Wind Actions and Responses of Steel Chimneys

Understanding some of the basic wind engineering concepts helps one understand the chimney’s response. The circular cross section of the steel chimney characteristically provides aerodynamic lift perpendicular to the wind direction. Knowing how to predict and prevent these adverse responses is of critical importance to steel chimney design. I. STATIC WIND FORCES The force exerted by wind varies with the wind speed and its associated turbulence. Turbulence is affected by metrological factors, temperature and terrain. An anemometer is used to measure the wind speed and its direction. Turbulence cannot be so easily measured but its effects must be considered. ATMOSPHERIC BOUNDARY LAYER Changes in temperature and pressure near the earth’s surface causes air to move across the earth’s surface. This movement exerts a horizontal drag force which retards the air flow. It is this force that we consider wind force. ANEMOMETER DATA A spinning anemometer magnetically induces a voltage that is proportional to the wind speed.