Seismic sensitivity indicators for tall guyed telecommunication towers

Very tall towers are a fundamental component of post-disaster communication systems and their protection during a severe earthquake is of high priority. In North America, there are no simple rules to evaluate the seismic sensitivity of guyed masts, and very limited attention has been paid to the seismic behaviour of such structures to date. Since guyed towers may exhibit significant geometric nonlinearities, their detailed nonlinear seismic analysis is complex and time-consuming. In addition, climatic loads such as wind and ice are likely to govern their design in most cases. As a result, earthquake effects are often ignored or improperly evaluated. The objective of this paper is to propose some seismic sensitivity indicators for tall guyed masts, which would help tower designers decide whether seismic effects are important and whether detailed dynamic analysis of the structure is required. The indicators proposed relate to the maximum base shear and the dynamic component of the axial force in the mast and guy cable tensions. A conceptual model is also presented to explain the distribution of earthquake effects along tower elevation. The study is based on detailed nonlinear seismic analyses of eight existing guyed telecommunication towers with heights varying from 150 to 607 m.