Pipe Hanger Load Rating 2

[StrLamp]

Hi Everyone,
I have a question. The consultant is asking for the pipe clamp capacity installed in different orientations. See attached drawings. I attempted to apply curved beam theory using Roark's formula, table 9.2 case 4, but the result is not quite convincing. Even though I reached out to the supplier, they are not helpful, stating that it is the responsibility of the end user. Another way would be a finite element simulation in Abaqus, which is beyond my reach. Would you please guide me on which theory or any other method to determine its capacity?

Thanks.

 

[dvd]

There are quite a few options that allow use of rated components - Anvil Pipe Hangers & Supports - why do you need to do it the way you are showing?

 

[StrLamp]

DVD,
It has already been installed as per the drawing prepared by a Mechanical P.Eng. of my company. I just joined this company, and I have been asked to determine the load rating. Based on my research, I found that this kind of job is more aligned with mechanical engineering rather than structural engineering.

Thanks!

 

[dvd]

Maybe try section 2.11 "Deflection of Curved Beams" in Design of Weldments, by Blodgett (which also addresses stress). You can buy the book pretty cheap from Lincoln Welding Foundation.

 

[StrLamp]

Thank you for the recommendation. I will take a look.

 

[BridgeSmith]

Seems to me the stresses on the curved portion would be almost straight tension, and the critical capacity at yield would be at the 'corner' (the junction of the flat and curve), which would be a bending capacity check compared to the moment generated by the eccentricity in the load path (force in the bolt multiplied by the moment arm between the nuts and the corner).

If you're looking for ultimate capacity after yielding/deformation of the clamp strap, that might be a tad more difficult, but I think the argument could be made that it would be the tension capacity of the net cross-sectional area of the strap at the bolt hole.

 

[Heaviside1925]

OP,
I agree with Bridgesmith, is your controlling case deformation of the strap or failure as a result of tear out? I am also curious to your point of why you are being asked to determine this and not a mechanical, not that you don't have the aptitude or skills, but I would see this more in the machine design realm of a mechanical.

 

[ETX]

I would calculate the load it takes to elastically yield each horizontal tab on the collar via a cantilever beam bending analysis and call that the limiting factor in design. The capacity of the support is then 85% of twice the load required to elastically yield a single tab. 85% is to account for a non-symmetrical load distribution in case the collar shifts to where one side picks up more load than the other. Then do a check that the tensile strength of the curved section (use the cross-sectional area of this region) exceeds the bending strength previously calculated. You're using an "off-the-shelf" rated component in a way it was not designed nor rated for. Be mindful of that and throw some conservatism in your design.

 

[bones206]

You're using an "off-the-shelf" rated component in a way it was not designed nor rated for.

It has already been installed as per the drawing prepared by a Mechanical P.Eng. of my company. I just joined this company, and I have been asked to determine the load rating.

Well that's not a nice welcome for the new guy

Pipe support engineering is a specialty that requires a mix of the mechanical and structural skill set. The off-the-shelf components are largely standardized to avoid having to reinvent the wheel for common situations. It sounds like someone at your new firm reinvented the wheel instead of choosing a more suitable support type, and you've been put in a position to be the "hero" and take ownership of their design choice. I would just like to throw out another option, which is to suggest replacement with a standard support configuration with a listed load rating.

 

[StrLamp]

Thank you, everyone, for your inputs and suggestions. They have been very helpful.