Dubbelglasfasader och efterlevnad av brandsäkerhetsreglerna Boverkets Byggregler 21 ( BBR 21 )

Double-skin glass façades has gained in popularity and is now a common feature in buildings in both Sweden and throughout the rest of the world. This gives rise to the question about the fire safety of these types of façades as the Swedish building code published by Boverket (Swe: Boverkets byggregler 21, BBR 21) currently does not provide any advice regarding how to fulfill the performance requirements. This thesis attempted to determine how a double-skin glass façade can comply with BBR 21. To limit the extent of the thesis a case study was conducted on the building Skeppshandeln 1, Hammarby Sjöstad, Stockholm, Sweden. As a part of this a literature study of research regarding double-skin façades, and building codes were made. The building codes analyzed were the ones from Sweden, New Zealand and Hong Kong. In addition to this simulations were made on a compartment based on the case study using Fire Dynamics Simulator (FDS) and an Abaqus analysis of a window with assumed input parameters.The information available for the case study was a floor layout and fire documentation, these were provided by Hifab AB. It was initially believed that detailed information regarding the façade could be accessed but when the information was required it was discovered that it was not available. Due to lack of time it was not possible to obtain sufficiently detailed information regarding the design of these types of façades from other sources.The modeling of the façade in FDS was done in two different ways. The first alternative uses one single obstruction with several surface layers; the second approach uses two obstructions with the material parameters of glass and an air gap between the obstructions. It was also attempted to model the façade using Lagrangian particles but this was unsuccessful due to how these function in FDS.The conclusions that could be drawn from the literature study is that although certain elements in the BBR 21 will also apply to double-skin glass façades there are uncertainties regarding the external glass and the air gap. Previous research and the building codes from New Zealand and Hong Kong provide some solutions to managing the air gap but these may contradict BBR 21. Specifically BBR 21 specifies that the amount of debris shall be limited whereas these façade solutions according to the building codes in New Zealand and Hong Kong require breaking the external window which will cause debris to fall down. The temperature analysis of the results from FDS indicate that in this specific case the façade design has to take into account that temperatures ranging from 800⁰C to approximately 950⁰C may occur in a fire situation. This does not take into account that there is a sprinkler system present in the compartment. These temperatures are highly dependent on whether the fire source is designed as a burner with a peak heat release rate (HRR) or fire load density; the expected temperatures will also vary with the placement of the fuel.The fixing points will be a weak spot in a double skin façade; the highest levels of stress will be located in proximity to these. They will also be required to maintain enough of their load bearing capacity in order to support the window. Due to the relatively high temperatures that are expected in smaller compartments aluminium is likely to be an unsuitable material, the load bearing capacity of aluminium is only 6% of its original value at 350⁰C and the fixing points are expected to be exposed to temperatures above 400 degrees. Due to the limited amount of information available a detailed assessment of a specific façade construction could not be carried out. The thesis did however identify design choices that need to be considered in order to prevent fallout and/or cracking and fire spread inside the façade. The question of whether some of the international solutions for preventing fire spread inside the façade are applicable in Sweden is unclear and requires the attention of Boverket. This thesis should be viewed as a possible example of how a detailed analysis of a double-skin glass façade can be done and it identifies several points of interest regarding fire safety in the design of such façades.Validerat; 20150906 (global_studentproject_submitter