CAD – integrated size and shape optimization of steel lattice energy transmission line towers using simulated annealing


Thesis Type: Doctorate

Institution Of The Thesis: Middle East Technical University, Faculty of Engineering, Department of Civil Engineering, Turkey

Approval Date: 2016

Thesis Language: English

Student: Serkan Şahin

Supervisor: OĞUZHAN HASANÇEBİ

Abstract:

Energy transmission grids have been undergoing drastic changes due to increasing energy demand throughout the world in the recent years. As a result of this trend, sufficient electricity should be transferred from production centers to consumption areas. Therefore, overhead transmission lines (OHTL) gain high importance to be designed on the land reliably and economically. A significant amount of overhead transmission lines is constituted by steel lattice towers. Transmission line towers serve to keep the conductors above the ground transferring electricity from the energy sources to the communities. The new conductor types, increased public awareness on aesthetics and environmental consciousness, and the need for higher capacity lines have resulted in great pressure on designers to develop economic and optimally designed towers. Additionally, optimization of transmission line towers is particularly important in the sense that these structures are designed once as either suspension or tension towers in several different types for each line, yet multitudes of them are erected along transmission lines extending to several hundreds of kilometers. Accordingly, even a small percentage of weight reduction vi that can be achieved in the design of a single tower may add up to hundreds or thousands of tons of material when the entire transmission line is considered. This thesis presents a new optimization tool for automated design of steel lattice transmission line towers in real-world engineering practice. This tool has been developed by integrating the simulated annealing (SA) optimization algorithm into the commercial PLS-Tower software to optimize steel lattice towers for minimum weight according to ASCE 10-97 (2000) design specification using both size and shape design variables. In this context, a novel two-phase SA algorithm is specifically developed and compared with a typical SA formulation in four weight minimization problems of real-world steel lattice towers for high voltage overhead transmission lines between 110 and 400 kV. The optimized designs and the CPU time required by the two SA variants are reported for each test problem and then compared with the currently available structural configurations resulting from a conventional design process in order to quantify material saving achieved through optimization. According to results, two-phase SA algorithm converges the optimum solution as good as SA does; however, it requires much less time to converge the optimum solution.