Deflection for members supporting glass

[palves]

Does anybody have good rules-of-thumb for member deflection limits when the member supports glass? I don't really see much direction on this in the code and have heard from others that they use more stringent criteria than L/360 when considering a sensitive material such as glass. Any ideas?

 

[Michel60]

Good morning palves,

If support is along an edge and is supporting the glass out-of-plane then deflection limits of L/175 are not unusual, refer to IBC 2403.3. If it's supporting the glass edge in-plane then deflection needs to be practically nil as seen by the glass and the connections need to be detailed appropriately to take up any support movement. As such the limit will be what can be accommodated in the selected attachment system and would likely be limited to a fixed dimensional value, say 1/2" across any two points of connection.

regards,
Michel

 

[msquared48]

You nail off the botom of a window, not the top and the gap is normaloly 1/4" to 1/2". So, I normally try to limit the deflection to 1/2" or less.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[steellion]

Curtainwall manufacturers can accommodate almost any reasonable deflection limit, but they will tell you they need "special" (read: more expensive) connections to accommodate deflections over 3/8".