An Optimized Design of Network Arch Bridge Using Global Optimization Algorithm

An optimization approach of network arch bridges using a global optimization algorithm EVOP is presented in this paper. The objective is to minimize the cost of superstructure particularly arches and hangers of network arch bridge by optimizing the geometric shape, rise to span ratio, cross section of arch, and the number, arrangement and cross sectional dimensions of hangers. Constraints for design are formulated as per AASHTO, AISC and ACI Specifications. The minimum cost design problem is characterized by having a combination of continuous, discrete, and integer sets of design variables and is subjected to highly nonlinear, implicit and discontinuous constraints. An optimization algorithm, evolutionary operation (EVOP), is used that is capable of locating directly with high probability the global minimum without requiring information on gradient or sub-gradient of the objective function. EVOP is interfaced with finite element analysis software, ANSYS for evaluation of structural response of the bridge to verify the constraints and also to evaluate objective function. Within the range of design constant parameters considered, it is observed that 38% to 40% of total cost can be saved for circular and parabolic arches respectively, if design is optimized. Results also show that parabolic arch with optimum design variables is more economic than the optimized arch bridges with circular arch geometry.