Multi-objective anti-optimization analysis of structures with genetic algorithm

In structure analysis we just consider either the maximum force acts in structure or the maximum displacement that structure happens, but it is not determined now that which one is the much adverse factor to make structure fail. While either the maximum force is much bigger or the maximum displacement excesses the allowed value, the structure will be fail. In the other hand, earthquake excitation includes two factors: the earth ground acceleration and the field frequency. If earth ground acceleration is big enough, the structure will suffer big force, while the structure's nature frequency is much close to the frequency of field, the worse response will happen. Genetic Algorithm (GA) is a kind of parallel search algorithm, so that it can be used in multi-objective optimization problem. In this paper the two factors are considered together, here the objective function includes: the ground acceleration and the field predominant period, the constrain condition includes: the maximum structural base shear and the maximum structural displacement. The genetic algorithm is used to search the worst earthquake excitation that acts in structures. The excitation includes the ground acceleration and the field's period that cause the structure happens the maximum shear, and the maximum displacement.