Fatigue reliability analysis of microwave antenna towers due to wind

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 Palm gren-Miner's rule to continuous random process is adopted for computing ann ual 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 c ycles of stress ranges over the design life period of the structure is assu med to follow a Weibull distribution. In the second approach, the first-ord er second-moment (FOSM) procedure is used. A 75 m tall antenna tower is con sidered as an illustrative example. The fatigue reliabilities obtained by t he two different approaches are compared for a set of important parametric variations. Also, fatigue reliabilities determined by assuming different ty pes of the distribution of responses are compared. Results of the study sho w that a Gaussian distribution provides the lowest estimate of the probabil ity of fatigue failure. The probability of failure computed by the FOSM met hod is greater than that computed by the full distribution method. Paramete rs governing the wind characteristics at the site have significant influenc e on the probability of fatigue failure.