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Dynamic behavior of stacks


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Solution 1

The use of helical strakes over a part of the chimney where the wind effects the stack.  
Positive for strakes is there will be no maintenance or malfunction of the system.

Negative side effect is the chimney is due to the strakes effected on a larger projected wind area, which leads to larger forces in bolts and foundation. Not every vortex shedding can be eliminated with stacks, second order or third order effects are nor eliminated.

Solution 2

The use of a tuned mechanical damping system. (for e.g. picture) Mechanical systems can be active or passive. Active means the system is starting on its own to react on cross wind movement. For chimneys this system is not common while some movement will not damage the chimney.

Passive means the system is activated after the deflection.

The most common system we use is a pendulum system with hydraulic shock absorbers. Almost every situation can be handled with a hydraulic shock absorber system.

Negative side effect is the systems will need maintenance and check- ups. At least every 5 year an inspection have to done.

If we design a chimney we fit the damping system in a location where it can be reached, so maintenance costs can be limited.


All spare parts are on stock, so there won't be a panic situstion with a not to stop chimney.