Optimization of Pratt Steel Trusses by a Genetic Algorithm under Moving load Load Considering the Buckling of the Members

The cost of construction is one of the influencing factors in the design of various structures, and the structure can be designed in such a way that with the same construction cost, it has a better performance against the incoming loads. Various methods for optimal design of structures such as genetic algorithm, biological growth and evolutionary algorithms have appeared. The ability of these methods to find the optimal design of structures is much more than mathematical methods.In this research, using the genetic method, the geometric characteristics and height of a two-dimensional Pratt type truss have been improved to make the design more economical. This truss is designed under the concentrated force in the critical position in such a way that with the minimum amount of steel consumption, the maximum stresses in the members do not exceed the limit value. Then this force is considered in a mobile form along the entire length of the truss and its optimal design has been done with the objective function expressed.Finally, the results of two problems are compared. The results show that with the number of about  17000 calls of the objective function during 50 generations, the results lead to a suitable accuracy and the optimal height of the truss in the fixed load mode is equal to 2.53 meters and the moving load mode is 2.56 meters, which for each Two cases are about 50% of the length of each opening. Also, in the case of moving load, the weight of the optimized truss was about 36% more than that of fixed load.