Wind simulation - wind velocity factor

[skellyRSA2023]

Hi,

i have some queries on the wind simulation tool in rsa. 

If i calculated a uniform wind pressure to eurocodes outside of the rsa program of say 1.35kN/m2 to be applied to the building, this i have then entered this pressure value into the wind simulation model in robot, if i assume a constant wind profile veloicity factor of 1.0 throughout the height of the building and the wind tunnel height (2 x building height) would this give me a constant pressure applied of 1.35kN/m2 on the face of the building? As the pressure varies in my model? 

How does the velocity factor actually work, does it multiply the applied wind pressure by the velocity factor in the wind profile throughout the height of the building, because when i increase this it seems to give less moment applied on my walls not increased? 

Also, if the wind pressure is applied over the face of the building by hand calculation based on eurocode wind pressure calculation, when the same pressure is applied in rsa wind simulation, the wind simulation gives me significantly less moments on my foundations, is there a reason for this?

thanks,

Simon. 

[Artur.Kosakowski]

Hi @Anonymous

I think you should check what final loads were generated marking the following attribute display on:

 

If it is a high building then you may want to divide its external walls into number of smaller panels rather than model them as single panels as the generated load is assumed as the average value from the pressure map on a given panel.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[skellyRSA2023 · Accepted solution]

Artur,

I have tried looking at this (see attached 9 snapshots on the pdf - with what was assumed), the force applied (based on wind in X-direction) seems to vary around the applied face of the building, the wind profile was constant at 1.0, however the panels which were highlighted seem to indicate all the panels for wind exposure? however does this make a difference if external openings have been assumed closed? if a constant pressure of 1.35kN/m2 is assumed, is it suppose to vary as it has? apologies if these are simple questions however I have not used the wind simulation before.

Thanks,

Simon.

[Artur.Kosakowski]

Hi @skellyRSA2023

Yes, the pressure generated by wind will vary depending on the location on a structure - constant wind speed doesn't mean uniform wind pressure on the entire structure (face). The CFD analysis considers openings as areas the wind can 'go through' to the inside of the building. As they usually are glass windows you should 'close' them with claddings.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[skellyRSA2023]

Thanks Artur, Ok then I have assumed correctly, that once the external claddings/wall panels with openings is noted as "closed" for wind exposure then if all the panels including the internal are highlighted it does not make a difference?

[Artur.Kosakowski]

Hi @skellyRSA2023

When all openings are closed the pressure map should be visible on the external walls only.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[skellyRSA2023]

thanks.

[gonzalo.grossmann]

Hello, I would like to know if any of you use the Robot wind simulator to comply with the standard (EN, ASCE) by the speed coefficient. What speed coefficient do you enter? Speed/pressure maximum or basic? 

or by introducing a maximum pressure coefficient, where 1 would be at the height of maximum pressure?

[haider.mumtaz]

Hi @Artur.Kosakowski 
I was wondering if you  can help me in loads generation when wind simulator is used. I have to model the tensile structure for car parking design. Now, it is in very windy area. The wind speed is 120 km/hr and to simplify my structure I have not used and cables rather bars with small diameters to support fabric. Now, when the wind is applied this tensile structure(cladding) in robot shows huge deformations, understandably as the wind is very high. Now, till which value does it continue to transmit the loads to the bars  and the structure below under wind loads? Is there any algorithm in robot? Or the deformations do not matter?
Should I use shell elements(slab with mm thickness) to imitate the effect of tensile structure and it will be always connected?
What is the best way to model the cables since, they will be used to support the tensile structure?
Thanks for your kind response. 

[Anonymous]

Hi everyone @Artur.Kosakowski @haider.mumtaz @skellyRSA2023 

What is the velocity factor in simulation wind load tools? and how I can determine it? Is it the topographic factor (Kzt) that exists in (ASCE 7-10)?