Steel Stack Design

[SVaughn]

Hi all,

I am attempting to design an unlined steel stack that is 87.67' tall and has an outside diameter of 4.37' with a wall thickness of 1/4". The stack is braced latterally at three points. Please see the attached screenshot for clarity. I am trying to design it through the use of the Structural Engineering Handbook by Edwin Gaylord Jr. and the ASME STS-1-2006 Steel Stacks standard. Neither of these references go into detail on how to design a stack braced at multiple points. Does anyboday have any experience with this and how to deal with vortex shedding and ovaling for braced stacks? Any and all help would be greatly appreciated.

Thanks,
Shaylon

 

[fegenbush]

Vortex shedding is usually handled by helical strakes. I have also seen straight strakes laid out in a step pattern. It is my understanding that the design of them is something of a black art, but if someone has a reference, I would be interested in hearing about it. I have been able to ascertain that they are triple-start and approximately 45° inclination from observation of others work.