Development of Structure Optimal Design Software: Applications in Cable-Stayed Bridge Design

Because of the aesthetic appeal, ease of erection, efficient utilization of materials, economical in long span bridges, and other countless advantages, cable-stayed bridges have found wide applications all over the world in recent 50 years. However, the design of cable-stayed bridge is very complex due to its three major structural components, stay-cables, girder, and pylon, are tightly coupled, which makes the structural system highly statically indeterminate. Design of such complex structure with a large number of design variables and constraints with traditional methods is inevitably time consuming and cannot guarantee the optimality of the final design. As a result, bridge engineers around the world are craving a methodology that is capable of solving the optimal configuration of cable-stayed bridges.
In this research, a flexible software framework that integrates commercial structural analysis software and optimization algorithms with a multi-level optimization scheme is proposed for generalizing the structural information to a unified mathematical model that is applicable for any mathematical optimization algorithms and solving multi-objective optimization problems. Based on the proposed framework, a powerful software named “Structure Optimal Design Interface with Unified Mathematical Model” (SODIUMM), has been developed to solve various structure optimal design problems.
Representative structural optimization problems and post-tensioning cable force optimization problems have been tested and validated to ensure the accuracy and efficiency of the SODIUMM. Those abundant optimization problems also reflect the flexibility of the software framework and the SODIUMM. Moreover, crucial design parameters are studied among 23 representative cable-stayed bridges in different classifications to provide practical design regions, which are used to examine the applicability of optimal solutions, and empirical design parameters. Standard cable-stayed bridge models for both single and double pylon configurations are proposed based on the empirical design parameters to demonstrate various optimal design schemes of cable-stayed bridges through bi-level optimization. Finally, from the optimal solutions of the standard cable-stayed bridge models, suggestions on specific bridges are made and general optimal values or conceptual guidelines are concluded in each respective design parameter.