Across-wind response of tall circular chimneys to vortex shedding

• rms lift coefficient, CL,V approaches constant, and independent of Re number.
• Enhanced response under lock-in, through non-dimensional parameter ‘fact’.
• Closed form solution for normalized (σyDe) ; Base B.M. validated with ACI Code.
• Non-linear relation for ‘fact’ with (σyDe); verified using full-scale data.

A semi-empirical method for predicting across-wind response of a circular chimney due to vortex shedding during lock-in region was earlier presented by the author. This involved use of only structural damping, with suitable modification of spectrum of modal lift force through a parameter ‘fact’, having a value of 0.45. When applied to three typical chimneys, the predicted across-wind base bending moment values showed good comparison with ACI code ACI-307-2008. In this paper, by considering additional experimental data from Wootton, a non-linear relation between the parameter ‘fact’ and the normalized rms tip deflection, (σyDe) is presented. The relationship is also verified using full-scale chimney data by Galemann and Ruscheweyh, Waldeck, and Melbourne. The suggested method is simple and useful for design offices and appears equally applicable both for steel and concrete chimneys.