Fuzzy Optimal Design Of Grid Structure Based On Reliability

As a common form of large span space structures, grid structure is used widely in the field of construction engineering. With the span increasing, the conception of optimum design is introduced in the course of grid structure design, in order to decrease the cost of engineering project and vertical displacement. Among the existing optimum design models, majority only aim at the optimization which just in the definite conditions and ignore the fuzzy factors which exist in practice widely. Also during the course of optimum design, engineering reliability is often ignored and don't look upon it as a kind of constrain condition to restrict the design of grid structure. This paper lays the research emphases on the two aspects which were mentioned above.During the course of determination for grid structure optimum model, the tolerance coefficient value, which has great influence on optimum design, can be got by using the method of multi-level fuzzy optimum decision and the conception of tolerance coefficient. According to the correlated calculation method defined for grid structure, a fuzzy optimum design model is established in this paper. The result of an example, which used this model to make optimum design, shows a good economical index.The reliability index for grid structural members can be determined through using the method of fuzzy optimization after borrowing ideas from reliability index range for steel structure member and comprehensively analyze the damage characters of grid structure. The constraint of structural reliability index is introduced into the grid structure fuzzy optimum design. A model of fuzzy optimum design based on reliability is established to make grid structure has the coordination both in economic and safety.Through analyzing and comparing the three optimum results of the example from fuzzy optimization, definite optimization and fuzzy optimization based on reliability, it can be seen that grid structure fuzzy optimum design based on reliability is feasible and economic.