Asce 7-10 Corners

[loouman]

thread507-299861
I read this thread from ASCE 7-05 and it seems the answer was still up in the air concerning any definitive word from ASCE on the matter so im re-posting the question for ASCE 7-10.

Are Inside corners and valleys considered End Zones or Corner Zones?

 

[TXStructural]

Roof valleys would be different from inside corner walls, and if you are talking about parapets, it would be different, but the fluid dynamics analogy is valid.

Ends and corners get special treatment because of various considerations, like vortexes that form at edges. An inside corner of a wall (not near an end) would see positive stagnation pressure (same as center of a long wall), and no real potential for negative pressures greater than would be seen at the center of the same long wall.

On a roof, where air is flowing across the surface, a valley could result in an increase in air speed across the valley (same air has to travel a longer distance) resulting in a sudden decrease in pressure. This can result in increased uplift.