Multicriteria fuzzy optimization of bridge systems

This paper applies a proposed an efficient, systematic and generalized multicriteria fuzzy optimum design method for. the structural systems, using the optimization concept, introduction of measure membership functions and fuzzy decision-making techniques [1-3]. Each objective function is suboptimized first for all discrete sets of common design variables and continuous design variables. In order to make the relative evaluation of suboptimized data of objective functions rationally and systematically, and involve the fuzziness or tolerance in the decision-making process and design emphases, the measure membership functions are introduced for all objective functions. The membership functions of the suboptimized objective functions are determined systematically using the corresponding measure membership functions as datum. A hybrid decision-making process is developed combining the weighted operator method, comparison process of maximum membership values and backward interpolation process for the determination of the global optimum solution. The weighted operator method can also involve the relative emphases of each objective function simply. A design example of a cable-stayed bridge system, in which the total cost and the aesthetic of the bridge system are the primary objectives.