Bolting through RHS 2

[km501]

Hi all,

Basically I'm looking for some help on bolting through a RHS. The connection I need help with is essentially a sleeve connection, one RHS fitting inside another and secrued with 6 bolts. Due to dimesional limits (i.e. it has to fit inside a standard 40ft container) we can't just use a bolted flange connection to connect them. I'm mainly worried about how much preload it would be possible to put on the bolts without crushing the section.

I'm actually a pipeline engineer so all my experience is with threaded and coupled or welded pipe so this is a bit outside my experience. Can anyone point me in the direction or a design code or standard?

Thanks for your help.

 

[hokie66]

A lot would depend on the size of the RHS sections and the wall thicknesses. How snug is the fit of the telescoping sections?

In order to tighten the bolts fully, you could use welded pipe sleeves through the inner RHS.

 

[km501]

Essentially a 450x250x16 RHS is going to fit inside a 500x300x25 fabricated RHS, so it's designed to be pretty snug! We then have six M36 bolts running through the connection.

It's also worth mentioning that this structure is designed to be placed on the back of a boat so the connection can't losen as it heaves up and down in rough seas.

 

[hokie66]

In that case, I would definitely use pipe sleeves welded through the 450x250 RHS and fully tighten the bolts.

 

[km501]

Thanks for your help. Just to make sure I know what you mean. Your talking about pipe running across the hollow section (in the direction the bolts are in) in order to stiffen it, right? Is it feasible for someone to weld inside an RHS, all be it quite close to the end?

 

[csd72]

Thats the idea, the bolt will actually go through the middle of the pipe sleeve so ensure that the internal diameter is sufficient for the bolt plus tolerances.

We specify this type of details for down to 4" square tubes and they dont have a problem welding it. You can specify a groove weld all around at each end if necessary.

 

[hokie66]

Yes, csd72 has beat me to it. Weld on the outside and grind flush.

 

[km501]

Thanks alot for your help guys. Sorts the whole thing out quite nicely.

 

[km501]

Also, one last thing, does any one have a reference for a code or standard that would advise this approach. All I need is one sentence that says, for bolting through an RHS use a pipe sleeve. Again, thanks alot for the help.

 

[csd72]

No reference, just common sense.

 

[hokie66]

Sorry, I don't have a reference either. I don't think I invented this type connection, but have been using it for a long time. The use of hollow sections as structural members has been steadily increasing, but I am not aware of a comprehensive source on connection detailing.