Published: February 28, 2008
Birdair, Inc., the leading full service design build specialty contractor for lightweight tensile architectural projects throughout the world, delivers custom tensile roof structures capable of resisting severe subtropical weather conditions, including hurricanes. >
Birdair structures – designed for traditional building envelopes as well as freestanding applications – are engineered to meet the most demanding building codes and standards in subtropical regions such as Florida, Puerto Rico and the Caribbean. This includes the Miami-Dade County Building Code Compliance Office’s requirements for ‘Missile Impact Testing’, in addition to other tests designed to measure wind resistance.
In order to meet the Miami-Dade County Building Code for missile impact resistance, materials used in building structures must be subject to unique tests. To pass this stringent standard, a nine-pound wooden 2×4 is loaded into a CO2-powered cannon and fired multiple times at a tensioned fabric test panel. The 2 x 4 reaches a velocity of 50 feet per second, impacting Birdair’s fabric panels at speeds up to 140 mph. Pea gravel (representing small missiles such as roof ballast blown off of conventional roofs) is also fired at the membrane panels. If little or no perforation or tearing of the material is visible after the tests, the membrane receives a passing grade.
Birdair structures were put to the test when Hurricane Wilma roared across the Florida coast in October 2005, causing widespread damage. The Port of Miami Terminals F and G for cruise ships, completed in 1999 using PTFE coated fiberglass membrane, suffered insignificant damage, proving the durability of the material.
“Only one fabric panel was damaged during that storm,” says Dave Ricci, Birdair Service and Support Director. “It turned out to be from a piece of flying sheet metal and other objects. Otherwise, the structure survived the storm in very good shape.”
Florida Hospital Waterman, located northwest of Orlando, found itself in a similar situation in 2004 when the area was slammed with four hurricanes, including Hurricane Charley, with 140-mph winds. One year earlier, Birdair had installed roof and canopy structures on-site to cover the hospital’s main entrance, emergency entrance and two-story central lobby.
The building’s survival was due in large part to Birdair’s engineering of the hospital’s canopy structure, which included the attachment of an intricate hardware system used to sectionalize and shape the fabric panels.
“When designing in hurricane prone areas, the challenge is simple – deal with an excessive amount of wind speed”, says Joe Magiera, Birdair’s National Sales Manager. “The wind issue isn’t different when considering other building materials; they all must be engineered to meet the codes. The message is that fabric is a viable material that has been tested and successfully used in hurricane prone areas.”
For all projects, the tensile structure’s design is analyzed under computer modeling to accurately determine the behavior of the structure when it is subject to the live loads (snow and wind). For the elongated walkway canopy built on San Juan’s Pier III in 2006, tie-down cables were required to reduce flutter in the 900 feet of PTFE-coated fiberglass membrane in winds greater than 125 mph. This design highlights the capabilities of tensile fabric shapes under extreme stress.
A wind tunnel study was conducted to better understand behavior under extreme wind pressure that could occur to this canopy. The potential for flutter was reduced by pre-stressing the fabric and limiting the size of the panels by introducing intermediate cables. “Based on our tests, any damage incurred should be minor and easily repairable,” says Tian-Fang Jing, a design consultant with New York-based Weidlinger Associates, Inc., who collaborated with Birdair on the project.
“The stability and exceptional durability of Birdair structures is clearly seen through their performance in the face of a hurricane,” explains Kevin Mayer, vice president of business development, marketing and sales. “Birdair gives clients a tested, proven, out-of-the-box system for achieving the building structures they design, no matter what the weather may bring.”
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About Birdair: Birdair, Inc. is the leading specialty contractor of custom tensile structures throughout the world. In addition to pre-construction services such as design assistance, budgeting, construction methodologies and project scheduling, Birdair provides design-build solutions in all aspects of project design, engineering, installation and maintenance. The company offers a selection of architectural fabric membranes, including PTFE fiberglass, ETFE film, PVC and Tensotherm™. Birdair, based in Buffalo, NY, is a member of the Taiyo Kogyo Group, with operations serving North and South America and other international locations. For more information about Birdair, like us on Facebook, call 1-800-622-2246 or visit www.birdair.com.