Geometry Optimization of Space Structures with Dome Shape by Considering Buckling of Member and Variable Jonits Location by Using Gentic Alghorithm

Structural optimization in Civil Engineering is a designing technique that, besides controlling the technical behavior of the structure, should possess the minimum weight. A dome structure is one type that is so applicable in civil engineering purposes. In such structures with a constant span diameter and under a constant distributed loading, determining a minimum weight depends on the location of the joints and a portion of the load applied to each joint. One of the major drawbacks in optimization techniques is a possible convergence of the problem in a local region. Therefore, using a technique capable of overcoming this major problem could be crucial. Genetic Algorithm (GA), a method based on the nature, is a technique which has overcome this problem to some extent. In this research, the objective is to minimize the weight of dome structures with concern to the buckling of all the members, while the height of the layers may vary to its best location in Z direction. Obviously alteration of the joint location will cause a change on the amount of load applied to each joint in order to keep the total loading constant. Also in order to make the optimum shape practical, the new location of the joint will move in the xy plane to fit a parabolic function. Therefore, obtaining the best location of the joints with regard to the defined parabolic function could also be considered as a secondary objective of the paper. The proposed technique was then applied to a number of dome problems and also to a barrel vault. The results obtained were found to be very satisfactory.