Bridge Concept Design Using Heuristic Fuzzy Optimum Design and FEM

In this study the aim is to present results of bridge concept design using heuristic fuzzy optimum design and FEM. The bridge concept is chosen as the basic suspension type. The deck plate rests on four supports. The middle supports are towers with suspension cables to lift up the bridge plate for minimising its deflection and bending stresses. Mass distribution load and flutter loading act on the plate. Geometric design variables are topology and dimensions of cables and deck. Material variable options are low strength and high strength steel. Decision variables are based on design variables. The main ones are cost and safety factors. The total goal is maximization of the fuzzy satisfaction of the user on all decision variables. The same optimal geometry is obtained for both steel options giving nearly equal performance. The softer steel option is preferable due lower cost. The model and FEM results agree reasonably in stresses and deflections. The fuzzy model used is shown to be an extension of probabilistic models.