Along wind response of communication tower

Abstract

Presently, communication technology has become significantly important. The need for tall towers has been increasing with the requirements for effective communication, particularly for television, radio, GSM, and Internet traffic. Analysis and design of these dynamically sensitive towers are generally governed by the wind loads. Wind excitation induces fluctuating stresses in the members of the tower leading to fatigue damages of the members. In achieving safety with economy for construction, accurate determination of wind load is important. Design wind loads are calculated from the provisions given in the codes and standards. Communication towers subject to vibrations due to wind gusts, which are analyzed using the gust load factor method. This method gives an accurate estimation of wind response of the structure as it considers the resonant component of wind loads. In this paper, microwave lattice tower heights of 21, 30, and 50 m are considered and wind forces are determined using IS 875-1987, IS 875 (Draft), ASCE 7-2010, AS-NZS 1170.2-2011, and HK-2004 design codes and standards. These towers are analyzed for wind velocity of 39 m/s under terrain category-I, terrain category-II, and terrain category-III, and results are compared. It is observed that there is variation in the wind loads and this is primarily due to the difference in definition of wind field features in the compared codes and standards.