World Trade Center Twin Towers Research Articles

Spontaneous Collapse Mechanism of World Trade Center Twin Towers and Progressive Collapse in General

The collapse of the World Trade Center (WTC) Towers during the terrorist attacks on September 11, 2001, remains one of the most tragic catastrophes in the field of structural engineering. This paper first reviews a mathematical model that explains the process of the total collapse of the Twin Towers and shows that the downward collapse progression below the impacted floors was spontaneous. The model is based on a continuum description of the motion of the crush front and captures various types of energy dissipation during the collapse. The predictions of this model match all the observations, including the video records of the first few seconds of motion of both towers, the seismic records of the collapse durations for both towers, the mass and size distributions of comminuted concrete particles, and the fast expansion of dust clouds during collapse with the booms generated. This catastrophe provoked general interest in other types of progressive collapse of buildings. This is the subject of the second part of this paper, in which a three-dimensional stochastic computational model for the collapse of RC frame buildings is presented. The occurrence probabilities of different collapse patterns are predicted. The model is further extended to investigate the delayed collapse behavior of RC frames. The results of the analysis shed light on the emerging trend of probabilistic analysis and design of structures against progressive collapse.

Thermodynamics of Tower-Block Infernos: Effects of Water on Aluminum Fires.

We review the thermodynamics of combustion reactions involved in aluminum fires in the light of the spate of recent high-profile tower-block disasters, such as the Grenfell fire in London 2017, the Dubai fires between 2010 and 2016, and the fires and explosions that resulted in the 9/11 collapse of the World Trade Center twin towers in New York. These fires are class B, i.e., burning metallic materials, yet water was applied in all cases as an extinguisher. Here, we highlight the scientific thermochemical reasons why water should never be used on aluminum fires, not least because a mixture of aluminum and water is a highly exothermic fuel. When the plastic materials initially catch fire and burn with limited oxygen (O2 in air) to carbon (C), which is seen as an aerosol (black smoke) and black residue, the heat of the reaction melts the aluminum (Al) and increases its fluidity and volatility. Hence, this process also increases its reactivity, whence it rapidly reacts with the carbon product of polymer combustion to form aluminum carbide (Al4C3). The heat of formation of Al4Cl3 is so great that it becomes white-hot sparks that are similar to fireworks. At very high temperatures, both molten Al and Al4C3 aerosol react violently with water to give alumina fine dust aerosol (Al2O3) + hydrogen (H2) gas and methane (CH4) gas, respectively, with white smoke and residues. These highly inflammable gases, with low spontaneous combustion temperatures, instantaneously react with the oxygen in the air, accelerating the fire out of control. Adding water to an aluminum fire is similar to adding “rocket fuel” to the existing flames. A CO2–foam/powder extinguisher, as deployed in the aircraft industry against aluminum and plastic fires by smothering, is required to contain aluminum fires at an early stage. Automatic sprinkler extinguisher systems should not be installed in tower blocks that are at risk of aluminum fires.

State, Religious Education, and Prevention of Violent Extremism in Southeast Asia

In the last two decades, violent extremism has become the center of attention for the world. The 9/11 attack in New York which devastated the World Trade Center (WTC) twin towers were a “big bang” for the violence phenomena triggered by the existence of radical religious ideas. The tragedy carried out by the al-Qaeda extremist group triggered tension in many countries which at some level it gave birth to the symptoms of a so-called called “Islamophobia”—a religious perspective that sees Islam as the estuary of violence. That dark event, then, has signaled a new chapter in the portrait of global diversity.Since then, violent extremism phenomena have been increasingly affecting the Southeast Asian region. Bali Bombing I (2002), Bali Bombing II (2005), attacks on the Ahmadiya group in Cikeusik, Banten (2011), Sunni conflicts with Shia community in Sampang, Madura (2013), burning of churches in Singkil, Aceh and burning of mosques in Tolikara, Papua (2015), the bombing on Thamrin Street, Jakarta (2016) and the suicide bombings in three churches in Surabaya (2018) have shown us that violent extremism was a bitter experience for Indonesia. This gives a gloomy representation for the essence of religious understanding that rests on the idea of raḥmatan li al-‘ālamīn—becoming a blessing for the entire universe. Also, the phenomena have alarmed us to be cautious and worry about threats on Indonesianism that upholds diversity.

Failure of Ethical Leadership: Implications for Stakeholder Theory and “Anti‐Stakeholders”

AbstractLeaders in a variety of organizations are beset by challenges that test their commitments to ethical behavior in interactions with stakeholders who make up their working environments. Situations that present themselves include complex management of expectations, people, and resources, which require novel solutions that also test the boundaries between right and wrong. Such conditions arose after the 9/11 terrorist attacks on the World Trade Center Twin Towers. President Bush asked the Central Intelligence Agency to round up persons who represented a continuing threat of harm to U.S. interests. What followed was a series of decisions and actions by a number of internal and external constituencies based on inaccurate reporting of treatment of and information gleaned from detainees. Lessons for understanding and avoiding resulting leadership ethical dilemmas and a novel stakeholder perspective are provided in the close.

Evacuating Damaged and Destroyed Buildings on 9/11: Behavioral and Structural Barriers

Evacuation of the World Trade Center (WTC) twin towers and surrounding buildings damaged in the September 11, 2001 attacks provides a unique opportunity to study factors that affect emergency evacuation of high rise buildings. Problem The goal of this study is to understand the extent to which structural and behavioral barriers and limitations of personal mobility affected evacuation by occupants of affected buildings on September 11, 2001. This analysis included 5,023 civilian, adult enrollees within the World Trade Center Health Registry who evacuated the two World Trade Center towers and over 30 other Lower Manhattan buildings that were damaged or destroyed on September 11, 2001. Multinomial logistic regression was used to predict total evacuation time (<30 to ≤60 minutes, >1 hour to <2 hours relative to ≤30 minutes) in relation to number of infrastructure barriers and number of behavioral barriers, adjusted for demographic and other factors. A higher percentage of evacuees reported encountering at least one behavioral barrier (84.9%) than reported at least one infrastructure barrier (51.9%). This pattern was consistent in all buildings except WTC 1, the first building attacked, where >90% of evacuees reported encountering both types of barriers. Smoke and poor lighting were the most frequently-reported structural barriers. Extreme crowding, lack of communication with officials, and being surrounded by panicked crowds were the most frequently-reported behavioral barriers. Multivariate analyses showed evacuation time to be independently associated with the number of each type of barrier as well as gender (longer times for women), but not with the floor from which evacuation began. After adjustment, personal mobility impairment was not associated with increased evacuation time. Because most high-rise buildings have unique designs, infrastructure factors tend to be less predictable than behavioral factors, but both need to be considered in developing emergency evacuation plans in order to decrease evacuation time and, consequently, risk of injury and death during an emergency evacuation.

Response Phase Behaviours and Response Time Predictors of the 9/11 World Trade Center Evacuation

The evacuation of the World Trade Center (WTC) Twin Towers on 9/11 is one of the largest full scale high-rise emergency evacuations to date and provides an opportunity to learn from survivor experiences. Here, quantitative and qualitative data extracted from the UK WTC High-rise Evacuation Evaluation Database (HEED) study were used to: (i) calculate more fine-grained response times useful for evacuation modelling; (ii) investigate Response Phase behaviours; and (iii) see which of these behaviours and other factors predicted the response times. Analyses revealed that the majority of participants’ response times were within 0 min to 1 min of WTC1 being hit (rapid responders) and 1 min to 4 min (moderate responders). Logistic regression indicated that rapid responders were more likely to be participants in WTC2 than participants in WTC1, the tower that was currently under attack. Higher perceived risk and undertaking fewer if any tasks prior to evacuation also significantly predicted rapid response times. Conversely, response times beyond 1 min from WTC1 impact were significantly predicted only by increased numbers of Information Tasks being undertaken prior to evacuation. These tasks appeared to be undertaken more frequently prior to evacuation than were Action Tasks.

Rule of Law in UK Since September 2001

The world changed in so many ways since September 11, 2001 that it would be difficult to assess the impact the terrorist attacks on World Trade Center twin towers had on the entire legal fraternity. Terrorism has become a part of life for people all around the world. UK has been living with terrorism for a fairly long time due to the Irish atrocities but it was in a much smaller scale compared to what the Al Qaeda terrorists planned to achieve. Terrorism made most countries cautious and this brought about new stringent laws that presented new challenges to the sanctity of the rule of law. Complexities of terrorism present different challenges to uphold rule of law and liberty.

Equation of Motion Governing the Dynamics of Vertically Collapsing Buildings

AbstractThe present paper aims at contributing to a discussion, opened by several authors, on the proper equation of motion that governs the vertical collapse of buildings. The most striking and tragic example is that of the World Trade Center Twin Towers, in New York City, about 10 years ago. This is a very complex problem and, besides dynamics, the analysis involves several areas of knowledge in mechanics, such as structural engineering, materials sciences, and thermodynamics, among others. Therefore, the goal of this work is far from claiming to deal with the problem in its completeness, leaving aside discussions about the modeling of the resistive load to collapse, for example. However, the following analysis, restricted to the study of motion, shows that the problem in question holds great similarity to the classic falling-chain problem, very much addressed in a number of different versions as the pioneering one, by von Buquoy or the one by Cayley. Following previous works, a simple single-degree-of-...

Phantom Empire: A Feminist Reflection Ten Years After 9/11

On May 1, 2011, close to ten years after Al Qaeda suicide bombers had used jet airplanes to demolish three targets in the eastern United States - most unforgettably blowing the World Trade Center twin towers up in smoke - the United States, having at last managed through its intelligence sources to locate the Pakistani hill refuge where Osama bin Laden had been hiding, secretly dispatched its Navy SEAL team to go there and shoot dead. There are many both tragic and farcical things might remark on about this momentous yet peculiarly anticlimactic event. On the tragic side of course are the hundreds of thousands of Iraqi and Afghani civilian and young U.S. military lives lost, displaced, or permanently maimed, and trillions of dollars of US. public resources squandered, on the murderous path to hunting down Al Qaeda and its leader. Representing the farcical, have U.S. mass cultures schizophrenic response to the announcement that we got him - the hysterical football cheers for Our Side and frat boy street celebrations quickly followed by pious quotations from Proverbs and Facebook posts about doing as Jesus would and forgiving our enemies (Sullivan 2011). And for combined elements of both tragedy and farce, consider the deliberate timing and staging of bin Ladens execution as a racialized and gendered propaganda tactic in the lead-up to the 2012 presidential election and the certification of Barack Obama as a Real (honorary white Christian) Man, whose valor in exterminating the Islamist foe will go down as unassailable. But I prefer to focus on another, less noticed sequel to the US. security apparatus's Top Assassination. Within two weeks, a strange follow-up episode occurred when the government of Pakistan made the gesture of returning to the United States the tail of the damaged stealth helicopter that the navy had used to perform the commando operation. Mainstream U.S. media reported this act in the light of strained US.-Pakistani relations following the killing. Pakistan faced tremendous criticism in the U.S. Congress for, if not deliberately harboring terrorists, then its leaders' apparent ignorance of bin Ladens whereabouts all those years and not doing enough to show support for the U.S.-led War on Terror while receiving billions in U.S. military and economic aid. Internally, President Asif Ali Zardari came under strong attack for abetting the violation of Pakistani sovereignty by, as the Washington Post put it, not having been of the raid in advance (as if being informed of U.S. unilateral action would be any less indicative of imperial fiat). But I propose shift our vantage point to look more closely at what this Return of the Tail signifies, both materially and symbolically, with regard to U.S. positioning in the world and the shape of masculinist militarism ten years after 9/1 1. In so doing, may find that, in ways newly configuring the fall of the twin towers ten years ago, this piece of tail returns as a kind of fetish embodying the decline of American empire in the twenty-first century. In the immediate aftermath of the terrorist attacks in September 2001, I imagined a new geopolitical scenario arising in the smoke clouds through the symbolism of phantom twin towers: the American imperial colossus confronting Al Qaeda and its jihadist partners and counterparts across the globe (Petchesky 2002). My point was to counter the prevailing Manichean Good versus Evil narrative that resounded at the time - certainly among the U.S. right wing and George W. Bush administration but also, in a kind of reverse fashion, among certain elements of the Left; a narrative of either righteous defenders of the Homeland and Christian values versus crazy jihadist terrorists; or, alternatively, resistant anti-imperialists (the chickens coming home to roost) versus arrogant Western oil interests. Rather than opposites, I argued, these two adversaries mirrored each other like fratricidal twins in their capitalist wealth, nationalist imperialist ambitions, manipulation of religion, staunch militarism, masculinism (even if, in the U. …

Discussion of “What Did and Did Not Cause Collapse of World Trade Center Twin Towers in New York?” by Zdeněk P. Bažant, Jia-Liang Le, Frank R. Greening, and David B. Benson

Discussion of “What Did and Did Not Cause Collapse of World Trade Center Twin Towers in New York?” by Zdeněk P. Bažant, Jia-Liang Le, Frank R. Greening, and David B. Benson

Closure to “What Did and Did Not Cause Collapse of World Trade Center Twin Towers in New York?” by Zdeněk P. Bažant, Jia-Liang Le, Frank R. Greening, and David B. Benson

Closure to “What Did and Did Not Cause Collapse of World Trade Center Twin Towers in New York?” by Zdeněk P. Bažant, Jia-Liang Le, Frank R. Greening, and David B. Benson

What Did and Did Not Cause Collapse of World Trade Center Twin Towers in New York?

Previous analysis of progressive collapse showed that gravity alone suffices to explain the overall collapse of the World Trade Center Towers. However, it remains to be determined whether the recent allegations of controlled demolition have any scientific merit. The present analysis proves that they do not. The video record available for the first few seconds of collapse is shown to agree with the motion history calculated from the differential equation of progressive collapse but, despite uncertain values of some parameters, it is totally out of range of the free fall hypothesis, on which these allegations rest. It is shown that the observed size range (0.01 — 0.1 mm) of the dust particles of pulverized concrete is consistent with the theory of comminution caused by impact, and that less than 10% of the total gravitational energy, converted to kinetic energy, sufficed to produce this dust (whereas, more than 150 t of TNT per tower would have to be installed, into many small holes drilled into concrete, to produce the same pulverization). The air ejected from the building by gravitational collapse must have attained, near the ground, the speed of almost 500 miles per hour (or 223 m/s, or 803 km/h) on average, and fluctuations must have reached the speed of sound. This explains the loud booms and wide spreading of pulverized concrete and other fragments, and shows that the lower margin of the dust cloud could not have coincided with the crushing front. The resisting upward forces due to pulverization and to ejection of air, dust, and solid fragments, neglected in previous studies, are indeed found to be negligible during the first few seconds of collapse but not insignificant near the end of crush-down. The calculated crush-down duration is found to match a logical interpretation of seismic record, while the free fall duration grossly disagrees with this record.

Methodologies Employed in the Collection, Retrieval and Storage of Human Factors Information Derived from First Hand Accounts of Survivors of the WTC Disaster of 11 September 2001

This article provides a broad overview of project HEED (High-rise Evacuation Evaluation Database) and the methodologies employed in the collection and storage of first-hand accounts of evacuation experiences derived from face-to-face interviews of evacuees from the World Trade Center (WTC) Twin Towers complex on September 11, 2001. In particular, the article describes the development of the HEED database. This is a flexible research tool which contains qualitative type data in the form of coded evacuee experiences along with the full interview transcripts. The data and information captured and stored in the HEED database is not only unique, but provides a means to address current and emerging issues relating to human factors associated with the evacuation of high-rise buildings

Stability of the World Trade Center Twin Towers Structural Frame in Multiple Floor Fires

This technical note presents the results from a nonlinear finite element analysis of a very simple two dimensional model of the World Trade Center Twin-Towers structural frame subjected to fire. The analysis was carried out for a large range of fire scenarios and was reported in detail in a recently published paper. The paper further investigates the results of this analysis to obtain the details of the collapse mechanism found. An interesting series of events leading progressively to overall collapse are discovered and described in detail. The main reason for the failure is found to be the low membrane capacity in compression of the composite steel truss and concrete deck slab floor system.

Advances in the Stability of Frame Structures

As far as structural engineering is concerned, scientific and technological advances are often fostered by the occurrence of collapses involving a more or less relevant amount of damage and, in the most unfortunate cases, also the loss of human lives. Indeed, it seems fair to say that every time a structural collapse takes place, designers and researchers will immediately start searching for a rational explanation; this boost of attention and interest invariably leads to the unveiling and investigation of new phenomena and also paves the way to the development of design tools intended to anticipate and prevent the detrimental effects of such phenomena. The above statements are especially true in the case of structural stability, as attested by the following illustrative examples: ~1! The progress in the theory of laced column buckling due to the collapse of the Quebec Bridge in 1907; ~2! the crucial role played by the Tacoma Narrows Bridge failure, in 1940, concerning the awareness and understanding of the aerodynamic torsional instability phenomenon; and ~3! the development of Koiter’s general elastic postbuckling theory, essentially inspired by the sudden collapse of several thin-shell structures at surprisingly low applied load levels. The very recent and unbearably tragic collapse of the World Trade Center twin towers, on September 11, 2001, highlighted the importance of devoting new attention and resources to a better understanding of behavioral, design, and safety issues related to the overall and member stability of framed structures— particularly when these structures are subjected to extreme loading conditions, such as the ones caused by impact, explosion, or fire. By publishing this Special Issue of the Journal of Engineering Mechanics, ASCE aims at making the above problems more visible, thus drawing the attention of the structural stability scientific and technological communities and encouraging them to devote new research to developing and disseminating more advanced methods for the efficient solution of these problems. At the same time, one has the opportunity of showing a representative sample of the activity currently under way in this field. The recent exponential growth in computer capabilities, affordability, compatibility, and interconnectivity is responsible for a virtual “computational revolution” in many areas related to structural analysis and design. In particular, this situation will certainly lead, in the near future, to the routine incorporation of geometrically and materially nonlinear concepts and methodologies into the daily design practice. It will also enable designers to feel more comfortable and secure when faced with the everexpanding tasks of coping with increasingly slender structures and more complex loading combinations, as they will have easy access to user-friendly tools that are able to handle advanced structural behaviors like the inelastic geometrically nonlinear behavior of initially imperfect members and framed structures, the global and local stability of nonprismatic thin-walled members,

PM exposure assessment of the population in Lower Manhattan area of New York City after the World Trade Center disaster

Abstract On 11 September 2001, the explosion and the collapse of the World Trade Center (WTC) Twin Towers in New York City (NYC), USA, generated a massive release of dust and inhalable toxic substances to the atmosphere as a result of the pulverization of various building materials, furniture, and computers. Many concerns were raised as Particulate Matter (PM) levels in Lower Manhattan might not meet the current National Ambient Air Quality Standards (NAAQS) (65 μg m −3 ). The current study aims to provide a first estimate of the scale of population exposures during this episode. Data collected from existing monitoring stations in September showed the occurrence of a series of high peaks of PM 2.5 registered in the Lower Manhattan area after the 11 September. An interpolation technique was used within a Geographical Information Systems (GIS) environment to estimate outdoor PM 2.5 concentrations over NYC. Monthly average of 24 h outdoor PM 2.5 concentration of Lower Manhattan was 20.2 μg m −3 and did not exceed the NAAQS value. PM 2.5 concentrations in indoor micro-environments were simulated by a deterministic micro-environmental model (INTAIR) and linear regression equations. Three typical population groups were identified for the NYC area—home-makers, office/shop-workers, and students/children—and their 12 h nighttime and daytime exposures were estimated from 14 September until the end of September, either as mean exposure (daytime and nighttime) or as exposure weighted by residential population distribution (nighttime only). Average nighttime and daytime exposures of the Lower Manhattan population were calculated to be 37.3 and 23.6 μg m −3 , respectively (daily average: 30.45 μg m −3 ), in which the various group movements and activities, smoking habits of individuals, and special population movements due to access restrictions and risk avoidance behaviors were considered. Within the study period, assuming the real nighttime population distribution followed the residential population pattern, approximate one quarter of the population was exposed to 20–30 μg m −3 PM 2.5 ; one half of the Lower Manhattan population was exposed to 10–20 and 30–60 μg m −3 ; around one fifth of the population was exposed to over 60 μg m −3 during nighttime. The results indicated that although the outdoor PM 2.5 concentration was lower than the NAAQS value, personal exposure levels, which were generally higher than the outdoor PM 2.5 concentration, might still be a reason of concern.

Please Play with Your Food: An Incomplete Survey of Culinary Wonders in Italian Renaissance Cookery

Wonders in Italian Renaissance Cookery As early as the 1st century C.E., food writers and cooks were devising illusions and theatrical presentations using food and culinary formulas. Roman gourmet Apicius' famous dish "Anchovies without Anchovies" and his utterance that "no one will know what he is eating" are (literally) classic examples of such "culinary wonders." In recent memory, illustrious chefs like Escoffier at the Savoy in London (who recreated a naval tragedy using poached chicken escalopes) and Abe Lebewohl of the Second Avenue Deli in New York City (who built a replica of the World Trade Center Twin Towers using chopped chicken livers) have made truly extraordinary--if not tasteful--contributions in this field of culinary arts. Such artifice and conceits found what was perhaps their greatest expression during the Italian Renaissance when the author of the "first modern cookery book," Maestro Martino of Como, documented a series of mirabilia gulae or "wonders of culinary indulgence," including a roast peacock that appears to be alive and spews fire and fishes that appear to swim in a suspended gelatin aquarium. A survey of his and his contemporaries' recipes reveals that the wholly new genre of culinary writing emerged together with the many other "secret books" of the Italian Renaissance, including miscellanea by famous Renaissance figures like Luca Pacioli.

Twin Towers: The Life of New York City’s World Trade Center

Book Review| July 01 2002 Twin Towers: The Life of New York City’s World Trade Center Twin Towers: The Life of New York City’s World Trade Center, Angus Kress Gillespie. Moira Smith Moira Smith Search for other works by this author on: This Site Google Journal of American Folklore (2002) 115 (457-458): 489–490. https://doi.org/10.2307/4129199 Cite Icon Cite Share Icon Share Facebook Twitter LinkedIn MailTo Permissions Search Site Citation Moira Smith; Twin Towers: The Life of New York City’s World Trade Center. Journal of American Folklore 1 January 2002; 115 (457-458): 489–490. doi: https://doi.org/10.2307/4129199 Download citation file: Zotero Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All Scholarly Publishing CollectiveUniversity of Illinois PressJournal of American Folklore Search Advanced Search The text of this article is only available as a PDF. Copyright 2002 American Folklore Society2002 Article PDF first page preview Close Modal Issue Section: Book Reviews You do not currently have access to this content.