Torus shape variations and cuttings.

Comment

Comment by djordje on August 13, 2012 at 4:56pm

Ok, thank you once again for the help.

Comment by Jon Mirtschin on August 13, 2012 at 11:02am

I don't have the eurocodes at hand, and it's a few years since I did these calculations now.  Different wind codes use different values, or different speeds for different considerations.

It depends on the response to wind you are considering (cladding design pressure, building overturning moment, accelerations/occupant perception etc etc).

This is described in the codes, I was merely trying to propose a reason you noticed a discrepancy in the wind speeds.

Comment by djordje on August 11, 2012 at 11:05am

So which one do you use as an initial one? Not 3 second gust, not mean hourly? But?

Comment by Jon Mirtschin on August 11, 2012 at 9:05am

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.

Comment by djordje on August 11, 2012 at 8:13am

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?

Comment by Ángel Linares on August 11, 2012 at 4:41am

No, I haven't :(

Comment by Jon Mirtschin on August 11, 2012 at 2:46am

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).

Comment by Ángel Linares on August 11, 2012 at 2:18am

Of course, this project was only made for study and research purposes. Jon is totally right about wind tunnel analysis and cfd. Jon, have you seen the new cfd from NextLimit people? http://www.xflow-cfd.com/

Comment by Jon Mirtschin on August 11, 2012 at 12:40am

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.

Comment by djordje on August 10, 2012 at 6:56pm

Thank you Angel.

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