Multispan Sawtooth Roof - AS/NZS110.2 APP C

[Toby43]

Hi all,
I have a query regarding the appropriate selection of pressure coefficients from Table C2 in AS/NZS1170.2 APP C. (attached)
Do you sequentially take the roof pressure from the windward wall. I would do this, but

For example - 0 degree angle of attack
2Span Sawtooth Roof -- are the roof pressures B&D or B&X
3Span Sawtooth Roof -- are the roof pressure B,D,N or B,D,X or B,N,X

Basically I overthought it and came to the conclusion that the leeward roof (last roof span at leeward end of building) pressure would be related to the "X" nomination.
Any thoughts or experience on this greatly appreciated.
Cheers
Toby

 

[Toby43]

attachment

 

[Agent666]

I think I'd interpret it as the last span being X as well.

Then for two spans would be ABCXY.

For three spans would be ABCDMXY.

For four spans would be ABCDMNWXY

You'd only get the W after an N in the middle of a longer series of sawtooth as I interpret it.

Must admit its not that clear exactly how it's supposed to be interpreted, but the commentary give you the reference that it's based on which may provide some confirmation.

 

[Settingsun]

The Holmes book doesn't clarify this point.

I'd adopt the -0.5 (D & N) as it's not much more than -0.4 (X). If that makes or breaks the roof then it's in the danger zone given how rough these numbers are, and the comments below from a 1992 paper by Saathoff & Stathopoulos (Canadians).

You don't get the +0.2/+0.3 on the leeward span as there is no vertical M/W to cause it.