End Connection Effects on Vortex Shedding Susceptibility of Welded Aluminum Truss Tubular Web Members

Abstract

A series of experiments and analyses have been conducted to assess the vulnerability of hollow circular web members in welded aluminum sign truss structures to wind-induced resonant vibrations. Results from nondestructive field testing were used to develop and verify a reliable method for determining the fundamental natural frequency of vibration for various categories of truss web members (incorporating end connection fixity effects). These natural frequencies for different types, sizes, and lengths of web members were then related to their computed vortex-shedding frequencies, toward estimating the critical wind speeds for web member resonant vibration. Outcomes were correlated with wind-related fatigue damage observed in the field; simple design recommendations for preventing this sort of damage by limiting the maximum web member slenderness ratio have been developed.