Development of wind vortex shedding coefficients for a multisided cylinder structure

Abstract

A major problem with high-mast light poles is the effects that wind vortex shedding can have on the pole itself because of the lock-in phenomenon. It is desired that the coefficients in the AASHTO Standard Specifications (<TEX>$5^{th}$</TEX> edition) for Structural Supports for Highway Signs, Luminaries, and Traffic Signals be analyzed and refined. This is for the belief that the span of the shapes of poles for which the coefficients are used is much too broad and a specific coefficient for each different shape is desired. The primary objective of this study is to develop wind vortex shedding coefficient for a multisided shape. To do that, an octagonal shape was used as the main focus since octagonal cross sectioned high-mast light poles are one of the most common shapes in service. For the needed data, many wind parameters, such as the static drag coefficient, the slope of aerodynamic lift coefficient, Strouhal number, the lock-in range of wind velocities producing vibrations, and variation of amplitude of vortex-induced vibration with Scruton number are needed. From wind tunnel experiments, aerodynamic parameters were obtained for an octagonal shape structure. Even though aerodynamic coefficients are known from past test results, they need to be refined by conducting further wind tunnel tests.