Wind Load Direction for Corner Mullion Condition 1

[Erudawn]

I am designing an aluminum corner mullion for a curtain wall system.

Conventional analysis for a typical wall mullion is to have two load combinations: Case 1: Positive (towards the wall) and Case 2: Negative (away from the wall) wind load
and check the stress and deflection for both cases.

For the case of a corner mullion, loads are now coming from two walls (usually perpendicular) and I was wondering about the load combinations I needed to apply:
Is it a valid assumption that the corner walls are either both positively or negatively loaded only,
or should I consider load cases wherein positive wind load is applied on one wall, negative on the other?

 

[Tomfh]

It’s not a valid assumption to assume loads are both positive or negative. Eg You can have windward wall positive and sidewall negative.

 

[Ron]

You also have to check for wind blowing directly at the corner and away from the corner that would give positive on both walls and negative on both walls.


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[trustthemodel]

Curtain wall manufacturers typically have engineers which will run quotes for certain jobs. They may be a good resource for the particular system you are looking at considering corner mullions can be odd shapes at odd angles. The same manufacturers also typically have loading tables which may include corner mullions. (although probably not)

However, I would imagine positive and negative pressures on both faces of the corner mullion would be possible for wind at an angle to the corner. You may be able to check something like a wind at a 45 degree to the corner and work out the force components for your mullion axes and compare them to forces from your other load cases to check if they control design.

One thing to keep in mind while you go through the mullion design: corner mullions typically have more stringent deflection criteria than typical verticals as the mullion could deflect and hit glazing in the panels parallel to your wind loading (for your positive wind pressures). Verifying this maximum deflection alone may be worth a call to your particular curtain wall manufacturer.