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.

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Railway tracks are subjected to constant degradation in terms of geometry, and wear and tear of the track components (rails, sleepers, fasteners, trackbed layers, etc.). Over the years, trains have evolved immensely, but the track infrastructure has not kept pace. With rapid advancements in vehicle technologies, the design of rail infrastructure must cope with the challenges associated with the operation of railway tracks. In addition, railway transition zones (RTZs) degrade even faster (4-8 times) than normal tracks, leading to higher maintenance and operational costs. RTZs are areas where railway tracks cross stiffer structures (e.g., roads, bridges, culverts). The amplified degradation in RTZs is mainly attributed to abrupt changes in vertical stiffness and to differential settlement, resulting in amplified and non-uniformtrack responses. Even though the dynamic behavior of RTZs differs from that of normal tracks, the design of track components in these zones remains similar to normal tracks, with some modifications at the superstructure and/or substructure levels to mitigate the transition effects. There have been several attempts to mitigate the adverse effects of dynamic response amplification in RTZs, but they have proven either marginally effective or counterproductive. Therefore, a comprehensive design methodology for RTZs is needed that addresses the main degradation mechanisms leading to amplified degradation of these zones.

In this paper-based thesis, a novel methodology is proposed to design and evaluate railway transition zones. For this purpose, detailed analysis and design optimization is performed for a bridge-embankment transition using various two-dimensional and three-dimensional finite element models, different vehicle models, and surrogate models (using polynomial chaos expansion). Firstly, the proposed methodology establishes a robust design criterion to design and evaluate RTZs. The criterion relates the magnitude and uniformity (spatial and temporal) of the total strain energy in the trackbed layers to the permanent deformation of RTZs. This novel energy-based criterion is used to evaluate the most commonly used mitigationmeasures at the superstructure and substructure levels and to investigate the key phenomena governing RTZ design. Based on insights obtained from these analyses, a preliminary design of a novel transition structure called SHIELD (Safe Hull-Inspired Energy Limiting Design) is proposed. The second phase of the work is dedicated to identifying the most influential design parameters leading to optimized geometry of SHIELD and the desiredmaterial characteristics. The third phase involves the performance evaluation of optimized SHIELD subjected to critical loading conditions (e.g., critical and supercritical velocities, different directions of movement, hanging sleepers, non-straight rail) and SHIELD is shown to be a robust design solution for all conditions under study. In the end, the use of SHIELD is extended to another type of an embankment-bridge transition (with ballast running over the bridge) where it is shown to be equally (compared to embankment-bridge transition with no ballast layer over the bridge) efficient in mitigating the transition effects, and a laboratory experiment is designed to test the effectiveness of the proposed design criterion and methodology. A robust design methodology for RTZs is proposed in this work, which aims to minimize operation-induced degradation and can be adapted to different transition types and sitespecific conditions. A preliminary optimized design of SHIELD is proposed, which has been shown to be effective in mitigating dynamic amplifications in RTZs under both ideal and non-ideal conditions. The results and conclusions presented in this work demonstrate the promise of SHIELD as an intervention for railway transition zones, outline the next steps toward its practical implementation, and highlight the challenges that need to be addressed in future research.
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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. ... Read more

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.
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