# United Steelworkers Building

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This article is about the building in Downtown Pittsburgh. For the building in Allegheny Center, Pittsburgh, see [IBM Building (Pittsburgh)](/source/IBM_Building_(Pittsburgh)).

The **United Steelworkers Building**, originally named the **IBM Building** and also known as the **I.W. Abel Building** or **Five Gateway Center**,[8] is a highrise office building in [Downtown](/source/Downtown_Pittsburgh) [Pittsburgh](/source/Pittsburgh), [Pennsylvania](/source/Pennsylvania). It was built by the [Equitable Life Assurance Society](/source/AXA_Equitable_Life_Insurance_Company) in 1961–64 as part of the [Gateway Center](/source/Gateway_Center_(Pittsburgh)) project which redeveloped a large portion of the area known as [the Point](/source/Point_State_Park). The building is listed on the [National Register of Historic Places](/source/National_Register_of_Historic_Places) as a [contributing property](/source/Contributing_property) in the [Pittsburgh Renaissance Historic District](/source/Pittsburgh_Renaissance_Historic_District)[1] and has been designated as a [Pittsburgh landmark](/source/List_of_Pittsburgh_History_and_Landmarks_Foundation_Historic_Landmarks) by the [Pittsburgh History and Landmarks Foundation](/source/Pittsburgh_History_and_Landmarks_Foundation).[2]

The building was designed by [Curtis and Davis](/source/Curtis_and_Davis_Architects_and_Engineers), a [New Orleans](/source/New_Orleans)–based architecture firm, with structural engineers [Worthington, Skilling, Helle & Jackson](/source/Magnusson_Klemencic_Associates). The design of the building, featuring a load-bearing steel [diagrid](/source/Diagrid) exoskeleton, was highly unusual at the time and helped pioneer the use of diagrids and [framed tube](/source/Tube_(structure)) construction.

## History

The building was developed by the [Equitable Life Assurance Society](/source/AXA_Equitable_Life_Insurance_Company) as part of the [Gateway Center](/source/Gateway_Center_(Pittsburgh)) project, which transformed an area consisting primarily of old [warehouses](/source/Warehouse) into a modernist office park. The IBM Building was built on the site of the former [Wabash Terminal](/source/Wabash_Pittsburgh_Terminal) [train shed](/source/Train_shed), which had been demolished in 1953. Workers had to remove 104 large concrete piers from the former station during construction.[9] Ground was broken on December 5, 1961[3] and the completed building was dedicated on March 19, 1964.[5]

The building's original tenants were [IBM](/source/IBM), occupying floors 1–4, and [U.S. Steel](/source/U.S._Steel) on floors 5–13.[7] The building was purchased in 1973 by the [United Steelworkers](/source/United_Steelworkers) [labor union](/source/Labor_union),[10] which has continued to own and occupy it since. In 1989 it was officially renamed for former USW president [I.W. Abel](/source/Iorwith_Wilbur_Abel).[11]

## Architecture

The design of the IBM Building was highly unusual at the time of construction in that the exterior of the building is load-bearing, unlike conventional high-rise architecture which used post-and-beam type [steel](/source/Steel_frame) or concrete framing with exterior [curtain walls](/source/Curtain_wall_(architecture)). The IBM building is supported by a steel exoskeleton resting on eight piers, two on each side of the building, along with a central core containing elevators and other utilities.[12] The remainder of the interior is free from structural supports, allowing a completely open floorplan.[13] This was one of the earliest examples of "[framed tube](/source/Tube_(structure))" construction,[14] which was later used extensively to build [supertall](/source/Supertall) structures like the [John Hancock Center](/source/John_Hancock_Center) and [World Trade Center](/source/World_Trade_Center_(1973%E2%80%932001)). In fact, the structural engineers for the IBM Building, [John Skilling](/source/John_Skilling) and [Leslie E. Robertson](/source/Leslie_E._Robertson), were also responsible for the World Trade Center. The *[Pittsburgh Post-Gazette](/source/Pittsburgh_Post-Gazette)* called the IBM Building "one of the first real changes from conventional design in half a century of multi-story building."[15]

The building was also one of the first to utilize a [diagrid](/source/Diagrid) (diagonal grid) structure, which requires less steel than a conventional frame.[16] The building frame does not contain any vertical members except for the six columns that support the utility core.[17] This type of structure was difficult to build at the time, though construction advances have since made it possible to build much larger diagrid buildings like [30 St Mary Axe](/source/30_St_Mary_Axe).[16] The IBM Building diagrid structure is constructed from 252 prefabricated sections which were hoisted into place and welded together.[4] The exterior of the building is covered with a skin of stainless steel and glass panels in alternating rows.[12]

Another unusual feature of the building is that the frame is constructed from different grades of steel depending on the strength requirements of each structural member. This was a departure from conventional structural engineering, where the material would typically be chosen at the outset. Instead, the engineers devised the frame geometry first and then calculated the required [yield strength](/source/Yield_strength) for each member, refining the design [iteratively](/source/Iteration). The steel used in the building was supplied by [U.S. Steel](/source/U.S._Steel) and varied from [plain carbon steel](/source/Plain_carbon_steel) with a yield strength of 36 [ksi](/source/Pounds_per_square_inch) (250 [MPa](/source/Pascal_(unit))) to high-strength [alloy](/source/Alloy_steel) with a yield strength of 100 ksi (690 MPa).[18] The steel beams were [color-coded](/source/Color_code) during construction to ensure the frame was assembled correctly.[19]

## References

1. ["National Register of Historic Places Registration Form: Pittsburgh Renaissance Historic District"](https://npgallery.nps.gov/GetAsset/9bd54cee-5aeb-4d8e-982f-6ad287c99628/) (PDF). National Park Service. May 2, 2013. Retrieved April 22, 2021.

1. [*Historic Landmark Plaques 1968–2014*](https://phlf.org/wp-content/uploads/2007/09/Plaques-1968-2014.pdf). Pittsburgh: Pittsburgh History & Landmarks Foundation. 2014. p. 19. Retrieved April 20, 2021.

1. ["IBM Breaks Ground For Gateway Office"](https://www.newspapers.com/clip/76226506/the-pittsburgh-press/). *Pittsburgh Press*. December 5, 1961. Retrieved April 22, 2021. – via Newspapers.com.

1. Thomas, George (November 9, 1962). ["Ceremony 'Tops' IBM Building"](https://www.newspapers.com/clip/76266972/the-pittsburgh-press/). *Pittsburgh Press*. Retrieved April 22, 2021. – via Newspapers.com.

1. ["IBM Building Dedication Set"](https://www.newspapers.com/clip/76268023/the-pittsburgh-press/). *Pittsburgh Press*. March 17, 1964. Retrieved April 22, 2021. – via Newspapers.com.

1. ["United Steelworkers Building"](https://web.archive.org/web/20151208123918/https://www.emporis.com/buildings/121909/united-steelworkers-building-pittsburgh-pa-usa). Emporis. Archived from [the original](https://www.emporis.com/buildings/121909/united-steelworkers-building-pittsburgh-pa-usa) on December 8, 2015. Retrieved April 22, 2021.

1. ["New IBM Building Unusual Inside, Too"](https://www.newspapers.com/clip/76268429/pittsburgh-post-gazette/). *Pittsburgh Post-Gazette*. January 11, 1964. Retrieved April 22, 2021. – via Newspapers.com.

1. Jensen, Edward (February 19, 1964). ["U.S. Steel Balks Over Name"](https://www.newspapers.com/clip/76529795/pittsburgh-post-gazette/). *Pittsburgh Post-Gazette*. Retrieved April 26, 2021. – via Newspapers.com.

1. Yates, Edward D. (January 4, 1962). ["Ghost of Wabash Empire Still Haunts"](https://www.newspapers.com/clip/76270197/pittsburgh-post-gazette/). *Pittsburgh Post-Gazette*. Retrieved April 22, 2021. – via Newspapers.com.

1. ["IBM Building, Manor Oak Sales Recorded Here"](https://www.newspapers.com/clip/76272580/the-pittsburgh-press/). *Pittsburgh Press*. April 15, 1973. Retrieved April 22, 2021. – via Newspapers.com.

1. ["USW Honors I.W. Abel"](https://www.newspapers.com/clip/76273961/pittsburgh-post-gazette/). *Pittsburgh Post-Gazette*. September 16, 1989. Retrieved April 22, 2021. – via Newspapers.com.

1. ["IBM's Building to Be Unique"](https://www.newspapers.com/clip/76260451/pittsburgh-post-gazette/). *Pittsburgh Post-Gazette*. April 28, 1962. Retrieved April 22, 2021. – via Newspapers.com.

1. Donnelly, Lu (17 July 2018). ["United Steelworkers Building (IBM Building)"](https://sah-archipedia.org/buildings/PA-01-AL5). *SAH Archipedia*. Society of Architectural Historians. Retrieved April 22, 2021.

1. *Building Structural Design Handbook*. New York: Wiley. 1987. p. 299. ISBN 9780471081500.

1. ["Ballet on Steel Draws Audience Below"](https://www.newspapers.com/clip/76260738/pittsburgh-post-gazette/). *Pittsburgh Post-Gazette*. August 15, 1962. Retrieved April 22, 2021. – via Newspapers.com.

1. Milana, Giulia; Gkoumas, Konstantinos; Bontempi, Franco (2014). ["Sustainability Concepts in the Design of High-Rise Buildings: The Case of Diagrid Systems"](https://books.google.com/books?id=j3yDBQAAQBAJ). *Proceedings of the Third International Workshop on Design in Civil and Environmental Engineering*. ISBN 9780989465830. Retrieved April 22, 2021.

1. ["IBM Building 'Due' Next April"](https://www.newspapers.com/clip/76260403/the-pittsburgh-press/). *Pittsburgh Press*. April 28, 1962. Retrieved April 22, 2021. – via Newspapers.com.

1. Robertson, Leslie E. (2008). ["A Life in Structural Engineering"](https://books.google.com/books?id=5gmPUXAqMFQC). *Seven Structural Engineers: The Felix Candela Lectures*. New York: Museum of Modern Art. pp. 67–68. ISBN 9780870707032. Retrieved April 22, 2021.

1. ["Paint Tells Kinds of Steel Used"](https://www.newspapers.com/clip/76266459/pittsburgh-post-gazette/). *Pittsburgh Post-Gazette*. October 8, 1962. Retrieved April 22, 2021. – via Newspapers.com.

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Adapted from the Wikipedia article [United Steelworkers Building](https://en.wikipedia.org/wiki/United_Steelworkers_Building) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/United_Steelworkers_Building?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.