Change search
Refine search result
1 - 30 of 30
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Carlsson, Fredrik
    Lunds Tekniska Höskola.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Enochsson, Ola
    Luleå Tekniska Universitet.
    Karoumi (Redaktör), Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Plos, Mario
    Chalmers Tekniska Högskola.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE).
    Täljsten, Björn
    LuleåTekniska Universitet.
    Wiberg, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Ülker, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Modern mät- och övervakningsmetodik för bedömning av befintliga broar2007Report (Other academic)
  • 2.
    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.

  • 3.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. The Swedish Transport Administration (Trafikverket), Sweden.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyréns AB, Sweden.
    Borg, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dymén, Olivier
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Carolin, Anders
    Trafikverket.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Pilot testing of a hydraulic bridge exciter2015In: EVACES'15, 6th International Conference on Experimental Vibration Analysis For Civil Engineering Structures / [ed] Glauco Feltrin, Zurich: EDP Sciences, 2015, Vol. 24, p. 02001-Conference paper (Refereed)
    Abstract [en]

    This paper describes the development of a hydraulic bridge exciter and its first pilot testing on a full scale railway bridge in service. The exciter is based on a hydraulic load cylinder with a capacity of 50 kN and is intended for controlled dynamic loading up to at least 50 Hz. The load is applied from underneath the bridge, enabling testing while the railway line is in service. The system is shown to produce constant load amplitude even at resonance. The exciter is used to experimentally determine frequency response functions at all sensor locations, which serve as valuable input for model updating and verification. An FE-model of the case study bridge has been developed that is in good agreement with the experimental results.

  • 4.
    Axelsson, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Syk, Annelie
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ülker Kaustell, Mahir
    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.
    Effect of axle load spreading and support stiffness on the dynamic response of short span railway bridges2014In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 4, p. 457-465Article in journal (Refereed)
    Abstract [en]

    In dynamic analyses of railway bridges, the train axle loads are often modeled as moving point forces. However, one effect of the ballast is to spread these point forces. This can lead to large reductions of the bridge response, especially for short span bridges. For this reason, Eurocode prescribes to distribute the axle loads over three adjacent sleepers. In this paper, the axle load distribution is first studied using a plane finite element analysis and based on that, a triangular load distribution is proposed. Then, numerical simulations are performed to compare the effect of this load distribution with the Eurocode one. Both simply supported bridges and bridges with integrated backwalls, all with span lengths less than 10m, are studied. For the later bridges, the effect of the stiffness of the foundation has been studied by adding springs at the supports.

  • 5.
    Axelsson, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Syk, Annelie
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ülker Kaustell, Mahir
    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.
    Effect of the spreading of the axle load through the ballast on the dynamic response of short span railway bridges2013In: Ballast: Issues & Challenges, 2013, p. 25-25Conference paper (Refereed)
  • 6.
    Battini, Jean-Marc
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    A simple finite element to consider the non-linear influence of the ballast on vibrations of railway bridges2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 9, p. 2597-2602Article in journal (Refereed)
    Abstract [en]

    This article proposes a new and simple finite element which can be used to analyze vertical vibrations in railway bridges. The main feature of the element is that the effect of the ballast is introduced through a non-linear longitudinal stiffness associated to the slip at the interface between the bridge and the ballast. Two numerical applications show that this element can be used to model the variation of the natural frequencies of the bridge as a function of the amplitude of vibration.

  • 7.
    Cantero, Daniel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Arena House, Ireland.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Tyréns AB, Sweden.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Time-frequency analysis of railway bridge response in forced vibration2016In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 76-77, p. 518-530Article in journal (Refereed)
    Abstract [en]

    This paper suggests the use of the Continuous Wavelet Transform in combination with the Modified Littlewood-Paley basis to analyse bridge responses exited by traversing trains. The analysis provides an energy distribution map in the time-frequency domain that offers a better resolution compared to previous published studies. This is demonstrated with recorded responses of the Skidträsk Bridge, a 36 m long composite bridge located in Sweden. It is shown to be particularly useful to understand the evolution of the energy content during a vehicle crossing event. With this information it is possible to distinguish the effect of several of the governing factors involved in the dynamic response including vehicle's speed and axle configuration as well as non-linear behaviour of the structure.

  • 8.
    Gonzalez, Ignacio
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ülker-Kaustell, Mahir
    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.
    Seasonal effects on the stiffness properties of a ballasted railway bridge2013In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 57, p. 63-72Article in journal (Refereed)
    Abstract [en]

    In this article it is shown empirically that ballasted bridges in cold climates can exhibit a step-like variation of their natural frequencies as the yearly season changes. The bridge under study was observed to have significantly higher natural frequencies (as much as 35%) during the winter months compared to the summer. This variation was rather discrete in nature and not proportional to temperature. Furthermore the increase in natural frequencies took place only after the temperatures had dropped below 0 °C for a number of days. It was thus hypothesized that this change in natural frequencies was due to changes in the stiffness parameters of some materials with the onset of frost. In low temperature conditions not only the mean value of the measured frequencies increased, but also their variance increased considerably. Given the large spread of the measured natural frequencies, the stiffness parameters were assumed to be stochastic variables with an unknown multivariate distribution, rather than fixed values. A Bayesian updating scheme was implemented to determine this distribution from measurements. Data gathered during one annum of monitoring was used in conjunction with a finite element model and a meta model, resulting in an estimation of the relevant stiffness parameters for both the cold and the warm condition.

  • 9.
    Johansson, Christoffer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Wiberg, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Höghastighetsprojekt ‐ Bro: Delrapport I: Befintliga krav och erfarenheter samt parameterstudier avseende dimensionering av järnvägsbroar för farter över 200 km/h2010Report (Other academic)
  • 10.
    Karoumi, Raid
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Monitoring of the New Svinesund Bridge: Report 3, The influence of temperature, wind and damages on the dynamic properties of the Bridge2006Report (Other academic)
  • 11.
    Karoumi, Raid
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Uppskattning av upplagsstyvheter och effekter av jord-bro interaktion genom dynamisk mätning. Steg 1: Presentation av mätdata och skattning av egenfrekvenser och dämpkvoter hos broarna över Banafjälsån och Östra Lillmosjövägen2008Report (Other academic)
  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    Rådeström, Sarah
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Tell, Viktor
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Department of Bridges, Tyréns AB, Stockholm, Sweden.
    Ülker Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Department of Bridges, Tyréns AB, Stockholm, Sweden.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Parametric evaluation of viscous damper retrofit for high-speed railway bridges2015Conference paper (Refereed)
    Abstract [en]

    Several of the bridges belonging to the Bothnia Line, located in northern Sweden, do not theoretically fulfil the current design limit for the vertical deck acceleration, when being subjected to high-speed trains. Hence, it is important to find appropriate vibration mitigation strategies that are applicable to railway bridges, in order to reduce the acceleration caused by passing trains. One way of solving this problem is to install external viscous dampers. A finite element solution for damper retrofit of high-speed railway bridges is proposed in this paper. The bridge is modelled as a two-dimensional Euler-Bernoulli beam, with inclined dashpots connected between the superstructure and the abutments. Furthermore, this paper highlights the influence of several parameters on the effectiveness of the dampers.

  • 17.
    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.

  • 18.
    Ulker, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Övervakning av accelerationer i broar vid passage av Gröna Tåget2006Report (Other academic)
  • 19.
    Ulker-Kaustell, Mahir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Application of the continuous wavelet transform on the free vibrations of a steel-concrete composite railway bridge2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 3, p. 911-919Article in journal (Refereed)
    Abstract [en]

    In this article, the Continuous Wavelet Transform (CWT) is used to study the amplitude dependency of the natural frequency and the equivalent viscous modal damping ratio of the first vertical bending mode of a ballasted, single span, concrete steel composite railway bridge. It is shown that for the observed range of acceleration amplitudes, a linear relation exists between both the natural frequency and the equivalent viscous modal damping ratio and the amplitude of vibration. This result was obtained by an analysis based on the CWT of the free vibrations after the passage of a number of freight trains. The natural frequency was found to decrease with increasing amplitude of vibration and the corresponding damping ratio increased with increasing amplitude of vibration. This may, given that further research efforts have been made, have implications on the choice of damping ratios for theoretical studies aiming at upgrading existing bridges and in the design of new bridges for high speed trains. The analysis procedure is validated by means of an alternative analysis technique using the least squares method to fit a linear oscillator to consecutive, windowed parts of the studied signals. In this particular case, the two analysis procedures produce essentially the same result.

  • 20.
    Zäll, E.
    et al.
    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. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Ülker-Kaustell, Mahir
    KTH. Tyréns AB, Stockholm, Sweden.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Swedish Transport Administration, Solna, Sweden.
    Evaluation of load model for crowd-induced vibrations of footbridges2016In: 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. 65-72Conference paper (Refereed)
    Abstract [en]

    Due to a trend in designing light and slender structures, many modern footbridges are prone to excessive vibrations. Severely vibrating footbridges can give rise to discomfort for the pedestrians. Therefore, during the last decades, pedestrian-induced vibrations of footbridges have become a subject of great interest. In this study, the performance of a coupled crowd-structure model, where the bridge is described using its first two modes of vibrations and each pedestrian is described as a moving mass-spring-damper system, in combination with a walking load, is evaluated. The model is used to estimate vertical deck accelerations of a real footbridge which is known to be susceptible to vibrations, and the results are then compared to measurements. The model performs satisfactory in the time domain, but poorly in the frequency domain, which is concluded to be mainly due to discrepancies in the simulated load compared to the measured load.

  • 21.
    Zäll, Emma
    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. Swedish Transport Administration, Sweden.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyrens AB, Sweden.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    An efficient approach for considering the effect of human-structure interaction on footbridges2017In: X International Conference on Structural Dynamics, EURODYN 2017, Elsevier, 2017, Vol. 199, p. 2913-2918Conference paper (Refereed)
    Abstract [en]

    Mainly because of the infamous incident with excessive vibrations of the London Millennium Bridge, the behavior of lively footbridges has been thoroughly studied lately. The liveliness of such bridges is strongly connected to various interaction effects between the pedestrians and the bridges. One such effect is the variation in the modal properties of the bridge, due to the presence of a crowd. In theoretical models of such systems, this is often accounted for by describing each pedestrian as a spring-mass-damper system, having its own dynamic properties, producing a time-variant system. A major drawback with models of this kind is that the computational time increases rapidly with the size of the system, i.e. for a larger crowd. Therefore, with the objective to reduce the computational time needed, this study focuses on describing vertical human-structure interaction by means of a simplified model. The paper describes a new methodology for taking this effect into consideration when predicting the dynamic response of a footbridge, subjected to human-induced, vertical loads. The method is used to predict the vertical bridge deck accelerations of a simply supported footbridge. The predictions produced by the proposed methodology are compared with existing models and it is shown that for certain bridges, it produces an accurate approximation at a significantly reduced computational cost.

  • 22.
    Östlund, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyréns AB, Sweden.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyréns AB, Sweden.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Swedish Transport Administration, Sweden.
    Battini, Jean Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Considering dynamic soil-structure interaction in design of high-speed railway bridges2017In: X International Conference on Structural Dynamics, EURODYN 2017, Elsevier, 2017, Vol. 199, p. 2384-2389Conference paper (Refereed)
    Abstract [en]

    This article presents preliminary theoretical results on the influence of dynamic soil-structure interaction (SSI) of slab foundations. Impedance functions, representing the dynamic SSI, were obtained from FE-models depicting the soil for a few cases of different geotechnical preconditions. The obtained impedance functions were attached to single-span bridges and HSLM-A analyses were performed. The effect of the impedance functions on the bridge response was studied and compared to the ultimate case of a bridge on rigid supports. The influence of SSI seems to have a significant effect on railway bridges. This study shows that by including this effect in bridge design, the damping ratio of the system is largely increased, giving lower acceleration amplitudes in the bridge, while the natural frequencies are less affected.

  • 23.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Damping from bearing hysteresis in railway bridges2014In: EURODYN 2014: IX INTERNATIONAL CONFERENCE ON STRUCTURAL DYNAMICS, 2014, p. 1303-1308Conference paper (Refereed)
    Abstract [en]

    The hysteretic behavior of bridge bearings contributes significantly to the overall damping of certain bridges. In railway bridge dynamics, the ability to dissipate energy is a key property, governing the resonant amplitudes of vibration. However, the efficiency of these damping mechanisms is coupled to parameters such as construction height and support stiffness. This paper presents an analysis of three different railway bridges, where the hysteretic behavior of the bearing mechanisms is modelled using the classical Bouc-Wen model. Both sliding and roller bearings are assumed to have similar backbone curves, the parameters of which have been chosen on basis of simple reasoning. Experimentally determined backbone curves for these mechanical subsystems are not available today. Instead, the performed analysis is validated by means of measurements of vertical acceleration in the bridge decks. The results show that the hysteretic behavior of the bridge bearings could explain the non-linear effects which can be seen in the frequency and amplitude modulation of the free vibrations in the studied bridges.

  • 24.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamic behaviour of pot bearings: A preliminary study2017Report (Other academic)
  • 25.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Essential modelling details in dynamic FE-analyses of railway bridges2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increased need to reduce the use of fossil fuels imposes higher demands on the efficiency of rail transportation. Therefore, an improved knowledge regarding the dynamic properties of railway bridges and infrastructure for railway traffic in general is required. Typically, increased train speed, longer trains and increased axle loads increase the dynamic response in railway bridges. Modelling details for bridge structures such as the flexibility of the foundations, radiation damping in the subsoil and the embankments as well as hysteretic effects in bridge bearings and the track superstructure are typically neglected. The reason for this is that suitable models which consider the influence of such effects in engineering calculations have not yet been implemented in the effectual design codes. This thesis is mainly based on a case study of a ballasted, simply supported steel-concrete composite bridge, which shows a considerable variation in the natural frequencies and damping ratios depending on the amplitude of vibration. Furthermore, the natural frequencies were found to increase significantly during the winter. It is well known that the dynamic properties of typical civil engineering structures are dependent on the amplitude of vibration. However, the fact that certain railway bridges exhibit such non-linear behaviour also for very small amplitudes of vibration has been shown only during later years. This has been verified by means of measurements of the free vibrations after train passages on three typical Swedish beam bridges for railway traffic. Possible sources to this amplitude dependency have been identified primarily in the bridge bearings and the track superstructure. Models of these structural components, based on the so called Bouc-Wen model, have been implemented in a commercial finite element program and was used in a preliminary study. The results indicate that roller bearings and pot bearings can give rise to a non-linear mode of vibration, characterised by two different states. At very small amplitudes of vibration (. 0:1m=s2), no movement over such bearings occur (state 1) since their initial resistance to motion is not overcome. Depending on parameters such as the longitudinal stiffness of the foundations and substructures, the beam height over the supports as well as the bearing type, there is an amplitude of vibration at which the initial resistance to motion is completely overcome (state 2). The bearings are then free to move, with a resistance characterised by the kinematic friction (pot bearings) or the rolling resistance (roller bearings). During the transition from state 1 to state 2, the frequency decreases continuously towards an asymptotic value and the damping initially grows considerably, from a value which corresponds quite well to the recommendations of the Eurocodes and then returns to a value similar to that in state 1. The preliminary study indicates that it is possible to design certain bridges so that this increase in damping is optimal over the relevant range of amplitudes of vibration.

  • 26.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Influence of vibration amplitude on the response of a ballasted railway bridge2012In: Proceedings of the The First International Conference on Railway Technology: Research, Development and Maintenance, 2012Conference paper (Refereed)
  • 27.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Some aspects of the dynamic soil-structure interaction of a portal frame bridge2009Licentiate thesis, monograph (Other academic)
    Abstract [en]

    For certain bridge types, the influence of soil-structure interaction (SSI) may have an important contribution to the stiffness and damping of the structural system. From a design point of view, this influence may be both conservative and non-conservative and therefore, an increased knowledge within this field could lead to better design assumptions. In terms of maintenance, assessment and upgrading of existing structures, an increased knowledge of the phenomena and parameters which govern the soil-structure interaction, may lead to more realistic models and thereby, to more precise information for the decision makers and railway system owners and administrators.

    SSI appears to be most important for short and relatively stiff structures such as portal frame bridges. Dynamic analyzes of this bridge type have shown a large sensitivity in the choice of boundary conditions, where applying elastic constraints on the vertical degree of freedom at the support, compared to fixing this degree of freedom, may increase the maximum vertical bridge deck acceleration by as much as a factor of three.

    In this thesis, numerical analysis procedures for the computation of dynamic stiffness functions describing the frequency dependency of the foundation-soil interface have been explored under the assumption that the analysis can be performed using linear theories alone. The numerical solution of the equations of motion of structural systems, including such frequency dependent parameters, is performed using an integration scheme based on the discrete Fourier transform. Furthermore, preliminary experimental work on a newly built portal frame bridge is described. This portal frame bridge is subject to a case study in which the the computational techniques mentioned above are applied on a two dimensional model of the bridge. Theoretically, the damping of the SSI is shown to give a large contribution to those modes of vibration which excite the foundations much. These structural modal damping ratios may be much larger than those prescribed by the design codes. Those modes of vibration which do not excite the foundations much are similar to those obtained using clamped or constant elastic boundary conditions and in these cases, the contribution to the modal damping ratio of the structure is only a fraction of that prescribed by the design codes. A very rough analysis of measurements taken from the bridge indicate a similar behavior, but the amplitudes of vibration in many of the estimated modes are quite small (in the order of the quantization error of the measurement system) and therefore, the errors in the damping ratio estimates may be substantial. The work with this thesis have raised many questions, the answers to which are believed to substantially improve our understanding of resonance phenomena and also our possibilities to update numerical models of existing railway bridges using dynamic measurements.

    From the simplified analysis of a portal frame bridge performed within this project, it has been concluded that when the elastic modulus of the soil is increased, the total structural damping ratio when dynamic SSI is included decreases. Furthermore, with respect to vertical bridge deck accelerations, clamped boundary conditions are certainly not conservative as compared with static and dynamic SSI.

  • 28.
    Ülker-Kaustell, Mahir
    et al.
    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.
    Influence of non-linear stiffness and damping on the train-bridge resonance of a simply supported railway bridge2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 41, p. 350-355Article in journal (Refereed)
    Abstract [en]

    Previous experimental work has identified Variations in the natural frequency and the modal damping ratio of the first vertical bending mode of vibration of a simply supported, single span steel-concrete composite bridge. It was found that the natural frequency decreased and the modal damping ratio increased with increasing amplitudes of vibration. This paper illustrates the influence of these variations on the train-bridge resonance of this particular bridge by means of a non-linear single degree of freedom system, based on the previously mentioned experimental results. As one might expect, the results indicate that the influence of the increasing damping ratio leads to a considerable decrease in the resonant amplitude whilst the decreasing natural frequency decreases the critical train speed at which resonance occurs. Further studies along this line of research may help us reduce the uncertainties in dynamic assessments of existing bridges based, on dynamic measurements and improve our understanding of the dynamic properties of railway bridges in general.

  • 29.
    Ülker-Kaustell, Mahir
    et al.
    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.
    Influence of rate-independent hysteresis on the dynamic response of a railway bridge2013In: International Journal of Rail Transportation, ISSN 2324-8386, Vol. 1, no 4, p. 237-257Article in journal (Refereed)
    Abstract [en]

    It is well known that the dynamic properties of civil engineering structures have a more or less pronounced amplitude dependency. However, it is rather difficult to quantify this both experimentally and theoretically. This paper describes an attempt to identify the sources of the amplitude dependent variation of the natural frequency and the modal damping ratio of the first vertical bending mode of a simply supported, ballasted steel-concrete composite railway bridge. It is proposed that the most likely sources to the non-linear properties of this mode of vibration are the ballasted track, the foundations and the roller bearings used mainly to relive constraint forces due to changes in temperature. The non-linear influence of the suggested sources were modelled in a 2D finite element model using the classical univariate Bouc–Wen model which was implemented as a user-defined element in ABAQUS. The results suggest that the roller bearings alone can give account for the variation in the dynamic properties observed in experimental data from the bridge and that the combination with a simple model of the track superstructure gives the most realistic result. A tremendous increase in the dissipation of energy was found as the amplitude of vibration was increased beyond that available in the experimental data, thus motivating further research within this field.

  • 30.
    Ülker-Kaustell, Mahir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Simplified analysis of the dynamic soil-structure interaction of a portal frame railway bridge2010In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 32, no 11, p. 3692-3698Article in journal (Refereed)
    Abstract [en]

    A qualitative analysis of the dynamic soil-structure interaction (SSI) of a portal frame railway bridge based on the linear theory of elasticity is presented. The influence of SSI on the dynamic properties of the structure and its response due to the high-speed load model (HSLM) of the Eurocode is analyzed by simple concepts from the finite element theory. The dynamic behavior of the foundations of the structure is introduced by means of dynamic stiffness functions, describing the stiffness and damping of the foundation-soil interface. These frequency dependent functions are used as boundary conditions on a two-dimensional Euler-Bernoulli model of the structure. The equations of motion are solved in the frequency domain and the time domain solution is obtained by the fast Fourier transform algorithm. It is shown that the radiation and material damping of the foundation-soil interface may give a substantial contribution to the modal damping ratio of the structure. A comparison of the dynamic response of the structure, subjected to the HSLM assuming different SSI models shows that fixing the vertical degree of freedom may grossly underestimate the vertical acceleration in the bridge deck.

1 - 30 of 30
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf