An efficient method for performing uncertainty analysis of transmission towers under skew winds with both yaw and tilt angles

Abstract

Serving as one key component of the most important lifeline infrastructure system, transmission towers are vulnerable to multiple nature hazards including strong wind. It has been demonstrated that uncertainty analysis of the tower under strong wind should be considered in practical engineering. This work proposes an effective method to perform uncertainty analysis of the transmission towers subjected to yaw wind only and both yaw and tilt winds. The proposed method takes into account, apart from other uncertain parameters, the uncertainties of both the yaw and tilt angles of the skew wind direction, leading thus to more realistic results, contrary to the usual uncertainty analysis procedures which take into account the uncertainty of wind direction in simplistic ways. Based on the analysis results, it was found that uncertain material properties have a greater impact on the tower capacity curves than uncertain section dimensions—specifically for towers exposed to yaw wind only, as well as those subjected to both yaw and tilt winds in the longitudinal and transverse directions. Additionally, tilt wind significantly influences tower behavior, especially when the tower is placed on hills and subjected to skew winds. This suggests that the tilt angle should be considered in the practical design of towers located on hills and exposed to skew winds, for safety reasons. Apart from the above, a new way of visualization of structural failure initiation probability is introduced in this study, which is the failure initiation diagram. The failure initiation diagram presents in a simplified and comprehensible way the probability of failure initiating at specific critical members or points of a structure. A detailed description of this novel type of diagram, along with its development for the transmission tower considered in this study is presented. In addition, some key ideas are mentioned for the importance and future development of the proposed failure initiation diagrams for various types of structures.