Code Clarification - Wind Loading

[kevanthurman]

I have a 4 walled structure with the two walls in the transverse wind direction completely enclosed and no walls in the longitudinal direction aka it is completely open.

According to code nomeclature all walls have to be at least 80% open to be classified as an open stucture. Due to the geometry of the structure it is classified as an enclosed structure according to the code.

When analyzing the wind in the longitudinal direction would I apply the loads as if there were walls to get the base shear? Or should I only apply the wind loads to the columns and face of the roof beam (a 10" HSS)?

 

[TXStructural]

A 4-walled structure with only two walls? This sounds like a pole barn.
You have to apply wind in both orientations (and the oblique), and depending on the situation, you may end up with wall and roof wind similar to freestanding elements.
Look over the wind commentary in ASCE 7.

You would use partially-enclosed (as a minimum) when the wind is perpendicular to the walls, which means you apply a higher interior pressure. That pressure is based on the pressure at the opening (missing wall), so when the wind is on the face of the walls, use the factors for pressure on end walls to find the interior pressure (and apply the appropriate factor, something like 0.55 instead of 0.18).

The along-wind forces and oblique winds, wind going through the open end, would act similar to free-standing walls (and a lot like a wing) plus a free roof. Look at ASCE 7-10 Ch 29. As you note, you also need to look at the area of structural elements facing the wind.

Hope this helps.

 

[Den32]

Agree with TX Structural.

Wind direction perp to walls: Use partially enclosed structure, GCpi=0.55

Wind direction parallel to walls: Check as a Free standing roof Element/canopy (uplift will likely govern).