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  • 1.
    Aagah, Orod
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Aryannejad, Siavash
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Dynamic analysis of soil-steel composite railway bridges: FE-modeling in Plaxis2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.
    Abdihakim Ali, Mohamed
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Henriksson, André
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Comparison between high strength steel and conventional steel regarding the overall material usage for a composite bridge2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Structural steels are among the most widely used materials in the constructionsector, of which S355 is the steel that is considered being the norm in Europetoday. As the demands on civil engineering structures are increasing today parallelwith the construction sector intending to become a more environmentalfriendly industry, high strength steel (HSS) has become increasingly relevanttoday with the aim of reducing the material usage and facilitate a more sustainableconstruction. HSS is structural steel with a very high yield strength andultimate strength. In this dissertation, structural steels with a yield strengthof 500MPa or above were classified as HSS.In this thesis, the main steel girders of the E4 bridge over the Vapelbäcken,which is a continuous steel-concrete composite highway bridge, were optimizedwith HSS S690 and conventional structural steel S355 in order to investigatehow HSS affects the material usage for the bridge compared to the conventionalsteel. In addition to the above, a cost analysis, modal analysis and a fatigueassessment of bridge were carried out in order to analyse how the mass changedue to HSS affects the material cost of the bridge as well as the bridge’s dynamicproperties and fatigue resistance.The main girders of the bridge were optimized with respect to the ultimatelimit state (ULS). The optimization initiated with a structural analysis of thebridge using the finite element software Abaqus. Design calculations were thenperformed for the girders in accordance with the Eurocodes. Afterwards, thecross-sections of the main girders were optimized. When the optimization wascompleted, a cost analysis, modal analysis and the fatigue assessment wereperformed for the bridge.The optimization showed that HSS significantly reduces the material usagecompared to conventional steel if the optimization takes place with respect tothe ULS. The cost analysis showed that the bridge with optimized main girdersof HSS was the cheapest option, indicating that HSS can be a more economicalalternative than conventional structural steel if the material reduction is largeenough.The large material reduction that HSS entails led to deterioration of the bridge’sother properties. The modal analysis showed that the bridge with optimizedgirders of HSS was had the lowest natural frequency, indicating that the largemass reduction of the bridge due to HSS results in a impairing of the bridge’sdynamic properties since a large mass reduction impairs the stiffness of thestructure which in turn decreases the natural frequency. The fatigue assessmentshowed that the bridge with optimized girders of HSS had the lowestfatigue capacity, which means that the yield strength of the material does nothave an impact on the fatigue capacity and therefore the benefits of HSS cannotbe exploited in cases where fatigue governs the structural design.

  • 3.
    Abdulrahman, Keiwan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Potrus, Fadi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Numerical analysis and model updating of a steel-concrete composite bridge: Parametric study & Statistical evaluation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 4.
    Aboutalebi, Ghareman
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Optimering av fackverksstolpar med konisk eller parallell form2005Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 5.
    Acar, Yalda
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Jingstål, Pontus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Influence of the Non-linear Effects in the Design of Viscous Dampers for Bridge Cables2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 6. Aggestam, E.
    et al.
    Nielsen, J. C. O.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. Swedish Transport Administration, Solna, SE-171 54, Sweden.
    Li, M.
    Multi-objective design optimisation of transition zones between different railway track forms2018Inngår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018, TU Delft , 2018, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The vertical dynamic interaction between vehicle and railway track is simulated in the time domain using an extended state space vector approach. The track model includes a transition zone between slab track on a bridge and ballasted track on an embankment. By considering a multi-objective optimisation problem, solved using a genetic algorithm, selected vehicle and track responses are simultaneously minimised by optimising the distributions of rail pad stiffness and sleeper spacing in the transition zone. It is shown that the magnitudes of the maximum dynamic loads in the optimised transition zone can be reduced to be similar as the magnitudes far away from the transition zone.

  • 7.
    Ahne, Alexander
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Wikforss, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Projektering av brandskydd för stålkonstruktioner2005Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 8.
    Akhondi, Mehdi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Pelletäppan, tennishall med bristfällig konstruktion: En fallstudie av massiv limträkonstruktion2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 9.
    Al-Djaber, Jafar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Prestressed glue laminated beams reinforced with steel plates: Comparison between prestressed, reinforced and non-reinforced glue laminated beams according to the Eurocode and the Swedish annex2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The paper presents details of a numerical analysis and simplified construction of strengthened glue laminated beams. Glue laminated beams are strengthened through the use of steel reinforcements embedded between the lamellas of the beams. The study compares the numerical results from reinforced and prestressed beams, simply reinforced beams and non-modified beams. Parametric studies were undertaken to evaluate the effects on reinforcement thickness, beam span, prestressing force and prestressing loss. Modified and prestressed beams with wide spans and large dimensions had a significantly higher design load compared to non-modified beams with similar geometry and span. In the most beneficial cases, a load increase of 438% was observed for point load at midspan and 346% for uniformly distributed load.

  • 10. Alhasawi, Anas
    et al.
    Heng, Piseth
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. Université Européenne de Bretagne, France.
    Hjiaj, Mohammed
    Guezouli, Samy
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggteknik och design.
    Co-rotational planar beam element with generalized elasto-plastic hinges2017Inngår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 151, s. 188-205Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11. Alsafadie, R.
    et al.
    Battini, Jean -Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Somja, H.
    Hjiaj, M.
    Local formulation for elasto-plastic corotational thin-walled beams based on higher-order curvature terms2011Inngår i: Finite elements in analysis and design (Print), ISSN 0168-874X, E-ISSN 1872-6925, Vol. 47, nr 2, s. 119-128Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 12. Alsafadie, R.
    et al.
    Hjiaj, M.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Corotational mixed finite element formulation for thin-walled beams with generic cross-section2010Inngår i: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 199, nr 49-52, s. 3197-3212Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 13. Alsafadie, R.
    et al.
    Hjiaj, M.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Three-dimensional formulation of a mixed corotational thin-walled beam element incorporating shear and warping deformation2011Inngår i: Thin-walled structures, ISSN 0263-8231, E-ISSN 1879-3223, Vol. 49, nr 4, s. 523-533Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 14. Alsafadie, Rabe
    et al.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Hjiaj, Mohammed
    Efficient local formulation for elasto-plastic corotational thin-walled beams2011Inngår i: The International Journal for Numerical Methods in Biomedical Engineering, ISSN 2040-7939, Vol. 27, nr 4, s. 498-509Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 15. Alsafadie, Rabe
    et al.
    Hjiaj, Mohammed
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Stability analysis for 3D frames using mixed corotational formulation2010Inngår i: SDSS-Rio 2010 Stability and ductility of steel structures / [ed] E. Batista, P. Vellasco, L. de Lima, 2010, s. 547-554Konferansepaper (Fagfellevurdert)
    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.

  • 16. Alsafadie, Rabe
    et al.
    Hjiaj, Mohammed
    Structural Engineering Research Group, Université Européenne de Bretagne, Rennes, France.
    Somja, Hugues
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    A comparative study of displacement and mixed-based corotational finite element formulations for elasto-plastic three-dimensional beam analysis2011Inngår i: Engineering computations, ISSN 0264-4401, E-ISSN 1758-7077, Vol. 28, nr 7, s. 939-982Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 17.
    Alshathir, Bashar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Fatigue of composite railway bridges based on dynamic simulations2012Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    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.

  • 18.
    Alà Salat, Ferran
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Critical shear buckling loads for I-girders with transverse web stiffeners2006Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 19.
    Amer, Wadi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    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 poäng / 30 hpOppgave
  • 20.
    Amer, Wadi
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Lars, Pettersson
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Structural response of a high profile arch flexible culvert in sloping terrain using finite element modeling2018Konferansepaper (Fagfellevurdert)
    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.

  • 21.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Adaptive and semi-active vibration control of railway bridge dynamics2012Rapport (Annet vitenskapelig)
    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.

  • 22.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Dynamic analysis of simply supported slab bridges2019Rapport (Annet vitenskapelig)
    Abstract [en]

    This report present results from simulations of simply supported concrete slab bridges for railway traffic. The geometry follows the Swedish standard deck models according to design drawing B2447-2 and B2447-8, with span lengths ranging from 2-8 m. For each bridge four different configurations are studied; straight or skewed bridge deck and short or long edge beams. In addition, a case of higher mass due to increased ballast depth is studied. In total 78 different bridge configurations are included.

    According to the numerical models the first natural frequency range from about 15-80 Hz depending on span length and configuration. In all simulations the first three modes of vibration are included. The limit criteria is a peak deck acceleration of 3.5 m/s2 when loaded by the HSLM-A train model. Including a speed safety factor 1.2 according to EN 1991-2 results in an allowable speed that range from 175-350 km/h depending on the bridge configuration. The allowable speed is somewhat higher for the skewed bridges compared to straight bridges. Increased mass results in lower acceleration but also lower resonance speed. An increase in ballast depth from 0.6 to 1.2 m generally results in lower allowable speed, except for the shortestbridges in the study.

    It should be noted that the above conclusions are based only on simulations. Before upgrading these bridges to speeds higher than 200 km/h experimental validation is recommended. On the other hand, most existing real trains are likely to result insignificantly lower dynamic response compared to the HSLM-A trains.

  • 23.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Impact loading on concrete slabs: Experimental tests and numerical simulations2014Rapport (Annet vitenskapelig)
    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.

  • 24.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Load capacity assessment and strengthening of a railway arch bridge with backfill2013Konferansepaper (Fagfellevurdert)
    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.

  • 25.
    Andersson, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Simplified approach to dynamic analysis of railway bridges for high-speed trains2018Rapport (Annet vitenskapelig)
    Abstract [en]

    In this report the analysis of 278 existing railway bridges is presented. The aim is to investigate how many of these bridges that potentially can be upgraded to higher speeds, with a target of 250 km/h. Due to the vast amount of bridges and the limited resources, the analyses are performed using simplified 2D models. The analysis is afflicted with several uncertainties, both regarding input parameters as well as model uncertainties. The results should therefore be interpreted carefully and primarily serve as an indicator for which bridges that may or may not meet the requirements. Large uncertainties are especially expected for portal frame bridges due to its inherently large interaction with the surrounding embankment and 3D behaviour.

    The results from the analysis show that a total of 22 bridges theoretically fail to meet the dynamic requirements. A combination of refined analysis and experimental validation is recommended to better assess the dynamic response for these bridges. Among the most critical cases are several steel-concrete composite bridges, that due to a combination of low mass and low natural frequency may be prone to resonant loading. Retrofitting with external dampers may for some bridges be a viable solution.

  • 26.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Arvidsson, Therese
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Train-Track-Bridge Interaction for non-ballasted Railway Bridges on High-Speed Lines2017Rapport (Annet vitenskapelig)
    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.

  • 27.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Arvidsson, Therese
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Train-Track-Bridge Interaction for non-ballasted Railway Bridges on High-Speed Lines2018Inngår i: Railways 2018, 2018Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper presents the result from a parametric study of the dynamic response of railway bridges during train passage. A 2D coupled train-track-bridge interaction (TTBI) model is used to calculate the response from both the bridge and the vehicle.

    To assure traffic safety and riding comfort, Eurocode EN 1990/A2 gives a set of design limits for railway bridges on high-speed lines. The vertical bridge deck acceleration and displacement are often of main interest. For bridges with non-ballasted tracks the vertical deck acceleration is limited to 5 m/s2, simply obtained as the gravity divided by a safety factor 2, under the assumption that loss of wheel-rail contact will occur at 1g. The vertical bridge deck displacement is an implicit measure to assure riding comfort, based on a limited set of simulations carried out in the 1980ies and 1990ies.

    The main aim of this paper is to study the relation between the vertical bridge deck acceleration and the risk of derailment as well as the relation between the vertical deck displacement to the riding comfort. The risk of derailment is estimated both as a wheel-unloading factor based on the filtered wheel-rail contact forces or as the duration of contact loss based on the unfiltered wheel-rail contact forces.

    A large set of theoretical bridges are studied, all optimised to reach the design limits according to EN 1990/A2 for either vertical bridge deck acceleration or displacement. The results show that there is no risk of derailment until the deck acceleration exceeds 30 m/s2. Based on the present parametric study, it appears that the current limit for vertical deck acceleration of non-ballasted railway bridges is very conservative but that the limits for vertical deck displacement is in the correct order of magnitude. It is further concluded that the magnitude of rail irregularities is of great importance, often causing larger dynamic response in the vehicle than due to the vibration of the bridge.

  • 28.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Christoffer, Svedholm
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Dynamisk kontroll av järnvägsbroar, inverkan av 3D-effekter2016Rapport (Annet vitenskapelig)
    Abstract [sv]

    I föreliggande rapport redovisas dynamiska analyser av järnvägsbroar för höghastighetståg. En jämförelse i dynamisk respons mellan 2D- och 3D-modeller har utförts för ett mindre urval av plattbroar, balkbroar och lådbroar. Varje tvärsnitt har först optimerats att precis klara de dynamiska kraven avseende 2D-dynamik, utan beaktande av den statiska dimensioneringen. I många fall skulle tvärsnitten troligen behöva ökas för att klara den statiska bärförmågan.

    Plattbroar med spännvidder från 10 – 25 m och 1 – 4 fack har analyserats. I flertalet fall, främst vid kortare spännvidder, är egenfrekvensen för böjning lägre i 3D-modellen jämfört med 2D-modellen. Detta beror på mindre medverkande tvärsnitt i böjning i 3D (shear-lag). Detta resulterar i en lägre resonanshastighet och därmed ofta en större dynamisk respons för samma hastighetsintervall. I övrigt överensstämmer det dynamiska verkningssättet väl mellan 2D och 3D. Inverkan av vridning synes inte vara styrande för de studerade fallen.

    På motsvarande sätt har balkbroar med spännvidder från 20 – 40 m och 1 – 4 fack analyserats. På samma sätt som för plattbroar ger balkbroar lägre böjfrekvens i 3D jämfört med 2D. För dubbelspårsbroar är skillnaden i respons mellan 2D och 3D liknande som för plattbroar. För enkelspåriga balkbroar visar 3D-modellen i några fall en avsevärt lägre respons utan utpräglade resonanstoppar inom samma hastighets­intervall som 2D-modellen. Orsaken tros vara en kombination av upplagens excentricitet och brons massa, vilket vid vertikal böjning bidrar till en horisontell masströghet. Detta visas i de flesta fall kunna beskrivas med en modifierad 2D-modell.

    Lådbroar med spännvidd 40 – 70 m i 1 – 3 fack har analyserats. P.g.a. hög vridstyvhet är egenfrekvensen för vridning mycket högre än första böjmoden och p.g.a. mindre shear-lag är egenfrekvensen för böjning likvärdig i 2D och 3D. Detta ger små skillnader i dynamisk respons mellan 2D och 3D-modellerna.

    I de fall dynamiska kontroller utförs med förenklade metoder enligt (Svedholm & Andersson, 2016) föreslås att följande beaktas:

    • Första böjfrekvensen n0 bör beakta inverkan av shear-lag och upplagens excentricitet baserat på en 3D-modell, vilket används som indata i design­diagrammen.

    • Då första vridmoden nT < 1.2n0 bör en fullständig dynamisk kontroll utföras i 3D.

    • I de fall en 3D-modell visar flera närliggande egenmoder för böjning med samma form bör en fullständig dynamisk kontroll utföras i 3D.

  • 29.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Attenuating resonant behavior of a tied arch railway bridge using increased hanger damping2012Inngår i: Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management, Taylor & Francis Group, 2012, s. 2572-2577Konferansepaper (Fagfellevurdert)
    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.

  • 30.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Dynamics of railway bridges, analysis and verification by field tests2015Inngår i: EVACES'15, 6th International Conference On Experimental Vibration Analysis For Civil Engineering Structures / [ed] Glauco Feltrin, EDP Sciences, 2015, Vol. 24Konferansepaper (Fagfellevurdert)
    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.

  • 31.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    O'Connor, Alan
    Trinity College Dublin.
    Development of a multi-passive tuned mass damper, theory and experiments2014Inngår i: Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014, Porto, 2014, s. 1551-1556Konferansepaper (Fagfellevurdert)
    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.

  • 32.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    O'Connor, Alan
    External damping of stay cables using adaptive and semi-active vibration control2013Inngår i: Proceedings of the 8th International Cable Supported Bridge Operators Conference, Edinburgh, Scotland, 2013Konferansepaper (Fagfellevurdert)
    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.

  • 33.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    O'Connor, Alan
    Semi-active damping systems for railway bridges2012Inngår i: / [ed] Colin Caprani, Alan O'Connor, Dublin, 2012, s. 177-182Konferansepaper (Fagfellevurdert)
    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.

  • 34.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    O'Connor, Alan
    Vibration mitigation of railway bridges using adaptive damping control2013Inngår i: Assessment, Upgrading and Refurbishment of Infrastructures, 2013Konferansepaper (Fagfellevurdert)
    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.

  • 35.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Leander, John
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Extending the fatigue service life of a railway bridge by local approaches2013Konferansepaper (Fagfellevurdert)
    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.

  • 36.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Lind Östlund, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Mahir, Ülker-Kaustell
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Full-Scale Dynamic Testing of a Railway Bridge Using a Hydraulic Exciter2018Inngår i: 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, s. 354-363Konferansepaper (Fagfellevurdert)
    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.

  • 37.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Development and testing of a bi-directional multi-passive tuned mass damperInngår i: Computer-Aided Civil and Infrastructure Engineering, ISSN 1093-9687, E-ISSN 1467-8667Artikkel i tidsskrift (Annet vitenskapelig)
    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.

  • 38.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Development of a Bi-directional Multi-Passive Tuned Mass DamperInngår i: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541XArtikkel i tidsskrift (Fagfellevurdert)
    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.

  • 39.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. Swedish Transport Adm Trafikverket, Solna, Sweden.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Passive and Adaptive Damping Systems for Vibration Mitigation and Increased Fatigue Service Life of a Tied Arch Railway Bridge2015Inngår i: Journal of Bridge Engineering, ISSN 1084-0702, E-ISSN 1943-5592, Vol. 30, nr 9, s. 748-757Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 40.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Roslin, Mattias
    Trafikverket.
    Load capacity of inner lining system s due to impact from falling rocks2015Inngår i: SEE Tunnel: Promoting Tunneling in SEE Region / [ed] Davorin Kolic, Dubrovnik, 2015Konferansepaper (Annet vitenskapelig)
    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.

  • 41.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Roslin, Mattias
    Trafikverket.
    Taube, Arvid
    Trafikverket.
    Bärförmåga hos inklädnadssystem vid stödbelastning från fallande bergblock2015Inngår i: Bergmekanikdag 2015 / [ed] BeFo, Stockholm: Stiftelsen Bergteknisk forskning , 2015Konferansepaper (Annet vitenskapelig)
    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.

  • 42.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Sundquist, Håkan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Full Scale Tests and Structural Evaluation of Soil-Steel Flexible Culverts for High-Speed Railways2012Inngår i: Second European conference on Buried Flexible Steel structures Rydzyna April 23rd – 24th 2012, 2012Konferansepaper (Fagfellevurdert)
    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.

  • 43.
    Andersson, Andreas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. The Swedish Transport Administration (Trafikverket), Sweden.
    Ülker-Kaustell, Mahir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. Tyréns AB, Sweden.
    Borg, Richard
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Dymén, Olivier
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Carolin, Anders
    Trafikverket.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Pilot testing of a hydraulic bridge exciter2015Inngår i: EVACES'15, 6th International Conference on Experimental Vibration Analysis For Civil Engineering Structures / [ed] Glauco Feltrin, Zurich: EDP Sciences, 2015, Vol. 24, s. 02001-Konferansepaper (Fagfellevurdert)
    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.

  • 44.
    Andersson, Jenny
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Widening of The Nockeby Bridge: Methods for strengthening the torsional resistance2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 45.
    Andersson, Linda
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Klingsmo, Maria
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Mellanstödslös bro över motorväg- i högpresterande betong med extern förspänning2004Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 46.
    Andersson, Lisa
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Dynamics of staircases: A case study to improve finite element modeling2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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. 

  • 47.
    Andersson, Mattias
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Hagersten, Elsa
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Optimal viscous dampers targeting multiple cable modes with FEM2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 48.
    ANDRÉN JAKOBSSON, NICOLINA
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    BOHMAN, SIMON
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    A Generative Design of TimberStructures According to Eurocode: Development of a Parametric Model in Grasshopper2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The interest of timber structures has in recent years increased, primarily due tothe environmental benets of timber. This has created an increased demand forstructural engineers with timber expertise. At the same time the concept of structuralparametric design have become more popular. This new way of working withdesigns enables for architects and engineers to explore dierent geometries in earlystages of a project. However, the combination of a parametric workow and timberdesign have so far been limited due to the complexity of the material.This thesis aims to create an parametric workow within the visual programmingenvironment Grasshopper. This enables analysis of structural design simultaneouslywith a cross sectional and topological optimization of timber structures. The structuralanalysis is performed with Karamba which is a plug-in tool to the Grasshopperenvironment. The design verication based on Eurocode EN-1995 have been manuallyscripted in python components. The parametric model have been applied to acase where the main bearing bearing of a glass roof is to be designed. Three dierentgeometries have been evaluated with regard to cross sectional dimensions andgeometrical shape.The framework with a truss turned out to be a preferable design if only consideringweight, deection and utilization. The truss frame provides the lowest weight and thesecond smallest displacement. Furthermore, a comparison of the structural analysisand design have been performed with the FEM-program Robot. The compassionshow similar results, increasing the reliability of the Grasshopper model and theresults from this tool. It conrms it is possible to perform generative design oftimber structures within the same interface.The Grasshopper model is limited and can not handle all variations of 2D timberstructures. The complexity and variation of such calculations in conjunction with theEurocode have not been implemented during the time-span of this thesis. However,it is general within the limitations of the case study meaning a variety of framegeometries can be evaluated.

  • 49.
    Ansell, Anders
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Holmgren, Jonas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Mundt, Elisabeth
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Installationsteknik (bytt namn till Installations- och energisystem 2012-03-01).
    Silfwerbrand, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Stille, Håkan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Sundquist, Håkan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    State-of-the-art och förslag till forskningsprojekt: Drift, underhåll och reparation av trafiktunnlar2007Rapport (Annet vitenskapelig)
  • 50.
    Ansell, Anders
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Holmgren, Jonas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Norlin, Bert
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Grunder för konstruktion med betong, stål och trä2006Rapport (Annet vitenskapelig)
1234567 1 - 50 of 617
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