Composite Beam with openings on both sides of flange

[celtickid]

I have a series of 32' long girders in a composite floor system that happen to have one end (about 24" lemgth) without a composite slab on both sides of the flange due to a 2 story CMU wall passing through (see uploaded file attachment). Of course RAMSteel will not design the girder as composite but common sense tells me that since most of the member has a composite slab, it could still be designed as composite provided that the beam location at and near the end with the opening is checked as non-composite for the moment at that location. I am a little fuzzy on the horizontal shear aspect though..I realize the horiz. shear gets greater towards the ends of the beam but since the opening is still less than the maximum stud spacing (8 times the slab thickness)everything should be fine. Am I missing something? Does anyone know of a good design example for this?

 

[JAE]

celtickid,

Take a look at the new 13th Edition Specification, Commentary for section I3.2d - under the last paragraph of (1), it reads:

[blue]"Trenches oriented transverse to composite beams should, if possible, be located in areas of low bending moment and the full required number of studs should be placed between the trenches and the point of maximum positive moment. Where the trench cannot be located in an area of low moment, the beam should be designed as non-composite."[/blue]

So with this, it appears that, since your "trench" is at the end with low moment, you could proceed accordingly.

 

[msquared48]

Assuming, of course, that there is no positive moment at the end of the beam, which would be an eitirely different animal here...

Thinking outloud too, in that the steel beam frames to the steel column, it must pass through the CMU wall. There is probably at least an 8 to 16" deep horizontal bond beam there. Why not use that bond beam as an extension of the slab to maintain the continuity of the composite action for the steel beam. Then your worries go away, except for the strength of the bond beam grout.

Mike McCann
MMC Engineering

 

[celtickid]

Thanks for the two replies.
(I guess I need to get more familiar with the 13th Edition of the steel code...I can't seem to pry my fingers off the 9th.))
To the second responder: There will be a small positive moment at that location, but I would check it for the steel beam alone.
Not sure I understand the CMU bond beam approach...while it sounds certainly outside the box, in this case, I have to keep the CMU non-load bearing....I would be a tad worried that engaging it (load bearing) would create some performance problems with the wall... If you have ever done this, I would be curious to see how well it worked out for you. Thanks for the input.

 

[msquared48]

Never had to do this before - just an idea.

Mike McCann
MMC Engineering

 

[haynewp]

2ft out of 32ft length without slab, I don't see it as much of a problem.