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Willis Tower

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Projects > Buildings
Looking up to the top of the Willis Tower
The Willis Tower, commonly refered to by its old name the Sears Tower, is a skyscraper in Chicago, Illinois. It was designed in the late 1960s to house Sears, Roebuck & Co. It reigned as the world’s tallest building from 1973 until 1996 when it was surpassed by the Petronas Twin Towers in Malaysia.

With 108 floors, the building currently stands 1,451 feet (442 m) high to its roof, with television antennas extending it to 1,730 feet (527 m). The tower was designed by Bruce Graham and Fazlur Khan, from the Skidmore, Owings & Merrill design firm. The tower cost US$175 million to build.

Contents

[edit] Construction History

[edit] Key Players

By the late 1960s, Sears, Roebuck & Co. was the number one retailer in the world.[1] Its headquarters, with 7,000 employees, was spread out amongst 10 different locations in Chicago. Sears chairman Gordon Metcalf wanted to centralize all operations under one roof.

However, before Sears was prepared to hire an architect, it hired an interior design team, SLS Environetics from New York, to perform studies on how much space was needed now and after 30 years of growth. SLS made the different Sears departments fill out questionnaires to decipher how best to allot office space. As a result of their research, SLS discovered Sears needed two million square feet (185,806 m2) presently, and 3.5 million square feet (325,161 m2) in 30 years.

Sears hired the Skidmore, Owings & Merrill firm with Bruce Graham as the head architect and Fazlur Khan as structural engineer. Graham and Fazlur had recently finished designing the John Hancock Center in Chicago.

[edit] Piecing it All Together

It was now time for the ironworkers to begin hoisting, bolting, and welding the large prefabricated pieces together.

Each iron piece, some as large as 15x26 feet (4.6x8 m), was transported on trailer trucks. Each piece was numbered so the workers knew exactly where it fit. The next piece to arrive on site was always the next piece to be raised. Nothing was stored on site. It ran like a well-oiled train. Two floors were being constructed per week.

“It had to take a lot of coordination between the fabricators, shipping and the truckers to make it all run smooth,” said Richard Gumer, crane operator on the Sears Tower.[2]

The raising gang would set the steel in place, and put one bolt in. The bolt gang would follow behind and bolt the entire piece. Surveyors would check to ensure the piece was straight before the welders welded it in place, finishing the job.

However, as well as the project appeared to be progressing, it still suffered hardships. Often weather conditions would hinder construction. In fact, from August through December 1972, ironworkers were unable to work an entire week because of the weather.

On May 3, 1973, a ceremony was held to celebrate the hoisting of the final iron piece into place. The piece was painted white allowing 15,000 Sears employees and construction workers to sign it.

Once framing was complete, the flooring was laid. In order to maintain the distribution of weight as much as possible, the direction of the flooring rotated 90 degrees every five floors.

After completion the tower leaned six inches (15 cm) to the West due to unbalanced distribution of weight resulting from the asymmetrical design.

[edit] Façade and Features

The tower's façade is made of a black aluminum curtain with bronze tinted windows.

The tower has 104 elevators, 14 of which are double-decker elevators. Two of the elevators are capable of reaching speeds of 1,600 feet (488 m) per minute.

There are five sets of two-story floors, which house immense mechanical systems in addition to providing integrity to the structure. Each of these floors are equipped with large x-braces on their frame, increasing the building’s strength and reducing lateral wind drift by 15 percent.

Revolving doors and air locks are located on the first floor to regulate temperatures and reduce “stack effect.” Stack effect is when hot air is released through the top of the building, forcing cold air to be sucked in at the bottom floor. In the fall of 1974, three-and-a-half years after construction began, the Sears Tower was completed on time and under budget.

[edit] Equipment Used

[edit] Refurbishment/Recent Projects/Renovations

Sears, Roebuck & Co. rehired Skidmore, Owings & Merrill in 1983 to renovate the lower level public space of the Sears Tower. They also built a large atrium at the entrance to the building. An architecture critic for the Chicago Tribune in 1985 wrote:

“The most striking change, of course, has come with the creation of a large new glassed-in entrance…it replaces a skimpy little marquee and an exposed outdoor staircase of 21 steps--which was a ridiculous entrance to a tower 1454 feet tall.”[3]

However, another writer for the Chicago Tribune critiqued the building again 10 years later:

“A lunchbox-shaped atrium tacked on the Wacker entrance in 1985 flopped miserably in its attempt to transform Sears into a pedestrian-friendly office building.”[4]

“Its lack of human scale was just one of Sears' ground-level woes. Lower floors were a maze of shops, elevator lobbies and escalators that bewildered visitors and tenants alike.”[5]

Another renovation was undertaken after Sears vacated much of the building. The company DeStefano + Partners renovated all of the public and skydeck lobbies and elevators. The company also constructed new glass canopies over two of the entrances.

On July 16 2009, it was announced that the name of the tower had been changed from the "Sears Tower" to the "Willis Tower".[6]

[edit] Unique Facts

  • A skydeck (observation deck) is located on the 103rd floor. It receives 1.3 million tourists annually.
  • More than 25,000 people walk into the Willis Tower every day.
  • The tower is 4.5 million square feet (418,064 m2), which includes offices, a private dining club, conference facilities, a U.S. Post Office, retail stores, and restaurants.
  • There are 2,232 steps to the top of the building.
  • There are six automated window washing machines to clean the 16,100 windows.
  • There are 796 bathrooms.
  • The tower employs 110 janitors, 100 security guards, 25 engineers, and three electricians.
  • There is a total of 50,000 miles (80,467 km) of electrical wiring, 25,000 miles (40,234 km) of plumbing, 80 miles (129 m) of elevator cable, and 145,000 light fixtures in the building
  • The tower houses five large chilling units providing 4,800 tons of refrigeration.
  • There are 3,000 thermostats.
  • The Willis Tower has never lost power; however, it houses two 2,100-kilowatt generators that have never been used.

[edit] References

  1. History Channel. Modern Marvels: The Sears Tower
  2. History Channel. Modern Marvels: The Sears Tower
  3. Gapp, Paul. Architectural giantism. SearsTower.org, November, 1985. (accessed: 2008-09-23)
  4. Ziemba, Stanley. Towering changes. SearsTower.org, October, 1993. (accessed: 2008-09-23)
  5. Ziemba, Stanley. Towering changes. SearsTower.org, October, 1993. (accessed: 2008-09-23)
  6. Willis who? Sears Tower gets new name. MSNBC [December 21, 2009].

[edit] External Links