AASHTO - Vortex Shedding Analysis Method
AASHTO - Vortex Shedding Analysis Method
(OP)
I am designing an aluminum truss type structure (see attachment) to resist vortex shedding in accordance with Section 11.7.2 - Vortex Shedding of AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, Fifth Edition, 2009. Any suggestions on how to apply this section to a truss type structure?






RE: AASHTO - Vortex Shedding Analysis Method
Dik
RE: AASHTO - Vortex Shedding Analysis Method
RE: AASHTO - Vortex Shedding Analysis Method
But if you want to check it......looking at this, it would appear you have all the variables you need (assuming you've done a dynamic analysis of the structure to get the natural frequencies) except one: the equivalent diameter of the bluff body as a whole [your "d" variable in Eq. 11-2]. Therefore, you would probably need to work up some numbers in the design wind velocity range (I assume we are talking from 0-90 mph here) to see what diameter (if any) would cause any unwanted excitation. I guess if it's between 16 and 3 inches you should be concerned.....but if you have issues, perhaps changing the stiffness (and ergo the frequency) would help. You would probably have issues with individual components (especially guy wires, if you have them) before the structure as a whole.
RE: AASHTO - Vortex Shedding Analysis Method
All that W bracing you put in to prevent buckling in the legs also serve to mitigate vortex shedding. It's like a 2-for-1 deal
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