Terri Meyer Boake BES BArch MArch LEED AP
Professor :: School of Architecture :: University of Waterloo

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The Chicago Skyscraper

From the Reliance Building to the Sears Tower

part two: the modern period


skyscrapers page one

part two: the modern period

Steel framing continued to be the structural system of choice from post Chicago Tribune Competition times, to the present day. Fire proofing methods have changed over the years, as well as flooring and cladding systems. The terra cotta and masonry facade with "window systems" have largely given way to aluminum and stone curtain wall systems. Mies Van Der Rohe's mark can be seen throughout central Chicago, whether it be the famous black curtain wall buildings for which he became so noted, or for versions of the same "by others". Many of the large urban sculptures that populate the modern era plazas are also constructed of steel


Images:
Federal Center: Ludwig Mies Van Der Rohe, 1959-75::
The Federal Center and the IBM Building are the two most famous buildings by this architect in Chicago. A Calder sculpture sits in the front plaza. The lower Post Office Building is under renovation (2005).
Close-up detail of "Flamingo" by Alexander Calder. The sculpture makes use of plate steel, expressing its splices and connections through exposed mechanical fastenings.
Equitable Building: Skidmore, Owings and Merrill, 1962-65::
The glazed bronze solar glass facade recalls the form of the Mies towers.
The building is set back from Michigan Avenue to make room in its plaza for public art, such as the steel sculpture pictured above.
Lake Shore Drive Apartments: Ludwig Mies Van Der Rohe, 1949-51::
The two black towers pictured in the L configuration (as viewed from the Hancock observation floor) became famous as some of the first truly "modern" apartment buildings in Chicago. These represented some of Mies early work upon coming to America post WW2. With these Mies encountered his first issues with North American fire codes that would not permit the exposed steel frame on the interior of his buildings -- such as had been acceptable in is earlier European efforts.
Aerial view of Chicago, taken from the observation deck of the Sears Tower. The John Hancock building in the distance... the Federal Building the black box towards the bottom right of the photo.
John Hancock Center (left): Skidmore, Owings and Merrill, 1968-74::
The 100 storey building uses large X braces, exposed on the exterior of the frame to stiffen the structure against wind loads. The braced tube is so efficient that only 29.7 pounds of steel per square foot were required. The tube allowed for the elimination of interior columns.
Detail view of the corner of the tower, at the intersection of the X bracing. These were clad in the same system as the balance of the curtain wall, and resulted in remarkably minimal intrusion to the interior office layout with respect to window loss.
Sears Tower: Skidmore, Owings and Merrill, 1968-74::
At 110 stories and 1,454 feet high, this is still amongst the tallest buildings in the world. A system of 75 foot square structural tubes is used for stability, to brace against wind forces. Nine of these form a square grid at the base, with only 2 extending the full height of the tower. Post 9/11 sees airport type security screening to gain access to the observation deck.
Here can be seen one of the major setback conditions immediately below the top extension of the tower. On extremely windy days it is not unheard of to evacuate the topmost portion of the building due to the ill effects of excessive wind sway. While such sway is not dangerous to the structure, it can make occupants feel uncomfortable, and remains one of the hinderances to the construction of such tall towers.
Contemporary Steel Framed Building, 2005::
Steel continues to be the material of choice for skyscraper construction in Chicago.
Sprayed on fireproofing covers the WF frame.
The buildings proceed in a "fast track" process, with cladding installed over the floors where fire protection is complete, while steel contines to be erected at the top of the building.
A detailed view of the steel flooring system, that is supported via a secondary set of WF beams.

 

These images are for educational use only and may not be reproduced commercially without written permission. tboake@sympatico.ca

Updated February 11, 2021