A STUDY ON WIND INDUCED VIBRATION ON LIGHTING POLES

Abstract

This study was under taken to understand the failures of slender flexible street pole structures under dynamic excitation due to wind loads. It also focuses on the most plausible collapse cause for the failure of the poles. Highway lighting poles as slender flexible structures with low-level of inherent damping undergo wind-induced vibrations. Two different types of steel pole sections have been considered in this study, viz. one with a single horizontal arm and luminaire, called the single luminaire and the other with two horizontal arms and luminaires known as the double luminaire both with a tapering hollow circular section. The models have been analyzed using SAP2000 by adopting the finite element method. The poles have been analyzed for equivalent static force considering the gust effect factor and wind load has been calculated based on three codes of reference namely AASHTO CODE, UBC CODE and IS 875 CODE. Wind gusts are the extremes of the turbulent, stochastic wind field. Most of the lighting poles sway under gust and are subjected to fatigue cracking due to wind induced harmonic resonance of the lighting pole. This causes failure at the junction between base plate and the lighting pole .In order to better understand the interaction of the pole structures with wind forces, it is beneficial to have a graphical representation of the problem. The deflection at the tip of poles has been compared with different codes to gauge the performance of the poles.