Numerical Simulation of Fire Spreading in a Steel Skeleton-Drywall System Building

Fire protection systems in buildings are commonly regulated using prescriptive-based codes and standards, which exhibit small flexibility for innovative solutions and cost-effective designs. Performance-based fire safety design can alleviate such restrictions and several countries have started to adopt such methodologies in the recent years. In this context, the utilization of Computational Fluid Dynamics (CFD) tools to accurately describe the fire and its impact on buildings and people is gaining significant momentum in the fire safety engineering community. In this work, a CFD tool is used to study the thermal behaviour of a two-storey residential house subjected to a typical domestic fire scenario. The building comprises a steel-skeleton with drywall systems as partitions and external cladding; the walls consist of multiple layers of plasterboard and insulation materials. When plasterboard is subjected to a high temperature environment, water molecules bound in its crystal lattice are released; this “dehydration” process is expected to enhance the building’s fire resistance. The Fire Dynamic Simulator code is used to simulate the momentum-, heat- and mass-transfer phenomena occurring inside the building during the fire. The Large Eddy Simulation concept together with a mixture-fraction model are used to describe the developing reactive turbulent flow and the combustion phenomena, respectively. The physical properties of the utilized multi-layered building components are taken into account in the simulations to accurately describe their thermal response; the highly detailed computational geometry is based on actual architectural drawings. Numerical predictions of the temporal evolution of a range of fire safety related quantities, such as gas velocity, gas- and wall-temperatures and toxic gas concentrations are obtained for the entire 3-dimensional domain that represents the interior of the building. Gas velocity and temperature predictions are used to visualize the developing flow-field and to estimate the heat flux to which each building element is exposed. Predicted wall temperatures allow the assessment of the investigated type of building in terms of fire resistance. Finally, gas temperature and toxic gas concentration predictions enable risk assessment for the tenants of the building in the event of a fire.