Cantilevered Channel Moment Connection 1

[SactoGirl]

I am in desperare need of some guideance. I am trying to design a cantilevered channel that is welded to a base plate that will be bolted to an embedment plate into concrete.

I have already completed the wed design, assuming the channel's web weld will take all the shear and the welds on the top of the flange will take any forces from the moment. This brings up another questions. Since the Channels flange is tapered would I use the average thickness to determine the minimum weld thickness?

How do I go about designing the base plate thickness? What about ecentricities?? I have a design example for using a Wide Flange but I have never seen a channel used in this way. Please help!

 

[larsacious]

SactoGirl,

Just use the "tf" given in the aisc manual in determining the minimum weld thickness. If there are fatigue/seismic issues you may need to be careful how close you terminate the weld to the tip of the channel flanges as this is a fatigue crack propogation hot spot.

Also, here are a few comments regarding your proposed detail:

1) Have you checked prying action with respect to the embed plate bending between the headed studs?

2)Why is the plate that is welded to the channel bolted to the embed plate? Are you planning on welding the bolts to the embed plate? If so, have you considered how the bolt welds will interfere with the plate seating flush against the embed plate?

I would recommend revising the detail by shop welding an angle to the embed plate, providing erection bolts to connect the channel to the angle, then field welding the channel flanges to the embed plate and the channel web to the angle.

If you can not use field welds then I recommend that you use slip critical bolts, shim plates, and angles shop welded to the embed plate to connect the channel web and flanges.

Good luck!

 

[rscassar]

I also find the detail somewhat confusing? Why not field when the channel directly to the baseplate. Or fabricate the baseplate welded to the channel in the shop and then fix directly to foundation bolts which are cast-in or epoxied to the footing.

Since the Channels flange is tapered would I use the average thickness to determine the minimum weld thickness?

I don't quite understand what you are asking?

I think this connection detail would require a complete penetration groove weld. Particularly if the channel is working near it's capacity.

 

[csd72]

You cannot get properly pretensioned bolts on a welded stud so there will also be some additional rotation associated with that.

If you absolutely have to have bolts then threded inserts welded to the back side of the plate are also an option though the above limitation still applies.

 

[paddingtongreen]

The weld for the threaded studs on the embed will force large holes in the baseplate!

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Prestressed Guy]

Due to all of the problems with threaded studs, I would use through-bolts in the embed plate with the heads tack welded to the back of the plate. that way you can standard bolt clearance.

 

[BAretired]

I like the suggestion of Haydenwse. It seems to me to be not only simpler but more economical.

BA