Wind effects on four steel stacks in square arrangement

摘要

The across-wind loads on structures having a circular cross-section, such as chimneys or stacks, have the potential to exceed the along-wind loads due to the aerodynamic phenomenon of vortex shedding. Unlike sharp-edged bluff bodies, where wind tunnel testing can provide a direct evaluation of wind load representative of those on the prototype, the interpretation of measurements for circular or rounded structures is more involved due to the presence of Reynolds number effects. Wind tunnel testing was carried out to evaluate the responses of four steel stacks in a square arrangement. Four aeroelastic models were constructed, characterized by a length scale of 1:90 and a frequency scale of 10.7:1. Stacks in arrangements are known to be susceptible to aerodynamic instability, including increased vortex shedding response or interference galloping. A test on an isolated stack was first carried out, which provided baseline measurements of the mean and peak responses. Wind tunnel tests were then performed for the four stacks in square arrangement over a range of wind speed and direction; the response of each stack in the arrangement was measured simultaneously. Two levels of structural damping were investigated. Mean and peak resultant base moments for each stack are presented as a function of wind speed and direction, and as a ratio to that measured for the isolated stack. The effect of stack position within the arrangement is discussed for the mean and peak resultant base moments. It was found that the peak responses of the stacks in the arrangement exceed that for the isolated stack at many wind directions. The effects of aerodynamic instability can be mitigated by increasing the level of structural damping.