COMPARATIVE STUDY OF DIFFERENT TYPE OF SUPERSTRUCTURES UNDER HIGH-SPEED TRAIN LOADING

Abstract

This thesis presents a comprehensive comparative study on the impact of high-speed train loading on two types of superstructures: U-Girder and Box Girder, specifically within the context of the Regional Rapid Transit System (RRTS) in India. The research delves into the structural behaviour, dynamic response, economic considerations, and construction benefits under high-speed rail loading conditions. The study employs a detailed dynamic analysis of U-Girder and Box Girder bridges using finite element models created with SOFISTIK software. The analysis methodology includes modal superposition for dynamic analysis, considering various loading scenarios such as dead load, superimposed dead load, and live load. The numerical modelling process, parameter variations, and validation steps are meticulously outlined, ensuring accurate and reliable results. Key aspects analysed include maximum acceleration, deflection under different speed, span configurations, and the feasibility of these sections under high-speed loading. The results indicate that U-Girder tend to exhibit higher deflection due to their lower torsional rigidity, whereas Box Girder demonstrate greater torsional rigidity, resulting in reduced deflection and enhanced suitability for longer spans and higher loads. Box Girder also shows lower vertical acceleration and deflection compared to U-Girder, attributed to their closed cross-section which provides greater stiffness and stability. However, both types maintain acceptable levels of vertical acceleration and displacement according to BS EN 1991-2:2003 and BS EN 1990 Standards. The analysis reveals that U-Girder require less concrete compared to Box-Girders, leading to potential cost savings and reduced environmental impact. Despite their smaller v volumes, U-Girder maintain sufficient structural integrity and load-carrying capacity, making them a cost-effective option for elevated construction projects. The simpler and faster construction process of U-Girder results in lower energy consumption and emissions, further reducing their carbon footprint. Additionally, the benefits of U-Girder extend to the reduction in the longitudinal profile of the rail line, lowering stations levels, and minimizing earthwork, all contributing to cost savings and environmental benefits. The study’s findings suggest that U-Girder are a viable and advantageous choice for high speed rail infrastructure, balancing performance, cost efficiency, and environmental sustainability. The conclusions drawn provide valuable insights into ensuring safe operational conditions for both U-Girder and Box Girder viaducts/Bridges under dynamic loading, facilitating the standardization of cross-section for various span lengths, and ultimately reducing economic and environmental impacts. This research lays a strong foundation for future studies, including understanding the behaviour under continuous span configurations, shell modelling of superstructure to understand the lateral distribution, and comprehensive life cycle assessments to further evaluate the environmental impact of elevated construction projects involving U-Girder and Box Girder.