Stud Wall Check for out of plane wind loads 2

[medeek]

Up until now I have checked stud walls for axial and out of plane wind loading using MWFRS wind loads because I was of the understanding that when there is combined loading of a member (ie. axial and bending for a stud wall) one should use MWFRS instead of C&C wind loads.

Typical calcs for a stud wall look like the following link:

http://design.medeek.com/resources/framing/2014-2x6_STUDWALL.pdf

However, after reading through my recently purchased copy of "Guide to the Wind Load Provisions of ASCE 7-10" by Mehta and Coulbourne I've noticed that they are most often calculating wind loads for wall stud loads using C&C and not MWFRS.

Any enlightenment in this matter would be greatly appreciated.


Another related question that has been bugging me for a few days is why is there no C&C wind load diagram for hip roofs with θ > 27 degrees. I've seen many 12/12 pitch hip roofs so this omission seems very glaring to me.

 

[medeek]

Based on the paper provided by Rlewistx the correct way to analyze the stud wall would be to:

1) check gravity axial loads. D + L or D + (Lr or S) or D + .75L + .75(Lr or S)
2) Then check bending loads from wind only using C&C at the worst case scenario (zone 5), no axial loads.
3) Then a combined check of axial and wind loads using (MWFRS) wind loads.

What I am missing in my spreadsheet is the C&C bending only load case check (2), which as stated in the whitepaper, is often the controlling load case.

 

[medeek]

Here is an updated stud wall calculation with the missing C&C (bending only) wind load, specified as load case 2.

Updated Stud Wall Calculation

After giving it some thought about Load Case 3, I realized there is actually one more combined load case (D + W). Note that there is no 75% reduction in loads in this case. So to encompass this load case without having to insert yet another load case into the spreadsheet I decided to run the combined gravity and lateral load case all at 100%. This may be a bit conservative but it then ensures that I have covered myself for the D + W load case.

I also decided to use Zone 5 C&C so that I'm also conservative there as well. Note that in this particular case the C&C (bending only) load case governs as expected for a high wind location (155 mph ultimate wind speed).