Steel Beam to Concrete Wall Connection

[etsbahamas]

I have searched but no real answer. We traditionally use 3/4" embedded plates with 1"x7" studs embedded into the 8" concrete to attach steel beams to the concrete walls. The problem is the connection from the steel beam to the plate. The concrete walls were moved in by 2 inches so we want to weld the two 4x4x3/8 angles to the beam web and fully weld it to the plate. I have heard some concerns about moment transfer and pull out of the embedded plate studs. I have seen this fully welded connection on several projects. Can someone advise if there is a reference and is this a major concern. The beam is a W30x90 and it will extend no more than 1/4" from the face of concrete wall and the top flange will not be welded.

 

[Lion06]

If you have a double clip angle connection and want it to remain as a simple connection, you can't have a weld return on the top of the greater than 4 times the weld leg or half the width of the part (See ASIC 360-05 J2.2b under the fillet weld terminations - it's item 2 on page 16.1-97).

If you weld the angles all the way around to the embed plate, it will attract some moment and will be a problem for the anchors.

 

[OHIOMatt]

Perhaps I am reading too much into the original post, but if you attach a 7" long stud to a 3/4" plate and embed that into an 8" wall, you only have 1/4" of concrete cover over the studs.

Other than above, what SEIT states is typical. Having only a small return will allow the angles to "flex" allowing some rotation.

 

[csd72]

Why not just bolt them with normal bolts and it will behave more like a single plate shear connection.

 

[etsbahamas]

Sorry the studs are only 5" long and we can't bolt them any more because the holes dom't fit since the wall has moved in.

thanks SEIT..how about I spec. that they only weld the vertical leg of the angle to the beam web. There is sufficient capacity in the vertical welds to hold.

 

[msquared48]

Not welding the top[ flange of the W30 to the plate is a big step toward minimizing the moment transferred to the wall.

I just don't understand why you are apparently welding the bottom flange.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[etsbahamas]

Sorry just to be clear, we are not welding any of the flanges.

 

[BAretired]

If you are welding only the tips of the outstanding legs to the embed plate, the connection should be sufficiently flexible. I would suggest no return top or bottom.

If you can decrease the thickness of the angles, flexibility will improve substantially.

BA

 

[nutte]

AISC recommends a return at the top of the angles equal to twice the weld size, no return on bottom. Look at Table 10-3 on page 10-47 of the 13th edition Manual. That's what I would use.

 

[hokie66]

Why not weld a shear plate to the cast in plate and bolt the beam web to the plate?

 

[MiketheEngineer]

A beam of that size might be quite long (or maybe just heavily loaded) - Don't forget about thermal changes...

 

[doka1]

Mike has a good point about thermal changes, I was on a project a while ago that was approximately 250 long without an expansion joint in the middle. On either sides of the building the steel framed into concrete walls with pockets. Both sides were welded during a hot summer day on july, after the first cool day in september the studs welded on the plates in the pockets made the concrete spall. If one didnt realize this was the effect of contraction it almost look like the pocket had failed. The EOR thought with a spacing of about 25' for columns, about 9 columns would allow for enough movement in the connection from the beam to the column. What was ironic is that his detail actually called for a bolt on the beam pocket but the detailer just called for the weld.

 

[connectegr]

StructuralEIT describes the corrected welded/welded angle connection. With a return only at the top of the outstanding legs, the connection is flexible and transfers shear only to the embed. Welding completely across the top is not prohibited.

http://www.FerrellEngineering.com

 

[BAretired]

Welding completely across the top would render it not very flexible.

BA

 

[connectegr]

Welding across the top in excess of a return only, can create a stress concentration in the weld and a crack can occur.

http://www.FerrellEngineering.com

 

[BAretired]

In that case, why would welding completely across the top not be prohibited?

BA

 

[connectegr]

I don't have my book, but I think it is prohibited. I have read research that suggests no return is better than a return greater than 4 times the weld size.

http://www.FerrellEngineering.com

 

[BAretired]

I am inclined to favor no return, top or bottom, but nutte says that AISC recommends a return of 2 times weld size on top only.

BA

 

[connectegr]

Yes. AISC recommends a return of at least 2 times the welds size and not more than 4 times the weld size.

http://www.FerrellEngineering.com

 

[connectegr]

Sorry. BA.
I just noticed that I said "not" prohibited in the earlier post. I was thinking not allowed and typing prohibited.

http://www.FerrellEngineering.com