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  • 1.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Lind Östlund, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Mahir, Ülker-Kaustell
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Full-Scale Dynamic Testing of a Railway Bridge Using a Hydraulic Exciter2018In: EXPERIMENTAL VIBRATION ANALYSIS FOR CIVIL STRUCTURES: TESTING, SENSING, MONITORING, AND CONTROL / [ed] Conte, JP Astroza, R Benzoni, G Feltrin, G Loh, KJ Moaveni, B, SPRINGER INTERNATIONAL PUBLISHING AG , 2018, p. 354-363Conference paper (Refereed)
    Abstract [en]

    This paper presents a full-scale dynamic testing on a simply supported railway bridge with integrated end-shields, by using a hydraulic exciter. Experimental frequency response functions are determined based on load controlled frequency sweeps. Apart from accurate estimates of natural frequencies, damping and mode shapes, the experimental testing also gives valuable information about the dynamic characteristics at resonance and amplitude dependent nonlinearities. Numerical models are used to simulate the dynamic response from passing trains which is compared to experimental testing of similar train passages. The results show that the bridge deck is partially constrained due to the interaction between the end-shields and the wing walls with the surrounding soil. Measurements at the supports also show that the flexibility of the foundation needs to be accounted for. An updated numerical model is able to accurately predict the response from passing trains. The response is lower than that predicted from the initial simulations and the bridge will fulfil the design requirements regarding vertical deck acceleration.

  • 2.
    Lind Östlund, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Mahir, Ülker-Kaustell
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Soil-Structure Interaction for foundations on High-Speed Railway Bridges2017Report (Other academic)
    Abstract [en]

    This report contains a parametric study on the dynamic response of railway bridges on flexible supports. The results are based on simulations using 2D and 3D models. The dynamic stiffness of the supports is described by separate models of the foundation, including relevant stress and strain dependent soil properties from permanent loading that is linearized in a subsequent dynamic analysis. The complex-valued dynamic stiffness constitutes the boundary conditions in a separate analysis of the bridge superstructure that is solved in frequency domain.

    Two different foundation types are studied; shallow slab foundation with relatively good ground conditions, and pile group foundations with relatively poor ground conditions. In both cases, the foundation slab and the pile group have fixed geometry. In the parametric study, the corresponding vertical static foundation stiffness range from 2 – 20 GN/m for the slab foundation and 5 – 25 GN/m for the pile group foundation.

    For the slab foundations, both the stiffness and damping highly depends on the properties of the soil, foundation depth and geometry of the foundation slab. For the pile group foundations, the stiffness is mainly governed by the pile group and the damping by the soil.

    Based on the simulations, the additional damping from the slab foundation is in most cases negligible. Only for relatively soft foundations and short-span bridges significant additional damping is seen. For the pile group foundations, the additional damping is in some cases significant, especially for deeper foundations and short-span bridges. Considering a lower bound of the parametric study does however result in a negligible contribution.

    The dynamic response from passing trains show that the assumption of fixed supports in most cases is conservative. However, the flexible supports may result in a lower natural frequency that should be accounted for in order to not underestimate the resonance speed of the train.

    If flexible supports are included in a dynamic analysis, both the stiffness and damping component needs to be included. The frequency-domain approach presented in this report is a viable solution technique but is not implemented in most commercial software used in the industry.

  • 3.
    Mahir, Ülker-Kaustell
    et al.
    KTH. Tyréns AB, Stockholm, Sweden.
    Östlund, J.
    KTH. Tyréns AB, Stockholm, Swede.
    Andersson, A.
    KTH. Tyréns AB, Stockholm, Swede.
    Current research and development in bridges for high-speed railways in Sweden2016In: IABSE Congress Stockholm, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment, International Association for Bridge and Structural Engineering (IABSE) , 2016, p. 2487-2494Conference paper (Refereed)
    Abstract [en]

    Short and stiff bridges are generally quite sensitive to the dynamic effects arising from train-bridge interaction. In the Swedish landscape, such bridges are common and represent 60-70% of the total bridge stock. Recent research has clearly shown that simple structural models may result in highly conservative predictions of the dynamic response of such structures. This has a large impact on the economy of these structures both for existing railway lines on which an increased maximum allowable speed could lead to a more efficient operation and for the design of new bridges on dedicated high-speed railways. This paper describes two promising modelling details that could lead to models that more accurately predict the dynamic response of such bridges; dynamic soilstructure interaction and the influence of rolling and sliding friction in bridge bearings. Currently, several research and development projects are aiming at increasing our understanding of these phenomena and at deriving simplified models that include these details in practical bridge design. Bridges with integrated abutments are common in Sweden as they provide an economic solution for many short bridges. However, simple models, which exclude the interaction between the abutments and the embankments, typically lead to theoretical dynamical responses that exceed the acceleration criteria given by the Eurocode. Recent research indicates that by modelling the interaction with the embankment, a more accurate and less conservative response may be obtained. Research regarding the influence of friction in bridge bearings has shown that a considerable additional damping can exist in bridges resting on either rolling or sliding bearings. An ongoing project attempts to quantify this additional damping and derive phenomenological models to include this effect in dynamic analyses of railway bridges in particular and bridges in general.

  • 4.
    Rådeström, Sarah
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Trafikverket.
    Mahir, Ülker-Kaustell
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyréns.
    Tell, Viktor
    Tyréns.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Structural control of high-speed railway bridges by means of fluid viscous dampers2016In: 19th IABSE Congress 2016, Zürich, Switzerland, 2016, p. 2535-2542Conference paper (Other academic)
    Abstract [en]

    The dynamic response of structures is an important aspect to consider, especially at resonance. Particularly, bridges traversed by trains are at risk, due to the repeated loading with regular interval from the axle and bogie spacings. If the risk of resonance is not accounted for in the design, the vertical acceleration of the bridge deck may exceed the allowed limits of comfort and safety. Hence, alternative, sustainable measures for reducing the vibrations in bridges are required to solve these challenges. This paper presents studies of fluid viscous dampers used to control the dynamic behaviour of high-speed railway bridges. A finite element model is used to investigate the response of an existing bridge, both prior to and after the installation of dampers, and the influence of some parameters on the efficiency of the dampers are analysed. The results from this paper show that the vertical deck acceleration is sufficiently reduced using the proposed solution.

  • 5.
    Rådeström, Sarah
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Mahir, Ülker-Kaustell
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyréns.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Trafikverket.
    Tell, Viktor
    Tyréns.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Application of fluid viscous dampers to mitigate vibrations of high-speed railway bridges2017In: International Journal of Rail transportation, ISSN 2324-8378, E-ISSN 2324-8386, Vol. 5, no 1, p. 47-62Article in journal (Refereed)
    Abstract [en]

    Several bridges along the Bothnia railway line in Sweden do not fulfil the Eurocode requirements regarding the maximum vertical bridge deck acceleration. The aim of this study is to investigate the possibility of reducing the acceleration of one of these bridges to an acceptable level by using post-installed viscous dampers. The bridge-damper system is described by a single-degree-of-freedom model. Assuming that the dampers do not change the mode shapes of the bridge, the model is further generalized to include higher order bending modes. The dampers are connected between the bottom surface of the bridge deck and the abutments.This creates an eccentricity between the connection point of the dampers and the neutral axis of the bridge, which is found to have a significant influence on the efficiency of the dampers. The results of this study also indicate that the proposed retrofit method can reduce the accelerations to an acceptable level.

  • 6.
    Tell, Sarah
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Leander, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Trafikverket.
    Mahir, Ülker-Kaustell
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyréns.
    Sensitivity analysis of a high-speed railway bridge with supplemental fluid viscous dampersManuscript (preprint) (Other academic)
    Abstract [en]

    One approach for upgrading existing high-speed bridges which are susceptible to excessive vibrations is to install damping devices. In this paper, a single-degree-of-freedom model of a simply-supported bridge with supplemental fluid viscous dampers installed between the superstructure and the abutments is derived based on an arbitrary mode of vibration. Further, to ensure the robustness of the proposed vibration mitigation method, a statistical screening of the uncertainties associated with the bridge-damper system is conducted using Monte-Carlo simulations. From this screening, it is possible to evaluate the probability of exceedance of a stipulated acceleration level, as well as studying the sensitivity of the ingoing random variables. This paper also highlights the necessity of conducting a statistical assessment to determine an estimate for the distribution of the acceleration limit and model uncertainty for dynamic analyses. The results also show that 1) the modulus of elasticity and structural damping should be treated as stochastic variables for the studied bridge, 2) it is sufficient to install damping devices only at the moveable bearing and 3) the proposed retrofit is insufficient if the friction of the moveable bearings is not overcome for the given set of damper parameters.

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