Topology optimization of wave barriers for railway induced vibrations in buildings

Abstract. In order to reduce environmental ground vibration due to railway traffic, mitigation measures at the source, the transmission path and the receiver can be applied. Mitigation measures on the transmission path are particularly appealing in situations with existing track and buildings. In this contribution, the optimal design of stiff wave barriers is considered. Up to now, wall barriers with a rectangular cross section have mostly been studied. However, current construction methods of wave barriers provide a wide flexibility in design geometry. Therefore further improvement is feasible. Topology optimization is used to discover novel, improved design geometries. Stiffer material is inserted into a design domain located between the source and a building. The objective is to minimize the amount of stiffer material in the design domain while satisfying the required vibration criteria in the building. The optimization problem is solved using a gradient based method and the adjoint method is used to enable an efficient calculation of the sensitivities. In this way, an optimal geometry is determined that considerably reduces the required amount of stiffer material. Topology optimized stiff wave barriers are therefore effective in reducing vibration levels, outperforming the rectangular wave barriers. The design contains, however, small features, making it sensitive to geometric imperfections, and a worst case robust optimization is applied. The resulting smaller sensitivity with respect to geometric imperfections also ensures that a posteriori design simplifications have a minimal impact on the barriers performance.

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