Modeling pre-evacuation delay by evacuees in World Trade Center Towers 1 and 2 on September 11, 2001: A revisit using regression analysis

We have tested a linear regression model to identify significant predictors of pre-evacuation delay in a sample of evacuees enrolled in the World Trade Center Evacuation Study. We have found that pre-evacuation delay was greater when there were more environmental cues, more seeking out of information, and more pre-evacuation actions. Additionally, higher perceived risk was predictive of shorter pre-evacuation delay times. These findings are compared and contrasted with an analysis of participants in the National Institute of Standards and Technology investigation of the World Trade Center disaster, recently reported by Kuligowski and Mileti (2009). Both studies reported factors associated with pre-evacuation delay that were similar to those associated with community evacuation. Additionally, we found that greater knowledge and greater emergency preparedness were associated with greater perception of risk. Greater emergency preparedness was negatively related to pre-evacuation delay within World Trade Center Tower I, but within World Trade Center Tower II, the relation between emergency preparedness and pre-evacuation delay was positive. These findings have implications for training of occupants of high-rise buildings.     

Modeling the Evacuation of the World Trade Center Towers on September 11, 2001

Multiple evacuation models were used to simulate different WTC tower evacuations, subject to a number of assumptions. The goal of the modeling was to frame an understanding of actual evacuation findings on September 11, 2001. Simulations demonstrated that a phased evacuation (occupants of the emergency floor, the occupants on the floor above, and the occupants on the floor below were to evacuate to three floors below the emergency floor) would have taken between 4 min to complete (without delays in evacuation initiation) and 11 min to complete (with evacuation initiation delays between 0 min and 10 min). Total evacuation of a tower assuming a full occupant load would have required from 92 min to 142 min. NIST estimated that approximately 14,000 occupants would have been unable to evacuate from WTC 1 and WTC 2 on September 11, 2001 had the starting building population in each tower been 19,800, i.e., a full occupant load without visitors.     

Analysis of the Evacuation of the World Trade Center Towers on September 11, 2001

This paper provides an analysis of the evacuation of the World Trade Center towers culled from telephone and face-to-face interviews with survivors. The first investigation explored where occupants were located when each tower was attacked. Regression analysis explored the sources of variance in occupants’ time to reach the stairwell, as well as stairwell evacuation time (how long the average occupant spent in the stairwells per floor). Finally, issues identified as contributing to either slowing or aiding the evacuation process were also explored.     

A study of evacuation behavior in the World Trade Center explosion

This paper is an analysis of five interviews conducted after the World Trade Center explosion on February 26, 1993, in New York City. Five people who were among those evacuated from the towers reported their experiences. The testimonies were analyzed according to the number of evacuees, occupants' awareness and knowledge of the emergency, behavior until egress, behavior in stairways, reverse flow of evacuees, and time to egress. According to the study, characteristics of human behavior become apparent in mass and simultaneous egress.     

美国纽约世界贸易中心主楼倒塌原因初探

介绍了纽约世界贸易中心主楼的结构体系概况 ,从撞击、燃烧和连接几个方面对该建筑遭 9 11受撞击后倒塌的原因进行了分析 ,并建议在设计城市标志性超高层建筑时适当考虑飞机撞击这种偶然荷载的作用     

美国纽约世界贸易中心大楼事故分析与反思

美国纽约世界贸易中心座落在纽约曼哈顿岛南部,是纽约中心的标志.该工程为姐妹塔楼,地下6层,地上110层,高417m,标准层平面尺寸63.5m×63.5m,每幢楼建筑面积41.8×104m2,整个大楼可容纳5万人工作,采用外筒结构体系,建于1973年,每幢楼总用钢量7 800t.在2001年9月11日两架飞机分别撞进北大...     

Overview of Major Studies on the Evacuation of World Trade Center Buildings 1 and 2 on 9/11

Following the attacks on the World Trade Center in New York City on September 11, 2001, several large studies were undertaken to look at the evacuation. The studies began from 18 months to 4 years after the event, and although there were similarities in the data sets collected in these studies, each set out to answer or contribute to a somewhat different purpose—investigation into the collapse of the towers, emergency preparedness in the workplace, and enhancements in the computer simulation of the evacuation of high-rise buildings. The studies used a variety of data collection techniques. This paper briefly describes the studies, their study populations, summary findings and long-term impacts.     

The UK 9/11 evacuation study: Analysis of survivors’ recognition and response phase in WTC1

The September 11th 2001 impact on the World Trade Centre (WTC) resulted in one of the most significant evacuations of a high-rise building in modern times. The UK High-rise Evacuation Evaluation Database (HEED) study aimed to capture and collate the experiences and behaviours of WTC evacuees in a database, which would facilitate and encourage future research, which in turn would influence the design construction and use of safer built environments. A data elicitation tool designed for the purpose comprised a pre-interview questionnaire followed by a one-to-one interview protocol consisting of free-flow narratives and semi-structured interviews of WTC evacuees. This paper, which is one in a series dealing with issues relating to the successful evacuations of towers 1 and 2, focuses on cue recognition and response patterns within WTC1. Results are presented by vertical floor clusters and include information regarding cues experienced, activities prior and subsequent to occupants first becoming aware that something was wrong, perceived personal risk, time taken to respond and the inter-relationships between them. The results indicate differences in occupant activities across the floor clusters and suggest that these differences can be explained in terms of the perception of risk and the nature and extent of cues received by the participants.     

Reconstruction of the Fires and Thermal Environment in World Trade Center Buildings 1, 2, and 7

The National Institute of Standards and Technology (NIST) conducted an extensive investigation of the collapse of the three tall World Trade Center (WTC) buildings. A central part of this investigation was the reconstruction and understanding of the initiation and spread of the fires. This paper describes the reconstruction of the fires, the thermal environment they created within the buildings, and the raising of the temperatures of the structural components. NIST analyzed thousands of documents, interviews, photographs, and videos to obtain information on the layout of the floors and the progress of the fires. Experiments provided information on the factors likely to have determined the fire growth. Simulations using the Fire Dynamics Simulator gave good agreement with the fire spread as observed at the windows. Imposition of the probable thermal environment on the structural steel produced maps of the probable temperature profile of the steel as the fires progressed. For WTC 1 and WTC 2, even in the vicinity of the fires, it was unlikely that the columns and floor trusses with intact insulation heated to temperatures where significant loss of strength occurred. This was in part due to the short time between aircraft impact and building collapse. There were regions of the towers in which the loss of structural strength of floors and columns, whose insulation had been damaged by aircraft impact, was likely. For WTC 7, even though the insulation was intact, the long periods of heating resulted in floor components whose temperatures exceeded 600°C, but columns did not exceed 300°C.     

世界遗产整体性保护与旅游开发研究--以皖南黟县宏村为例

旅游开发在一定程度上带动了宏村经济发展,同时也带来了宏村整体风貌遭受建设性破坏,游览景点的保护和修缮缺乏整体性等负面影响。宏村遗产的整体性保护规划力求保持古村落格局及空间形态,旅游开发以遗产保护为前提,增设景点,延长旅游线路,正确预测游客量,以实现遗产保护与旅游业的“双赢”与可持续发展的目标。     

Discussion on “Composite (steel-concrete) highway bridge fatigue assessment” by F.N. Leitão, J.G.S. da Silva, P.C.G. da S. Vellasco, S.A.L. de Andrade, and L.R.O. de Lima [J Constr Steel Res 2011; 67(1): 14-24]

A discussion was proposed on the paper “Composite (steel-concrete) highway bridge fatigue assessment” by F.N. Leitão, J.G.S. da Silva, P.C.G. da S. Vellasco, S.A.L. de Andrade, and L.R.O. de Lima. The main point of the discussion is the finite element model, in which the shear connectors of the steel-concrete composite girders were not considered. Besides, several issues such as the influence of other variable loads, the dynamic effects of vehicle loads due to irregular pavement surface, and critical locations of fatigue assessment of steel-concrete composite girders require further explanation to the readers.