Infill Concrete Block Wall Supported on a Steel Beam - What is the perferred detail?

[amecENG]

I would like to get some opinions on the preferred method of detailing a concrete block wall supported on a steel edge beam with open web steel joists framing perpendicular to the beam. In this scenario the block wall is just intended to be an infill non-load bearing wall one storey tall.

I have attached two options:

Option 1: the concrete block wall is constructed on top of the composite steel deck with a bond beam at the first course to span between the open web steel joists

Option 2: the concrete block wall is constructed directly on top of the steel beam and notched around the open web steel joists

 

[JAE]

To me - Option 2 sucks.

1. No direct shear connection between diaphragm and beam.
2. Masons have to cut block over the joists.
3. Rebar must be field welded onto beam without knowing exactly where the CMU cells are located (can be figured out but more work).
4. Lateral forces on the parapet are resisted by the beam flange, web, and to some extent flex in the joist top chord seat.
5. No lateral angle brace at the top of the wall to take lateral forces into the joist/deck system (beam will be torqued)

 

[CELinOttawa]

One, no question. Two is labour intensive (expensive) and structurally weaker with an obviously stronger detail readily available.

 

[amecENG]

Thanks for your responses.

In Option 1:
a) Would you specify the bond beam to be allowed to cure for 7 days before constructing the rest of the wall?
b) Would you provide the vertical dead load reaction on the open web steel joist shoe for the owsj designer?
c) Is it a good idea to let the weight of the wall bear on the owsj shoe or would you add a HSS between the joists (similar to a drag strut) even if it is not needed for diaphragm capacity?

 

[JAE]

a) I don't think the wall is that load bearing to require a cure period.
b) You could and probably should if the parapet is significantly high....or see c)
c) we add 2 1/2" steel tubes between joists to drag diaphragm shear in to the steel beam below.

d) we also provide the joist manufacturer any wind/seismic reaction loads from angle braces off the bottom of the steel beam.

 

[Archie264]

Just a quick drafting note on Option 1: consider making the lines for the vertical rebar and dowels much heavier; I looked right past them on the first glance. True, the contractor will eventually see them but will his estimator? Probably. But it's still better shown with heavier lines, in my opinion.

 

[amecENG]

If I use HSS struts between the joists I guess I don't need to use the bond beam to transfer the wall load between the joists.

 

[msquared48]

I, too, would have to go with option 1, but I see problems with that too, specifically the eccentric loading to the CMU wall below. The beam should be able to be shifted out to reduce this eccentricity. I would also prefer to see a more positive shear connection at the base, like a #4 @24 welded to the edge angle of the steel deck, extending up three courses of block (24").

Mike McCann
MMC Engineering