Optimum Design of Transmission Towers Subjected to Wind and Earthquake Loading

Abstract

Transmission towers (1S2 and 2S2-132 kV types) subjected to multiple combinations of wind, seismic and dead loads are optimally designed for least weight. The member areas and joint coordinates are treated as design variables. Members are designed to satisfy stress limits. Joint coordinate variables are linked to reduce the number of independent design variables. The optimization problem is divided into two design spaces. While changing the coordinate variables, using Hooke and Jeeves method, the member areas are treated as dependent design variables. The sections used are: angle and pipe sections which represent the commonly used sections in lattice transmission towers, in addition to tube sections. The structural analysis and the fully stressed design are performed using STAAD pro v.2006. It is found that the 1S2 tower with angle section and X-bracing, under anti-cascade loading condition, has a reduction in weight of about 14% of the weight before optimization, while the reduction for 2S2 was 24% for the same conditions. For seismic loading conditions, the reductions were about 24% for 1S2 tower and 22% for 2S2 tower with angle section and X-bracing. The results showed that the 1S2 tower with pipe section has a weight of 85% of that with angle section, under the same loading condition, while for 2S2 tower, the weight with pipe section was about 88% of that with angle section.