A BY SYLVIE BOULANGER, PH.D., P.ENG., AND TERRI MEYER BOAKE, LEED AP ARCHITECTURALLY EXPOSED STRUCTURAL STEEL (AESS) is a mix of art, science and know-how, introducing the issue of per- sonal preference for what is considered aesthetically pleasing while remaining technically sound. Whether your AESS project is the canopy of a retail store, the atrium in an ofice building, the passenger area of an airport, or the long-span roof structure of a sports complex, three key factors should be addressed to ensure a successful outcome: ➤฀Good Communication ➤฀Elegant Connections ➤฀Reasonable Cost Engineers strive to design structures in which loads low efi- ciently to the ground. The loads are happy. The building is stable and durable. End of story. Creating an aesthetically pleasing structure is not part of the curriculum, let alone conceiving elegance in the design of connections. Yet, with AESS, structural engineers become part of a triangle of communication with the architect and the fabri- cator, which greatly affects connections, their design and cost. This interactive design process is very different from the more linear pro- cess associated with “standard” structural steel that is hidden from view and where the architect steps back from involvement in the process. When AESS is used, the architect sees the exposed connec- tions as part of the design expression of the project. Adapting to the new requirements in the design of AESS is really not that dificult. In this article, we propose 17 tips that we hope will make your involvement with AESS a fulilling experience. Communication A fabricator once explained that an architect speciied “nice-looking” connections with a “smooth” inish for the exposed part of a school. As one can imagine, such vague language caused anguish for the poor engineer who was somewhat caught between two world views. “Nice-looking” connection and “smooth” inish mean some- thing quite different to the architect, engineer and fabricator. Communication must be structured to provide a clear set of guide- lines for the vision of the outcome of the AESS project. Consider the following tips to improve communication right from the speciication. 1. Have an AESS section in your speciication, preferably as a subdivision of the Structural Steel Division. The AESS sec- tion will provide separate requirements for the exposed steel from what is normally included for concealed structural steel. However, all the standard structural steel requirements apply. 2. Adopt a category approach. A four-category system (AESS1 through AESS4) such as proposed in the article “A Categorical Approach” (April 2008 MSC, available at www.modernsteel.com/ backissues) and now part of the CISC Guide for Specifying Architectur- ally Exposed Structural Steel (available at www.cisc-icca.ca/aess) can help clarify requirements for differentiating AESS as a function of the building type, distance of view, surface treatment and budget. Another useful set of characteristics was proposed in the AISC AESS supplement published in the May 2003 issue of MSC, which is also available online. 3. Moderate discussions with the architect and the fabrica- tor in the early stages. It is essential to have face-to-face meetings with the architect, engineer and fabricator to discuss expectations of the form, it and inish of the steel. Depending on the work, it may be desirable to meet at the fabrication shop or in front of AESS that has previously been completed by the fabricator. 4. Be clear in your speciication about what you will accept as a substitution. Once the loads are happy, limits need to be 22 MODERN STEEL CONSTRUCTION DECEMBER 2011 Left: An example of a helical weld on a large tubular member. Was this part of the specification? Above right: There is a sense of balance and attention to detail on this relatively complex connection. The detailer definitely added his magic touch. Below right: A simple taper on the flanges and lightly rounded corners on the shear tab go a long way to add elegance to this repetitious detail in an airport. The Three C’s of AESS Following these 17 tips will help engineers experience architecturally exposed structural steel as a pleasant interactive process— not just a challenge. ➤ ➤ ➤ Photos in this article have been provided by the authors.