DYNAMIC ANALYSIS OF TRANSMISSION LINE TOWERS

Abstract

The development of methods for the structural analysis and design of transmission line towers have received considerable attention in recent yea-rs. The rapid increase in the use of electrical energy necessitates the use of higher capacities of transmission line systems. This in turn requires the supporting towers to become heavier and consequently costlier. The economics of the situation have forced a review of cost and strength relationships of the tower. The dynamic response of transmission line towers is of serious concern to structural engineers because of the stringent requirements of safety and strength of the towers. This study deal-s with the dynamic response of transmission line towers to wind and earthquake forces. The codal provisions for calculating these two loadings have been reviewed. State-of-the-art procedures for the mathematical modeling of the towers and computation of the dynamic response o.f towers to time-dependent forces havebeen presented. A method has been presented for the digital simulation of realistic wind records taking into account the turbulence characteristics, frequency-energy content, temporal and -spatial correlations using stochastic processes. Although it is well established that earthquake forces do not govern the design of transmission line towers, an attempt has been made to quantitatively assess the response of the-towers to epicentral and strong motion earthquakes. Three sample towers have been considered and their free vibration oharactertstica have been determined analytically, The dynamic response of the three towers to simulated wind records and strong motion earthquakes have been computed and compared.