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Manufacturers use several different frame types to construct tension fabric buildings. At first glance, these frameworks may look similar, however, there are key differences of each that is critical to be informed about before investing in a tension fabric building. While some build using rigid steel frames, single tubes, or bent web trusses, the superior choice by many has historically been open web trusses. See here an overview of each, and how they compare to open web trusses.

Rigid Steel Frames or i-Beams: No Real Advantage

Some fabric structure companies choose to design their steel framework using rigid steel frames or i-beams. Industry studies have claimed that this does not guarantee a “better” build, but can cost more than an open web truss design for the same structural integrity.

With more steel mass in a rigid steel frame, the natural light from the fabric membrane is diminished and tends to create a shadowed interior, thus, may require a need for artificial lighting. This can impact desired savings on utility costs, long-term.

Aesthetically, some may also find the rigid frame look ‘chunky’ and unappealing.

Conversely, open web trusses allow for maximum use of clearspan space. Any ventilation options, HVAC, and electrical applications are more easily installed and accessible with an open web truss making installation and maintenance faster and possibly even less expensive.

Single Tube Frames or Base Rails: Limited Size and Design Capability

Single tube frames are often found in smaller, less complex tension fabric buildings. This type of framing system limits how tall and wide a fabric structure can be, and can lack the proportionally spaced load-bearing posts of an open web design. Fabric buildings made with single tube frames are often an “out of the box” option and do not allow customization or durability. These structures may be quick to obtain and set-up, but the trade-off is less durability and virtually no customization options.

Conversely, open web trusses allow the flexibility to construct fabric building widths that range from 22′ wide to 250′ wide or more, with the durability and reliability required for a structure that will last generations.

Bent Web Trusses: Not Fully Protected

While a bent web truss may be faster to fabricate and will sometimes cost less, they tend to prevent proper interior application of the protective hot dip galvantization coating at critical truss connection points. These unprotected points in the steel assembly may eventually rust and weaken the entire system – making it prone to buckling failure.

The bent web design is not conducive to establishing an effective weld. The pinched end of the web leaves very minimal room for the hot-dip galvanization to coat the area, leaving untreated steel in a critical connection point in a highly corrosive environment. Therefore, does not allow for full coverage of hot-dip galvanization.

Conversely, an open web truss design allows for optimal coverage during the hot-dip galvanizing process, particularly if designed with square tubing versus round tubing. It may seem like a minor detail, but square tubing used in open web trusses is far superior to round-shaped tubing as it resists any bending and buckling due to having more metal stock than a round tube.

Tension Fabric Buildings from Calhoun Super Structure

Calhoun Super Structure exclusively uses an open web truss framework with square tubing. Our truss system gives the frames a wider stance and a more robust connection into the chord – a more effective way of transferring the load between the chords and the web.

We build to real-world specifications, using 3D finite element analysis to simulate live and dead loads. This analysis can also help determine the size of truss members, along with the spacing and slope. Calhoun offers total customization using the industry’s best construction methods for tension fabric buildings.


For more information on open web trusses, read our Open Web Truss Fact Sheet here.