Sears Tower stands tall, over 1,700 feet aloft, overlooking the west side of Chicago's downtown Loop. Clad in bronze-tinted glass and stainless aluminum, rising with determination yet elegance from the depths of its grand foundations to the tips of its massive spires, luring tourists in daze, housing a workforce of thousands, the Big Store represents an era in Chicago of optimism and opportunity that will not be forgotten.
Currently, Sears Tower is the second tallest building in the world. At 1,729 feet, it is superceded only by the United Arab Emirates' Burj Khalifa in structural height. Since its completion in 1974, it still remains the tallest skyscraper in the U.S.
During 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. Both were surpassed within their first year of completion by Sears Tower.
In 1984, SOM was commissioned to overhaul many of the tower's lower-levels, including the addition of a vaulted atrium alongside Wacker Drive. Following Sears' departure, the building underwent a comprehensive renovation by DeStefano + Assoc of all public and Skydeck lobbies and elevators. This also included the construction of two glass-and-steel canopies over the Franklin Street and Jackson Street entrances. By the fall of 1995, a seasonal rooftop illumination program was also initiated. Much like the Empire State Building, the colors typically coincide with national events and holidays.
The superstructure consists of nine interlocking tubes that terminate at different heights, creating the iconic stepped-back appearance of the tower. Each tube is a rigid steel frame that performs in tandem with its neighbor to efficiently counteract all lateral and gravity loads. 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. as implemented in the World Trade Center towers.)
This "bundled-tube" configuration was a revolutionary engineering concept at the time, pioneered by SOM's very own Fazlur R. Khan. 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. To aid in occupant comfort, belt trusses were rigged on the upper mechanical floors thereby further reducing shear forces (i.e. wind-induced sway).
Building automation was a primary design consideration as well. 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. Another technological innovation was the robotic window washers that could be programmed to descend along tracks built into the curtain wall. Currently, they operate eight times per year.
Sears Tower also provides facilities for broadcasting to the Chicago metropolitan area. 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. The 101st floor is leased to broadcasters for housing of transmitter equipment.
Vertical transporation was also crucial. Designers had to ensure efficient flow of pedestrian traffic throughout the building which, on any given day, could number in the tens of thousands. Westinghouse Electric Corp. employed "skylobbies" for this purpose, a system which Otis Elevator Co. had originally implemented in Chicago's own John Hancock Center. Designated transfer-floors would be served by banks of double-deck express elevators. Separate banks of local-service elevators would carry passengers to their final destination.
Sears eventually chose to move its headquarters to a more human-scale suburban setting in Hoffman Estates leaving the tower nearly half vacant. Management and leasing of the property was initially given to Chicago developer John Buck Co. who established the iconic building as a destination for many new tenants over the course of almost five years.
The building was first acquired in 1989 by Boston's AEW Capital Management for the sum of $800 million. However, despite successfully bringing occupancy up by 40 percent during its term of ownership, AEW could not profit leasing space to its roster of tenants due to a continued downtown real estate depression and lower than average rental rates within the Tower.
In late 1997, the landmark tower was sold for $804 million to Toronto-based TrizecHahn, a REIT (real estate investment trust) firm. Downtown property markets subsequently began to show signs of recovery, and Sears Tower was again becoming one of Chicago's most prestigious high-rise properties. In fact, to honor Sears Tower's principal structural engineer, an adjacent street was, following a ceremony in the building, dedicated "Fazlur R. Khan Way" on July 7, 1998 by the City of Chicago.
To meet the growing demands of the digital age, Sears Tower was upgraded March 8 of 2000 with four combination antennas, each 29.4-feet, 2890-lbs mounted on 80-foot towers at the four corners of the roof. An Erickson S-64F Aircrane was used to lift the load from the top of the parking garage skyward about one quarter mile. Four city blocks were closed off during the massive operation. However, the addition would ensure that the Chicago area was capable of receiving HDTV.
On June 4, 2000, the 220-foot western communications tower had to undergo modifications to increase the signal quality of Chicago's local NBC television station. This necessitated disassembling the existing framework via hellicopter and installing a new 75-foot, 19250-lb stack of self-supporting antenna pylons for WMAQ-29, WLS-52, and WPWR-52/22 on top of the existing support tower, thus raising the height of the building to 1729 feet.
Following the attacks of September 11, 2001, however, the status of Sears Tower as a viable investment opportunity proved questionable. Trizec Properties Inc. finally transfered ownership to its lender, MetLife Inc., in August of 2003 after facing the growing possibility of defaulting on its mortgage. Less than one year later, however, MetLife sold its stake in the building outright to a group of three investors (including two of Larry Silverstein's group), thereby forming 233 South Wacker LLC.
The building was leased and managed by real estate firm CB Richard Ellis Inc. until 2007 when responsibilities were assigned to Chicago-based U.S. Equities Realty LLC. Seeking to revitalize and redevelop Sears Tower, owners have announced numerous "green initiatives", including possible LEED certification, aimed at reducing energy costs and positioning the Tower as a more attractive and eco-friendly destination for new tenants. Visionary plans to "paint" the building silver were also briefly considered, but never left the drawing room table.
The entire building has also undergone significant security improvements since 2001. Johnson Controls' Hillside office was awarded the contract to install various barricades along all street-level entrances, X-ray metal detectors in the main concourse, and electronic turnstile portals around the elevator lobby. Additionally, visitors now wishing to do business in the tower must sign-in at a security checkpoint. Any unidentified person will be immediately escorted out of the building by armed security officers.
As of 2010, Sears Tower remains the tallest skyscraper in the western hemisphere and one of the largest office buildings (in rentable square footage) in the United States. It also maintains the title of the world's tallest steel-framed building.
Annually 1.3 million people visit the observation deck alone, making The Big Store the 7th most popular tourist destination in Chicago (Source: Chicago Tribune, Sept 14, 2006). In addition, a recent public poll conducted by the American Institute of Architects, in commemoration of its 150th anniversary, ranked Sears Tower as America's third favourite Chicago architectural landmark.
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