The Fall of Twins

Introduction

On September 11, 2001, the whole world watched as the towering symbols of American economic might crumbled down the streets of lower Manhattan. The collapse of the World Trade Center Twin Towers left everyone in disbelief. The chain of events were so abrupt, anxiety filled the streets of New York.

It has been said that the buildings design were structurally deficient, that the steel trusses melted and gave way, or the sprinkler system failed to suppress the fire. Most reports are insufficient and some are incorrect.

This paper will explain the details of the collapse including additional information about the World Trade Center Twin Towers. Quantitative and qualitative reasoning can help sort facts and data from, literally, a mountain of metal and debris. Consequently, this can help us learn from this unfortunate tragedy.

History

The World Trade Center, along with so many great structures, will not only be remembered for their breathtaking design and engineering, but also as a symbol of mankind’s imagination and vision of the future.

In the 1960s, a massive urban-renewal project was being implemented at the lower Manhattan area of New York City. Under the motivation of former governor Nelson A. Rockefeller and his brother, David Rockefeller, the World Trade Center Twin Towers were conceptualized. It was envisioned as “a living symbol of man’s dedication to world peace.” American architects Minoru Yamasaki and Emery Roth designed the buildings. It took seven years to build and earned its placed among New York’s best-known landmarks, along with the Statue of Liberty and the Empire State Building.

"World trade means world peace, and consequently the World Trade Center is a living symbol of man's dedication to world peace," Yamasaki, the chief architect, once said. The center "was a representation of man's belief in humanity, his need for individual dignity, his beliefs in the cooperation of men, and through cooperation, his ability to find greatness."

The towers served more than a location for industry. "It symbolizes modern architecture in the 20th century," says Wendy Evans Joseph, chairman of the American Institute of Architects Committee on Design. "It is a symbol of New York."

After it was erected, it became the most valuable commercial property in the history of New York City. The twin towers stood over Manhattan’s skyline for nearly three decades as an icon of financial power.

They were the world's tallest buildings, costing more than a billion US dollars, until the Sears Tower was completed in Chicago in 1974.

In addition to the twin towers, the complex had a 47-story office building and two nine-story office properties. In July, the towers were leased in a record-setting $3.2 billion real-estate deal with private investors.

"This is a dream come true," New York developer Larry Silverstein said after cinching his deal to lease the center for 99 years with Los Angeles-based shopping-center developer Westfield America and investor Lloyd Goldman. Silverstein said he had dreamed of owning the WTC since his company, Silverstein Properties, moved into 7 World Trade Center years ago, a smaller building beside the towers. That building collapsed as well.

General Information

The towers were planned and built in the mid-1960s up to the 1970s. They represented a new approach to buildings, to be precise, skyscrapers, in that they were to be very light in terms of weight and involved organized construction methods in order to hasten the time table for construction and, more importantly, to reduce the costs.

The World Trade Center, with 43,000 windows, nearly 200 elevators, an observation deck, the Windows on the World restaurant and 10 million square feet of office and retail space is truly an engineering marvel. The twin towers, one 1,368 feet high, the other 1,362 feet high, each contained 130,000 tons of steel and has a net weight of about 300,000 tons.

Traditional skyscrapers used evenly spaced support columns. They contained huge columns and contained massive amounts of masonry carrying some of the structural load. The innovative design of the World Trade Center buildings is their central core and moving most of the support columns to the outer wall. Thus, the towers looked as if they had no windows. The key to the design are the series of steel floor beams and trusses that connected the supporting columns of the outer wall to the inner core which houses the elevators, stairwells, and other utilities. Consequently, it created larger floor space and less hindrance all over the work area. The trusses acted as flooring which were later covered with concrete. The central core was designed to support the entire weight of the building and the supporting columns as a fail-safe precaution.

The positive design and lightweight construction materials used were not bottlenecks to the overall capabilities of the buildings. The buildings’ design proved to be one of the most redundant and one of the most resilient structures ever built. The finis

Just like any other skyscraper, the towers are design to withstand hurricane-force winds, earthquakes, fire and tested through other situations that may result thereof.

Timeline of Events

At 8:45 a.m. Eastern Standard Time (EST), American Airlines Flight 11, a Boeing 767 hijacked en route from Boston to Los Angeles with 92 passengers aboard, slams into the North Tower. 21 minutes later, at 9:06 a.m. EST, United Airlines Flight 175, also a Boeing 767 hijacked en route from Boston Los Angeles with 65 passengers aboard, banks hard and slice through the South Tower.

Immediately upon confirmation, President George W. Bush calls the crashes an �apparent terrorist attack,’ as hundreds of rescue workers and volunteers arrive at the World Trade Center to evacuate the buildings.

At around 9:50 to 10:00 a.m. EST, the inevitable happened. The South Tower collapses, killing and injuring thousands and sending a plume of smoke spiraling down the streets. Weakened by its imploded twin, at 10:29 a.m. EST, the North Tower collapses causing even more devastation and blanketing downtown Manhattan in ash and debris.

Collapse Explained

Design

The steel structure is made up of 61 columns on each side of the square towers, steel columns around the elevator core, and steel truss beams supports the floors. They were protected from fire and heat using fire retardant

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