Sections Optimization Design Of Truss Structure Based On Life Cycle Model And Improved Immune Genetic Algorithm

At present, when structure designers are doing optimization design, they only consider structure optimization of design phase and initial cost, and don't consider change of structure performance from design to failure and corresponding cost, but structure performance is descending during the structure's service time, and in some cases, the whole maintenance cost during it's service time can exceed initial cost. Thus, structure optimization design should aim to reach minimum life cycle cost with a view to the balance of design cost and maintenance cost during service time. As the paper's research object is truss structure, a simple life cycle optimization model for it is established.The genetic algorithm is a kind of searching method which simulates the natural evolution. It is simple and easy to implement, especially it doesn't need the special field knowledge, so it has been used in every broad fields. When GA are used in solving real engineering optimal problems, such disadvantages as premature convergence or weak ability of local search will occur.Based on the mechanism of such features as antigen recognition, variability of antibody and immune memory in immune systems, a new improved IGA, namely, Improved Immune Genetic Algorithm is presented in this thesis. In order to overcome premature convergence and find out optimal solution, the immune mechanism of creature is used in IIGA and antibodies will be promoted or restrained according to the computation result of affinity between antibodies, which reserves the excellent antibodies as well as guarantees the variability of antibody. A Direct Comparison method is proposed to cope with constraints, and crossover and mutation probability are adjusted adaptively, these two improvement further enhance searching efficiency and performance.By applying IIGA to life cycle optimization of truss structure with discrete design variables, it's proved that the IIGA possess good searching ability, it can solve this kind of problems excellently, and the practical results are satisfactory.