Design of Horizontal Mullions For Gravity Load
Design of Horizontal Mullions For Gravity Load
(OP)
When designing a horizontal mullion for gravity load (which is typically the self weight of the glass pane above), is it typical to assume the glass spans to the end setting blocks?
Seems like a reasonable assumption. The glass pane will be very stiff so any deflection will cause the glass pane to span to the end supports (i.e. the setting blocks). Similar to our beam on beam discussion a few weeks back.
Thanks.
Seems like a reasonable assumption. The glass pane will be very stiff so any deflection will cause the glass pane to span to the end supports (i.e. the setting blocks). Similar to our beam on beam discussion a few weeks back.
Thanks.






RE: Design of Horizontal Mullions For Gravity Load
But right at the edges of a square/rectangle pane of glass, its movement of the edges of the glass will depend more on the seal itself: As soon as the rubber deforms - above and below the glass, you will start getting leaks at the edges.
RE: Design of Horizontal Mullions For Gravity Load
I think you’ve got the right idea. The mullions will be loaded primarily in shear, by the two point loads out near the ends of the mullion, near the stiles/jambs. The trick is to size the length, durometer (hardness) and locations of the setting blocks so as not to damage the glass due to these concentrated loads, and a slight amount of deflection of the mullion.
RE: Design of Horizontal Mullions For Gravity Load
RE: Design of Horizontal Mullions For Gravity Load
Also...why are you doing this? Storefront and curtain wall manufacturers have this down to a fine art. Is this a custom application or are you doing calcs for product approval by government agency.....just curious.
RE: Design of Horizontal Mullions For Gravity Load
I think in the past shop drawings were submitted for storefront / curtain walls but typically they are not required to be stamped and/or calcs are not requested. However now calcs are starting to be requested (or maybe they always have, I'm probably to green to know the situation). It seems as though the typical process is -> There are some drafters who provide drafting services to the curtain wall supplier. They create the shop drawings based on they desired system and designate "anchor by others". Then if calcs are requested the engineer comes along and provides calcs for member design and anchorage, in some sort of calculation report.
I was looking at two different submittal. One is 2 pages of calcs, the other was 85 pages. Funny how different we can approach things. The detailed calcs limited deflection to 1/8" or 1/4 the glass bite. However they applied point loads located at the end setting blocks. As we have discussed.
EIT
www.HowToEngineer.com
RE: Design of Horizontal Mullions For Gravity Load
http://math.ucr.edu/home/baez/physics/General/Glas...
RE: Design of Horizontal Mullions For Gravity Load
RE: Design of Horizontal Mullions For Gravity Load
Take the system designation and go into Florida's product approval search system and see if the system you have is approved. If so, you'll find links to the engineering backup.
Here's the link to the Florida Product Approval system....
Florida Product Approval
RE: Design of Horizontal Mullions For Gravity Load
@Hokie - good point. To clarify though, as part of the submital they designated that the location of the blocks and anchors. In this particular case they were (supposed) to be placed at 1/8 points.
EIT
www.HowToEngineer.com