The resilience of U.S. communities, defined as the "ability to withstand and recover rapidly from disruptive events," is directly dependent upon the ability of the built environment to maintain and support the functions upon which modern society relies. The built environment includes buildings and infrastructure systems. Buildings are important because they provide critical services (e.g. hospitals, police stations, and mercantile buildings). Infrastructure systems include the physical networks, systems, and structures that make up transportation, energy, communications, water, wastewater, and other systems that support the functionality of community social institutions. As local decision makers consider resilience, choices often involve cost-benefit decisions among materials with differing initial and lifetime costs, and differing performance characteristics. This paper will describe the important role that materials science plays in enabling informed local decisions for resilience and identify knowledge gaps, such as the service life of the materials designed for new construction or system repair.

This paper describes the occupant evacuation of World Trade Center (WTC) 1 and WTC 2 on September 11, 2001. Multiple sources of information were collected and analyzed: over 1,000 new interviews with survivors (including 803 telephone interviews, 225 face-to-face interviews, and 6 focus groups); over 700 published interviews; 9-1-1 emergency calls; transcripts of emergency communications, historical building design drawings, memoranda, and calculations; formal complaints filed with the Occupational Safety and Health Administration; and other relevant materials. The population in WTC 1 and WTC 2 on September 11, 2001, at 8:46:30 a.m. is enumerated and described, where the characteristics of the population were relevant to the subsequent evacuation, including training, experience, mobility status, among others. The progress of the evacuation of both towers is described in a quasi-chronological manner from 8:46:30 a.m. when WTC 1 was attacked, until 10:28:22 a.m., when WTC 1 collapsed.

A standard procedure is needed for obtaining smoke toxic potency data for use in fire hazard and risk analyses.Room fire testing of finished products is impractical, directing attention to the use of apparatus that can obtain the needed data quickly and at affordable cost.This report examines the first of a series bench-scale fire tests to produce data on the yields of toxic products in both pre-flashover and post-flashover flaming fires.The apparatus is the radiant furnace in NFPA 269 and ASTM E 1678.Test specimens were cut from finished products that were also burned in room-scale tests: a sofa made of upholstered cushions on a steel frame, particleboard bookcases with a laminated finish, and household electric power cable.Initially, the standard test procedure was followed, with a variation to reduce the contribution to the effluent of postflaming pyrolysis.Subsequent variations in the procedure included cutting the test specimen into small pieces and performing the tests at a reduced oxygen volume fraction of 0.17.The yields of CO 2 CO, HCl, and HCN were determined.The yields of other toxicants (NO, NO 2 , formaldehyde, and acrolein) were below the detection limits, but volume fractions at the detection limits were shown to be of limited toxicological importance relative to the detected toxicants.In general, dicing the test specimen and performing the tests at the reduced oxygen volume fraction had little effect on the toxic gas yields, within the experimental uncertainties.The exceptions were an increase in the CO yield for diced specimens at reduced oxygen, a decrease in the HCN yield from the intact sofa and cable specimens at reduced oxygen, and an increase in the HCN yield from dicing the cable specimens.In none of the procedure variations did the CO yield approach the value of 0.2 found in real-scale postflashover fire tests.

This paper summarizes the primary structural systems that comprised World Trade Center (WTC) 1, 2, and 7, which were destroyed in the terrorist attacks of September 11, 2001. There were four major structural subsystems in the towers: the exterior walls, the core, the floor system, and the hat truss. The major structural systems within WTC 7 were the foundation, exterior moment frames, floor system, interior columns, and column transfer trusses and girders. At the time of design and construction, the WTC towers were innovative in many ways, and resulted in a tremendous increase of open-plan commercial office space in downtown Manhattan. As the first of four papers, this paper summarizes the structural and passive fire protection features of each building, and focuses on the structural systems which played a critical role in the outcome of the attacks of September 11, 2001. Three companion papers address the effects of aircraft impact damage on the WTC towers and debris damage on WTC 7, the effects of fire on the three buildings, and how these events contributed to building collapse by describing the contribution of key structural systems to the overall building behavior and collapse, such as the floor systems and hat trusses in WTC 1 and WTC 2 and the floor connections around Column 79 in WTC 7.

Fire costs and losses are a significant life safety and economic burden on society comprising about two percent of the United States gross domestic product. This paper presents the results of a roadmap developed by the National Institute of Standards and Technology (NIST) in response to the U.S. fire problem and proposes ways to best reduce fire losses and costs in buildings and communities. In an effort to address the most pressing fire problems, attention is directed towards the burden of fire on communities, structures and their occupants, the fire service, and the economy in three key areas: Reducing fire risk in buildings, Advancing fire service technologies, and Reducing fire risk in wildland-urban interface (WUI) communities. The roadmap sets targets for new measurement capabilities that underpin innovation in fire-risk-reducing technologies and best practices. These advanced capabilities are required to overcome technical hurdles that stand in the way of nascent or current technologies with the potential to deliver a wide range of fire safety benefits. The roadmap stresses the measurement science needed to enable the most promising technologies that will reduce the preventable burden of fire in the three focus areas. The breadth of key technology issues ranges from reliable nuisance-free fire detection, improvements in the fire-safety design and construction of buildings and communities, to better firefighting equipment and tactics, to more effective approaches to preventing and responding to "wildland-urban interface" fires, which is a rapidly growing problem in the U.S. and many other countries. The roadmap sets short, medium and long-term goals for accomplishing the overall objective of reducing the U.S. fire burden and emphasizes the importance of science-based standards, regulatory codes, engineering tools, and best practices.

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.

Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately.Such identification is not intended to imply recommendation

This paper presents the findings of the NIST World Trade Center Investigation describing the occupant evacuation of WTC 1 and WTC 2 on September 11, 2001. The egress system, including stairwells and elevators, is described along with the evacuation procedures. The population in WTC 1 and WTC 2 on September 11, 2001 at 8:46 a.m. is enumerated and described, where the background of the population was relevant to the subsequent evacuation, including training, experience, mobility status, among others. The progress of the evacuation of both towers is described in a quasi-chronological manner. A decedent analysis explores where occupants were located when each tower was attacked. Multiple regression models were built to explore the sources of evacuation initiation delay (why people did not immediately start to leave the building), as well as stairwell evacuation time (how long the average occupant spent in the stairwells per floor). Issues identified as contributing to either slowing or aiding the evacuation process were explored. Egress simulations provided context for estimating how long WTC 1 and WTC 2 would have taken to evacuate with different populations, using three different models, and subject to different assumptions of damage to the building.

This paper identifies five grand challenges in the multidisciplinary field of pedestrian and evacuation dynamics (PED). In order to maximize the effectiveness of limited resources, the PED community would benefit greatly from a prioritized, consensus-based research agenda. The five proposed research initiatives include (1) a general human behavior model with a theoretical foundation and numerical validity, (2) a database archiving actual building emergency evacuations, (3) methods to embrace the stochastic nature of inputs and outcomes in building evacuation, (4) a validated method to integrate distributions of egress calculations with fire hazard calculations, and (5) adoption of technology for people movement, data collection, and within modeling constructs. The list proffered in this paper may reflect the building evacuation perspective of the author and is intended merely as a spark for discussion amongst the greater PED community; a true consensus research agenda requires deliberation by leaders in the community.

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.

Occupant descent down stairwells during building evacuations is typically described by measurable engineering variables such as stairwell geometry, speed, density, and pre-evacuation delay. In turn, predictive models of building evacuation use these variables to predict the performance of egress systems for building design, emergency planning, or event reconstruction. This paper provides a summary of literature values for movement speeds and compares these to several new fire drill evacuations. Movement speeds in the current study are observed to be quite similar to the range of literature values. Perhaps most importantly though, the typical engineering parameters are seen to explain only a small fraction of the observed variance in occupant movement speeds. This suggests that traditional measures form an incomplete theory of people movement in stairs. Additional research to better understand the physiological and behavioral aspects of the evacuation process and the difference between fire drill evacuations and real fire emergencies are needed.