Optimal Design of H-Frame Transmission Poles for Earthquake Loading

The design of H-frame transmission poles subjected to static and dynamic loads (earthquake load) is formulated as an optimization problem. Time history analysis, discrete design variables, and optimization algorithms are integrated to solve the problem. With time history analysis, structural nonlinearity can be incorporated in the formulation; however, stress constraints based on ASCE design force the final design to remain elastic. Two cost functions are defined: Material cost and total initial cost. A method to treat time-dependent constraints is selected for use with two discrete variable optimization methods: Simulated annealing and genetic algorithm. A simple penalty function is defined to account for constraints in the algorithms. Several solution cases are defined and solved. Results show the genetic algorithm to be superior to simulated annealing. Both algorithms are quite simple and appropriate to solve discrete variable problems. Computational times with the methods are quite large because many alternate designs must be generated and analyzed. The use of parallel processors and reanalysis methods is important for practical applications of the methodology.