This study aims to analyze the effect of variations in elevator shaft size on smoke propagation in high-rise buildings and to provide design-based evidence for securing evacuation safety within elevator lobbies. High-rise buildings have become a repre...
This study aims to analyze the effect of variations in elevator shaft size on smoke propagation in high-rise buildings and to provide design-based evidence for securing evacuation safety within elevator lobbies. High-rise buildings have become a representative architectural form for efficient land use in dense urban environments; however, during a fire, vertical smoke movement through elevator shafts poses a significant threat to human safety.
To investigate this phenomenon, fire simulations were conducted using the Fire Dynamics Simulator (FDS), a computational fluid dynamics (CFD)-based program. Both single and parallel elevator shafts were modeled to reflect realistic building geometry and boundary conditions. Key parameters, including shaft cross-sectional area and leakage gap size, were systematically varied to examine their effects on smoke propagation and the Available Safe Egress Time (ASET). All simulations were performed under identical fire growth rate (t² fire), ventilation, and fuel composition conditions to ensure comparative consistency.
For the single-shaft configuration, the analysis revealed that changes in shaft size did not exhibit a simple linear relationship with ASET. At lower levels, smoke infiltration had a relatively greater influence, whereas at upper levels, the dilution effect from increased shaft volume produced nonlinear characteristics.
Beyond a certain threshold, enlargement of the shaft cross-section was found to be a dominant factor affecting the improvement of evacuation time.
In the parallel-shaft configuration, although the total cross-sectional area was larger, the leakage area was also approximately twice that of the single-shaft model, resulting in generally shorter ASET values. Comparative analysis of width (W) and depth (D) variations indicated that width expansion had a limited effect on ASET improvement, whereas increasing the shaft depth effectively delayed smoke propagation to upper floors.
Finally, when the leakage gap area of the parallel-shaft model was reduced by half, the ASET improved significantly by approximately 58–65%, demonstrating that the reduced evacuation performance of parallel shafts is primarily governed by the extent of air leakage.
These results confirm that the shaft cross-sectional size, elevator
arrangement, and leakage gap conditions are decisive factors influencing smoke propagation behavior in high-rise buildings. This study provides practical data for determining the appropriate shaft dimensions and for establishing smoke control and pressurization strategies in the design of elevator shafts.
Furthermore, it is expected to serve as a foundational reference for improving evacuation safety performance in performance-based fire design (PBD)
applications for high-rise buildings.