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Wind acceleration and frequency workflow

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Message 1 of 4
skellyRSA2023
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Wind acceleration and frequency workflow

Hi,

i have a typical concrete frame modelled in rsa. I understand that wind acceleration and frequency are a complex subject which i am currently tryng to learn about. Would there be a step by step workflow for finding the acceleration and frequency for a concrete frame or steel frame for that matter under wind loading? I.e. Modal analysis etc. Have reviewed some of the posts on the forum but they are difficult to follow and i would appreciate if i could get some guidance on a workflow on how to approach this calculation model for finding these values. Any help would be most appreciated.

Simon.

3 REPLIES 3
Message 2 of 4

Hi @skellyRSA2023 

Actually there is no possibility to simulate dynamic wind impact on structure in Robot Structural Analysis.

Wind simulation module takes into account only static wind pressure. caused by linear air flow over model geometry. No dynamic action is taken into account.

Wind and Snow load module (code load definition) is based on code regulation, where in most cases dynamic wind action is simulated by static load factors. Loads generated in that module does not take into account any dynamic structure action as well.

 

Loads variable in time can be simulated in harmonic analysis or time history analysis, but there are not any tools to use those analysis for wind simulation. While using harmonic and time history analysis loads and analysis parameters have to be defined manually.

 

 



Krzysztof Wasik
Message 3 of 4

Hi @skellyRSA2023 

Below you will find short description of using harmonic analysis for dynamic wind load simulation.

Robot will not help in load parameters definition (values, frequencies). They should be defined manually.

Maybe you will find this procedure useful

 

Divide wind action into two components:
  • mean value, defined as static load case.
  • variable (dynamic) load amplitude, defined as harmonic load. 
Then combine mean and dynamic wind action in load combination module. 

Follow the steps:
  1. Define structure and static loads and combinations.
  2. Define modal analysis to calculate normal modes and to activate harmonic analysis.
  3. Divide wind action in two components and define two separate load cases.
  • constant - mean wind pressure value.
  • variable (dynamic) wind action amplitude.
  1. Change load case type for variable load from static to harmonic and define variable wind action frequency.
  2. Define the following combinations:
  • static combinations + mean wind load + wind variable (harmonic load).
  • static combinations + mean wind load - wind variable (harmonic load).
  1. Verify structure for defined combinations.

Please refer to the following video Wind action with harmonic analysis in Robot

 



Krzysztof Wasik
Message 4 of 4

Thanks, Krzysztof  ill try this and see how I get on. 

 

Simon. 

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