Coupling ventilation and egress analyses to design a safer station

摘要

Egress capacity calculations, like those found in Annex C of the National Fire Protection Association (NFPA) 130 Standard for Fixed Guideway Transit and Passenger Rail Systems are simplistic in that they don't account for the potential that certain egress elements may become untenable in the course of an evacuation. This paper presents a method to enhance the egress calculations by considering the propagation of smoke from a train fire and its effect on egress. This method couples the ventilation and egress analyses to permit the simultaneous study of smoke on egress, and provide station designers insight into producing a safer, more cost-effective or aesthetically pleasing station design. This method utilizes the egress modeling software, STEPS, to model the pedestrian egress movement and the Computational Fluid Dynamics (CFD) software, Fire Dynamic Simulator (FDS), to model the smoke propagation. The smoke propagation information is imported into STEPS and graphically mapped onto the egress elements and the movement of people. The results of this egress analysis show which egress elements may become untenable, and the resulting longer evacuation times due to reduction of egress paths. This enhanced egress analysis was used to demonstrate to one client that costly, visually unappealing downstands would not be required, and that the evacuation criteria could still be met, even if as many as half of the egress paths become untenable during the course of an evacuation.