Overcoming fall protection challenges of pre-engineered metal buildings Fall Arrest Anchor Solutions


Fall protection on metal buildings roofs, especially pre-engineered metal build- ings, has always been a challenge. Although a cost-effective construction method, these build- ings are designed to close tolerances for loadings, and often don’t have the strength capacity required for traditional rooftop fall arrest anchors and the traditional fall arrest design process.


Traditional fall arrest anchors In most cases, traditional rooftop fall arrest anchors consist of a base plate, rigid pipe, and a D-ring or U-bar connection point at the top for attaching an energy-absorbing lanyard or self-retracting device. These anchors stand off the roof structure 9 to 14 inches, depending on the system design. OSHA requirements for anchor point strength state that the anchor must be able to resist a 5,000-pound load or have a factor of safety of at least two. Many designers not familiar with fall protection would opt for the 5,000-pound requirement to ensure they were covered from any liability. However, tradi- tional fall arrest anchors may not be a viable option for these buildings, as they develop a very high moment force on the supporting steel structure. As a result, fall arrest anchors are oftentimes


installed without consideration of the loads they can transfer to the roof structure in the event of a fall. What is also commonly encountered is the ab- sence of roof anchors being installed because the designer incorrectly believes the anchor connection to the structure must be rated to a load of 5,000 pounds applied 9 to 14 inches above the structure. Neither of these results is advisable. Designing to these requirements would undoubt-


edly increase the steel’s section size to a point where these buildings would no longer be very cost effec- tive. It could be imagined that the roof structure’s de- sign would be dictated more by the fall arrest loads, than the live and dead design loads for the building. Utilizing an engineering fi rm who are experts in fall protection would allow for much smaller design loads on the structure. They can specify the complete system and design to the actual loads that may be experienced, rather than the higher loads which were selected based on uncertainty of use, connecting means and system specifi cations. Roof penetrations created by traditional fall


arrest posts attached to the structure is another area of concern. If you have ever tried to chase down a water leak in a building, you understand why there would be apprehension with putting holes in a perfectly good roof. Generally, anchors


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are installed after a building is fi nished, which is another challenge altogether when trying to ensure a watertight building.


Better solutions Manufacturers of fall protection equipment have stepped up to the plate, and through innovative design and testing have engineered fall arrest solutions that effectively distribute loads and easily attach to the roof system. These fall arrest anchors distribute a smaller load throughout the roof system rather than excessive moment loads on specifi c sections of the roof structure. In some cases, they also eliminate any penetrations. This is accomplished, in part, by removing the moment load on the structure wherever possible. Some manufacturers have single-point an-


chors that stand proud of the roof and are similar in looks to a traditional fall arrest anchor. These anchors deform when exposed to a fall arrest force and distribute a much smaller shear load to the roof system, removing the much higher moment or torsional load from the design. These anchors have connections for standing seam roofs that eliminate any penetrations, and can be installed on corrugated roof systems with specialty screws that seal the holes and prevent moisture from being an issue. These anchor posts can also be used as part of a horizontal lifeline system for larger roofs that


By David Lough


require workers to have 3-D movement. Manufacturers have also developed low-profi le


rail systems that can be attached to the roof sys- tems of metal buildings. Attachment design is simi- lar to “tip-over” or deforming posts. These fall pro- tection systems can be attached to standing seam and corrugated roofi ng systems, as well. Because of the low profi le and the number of attachments, they reduce the load on the roof system and distribute that load over a greater area. Some manufacturers have incorporated these fall protection systems into ridge caps so that they’re not visibly obtrusive. Ad- ditionally, manufacturers may offer colors that blend into a roof, further masking the system. Although fall protection can be challenging


on metal building construction, many alternatives are available that do not necessarily result in an increase in the strength requirement of the building roof structure. These alternatives can be effectively and easily installed on new or existing structures. However, it is always recommended that this be done under the supervision of a qualifi ed person, preferably a professional engineer that specializes in fall protection system design.


David Lough is general manager of Poulsbo, Wash.-based Gravitec Systems Inc. For more information, visit www.gravitec.com or call (800) 755-8455, ext. 236.


This illustrates force absorption using a constant force post. (Images courtesy of Latchways LLC)


This demonstrates traditional fall protection anchor failure from equivalent force. (Images courtesy of Latchways LLC)


December 2013 METAL CONSTRUCTION NEWS 37


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