Abstract
Modern railway tracks for high-speed traffic are often built based on a slab track design. A major disadvantage of slab track compared to conventional ballasted track is that the environmental impact of the construction is higher due to the significant amount of concrete required. In this paper, the dimensions of the rectangular cross-sections and the types of concrete used in slab tracks are optimised with the objective to minimise greenhouse gas emissions, while considering the constraint that the design must pass the static dimensioning analysis described in the European standard 16432-2. The optimised track design is also analysed using a three-dimensional (3D) model of vertical dynamic vehicle–track interaction, where the rails are modelled as Rayleigh–Timoshenko beams and the concrete parts are represented by quadratic shell elements. Wheel–rail contact forces and the time-variant stress field of the concrete parts are calculated using a complex-valued modal superposition for the finite element model of the track. For the studied traffic scenario, it is concluded that the thickness of the panel can be reduced compared to the optimised design from the standard without the risk of crack initiation due to the dynamic vehicle load. In parallel, a model of reinforced concrete is developed to predict crack widths, the bending stiffness of a cracked panel section and to assess in which situations the amount of steel reinforcement can be reduced. To reduce the environmental impact even further, there is potential for an extended geometry optimisation by excluding much of the concrete between the rails.
Highlights
Railway transportation is one of the most environmentally friendly transport modes
The objective of the optimisation was to minimise the environmental impact from the concrete parts while still fulfilling the requirements of the standard
The optimised dimensions were used as input to a 3D model of dynamic vehicle–track interaction
Summary
Railway transportation is one of the most environmentally friendly transport modes. a remaining environmental issue is the significant amount of greenhouse gas emissions generated by the construction of a railway track. The magnitude of stress intensity factors when considering a through-transverse crack in the roadbed was studied by Zhu et al [19] In their analysis, a simplified 3D model consisting of beam and plate elements was used to calculate the wheel–rail contact forces. Zi et al [26] developed a non-linear finite element model to study conical crack formations in concrete sleepers in a slab track system. By taking the dynamics of the track into account, novel recommendations for next-generation slab track structures are presented In these simulations, both cracked and uncracked sections of the concrete panel are considered, and the influence of cracks in the concrete panel on track responses at several operational scenarios is determined. The model of reinforced concrete is used to assess if the amount of steel reinforcement in the slab track design can be reduced, which may lead to additional carbon dioxide (CO2) savings
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