BASE SHEAR AMPLIFICATION FACTORS FOR SELFSUPPORTING 4-LEGGED TELECOMMUNICATION TOWERS UNDER SEISMIC EXCITATIONS

Due to rapid advances and developments in the telecommunication industry, proper investigation into the seismic behavior of telecommunication towers has proven to be most essential. The researchers in their studies have considered the effects of earthquake induced loads mostly on the trussed steel towers of triangular cross sections. The main objective of this paper is to obtain an approximate relation that could help the designer in evaluating the seismic response of 4-legged self-supporting telecommunication towers by determining their corresponding ground motion base shear amplification factors. For this purpose, seven of the existing telecommunication towers in Iran with heights ranging from 42 to 117 meters are considered for a modal superposition analysis under the effect of 45 strong-motion earthquake accelerogram records. Only the horizontal components of these earthquake records have been taken into account. To obtain a relation that would cover a vast range of earthquake zoning, the records are selected such that both near-field and far-field effects are included in the analysis. The suggested relation is presented as a function of fundamental flexural period of tower, and can be applied by designers to approximate the tower base shears under seismic loadings.