Performance assessment of stairwell smoke prevention techniques in a model high-rise building

Abstract

The complexities of construction and increased fuel loading in high-rise buildings implied engineers to shift towards performance-based design (PBD) instead of prescription design to ensure a higher level of fire safety. Since PBD is an iterative process, so engineering models and tools based on numerical techniques are generally used to evaluate the trial designs. In the present study, various methods of stairwell smoke prevention have been analysed and compared using Fire Dynamics Simulator (FDS) in a model high-rise building. Optimization is done by defining critical values of smoke layer height and maximum pressure differential as 2 m and 55 Pa, respectively. Results demonstrated that natural and cross ventilation in the stairwell are not fully effective for smoke prevention due to the enhanced stack effect observed in them. Further, the pressurization of stairwell at a minimum differential pressure of 25–30 Pa seems to be effective only when all windows in the stairwell are closed. Effectiveness of single and multiple injection pressurization techniques are also assessed. The single injection system fails to maintain the required pressure differential when multiple doors are opened and causes high-pressure differentials at the top stories. Open windows in the stairwell reduce the effectiveness of the pressurization method. Placing an exhaust duct near windows enhances the effectiveness of the PPV method, even at lower capacities of supply vents, and proves effective when stairwell windows are open by creating a higher stack effect in the exhaust duct. The current research involved a comparative analysis of various stairwell smoke prevention methods, as outlined in NFPA 92 and in accordance with the National Building Code of India. The findings may have broader applicability beyond the studied context.