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Bolting of the follow sections
10

Bolting of the follow sections

Bolting of the follow sections

(OP)
Hi there,

could someone provide some general guidance on how to bolt together multiple hollow sections? I am using only rectangular sections.

Also, I attached the figure below and am interested in which of the two ways is the "correct" one, when it comes to connecting two rectangular sections side by side.

Many thanks,

Uroš

RE: Bolting of the follow sections

Hi
The top picture is better but the problem is reaching down into the sections to tighten them, you could I suppose put cutouts into the walls of the section to access them but that reduces the section strength.
If you use the bottom figure you will end up crushing inwards the section walls as you tighten the bolt

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

RE: Bolting of the follow sections

Agree with desertfox, the top sketch is OK but the lower one potentially problematic.

Will there be access issues due to length of the tubes?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Bolting of the follow sections

It depends so very much on what the loads are, what direction the loads are applied and what you are trying to do.

They both have details that are sub-optimal "in general", but those weaknesses may or may not be critical for whatever you are doing.

RE: Bolting of the follow sections

Bozo_Sam,

Your first drawing with the inside walls bolted together is good. Your other drawing is very bad. Bolts are easily able to crush thin-walled tubes. If bolts are not clamped down hard, they come loose.

Consider drilling through the tubes, welding a solid round bar through the holes, and drill your bolt clearance holes through the bars. Now, you have a solid, clamped section.

--
JHG

RE: Bolting of the follow sections

Another way would be to use 2 bolts: One by the top wall and one by the lower wall. You'll still get some crushing.

RE: Bolting of the follow sections

Solid round bar + drilling? I've seen tubes welded in SHS, same effect but much less work...

RE: Bolting of the follow sections

kingnero,

It has to have a hole in it. I won't ask the welder how it got there. Drilling a hole through a bar is potentially more accurate.

--
JHG

RE: Bolting of the follow sections

You'll get much stronger and stiffer results if you bolt through external flanges welded to the tube walls. Even if you weld in a spacer to prevent crushing of the tubes, the load path from the section into the bolt passes through the region of the section with the lowest stiffness.

RE: Bolting of the follow sections

(OP)
Hi guys,

thanks for the extensive replies. This has been most helpful. If I try to summarize the suggestions, it would be better to have the option with the short screw.

If possible the best way would be to weld an additional cylinder on both sections as in the figure below. This would provide stiffness and stability to the connection.

RE: Bolting of the follow sections

Hi Bozo Sam

Yes that configuration will work but just make sure the tubes you put through the section are just below the surface of the section.

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

RE: Bolting of the follow sections

Sam, in your haste to post you left the annotations and notes off your 7 Aug 20 08:22 posted image, and in so doing added vast mysteries.

I am scratching my head about what is welded to what, and what the hatched ( tube ?) and un-hatched (tube) do in the arrangement.

RE: Bolting of the follow sections

Bozo ....

I would just clamp the tubes together and run an intermittent stitch weld along the top corners and bottom corners where the two tubs were in contact.

But now your gonna tell me that the tubes must be able to be dis-assembled ?... Right ?

And that you forgot to tell us this before ....

MJCronin
Sr. Process Engineer

RE: Bolting of the follow sections

(OP)
Hi guys and thanks again for the effort.

Do you think having a 2mm chamfer as a preparation for the filled weld would be reasonable?

Sorry for the confusing figure before.

RE: Bolting of the follow sections

You should look at how the external loads are applied to the tubes. One center bolt versus other methods will have different stress/deflections/friction clamping.

RE: Bolting of the follow sections

Bozo_Sam,

Are you the welder or the designer?

Specify that you want the bar/tube welded through your rectangular tube. Welders are skilled, and will find a good way to do it. When you inspect it, it will be two pieces of metal, ground flat on both faces.

Get Mongo the installer to install the bolts.

--
JHG

RE: Bolting of the follow sections

Too many welds that, at the end before assembly, have to be ground together with the head of the pipes. No reason to do this, also because after assembly the weld don't do anything : it is enough the pipes to avoid crushing of hollow sections

RE: Bolting of the follow sections

robyengIT (Mechanical)
7 Aug 20 19:04
Too many welds that, at the end before assembly, have to be ground together with the head of the pipes. No reason to do this, also because after assembly the weld don't do anything : it is enough the pipes to avoid crushing of hollow sections

agreed! the sleeve over the bolt is to prevent crushing the tubing or pipe.
it needs to a tad smaller to let the bolt compress properly.
once torque it should be fine.

RE: Bolting of the follow sections

If it is accessible, weld the short sleeves with end plates that having predrilled hole should work. Sizing the sleeve for compression.

RE: Bolting of the follow sections

Drill the inner hole diameter for clearance around the bolt. Drill the outer hole diameter for clearance around the sleeve. It will then behave like like the first drawing in the OP. No welding and no need for access to the inside of the tube. Use one drill to drill through both sides of the tube then enlarge the outer hole.

RE: Bolting of the follow sections

It is a pretty good idea, if large rotation of the HSS is permitted. The contact between the HSS wall and the washer provides friction that prevents movement. The contact can be lost when bearing directly on the sleeve. But the above method is preferred if this is not a single bolt connection.

RE: Bolting of the follow sections

How about just a thick weld washer to distribute loads out to the flanges?

RE: Bolting of the follow sections

What are you actually trying to acheive in bolting them together? What are the applied loads? What are the RHS's doing?

RE: Bolting of the follow sections

You haven't explicitly stated that the bolts must be concealed within the tube - if you can have some external connection material this becomes much easier.

RE: Bolting of the follow sections

OP said of one arrangement "If possible the best way would be to weld an additional cylinder on both sections as in the figure below. This would provide stiffness and stability to the connection."

I think a single bolted connection is a pivot if asked to resist any rotation, even if tightened by Mongo. In a triangulated frame the lone bolt at an intersectionwould mostly not be asked to resist rotation

I don't think I've seen the OP provide details of what this joint is supposed to do ( or NOT do).

I can imagine some sitchee-ations where tube internal reinforcement is not needed, some where exquisitely detailed welded internal reinforcement is required, and still others where any bolted joint will fail killing loved ones and bringing at best a lifetime of notoriety and shame to the designer.

http://www.ducati.ms/forums/attachments/supersport...

RE: Bolting of the follow sections

CANPRO,

Double check your welding detail, and provide procedure if you don't mind.

RE: Bolting of the follow sections

The HSS section will collapse under the compressive load of the bolt extending from the outside surface of the HSS to the outside surface of the opposite HSS. We all agree on that. The problem is to keep the HSS from collapsing. Several proposals have used tubing to prevent the HSS from collapsing. I propose solution that doesn't require any welding. The tube in any case has to resist the compressive load of the bolt. That would pretty much eliminate a thin wall tube. The capacity of the tube would have to be equal to the compressive force developed by the bolt. So, I call the tube "a heavy wall tube".

The clamping force must be tranferred to the faying surface where one HSS wall bears directly against the other. I believe that is accomplished by my solution. Note that the heavy plate washers bear directly on the heavy wall tube at both ends. The ends of the heavy wall tubes bear directly against the inside of the HSS walls. There doesn't have to be any welding. The weld would have to sustain the full forces of the bolt, which is no small task. My solution requires access from one side of the HSS sections, so the connection can be placed anywhere along the length of the HSS. If the heavy wall tubes are a little too long or a little too short, it doesn't matter as long as the plate washers bear directly against the heavy wall tubes. See the attached sketch.

Best regards - Al

RE: Bolting of the follow sections

Yes, I like it.

RE: Bolting of the follow sections

Thanks. I tried to keep it simple and keep in mind that the bolted connection may be such that it isn't accessible from one end of the HSS.


Best regards - Al

RE: Bolting of the follow sections

GTAW : similar to what I suggested on 07 august. Your suggestion is better if you fit the tube while you are erecting the structure. If you need an early preparation I think my suggestion is preferable

RE: Bolting of the follow sections

retired13, what would you like to double check? not sure what procedure you'd like - pretty standard welds.

RE: Bolting of the follow sections

No welds with my detail. No machining other than use of a bandsaw to cut the spacers to length and a couple of drills to drill the proper sized hols.

I tried to stay away from the welding. The spacers (heavy wall tubing) could be off center when they are tack welded, the wall of the tube would have to be increased to provide sufficient bearing on the HSS and permit tack welding. Will the welds act in unison with the tube wall? If the bearing against the wall of the HSS is insufficient, could it could crush the corner of the hole?

The advantage of robyeng's detail is the heavy wall tubing would be placed and tack welded or welded completely before erection. The question is: do you assume at least a portion of the load path goes through the weld? Do you want to make a full circumfential weld between the HSS and heavy wall tube? What portion of the load goes through the weld, all of the load, half the load, none of the load? Are you going to grind the excess weld if it projects into the area of the faying surface?

I tried to simplify the connection and eliminate any steps that would increase fabrication time and cost. So, yes, to a large extent it is similar to robyeng's approach, but simplified to eliminate a machining operation, a welding operation, and possibly a grinding operation. Isn't that what "Barnstorming" is all about? We had several ideas thrown out to the group and we each looked at the proposals and tried to improve what was offered.

I would like to think that robyeng and I were thinking along the same lines of thought.

There are a few unknowns in this problem. 1) Is this a "slip critical" connection? 2)Where is the connection located? Near an end, toward the middle of the length of the tube? 3) Is the connection a single bolt connection? That's not good if this is fitted and bolted in the field. 4) Do the tubes rotate relative to each other. Before settling on a plan of attack, I would want to know more about the application.

Best regards - Al

RE: Bolting of the follow sections

I don't like that detail at all- You need welds to transfer load into the external wall of the tube. The amount of clamping force applied to the inner walls of the tubes is also highly dependent on the tube wall thicknesses and exact lengths of the spacers.

This is all pretty much moot because we don't know any detail about the service conditions of this connection. But an external connection is still better that anything we've tossed around so far.

RE: Bolting of the follow sections

There's no need to put any clamping forces on the outside surface of the HSS. The faying surface is where the two HSS section make contact.

Care to include a sketch? Show us the percieved load path.

Best regards - Al

RE: Bolting of the follow sections

FWIW, this thread reads just like an undergrad brainstorming session. Not criticizing, just saying.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Bolting of the follow sections

has the OP said what this is for? what is he trying to build, no clue

RE: Bolting of the follow sections

Quote (gtaw)

There's no need to put any clamping forces on the outside surface of the HSS. The faying surface is where the two HSS section make contact.

You may be right- but without more detailed information from the OP on what the loading condition is, we don't know.

Information on the environment this will live in would also help us identify whether or not the path through the assembly for ingress of water is acceptable. But we'd need more information for that too, and and this point I don't think we'll get it.

RE: Bolting of the follow sections

CANPRO,

How these welds are to be made?

RE: Bolting of the follow sections

retired13, you weld the clip angles to the HSS and then bolt them together.

RE: Bolting of the follow sections

You can't weld the backside of both angles to the HSS, can you?

CANPRO,

You are correct. I apologize for my mistake.

RE: Bolting of the follow sections

The welds within the red circles would be categorized as flare bevel grooves. If the governing code is one of the AWS structural welding codes, the maximum size of the weld is a function of the radius, welding process, and welding position.

They would most likely be shop welded prior to being field assembled.

Best regards - Al

RE: Bolting of the follow sections

Quote (retired)

You can't weld the backside of both angles to the HSS, can you?

The two sections aren't bolted together when being welded in this scenario.

RE: Bolting of the follow sections

OP Sam logged in yesterday August 19. His last post (on this topic) was Aug 7.

Methinks he has found other interests.

RE: Bolting of the follow sections

GG,

Thanks. My brain went for vacation that day.

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