WIND-RESISTANT DESIGN OF HIGH MAST STRUCTURES

Today, a large number of High Mast Structures (HMS) is being constructed around the world. Usually, the structural systems are presented as monotubular towers or masts with a mass at the tip which has utility equipment mounted. The monotubular configuration of an HMS has a large ratio of height to horizontal dimension. This means that the HMS is not only very slender, but also more wind-sensitive than any other common structures. Since failures of masts and monotubular towers or poles have occurred often, this confirms the necessity for a better understanding of wind-excited behaviour on the HMS, and also a better design for a wind-resistant HMS. This paper illustrates the basic theories of behaviors of along-wind response, and across-wind response. Prior to the present, design codes for HMSes have not been standardized. Therefore, this study has aimed to develop a suitable criterion of Wind Resistant Design (WRD) for HMS. We wish to produce guidelines to be used when designing a wind-resistant HMS to counter wind-excited responses. This paper starts with a theoretical approach. Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) are reviewed and applied to the analytical development of the design criteria. Then, the design criteria and the procedure of WRD are established. And finally, a case study is presented for illustration. There are three major findings in this study. First, the results of the analysis of CFD show that when the polygon sides are more than 16, the total drag coefficient tends to the constant, which closes to leeward drag coefficient, and the windward coefficient tends to be zero. Second, it's recommended that an HMS had better adopt a gust effect factor, G, equal to 2.33 due to flexibility by geometric configuration and structural properties. Third, the total maximum response limitation of an HMS should be considered in across-wind analysis for WRD procedures.