Spliced moment connection in Channels

[TonyES]

I have a client who has a 9' long channel and needs it to be 12'. It will act as a beam with a uniform load and be pinned on each end. For now he plans on welding a splice plate to connect the two channels (a 3' piece and a 9' piece) on one side of the web and on the top of the top flange and bottom of the bottom flange. Does anyone have any literature, example calculations, or ideas/concerns regarding this concept?
thank you.

 

[rb1957]

sounds feasible to me ... te welds are obviously shearing the load from one piece to the other ... a few details and we can help design the welds ... load, thickness

are you sure the channel section is good for the extra span ?

 

[MikeHalloran]

A whole new channel would cost less than the splice. ... unless there's some detail omitted.



Mike Halloran
Pembroke Pines, FL, USA

 

[TonyES]

Mike - these guys are actually steel fabricators and welding time is essentially free to them as opposed to ordering more steel.
rb1957 - the channels are 3/16" thick, 12" tall, and 4" flanges - its a custom shape and the material is unknown so I assume A36 for now. I modeled it in RISA and the new span is easily adequate for the small applied loads. I more hoping for something technical that I can use besides my "engineering judgement" in case I have to provide calcs for city comments.
thanks again

 

[MiketheEngineer]

Most people use the flange plates to carry the tension created by the moment and the web plates to carry the shear.

Real simple and works...

 

[port125]

We work with stair fabricators that will frequently use a full penetration weld to join two channels. This effectivly give a full capacity moment connection without the hassel of the web and flange plates. If they are steel fabricators they will proably have a CJP weld they prefer and (hopefully) know the prep that is required.

 

[rb1957]

if you've modelled them then you know how much load is in the beam at the splice and you should be able to design a weld to shear the load

 

[rscassar]

You say they are custom channels. Where they rolled or where they fabricated from plate? Are the channels still in the shop? If they are still in the shop then can they be spliced with full penetration butt welds. Otherwise provide flange plates and web plates and weld all around. You will need to provide the web plates otherwise there is no way of transferring shear force and the beam will deform at the splice location.

 

[rb1957]

butt welds in tension ? as strong as the parent material ??

 

[hokie66]

rb1957,
Yes.

 

[dhengr]

Rb1957:
I second Hokie’s YES. The weld metal and the HAZ will be as strong or stronger than the base metal if it is a good weld, properly made. This is done every day, intentionally, on much bigger structural members than an 8 or 10" channel. I’ve done 20' deep plate girders with 48"x5" flanges and 1.5 or 2" webs all full pen. splices and tension welds. They tested fine and are still standing and producing electric power.

 

[BAretired]

Yes*3.

BA

 

[HSIII]

Yes times 4. If you compare the stress of the weld metal in flexure or tension as compared to the base metal in flexure or tension, more often than not the weld metal is stronger (especially with 70 ksi weld metal). If the full pen weld is done correctly and can be verified good by NDE methods (UT being the most common), there should be every bit of confidence that it would work.

 

[MikeHalloran]

>>>butt welds in tension ? as strong as the parent material ??<<<

Steel is a marvelous material.



Mike Halloran
Pembroke Pines, FL, USA

 

[apsix]

Just to be different; No.
But only where fatigue is an issue, otherwise yes.