Background Information
It was on September 11, 2001, when World Trade Center, WTC suddenly collapsed following terror attacks by the suspected Al Qaeda group. Following the destruction of this stature, everyone was surprised at first, and to establish the cause of the incident, there were speculations that the building was structurally defective. In order to establish the truth of what happened in the WTC incident of 2001, proper analyses of three parameters should be put into perspective: damage caused to the column by the airplane impact, loss of steel strength, and the inward collapse of the building with less tipping margin.
Not so many columns were interfered with by the initial impact of the airplane; but, the consequence of this first impact made a number of columns to be loaded with unbalanced weight. On the other hand, Eagar and Musso (2001) note that “Of equal or even greater significance during this initial impact was the explosion when 90,000 L gallons of jet fuel, comprising nearly 1/3 of the aircraft’s weight, ignited. The ensuing fire was clearly the principal cause of the collapse.”
Steel lose its strength as a result of heat and this can occur at temperature of around 425°C and when the temperature reaches 650°C, lose up to half steel’s strength is possible, (Cote, 1992). Structural failure of steel has been seen as the potential cause of the collapse of the WTC; however, steel strength hardly explains how the building collapsed because it could still offer support for up to three folds stress level of a 650°C inferno.
Therefore to articulately explain the reason for the collapse, it is right to say that due to unbalanced temperature of the steel at various points, the structure was distorted and this made it generally weak. Sides facing the inferno were hotter than the exterior part of the box columns. The resultant effect of the distortions led to buckling failure of slender steel structures. In a wider perspective, failure of the steel was due to two factors: loss of strength due to the temperature of the fire, and loss of structural integrity due to distortion of the steel from the non-uniform temperatures in the fire, (Eagar and Musso, 2001).
The Similarities and Difference between 9/11 Fire and the DuPont Plaza
Hotel Fire of 1986
DuPont Plaza Hotel Fire was caused by striking employees in the middle of settling dispute with the hotel management. “The three staffs: Hector Escudero Aponte, Jose Rivera Lopez and Arnaldo Jimenez Rivera set up fires with the intention of scaring tourists out of the hotel, only for the fire to spread to the hotel’s store,” (Harris, 2010). In the store there was furniture which got burnt, from which fire flashover was developed in big magnitudes. At the ballroom, gasses were heated at high temperatures and the developing fire was then sucked into casinos via open doors. In the inferno, a total of 97 people died and several casualties reported.
From the information above, it is true that the fire was not an accident but a planned disaster that blew out of proportion. This shows similarity with the 9/11 fire that was a planned terror attack by Al-Qaeda. The number of victims who lost there lives in World Trade Center fire was massive compared to the DuPont Plaza Hotel fire. This is because in the former case, steel structure failure majorly contributed to collapse of the skyscraper and structural distortion led to more deaths apart the fire itself. In DuPont Plaza Hotel inferno, deaths resulted from splashing over of fire and gasses to other rooms like casinos where most people were. Structural failure in the case of DuPont fire was not as immense as the case of WTR was. The 9/11 bombing of WRC is an example of smoky fire due to high presence of soot that was witnessed afterwards.
Another difference between the two fires is the type of flames that were witnessed. The WRC fires was Class B; resulting from flammable materials like airplane fuel and gasoline among other flammable liquids while Du Pont Plaza Hotel fire can be classified as Class A; resulting from burning of wood products. DuPont fires could also fall under Class B due to the involvement of fuel at the initial set up of the blaze; but this is less significant as fire from the furniture is what led to massive flashover to other areas. According to Harris, (2010) investigations carried out revealed that, “They found that the fire was of incendiary origin and was started in a stack of new furniture that was stored in corrugated boxes in a ballroom.”
Fire Triangle
Fire growth process is dependent on three basic elements: energy source like fuel, heat and air. For an inferno to sustain itself there must be presence of oxygen whereas heat is necessary in raising ignition temperature. Analysis of these three elements is crucial in fire safety where fire fighters try as much as possible to separate the elements. “Fuel can be naturally removed from the equation when the fuel completely burns out or it can be manually removed. Essentially, how a fire is extinguished depends on the type of fire it is,” (Joyce, Miller and Wamakima, 2008). However all fire types vastly depend on removal of heat as the conventional way of fire extinguishing.
Fire Fighting Strategies
To fight fire set up, a number of tactics can be used some of which are preventive while other are rescue-based. While preventive strategies include enhanced communication system among other preventive measures, rescue-based measure include fire extinguishing, escape routes and fire containment measures. Communication strategies can also be employed when an inferno occurs to help in evacuation; and, it is during such times that fire alarms are used to raise alert. In the containment strategy, buildings should be designed to ensure that fire does not spread to other adjacent areas. Another determinant of fire spread is rate of burning; and the higher the rate, the higher the risk of spreading and vice versa. To prevent fire spreads, buildings should be highly ventilated, built with smoke vents, and smoke barrier.
Fire extinguishing strategies are employed via use manual methods of fire fighting. Equipment that used in these cases include: fire extinguisher and hose rills, and other automated systems. The most common automation employs the use of sprinkler system. According to (Joyce, Miller and Wamakima, 2008), “sprinkler heads are placed throughout a structure with pipes going back to a main source of water, be it a reserve tank or the structure’s local water supply.” The more accessible a building is the more success a fire extinguishing effort will be. Sprinkler system is popular due to its ability to extinguish and contain fire. It is important to note however, that fire fighting strategies are not exclusive as their employment does overlap at times in risk reduction and containment of infernos.
Code and Building Standards Necessary for Fire Prevention
According to Grant and Cote, (2006). “A code is a law or regulation that sets forth minimum requirements and, in particular, a building code is a law or regulation that sets forth minimum requirements for the design and construction of buildings and structures.” The main objective of setting up building codes is to ensure safety of mankind at times of accidents like infernos. There are two types of codes used: specifications code; also known as prescriptive codes and performance codes.
Prescriptive codes articulate the materials to be used, construction sizes, and how to amass components. On the other hand, performance codes include laid down objectives with proper criteria for assessment of whether objectives are met or not. Performance codes are similar to prescriptive codes, with the only difference being applicability of alternative methods of achieving desired results. Joyce, Miller and Wamakima, (2008) note that, “Model safety codes, such as building and fire codes, are developed through consensus-based processes by code development organizations, but they do not become laws until they are adapted by state and municipalities.”
In the early 1970s, codes that were set to check fire incidents included: building structures without use of aluminum wiring and installation of communication devices. Another aspect that was addressed by 1970s codes was to avoid use of flammable furnishings. This was aimed at reducing fire spreads and to contain fires within one area. However, codes now address performance-based building structures unlike the prescriptive measures of the 1970s.
Modern fire challenges are addressed by performance codes that seek to address spread of fire from one floor to the next. Hence fire has to be contained at its origin because once it gets to the atrium; it becomes a difficult task in containing it. Another strategy of performance codes in recent times is to build structures with automated sprinkler systems and building structures with ample escape routes when inferno strikes.
Building codes are intended for the prevention of extreme fire behavior occurrence. Extreme fire behavior include: flashover, smoke explosion, and back draft. Post flashover circumstances is a quick fire process that leads to a high level combustion and lack of adequate awareness about the incident can lead to more loss. Proficiency is thus needed to recognize fire behavior from which a deep understanding of fire ground may be easy.
Flashover refers to development of fire from low to high level within a short spell. Flashovers are enhanced by combustible furnishings and structural designs that allow for rapid fire spread; for instance, existence of atrium. Ventilation is also another avenue for increased flashover. The DuPont Plaza Hotel inferno experienced flashover due to high ventilation of the structure to provide for comfort of tourists. As a result, fires spread faster to the casinos from the furniture storage with immense heat and choking gases.
Conclusion
Fires are among the fatal tragedies that have befallen America since time immemorial. Fire tragedies continue to haunt people all over the world despite efforts made to fight fires. Development of codes as measures of curbing infernos continues to ensue. Codes have been developed as a result of witnessed weaknesses that emanate from fire incidents and this explains why codes used in the 1970s have been changed in modern times. It is therefore crucial for structural designs of buildings adhere to building and fire codes to aid in evacuation efforts and containment of infernos.
References
Cote, A. E., ed. National Fire Protection Association (1992). Fire protection handbook. 17th edn. Quincy, MA: National Fire Protection Association.
Eagar, T. W. and Musso, C. (2001). “Why did the World Trade Center collapse? Science, engineering, and speculation.” JOM Journal. 53 (12), 8-11.
Grant, C. C. and Cote, A. E. (2006). Safety in the built environment. Codes and standards for the built environment. Web.
Harris, C. (2010). DuPont Plaza Hotel arson. Web.
Joyce, S., Miller, L., and Wamakima, D. (2008). Fire safety in green buildings. Web.