Toggle Bolts for Fall Protection System into a Metal Deck 2

[muhammeta7]

I am working on a project for work. The system we are using for the fall protection is Latchkeys but I am having trouble calculating the point loads on the 4 toggle bolts being inserted into a metal deck that has an I=0.959 in4/ft St=0.567 in3/ft
and Sb= 0.492 in3/ft. The decking is 3" and 20 gauge. Is there anyone that may be bale to help me out.

 

[Duwe6]

Suggest you quit trying to calc, and "ask the parts". Dummy up several connections and send them to a test lab for tensile testing. When you get a 'feel' for the average failure load, reduce it by a Safety Factor of 3 or 4. Also, keep in mind that the 'shock-absorbing' lanyards that are probably going to be used will limit the peak force to under 1000 lbs.

 

[muhammeta7]

I did the loads on the bolts themselves and each bolt ended up coming out to 812 lbs per bolt. I didn't factor in the rigid insulation and epdm membrane but I would like to assume that it takes off some of the tension away from the metal decking. My next step moving forward is figuring out the pull out strength of the 20 gauge 3" metal decking. Being that I went to school for chemical engineering I only have a small grasp of all the concepts. I need a lot of instruction but my boss obviously expects me to figure all this stuff out.

 

[EdStainless]

If this is for personnel safety then I suggest that you retain and expert for this.
Is you boss willing to bet someones life, and his job on your calculations?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Tmoose]

"Anchorage device: Latchways Constant Force™ post for Derbigum membrane Roofing with mechanical attachment through the insulation to either the crowns of the steel deck, Concrete or ply deck using Latchways toggle bolts/Threaded M8 bar. All fixed in accordance with our installation Data sheet 65619-98-4 and Weathering to Derbigum membrane needs to be tested and approved by Latchways plc in accordance with Manufacturers recommendations."

http://www.latchways.com/sites/default/files/PDF/Latchways-ManSafe-for-Roofing-(US).pdf

 

[muhammeta7]

My boss has checked the toggle bolt calculations. The only other calculation left is to figure out the pullout strength from the metal deck. I've been researching online but am having trouble getting direction in this area.

 

[chicopee]

Looking at page 11 of the link provided by Tmoose, the resistance appears mostly by shear and not by tension. Also the load absorbed by the constant force post is 2250lbs which I would think is the value to use to determine anchorage strength.

 

[Tmoose]

"The decking is 3" and 20 gauge."
"The only other calculation left is to figure out the pullout strength from the metal deck."

I'm picturing this -

http://leathermanlibrary.com/albums...In Use Images/Pocket-size/Wave_Can Opener.jpg

despite the picture on page 7 here -

http://www.latchways.com/sites/default/files/PDF/Latchways-ManSafe-for-Roofing-(US).pdf

 

[MikeHalloran]

It appears that the fall energy is dissipated by uncoiling a steel helix 'the hard way', i.e. on a diameter and not axially.

... but that doesn't tell you squat about the toggle bolts interacting with the thin steel sheet in the roof. The nice diagram suggests that the toggle bolts are loaded partially in shear, but there must be some tension.

In your position, I'd ask the anchor supplier for test results with photographs of an anchor installation similar to what you contemplate.



Mike Halloran
Pembroke Pines, FL, USA

 

[berkshire]

Duweb6 hit it ,
Do it by test, make a dummy connection and get it tested. Even though some connections are done with a large number of self drilling screws and it looks like overkill, they are only as good as the worst installer.
B.E.

You are judged not by what you know, but by what you can do.

 

[Ron]

Toggle bolts in a corrugated metal deck should be tested, not calculated. The orientation of the toggle relative to the deck flutes makes a difference, as does the flute width. There are numerous decking types, so make sure you have the right one.

Neglect any benefit of the membrane or insulation....they are negligible.

Also, since this is a toggle bolt with no thread engagement in the deck, you are not looking for a "pullout" strength but a "pullover" strength...as if the head of a bolt were being pulled through the decking.

 

[tbuelna]

I saw one statement that said the post the lanyard is connected to is designed to collapse when the radial force exceeds one ton (2000lbf), which is apparently intended to dissipate some energy and prevent the attaching fasteners from breaking loose of the metal roof panel. Thus it would seem safe to assume the system is at least good for an initial radial impulse force of 2000lbs applied to the lanyard. Something like a 200lb roofer at 10g's. I also imagine the lanyard stretch will help quite a bit.

 

[Tmoose]

I am completeley ignorant of corrugated roofing construction ( and a bunch of other subjects too) but I suspect there are seams in corrugated roofing every now and then. I wonder if a toggle or 2 happened to end up near a seam it might be easy to peel open the seam, compared to pulling the toggle thru, or untoggling the toggles.

 

[Duwe6]

Test, don't guess. And calc's with all the unknowns like seams and fastener breakaway strengths are just educated guesses. And remember, there will be a person attached to this anchorage. The consequences of failure are immense.