Wind Enclosure - Special Case

[OzarkEngr]

Consider a square building with a full open endwall and sidewall, while the opposite endwall and sidewall are fully enclosed with no openings. These two enclosed walls form an L-shape. Per ASCE7, when using the formulas you will get this building to be 'Enclosed' or 'Partially-Open' with the newest ASCE7 and have a GCpi of ±0.18.

What about when the wind comes in from the 45° quadrant, where both of the open walls receive positive wind pressure simultaneously and the two enclosed walls catch this wind? I have always designed this case as partially-enclosed (GCpi of ±0.55), but have been wondering if this is overly conservative. The wind pressures to the enclosed walls would be at an angle, which reduces the normal pressure, but the increased GCpi would still create more wind than an Enclosed category with normal wind direction.

Thank you.

 

[ANE91]

For this particular scenario (square), A_o = A_oi (or slightly less), so you end up with partially open.

Were the same building more of a rectangle, then you could end up with a scenario wherein wind incident on the open corner resolves into smaller, vector-component q_hs normal to the open walls, and the q_h associated with the longer open wall is amplified for the partially-enclosed condition. So -C_p combined with +C_pi on the opposite wall (i.e., the “real” wall) is critical. I don’t see how this could be worse than wind normal to the longer open wall, which is how this problem is usually approached.

Are you treating the reentrant corner as an exterior surface? The open walls still have posts and define the exterior “surface,” even in the absence of any actual framing (e.g., roof cantilever).