ASCE 7-05 "Least Horizontal Dimension"

[bar7h]

The ASCE 7 defines edge and corner zones "a" as 10% of the least horizontal dimension or 0.4h, whichever is smaller...

How do you all define "least horizontal dimension" when the building isn't a box, but irregular with several different wings or roof sections. I typically take the least horizontal dimension of the particular section of roof in question, but is that the correct approach? Your thoughts? Thanks.

 

[fegenbush]

I interpret the spirit of the code as to provide a minimum edge and corner distance (... but not less than either 4% of least horizontal dimension dimension or 3 ft). If your reduced horizontal dimension from the complex design becomes unconservative, the 4% or 3 ft limit will control and keep you in line. I don't see a problem with the way your approach.

 

[JAE]

The ASCE 7 wind design method is based on generalized "boxes". When you have a building with wings and smaller appendages extending out from it you have to use your engineering judgement to find an equivalent "box" shape that would approximate the wind behavior.

This can be difficult to do as we engineers don't have any intuitive sense of how wind actually behaves but using a general box dimension of the overall building (and ignoring the little wing widths) would be conservative as it would maximize the "a" distance where the higher corner forces occur.

 

[bar7h]

Thank you for your input.