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The Twin Towers of the World Trade Center in New York City have symbolized for over thirty years the economic possibilities and financial robustness of the Unites States of America. The North and South Towers of the World Trade Center each stood over 1,360-feet high and together contained more office space than any other building in the world. Each massive 110-story tower enclosed more than 1-acre of office space for each of the buildings’ floors. The towers were at one point the world’s tallest during the 1970’s (10, 34).

In less than two hours on September 11, 2001, eighteen terrorists were capable of hijacking four fuel-laden aircrafts and destroying them along with the Twin Towers and a portion of the United States Pentagon. Fatalities of these horrific attacks claimed the lives of 2,823 people in or around the towers, 123 at the Pentagon, and 266 on the planes. Each of the twin towers was originally designed to withstand hurricane-force winds, earthquakes, and ironically, the impact of a Boeing 707 inadvertently colliding with one of the towers at a speed of 200 miles per hour, the average speed of an aircraft upon landing.

The Boeing 707 was the largest commercial aircraft in the sky at the time the first tower opened in 1970. Unfortunately, the planes that destroyed the World Trade Center Towers were Boeing 767 jets fully tanked with 20,000 gallons of highly combustible jet fuel flying at speeds in excess of 500 miles per hour. Experts agree that it was the intense heat of this fuel, likely burning in excess of 850? C, and interior debris burning that ultimately caused the progressive collapse of the towers.

According to the Lamont-Doherty Earth Observatory of Columbia University, the collapse of each tower was estimated to be equivalent to the explosion of 23. 5 tons of TNT. The estimated area of Manhattan real estate that was razed or temporarily rendered unavailable due to the terrorist attacks exceeded 30 million square feet (9, 15). The hallow ground were the World Trade Center once stood in New York City, known as Ground Zero, is now a gaping hole in the Manhattan skyline.

These terrorist attacks that transformed a sunny autumn morning into one of the darkest days in our Nation’s history have had ramifications worldwide. Seven months after the attack, the aftermath still lives. Physical, mental, psychological, and economic consequences will be felt for years to come. Life in the United States, or anywhere in the world for that matter, will never be the same, “clouded with the new global nightmare of warfare that recognizes no country boundaries, allegiances or faith.

The construction industry’s role in protecting the personal safety of building occupants must change to address that nightmare” (7, 56). The September 11 terrorist attacks have had a profound and enduring affect on our economy, especially in the design and construction industry. Tentative insurance estimates for the losses due to the attacks exceeded $30 billion. A total of 700,000 of the nearly 4 million jobs in New York were impacted by the tragedy either directly or indirectly.

When trading resumed on September 17, the inevitable Dow Jones stock market slide erased an additional $590 billion worth of market equity in one single day (5, 25). Potential changes in the design industry to avert such future catastrophes will have economic consequences affecting owners, investors, designers, and workers. Moreover, the construction industry has been dramatically affected by the WTC attacks and by the ensuing uncertainty and reluctance of owners to proceed with the capital formation for current and future construction projects.

Until an extensive analysis is performed, it is difficult to completely anticipate how much building design will be reviewed and revamped in the aftermath of the tragic terrorist attacks. In the days immediately following the attacks, priority around Ground Zero was rightfully given to rescue and clean-up efforts. However, engineers from around the nation were allowed to inspect and assess the tower remains and surrounding buildings.

Information on how nearby buildings withstood effects from the attacks can provide valuable insight to engineers and designers in developing building codes that would allow more time for people to escape buildings that have sustained significant structural damage. The WTC attacks filled the nation and the world with fears of potential nuclear and chemical warfare. Civil defense and disaster control were suddenly at the top of design concerns. Experts agreed that evaluations should be done to assess the vulnerability of existing structures, but others cautioned of the hasty actions to carry out this task.

“On September 11, the vulnerability of structures didn’t change. Principally what changed was our perception of the threats. We have to be careful that we don’t get trapped into designing for the last threat when the next threat is out there”, said Robert Prieto, chairman of civil engineer Parsons Brinckeroff, Inc. (11, 9). The overall consensus was that few developers were going to insist that their building be designed to resist airplane attacks, but the attacks did serve as a notice, a chance for the risks of the engineered environment to be reassessed.

Prieto stated that the future of design criteria should incorporate the three R’s of threat design: Design to Resist threat, Design to Respond to threat, and Design to Recover from threat. Many groups have been organized to evaluate and learn from the attacks. The Structural Engineering Institute, SEI, of the American Society of Civil Engineers has formed The Infrastructure Security Partnership, TISP, to evaluate the tower failures. The goal of TISP is to bring together experts from all industry sectors to develop a comprehensive, multi-hazard force protection approach for the built environment.

SEI has also partnered with the American Institute of Steel Construction, the American Concrete Institute, The National Fire Protection Association, the Society of Fire Protection Engineers, and the Federal Emergency Management Agency to examine the aftermath and consider possible building code changes. According to Carl Baldassarra, P. E. , president of the fire-protection and security firm, Schirmer Engineering Corporation, “there needs to be a diligent, thought out, scientific analysis before we determine if and what should be done to change building design.

In the end, we’re going to have to find a balance between acceptable risk and building design” (1, 17). David Cooper, P. E. , senior vice-president of Flack & Kurtz and mechanical designer for the World Trade Center Towers, stated that potential design changes would eventually make their way to technical committees subject to review by building industry officials. Cooper also noted that the industry would not be affected by any such changes for nearly two years and the costs associated with these modifications would be significant.

Consequently, in the months after the attacks, engineers reported that their clients initiated changes in the building design. Gupta anticipates that fundamental design changes may begin with the elimination of features such as open atriums and underground parking (8, 138). According to Raj Gupta, P. E. , president of Environmental Systems Design, many companies cancelled their high-rise projects because they did not want to centralize their workforce. However, for projects already under construction, many owners and clients instructed their consulting engineers to revisit the security design.

Security was heightened to the extent that the General Services Administration, the American Institute of Architects, and the National Society of Professional Engineers issued a security warning to 300,000 members. The warning was sent via electronic mail instructing firms to report to the Federal Bureau of Investigation any unusual recent or past requests for specific building plans. Restrictions as such have the detrimental capability of impeding the communication channel for technological and resourceful information between viable sources (3, 27).

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