Dynamic Analysis of Portal Frame Bridges for High-Speed Trains : A Parametric Study

Abstract: A high-speed railway network is important for Sweden’s development. However, anincreasing train speed brings new challenges in bridge design due to higher bridgeaccelerations. This thesis addresses these challenges by investigating the dynamicbehavior of portal frame bridges subjected to high-speed train loads, while includingthe influence of the backfill soil. The aim is to minimize the bridge’s mass with focuson the thickness of the deck and abutments while meeting the acceleration criteriaoutlined in Eurocode. A parametric study is conducted using 2D models of portal framebridges with various cross sections and span lengths.The results show that the thickness of the deck plate plays a crucial role in reducingvertical deck accelerations, whereas the contribution of abutments is relativelyless significant. The findings also indicate that the soil-structure interaction (SSI)significantly influences the bridge’s response. It shows the importance of including SSIin dynamic analysis since the surrounding soil contributes with damping effects thatreduces the accelerations.Moreover, a graph representing deck stiffness is presented as a tool for designing portalframe bridges while considering the maximum allowable deck acceleration. The graphprovides approximate values of stiffness based on known parameters such as deckthickness and span length, offering guidance for bridge designers.In summary, this thesis provides insights into the dynamic behavior of portal framebridges and offers practical recommendations for their design, emphasizing theimportance of deck plate thickness and the influence of SSI.