The building was first acquired in 1989 by Boston's AEW Capital Management for the sum of $800 million. who established the iconic building as a destination for many new tenants over the course of almost five years. Management and leasing of the property was initially given to Chicago developer John Buck Co. Sears eventually chose to move its headquarters to a more human-scale suburban setting in Hoffman Estates leaving the tower nearly half vacant. Looking skywards on South Wacker Drive (© Randall Krause) Other resources erroneously claim that this lean is the result of unequal loads bearing on its foundations. Separate banks of local-service elevators would carry passengers to their final destination.ĭue to its excessive height, Sears Tower was designed to lean approximately six inches from normal to counteract for the rotation of the Earth - a fact that engineers later discovered was unnecessary. Designated transfer-floors would be served by banks of double-deck express elevators. had originally implemented in Chicago's own John Hancock Center. employed "skylobbies" for this purpose, a system which Otis Elevator Co. Designers had to ensure efficient flow of pedestrian traffic throughout the building which, on any given day, could number in the tens of thousands. The 101st floor is leased to broadcasters for housing of transmitter equipment.
Sears tower floor full#
Twin 67-foot cylindrical supports, both 12-feet in diameter, project from inside the roof to provide a rigid steel base for 159-foot communication towers, which are comprised of triangular supports and antenna pylons, all of which is encased in white fiberglass radome to prevent large diameter ice formation, extending the full building height. Sears Tower also provides facilities for broadcasting to the Chicago metropolitan area. Currently, they operate eight times per year. Another technological innovation was the robotic window washers that could be programmed to descend along tracks built into the curtain wall. For fire, security, and HVAC monitoring and control, engineers opted for a Honeywell computer system, one of the largest such networks ever installed at the time. wind-induced sway).īuilding automation was a primary design consideration as well.
To aid in occupant comfort, belt trusses were rigged on the upper mechanical floors thereby further reducing shear forces (i.e. It allowed for large open office spaces on the lower levels, where Sears, Roebuck and Company would reside, and smaller floor plates on the upper levels with unobstructed views of the cityscape. This "bundled-tube" configuration was a revolutionary engineering concept at the time, pioneered by SOM's very own Fazlur R.
as implemented in the World Trade Center towers.) This is in contrast to the popular tube-in-tube system, in which a rigid network of floor diaphrams and closely-spaced exterior columns work in unison to resist lateral loads whereas a centralized core functions to carry vertical loads exclusively (e.g. Each tube is a rigid steel frame that performs in tandem with its neighbor to efficiently counteract all lateral and gravity loads. The superstructure consists of nine interlocking tubes that terminate at different heights, creating the iconic stepped-back appearance of the tower. Sears Tower was the last supertall building constructed during the International architecture period, and SOM's interpretation of the style is remarkably bold and awe-inspiring. Much like the Empire State Building, the colors typically coincide with national events and holidays. By the fall of 1995, a seasonal rooftop illumination program was also initiated.
This also included the construction of two glass-and-steel canopies over the Franklin Street and Jackson Street entrances. Following Sears' departure, the building underwent a comprehensive renovation by DeStefano + Assoc of all public and Skydeck lobbies and elevators. In 1984, SOM was commissioned to overhaul many of the tower's lower-levels, including the addition of a vaulted atrium alongside Wacker Drive. Both were surpassed within their first year of completion by Sears Tower, which opened its doors on September 10, 1973. Originally designed in the late 60's by Bruce Graham of Skidmore, Owings, and Merrill for Chicago-based Sears, Roebuck and Co, Sears Tower was officially topped out on May 3, 1973.ĭuring the skyscraper's initial construction, which began in August of 1970, two other prominent office tower projects vied for the "world's tallest" title: the Standard Oil of Indiana Building (now the Aon Center) located in downtown Chicago and the World Trade Center high-rise complex formerly located in Manhattan. Modern versus classic in Chicago's Loop (© Randall Krause)
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