Reliability analysis of a microwave tower for fluctuating mean wind with directional effect

The reliability analysis of a 75 m tall steel lattice tower is presented fo r the annual variation of mean wind velocity taken as a function of both me an wind speed and direction. A parametric study is also conducted in order to investigate the effect of different important parameters on the componen t and system reliability of the tower. Variation of the mean wind velocity is determined from the continuous records of the hourly mean wind speed and the hourly mean values of the two components of the wind velocity. Annual probability of maximum response of a component of the tower exceeding a thr eshold level is determined as the mean number of crossing per day of the ve locity vector out of the safe resistance boundary surface defined as a func tion of mean wind speed and direction. Using the above method of analysis, reliability against allowable stress failure of critical members of the tow er and the consequent, system reliability are determined for a number of pa rametric variations. It is shown that the probability of failure of the tow er increases with the increase in the standard deviation of mean wind speed , the zero crossing rate and the correlation coefficient between the veloci ties in the two directions. Further, the variation of the probability of fa ilure is found to he sensitive to the variation of the above parameters in the lower range of the threshold levels of stresses. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.