Why?

[mijowe]

When I tell the curtain wall manufacture that my post composite deflections for perimeter beams will be l/600 or 1/2" max do they look at me surprised and wonder how they are going to deal with such a large deflection?

 

[CANPRO]

Maybe you should ask them if they would rather deal with L/360.

 

[PMR06]

I hope you look back at them and wonder if they are qualified to do the project...

 

[MiketheEngineer]

Agree w/ PMR06

If they don't understand - then they don't know what they are doing. But 1/600 should be OK - What is the rest of the building doing??

 

[steellion]

Deflections for the curtain wall system in excess of I believe 3/8" require them to detail it differently. It's likely not a matter that they can't, but rather they don't want to...

 

[msquared48]

Large deflection? You mean small deflection...

I agree that obviously they are not good enough.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[shobroco]

I think it's unanimous that your deflections are not the problem, your curtainwall guys are.

 

[LD81]

Steellion is correct, the typical joint thickness for CW can handle 3/8" max. But the concern is differential deflection between stories and your post-composite deflection most-likely includes dead loads that will be close to evening out on every floor. So you are mainly concerned about LL deflection.

 

[rapt]

The standard code deflection limits have never, in my experience, applied to glass curtain walls.

It has always been required for designers to check for the manufacturers requirements and they are always low, as it is more expensive to allow for greater deflections. In a competetive environment, they always quote on the cheapest alternative (for the curtain wall) to win the work, so the least deflection. There used to be one manufactirer in UK who required 0mm deflection. He did not win may contracts.

Larger deflection limits are possible but they cost a lot!