Butt Joint or Tee or Corner Joint

Date 10-27-2010 16:32

Looks like a butt joint to me, now if it were alot thicker I could see a Tee joint like where the flange is welded to the face of the column but this is not the case.

By jwright650 (*****)

Date 10-27-2010 16:37

I don't know the specifics of how your joint is applied, and maybe you have no choice about changing the joint to a B-U4b which would allow you to transition the joint per 2.17.1. I never liked to have the backing bar where you have it in your sketch, due to the notch/stress raiser created there.

By eekpod

Date 10-27-2010 19:32

Ironically that was my proposal was to remove the B/B.

But as drawn I guess it could be considered TC-U4a. It's just that with both members in the same plane (horizontal in this case) I'm leaning towards a the butt joint vs a Tee joint.

By jwright650 (*****)

Date 10-27-2010 19:45 Edited 10-28-2010 00:37

Is it possible in your case to flip the bevel over and place the backing bar on the flush side of the joint(provided it isn't in the way of something) and then you could make that 2.5:1 transition between the two thicknesses.

edit: added correct ratio at transition

By 803056

Date 10-27-2010 22:28

I like your way of thinking John.

Best regards -Al

By fschweighardt (***)

Date 10-28-2010 01:19

That is probably the easiest, burn the 2.5:1 transition after you cut the weld bevel and keep the BB on the flush side so it bridges the gap like it is "supposed" to

By swnorris (****)

Date 10-28-2010 17:19

eekpod,

Take a look at Figure 5.4 in the 2010 code (pg. 217) for typical profiles for butt welds between unequal thicknesses.

By jwright650 (*****)

Date 10-28-2010 18:13

I forgot all about the newly revised Fig. 5.4....good job Scott for pointing that out.

By jwright650 (*****)

Date 10-28-2010 18:16

If the thickness transistion is small like 5/8" to 1", it isn't too bad to provide the transition while welding with filler material, but it can be done several ways just as you pointed out about chamfering the thicker of the two thicknesses or a combination to achieve the same result of 2.5:1

By eekpod

Date 10-29-2010 11:16

the joint can not be changed or flipped, its already in place.
we ended up removing the b/b and chamfering the thicker piece and re-welding the second side to get the transition.

By 803056

Date 10-29-2010 22:01

Back to your original question, that is, whether the joint configuration is a butt joint or a t-joint?

You need to look at how the load is transferred from one member to another. If the load is either in compression or in tension, the butt joint, where the axis of the members are parallel, does not require the direction of the load to change as it transfers from one member to the other. On the other hand, the T-joint or the corner joint, where the axis of the members are approximately perpendicular to each other, requires the direction of the load to change as it is transferred from one member to the other. The change in direction usually causes bending or a prying action.

The sketch depicts what I mean by a change in direction of the applied stress. I did not address shear loads where the loads are transferred a little differently.

Best regards - Al

By eekpod

Date 11-01-2010 11:46

thank you Al for that information.