ANALYSIS AND DESIGN OF MASTS AND TOWERS

摘要

For many years both guyed masts and self-supporting towers have been used for supporting antennas for broadcasting, mobile communication, etc. The choice between a mast and a tower has often been determined by tradition. However masts have clear advantages in the open country, whereas towers are more suitable in urban areas. Masts and towers are often situated on the top of hills and mountains, where the climate can be extreme with respect to wind load and in some cases atmospheric icing. Since the wind is turbulent, and the masts and towers are flexible and sensitive to dynamic load, the dynamic response becomes important in the analysis. However there are some differences in the analysis of masts and towers. The wind resistance for lattice sections is dependent on the type of members, the solidity of the sections, and for tubular members also dependent on the Reynolds number. Furthermore the latest research within the IASS Working Group for Masts and Towers has shown that the wind resistance of tubular sections is dependent on the turbulence of the wind. The masts act strongly non-linearly, as the forces in the guy ropes vary from slackened to a taut string. Over the years different methods have been used for analysing guyed masts, making the methods more and more realistic: starting with a gust factor method, over the IASS patch wind method to the Eurocode patch wind method, which gives results very similar to the results from a stochastic analysis.