Fuzzy optimum model of semi-structural decision for bridge lectotype

In the process of concept design of bridges, it is necessary to select the best from feasible alternatives through comparison and filter. The criterion set, used to evaluate and select the satisfying alternative, consists of many qualitative and quantitative factors. Therefore, the selection is a problem of multi-criteria and semi-structural decision making. Different from traditional methods in semi-structural decision making, a new framework and methodology is presented in this paper for evaluation of bridge alternatives. First the criterion set is established for the evaluation of alternatives. Next, the approach is studied to construct the relative membership degree matrix, in which both qualitative and quantitative factors are consistent with the uniform calculating standard. Then a new weight-assessing method is developed for calculation of the weights based on the relative membership degree matrix. Finally, a fuzzy optimum model is adopted to select the satisfying bridge alternative. Finally a case study is given to show the efficiency and robustness of the new framework and methodology.