Crosswind vibrations of steel stacks. - critical comparison between some recently proposed codes -

Abstract

The codification of vortex-excited oscillations of slender structures seems to be a still unsolved problem! This is shown by the comparison of three draft codes proposed recently: ISO-TC 98, CICIND and DIN 4133. The vortex-excited amplitudes calculated with these codes are compared with measured and observed amplitudes of full-scale stacks. For stacks with low structural damping parameters, typical for steel stacks, the differences between the calculated amplitudes are very large and can be regarded as unacceptable. While the amplitudes according to DIN 4133 are in rather good agreement with the observations, the CICIND recommendation gives amplitudes which are up to ninetimes higher (extremely large and uneconomic safty margin) and the ISO solution even tends to infinite values if the structural damping falls below a special value. More exact full-scale measurements should be undertaken in order to clarify this discrepancy.