current International Standards. A dataset of 1080 point transmittance values is obtained upon use of a spectral element method, varying systematically material conductivities and thickness of panel layers, for the most common pairs of rib widths in current panel production. To limit the computational cost, a solution strategy based on the use of low-order polynomials on three grids of increasing refinement, coupled with Richardson extrapolation is adopted. Finally, a power law correlation is proposed that allows to estimate point transmittance within a relative error of 10%.