Stack with Strakes (API design)

[PSSC]

I have posted this in the API forum and did get a good response, but I was hoping to get more inputs if possible.

I completed the API stack vibration calculations.
Adding strakes seems to be the easiest solution to get the critical wind velocities above 60 mph.
After recalculating the area for wind forces, and increasing the shell thickness to accomodate the new forces.
I then rechecked the critical wind velocity with the new average diameter with the strakes included and new "I".
The new frequency and velocities check out.
I guess my question is, am I done?
The code doesn't really say what to do, it only says to add strakes.
I assumed that you should recheck it with the new average diameter.

If I am missing something I would greatly appreciate some guidance.

Thanks in advance.

 

[weab]

Maybe I just don't quite understand your explanation, but I think you did too much. It's been a while since I had to do this so maybe there is more to it.

Check your stack for wind, add strakes if necessary, check new wind load for slightly larger diameter if you feel necessary, then thicken the wall if necessary. Done. No need to recheck for a new diameter because you have the same diameter, just slightly more wind area due to the strakes.

Arguably, I'd say that properly designed strakes add so little to the wind area in elevation that recalculation is not necessary.

 

[PSSC]

You may be right.
I was of two minds on this.
1) The strakes distrupt the vortex shedding and make the vibration calc unnecessary and not even valid.
2) The strakes are to increase the average diameter and if you don't redo the calc's how do you know the new diameter is adequate.
I just wasn't sure which one was the case.

Thanks,