Insulated rail joints (IRJs) play a crucial role in modern railway systems. They serve the critical function of electrically isolating rail segments through the placement of an insulating material, known as an end plate, between two rail ends. This insulating material is necessary to define track segments, which makes it possible to determine the position of trains within the railway system. Knowing a train’s position is key to ensuring efficiency, reliability, and safety. While these joints are highly important, they are also vulnerable. The interruption in rail geometry results in a complex interaction between wheel and rail, giving rise to high dynamic impact forces. Traditional IRJs, or squared IRJs, have the cut between the rail ends orthogonal to the rail. In this thesis, an alternative design with a non-orthogonal junction angle is analyzed.

The primary goal of this thesis is to determine how the junction angle influences both the global wheel-rail interaction and the local contact pressure at the wheel-rail interface. To achieve this, the thesis is split into two parts: (1) the global wheel-rail interaction analysis, which studies the influence of the junction angle on the interaction between the wheel and rail using simplified geometries in a kinematic approach, and (2) a local wheel-rail interface analysis, which studies the effect of the junction angle on an assumed uniform contact pressure between wheel and rail.

The global analysis revealed the possibility of two distinct contact scenarios, depending on lateral wheel position and dip angles greater than zero. In contact scenario 1, the effective geometry and the resulting vertical impulse remained identical to those of squared joints. However, in contact scenario 2, the active geometry of the joint changes, leading to an increase in vertical impulse of the wheel’s center of mass. Additionally, the introduction of the junction angle increased the likelihood of less favorable contact conditions for contact scenario 1 and guaranteed less favorable contact conditions for contact scenario 2. The local analysis showed that uniform contact pressure between the wheel and rail increases slightly for non-orthogonal junction angles with dip angles near zero. For small junction angles (resulting in a long cut in the longitudinal direction), outside of the practical range, the rate of change of the contact pressure was greatly reduced.

The study has shown that insulated rail joints with non-orthogonal junction angles within the practical range do not provide significant improvements in dynamic performance compared to traditional squared joints. However, due to the assumptions made in this model, the complexity of the rail geometry was significantly simplified, and material elasticity was not considered. These limitations are expected to affect the contact behavior and could affect the results. This should be investigated further. The second model demonstrates that for junction angles within the practical range, the assumed uniform contact pressure increased slightly. However, for very small junction angles, which result in impractically elongated joints, the rate of change in uniform contact pressure can be greatly reduced.

Dit onderzoek richt zich op het verminderen van trillingshinder in CLT- en betongebouwen, zodat ze voldoen aan de richtlijnen en er meer naast het spoor gebouwd kan worden. De centrale vraag van het onderzoek is hoe specifieke ontwerpmaatregelen kunnen leiden tot een vermindering van trillingshinder in overeenstemming met de richtlijnen. Een voorspellingsmethode is ontwikkeld om trillingshinder te voorspellen op basis van trein-geïnduceerde trillingen, waarbij voorwaarden gesteld worden aan de trilling en het frequentiespectrum. Ontwerpmaatregelen zijn bepaald voor zowel CLT (variërende dikte, totale vloerdikte, overspanning, permanente belasting) als beton (variërende vloer- en wanddikte, overspanning, stramienconfiguraties, starre vloerverbindingen). Analyse toonde aan dat ontwerpmaatregelen met betrekking tot vloer- en wanddikte en overspanning het meeste effect hadden op de eigenfrequentie van de vloer. De methode omvatte ook het gebruik van een eindig elementen model voor dynamische analyses, waaronder een frequentieresponsanalyse en een lineaire tijdsafhankelijke analyse. De methode werd toegepast op een casus in Arnhem en vergeleken met de SBR richtlijn-B voor het bepalen van hinder voor personen in gebouwen gedurende de nachtperiode. De methode bleek effectief in het voorspellen van trillingshinder bij verschillende ontwerpmaatregelen, hoewel er een onderschatting was bij maatregelen met resonantiepieken rond 10 Hz en 12 Hz. Voor zowel het CLT-model als de betonmodellen waren vergroting van de overspanning en toepassing van doorlopende tussenwanden effectieve ontwerpmaatregelen om aan de richtlijnen te voldoen. Verder onderzoek op meerdere locaties wordt aanbevolen, waarbij het gebruik van een spectrum met de volledige frequentie-inhoud van trein-geïnduceerde trillingen wordt aanbevolen en het middelen van de frequentie-inhoud wordt afgeraden.

Wave barriers are a common mitigation measure when dealing with environmentally induced vibrations. These wave barriers generally consist of stiff vertical walls buried in the soil to impede waves on their path from the source to the receiver. The geometries of the wave barriers that are used in practice are very simple. More complex geometries have not often been considered as it is difficult to estimate which changes would increase the effectiveness.

In literature, topology optimization was explored as a method to design wave barriers. This method was applied while modelling the soil as a homogeneous elastic half-space. The resulting wave barriers showed a significant increase in the achieved vibration reduction. However, the designs were often very complex and hard to manufacture. In this thesis the method was improved by introducing a layered soil and by ensuring the manufacturability of the designed wave barriers.

The improved method was then applied to multiple situations in order to investigate aspects of wave barrier design and effectiveness. Optimization of a wave barrier for a two-layered soil model showed the significance of implementing a layered soil model. The interface between two layers resulted in reflections that could diminish the effectiveness of a wave barrier if not accounted for. The optimization algorithm responded to these reflections by placing material in the path of waves that would otherwise reflect back to the surface.

A wave barrier optimized for a three-layered soil model that consisted of a softer layer embedded in a stiff layer and a stiff half-space showed a different approach to reflections. The wave barrier appeared to use the softer layer as a waveguide in order to reduce the energy at the surface.

The manufacturability was increased by adding constraints. This resulted in wave barriers with a more manufacturable design at the cost of a decrease in vibration reduction. In three of the four cases, the optimized wave barrier still performed significantly better than the reference wave barrier. In one case, the final design reverted back to the reference wave barrier when the manufacturability conditions were applied.

The goals set at the start of the thesis were largely accomplished. The model was able to more accurately reflect soil profiles found in practice by using a layered soil model and the topology optimization algorithm resulted in wave barriers that are relatively easy to manufacture while still showing a significant improvement over the standard reference wave barriers. The possible use of
soft embedded layers as waveguides was discovered during the optimization. Future research into this possibility could prove valuable. Some concerns are posited with regards to the reliability of the wave barriers. In some cases, the optimized wave barrier appeared to abuse the idealized representation of the interface between layers. An initial investigation showed that in those cases,
the effectiveness of the wave barrier was sensitive to changes of the interface depth. Further investigation would be required to determine the sensitivity of the designed wave barriers to other parameters related to the idealized representations of the interfaces.