Obvious concerns, such as when a firefighter entering a high-rise building loses communications with his team because tall buildings are not conducive to radio wave transmission and therefore do not allow firefighters' radios to work properly has not been addressed during the recent trend of building higher and higher.
Even something as simple as an external fire on a high-rise cannot be defended with the conventional firefighting techniques used throughout history. Unless helicopters or airplanes are deployed, a simple fire on say the 75th floor could wreak havoc. These concerns regarding safety and building size were logged from fire service representatives long before September 11th. As early as 1995, retired Fire Chief of the FDNY, Vincent Dunn wrote that the World Trade Centers were lacking proper evacuation avenues and that if the buildings ever encountered a serious fire, existing procedures would be useless and that people above a certain threshold would not be able to evacuate.
As Taipei 101 prepares to lose the coveted title of the world's largest building, the majority of skyscrapers around the world fall under safety codes implemented for ten story buildings. New safety standards must be created for buildings of 100 or more stories or the occupants will never be completely safe. As the building trends run their course, new safety considerations will be needed. Not only an airplane attack is reason for concern: the basic fire can be just as deadly.
The term truss means to bind or fasten. In construction terminology, builders support things by using a truss or trusses. The heritage dictionary goes a bit further by pointing out that a truss in a building or construction sense could mean "any of a various number of structural frames constructed on the principles that are other than geometric rigidity of the triangle or deriving stability from other factors, as the rigidity of joints, the abutment of masonry, or the stiffness of beams." An example would be in the case of the World Trade Center towers, as mentioned, the concrete slab floors that were literally anchored to the sides for the buildings by using a truss-construction methodology.
Prior to September 11, engineers would have sworn by the truss construction system as a reliable high-rise technique. No test for truss construction had even conceived of the situation created by the crashing of the two hijacked jetliners turned missiles.
Depending on the type of construction used in newer high-rise buildings, designers take into consideration a number of different types of collapse scenarios. Even though designers were aware of the possibility of fire when they used truss techniques in the Twin Towers, the designers most likely only tested the possibility of construction failure because of normal fire exposure. The September 11 events triggered temperatures well over the norm. Therefore, the type of collapse that occurred on that day was beyond the experience and established history of truss construction methods.
Truss technology has come under fire. However, although the design and construction of the World Trade Center Towers is open to criticism now, the fact that the Twin Towers took over an hour to eventually fall after sustaining direct hits from two fast moving jetliners provides some idea of how strong the buildings actually were. "The fact that the structures were able to sustain this level of damage and remain standing for an extended period of time is remarkable." (Graham-Rowe, 2003)
Firefighters Structural Analysis
The buildings are getting taller. The fact that a 110-story building collapsed in only 8 seconds should put fear in the heart of any fire fighter. Once a firefighter makes a decision to go into a building to help those in need - he must understand ahead of time that 8 seconds most likely will not provide enough time to escape.
From a fire fighters perspective, the Twin Towers departed from accepted high-rise buildings when it came to the construction process. New skyscrapers do not bear the load in the same manner as conventional skyscrapers did in the 19th century. have been built with a skeleton of interior supporting columns that supports the structure. Exterior walls of glass steel or synthetic material do not carry any load.
In conclusion, this report attempted to examine how and why fire fighters continue to show concern regarding the ever increasing size of the world's skyscrapers. When the World Trade Centre towers were completely destroyed on September 11, 2001, many in the fire service were convinced future high rise safety concerns would put an end to the construction of skyscrapers. Yet, the world's demand for newer and taller structures continues to increase. It is apparent that our global population desires high-rise complexes in spite of the catastrophic events of September 11th. Economic indicators such as the currently low interest rates and the high consumer demand will continue to force engineers to reach for new record buildings. Designers, architects and builders seem confident that the only effect in the newer higher buildings will be that any future plane crashes will only generate lots of broken glass and limited structural damage at the point of the impact. Therefore, because of this new found sense of confidence in the design and construction the world demand for high-rises will be higher than ever. But, from a firefighter's perspective, the new found confidence may not be on a solid foundation.
Dunn, Vincent (2003). Collapse of Burning Buildings. Retrieved September 24, 2004, at http://www.firenuggets.com/dunn3.htm
Dunn, Vincent. (2002). WHY THE WORLD TRADE CENTER BUILDINGS COLLAPSED: A FIRE CHIEF'S ASSESSMENT. Retrieved September 24, 2004, at http://www.firenuggets.com/dunn3.htm
Graham-Rowe, Duncan. (05 February 03). Twin Tower Collapse Theory Challenged. Retrieved September 26, 2004, at http://www.newscientist.com/news/news.jsp?id=ns99993354
Greeman, Adrian (2002). Eastern High-Rise: Record Breaking High Rise Construction Continues Apace In Asia, And Favco Seems To Be The Preferred Crane Of The Job. Cranes Today, July.