Wind Loads Generation on Symmetrical Building

[jneves1990]

Dear friends,

I've recently tried to use the automatic wind loads generation RSA 2015 provides. I've now created a simple model to see if the pressure is according to the values provided in the Eurocode. 

This building is symmetrical in both X and Y axes and so symmetrical wind loads should be expected.

The problem is, as you can see in the attachments, these loads are not strickly symmetrical. Why is that? Note that given the geometry, I've only considered X+ and Y+ direction.

[StefanoPasquini6790]

Hi,

Do you have generated the automatic load over the claddings with automatic wind load generation? If yes, do you have compared the load values? Do you tried to run two different anakysis??

Waiting for your answers

[jneves1990]

Hey Stefano,

Indeed I did, I did and I did.

The maps being different for both sides of the building, create different load values. I picked 3 claddings from the façade hit perpendicularly by the Wind (X+) [1st attachment] and the compared its values [2nd attachment] and as you can see they differ. I'm completely aware that the differences are minimal but my concern is why isn't it symmetrical?

Thanks in advance,

João Neves

[StefanoPasquini6790]

Hi João,

Can you send your model to the forum? Send also the wind settings (speed and wind profile).

I will test your model also in a CFD simulation to evaluate the real difference.

Greetings

[jneves1990]

Stefano,

Please find attached the structural model. 

Regarding the wind properties, I assumed a peak pressure of 1.09 KPa to check if it was according to the Eurocode.

As said before, given the geometry of the building only X+ and Y+ should be considered.

[jneves1990]

Hey Stefano,

I haven't heard from you in a while. Any update regarding this issue?

Regards

[StefanoPasquini6790]

HI,

I'm running the CFD analysis, a little bit of patience....I'm not a product support and I have to insert the forum activity in the usual working time...really hard sometimes...

I've checked the dimensions of the wind tunnel in your model, see the picture below:

As you can see, there is a little NON simmetry in the wind tunnel that can justify the NON simmetry of the applied loads. As I told you before, I'm investigating in advanced CFD Analysis the compare the pressure value.

Be patient, greetings

[jneves1990]

Hey stefano,

Thank you for the support. I thought the CFD analysis could be briefer. Apparently, I was wrong.

From your picture I can assume that there is an offset of 5mm in the wind tunnel. What a shame, such tool could be a great asset to RSA.

Thanks once again, take your time!

Regards.

[Rafal.Gaweda]

Thank You Stefano for deep analysis 🙂
You may be right.
We will check WS algorithms.

[Rafal.Gaweda]

Soon:

[StefanoPasquini6790]

Hi Rafal, Joao.

My assumption is that Robot overstime the wind value in pressure as in depression. My brief and easy analysis show some comparison between Robot structural Analysis Professional and Autodesk Flow Design.

Starting from Joao model I've created, as he request, the X direction wind simulation finding a NON simmetrical pressure load distribution, as described in previous post, then I've created the same model in Autodesk Flow Design and set the same wind tunnel dimensions and wind speed.

Then, the results are shown in the next images.

Only one note, that can be also an idea to add in the wishlist. The CFD analysis don't take in count the effect of internal pressure (CPi). It could be a very poverful tool if it could be automatically created an uniform load pressure  (for example + and - 0.2) that can be automatically combined with the CFD pressure loads. So we can have three load combination for each wind direction: CFD, CFD+Cpi and CFD-CPi....tell me what do you think about it....

[jneves1990]

Dear Rafal, thank you for the support given.

Let me tell you that for low wind speeds (as 20m/s) the map pressure in RSA seems to be (near) symmetrical but once the speed increases, the differences are noticeable.

Please check it for the wind pressure I used, i.e., 1,09 kN/m2 ~ 41.76m/s

Regards.

Stefano, Your help was much appreciated. The conclusions of your brief analysis were enlightening.

Regards.

[Rafal.Gaweda · Accepted solution]

[jneves1990]

Hey Rafal,

How did you fix the problem? If I try to run this simualtion tpday on RSA 2015 will I get a symmetrical load pattern like the one you have shown? thanks in advance.

[Rafal.Gaweda]

Joao

In the my first post in this thread I wrote "soon".
And that's all I can tell you now.

[jneves1990]

Ha ok! 😉

Thank you very much, Rafal!

Keep up with the good work.

Regards

[Anonymous]

Hi. I have a similar question reagarding the wind load generation on RSA. Does anyone know why the pressure value on the figure shows higher pressure at the bottom? is it an accumulated value of the wind load generated? because i think highest wind pressure are experienced at the top of the structure. PLease.

[Rafal.Gaweda]

http://forums.autodesk.com/t5/robot-structural-analysis/wind-load-generation-pressure/td-p/6300691