Wind excitation of steel chimneys

This paper is intended to show how wind excitation is a major effect in the design of steel chimneys. The static behaviour is well covered by publications and Codes, but the same is not true of the dynamic behaviour. Accordingly, this is presented in a form that closely parallels static methods and combines with the static calculations to obtain overall values of amplitudes, stresses or deflections. Structurally sound approximations are given for values of the various parameters, which are within a few percent of 'exact'. The calculations obtain the aerodynamic forces acting on a chimney, the resulting amplitude of vibration, the dynamic stress, and an assessment of whether metal fatigue might cause difficulty. An example is included of a 80m-high chimney of 3.25 m diameter to show that the dynamic procedure is quite feasible for hand calculations in a standard design office.