Why Steel

Architecturally Exposed Structural Steel

When left exposed, structural steel can express form, integrity and beauty in buildings while simultaneously demonstrating function and strength.

Architecturally exposed structural steel (AESS) can express the structural integrity of a building in a striking way and put the structural system at the aesthetic forefront. Today, many buildings showcase AESS to provide an identity and even create iconic structures. AESS elements feature higher degree of finish and are handled with a higher level of  care during fabrication and erection. Beautiful and creative expression can be achieved in the broad range of shapes, tapered forms, curves, colors, glossy or matte finishes, as well as seamless or tectonic expression.


Following are a handful of projects that illustrate the beauty and expressiveness of AESS:

Lee Hall III

Lee Hall III, Clemson University, Clemson, South Carolina. 

Photo courtesy of Skidmore, Owings &  Merrill LLP.  Credit: © Scott Frances | OTTO


Lee Hall III at Clemson University in Clemson, S.C., incorporates AESS as an educational tool to elegantly express buildings' steel structural system. Slender "tree columns" draw attention to the exterior, acting as feature elements that create an identity with purpose. This addition to the College of Architecture, Arts and Humanities is a display of clarity between architecture and engineering, as well as an expression of fine craftsmanship. 

Photo courtesy of Skidmore, Owings &  Merrill LLP. Photo credit: © Scott Frances | OTTO

Non AESS Steel

A steel beam, recently cut to size and with the ends coped per the standard requirements of the AISC Code of Standard Practice. Note that the edges have not been ground smooth; etched numbers and heat marks are visible from the fabrication process. This member is not specified to meet AISC AESS requirements.


Pomona College Studio Art Hall

The Pomona College Studio Art Hall in Claremont, Calif., exposes the steel roof structure as an aesthetic feature that's visible from below. The height of the steel diagrid is well over 20 ft from the typical viewing distance on the ground. .  

2015 IDEAS2 Award Winner
Photo credit: Jeremy Bitterman, courtesy of wHY Architecture

Brookfield Place Entry Pavilion

AESS trees define the Brookfield Place Entry Pavilion in New York.  Uplighting the structural elements creates a dramatic effect but also highlights the importance of the surface finish. Welds were ground smooth and made flush with the steel’s surface for a cleaner aesthetic. Additionally, fitting multiple steel members  together necessitated stringent erection tolerances for the trees.  

2014 AISC IDEAS2 Award Winner
Photo credit: Bess Adler/courtesy of Thornton Tomasetti 

Intumescent Coating

An intumescent-coated and painted connection detail at Michigan State University’s Wells Hall Addition in East Lansing, Mich. 

Photo credit: Paul Dannels/courtesy of SDI Structures

AESS emphasizing bolts and connections

A more tectonic style of AESS assembly, emphasizing bolts and connections.  

Photo courtesy of Walter P. Moore  Credit: Brian Wancho

AESS emphasizing smooth connections

The intersection of multiple AESS members at  Loyola University’s Institute of Environmental Sustainability in Chicago is seamless and smooth.

  Photo courtesy of © Skidmore, Owings & Merrill LLP

Twisting AESS

837 W Washington in New York was challenged with tight tolerances and straightness requirements so that all steel members would precisely align in this visibly twisting form. The exoskeleton structure is exposed to the exterior and requires additional applied treatment to prevent corrosion.  

Photo courtesy of Gilsanz Murray Steficek

University of Michigan

Robert B. Aikens Commons at the University of Michigan in Ann Arbor, Mich.

Photo courtesy of SDI Structures 

Etching on Non AESS Steel

Numbers are etched into a steel beam (left) during the fabrication process. After receiving a painted finish coat in the shop, the tracking number for the project can still be seen. 

Photo courtesy AISC

Mill Marks

Mill marks from Steel Dynamics, Inc. (SDI) are visible through the painted finish on this structural member.

Photo courtesy of AISC

Boston Logan International Airport

A series of intersecting hollow steel sections (HSS) are visible along the pedestrian bridge (left) at Boston Logan International Airport. A close-up view (right) shows the weld seams, which have been ground out consistently at each architecturally exposed member and coated with intumescent paint. 

Photo courtesy of AISC 

Queen Richmond Centre West

Steel castings typically do not fall under AESS requirements per AISC’s Code of Standard Practice.
Photo credit: doublespace photography/ courtesy of CastConnex

Chicago O’Hare International Airport

Daylight penetrates the interior of the United Airlines Terminal (Terminal 1) at O’Hare International Airport in Chicago.

Photo courtesy of AISC

Sacramento International Airport

The Central Terminal and Concourse B Expansion at Sacramento International Airport.

Photo credit: Tim Griffith  

United Therapeutics Pedestrian Connector

United Therapeutics Pedestrian Connector

2014 IDEAS2 Award Winner
Photo credit: © Ron Blunt

Anaheim Regional Transportation Intermodal Center

Anaheim Regional Transportation Intermodal Center - Phase 1

2015 IDEAS2 Award Winner
Image courtesy of Thornton Tomasetti

Florida Polytechnic University

Florida Polytechnic University

2015 IDEAS2 Award Winner
Photo credit: Macbeth Photo

Denver Union Station

Denver Union Station

2015 IDEAS2 Award Winner
Photo credit: Ryan Dravitz Photography

The Gourd

The Gourd

2016 IDEAS2 Awards Winner
Photo credit: Scott Adams

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