Wind Diaphragm for inclined floor

[Bao Thanh]

Hi Everyone.
Please help and many thanks in advance.
I am doing with assigning auto wind load by diaphragm into an inclined floor - slope is about 7 degrees.
If I let Sap2000 auto assign the height for diaphragm (diaphragm 1-2-3 for floors, diaphragms 4-5-6-7-8-9 for roofs), it is not very true because the wind load will be Maximum at the lowest level, because the height distribution is Max at the lowest diaphragm.
Then I defined the height of each diaphragm by myself, the results seems more correct and after verifying between the Analysis and the Design, all member is Pass the check.
However, when I deleted the diaphragms 4 to diaphragm 9 (for the roofs), a lot of frames is Over-Stress by loads combination 2 (this load combinations does not include Wind Load)

My question is
- Why when let the Sap2000 auto assign the height for diaphragm, it seems not correct as for a Vertical Tower as usual.
- When I defined the height of distribution for each diaphragm, is that correct?
- Why when I delete the diaphragms for roof, some members are over stress by load combination 2.
Please check the attachment for details.
Thanh.

 

[Bao Thanh]

Here is the file after I deleted the diaphragm 4-5-6-7-8-9 for Roofs and some of members are Over-Stress
Thank you.