SEARS TOWER FLOOR UPDATE

While the tubes connectat each floor level with beams and floors trusses, several large trussed levels act as the main horizontal connectors in the buildings. These tubes are independently strong but are further strengthened by the interactions between each other through truss connections. As the columns rise up the building, each square in the plan forms a tube, which can be seen on the exterior of the building. Each square has 5 columns per side spaced 15 feet on centers, with adjacent squares sharing columns. The building plan consists of 9 squares, each 75 feet across, placed in a three-by-three grid arrangement(Figure 2). The Willis Tower draws its strength, both visual and physical, from its structural form, the bundled tube. The dark bands represent the truss levels. 2: Seven of the nine ‘tubes’ discontinue at certain levels creating various floor plans. However, Sears and Graham both wanted something distinctive, not another ‘Big John’. As the building contained an excess 2 million square ft compared to the initial space demand, Sears needed to consider various tenant requirements, and the shape of the John Hancock Center was similar to what they needed.

In that building, he had used another innovative structural system, the braced tube, which tapered towards the top to provide for various tenant requirements. 9 Khan had already worked on another Chicago project, the John Hancock Center, with architect Bruce Graham. This bundled tube system gave the building its physical strength while saving Sears $10 million as compared to pre-existing structural systems. 8 This would change the building into an 80-story tower, but only if SOM could make it cost-effective.įazlur Khan, the engineer selected to work on the project, came up with the structural system that defined the Sears Tower. Instead, SOM determined by performing its own studies that departments could save significant amounts of time by stacking two 55,000 square ft stories on top of one another. Also looking for a cost-effective solution, Sears pictured a large 40-story cube. Sears performed several studies about the company’s project growth and current business practices and concluded that their current and future space requirements were 2 and 4 million square ft, respectively 7, with a floor area of 110,000 square ft per department. It was only after Skidmore, Owings and Merrill (SOM), a structural engineering and architecture firm based in Chicago, got involved that the building took its final form. 6 However, height did not initially concernSears, as the original Tower design differed greatly from the final design. above sea level, or 1450 ft above ground. 5 The only remaining obstacle to build higher was the Federal Aviation Administration, which set the maximum building height for Chicago at 2000 ft. 4 Daley also lifted the height restriction on buildings through a zoning ordinance revision in 1955 the ordinance changed the maximum building height to sixteen times the area of the lot. He was keen on the commerce that Sears’ headquarters would bring to the Chicago Loop area, which was partly undeveloped land. The company found support from Chicago’s mayor, Richard Daley. 3 However, Sears needed Chicago’s support in order to make their move to the city center at South Wacker Drive. 2 With a net income of $441 million that year, the company could financially support the development of an impressive modern building.

SEARS TOWER FLOOR UPDATE

By 1969, Sears was the largest retailer in the nation, and looking to update their outdated headquarters. 1 In the mid-1920s, Sears transitioned from the mail order business into regional stores. In the years that followed, thesmall company grew tremendously, becoming the largest mail order business in the world by 1906. Sears, Roebuck and Company was incorporated in 1893 by Richard Warren Sears and Alvah Curtis Roebuck. This company, who commissioned the building as their new headquarters in the early 1970s, played an integral role to the final form and size of the Tower. Originally, the Willis Tower was called the Sears Tower, after Sears, Roebuck & Company. The name change will stand for the duration of their ten year lease. In 2010, the building was renamed the Willis Tower after Willis Group Holdings, a London insurance broker and currently the largest tenant of the tower. Major Works Sears Tower (currently Willis Tower)įig 1: The Willis Tower (formerly Sears Tower) dominates the Chicago skylineĬhicago natives now affectionately call the Willis Tower ‘Big Willie’, (Figure 1) to go with ‘Big John’, the John Hancock Center, and ‘Big Stan’, the former Standard Oil Building, a sign that the city may finally be accepting the building’s new name.

Sears tower floor