CJP flange weld, no backer at web

[CTSeng]

Working with a fabricator that wants to do a CJP field welded flange moment connection with 2 separate backer plates either side of the beam web and no access hole thru the web at the top flange only. I know this is not in exact accordance with the procedure but seems reasonable. Should this be allowed in a non-seismic application?

 

[connectegr]

Weld backing bars must be continuous to avoid stress concentrations. Weld access holes allow space for continuous backing, but also aid to alleviate stress due to weld shrinkage.

If the full tensile strength of the flange is not required there may be other welding options:
Partial penetration welds would not require backing. But they allow for no root opening, which is difficult (maybe impossible) in the field.

Fillet welds. But they must be on both sides of the flange, which requires overhead welding. Single fillets should not be using in tension.

Another option is bolted endplate or paddle plates. All welds can be shop applied, leaving only bolting in the field. Paddle plates can be problematic in the field, maintaining the alignment.

Maybe even field welded paddle plates. Paddle plates can be field or shop welded (usually the bottom plate) to the column. The beam does not require shop prep for welding. The paddle plates are fillet welded to the beam flanges in the field. (note: top plate should be narrower than the flange, bottom plate wider than the flange)

http://www.FerrellEngineering.com

 

[HgTX]

Are they planniing to leave the backing bars in place or remove them after welding?

Hg


Eng-Tips policies: faq731-376

 

[CTSeng]

The backing bars will be left in-place, with ultrasonic testing.

They did not leave enough room for weld access holes at the top flange because of welded shear angle connections are rather high on the beam web because the beams have a rather steep slope (5:12).

The comments are appreciated.

 

[connectegr]

I would not recommend clip angle shear connections for flange welded moment connections. Clip angles to not allow for weld shrinkage in the flange welds. We have seen cases where cracks resulted in the welds. AISC recommends single plate connections with short-slots. The bolts should be tightened after the welds are completed and have cooled.

I don't know the size of your beam. And obviously the flange thickness would impact the amount of weld shrinkage that occurs.

If this is an "as erected" condition, then I may be more open minded. What is the beam size? What is the moment? The force and flange size is very relevant.

Otherwise, the web connection should be changed to allow room for the weld access holes and a continuous backing bar. If the web connection needs to be reduced, what is the shear?

http://www.FerrellEngineering.com