Vibrations of Stacks Supported on Steel Structures

The effect of a flexible support foundation on stack vibrations due to vortex shedding is presented. Stacks considered dynamically stable if ground supported, would not necessarily be so if supported on steel structures. The lumped parameter method, shown to be adequate for ground-supported stacks, is applied in the determination of the frequencies of stacks supported by beams on top of steel structures. The flexibility of the stack supporting beams is considered in the determination of the influence coefficients. A numerical example is given for a particular stack showing that the frequency and resonant velocity for the stack is considerably reduced when the flexibility of the stack supporting beams in included. Approximate formulas are given for the determination of the minimum moments of inertia required for the stack supporting beams, considering stacks symmetrically supported on steel structures.