When members are specifically designated as architecturally exposed structural steel or AESS in the contract documents, the requirements in Sections 1 through 9 shall apply as modified in Section 10. Surfaces exposed to view of AESS members and components shall be fabricated and erected with the care and dimensional tolerances that are stipulated in Sections 10.2 through 10.6.
Commentary
The designation of steel as AESS adds cost, and that cost is higher as the level of the AESS designation increases. However, not all exposed steel must be designated as AESS. There are many applications in which the as-produced appearance of fabricated and erected structural steel may be deemed sufficient without any special additional work.
10.1.1
The following categories shall be used when referring to AESS:
- AESS 1: Basic elements
- AE5S 2: Feature elements viewed at a distance greater than 20 ft (6 m)
- AE5S 3: Feature elements viewed at a distance less than 20 ft (6 m)
- AE5S 4: Showcase elements with special surface and edge treatment beyond fabrication
- AE55 C: Custom elements with characteristics described in the contract documents
Commentary
The categories are listed in the AESS matrix shown in Table 10.1. Each category describes characteristics with successively more detailed—and costly— requirements.
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• Basic elements in AESS 1 are those that have workmanship requirements that exceed what would be done in non-AESS construction.
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Feature elements in AESS 2 and 3 exceed the basic requirements, but the intent is to allow the viewer to see the art of metalworking. AESS 2 is achieved primarily through geometry without finish work and treats things that can be seen at a larger viewing distance, like enhanced treatment of bolts, welds, connection and fabrication details, and tolerances for gaps, copes, and similar details. AESS 3 is achieved through geometry and basic finish work and treats things that can be seen at a closer viewing distance or are subject to touch by the viewer, with welds that are generally smooth but visible. AESS 3 involves the use of a mock-up and acceptance is based upon the approved conditions of the mock-up.
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• Showcase elements in AESS 4 are those for which the designer intends that the form is the only feature showing in an element. All welds are ground and filled, edges are ground square and true. All surfaces are filled and sanded to a smoothness that doesn't catch on a cloth or glove. Tolerances of fabricated forms are more stringent—generally half of standard tolerance. AESS 4 involves the use of a mock-up and acceptance is based upon the approved conditions of the mock-up.
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• Custom elements in AESS C are those with other requirements defined in the contract documents, which may be more or less stringent than the other categories because individual desired characteristics may be required at the discretion of the specifier.
10.1.2
A mock-up shall be required for AESS 3 and 4. If a mock-up is to be used in other AESS categories, it shall be specified in the contract documents. When required, the nature and extent of the mock-up shall be specified in the contract documents. Alternatively, when a mock-up is not practical, the first piece of an element or connection can be used to determine acceptability.
Commentary
Generally, a mock-up is produced and approved in the shop and subsequently placed in the field. The acceptability of the mock-up can be affected by many factors, including distance of view, lighting, and finishing. The expectations for the location and conditions of the mock-up at time of approval should be defined in the contract documents.