FATIGUE ' ANALYSIS OF ANTENNA TOWERS DUE TO WIND GUSTS

Abstract

Fatigue damage over a period of time is invariably present in any structural system that is subjected to dynamic wind loads. Antenna towers are subjected to stress fluctuations under the influence of wind gusts and consequently fatigue failures occur in service conditions. The objective of present study is to assess the number of gusts to failure for the critical members of antenna towers due to wind gusts of varying durations. Fatigue analysis of two 24 m high antenna towers was carried out for wind gusts of durations ranging from 3 min to 25 min, in suburban and open terrain conditions. Palmgren-Miner linear damage rule along with the rainflow counting technique has been used to obtain the fatigue damage. The study indicates that the duration of wind gusts governs the number of gusts to failure of the towers. The study indicates that, terrain condition has significant influence on fatigue damage. It was noticed in the study that, the fatigue damage sustained in the members is significantly influenced by the member properties and the location of antennas. Also, the study indicates that the relationship between the number of gusts to failure and the duration of gust is non-linear.