How to determine the 5000 lbs strength of anchorage point?

[akrekan]

Hi all,

I am new here. I have read a lot regarding the anchors and anchorages here but couldn't find the answer to my question.

I want to know how to determine the 5000 lbs strength of anchorage points. What is the calculation to determine that?

We are now designing fall protection system for the roof workers. We will fix scaffold tubes to the I-beams and pass the horizontal lifeline through the eyes on the scaffold tubes. How can I make sure that it meets the requirements?

Thanks.

 

[CANPRO]

There is no cook-book calculation for what you're looking for...you need to run the numbers on whatever situation you have. Just follow the load path. You can also pull test the anchors fairly easily and depending on what your local regulations are and the type/application of the anchor you may be required to pull test.

If you're fixing tubes to the steel beam and then the lifeline to the tubes, why not just attach the lifelines directly to the beam?

 

[darthsoilsguy2]

although i've climbed scaffolding at least a few hundred times... i'm having trouble figuring out where the eyes are... maybe if you submitted an image, you might get more response

 

[Archie264]

You're playing with fire. Hire a structural engineer.

 

[ztengguy]

Just make sure the fixture is checked by an engineer and have him sign and seal it, that way you know it meets the requirements.

 

[John2025]

Scaffolds? Life lines?
I'll dabble in a lot of things, but for that I don't just want an SE, I want one with experience working on them.

 

[charliealphabravo]

Horizontal lifelines and multi-point anchorages are some of the most advanced aspects of fall protection design. If you are intent on doing the design I would suggest putting your hands on the appropriate standards and regulations for your jurisdiction and taking some training and consulting with someone who has some experience. The manufacturer for the system you will be using is a good place to start. Those guys are often closely involved with the regulating committees and know the pitfalls of design.

 

[akrekan]

Thank you for replies guys. May be the picture attached can help?

 

[LittleInch]

I'm looking forward to the replies on this one.... The pole attachment to the roof and simple fillet welded u bolt look woefully inadequate to me to withstand 5000 lb (2 tonnes). Think one or two of those pick up trucks behind the photo hanging off that??

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[CANPRO]

that's not for fall arrest attachment, that's for a guardrail. Huge difference... 5000lbs vs. 200lbs

But maybe that's all you need for your application. I think you need to take a step back and first determine exactly what it is you need and what you're trying to achieve with this.

 

[JStephen]

If you're going to be using this on a continuing basis, it'd make sense to have somebody more familiar with it all to do the design.
OSHA requires the 5,000 lb strength, but there's no guarantee that there's anything in the vicinity to actually anchor to, and that's part of the challenge.
OSHA also allows that load to be reduced where you can show that fall-arresting lanyards will limit the force, and that'd be a major factor on a design like this where available strength may be limited.

 

[racookpe1978]

Doesn't look right.

The cantilevered red and white striped posts are held on how?
To what what steel underneath?
To try to hold who? (How many? at what weight?)
I'm assuming the loops on the red-and-white poles are for "wire ropes" to act as the lifelines or as the guard rails?

 

[graybeach]

I have done a fair amount of this kind of work along with supporting microwave antennas and cameras on buildings. As others have mentioned, the tough part is finding something to resist the moment. Just attaching to single wide flange beams doesn't cut it because they are weak in torsion. Sometimes I have had to design a grillage of beams that would be installed between roof joists. On sloped roofs, I sometimes get lucky and can get enough resistance by attaching the post to both the rafter and the joist.

For fall protection, I never factor the 5000 pound design load. I assume 5000 pounds is the limit state and compare it to the structure's nominal resistance times phi.