Proposed solutions

FIRST SOLUTION :

Adding a set of helical strakes on a stack

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Avantages
The helical strakes are breaking the vortex . This solution could be adopted on cylinder structure if the Scruton number is bigger than 8.
In some rare cases they provide the most economical solution.

Disavantages
Double the wind load on the upper 13 of the stack, increasing stack weight significantly.
Nearly always more expensive than a vibration damper.
Complex geometry make fabrication difficult.
Can interfere with other attachments ( ie.ladders,platforms, etc.).
Foundation and Anchor Bolts usually increase in size.
Do not work in the case of interfering stacks.
Some codes do not allow their use for Scruton Numbers< 8 (which cover most stacks with vibration issues).

Conclusion :
Only of interest for small stack with small diameters. In all other cases a solution with a damper proves to be more economical.

SECOND SOLUTION :

Installing a vibration Damper

Placing a damper is an elegant modern solution, which has no disadvantage. This solution is always cheaper than the solution with strakes, except on rare occasions when the stack is small and with a small diameter.

Different types of damper could be used. There is no universal damper :each one has its advantages and disadvantages. On the following pagesyou can see different types of dampers.On bridges, the phenomenon ismore complicated than on cylindrical slender structures and horizontaldampers, vertical dampers and sometimes rotation dampers could berequested.

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A vibration damper absorbs the energy due to the vibration and to make the vibration phenomena disappear.

There is no universal damper to solve all vibration problems. Case by case taking into account local conditions (acceleration, amplitude, frequency, space.) will advise you of a given type of damper. dampers are used to suppress horizontal or vertical vibrations. Torsion vibration problems may

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