I know, I know lower cuttings looks pretty similar to Alien Engineers ship... damn it! I swear it was before Prometheus...hehehe :P

I believe you it was before Prometheus :)

Thank you for the image Angel. Looks great !!!

What we see here is result of a FEM deformation analysis in sap2000? Alessandro Gubinelli did this?

That analysis are useful to identify compression and traction areas, because the frame mesh that you need to design before must take care about that. It's faster to analyse meshes that lot of frames. That's because we made this meshes models and the Kangaroo model before the final frame model.

I see. Thank you for the reply Angel.

Can you tell what value for the wind load did you take ?

In this simplified model we take 1KN/m2 and applied only over to zones of maximum exposure index. I have some pictures showing these areas shaded, if you want I could sent to you ;). Our experience calculating wind loads with eurocode tells us that considering location an the height of the structure, 1KN/m2 was a really safe-side choose in this model.

In other skyscraper models we made a more "scientific" calculation because of the higher exposure index (and location data), the brace produced in the base, and the natural period of the global structure (quite higher than this stadium) ;)

Hope this answer your questions ;) You are a really curious guy :P

Actually I would be grateful if you could help me out with the calculation of the wind load according to EC. I got the EN 1991-1-4 standard (I think it is the newest one - from 2002.) and except for the domes there is no specific category for free formed roofs.

I started reading the EN 1991-1-4, parallel with this example of a two pitched roof wind load calculation. The problem emerged on the very start in the section EN 1991-1-4 4.2 where basic wind velocity values were calculated. In upper example they took 26 m/s for Aachen, Germany. Whereas European wind map shows only 5-11.5 m/s - differing for different types of terrain in that area.

Maybe you can send me some of your examples of wind value calculations?

If you think it is more appropriate to reply on this by email, than here is mine: issworld2000 [at] yahoo [dot] com.

Muchas gracias !

xD...man, wait, I'm not structure teacher. :P This is not a structures forum neither, and I'm not here to talk about how to calculate wind loads over free formed roofs ;). 

But, normally, when you have a free-form surface is better to make some CFD analysis if you want to be accurate. The code only gives you simple examples to solve simple problems (double pitch roofs, cylinders, etc...), if you want to go further you need more than the code examples ;) I'm sending to you a spreadsheet capture in PDF with the calculus of win over a variable section skyscraper. With that email I finish the structure lesson ;). Be kind, I'm sure than there in Serbia must be someone else who could help you with this. 

You are welcome ;)

Thank you Angel.

Actually the structural engineering codes are most applicable to "standard" buildings, primarily rectilinear.  Projects that deviate from this (including sports stadiums and footbridges) are more often than not tested in a wind tunnel to accurately predict loading wind loading actions.  CFD is still often not accurate enough (but can be used as an initial estimation to be confirmed in a wind tunnel).

If you want to dabble with wind CFD, I would recommend testing it with Vasari (given it's a AD lab preview and free).  Conceptual massing can be done in Revit (or using my IFC links from GH/Rhino).  The results are pretty credible from my experience, certainly for the purpose of study and research.

Also if you're in an applicable climate, snow drifts can be critical on roofs, influenced by simultaneous winds.  I believe this is still a very challenging prediction using CFD.

Hi Angel,

Xflow looks really impressive.  Do you have any contacts there?  I see it imports IGES which is good, but would be great to consider any direct link with GH (or indirect using IFC).

Thank you for such an nice reply Jon.

I did not know Vasari can calculate pressure on surfaces?

How did you get that initial value for the wind velocity, which you used to start the CFD analysis?

Hi Djordje,

Pressure is function of wind velocity, and Vasari does have options for plotting the pressure.

The site wind velocity is normally provided in the wind code, you mentioned some values you've seen in the european code.  This is derived from recorded statistics at local weather stations.

Note that there are several design values that can easily be confused, including 3 second gust speed or mean hourly wind.