The World Trade Center in New York (WTC) was attacked by terrorists twice, in 1993 and 2001. In the latter case, it collapsed. In the first case on February 26, 1993, a survey was conducted holding interviews with Japanese business people. The testimonies are analyzed according to the number of occupants, occupants°« awareness of the emergency, pre-escape behaviors, behavior in the stairs, and escape time. In the second case on September 11, 2001, survivors°« stories were collected from the Internet. The remarkable and common event found in two disasters is heavy congestion in the stairs. This paper aims to study measures for life safety design to future tall buildings focusing on a heavy congestion in the stairs caused by simultaneous escape in the whole building. In analyzing a simultaneous escape, it is necessary to deal it with a dynamic method, as human flow in stairs is a feedback system. Analyses of WTC escape standing on the same position are reported by NIST . The fluid model in this paper was carried out prior to NIST studies and demonstrated necessity of dynamic analysis.
Keywords: tall buildings, World Trade Center, escape simulation, simultaneous evacuation, phased evacuation, fluid model