Design of railway bridges considering life-cycle assessment

Abstract

The world is currently confronted with the challenge of preventing environmental degradation and resource depletion. To compare the environmental performance of two railway bridge designs, an Excel-based model was developed with implementing a simplified quantitative life-cycle assessment. The model covers the entire life cycle of the bridge, from raw material extraction to construction materials recycling and disposal. Various assumptions are made for selecting the relevant emissions and environmental impacts. A streamlined approach is applied to compare the environmental burden throughout the life cycle of the Banafjäl Railway Bridge. The bridge is a simply supported composite structure carrying one railway track. Two track alternatives are investigated: ballasted track and fixed track. The results show that the environmental impacts of the fixed track alternative are lower than those of the ballasted track alternative. From a sustainable development perspective, it appears that fixed track has a significant advantage as the overall environmental impact is reduced by up to 77%. The raw material phase is found to be decisive in the life cycle of both alternatives. The frequency of track replacement is identified as a key environmental parameter, because the extra environmental burden of traffic delay during bridge closure nearly overwhelmed the other life-cycle stages.