Equivalent thermal conductivity of steel girders with slotted web

Lightweight building methods are spreading all over the world from the Scandinavian countries and North America and can also be seen more often in Hungary. One of the areas of this building method is a façade containing thin-walled slotted steel girders, called as thermal studs, also. Due to the slots in the web there is an increased heat path length inside the steel elements, so the heat bridges caused by the framing will be less, compared to the case of a standard geometry of the solid ones. Research has been carried out in the past decades in the development of this wall system. One approach was to investigate the building physics properties (thermal and vapour transmittance, fire protection, acoustics). This paper presents the calculation method of the equivalent thermal conductivity of the slotted webs of the steel girders. Simulations were carried out with the computational programmes ANSYS 11.0 and HEAT3 5.0. To check the validity of the thermal conductivities, wall sections containing slotted steel g irders were simulated by using either the original slotted elements and after it the equivalent section. The comparison of the models shows good agreement between the original slotted girder and the equivalent solid sections. Special perforation geometries were also developed to achieve a better thermal performance.