TEXTILES.ORG
Proper engineering trumps attempts to save money and time.
by Janice Kleinschmidt
Last May, consulting engineer Nicholas Goldsmith received a call for help with a tent for the July 4 Coney Island Festival and Flea Market.
“A client who purchased a rental tent system from China set it up not realizing that the engineering used in China really wouldn’t apply to New York,” says the senior principal of FTL Design Engineering Studio in New York City. “After he set it up, the building department said he needed a local engineer to stamp the project. He brought us in, and we had to then do forensic engineering. We had to measure all the pieces. There were no drawings.” Fortunately, FTL was able to have necessary steel reinforcements made, shipped and installed by the end of June.
“The cost was a lot more than if [the client] had just come to an engineer at the beginning and had them review products out there to select something that would meet the wind load,” Goldsmith says.
As evidenced by the Coney Island incident, tent buyers need to pay particular attention to engineering specifications before ordering a foreign product.
“There aren’t as many restrictions [in China] as there are in many parts of the world, so the chance you might get something that might not meet U.S. standards is certainly there,” says Pat Moughan, general manager of Losberger U.S. in Frederick, Md. “If something is too cheap to be true, there’s got to be a reason why.”
Losberger manufactures tents (all are engineered) in Bad Rappenau, Germany, to the German Institute for Standardization’s DIN standards (similar to ISO standards). “We have our engineering books,” Moughan says. “I have a U.S. engineer translate them into applicable U.S. building codes or, in most cases, international building codes.”
Comparison shopping
Even though Losberger also manufactures tents in China to support its Asian market, the company ships some materials from Europe to its Chinese factory. “There are some products not readily available [there], not up to the standard of our engineering,” Moughan says. He advises tent buyers to do their homework.
“Does the manufacturer have a history? Have they been around for [only] five years because they thought it would be a good idea to be in the tent business? I think track record is important. If there is a problem, who are [buyers] going to call? Who is their resource? The materials are pretty simple. You should be able to ask what grade bolt is being used, the grade of the steel. Ask as many questions as possible.”
Brian Rieke, an owner of Stamford Tent & Event Services and the company’s director of operations, waves a warning flag over manufacturers that offer a product that is the same as—or which they claim is the same as—an existing product at a fraction of the cost. He notes that his tent rental company, based in Stamford, Conn., has received numerous emails from a seller of Chinese-sourced tents offering a product they say is compatible with the tents they buy from Losberger for significantly less.
But Rieke questions, “How do they know it is compatible? Where is the engineering that comes along with it? Why is it so much less expensive, and why all of the sudden did they just come out of nowhere to create this product?” Even if a product were compatible, interchanging parts with existing tents, he notes, would void any engineering guarantee from the other company.
Stamford, says Rieke, considers cost “later on in the process.”
“When you look at comparable specifications from one brand to the next, it is the details that always seem to stand out from one product to another. We have a history of migrating to the one that is more refined, because it says something about that company, as well as us.”
Lightweight structures
When it comes to fabric structures, a lot of engineering gets done through contractors, says Craig Huntington, president of Huntington Design Associates Inc. of Oakland, Calif. “In all but the simplest structures with uncurved fabric, you need a fabric specialist engineer,” he says. “Usual construction materials—wood, steel and concrete—are very adaptable in how they carry load. Fabric, string, cable—all you can do is pull on it. All it resists is tension. Because of that, the way the shapes are derived is very different.”
“Fabric structures are very particular. The programs that are used for doing engineering analysis are written for this industry and are fairly unique,” Goldsmith says. “I have been in situations where a client has had other engineers aboard and then realized [the engineers] don’t understand the tent structure, and then we are called in to do it.”
Temporary structures
“A lot of companies put up tents although they don’t do the research involved to make sure they are secured properly,” Rieke says. “Manufacturers will give you specifications to stake or ballast properly. When dealing with engineered tents, you know exactly what those requirements are for each location because they have calculated uplift, down pressure and wind load.”
To Rieke’s way of thinking, engineered tents’ only disadvantage is that end users may think they can do things they are not designed to do. “We don’t have an issue with the cost or amount of time needed for installation,” he says, mentioning the factors others refer to as disadvantages. “It’s all about the safety of the people in the tent.”
“If you don’t have any engineering, building officials won’t let you put tents up,” Moughan says. “It’s become more and more important to have engineered tents, even 20-by-20s.”
According to Moughan, tent manufacturers and renters can expect that trend to continue. “Non-engineered tents will become a thing of the past,” he predicts. “They’ll be less and less acceptable in any public event.”
Occasionally, Mother Nature ignores her own rules and blows down a tent designed, tested and installed to meet wind-force specifications. But, as Rieke points out, “If tents were not engineered, the failure rate would be much, much higher.”