Brandteknisk dimensionering av limträkonstruktioner : En jämförelse mellan förenklad och analytisk dimensionering med avseende på materialåtgång

Sammanfattning: This thesis examines the possibility of saving material by using analytical design of fire protection of glued laminated timber structures instead of the standard simplified design approach. The thesis is based on an existing store building (building class Br2 and occupancy class 2B) where Tyréns AB has determined a fire exposure specific for the store building, which is used to simulate 30 minutes of fire. The result from the simulation is then used in this thesis to evaluate the effects of said fire on a glued laminated timber structure. The analysis results in the assumption of a laterignition, since the temperature development varies from the standard fire curve used in thesimplified design approach. The thesis consists of several steps. First a glued laminated timber structure consisting of a column and beam system is designed for load bearing capacity in the ultimate and service limit state according to Eurocode. The structure is then verified for accidental actions with fire as the main action according to Eurocode using simplified design. Subsequently the same verification is carried out using the analytical design approach with the specific fire exposure. The columns are not verified since they are assumed to be exposed to direct flame impact and immediate ignition. The columns are also required to be covered with ignition retardant protection according to BBR. The result shows that no saving in material can be obtained for lower fire classes. The main reason for this is the fact that the structure design for load bearing capacity in the ultimate and service limit state is large enough to resist fire for up to 90 minutes without structural failure. For higher fire classes than R90, a potential saving in material can be achieved by using the analytical design approach. This is however deemed irrelevant, since fire classes above R30 are uncommon for these types of buildings.