Earthquake amplification factors for self-supporting telecommunication towers
In the absence of specific guidelines for the seismic analysis of self-supporting telecommunication towers, designers may be tempted to apply building-code approaches to these structures. However, these towers respond to earthquakes in a different fashion than shear buildings. In this study, earthquake amplification factors for the base shear and the total vertical reaction of self-supporting latticed telecommunication towers are suggested based on modal superposition analysis performed on 10 existing towers, each being subjected to a set of strong-motion accelerograms acting in the horizontal and the vertical directions separately. Results are presented in detail for two of the towers studied, with heights of 66 and 121 m, respectively. Simple regression analyses are performed on the results from which the base shear and vertical reaction amplification factors are found. These factors are presented as functions of the tower's largest flexural period or largest axial period of vibration as appropriate, and can be used by designers to estimate the expected level of dynamic forces developed in self-supporting telecommunication towers due to an earthquake.Key words: dynamic analysis, lattice towers, base shear, vertical reaction.