Optimization of steel-UHPC composite girder bridges for lightweight and eco-efficient design

Infrastructure construction demands fast and industrialized methods to deliver more sustainable and durable solutions. The application of composite structures using Ultra-High-Performance-Concrete (UHPC) emerges as a potential strategy to enhance structural efficiency, extend service life, reduce environmental impacts, and design lightweight structures. However, there is still a lack of studies applying automated optimization techniques to steel-Ultra-High-Performance-Concrete (UHPC) for those purposes. In bridge projects, the superstructure alone accounts for approximately 50% of carbon dioxide (CO₂) emissions during material supply, transport, and manufacturing. In this context, this study aims to replace an ordinary concrete slab with UHPC, and the composite section is optimized using heuristic optimization combined with a nonlinear finite element model. The optimization resulted in a weight reduction of up to 38% and a 4% smaller carbon footprint than the original section. Thus, the solutions will have an extended life cycle with a smaller carbon footprint, combined with an accelerated construction process due to more lightweight components.