Glass Block Masonry Lateral Support

[akastud]

2006 IBC section 2110.4.3, requires lateral support of 200 PLF. How do you interpret that, does my support have to be able to resist 200 PLF along the 4 sides of the panel? Or is it 200 plf times the horizontal direction of the block applied as a point load into the jamb or possibly as 200 plf over the height of the panel into the jamb?

Thanks
akastud

 

[JAE]

The paragraph reads that "lateral support" (which is either anchors at 16" o.c. or channel-type restraints) must be designed to resist...200 plf.

Earlier it states that the lateral support must be along the top and sides.

So I would say the strength of the top and side lateral restraints (be they anchors or channels) must resist 200 plf along their length.

 

[akastud]

JAE, I absolutely agree with that, and have no problem with that, but I have masonry walls beyond the channels. How far out do I have to carry that load. Do you think after I anchor the channels, I am done with that larger load, or do you think I have to design my jambs and lintels for that load as well. I think the word "support" takes me to the masonry design as well, but it seems like an excessively large load to resist by the jambs.

akastud

 

[JAE]

I'm not sure what you mean by "masonry walls beyond the channels".

I think the intent of the code is that you have this finite glass block wall with definitive ends and a top. Then you have some form of channel that cradles the edges and top to prevent out-of-plane movement.

With the 200 plf load on the channels, the channels themselve must be anchored to something to support the wall. That something must be anchored to the main structure to take the loads on out - full load path.

 

[akastud]

I apologize, I confused you a little, and now I know why. The glass block sits in a channel that is anchored to a masonry wall. The glass block (10' x 10') sits on either side of a 6' wide masonry jamb. The confusion comes in what loads to be placed on the jamb which spans between floor and roof diaphragms. I hope you are still with me...

So in designing the jamb. At the bottom and top of the glass block, I have 10'(200 PLF) 2000# and then I have 400 plf along the jamb between the 2 point loads. So for these two glass block windows which in theory add 1125 total pounds of seismic load to my jamb (based on weight and seismic acceleration) instead I have to design my jamb for 8000 total pounds of force. This doesn't seem right to me.

Thanks,
akastud

 

[JAE]

It doesn't seem right to me either, but that is how it reads, I guess.

Keep in mind that the 200 plf only applies at the top and sides...not at the bottom of the glass block panel. That will help a little, but not much.

 

[akastud]

I guess my question is how far to transfer the load. You mentioned full load path, and I would typically not argue with that point, however with seismic loads you often design elements with higher force capacity than the system as a whole can take. Diaphragms, collectors, steel attachment elements etc. So to what point do you think I have to go. There are not many masonry walls that will take 6000 # (reduced to account for the bottom) out of plane load in addition to the self induced seismic forces.

akastud

 

[whir]

I believe that you could argue it the other way also. The code is probably intending to treat the glass unit support the same way that you would treat a component with a small tributary area by putting the minimum 200 plf to account for very localized loading. I think you could justify applying that load to the channel and it's connection and then design the lintel and jamb based on its component wall loads as you would for any other type of opening.

 

[akastud]

Whir,

That is my argument, but I don't know if it is correct and I am asking for opinions on that thought. Thank you.

akastud

 

[whyun]

I would end the design at the connection of the glass block to the support only. Masonry portion would be designed for the out-of-plane seismic load from its own weight plus the tributary area of the glass blocks. I agree with the gist of what whir said.

Interpretations will vary and ultimately you need to go through the interpretation of your local building official.