When an industrial operation requires a new building, it’s time to evaluate the options. Will it be temporary or permanent? Build a pre-engineered box or get a custom shape and size? What building system is best?
Every case is different, and there are cases in which a certain type of building is a better option than the others. Tension fabric buildings are a versatile option for many industrial building situations, but metal and other types of fabric buildings have their own benefits as well.
To find out more about the technologies, engineering.com spoke with Legacy Building Solutions, a major vendor which offers a type of fabric structure that is different than the conventional membrane-covered hoop buildings many people are familiar with. Legacy buildings are made up of a structural steel frame with tensioned fabric panels for cladding. This system was developed and patented by Legacy to allow great design flexibility, customization, safety, and higher quality installation.
“We worked to take the best piece of the metal building industry, which is the rigid frame design, and the best piece of the fabric building industry, which was the fabric, and created a hybrid between those two unique building systems. We merged the best features together into one building system,” said Nathan Stobbe, general manager of Legacy.
In this article, we’ll take a look at the benefits and drawbacks of metal buildings, conventional fabric structures, and steel-framed tension fabric buildings.
What’s the Difference Between Steel-Framed Fabric Buildings and Other Types?
Tension fabric buildings use tension across the fabric to support loads. The tension on the fabric is critical – friction, including flapping in the wind or rubbing against supporting frames, will cause fabric cladding to depreciate and ultimately fail.
“Fabric performs well from a longevity standpoint when it's properly tensioned. When it's not properly tensioned, and is moving and flapping, that’s when it doesn't perform well,” cautioned Stobbe. A flapping fabric sheet can also cause difficulties during installation of the building. “If you're trying to pull a great big sheet over the top and suddenly a big wind comes up, that sail is big enough to power a large ship, so you can imagine what happens to the people trying to put up the panel.”
The difference between the conventional fabric hoop buildings often seen on farms and steel-framed tension fabric buildings is in how the fabric is attached to the frames. In hoop buildings, large sheets of fabric are attached to the end frames and rests on the center frames. The rigid framed buildings produced by Legacy use smaller fabric panels which are individually attached to each framing member.
Smaller pre-tensioned fabric panels, like what Legacy offers, work better than large membranes. The panels can be properly tensioned independently of one another. The strength of the structure comes from the frame, without relying on the fabric to keep the building upright. That’s what separates them from what we’ll call ‘conventional’ fabric structures.
Metal vs. Fabric Building Price
One of the most important considerations for customers looking for a new building is cost. While there are too many factors involved with custom buildings to give definitive numbers, industry experts say that traditional steel buildings can have escalated costs for high sidewalls. Fabric structures are cost-effective at any eave or peak height. Fabric buildings are typically installed in one third the time of conventional structures, providing a fast return on investment in relation to operations, down-time and other factors.
However, cost is never the only consideration. Below, we’ll examine the benefits and drawbacks of each option.
Metal Buildings
Metal buildings typically cover a steel frame with steel or aluminum sheathing panels. The steel structural members are strong enough to support payloads such as gantry systems or catwalks. The high strength of steel construction materials means the building is resistant to environmental and operational wear and tear.
Some steel building systems are designed to simplify construction and assembly. Pre-fabricated components such as sheathing panels or pre-engineered trusses have long been used to simplify construction. Panels are also easier to repair or replace than other forms of siding. Metal buildings are durable, and the metal materials can be recycled when the building is demolished.
One of the most significant benefits of metal buildings is that the structural frame allows for large clear-span widths. In some buildings, posts and trusses are an inconvenience. In other structures, they are a deal-breaker, such as in an aircraft hangar.
Now, let’s consider the drawbacks. Metal is susceptible to rust and corrosion, and while metal materials can be coated, painted or galvanized to reduce the effects of corrosion, these techniques aren’t perfect. Paint and coatings are subject to wear and tear. Galvanization works by chemically inhibiting corrosion’s attack on the underlying steel. In general, thicker materials with more mass perform much better in these conditions than thin-section materials such as siding, sheet or tube.
Water leaks are also a common drawback, risking damage to the contents stored within. In addition, metal buildings are costly and take longer to construct than fabric structures, both conventional and steel-framed.
Conventional Fabric Structures
Conventional fabric structures include hoop barns and other buildings which feature a large sheet of material pulled over a frame. These structures have the advantage of being less expensive than many other options. In addition, this type of fabric structure is typically temporary, and can be disassembled and moved.
Some types of conventional fabric structures use an arch-style frame which supports a wide clear span. However, the arch means that the ceiling is much lower near the sides. If you’re planning to maneuver equipment such as a boom forklift or loader inside, you may be looking for an option with accessible area near the sides.
One of the main advantages of all types of steel framed fabric structures compared to traditional fabric hoops is that the frame allows for soffit ventilation, which allows fresh air flow through the building. This can help save significant energy costs, and air circulation is especially beneficial for livestock, people or bulk goods stored inside. Good air circulation not only improves air quality, it can also prevent dust from settling on the interior surfaces of the structure. Notably, PVC and PE fabrics also resist corrosion. Legacy fabric buildings come standard with soffit and ridge ventilation to ensure proper ventilation within the structure.
Another significant benefit of fabric is in a fire emergency. Most fire damage is caused by intense heat and smoke. “Typically, the fabric is FR fire rated, but what happens in a fire event is the fabric will shrink away from the heat source and it will actually exhaust the heat and the smoke out of the building,” explained Stobbe. “So, because the smoke now has an escape route, it's much safer.” With the heat being able to exhaust, the extreme heat build up is typically avoided and often structural damage can be avoided as well.
The frame of a conventional fabric structure often consists of tube material, or truss systems. Tube makes for a lighter frame, but the thinner material makes it more vulnerable to corrosion and damage. According to Dwayne Moench, Legacy’s senior structural engineer, a solid steel beam construction is preferable: “With a rigid frame, the lateral stability of the frame is much greater, because the flange has a more substantial area, a more substantial mass, to keep it from kicking during compression, tension and reverse loading.”
How Fabric Buildings Leverage the Benefits of Both
In the industrial buildings market, many customers fall somewhere between the ideal use cases for both metal and fabric building types. For example, Solar Ship Inc., a Canadian aerospace company, required both the natural lighting of a fabric building and the clearspan space and customizability of a rigid-framed steel building.
Solar Ship wanted to build a large hangar to house their unique wing-shaped airships. The hangar had to be a permanent, enclosed structure with a large hangar door, and a wide clear span space. In addition, Solar Ship wanted the building to operate off the electric power grid. This meant the roof had to support solar panels, and the building had to be energy-efficient.
In Solar Ship’s case, a metal building would meet requirements for clear span, the large hangar door, and it would be a permanent structure. The metal frame could support the load of rooftop solar panels. However, metal buildings require more electric lights, and unless insulated, do not regulate heat well. On the other hand, certain types of traditional fabric structures would support the clear span, and a light-colored fabric material would allow natural light in during the day, reducing power costs. However, the load of solar panels and the large door may not be supported by the structural design of a non-rigid frame.
In the end, Solar Ship chose a permanent, rigid-frame fabric building. This type of building combines the rigid steel frame of a steel building with the benefits of fabric structures. Instead of a large sheet of material attached to the frame, these buildings use fabric attached to panels, which are then bolted to the frame. The panel design ensures that each section of fabric is properly tensioned, evenly distributing force across the frame.
In order to develop this new building, Legacy had to invent and patent the fabric attachment system which holds the fabric to the frame under biaxial tension. “The patented fabric attachment system ensures proper horizontal and vertical tension, which guarantees the long life of the fabric,” said Stobbe.
Moench elaborated on the process of developing their system. “Ben Fox, the President of the company, had things set up in the shop and outside, and we would run testing on it. We filmed the tests. He would try a certain way of attaching the fabric with the bolts that would hold it to the frame, and we'd run that. My role was to run calculations on this or that aspect of each design. When Ben got to the point where he was happy with the design, that's when he formalized it, and went for the patent.”
With the patent secured, the company was able to begin building around the country.
“That R&D is really what's driven the company from the very beginning, even as we were operating as a construction company,” said Stobbe. “It was those characteristics that allowed us to develop better installation methods, and work with manufacturers to develop better products. I can't think of a better way of doing it than how it actually occurred.”
To learn more about how Fabric Buildings address engineering challenges, check out the information on the Legacy Building Solutions website.
Legacy Building Solutions has sponsored this post. Opinions are mine. Isaac Maw