Wind and Metal Buildings

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All locales are subject to damaging winds, even if not residing in “Tornado Alley” or in areas where hurricanes are common. Therefore, it is required that structures meet building code requirements for minimum resistance to such destructive winds. The formulae for such codes are based on historical meteorological data and takes into consideration extreme “3 second bursts” of reasonably expected maximum wind speed for a given area. In addition, the immediate terrain and environment are factored in to determine their effects on the given wind. Surrounding buildings, trees, hills, mountains, and the like, can serve to deflect or sometimes, enhance wind speed, its direction, and thus its impact on the structure. The end result is a code that determines, at minimum, the maximum wind speed that the building must be built to withstand (i.e.; 85mph) and the exposure level it must be built to (i.e.; EXP C).

For most locations, meeting the building requirements for wind is simple. However, in the many places subject to gusting winds or frequent wind events, the challenge to construct a metal building that meets code can prove difficult. At Tech-Fast, we are accustomed to such challenges. We have built numerous structures to meet demanding building codes including several in extraordinary windy locations. We accomplish this by first understanding how wind affects metal buildings.

There are a number of ways in which wind forces can hurt a steel structure. Slipping of the structure is one method, where the pre-engineered steel building actually exists as a whole element, but due to frailty of attachment to the structure’s foundation, caused by high wind forces, slides laterally off of its footing. Capsizing of the steel building is another effect of wind damage. This, said a different way, is the frailty of building binding to its foundation as an effect of insufficient weight load plus harsh wind events that concludes in the rolling over of the structure as one unit. Not as common, but nonetheless incredible to witness, is the complete collapse of the structure. This is the defeat of the building due to extreme wind events that induce the steel structure to fall apart upon itself, like a house of cards toppling. Most commonly, however, damaging winds will cause only a portion of the pre-engineered steel building to collapse or fall, but when this occurs, damage to adjacent components of the building can develop. Sectors of walls ripped out, doors blown inward, and/or fragmentary roof collapse are all results of what can eventuate.

High wind damage analysis shows that the structural failure of rooftops and wall supports most often occurs at the eaves and the four corners of a metal building. A great deal more engineering focus, therefore, should be placed on the design of this portion of prospective steel structures so as to lessen the chance of their demise in the face of strong winds. Extra reinforcing should be centered on these areas through a “salient corner” approach that centers on “problem areas” requiring strong wind structure loading.

Tech-Fast has designed buildings subject to the probability of high winds, by using extra roof clips, increasing the purlin size from the standard 4 inches to the stronger 6 inches, increasing their numbers by placing them 2 ½ feet on center as opposed to 5 feet on center, and crimping the roof seam, thus providing additional strength and opposition to damaging winds. Walls can be strengthened by increasing the thickness of the metal, using additional framing, and combining (or substituting) with concrete block where necessary. Further, it is equally important to consider the man and roll-up doors to be used in such buildings. Doors stamped and certified to meet required wind loads are very important as the failure of these can lead to upward force winds that can wreck havoc on the interior support of the building.

The affect of wind, is just another subject that must be considered when designing a well built metal building, just as one must consider soil, drainage, use, snow loads, and a myriad of other things. Uniform building codes were created to address these issues and provide standards for engineers to adhere to. Using a professional firm like Tech-Fast, ensures that such issues, even when challenging, are but minor road blocks in the design and build highway.