Solved: Wind load generation - Wind velocity/pressure?

skellyRSA2023 · ‎08-23-2019

Hi,

With regards wind load generation, which wind velocity/pressure would I enter into RSA as per the attached pdf (2 sheets)? i have read previous treads from @Rafal.Gaweda and @StefanoPasquini6790 in which downloaded the spreadsheet, however i am still not that clear on it and think i may be airing on the onerous side when entering the wind load. Based on EC1 would it be as follows:

1. Basic wind velocity Vb or basic wind pressure qb ? as per the attached pdf second page.

2. Point 1 above taking into account topography i.e. terrain category, Z etc.

3. Points 1 and 2 above including the shape of the structure, then dividing by the area face of the building to give a wind pressure which may be a bit onerous.

at present I use point 3 above, however this is quite onerous as I thought the whole point of the wind simulation was to generate the wind loads based on shape of the building and flow around its shape? I would appreciate some thoughts or advice on this, or even if someone had some examples of what they have assumed in the past it would be most appreciated.

Simon.

Krzysztof_Wasik · ‎08-27-2019

Hi @skellyRSA2023

Robot Structural Analysis wind simulation module uses CFD simulation method . It is numerical simulation of wind tunnel. This simulation is code independent

To connect this simulation with code conditions, velocity or pressure profile determined by code can be used.

In my opinion regarding EN-1991 conditions:

mean wind velocity profile determined in 4.3.1 can be used

or if short therm velocity fluctuations should be taken into account

peak velocity pressure profile determined in 4.5 can be used

Structure shape influence (pressure distribution) is determined while simulation

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.

.

Krzysztof Wasik

StefanoPasquini6790 · ‎08-29-2019

Dear @skellyRSA2023 ,

As @Krzysztof_Wasik said (perfectly), Robot it has inside a CFD engine and not a design code wind load generator (it has but not for all codes and all structure type!).

I managed a lot to find the way to let converge those approach, in a safe way. I reported the workflow in this thread: https://forums.autodesk.com/t5/robot-structural-analysis-forum/terrain-type-wind-simulation/td-p/523...

I always use "pressure" as parameter and I've made a spreadsheet that create the wind pressure curve scaled at the top value, referred to the wind tunnel height.

So, the steps are this:

Define your site parameters, dependent by design code, zone...and so on;
Calculate the wind pressure on top of the wind tunnel height dimension, as shown in the following picture (the wind tunnel Height dimension depend by the dimensions of the structure, usually I use to set the height in about 2 times the building height)

;
set the pressure value in Robot at the value that you've defined at the top height (as told in the point 2.)
Run the analysis

Let me know if you understood the process

PasProStudio

www.pasquiniprogetti.eu

Structural + Detailing engineers

skellyRSA2023 · ‎09-01-2019

Guys many thanks for the explanation and apologies for the late reply @StefanoPasquini6790 @Krzysztof_Wasik .

Just so I understand clearly from what I understand basically input the peak velocity pressures as per what is highlighted in the attached document and set the wind tunnel height to say 2 * the height of the structure. is there any issue setting the maximum peak pressure as say the maximum value (1.3kN/m2 as per the attached calculation) and not having to interfere with the pressure curve at all and keep that straight?

Simon.

Anonymous · ‎09-02-2019

I am more of a wind velocity guy because the code that I use, ASCE, uses wind velocity coefficients. This is just to be coherent with the code variables and equations.

Anonymous · ‎10-08-2020

Hi @Krzysztof_Wasik @skellyRSA2023 @StefanoPasquini6790
I was wondering if you guys 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.

Jacques-GRANGER · ‎10-23-2020

@ StefanoPasquini

This is another approach of convergence between the CFD RSA and the EC1-1-4, see here:

https://forums.autodesk.com/t5/robot-structural-analysis/simulateur-de-vent/m-p/6852223

Jacques-GRANGER · ‎10-23-2020

StefanoPasquini said
>" usually I use to set the height in about 2 times the building height "

Accuracy for your approach to calculate the tunnel height ( hT) of the RSA simulator.
If b or d < h then hT = 2.h
If b or d >= h then hT = 2,5.min {d;b}
With
h = height
d = length
b = width
of building
And hT the tunnel height of the RSA simulator

Wind load generation - Wind velocity/pressure?

Wind load generation - Wind velocity/pressure?

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