Fall Protection Anchor Mounted to Standing Seam Metal Roofing

[shemp]

I am a structural engineer designing a government project that requires roof mounted fall protection. The type of anchor being considered is shown in the following link. It mounts with set screws to the seams of a standing seam metal roof.

https://www.guardianfall.com/performance-safety-products/anchor-points/product/spanner-anchor

As the EOR I have major concerns with the use of this product. The anchor itself may be capable of resisting the 5,000 lb load, but how does that load get transferred from the standing seam roofing down through ~5" of rigid insulation and into the metal deck and steel roof beams? Standing seam roofing is typically connected with one screw every two feet or so. I don't see how these anchors can be clamped anywhere on a roof with the assumption that the loads from the fall arrest will be safely resisted by the structure. The fine print of the technical data sheets say that the "structure must withstand loads applied in the directions permitted by the system of at least 5,000 lbs." When I asked a major supplier how this force is typically resolved, they responded as if they have never heard such a question.

Does anyone have experience in specifying and designing for this type of standing seam roof mounted fall protection anchor?

Thanks

 

[CANPRO]

I've seen these systems as well and have had the same concerns. I think their largest market are people who don't read the fine print.

This is one of those situations where crunching the numbers on paper doesn't translate well to reality. You'll probably never get this to work for 5000lbs on paper, but if someone falls (and I'm sure this has happened already with their product) the system is more than likely to be okay.

I know that doesn't really help you much. I think the only way to conclusively say that product works with your roof system is to test it on a mock-up.

 

[Agent666]

My experience with this type is that they are essentially tested, so provided they are installed correctly they works as advertised. What they don't advertise is they work through adsorbed the energy through considerable roof deformation. So if there is a fall you will potentially be up for replacement of roofing, purlins, etc and anything else that gets damaged along the way resisting the load.

I looked at using them in the past but instead provided another dedicated system of posts connected directly to the primary structure with attachment points, primarily because of the fact it would render the building envelope useless, and secondly the dodgy way it relied on cladding (which might have a life much lower than typical of 50 year building design life).

Salesperson wasn't to worried about the damage, everyone else was. When asked for evidence from testing about the damage expected (photos, etc) they were unable/unwilling to provide information.

 

[XR250]

I imagine the roof panel will rust at the set screw locations which may cause even more questionable capacity down the road.

 

[Nor Cal SE]

The other posters make good points, and I think a good initial course of action is to notify your client right away that you expect significant roofing damage in the event of any fall. This might make them think twice, and potentially elect a more secure system such as Agent666 describes.

 

[bones206]

I worked construction through high school and college and we often used this clamp system while installing metal roofing. One time a big 250+ lb guy passed out from heat and we all watched helplessly as he ragdolled down the roof and tumbled over the edge. I don’t remember what kind of damage the clamp did to the roof, but I do remember that it held and probably saved his life.

The clamps were installed every so often, which was a pain for workers to have to constantly hook and unhook around, but I imagine that redundancy makes a big difference in system performance.