Optimization of Truss Girders in Cable-Supported Bridges including Stability

The main design principles for girders in cable-supported bridges have not changed significantly over the past 60 years, and are limited in further development. The design concept suffers from substantial fatigue issues, and will be challenged by self-weight in future very-long bridges with main spans beyond 2 km. In this work, truss topology optimization, including global and local stability, is applied in a conceptual study of new weight-reduced designs for girders in cable-supported bridges. The methods are based on finite-element limit analysis and convex optimization. A single section of a continuous girder, subject to local and global loads, is optimized to minimize weight while fulfilling constraints on stresses as well as global and local stability. The optimized designs, significantly different in layout from the conventional, show initial weight savings of up to 45% compared with the present design. Further parameter studies indicate potential weight savings of up to 54%.