Through bolt to CHS

[sdz]

Can anyone direct me to a design guide for a through bolt connection to a CHS? E.g. see below where the CHS is in tension/compression. Since there is no bolt head/nut on the inside of the CHS to clamp the joint I understand the capacity can be lower than for a normal connection, however the curvature should mean it is not prone to local buckling like a flat plate. I've already looked at CIDECT Design Guide 9. I read the reference below but it talks mainly about RHS.

Ref: "Connecting Hollow Structural Section Members with Through-Bolts"

Connecting Hollow Structural Section Members with Through-Bolts | Steel Tube Institute

In this article, Jason McCormick, Associate Professor, Civil & Environmental Engineering, University of Michigan, discusses how to connect HSS section members with through-bolts.

steeltubeinstitute.org

 

[dik]

Any self-respecting bolt would crush the tube wall; you need a sleeve or maybe a nylock nut that can be snug... but not tight. You can get washers that have a curvature on one side, too.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Settingsun]

How is the connection loaded?

 

[desertfox]

Hi sdz

The tube will crush as the bolt is tightened because there will be an infinite point contact, as the tube crushes and more area comes into contact with the bolt head it will get harder to tighten but the joint won’t really be of use. What are you trying to connect to the tube because at the moment the diagram just shows a bolt through the tube?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[sdz]

Clarification. No, tightening the bolt won't crush the tube. The CHS is loaded in axial tension.

More of a problem is local buckling around the bolt. In a lapped connection the bolt washers prevent this but this is a connection without washers, at least on the inside.

The limit state equation for through-bolt bearing (AISC 360-16 Equation J7-1) is given as: Rn = 1.8FyApb (θ = 0.75). This applies to Rectangular hollow sections where the plate element is flat. I would expect that the curvature in a Circular hollow section would tend to prevent or reduce local buckling giving a higher capacity.

Does anyone know if this is included in any design codes or if there is any published research?

 

[Tomfh]

Clarification. No, tightening the bolt won't crush the tube.

The bolts can crush the tube depending on the dimensions. That image you showed with 0.9mm wall thickness would crush flat pretty easily.

 

[Agent666]

You say it's in tension, but what's it bolted to as you only show a bolt through a single CHS?

Is it related to the question you asked in AS/NZS forum? See my answer there, same applies regarding snug tight condition for bolt capacities to be applicable.

 

[Agent666]

I'm perhaps wrongly assuming those are washers though in taking a second look?

 

[dik]

Whatever the fastener... it has to be secured by some other means... nyloc or Locktite Red, or something... that's why I tried to distinguish between snug in my original posting.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik