Bolting of the follow sections 10

[Bozo_Sam]

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

 

[Compositepro]

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.

 

[r13]

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.

 

[BUGGAR]

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

 

[12345abc6ttyui67]

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

 

[CANPRO]

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.

 

[Tmoose]

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/attachm...hat-frame-color-should-i-use-my-95-ss-042.jpg

 

[r13]

CANPRO,

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

 

[gtaw]

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

 

[r13]

Yes, I like it.

 

[gtaw]

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

 

[robyengIT]

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

 

[CANPRO]

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

 

[gtaw]

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

 

[SwinnyGG]

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.

 

[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.

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

Best regards - Al

 

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."

 

[mfgenggear]

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

 

[SwinnyGG]

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.

 

[r13]

CANPRO,

How these welds are to be made?

 

[CANPRO]

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