Abstract
The September 11, 2001 terrorist attacks were a series of four suicide attacks on the US (CNN, 2013). Four passenger jets were hijacked by 19 Islamic terrorists operating under the group al-Qaeda. Two planes were crashed into the Twin Towers of the World Trade Center. The two towers collapsed in a matter of two hours. A third plane was crashed onto the Pentagon while the fourth plane crashed in Pennsylvania when passengers tried to take over the plane from the hijackers who were aiming at Washington D.C. Almost 3,000 people died during these attacks. These attacks have led to major consequences in a variety of fields. Some of these fields include politics, military policies, foreign relations, structural engineering, film, literature, culture, building and construction (CNN, 2013).
Everybody was shocked by the collapse of the Twin Towers. Specialists could not comprehend how the buildings had collapsed given the expert skills that had been put into place during construction. Investigators had numerous questions which they were trying to figure out the answers. WTC1 stood almost double the period WTC2 stood after being hit by the plane (Charles, 2011). The World Trade Centre Building 7 fell after seven hours despite not being hit by the plane (Don & Hoffman, 2012). As the investigators were trying to figure out the answers to these questions, they were also wondering whether a repetition of the same could happen to other buildings in the rest of the country. Looking for answers to these questions has helped in solving the mysteries and has also led to changing of the international building codes. The changing of the building construction codes is aimed at preventing tragedies from happening in the future.
One of the major challenges faced by the investigators was the lack of evidence due to destruction by the disaster. The buildings and structures were destroyed to the extent that they could not be recognized. The destruction was so severe that some of the pieces could not even be reconstructed (Charles, 2011). The leading team of investigators was the National Institute of Standards and Technology (NIST). Despite their high level of skills and expertise, the remains of the disaster posed a big challenge to them in their fulfillment of their duties.
NIST collected any piece of evidence they could get so as to enable them reconstruct the ordeal of the twin towers before and after the disaster. They were able to collect pieces of steel totaling to 236. These pieces of steel came from both the buildings and the planes. They also gathered 7,000 photographs from photographers and media (Charles, 2011). They went through the documentation of the original engineering records of the building and interviewed witnesses of the attacks and also the people who had participated in the construction of the buildings. They also interviewed people who were responsible for the maintenance and designing of the buildings. Lab tests concerning heating of structures and large fires were also carried out.
NIST then created models to show how the towers were destroyed on impact, how the fuel was transmitted, how the fires razed the floors, how the buildings’ structures contacted heat and how failure came about. These computer models were complex because accuracy was required. There were times when the simulations did not work and therefore the investigators had to reinvent new models (Charles, 2011). The conclusion drawn by NIST was that the fires and planes were not enough to destroy the buildings. They stated that the size of the structures would have withstood the impact of the plane crash. They also concluded that even intense fire could not have led to the collapse of the buildings.
According to NIST, the impact led to the dislodgement of fireproof insulation which was used to coat steel on the columns and floors. This led to the weakening of metal which was left exposed to the direct heat. The sprinklers which had been set up in the ceiling failed to work because there was no water supply due to cut off by the collisions. It was also discovered that WTC2 took a shorter time to collapse than WTC1 because the plane crash had a huge impact on its core building. The towers had a capacity of 40,000 people, but luckily, the towers were not fully occupied thus comprised of an estimated 17,400. A total of 2,749 died in the attack (Charles, 2011).
NIST also found out that the reason that led to the collapse of WTC7 was that it caught fire when the burning debris fell on it. The debris came from WTC1. The sprinklers also failed to work because they got damaged when the Twin Towers fell. The fire led to the expansion of the girders and steel beams making the structure weak and leading to the collapse of the building. The collapse of WTC7 was therefore, as a result of uncontrolled fires.
The forensic analysis by NIST from the September 11, 2001 terrorist attacks has led to the issuance of 31 recommendations aimed at improving safety and procedures to be carried out in the event of emergencies (Charles, 2011). These recommendations have been criticized by critics especially because of the costs to be incurred. One of the critics is the General Services Administration. The critics are not totally convinced on issues regarding the benefits of these changes. The critics argue that there was no consensus concerning the results of the investigations. They also say that the benefits that are expected to be realized by the implementation of these recommendations are not convincing.
In the earlier days after the release of the recommendations, people were easily accepting them. Examples include the undertaking of NIST in the investigation of buildings to measure whether the buildings were ready for earthquakes. The engineering community offered NIST a lot of support and readily accepted the recommendations. People were however, critical about the investigation of the World Trade Center because it was not open to people’s review and it was conducted under a lot of security. The recommendations by NIST led to the changing of the international Codes to accommodate the new ideas. In the year 2009, a total of 23 changes were made to the international codes. In the year 2012, 17 more changes were made to the codes. These building and construction codes are accepted and practiced by the local and state authorities.
Some of these recommendations include: tall buildings over 420 feet must have an additional stairwell exit or elevators that can aid evacuations; the stairwells in buildings standing over 75 feet must have markings which glow in the dark so as to enable people to make their way out of the building in case of emergencies; and spray applied fire resistive materials should be four times as effective as those of the present buildings for buildings towering between 75 feet and 420 feet while those buildings over 420 feet should be seven times more effective. These changes in construction codes are geared towards the safety of people.
The ICC looked at the recommendations and set forth codes which were aimed at promoting safety. Their intention was to control the effects of terror activities through the provision of proper codes which would enable the prevention of loss of lives and damages. All the changes that had been proposed were not successful, but many were adopted. Some of the codes were involved high costs while others were cheap. The overall results were the huge potential benefits that these changes in the building construction codes carried.
Other changes incorporated in the international codes of building as a result of the September 11, 2001 include: The inclusion of elevators in buildings rising above 120 feet to enable the firefighters to reach fires easily and fight fires without the hassle of moving up and down with heavy equipment; using exit stairways and shafts made from materials with high resistance to impact; and use of radio systems in the building to enable the evacuating team to communicate to the victims and also to their support outside the building (Penwell, 2014). Owners of the buildings are also told to exercise vigilance and adopt extra measures based on their assessment of the risks and threats faced.
The 17 changes adopted by the International Code Council (ICC) in the year 2012, affect the construction, fire safety and design (David & Gene, 2011). These changes include:
- Two elevators for the fires service reaching the lowest floors where the fire fighters can access.
- Consistent evacuation plans in all jurisdictions.
- Inclusion of information cards.
- Use of elevator recall.
- Constant supply of water through automatic systems.
- Elevator lobby doorways.
- A standpipe should be able to gain access to all floors.
- Fire service elevators should have standard markings.
- Availability of passenger elevator recall.
- There should be passenger elevators which are activated upon fire alarm.
- There should be radio coverage.
- There should be roof assemblies that are not connected to the columns of the buildings.
- The egress width should be checked and measured to suit the standards set.
- There should be automatic sprinklers.
- The lobby enclosure should be safe.
- There should be controlled wiring.
- The width of the stairs and corridors should be up to standards.
In conclusion, the collapse of the Twin Towers due to terrorist attacks highlighted the structural mistakes that had been made by the previous engineers. The results from the investigations showed that US was not well prepared for terrorist attacks of such magnitude. This prompted the state to make changes in the construction codes of buildings. There are requirements that every company needs to adhere to so as to ensure the safety of people in the event of emergencies.
References
David D. & Gene C. (2011). Evolution of Building Code Requirements in a Post 9/11 World. Retrieved from http://www.ctbuh.org/LinkClick.aspx?fileticket=%2BYb7cly6880%3D&tabid=2684&language=en-US
Charles Q. C. (2011). Twin Towers Forensic Investigation helps revise Building Codes Despite Critics. Retrieved from http://www.scientificamerican.com/article/twin-towers-forensic-investigation-revise-building-codes/
Penwell, (2014). Building Safety Codes Changed as a Result of 9/11. Retrieved from http://www.fireengineering.com/articles/2011/08/9-11-code-changes.html
CNN, (2013). September 11 Anniversary Fast Facts. Retrieved from http://edition.cnn.com/2013/07/27/us/september-11-anniversary-fast-facts/
Don P. & Hoffman J., (2012). Building 7. Retrieved from http://911review.com/attack/wtc/b7.html
