Wind Load Case According to ASCE7-10

[drasticxxxx]

Hello guys,
I have been reading a lot and asking my colleges in work as well regarding wind load pattern, so here I will explain my doubts, and please explain it to me as much as you can.

In ASCE 7-10
There are 4 case for wind load,
And if I want to think by my self
Case 1 equal 4 cases
Case3 equal 4 cases
Case 2 equal 8 cases
Case 4 equal 16 cases
This what I think, according to my understanding and in this situation the wind load will be applied on all face and all cases will be considered
For example let explain case 2 and why it is 8 cases
1.pwx +ex
2.pwx-ex
3.-pwx+ex
4.-pwx-ex
And another four cases for pyx


I think the 32 case will cover everything except the suction load for roof, which is not considered, the reason behind this as far as I know, that for concrete high rise building the suction is insignificant and not be considered like in steel structures (is this right??),bur maybe it will reverse the deflected shape in the rood slab(which I doubt)

Another thing case 3 which consist of four case take into consideration of sidewall pressures but not conservatively since leeward coefficient is 0,5 while side wall coefficient is 0.7, but I think who put the code found that those 4 case are almost representative for design am I right)

Now to my main question,
In etabs 2015 ,it allow you to make 12 case only which will not cover all case, and I asked my colleges in office and they told that generally in Dubai we take 24 case by creating 12 cases use 0 direction of wind load and 12 cases by using 90 degree in wind load (etabs 9.7 allow entering wind direction whilel etabs 15 will not give you that option), and here my problem start , I need to understand not memorize and do what others do, so what is right what is wrong and how can I do it in etabs.

Please help me in details, and if there is something still not clear, don’t hesitate to ask about it

Thank you all friends

 

[mike20793]

I believe you are correct in your understanding of the wind load cases and the number of total cases.

The external pressure coefficients for low rise buildings take into account the roof slope. These pressures are then applied to the vertical projection of the roof. I believe it is the same for high rise buildings.

Case 3 and Case 4 are really for wind blowing diagonally across the building, not perfectly normal to one of the building faces.

In response to your main question, I haven't used etabs for wind design enough to know the workaround for this problem. Usually when I'm in etabs, it's for high seismic projects and I'm not too worried about wind loads.

 

[drasticxxxx]

Thank you mike,

Please I am waiting for more discussion on the subject ,I am still confused!!!!!!!!

 

[wannabeSE]

1. 32 load cases sounds about right.
2. For case 3, Pwx and Pwy are windward forces while Plx and Ply are leeward forces. For MWFRS, side wall pressure acts outward and typically the two side walls will cancels each other out (side wall pressure needs to be considered in some structures such as those with a building separation).

 

[drasticxxxx]

Thanks

Ktootk and you add your comment please, it is so important to me to see your answer please.