Fatigue Reliability Analysis of Microwave Antenna Towers due to Wind

Abstract

A reliability analysis of antenna towers against cumulative fatigue damage failure is presented for the gustiness of wind. Fatigue damage is evaluated by the S-N curve approach using Palmgren-Miner's rule. Application of Palmgren-Miner's rule to continuous random process is adopted for computing annual damage assuming the distribution of response to follow several types of distribution processes. The reliability against fatigue damage failure is obtained using two approaches. In the first approach, the total number of cycles of stress ranges over the design life period of the structure is assumed to follow a Weibull distribution. In the second approach, the first-order second-moment (FOSM) procedure is used. A 75 m tall antenna tower is considered as an illustrative example. The fatigue reliabilities obtained by the two different approaches are compared for a set of important parametric variations. Also, fatigue reliabilities determined by assuming different types of the distribution of responses are compared. Results of the study show that a Gaussian distribution provides the lowest estimate of the probability of fatigue failure. The probability of failure computed by the FOSM method is greater than that computed by the full distribution method. Parameters governing the wind characteristics at the site have significant influence on the probability of fatigue failure.