Design of vibration reduction measures for railway traffic by means of topology optimization.

Vibrations and re-radiated noise in buildings due to railway traffic are a matter of growing environmental concern. This has necessitated the development of vibration mitigation measures at the source (railway track), on the transmission path, and at the receiver (building). Mitigation measures on the transmission path aim at impeding propagation of ground vibration from source to receiver and are particularly appealing in situations with existing track and buildings. Examples include open trenches, soft and stiff wave barriers, stiffening of subgrade under the track, and placement of heavy masses next to track. Because of the high computational costs of numerical simulations, mitigation measures on the transmission path are usually designed by trial and error. Only a limited number of relatively simple design geometries is explored, leaving much roomfor further improvement by fully exploiting flexibility in design geometry provided by construction methods presently in use. The aim of this PhD research is therefore to develop a methodology for optimizing the design of mitigation measures on the transmission path, taking into accounttechnological constraints of buildability as well as uncertainties related to construction and surrounding soil. A topology optimization approach, that seeks the most efficient distribution of a given amount of material in a specified design domain, will be adopted for finding innovative optimized solutions.