Curved Roof Wind Loading

[Engineering05]

I have a question relating to the geometric expressions used in appendix C3 of AS1170.2 for buildings with curved roofs. I have a situation unlike those described in the illustrations of this appendix where my building is raised off the ground by a series of columns. Should I be adopting a value for 'h' (denoted as 'the average roof height') from the ground or from the soffit of my raised structure?

 

[Bagman2524]

ftp://law.resource.org/nz/ibr/as-nzs.1170.2.2011.pdf

It's the average height of the curved section above grade. I would add the distance from ground to be bottom of the columns when figuring your "h" height. Page 64 on the link.

“Faith is taking the first step even when you don’t see the whole staircase.” MLK

 

[Engineering05]

Awesome. I've run my numbers aginst both cases and it's obvious that taking 'h' from grade will be more conservative. Thanks for advice - it's my first time doing this calculation!

 

[ColinPearson]

For what it's worth, I've been dealing with the same thing over the past couple days and made the same decision - I included the height of my columns in 'h' because you're finding a coefficient that modifies the pressure from the wind which is based on velocity which as you well know increases with height above grade. You're also doing this to calculate the pressure on the roof itself; the condition of the framing/walls/columns/whatever underneath your roof does not seem to have any bearing on this.