C+S October 2022 Vol. 8 Issue 10 (web)

The primary benefits of tension fabric buildings have been clear for decades: Fabric cladding doesn’t corrode, making it a great option for high-humidity facilities or corrosive material storage. In many applications, the clad- ding also allows for natural daylighting. The structures are cost-effective, and they go up fast. Some of the downfalls have also been obvious: For a long time, buildings were only offered in pre-engineered designs with standard sizes to pick from. And depending on the manufacturer and materials used, longevity wasn’t always what was hoped for. Proving It with Fabric Using proven I-beam designs, fabric buildings can be fully optimized for any facility application By Eric Donnay

using metal building software programs, there is virtually no additional lead time involved to render a complete building frame. Some manufacturers, including Legacy, have gone a step further and handle their own in-house steel fabrication. By not outsourcing this key component of a fabric building, these companies are better posi- tioned to ensure quality control, adapt to any project modifications, and eventually provide on-time delivery of the structure. Codes and User Demands The precise dimensions made possible by the rigid-frame concept make it far easier to meet code requirements while also optimizing the building design, helping to achieve all necessary considerations without investing in excess materials. For example, tension fabric structures are among the most common and cost-effective shelter choices for aircraft hangars. The code re- quirements in the aviation industry are very strict, necessitating that there is always enough vertical and horizontal clearance around the wingtips of the aircraft in relation to the roof, door frames, or sidewalls of the building. In the days of standard size fabric buildings, meeting these clearances mostly involved the manufacturer just taking the aircraft measurements and offering the smallest pre-engineered structure in their inventory that could achieve compliance. In other words, if a width of 85 feet was needed, a supplier would have to go to a 100-foot-wide option since their 80-foot offering wouldn’t suffice, which added 15 more feet than needed to the project footprint. Using rigid-frame design, engineers can provide the most optimal dimensions and avoid wasting money or space that might be needed for future considerations. Dimensions, however, are far from the only parameter that can be optimized in a fabric building.

In recent years, however, leading manufacturers have made strides to eliminate the historic weaknesses of fabric structures, while main- taining and even enhancing their strengths. Better engineering has helped solidify fabric’s place as an ideal facility solution in a wide range of industries. Rigid Frame Fabric structure projects have a long history of short lead times. For decades, the main reason for this was that these buildings mainly only came in standard size offerings, meaning that very little thought had to go into the design. Typically, a pre-engineered size was selected “off the shelf,” and the structure was quickly installed in a matter of weeks or months. The ability to provide fast turnaround with a tension fabric building hasn’t changed, but the way these structures are built has evolved for the better. The traditional fabric structure consisted of a hollow-tube, open web truss frame covered with a fabric roof. The problem was that there were far too many engineering assumptions being made when designing and assessing the integrity of a web truss frame. Disagree- ment from one engineer to the next was commonplace. The logical solution over the past decade was to move away from de- sign subjectivity and toward framing that was universally accepted and understood by everyone in the engineering community. Web trusses began to be pushed aside in favor of a rigid-frame design using struc- tural steel I-beams. Legacy Building Solutions was the first company to marry together an I-beam frame with a tension fabric membrane. In addition to being a proven method, rigid-frame engineering instantly made it possible to move beyond standard sizes and instead design every building to the exact dimensions desired. The increased strength of the frame allows for buildings to be made much taller and wider than before as well, making it perfect when long, clear spans without support beams are needed. Furthermore, because full designs are done

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October 2022 csengineermag.com

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