The United States Al-Qaeda Attack on 11th of September 2001

On September 11, 2001, the United States came under attack by a foreign terrorist group named "Al-Qaeda”, an organization headed by a known terrorist Osama Bin Laden. Upon his orders, two high-jacked passenger airplanes descended on the World Trade Center Towers on an approach to terrorize and victimize Americans. Upon impact and as a result, many average Americans perished as they scurried to escape from a blazing inferno and impending collapse. Unfortunately, minutes after the impact of one of the planes the first tower succumbed to the fire and impact, leveling an iconic landmark.

Moments later, the second tower followed in its wake claiming over 3000 lives that were trapped inside the buildings and an additional 300 plus first responders, police officers and firefighters rushing to their aid. As the cleanup, search, rescue, and recovery of those missing began, so did the prompting of a fire investigation as to why the towers fell and why so quickly. In this presentation, I will explore some of the controversial theories, thoughts, and activities which followed such as, the fire investigator's role in finding a cause, the potential chemistry, physics aspects of collapse, and scene analysis.

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The post-impact collapse of the World Trade Center buildings commenced highly sought-after information from various agencies namely FEMA and other volunteer organizations wishing to gain answers as to why it collapsed when structural engineers previously documented the towers can withstand aircraft strikes the size of Boeing 707's. When in fact this event changed those original thoughts and drove a new vision of direction into assuring safety in skyscraper construction, building codes and standards, as well as building design and operational practices.

Much debate continues to this day between structural engineers and fire investigators about what caused the twin towers to fall. Some speculate that the building was structurally deficient due to its age, while others believe the impact of the aircrafts themselves severed the inner main structural members causing a "pancake effect" and fire suppression systems failed allowing the steel members to reach a temperature that rendered the steel malleable creating the collapse. The destructive demolition created an investigation that would take years to sift through. However, investigators were able to funnel in bystander information via video camera footage to provide initial theories for the collapse.

Initial reports stated that the impact of the aircraft crippled the strength of the inner and outer members creating the collapse but others argue that the estimated 90,000 L of jet-fuel that immediately burst into a fire ball created such a sudden heat effect that weakened structural supports and was destined for failure. But according to Eager and Musso, (2006): the fire is the most misunderstood part of the WTC collapse. Going on to state that temperature and heat are the two most misunderstood portions of fire and by this reference adds that the fact that there were 90,000 L (23780 gals.) of jet fuel on a few floors of the WTC does not mean that this was an unusually hot fire. The temperature of the fire at the WTC was not unusual, and it was most definitely not capable of melting steel.

This argument obviously leaves more for scientists to argue over. Nevertheless, the collapse is still the biggest lingering question because large skyscrapers such as these were constructed with redundancies under the premise of high wind stresses and other potentially catastrophic events like earthquakes. Yet they failed in a “pancaking effect" falling like pancakes one on top of another. Meanwhile, the system of floor joists, trusses and support columns could not support the weight. Additionally, the fire load and debris compounded each floor with additional weight reinforcing the collapse. Though, this collapse could have affected more buildings and lives had it fallen like a falling tree. But due to the tube-like design of the buildings the unaffected lowers floors exterior supports and columns were able to contain the outward force within its structural shell preventing the building and debris from bursting outward.

Department (NYFD) and unfortunately suffered the most casualties among first responders as the towers collapsed. Thereafter, with the overwhelming rush of surrounding cities aid, the Port Authority, NY Police Department, and various other agencies the federal government assumed authority of the area with the Federal Emergency Management Agency (FEMA) running the point. This essentially allowed FEMA to control the flow of information found and its distribution. For instance, according to an article assessing the National Institute of Standards and Technology (NIST):

The ASCE volunteering engineers were assigned the role of (BPAT) a Building Performance Assessment Team. Eventually, FEMA produced the first official report. This report indicated that the collapse of the towers was caused by the plane crashes and subsequent fires that ensued (National Commission on Terrorist Attacks, 2010).

Despite this initial, well intended activity, later; FEMA was blamed for a clean of the major evidence required for an in-depth investigation. This was not to be the final report, because later (NIST) the National Institute of Standards and Technology initiated 2 year fire safety and building investigation on the World Trade Center by 2002, August 21st. Later NIST produced and a metallurgical and mechanical analysis of the steel sampled from the collapsed skyscraper that seemingly contradicted the FEMA report (Arabseque, 2008).

This more so led to further questioning to include the fire analysis of due to other findings removed from ground zero. As witness accounts and recovered videos show the collapse of the two building happened in such symmetry that it resembled a controlled demolition. The chemistry portion of the investigation compared this occurrence to other high-rise and skyscrapers that were involved in major fires for long durations and have not found one that collapsed due to flame and heat impingement on its structural supports. Moreover, during further investigation of the steel members removed from the site were tested which produced traces of a thermite compound typically found in explosives. In other tests and simulation ran by the NIST are entertaining the evidence that the fire retardant coating on the structural supports were possibly defective or had eroded away in areas contributing to the weakening steel and eventually setting off the chain of events towards the collapse.

The attacks on 9/11 have raised more questions and theories than definitive answers. Fire investigators continue to be challenged with their own personal fire science experience and theories to confronting evidence by structural engineers and conspiracy theorists. And true to their jobs, fire investigators continued to search for answers to find cause for the collapse, physics of the collapse, and the overall scene analysis. While the true cause of the collapse may be never found fire investigators and other departments involved in safeguarding the nation have learned the deficiencies encountered on that day. Some studies are being conducted today to incorporate safety recommendations on new and proposed construction of high-rise buildings.

For example, the installation of glow-in-the-dark path markings in stairwells, The FireGrid system, developed over the past decade by Edinburgh University professor Jose Torero and funded by the BRE and Arup, comprises a system of sensors attached to a remote computer which can monitor the spread of fire throughout a tall building and provide vital forecasting information to emergency services (Building Design (May 4, 2007, future construction material, building codes, public notification systems, and enhanced emergency responder communication networks. All of these systems to some degree affected and were deficient during the attacks on the twin tower.

As a result the strides taken to better these systems have been exponential and it is my belief that technology will outpace the construction of high rises as more cities continue to construct such large building for commercial purposes. Moreover, due to the diligence of businesses to develop new options for construction materials, blast resistant materials have been introduced to the market offering new options. While the innovation fireproofing the structural members of a building have also been improved. According to investigative studies the fireproofing that was originally applied the WTC towers prematurely peeled off allowing longer contact and exposure to the heat and flames. New improvements to these products will allow it to adhere longer to support the evacuation of any facility.

In conclusion, all aspects of the events that occurred on September 11, 2001 still daunt structural engineers and fire investigators to this day. The fact that no agency has been able to produce a definitive and justifiable answer for these events bolsters many speculators and conspiracy theorist voices. Yet among all the chaos in understanding the scope of this attack, the finger pointing, and recovery of missing victims some positive improvements were developed. These improvements cover such things as illuminated stairwell markers that identify the direction of egress in poorly lighted stairwells, independent fire alarm and suppression systems that still activate in absence of electrical power, and an innovative system that electronically tracks the path of a fire or collapse from a remote station.

These types of innovations create answers for fire investigators and to a degree allow more effective efforts to develop solutions instead of blame. Lastly, the development of newer and more stringent high-rise building codes will prove to offer more safety to the public as developers and architects widen egress paths as more cities project continued commercial developments like these on their skylines. Collectively, we as first responders, police officers, and fire investigators wish that we never encounter this type of situation again but if something similar was to occur we will be better prepared.