BLOG 14 AESS - 4

 

AESS - Architecturally exposed steel certainly differs from standard structural steel. AESS is divided into five categories based on various factors. Steel members of similar qualities are also categorised under different AESS, due to the nature, scale of the project or even where the steel member is used. 

Such a category is AESS 4, which is labelled for steel members employed as showcase members in a structure or a building.

The factors to be considered to identify the level of AESS for a project are    
•    Member Visibility


As the name says, the visibility of the steel member lays the conditions for the finishes and detailing. The design time and efforts are put for the member/ part of the member that is visible or exposed for the view. Identifying such specific locations will take analysis and careful consideration. In AESS 4 the weld seams must no longer be visible.


•        Viewing Distance

Any object 20ft far from the human eye can be devoid of clarity in its details. The treatment given to the steel member is decided by the viewing distance. 





•        Location

There are cases where welds may show through the back face of an exposed steel element. Locations, where welds show through to the other side of the AESS component, must be addressed to reduce their undesirable appearance.


•        Lighting

According to Steve Weiss, principal and founder of Weiss Architects, Lighting has the greatest impact on interior AESS, whereas sight lines are the most important for AESS located on the exterior. Lighting fixtures are predominantly planned and laid as per the aesthetic needs. For a dramatic effect, when lights are directed upon high ceilings which would normally not be visible to the naked eye, they tend to expose the texture and blemishes on the surface. 


•        Coatings, Finishes & Appearance

Filling any deviations with a body filler as well as sanding textured surfaces are methods of fabrication used in this category. AESS 4 elements have a higher premium not only for its glove-smooth finish but more for its complexity in structural geometry. The appearance of the weld should be smooth and contoured. Open holes placed in the steel members, often for the welding process, are to be closed off and smoothed out for a clean, finished surface.


-        Joinery welded connections are preferred and focused more than on bolted connections for a seamless aesthetic.

- When selecting the level of finish of a welded connection, the viewing distance especially for AESS 4 must be respected.




•        Style

The sculptural nature of steel is meant to be the main focus when specifying AESS 4. The contoured connections make the whole structure seem as a single entity. 


•        Adjacency


Tolerances of fabricated forms are more stringent – generally half of the standard tolerance.



Installation, Fabrication & Costing 

Most elements and members are custom cut and fabricated due to their unique style and differing geometry which depends on the desired aesthetic besides the structural loads. Due to fabrication and the type of finish rendered for AESS 4, it significantly has higher total costs.

AESS 4 is preferably painted in the shop to achieve the desired quality of the finish. The protection of these members during transportation and installation is critical due to the need to prevent undue damage to the finishes.



The design approach is to be discussed before selecting the AESS category. AESS 4 requires stringent conditions are specified and followed. Estimating the outcome precisely and selecting the proper connection, coating and finishes can significantly affect the costs and final result 


-Janani Venkateswaran


No. of Words - 780


REFERENCE

  • https://continuingeducation.bnpmedia.com/courses/american-institute-of-steel-construction/categorized-by-design-architecturally-exposed-structural-steel/2/
  • https://www.tboake.com/SSEF1/aess4.shtml
  • https://www.steel.org.au/resources/elibrary/resource-items/code-of-practice-for-fabricators-architecturally/download-pdf.pdf/
  • https://www.aisc.org/globalassets/aisc/aess/all_about_aess_reprint.pdf
  • https://www.aisc.org/why-steel/architecturally-exposed-structural-steel/#29207


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