Change search
Refine search result
1234567 1 - 50 of 534
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • 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.
    Aagah, Orod
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Aryannejad, Siavash
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamic analysis of soil-steel composite railway bridges: FE-modeling in Plaxis2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A soil-steel composite bridge is a structure comprised of corrugated steel plates, which are joined with bolted connections, enclosed in friction soil material on both sides and on the top. The surrounding friction soil material, or backfill, is applied in sequential steps, each step involving compaction of the soil, which is a necessity for the construction to accumulate the required bearing capacity. Soil-steel composite bridges are an attractive option as compared with other more customary bridge types, owing to the lower construction time and building cost involved. This is particularly true in cases where gaps in the form of minor watercourses, roads or railways must be bridged.

    The objective of this master thesis is the modelling of an existing soil-steel composite railway bridge in Märsta, Sweden with the finite element software Plaxis. A 3D model is created and calibrated for crown deflection against measurement data collected by the Division of Structural Engineering and Bridges of the Royal Institute of Technology (KTH) in Stockholm, Sweden.

    Once the 3D model is calibrated for deflection, two 2D models with different properties are created in much the same way. In model 1, the full axle load is used and the soil stiffness varied, and in model 2 the soil stiffness acquired in the 3D model is used and the external load varied. The results are compared to measurement data. In 2D model 1 an efficient width of 1,46 m for the soil stiffness is used in combination with the full axle load, and in 2D model 2 an efficient width of 2,85 m is used for the external load, in combination with the soil stiffness acquired in the 3D model.

    Aside from this, parametric studies are performed in order to analyse the effect of certain input parameters upon output results, and in order to analyse influence line lengths.

    Recreating the accelerations and stresses in the existing bridge using finite element models is complicated, and the results reflect this. Below are shown the discrepancies between model results and measurement data for the pipe crown. The scatter in the measurement data has not been taken into consideration for this; these specific numbers are valid only for one particular train passage.

    For crown deflection, the 3D model shows a discrepancy of 4%, 2D model 1 5% and 2D model 2 8% compared with measurement data. For crown acceleration, in the same order, the discrepancy with measurements is 1%, 71% and 21% for maximum acceleration, and 46%, 35% and 28% for minimum acceleration. For maximum crown tensile stress, the discrepancy is 95%, 263% and 13%. For maximum crown compressive stress, the discrepancy is 70%, 16% and 46%.

  • 2.
    Abdulrahman, Keiwan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Potrus, Fadi
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Numerical analysis and model updating of a steel-concrete composite bridge: Parametric study & Statistical evaluation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the year 2006, only 10 years after the steel- concrete composite bridge, Vårby bridge was built, fatigue cracks were found during an inspection. To further investigate the reasons and the potential danger of the cracks, an investigation under the commission of the Swedish Transport Administration was issued in 2009. After the detection of fatigue cracks, several measurements were carried out in order to monitor the static behavior by the use of strain gauges at selected positions along the bridge. The measurements from the strain gauges monitoring the global behavior were then used to calibrate an finite element model.

     

    The present report is part of the research of understanding the behavior of steel-concrete composite bridges. Numerical analysis and model updating have been used in order to understand and determine how different parameters affects the strain range and the global behavior. The numerical analysis and parameter study were performed in the Finite Element software Abaqus and programming language Python. The outcome of the parameter study was then used to perform the model updating by the method of falsification in MATLAB.

     

    The results from the parameter study and the model updating showed that the measured strains could be reached with a wide range of parameter combinations. Even with unreasonable parameter values, the measured strains were obtained. To investigate the reason for this, a multiple linear regression analysis was performed which showed that the strain range is strongly correlated to the Young’s modulus of steel and concrete and also to the connector elasticity, which resembles the studs in the real bridge.

     

    Two different finite element models, with two completely different input parameter values, obtain the same strain range for the global behavior. It is therefore not certain to assume that a model is accurate and valid based on the fact that the predicted strain range from the finite element model is close to the measured strain range since the global behavior of a steel- concrete composite bridge can be modeled by many different sets of parameters.

  • 3.
    Aboutalebi, Ghareman
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Optimering av fackverksstolpar med konisk eller parallell form2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 4.
    Acar, Yalda
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Jingstål, Pontus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Influence of the Non-linear Effects in the Design of Viscous Dampers for Bridge Cables2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master thesis the performance of external viscous dampers attached to cables in cable-stayed bridges have been studied. A comparison has been performed between a linear and a non-linear cable model. The comparison was carried out for two bridge cables, one from the Dubrovnik Bridge and the other from the Normandie Bridge. The performance of the dampers have been measured in terms of maximum achieved damping ratio and minimum amplitude of vibration.

    The analysis was performed using the finite element method. The damping ratio was measured using both the half-power bandwidth method and by calculating the loss factor. The half-power bandwidth method can only be applied to a linear system. Therefore, the loss factor was evaluated for the linear model and compared to the results obtained using the half-power bandwidth method. From the comparison, it was concluded that the damping ratio evaluated using the loss factor was similar to the results obtained when using the half-power bandwidth method. However, when calculating the loss factor, it was of great importance that the resonance frequency of the system was accurately determined. The loss factor was then calculated for the non-linear model and compared to the results obtained for the linear model. Since the loss factor measures the energy dissipated in a system, it could be utilised for the non-linear model. When computing the strain energy for the non-linear model an approximate method was used to take into consideration the strain energy caused by the static deformation of the cable.

    From the comparison between the linear and non-linear cable models, it was concluded that the optimal damper coefficients obtained by both models are not significantly different. However, there is an uncertainty in the results due to the fact that an approximate method was used when calculating the strain energy for the nonlinear model. It was also observed that a very accurate evaluation of the system’s resonance frequency was needed to calculate the loss factor. It was also observed that the variation in amplitude of vibration for varying damper coefficient was small for all modes of vibration for the Dubrovnik Bridge Cable as well as for the first mode of vibration for the Normandie Bridge Cable. The difference in the results between the two bridge cables needs to be investigated further in order to get a better understanding of the results.

  • 5.
    Ahne, Alexander
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Wikforss, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Projektering av brandskydd för stålkonstruktioner2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 6.
    Akhondi, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Pelletäppan, tennishall med bristfällig konstruktion: En fallstudie av massiv limträkonstruktion2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete bygger på en jämförelse mellan Boverkets Byggregler och Eurokoder för en befintlig limträkonstruktion. Referensobjektet är en tennishall belägen i Botkyrka kommun. Objektet byggdes under början på 90-talet i form av en treledsram med taktäckning av PVC duk som vilar direkt på limträbalkarna, inklusive en inre duk med mellanliggande isolering och luftspalt. Under de senaste åren har konstruktionen uppvisat tecken på svagheter med bl.a. stora sprickor i limträbalkarna, dessa skador kulminerade i att på begäran av kommunen stänga av anläggningen för fortsatta spel.

    Oavsett om beräkningarna utförs med BKR eller Eurokoder som är norm idag så har stommen inte tillräckligt bärighet för sin egentyngd och dagens snölast. Detta kan tyckas vara märkligt men förklaringen kan vara att man utförde byggnaden med tanke på att snön glider av hallen och inte ackumuleras. Med detta i åtanke skulle snön glida av om yttertaken hade hållits varm, mycket tyder på att så skulle ha varit fallet om fläktarna som luftar spalten i takkonstruktionen hade varit igång. Enligt Roger Vintemar, verksamhetschef för Idrott och Anläggning på Botkyrka kommun, har fläktaggregatets på/av knapp placerats lättillgängligt i spelargången och det finns anledning att misstänka att fläktaggregatet har varit avstängd vid långa perioder. Sprickorna i bågarna kan bero på överlast eftersom snön har ackumulerats och inte glidit av. Med avseende på hur konstruktionen är utformad och att det har blivit vattenansamlingar på spelbanan är det inte orimligt att ifrågasätta dragstagets rostskydd. Skulle dragstaget som håller ihop de två bågarna brista finns det en överhängande risk för s.k. sprött brott med ett snabbt ras till följd.

  • 7. Alhasawi, Anas
    et al.
    Heng, Piseth
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Université Européenne de Bretagne, France.
    Hjiaj, Mohammed
    Guezouli, Samy
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Co-rotational planar beam element with generalized elasto-plastic hinges2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 151, p. 188-205Article in journal (Refereed)
    Abstract [en]

    Slender elements in framed structures may undergo large displacement and experience highly nonlinear behavior. This paper presents a two-node co-rotational flexible beam with generalized elasto-plastic hinges at the beam ends. A Condensation procedure is used to remove the internal degrees of freedom so that the formulation is easily incorporated with the standard co-rotational approach. A family of asymmetric and convex yield surfaces of super-elliptic shape is considered for the plastic behavior of the hinges. By varying the roundness factor, an infinite number of yield surfaces are obtained making it possible to select the yield function that best fit experimental data of any type of cross-section and material. The nonlinear response of bolted connections subjected to both bending and axial forces are conveniently modeled with such a yield surface. Discrete constitutive equations for the hinge plastic deformations are derived using the implicit scheme for both smooth and non-smooth cases. Numerical examples demonstrate the accuracy of the model in predicting the large displacement inelastic response of framed structures. Effect of the roundness factor on the ultimate load strongly depends on the structure typology. It was observed that cyclic loading produces pinching effect, cyclic softening and ductile behavior. Those effects are more pronounced with anisotropic yield criteria.

  • 8. Alsafadie, R.
    et al.
    Battini, Jean -Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Somja, H.
    Hjiaj, M.
    Local formulation for elasto-plastic corotational thin-walled beams based on higher-order curvature terms2011In: Finite elements in analysis and design (Print), ISSN 0168-874X, E-ISSN 1872-6925, Vol. 47, no 2, p. 119-128Article in journal (Refereed)
    Abstract [en]

    The paper deals with the derivation of a local elasto-plastic finite element formulation of three dimensional corotational beams with arbitrary cross- section. Based on Bernoulli beam kinematics, an improved displacement field is constructed by inclusion of second-order terms of cross-section local rotations. The formulation captures both the Saint-Venant and warping torsional effects of open cross sections. Numerical tests show that the inclusion of the second-order terms of the local bending curvatures gives more accurate and more efficient element that allows a significant reduction of the computational time.

  • 9. Alsafadie, R.
    et al.
    Hjiaj, M.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Corotational mixed finite element formulation for thin-walled beams with generic cross-section2010In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 199, no 49-52, p. 3197-3212Article in journal (Refereed)
    Abstract [en]

    The corotational technique is adopted here for the analysis of three-dimensional beams. The technique exploits the technology that applies to a two-noded element, a coordinate system which continuously translates and rotates with the element. In this way, the rigid body motion is separated out from the deformational motion. In this paper, a mixed formulation are adopted for the derivation of the local element tangent stiffness matrix and nodal forces. The mixed finite element formulation is based on an incremental form of the two-field Hellinger-Reissner variational principle to permit elasto-plastic material behavior. The local beam kinematics is based on a low-order nonlinear strain expression using Bernoulli assumption. The present formulation captures both the Saint-Venant and warping torsional effects of thin-walled open cross-sections. Shape functions that satisfy the nonlinear local equilibrium equations are selected for the interpolation of the stress resultants. In particular, for the torsional forces and the twist rotation degree of freedom, a family of hyperbolic interpolation functions is adopted in lieu of conventional polynomials. Governing equations are expressed in a weak form, and the constitutive equations are enforced at each integration cross-section along the element length. A consistent state determination algorithm is proposed. This local element, together with the corotational framework, can be used to analyze the nonlinear buckling and postbuckling of thin-walled beams with generic cross-section. The present corotational mixed element solution is compared against the results obtained from a corotational displacement-based model having the same beam kinematics and corotational framework. The superiority of the mixed formulation is clearly demonstrated.

  • 10. Alsafadie, R.
    et al.
    Hjiaj, M.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Three-dimensional formulation of a mixed corotational thin-walled beam element incorporating shear and warping deformation2011In: Thin-walled structures, ISSN 0263-8231, E-ISSN 1879-3223, Vol. 49, no 4, p. 523-533Article in journal (Refereed)
    Abstract [en]

    This paper presents a corotational formulation of a three-dimensional elasto-plastic mixed beam element that can undergo large displacements and rotations. The corotational approach applies to a two-noded element a coordinate system which continuously translates and rotates with the element. In this way, the rigid body motion is separated out from the deformational motion. In this paper, a mixed formulation is adopted for the derivation of the local element tangent stiffness matrix and nodal forces based on a two-field Hellinger-Reissner variational principle. The local beam kinematics is based on a low-order nonlinear strain expression using Timoshenko assumption. The warping effects are characterized by adopting Benscoter theory that describes the warping degree of freedom by an independent function. Shape functions that satisfy the nonlinear local equilibrium equations are selected for the interpolation of the stress resultants. This local element, together with the corotational framework, can be used to analyze the nonlinear buckling and postbuckling of thin-walled beams with generic cross-section. The mixed formulation solution is compared against the results obtained from a corotational displacement-based formulation having the same beam kinematics. The superiority of the mixed formulation is clearly demonstrated.

  • 11. Alsafadie, Rabe
    et al.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Hjiaj, Mohammed
    Efficient local formulation for elasto-plastic corotational thin-walled beams2011In: The International Journal for Numerical Methods in Biomedical Engineering, ISSN 2040-7939, Vol. 27, no 4, p. 498-509Article in journal (Refereed)
    Abstract [en]

    A local elasto-plastic formulation, based on a low-order nonlinear strain expression using Bernoulli beam kinematics, is presented in this paper. This element, together with the corotational framework proposed in (Comput. Meth. Appl. Mech. Eng. 2002; 191(17): 1755-1789) can be used to analyze the nonlinear buckling and postbuckling of thin-walled beams with arbitrary cross-section. The formulation captures both the Saint-Venant and warping torsional effects of open cross-sections. Numerical examples show that this local formulation is more efficient than the one proposed in (Comput. Meth. Appl. Mech. Eng. 2002; 191(51):5811-5831) based on a Timoshenko beam assumption.

  • 12. Alsafadie, Rabe
    et al.
    Hjiaj, Mohammed
    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.
    Stability analysis for 3D frames using mixed corotational formulation2010In: SDSS-Rio 2010 Stability and ductility of steel structures / [ed] E. Batista, P. Vellasco, L. de Lima, 2010, p. 547-554Conference paper (Refereed)
    Abstract [en]

    The corotational technique is adopted for the analysis of 3D beams. The technique applies to atwo-noded element a coordinate system which continuously translates and rotates with the element. Inthis way, the rigid body motion is separated out from the deformational motion. Then, a mixedformulation is adopted for the derivation of the local element tangent stiffness matrix and nodal forces.The mixed finite element formulation is based on an incremental form of the two-field Hellinger-Reissnervariational principle to permit elasto-plastic material behavior. The proposed element can be used toanalyze the nonlinear buckling and postbuckling of 3D beams. The mixed formulation solution iscompared against the results obtained from a corotational displacement-based formulation having thesame beam kinematics. The superiority of the mixed formulation is clearly demonstrated.

  • 13. Alsafadie, Rabe
    et al.
    Hjiaj, Mohammed
    Structural Engineering Research Group, Université Européenne de Bretagne, Rennes, France.
    Somja, Hugues
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    A comparative study of displacement and mixed-based corotational finite element formulations for elasto-plastic three-dimensional beam analysis2011In: Engineering computations, ISSN 0264-4401, E-ISSN 1758-7077, Vol. 28, no 7, p. 939-982Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to present eight local elasto-plastic beam element formulations incorporated into the corotational framework for two-noded three-dimensional beams. These formulations capture the warping torsional effects of open cross-sections and are suitable for the analysis of the nonlinear buckling and post-buckling of thin-walled frames with generic cross-sections. The paper highlights the similarities and discrepancies between the different local element formulations. The primary goal of this study is to compare all the local element formulations in terms of accuracy, efficiency and CPU-running time.

  • 14.
    Alshathir, Bashar
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Fatigue of composite railway bridges based on dynamic simulations2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many steel and composite railway bridges were designed using static analysis and a dynamic amplification factor. These bridges are subjected at present time and in future, to more axel loads and higher train speeds which may reduce substantially fatigue service life at specific parts.

    The purpose of this study is to investigate two types of dynamic parameters to evaluate fatigue service life of the Banafjäl Bridge. It is structurally a composite railway bridge that is located in north of Sweden.

    One of the dynamic parameters is the speed of different types of high-speed train models which will influence the resonance speed and its impact on fatigue. In addition, the overall damping ratio of the structure is varied which has shown to have a significant effect on the fatigue life.

    Two dimensional finite element model was created to perform dynamic time history analyses which was utilizing load-time amplitude function. Two types of trains were used to simulate the bridge response dynamically. The model was verified with another study and the results were employed to evaluate the bridge in three critical welded connections with respect to fatigue.

    The results show that the speed of the trains has great impact on the fatigue life especially at resonance speed, and that an increase in the damping ratio will prolong the bridge service life. A comparison of fatigue life between dynamic and static analysis of a specific train type is also presented which shows large differences in results.

  • 15.
    Alà Salat, Ferran
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Critical shear buckling loads for I-girders with transverse web stiffeners2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 16.
    Amer, Wadi
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Soil Steel Composite Bridges: A comparison between the Pettersson-Sundquist design method and the Klöppel & Glock design method including finite element modelling2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 17.
    Amer, Wadi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Lars, Pettersson
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Structural response of a high profile arch flexible culvert in sloping terrain using finite element modeling2018Conference paper (Refereed)
    Abstract [en]

    Flexible culverts are generally considered cost-effective structures for their simplicity in construction and the short time involved in the erection process. This has constantly motivated practitioners to explore the different areas of application including their performance in sloping environment. Yet, the complex nature of the interaction between the soil and steel materials marks a challenge, where the performance of these structures is fundamentally influenced by the quality of the backfill soil and its configuration around the conduit/arch. Surface slopes may affect the structural response by inducing an asymmetrical soil support and an unbalanced earth loading.

    The use of numerical simulation is utilized to provide insights about the performance of flexible culvert in sloping environment, where a case study of a high profile arch is investigated under different construction schemes. The paper focuses mainly on predicting the structural behavior of soil loading effects. The study includes the influence of different slopes in combination with various depths of soil cover.

    The results enabled to realize the importance of soil configuration around the steel arch and its influence on the structural response. While the presence of surface slopes emphasizes the susceptibility of flexible culverts with low depths of soil cover, higher covers may help in reducing the effect of steep slopes. Sectional forces were found to increase with the increase of surface slopes. The study also highlighted recent research efforts on the topic and briefly discussed some design implications when building flexible culverts in sloping terrain.

  • 18.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Adaptive and semi-active vibration control of railway bridge dynamics2012Report (Other academic)
    Abstract [en]

    Long Life Bridges is a Marie Curie 7th Framework Project funded under the Industry and Academia Partnerships and Pathways call, Grant Agreement No. 286276. The Project commenced in September 2011 and is continuing for 4 years until August 2015. The project vision is to extend the service lives of bridges through development of advanced assessment methods. The author wishes to acknowledge the financial contribution by the European Commission in supporting the project and funding this research.

    The work presented in this report has been conducted at Roughan & O’Donovan Innovative Solutions, Dublin, Ireland, during the period of January to December 2012, under supervision of Associate Professor Alan O’Connor. The author has been seconded from the Royal Institute of Technology (KTH), Division of Structural Engineering and Bridges.

    Within the project, experimental work to develop a prototype damper has been carried out at Trinity College Dublin (TCD), Department of Civil, Structural and Environmental Engineering. A special thank goes to Dr. Kevin Ryan and the laboratory staff at the Department for the help in manufacturing and testing the prototype damper.

    Full-scale testing has been performed on a railway bridge in Sweden. The tests were funded directly by the Swedish Transport Administration (Trafikverket). The instrumentation and field measurements were performed by KTH in collaboration with the author.

    The work presented, denoted secondment 1.1b, deals with development of adaptive and semi-active damping systems for railway bridges. The aim of the project is to develop methods for structural vibration control with applications for railway bridge dynamics. Much of the work has been related to a case study bridge.

    There is constant demand on rail authorities to increase both the allowable axle loads and the allowable speed on existing railway lines. As an example, the Swedish Transport Administration has recently investigated the possibility of upgrading part of the main lines to allow for future high-speed trains. Some lines are also being investigated with the aim of allowing ore transports with higher axle loads and longer trains. A large portion of the bridge stock was designed for significantly lower axle loads and only very few have been designed to account for dynamic effects. Increased dynamic effects may result in exceedance of dynamic design criteria, reduced service life due to fatigue, or even failure. Through better quantification of risk, it is often possible to prove that speeds can be increased with no adverse effect. However, for bridges where the level of risk is too high, a cost-effective means of reducing dynamic effects on bridges are active and semi-active control system. Semi-active control is well established in other fields and could prove to be a beneficial technique to allow train speeds to be increased.

    The concept of structural vibration control is to attenuate the dynamic response of a structure by means of an external damping device. Due to changes in either loading or structural behaviour, the properties of the damper device may need to be changed to efficiently mitigate vibrations. Two main principles of damper devices are commonly used; tuned mass dampers and shock absorbers. Tuned mass dampers consist of a suspended mass mounted on the main structure. Due to a phase-shift, the vibration of the suspended mass partly counteracts the corresponding motion of the main structure. Changing the stiffness of the suspended mass results in a variable adaptive tuned mass damper. Shock absorbers rely on producing the counteracting force by means of increased viscous damping. Devices with variable viscous damping are often categorised as semi-active. Fully active systems rely on producing the counteracting force by means of a load actuator. Adaptive and semi-active systems generally require much less energy to operate compared to fully active systems.

  • 19.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Impact loading on concrete slabs: Experimental tests and numerical simulations2014Report (Other academic)
    Abstract [en]

    In this report, the load capacity of concrete slabs subjected to concentrated loads is studied, considering both the static load capacity and the response due to impact of a falling mass. The purpose of the study is to gain more knowledge on the static and dynamic behaviour of the slabs and to use that knowledge in the assessment of the load capacity of inner lining systems in tunnels. The methodology involves experimental testing of a series of slabs, validation of numerical models and simulating the response of the inner lining system.

    A total of 18 slabs were manufactured, consisting of shotcrete and reinforcement mesh. Some of the slabs also included steel fibre reinforced concrete (SRFC). The size of the slabs were 1.75×1.75×0.12 m, suspended in four hangers #1.2 m and loaded centric on an area of 0.2×0.2 m. In addition, a series of core samples and beams were cut from two of the slabs for material testing and verification of numerical models.

    From the static load tests of the slabs, the load at cracking was obtained at 50 – 60 kN with a vertical midpoint displacement of 0.6 – 1.0 mm. The ultimate load ranged from 60 – 80 kN. The slabs showed significant ductility with a peak displacement of about 70 – 80 mm at post-failure. All slabs showed a two-way flexural failure. The concrete cover was in average 30 mm, measured from the compressive side, resulting in little difference between the crack load and the ultimate load. A vertical displacement of about 1 – 2 mm was required to obtain a crack width of 0.2 mm. Three slabs with only SRFC were tested until static failure, the ultimate load ranged from 85 – 90 kN but with less ductility compared to the slabs with rebar mesh.

    Impact load tests were performed using a steel mass of 600 kg. The free fall height was varied from 1 – 2 m. The peak impact load varied from 200 – 250 kN, without any clear correlation with the height. The corresponding impulse load varied from 4.0 – 5.5 kNs with a clear correlation to the height. All slabs subjected to impact load showed a one-way flexural failure, the residual strength after impact was sufficient to carry the static load of the steel weight. Several of the slabs showed significant fallout of concrete during impact, in one extreme case a total of 16 kg. Three slabs were tested with an outer layer of 30 mm of SRFC, none of these slabs showed any significant fallout.

    The static and dynamic response of the slabs have been simulated using nonlinear FE-models. The models generally show good agreement, both for static load, crack widths and response during impact. Similar models were used to simulate the response of the inner lining system. The results indicate a significant load capacity, both due to static and impact loading. The models are however not able to account for potential punching failure.

  • 20.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Load capacity assessment and strengthening of a railway arch bridge with backfill2013Conference paper (Refereed)
    Abstract [en]

    In this paper, a load capacity assessment and strengthening measures of a multi-span railway arch bridge with backfill are presented. The bridge is located in Stockholm, Sweden, and constitute a vital link for the national railway network. The bridge consists of 20 concrete arches with overlying backfill, each with a span of 20 m. After more than 80 years of service, severe deterioration of the concrete was found during conditional assessments. A load capacity assessment was performed and the theoretical ultimate load was found to be highly dependent on the development of soil pressures along the arch barrel. The demands from the railway authority are to increase the allowable axle load from 22,5 to 25 tonnes and extend the service life by 50 years. Due to the uncertainties in structural behaviour and progressing degradation, extensive strengthening measures for the arch barrels were decided. To allow for full traffic at all times, the strengthening was performed in stages, to minimize any temporary reduction in load capacity due to removal of existing material. The strengthening was designed using non-linear finite element analysis and each stage of strengthening has been verified using in-situ field measurements.

  • 21.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Arvidsson, Therese
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Train-Track-Bridge Interaction for non-ballasted Railway Bridges on High-Speed Lines2017Report (Other academic)
    Abstract [en]

    This report contains a comprehensive parametric study on the coupled dynamic train–track–bridge interaction (TTBI) system for non-ballasted railway bridges. The existing design limits in Eurocode EN 1990 A2 regarding vertical deck acceleration and vertical deck displacement is compared with the wheel–rail forces and car body acceleration from simulations.

    The simulations are based on a 2D TTBI model with linear Hertzian contact that allows for loss of contact. The model has been verified against both other numerical simulations as well as experiments, all with good agreement. The parametric study consists of a large number of theoretical bridges, all optimized to reach the limit of either vertical deck acceleration or vertical deck displacement. The study comprises both single- and double track bridges.

    The track irregularities are found to be of paramount importance. Two different levels are therefore studied; “higher track quality” corresponding to a well-maintained track for high-speed railways and “lower track quality” corresponding to the Alert Limit in EN 13848-5. The final conclusions are based on the “lower track quality” in order not to underestimate the risk of running safety and passenger comfort. Simulations with the bridge excluded show that the additional contribution from the bridge is low, especially for the lower track quality.

    The existing limit for vertical deck acceleration is set to 5 m/s2 in EN 1990 A2 and is based on a very simple assumption of the gravity acceleration reduced by a factor 2. The results in this report show that this likely is a too conservative measure of the running safety. Based on the wheel–rail forces from the simulations, the resulting wheel unloading factor and duration of contact loss does not reach critical values before the deck acceleration is beyond 30 m/s2.

    In EN 1990 A2, a vertical car body acceleration of 1 m/s2 is stipulated as “very good level of comfort” and is indirectly limited by the vertical deck displacement. Good agreement is generally found in the simulations between deck displacement and expected car body acceleration. In the simulations, the limit for car body acceleration is always exceeded before the running safety is compromised.

  • 22.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Christoffer, Svedholm
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamisk kontroll av järnvägsbroar, inverkan av 3D-effekter2016Report (Other academic)
    Abstract [en]

    This report present result from dynamic analyses of railway bridges for high-speed trains. A comparison of the dynamic response in 2D vs. 3D has been performed for a limited selection of slab bridges, beam bridges and box girder bridges. Each cross-section has been optimized based on the dynamic requirements for dynamics in 2D, without any consideration of the static design. In many cases, the cross-section probably needs to be increased to fulfil the static load capacity.

    Slab bridges with a span length from 10 – 25 m and 1 – 4 spans have been analysed. In several cases, mostly for shorter spans, the natural frequency for bending is lower in 3D compared to 2D. The reason is due to a smaller contributing width, owing to shear-lag. This results in a lower resonance speed and therefore often a larger dynamic response within the same speed range. Apart from that, the dynamic response is found to be similar in 3D compared to 2D. The influence of torsional does not appear to be governing the response for the studied cases.

    Using the same method, beam bridges with span length from 20 – 40 m and 1 – 4 spans have been analysed. Similar to the slab bridges, the 3D-model of the beam bridges show lower natural frequency in bending compared to the 2D-model, owing to shear-lag. For double-track bridges, the difference in response between 2D and 3D-models are similar to the findings for the slab bridges. For single-track bridges, some cases of the 3D-model shows significantly lower response without pronounced resonance peaks in the same speed interval as the 2D-model. The reason is likely a combination of the support eccentricity and the mass of the bridge, which for vertical bending results in horizontal inertia. It is shown that this can be simulated with a modified 2D-model in most cases.

    Box girder bridges with span length from 40 – 70 m in 1 – 3 spans have also been analysed. Due to the larger torsional stiffness, the torsional mode is often much higher than the first bending mode. Also, the shear-lag effect seems to be smaller and the response from the 3D-model agrees well with the corresponding 2D-model.

    In the case dynamic assessment is performed using the simplified methods according to (Svedholm & Andersson, 2016), it is suggested that the following is considered:

    • Shear-lag and the eccentricity at the supports should be considered when estimating the first natural frequency for bending, n0, preferably using a 3D-model.

    • If the first torsional mode nT < 1.2n0, a full dynamic analysis in 3D should be performed.

    • In the case a 3D-model shows several closely spaced bending modes with similar shape, a full dynamic analysis in 3D should be performed.

  • 23.
    Andersson, Andreas
    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.
    Attenuating resonant behavior of a tied arch railway bridge using increased hanger damping2012In: Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management, Taylor & Francis Group, 2012, p. 2572-2577Conference paper (Refereed)
    Abstract [en]

    In this paper, dynamic analyses and field measurements of a tied arch railway bridge is presented. Excessive vibrations of the hangers were obtained, caused by resonance during train passages. The resulting increase of the stress level and number of stress cycles were shown to decrease the fatigue service life significantly. The most critical section is a threaded turnbuckle connection of the hangers. Due to low damping of the hangers, more than 50 % of the cumulative fatigue damage was related to free vibrations after train passage. Passive dampers were installed to attenuate the vibrations by means of increased damping. A combination of field measurements and numerical models are used to investigate the behavior of the bridge and the impact of increased hanger damping.

  • 24.
    Andersson, Andreas
    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.
    Dynamics of railway bridges, analysis and verification by field tests2015In: EVACES'15, 6th International Conference On Experimental Vibration Analysis For Civil Engineering Structures / [ed] Glauco Feltrin, EDP Sciences, 2015, Vol. 24Conference paper (Refereed)
    Abstract [en]

    The following paper discusses different aspects of railway bridge dynamics, comprising analysis, modelling procedures and experimental testing. The importance of realistic models is discussed, especially regarding boundary conditions, load distribution and soil-structure interaction. Two theoretical case studies are presented, involving both deterministic and probabilistic assessment of a large number of railway bridges using simplified and computationally efficient models. A total of four experimental case studies are also introduced, illustrating different aspects and phenomena in bridge dynamics. The excitation consists of both ambient vibrations, train induced vibrations, free vibrations after train passages and controlled forced excitation.

  • 25.
    Andersson, Andreas
    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.
    O'Connor, Alan
    Trinity College Dublin.
    Development of a multi-passive tuned mass damper, theory and experiments2014In: Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014, Porto, 2014, p. 1551-1556Conference paper (Refereed)
    Abstract [en]

    In this paper, a bi-directional multi-passive tuned mass damper is presented. The applicationfor the damper is on vertical hangers of an existing steel arch railway bridge.The hangers have been found susceptible to resonance and the resulting stressesresults in a reduced service life due to fatigue. Due to different boundaryconditions, the natural frequencies of the hangers are different in thelongitudinal and the transverse direction. In addition, the natural frequenciesincrease during train passage, due to increased tensile force in the hangers. Aprototype of the damper has been developed, consisting of two suspended massescoupled in series. Different lateral suspensions are used to obtain differentnatural frequencies in the longitudinal and the transverse direction. One massis tuned to the conditions of the fully loaded bridge and the other mass to theunloaded bridge. The performance of the damper is verified using controlledloading under laboratory conditions and the results are compared with a finiteelement model. The damper is shown to perform as expected and the motion of thetwo masses is near uncoupled. Finally, the performance of the damper isverified by in-situ testing on the case study bridge.

  • 26.
    Andersson, Andreas
    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.
    O'Connor, Alan
    External damping of stay cables using adaptive and semi-active vibration control2013In: Proceedings of the 8th International Cable Supported Bridge Operators Conference, Edinburgh, Scotland, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, the performances of different external damping systems for stay cables are studied based on numerical simulations. Two types of dampers have been analysed; a near anchorage viscous damper and a tuned mass damper (TMD) mounted near the midspan of the stay cable. For the passive case, both dampers are tuned to the fundamental mode of vibration of the cable. The optimal viscous damping for the near anchorage damper is determined based on well-known equations for a taut string. For the TMD, parametrical studies have been performed to determine the optimal damping ratio as function of the damper mass. The resulting vibration mitigation from the two systems are also studied for higher modes of vibration and the potential increase in performance using an adaptive or semi-active vibration control system is studied.

  • 27.
    Andersson, Andreas
    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.
    O'Connor, Alan
    Semi-active damping systems for railway bridges2012In: / [ed] Colin Caprani, Alan O'Connor, Dublin, 2012, p. 177-182Conference paper (Refereed)
    Abstract [en]

    In this paper, a semi-active control system for vibration mitigation of railway bridges is presented. The real time frequency response is estimated using a short-time Fourier transform, employing curve fitting to relevant peaks for increased accuracy. A control algorithm developed in Matlab® is linked to a commercial FE-software, facilitating application on arbitrary structures. A numerical study of an existing tied arch railway bridge is presented. From earlier field measurements and numerical analysis, resonance of several hangers during train passage was observed. This was shown to significantly reduce the fatigue service life of the hangers and for the most critical section about 50% of the cumulative damage was related to free vibrations. A system of passive dampers was later installed and the increase in resulting damping was measured. Within the present study, the previous results are reanalysed and compared with a semi-active approach. The natural frequencies of the hangers vary as a result of the variation in axial force. A semi-active control system has the potential to improve the vibration response of the structure when compared to the installed passive system.

  • 28.
    Andersson, Andreas
    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.
    O'Connor, Alan
    Vibration mitigation of railway bridges using adaptive damping control2013In: Assessment, Upgrading and Refurbishment of Infrastructures, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, the advantage of an adaptive damping system is presented. A damper with variable stiffness is tuned based on estimates of the real-time frequency response, facilitating optimal vibration mitigation. The performance of the developed routines is investigated on an existing tied arch railway bridge. Based on previous field measurements, resonant behaviour of several hangers was found. In combination with low structural damping, the induced stresses resulted in a reduced fatigue service life. Passive dampers are currently installed on the longer hangers, each tuned to the fundamental natural frequency of the individual hanger. However, increased axial force during train passage results in a significant variation in natural frequency, with an apparent risk of detuning the passive dampers. The predicted performance of an adaptive damping system to account for this variation in dynamic behaviour is presented and its potential application is discussed.

  • 29.
    Andersson, Andreas
    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.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Extending the fatigue service life of a railway bridge by local approaches2013Conference paper (Refereed)
    Abstract [en]

    In this paper, fatigue assessment of a steel railway bridge is presented. The bridge is located in central Stockholm, Sweden, and is one of the most vital links for the railway network. The bridge services both freight trains and commuter trains with more than 500 passages per day. The main load bearing structure is designed as a steel grillage of welded I-beams. Fatigue critical sections have been identified at locations where secondary bracing systems are welded to the flanges of the I-beams. Both numerical simulations and extensive field measurements have shown a significant exceedance of the theoretical fatigue service life. Based on analysis of local stress concentrations, improvement of fatigue critical details have been suggested. The decrease in stress concentration is demonstrated both by numerical simulations and in-situ field measurements and shows a significant improvement when estimating the remaining fatigue service life.

  • 30.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Development and testing of a bi-directional multi-passive tuned mass damperIn: Computer-Aided Civil and Infrastructure Engineering, ISSN 1093-9687, E-ISSN 1467-8667Article in journal (Other academic)
    Abstract [en]

    This paper presentsthe development and testing of a bi-directional multi-passive tuned mass damper(bi-MTMD). A prototype of the damper has been built and tested under laboratoryconditions. The damper was developed for application to a vertical hanger on anexisting tied-arch railway bridge. During train passage, resonance has beenobserved in several hangers, resulting in a reduction in the predicted fatigueservice life. The objective of the damper is to mitigate the vibrations toreduce the resulting stresses and consequently to extend the life of thehanger. The hanger has different natural frequencies for longitudinal andtransversal bending. In addition, a significant difference in natural frequencyis obtained for the loaded and unloaded bridge, due to the increase in axialforce in the hangers. The developed damper accounts for both scenarios and istuned based on previous field measurements. The results from the laboratoryexperiments are compared with a 3D FE-model of the damper.

  • 31.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Development of a Bi-directional Multi-Passive Tuned Mass DamperIn: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541XArticle in journal (Refereed)
    Abstract [en]

    This paper presents the development and testing of a bi-directional multi-passivetuned mass damper (bi-MTMD). A prototype of the damper has been built andtested under laboratory conditions. The damper was developed for application toa vertical hanger on an existing tied-arch railway bridge. During trainpassage, resonance has been observed in several hangers, resulting in areduction in the predicted fatigue service life. The objective of the damper isto mitigate the vibrations to reduce the resulting stresses and consequently toextend the life of the hanger. The hanger has different natural frequencies forlongitudinal and transversal bending. In addition, a significant difference innatural frequency is obtained for the loaded and unloaded bridge, due to theincrease in axial force in the hangers. The developed damper accounts for bothscenarios and is tuned based on previous field measurements. The results fromthe laboratory experiments are compared with a 3D FE-model of the damper.

  • 32.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Swedish Transport Adm Trafikverket, Solna, Sweden.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Passive and Adaptive Damping Systems for Vibration Mitigation and Increased Fatigue Service Life of a Tied Arch Railway Bridge2015In: Journal of Bridge Engineering, ISSN 1084-0702, E-ISSN 1943-5592, Vol. 30, no 9, p. 748-757Article in journal (Refereed)
    Abstract [en]

    n this article, the use of external damping systems for vibration mitigation of railway bridge dynamics is studied. For a presented case study bridge, the performance of different tuned mass damper systems (TMDs) is studied. During train passage, the change in dynamic characteristics of the bridge may produce a significant detune to a passive TMD. Therefore, routines for a variable stiffness TMD using incremental frequency estimates are developed. Based on numerical simulations, the cumulative fatigue damage is calculated for different damper systems. Due to resonant behavior, the results are found to highly depend on the train speed. Based on an assumed probability density function for the train speed, fragility curves are produced to express the probability of fatigue failure as a function of the number of train passages.

  • 33.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Roslin, Mattias
    Trafikverket.
    Load capacity of inner lining system s due to impact from falling rocks2015In: SEE Tunnel: Promoting Tunneling in SEE Region / [ed] Davorin Kolic, Dubrovnik, 2015Conference paper (Other academic)
    Abstract [en]

    The inner lining concept is a method to prevent water leakage and the risk of icing inside tunnels and is frequently used in countries with cold climate. Blocks of falling ice may result is a severe safety risk in both road and railway tunnels. Although several established inner lining systems exist, finding the optimal solution considering function, maintenance- and investment cost is a challenging task. A new system has recently been used in Sweden and is due to its success planned to be used for the Stockholm Bypass, an 18 km road tunnel project in Stockholm.

    A set of design criterions has been stipulated for the inner lining system. In this paper, the case of impact loading from falling rocks is studied. The inner lining system is required to withstand the impact of a 600 kg block landing on a square surface of 0.2x0.2 m. The free fall height, i.e. the distance to the rock surface, is typically less than 0.5 m but may span up to 1.5 m in some cases. A too conservative design may result in an unnecessary thick structure and lack of knowledge of the impact phenomena may result in an unsafe design.

    An extensive experimental program has been performed, consisting of representative parts of the inner lining system. A mass of 600 kg is dropped onto the structure and the results are compared with numerical simulations. The experiments show that the current system is rather ductile but that local concrete fallouts may occur at extreme free fall heights.

  • 34.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Roslin, Mattias
    Trafikverket.
    Taube, Arvid
    Trafikverket.
    Bärförmåga hos inklädnadssystem vid stödbelastning från fallande bergblock2015In: Bergmekanikdag 2015 / [ed] BeFo, Stockholm: Stiftelsen Bergteknisk forskning , 2015Conference paper (Other academic)
    Abstract [en]

    Inner lining system in tunnels is a method to prevent water ingress and forming of ice in the traffic area. A solution that is common in Norway is based on stretching a sealing membrane between rock anchorages that forms a gap to the primary rock strengthening. The membrane is in turn protected by a layer of shotcrete towards the traffic area. The rock strengthening is designed to resist all loads from the rock mass independent of the inner lining system. A problem is however how to perform inspections and conditional assessment of the rock strengthening, since the gap is usually small. Other topics are what loads the inner lining system should be designed for. In TRVK Tunnel 11, the load of a local falling rock of 600 kg is stipulated, assuming to act on a surface of 0.2×0.2 m. Furthermore, the inner lining system should be designed to resist what is connoted as an extreme rock load of 6 metric ton, acting on a 1×1 m area, even when a primary rock strengthening is present. Similar inner lining systems have been used in e.g. Norra länken, parts of Citybanan in Stockholm and is planned to be used for the Stockholm Bypass project.

    In the present paper, results from a recent research project are presented, aiming at investigating the structural manner of action of the aforementioned inner lining system. A series of concrete slabs have been tested, both until static failure and with a 600 kg drop weight from different heights. All tested slabs resulted in flexural failure and showed a significant ductility. For several of the slabs tested for impact loading, significant spalling from the soffit was obtained, at the most corresponding to a mass of 16 kg. Three of the slabs tested for impact load were manufactured with an outer layer of steel fibre reinforced shotcrete. None of these slabs showed any significant spalling, despite a free fall height up to 2 m.

    Several FE-analyses have also been performed, accounting for the nonlinear material properties of concrete. The results showed good agreement with the conducted experiments, both regarding static loading, cracking and impact load. A similar analysis was also done for the whole inner lining system. The results showed a larger load capacity compared to the experiments, but still with a rather localised failure.

  • 35.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Sundquist, Håkan
    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 Tests and Structural Evaluation of Soil-Steel Flexible Culverts for High-Speed Railways2012In: Second European conference on Buried Flexible Steel structures Rydzyna April 23rd – 24th 2012, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper, results from full-scale tests on a corrugated soil-steel flexible culvert for railway traffic are presented. The bridge was instrumented with strain gauges, accelerometers and displacement gauges, measuring the response from passing trains. The aim of the measurement campaign was to gain knowledge of the dynamic behaviour due to train induced vibrations, both of the bridge structure and the overlying railway embankment. From the measured data, the load distribution and soil-stiffness can be estimated. The results also serve as input for calibration of numerical models that are used for predicting the behaviour due to high-speed trains.

  • 36.
    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.

  • 37.
    Andersson, Jenny
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Widening of The Nockeby Bridge: Methods for strengthening the torsional resistance2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    i Abstract The Nockeby Bridge, in the western part of Stockholm, is a prestressed concrete bridge with an openable swing span of steel. The bridge was built during 1970 and should now be widened with 0.5 meters on each side. The concrete bridge deck is supported by two main-beams and cross-beams are located at the position of all supports. Previous studies of the bridge show that the torsional resistance is too low and the bridge needs strengthening while widened. The aim of this master  thesis  was  to  study  and  compare  different  strengthening  methods  for  The  Nockeby Bridge.  Eight  different  bridges  in  Sweden  and  China  were  reviewed  to  find  possible  strengthening  methods  for  The  Nockeby  Bridge.  External  prestressing  tendons  and  additional  cross-beams between  the  two  main-beams  were  seen  to  have  good  influence  on  the  resistance.  The  effect from strengthening with carbon-fiber reinforced polymer was questioned during small loads and was not seen as a suitable strengthening method for The Nockeby Bridge.  Four different FE-models were generated to be able to compare two strengthening methods. The compared strengthening methods were a method with additional cross-beams between the main-beams and a method with external prestressing tendons. All FE-models were built up by solid- and  truss  elements  where  the  concrete  was  modelled  with  solid  elements  and  the  prestressed reinforcement was modelled with truss elements.  Only a few load-cases were included to limit the scope of the study. The included load-cases were deadweight,  prestressing  forces  and  vehicle  load  from  standard  vehicle  F,  G,  H  and  I.  Two influence lines were created to be able to place the vehicle loads in an unfavorable way. From the FE-models, shear  stresses were  extracted  along two  lines, one  on  each  side  of the main-beam. The torsional part of the shear stresses was calculated from these two results and compared with the torsional resistance of the bridge. While calculating the torsional resistance, the normal force in the cross-section from prestress was extracted with the function “free body cut”. The results showed that none of the tested strengthening methods were enough to  strengthen The  Nockeby  Bridge.  However, the  method  with additional  cross-beams  was  seen  as  a  better method than external prestressing tendons. A combination of the two methods might be suitable but  was  not  tested.  Adding  four  cross-beams  in  each  span  might  also  increase  the  resistance enough, but this was neither tested. It was also seen that a reduction of the torsional stiffness had a large influence on the result. Such a reduction is allowed in some cases and should be utilized if possible. Furthermore,  it  was  seen  that  solid-models  were  extremely  time  consuming  and  there  is  not  a  good alternative to design a bridge with only a solid model.

  • 38.
    Andersson, Linda
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Klingsmo, Maria
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Mellanstödslös bro över motorväg- i högpresterande betong med extern förspänning2004Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 39.
    Andersson, Lisa
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamics of staircases: A case study to improve finite element modeling2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Vibrations in staircases have during the last decades become an important issue in design. The main reasons are current architectural trends aiming for innovative, slender and high staircases, together with developments in material properties and building technique, making these aims possible. The improved material properties and slender design of the staircase makes the structure lightweight and have great impact on the flexibility and dynamic performance of the staircase. This have resulted in that vibration serviceability criteria increasingly often are becoming governing in design.

    The performance of staircases in serviceability under dynamic loads is however very hard to predict. In many cases hand calculations will not be sufficient, and a computerized model, e.g. a finite element model, need to be created. Creating a finite element model that performs well when subjected to dynamic loads is however not simple. Especially boundary conditions, connections and the effect of non-structural elements are hard to adequately represent. The formulation of the load is also a complex question. The main dynamic load that staircases are subjected to, that causes uncomfort for the user, is the load that the user themselves apply on the structure, when ascending or descending. 

    The main part of this master thesis project is a case study of two lightweight, steel staircases. To form a basis for the case study, current research have been summarized in a literature survey. An introduction of elementary dynamics is also made for less conversant reader.

    The literature survey reviews previous research about loads introduced by humans and how these can be formulated, both for single human excitation and group loading. How vibrations arise and how humans percept vibrations is also reviewed. The view and recommendations of standards and regulations about load formulation and vibration acceleration limits is presented. Recommendations in research for finite element modeling of staircases and dynamic loads is also reviewed.

    The case study consists of measurements and analyzing of finite element models of the staircases. Measurements of vibrations and the dynamic response of the staircases under human introduced loads have been conducted. The human introduced loads included are an impulse load created by a jump, ascent at a moderate pace of a single subject and descent at a moderate pace by a single subject. The measurements have been recreated in finite element models. Different modeling choices and formulations for ascending, descending, and impulse loads are studied. 

    The aim is to investigate how different modeling choices in connections, boundary conditions and adjacent structure, affects the natural frequencies and mode shapes of the staircase. Different load formulations for the loads are analyzed, both for the impulse load and for the loads created by a subject ascending and descending. With these results as a basis, some general recommendations about construction a finite element mode of a staircase and achieving appropriate load formulation for dynamic loads are made. 

  • 40.
    Andersson, Mattias
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Hagersten, Elsa
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Optimal viscous dampers targeting multiple cable modes with FEM2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis presents a study of the mitigation of rain-wind induced vibrations on horizontal cables using viscous dampers considering multiple modes. Software based on finite

    elements is developed which finds the optimal damping coefficient. This software uses a graphical user interface to facilitate the damper design process. In addition to this, the

    maximum vertical and rotational displacements have also been studied to observe the mitigation of the maximum amplitudes with increasing damper coefficient.

    The model is based on already known research, and the results are verified by comparing with case studies. The program uses both the Logarithmic Decrement method and the Half-Power Bandwitdh method to obtain the damping ratios.

    From this master thesis the following can be deduced:

    -The optimal modal damping will give the lowest maximum amplitudes.

    - The maximum vertical displacements may be interesting when considering alternative ways to optimize the damper coefficient and location.

    -The angular change delta (Δ) above the damper, increases with increasing damping coefficient.

  • 41.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Holmgren, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Mundt, Elisabeth
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Silfwerbrandt, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    State-of-the-art och förslag till forskningsprojekt: Drift, underhåll och reparation av trafiktunnlar2007Report (Other academic)
  • 42.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Holmgren, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Norlin, Bert
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Grunder för konstruktion med betong, stål och trä2006Report (Other academic)
  • 43.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Racutanu, George
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    A Markov approach in estimating the service life of bridge elements in Sweden2002In: 9th International Conference on Durability of Building Materials and Components, CSIRO Australia , 2002, p. 142-143Conference paper (Other academic)
  • 44.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Sprängavstånd till ung gjuten och sprutad betong2007Report (Other academic)
  • 45.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Racutanu, George
    Nedbrytningsmodeller för broelement, etapp 12001Report (Other academic)
  • 46. Arvidsson, T.
    et al.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Modelling alternatives in the dynamic interaction of freight trains and bridges2014In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 104Article in journal (Refereed)
    Abstract [en]

    This paper focuses on studying the dynamic response of bridges under passing freight trains. To increase transport efficiency, infrastructure mangers are asked to allow for higher freight train speeds and higher axle loads. However, little work has been done on the influence of increased freight train speeds on bridges. In this paper a two-level factorial experiment was used to identify the most important factors in train-bridge interaction systems comprising the Swedish Steel Arrow freight train passing over simply supported beam bridges. Thereby, the effect of a simple 2D multibody model as opposed to moving forces was set in relation to variations in other key system parameters. Preceding the factorial experiment, four train models were compared to determine a relevant vehicle idealisation. Through the factorial design, effects of single parameters, as well as joint effects from simultaneous changes in several parameters, were evaluated. The type of load model was found to have a large effect, reducing the bridge deck response at resonance considerably for the four studied bridges of span 6, 12, 24 and 36 m. For the relatively light 24 and 36 m span bridges, clear resonance peaks from heavy freight train passages in the speed interval 50-150 km/h were much reduced.

  • 47.
    Arvidsson, Therese
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Train–Bridge Interaction: Literature Review and Parameter Screening2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    New railway lines are continuously being constructed and existing lines are upgraded. Hence, there is a need for research directed towards efficient design of the supporting structures. Increasingly advanced calculation methods can be motivated, especially in projects where huge savings can be obtained from verifying that existing structures can safely support increased axle loads and higher speeds.

    This thesis treats the dynamic response of bridges under freight and passenger train loads. The main focus is the idealisation of the train load and its implications for the evaluation of the vertical bridge deck acceleration. To ensure the running safety of train traffic at high speeds the European design codes set a limit on the vertical bridge deck acceleration. By considering the train–bridge interaction, that is, to model the train as rigid bodies on suspension units instead of constant moving forces, a reduction in bridge response can be obtained. The amount of reduction in bridge deck acceleration is typically between 5 and 20% for bridges with a span up to 30 m. The reduction can be higher for certain train–bridge systems and can be important also for bridge spans over 30 m. This thesis aims at clarifying for which system parameter combinations the effect of train–bridge interaction is important.

    To this end, a thorough literature survey has been performed on studies in train–track–bridge dynamics. The governing parameters in 2D train–bridge systems have been further studied through a parameter screening procedure. The two-level factorial methodology was applied to study the effect of parameter variations as well as the joint effect from simultaneous changes in several parameters. The effect of the choice of load model was thus set in relation to the effect of other parameter variations.

    The results show that resonance can arise from freight train traffic within realistic speed ranges (< 150 km/h). At these resonance peaks, the reduction in bridge response from a train–bridge interaction model can be considerable.

    From the screening of key parameters it can furthermore be concluded that the amount of reduction obtained with a train–bridge interaction model depends on several system parameters, both for freight and passenger train loads. In line with the European design code’s guidelines for dynamic assessment of bridges under passenger trains an additional amount of damping can be introduced as a simplified way of taking into account the reduction from train–bridge interaction. The amount of additional damping is today given as function of solely the bridge span length, which is a rough simplification. The work presented in this thesis supports the need for a refined definition of the additional damping.

  • 48.
    Arvidsson, Therese
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Train–Track–Bridge Interaction for the Analysis of Railway Bridges and Train Running Safety2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, train–track–bridge interaction (TTBI) models are used to study the dynamic response of railway bridges. A TTBI model considers the dynamics of the train in addition to that of the track–bridge system. The TTBI model enables the assessment of train running safety and passenger comfort. In the bridge design stage, a moving force model is instead typically used for the train load. The main aim of this thesis is to use results from TTBI models to assess the validity of some of the Eurocode design criteria for dynamic analysis of bridges.

    A 2D rigid contact TTBI model was implemented in ABAQUS (Paper II) and in MATLAB (Paper III). In Paper V, the model was further developed to account for wheel–rail contact loss. The models were applied to study various aspects of the TTBI system, including track irregularities. The 2D analysis is motivated by the assumption that the vertical bridge vibration, which is of main interest, is primarily dependent on the vertical vehicle response and vertical wheel–rail force.

    The reduction in bridge response from train–bridge interaction was studied in Papers I–II with additional results in Part A of the thesis. Eurocode EN 1991-2 accounts for this reduction by an additional damping Δζ. The results show that Δζ is non-conservative for many train–bridge systems since the effect of train–bridge interaction varies with various train–bridge relations. Hence, the use of Δζ is not appropriate in the bridge design stage.

    Eurocode EN 1990-A2 specifies a deck acceleration criterion for the running safety at bridges. The limit for non-ballasted bridges (5 m/s2) is related to the assumed loss of contact between the wheel and the rail at the gravitational acceleration 1 g. This assumption is studied in Paper V based on running safety indices from the wheel–rail force for bridges at the design limit for acceleration and deflection. The conclusion is that the EN 1990-A2 deck acceleration limit for non-ballasted bridges is overly conservative and that there is a potential in improving the design criterion.

  • 49.
    Arvidsson, Therese
    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.
    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.
    Train running safety on non-ballasted bridgesManuscript (preprint) (Other academic)
    Abstract [en]

    The train running safety on non-ballasted bridges is studied based on safety indices from the vertical wheel–rail forces. A 2D train–track–bridge interaction model that allows for wheel–rail contact loss is adopted for a comprehensive parametric study on high-speed passenger trains. The relation between bridge response and vehicle response is studied for more than 200 theoretical bridges in 1–3 spans. The bridge's inuence on running safety and passenger comfort is differentiated from the influence of the track irregularities. The Eurocode bridge deck acceleration limit for non-ballasted bridges is 5 m/s2 based on the assumed derailment risk at 1g from wheel–rail contact loss. This study shows that the running safety indices are not compromised for bridge accelerations up to 30 m/s2. Thus, accelerations at 1g do not in itself lead to contact loss and there is potential to enhance the Eurocode safety limits for non-ballasted bridges.

  • 50.
    Arvidsson, Therese
    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.
    Modelling Alternatives in the Dynamic Interaction of Freight Trains and Bridges2014In: Proceedings of the Second International Conference on Railway Technology: Research, Development and Maintenance, 2014Conference paper (Refereed)
    Abstract [en]

    This paper focuses on studying the dynamic response of bridges under passing freight trains. To increase transport efficiency, infrastructure mangers are asked to allow for higher freight train speeds and higher axle loads. However, little work has been done on the influence of increased freight train speeds on bridges. In this paper a two-level factorial experiment was used to identify the most important factors in train-bridge interaction systems comprising the Swedish Steel Arrow freight train passing over simply supported beam bridges. Thereby, the effect of a simple 2D multibody model as opposed to moving forces was set in relation to variations in other key system parameters. Preceding the factorial experiment, four train models were compared to determine a relevant vehicle idealisation. Through the factorial design, effects of single parameters, as well as joint effects from simultaneous changes in several parameters, were evaluated. The type of load model was found to have a large effect, reducing the bridge deck response at resonance considerably for the four studied bridges of span 6, 12, 24 and 36 m. For the relatively light 24 and 36 m span bridges, clear resonance peaks from heavy freight train passages in the speed interval 50-150 km/h were much reduced.

1234567 1 - 50 of 534
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • 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