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  • 1.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Structural dynamic and stress wave models for analysis of shotcrete on rock exposed to blasting2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 35, no 1, p. 11-17Article in journal (Refereed)
    Abstract [en]

    During blasting in tunnels and mines, the interaction between shotcrete (sprayed concrete) and rock is influenced by propagating stress waves. Shotcrete support in hard rock tunnels is studied here through numerical analysis using three different modelling approaches. The stress response in the shotcrete closest to the rock when exposed to P-waves striking perpendicularly to the shotcrete–rock interface is simulated. The first model tested is a structural dynamic model that consists of masses and spring elements. The second is a model built up with finite element beam elements interconnected with springs. The third is a one-dimensional elastic stress wave model. The models give comparable results, although the definition of the dynamic loads is different. The analysis results can be used to estimate whether the shotcrete will fail or not for a prescribed distance to detonating explosives inside the rock.

  • 2. 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.

  • 3.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    The dynamic element method for analysis of frame and cable type structures2005In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 27, no 13, p. 1906-1915Article in journal (Refereed)
    Abstract [en]

    With the dynamic element method (DEM), results more accurate than with the conventional finite element method (FEM) are obtained with the same number of degrees of freedom. This is due to the introduction of shape functions of polynomial type, introducing frequency dependence into the mass matrix expressions. It is demonstrated how this affects free vibration analysis, including the solution of nonlinear eigenvalue problems. Various numerical techniques for solving these polynomial problems are discussed. The polynomial matrix formulations for stiffness and mass matrices are given for a beam, a bar and a cable element. Numerical examples demonstrate how the DEM can be implemented for modelling of frame type structures and its efficiency is compared to that of the conventional FEM

  • 4.
    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.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Sweden.
    Statistical screening of modelling alternatives in train-bridge interaction systems2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 59, p. 693-701Article in journal (Refereed)
    Abstract [en]

    The effect of parameter variations in railway bridges subjected to train loads has been evaluated within the framework of a two-level factorial experiment. Especially, the influence of train-bridge interaction in comparison to other parameter variations is highlighted. Variations in the system parameters were introduced, corresponding to modelling alternatives considering reasonable uncertainties in a bridge design model. The dynamic effect from a passenger train set has been evaluated at, and away from, resonance in beam bridges of span lengths 6, 12, 24 and 36. m. By means of the two-level factorial design, effects from changes in a single parameter, as well as joint effects from simultaneous changes in several parameters, may be evaluated. The effect of including train-bridge interaction through a simple vehicle model as opposed to moving forces was found most distinct at resonance. The effect of the choice of load model was furthermore shown largest for the bridges of span length 24 and 36. m, where it was found more influential or comparable to the effect of other system parameter uncertainties. The high influence of the load model may well be attributed to the fact that the natural frequencies of the 24 and 36. m bridges are close to the vertical frequency of the primary suspension system of the train. The reduction of response obtained with the train-bridge interaction model are discussed in relation to bridge frequency rather than span length, and compared to the Additional Damping Method given in the European design code.

  • 5.
    Battini, Jean-Marc
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    A simple finite element to consider the non-linear influence of the ballast on vibrations of railway bridges2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 9, p. 2597-2602Article in journal (Refereed)
    Abstract [en]

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

  • 6.
    Bayoglu Flener, Esra
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Dynamic testing of a soil-steel composite railway bridge2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 12, p. 2803-2811Article in journal (Refereed)
    Abstract [en]

    Actual dynamic response of a long-span corrugated steel culvert railway bridge is studied. The bridge, which is a type of soil-steel composite structures, has a span of 11 m. Tests were carried out by measuring strains and displacements during passages of a locomotive at different speeds. Vertical ballast accelerations as well as the effects of braking forces were also measured. The tests showed that the speed has a large influence on the displacements, thrusts and moments. The measured dynamic displacements and thrusts are as much as 20% larger than the corresponding static response. This is greater than the values specified in bridge design codes. Dynamic amplification factors as high as 1.45 were obtained for the moments at the quarter point which is found to be much larger than the values for the crown point. This type of bridge structure is believed to be less sensitive to resonance from passing trains than other common bridge types, due to the high damping values obtained from the forced vibration tests.

  • 7.
    Cantero, Daniel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Roughan and O'Donovan Innovative Solutions, Ireland.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Numerical evaluation of the mid-span assumption in the calculation of total load effects in railway bridges2016In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 107, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Maximum load effects in simply supported railway bridges traversed by trains are generally investigated at the mid-span section. However, this assumption is not necessarily correct. The true maximum load effect might occur at some other bridge section and its magnitude could be significantly greater. This paper quantifies the underestimation of the load effects as a result of exclusively considering the middle section, with special emphasis on resonant situations. A 2D numerical model of a vehicle-track-bridge system was used to evaluate different vehicle velocities, bridge properties and track irregularity conditions. The error due to the mid-span assumption depends on the particular case considered but can be related to the relative energy content of the higher modes of vibration. The results show that the error is greatest for accelerations, smaller for bending moments and is almost negligible for displacements.

  • 8.
    Cantero, Daniel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Gonzalez, Arturo
    The Virtual Axle concept for detection of localised damage using Bridge Weigh-in-Motion data2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 89, p. 26-36Article in journal (Refereed)
    Abstract [en]

    This paper proposes a new level I damage identification method for short span statically indeterminate bridges using the information provided by a Bridge Weigh-in-Motion system. Bridge Weigh-in-Motion systems measure the bridge deformation due to the crossing of traffic to estimate traffic attributes, namely axle weights and distances between axles for each vehicle. It is theoretically shown that it is convenient to introduce a fictitious weightless axle, which has been termed 'Virtual Axle', in the Bridge Weigh-in-Motion calculations to derive a damage indicator. The latter can be used both as a new robust output-only model-free level I Structural Health Monitoring technique and as a new self-calibration method for Bridge Weigh-in-Motion systems. The response of a fixed-fixed beam traversed by a 2-axle vehicle travelling over an irregular profile is used to validate the proposed method. By means of Monte Carlo simulation the influence of the key parameters such as the degree and location of damage, noise levels, span lengths and profile irregularities on the accuracy of the method are investigated. The results show that the 'Virtual Axle' method is able to detect small local damages in statically indeterminate structures.

  • 9.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Henriksson, Marielle
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mendicino, Antonio Lorenzo
    Fortino, Stefania
    Toratti, Tomi
    NMR imaging study and multi-Fickian numerical simulation of moisture transfer in Norway spruce samples2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 11, p. 3079-3086Article in journal (Refereed)
    Abstract [en]

    Wood has potential as a renewable material for a large variety of applications that often call for improved properties such as dimensional stability, moisture insensitivity, and durability. Moisture migration in wood is a particularly important factor in determining the cost-effective service life of wooden construction. Within the present research, proton NMR imaging was applied for recording the moisture spatial distribution of various samples of Norway Spruce. Moisture distribution along the radial, tangential and longitudinal directions in wood was monitored at different times upon three consecutive changes of relative humidity: (1) from 65% to 94%; (2) from 94% to 33%; (3) from 33% to 65%. Uncoated samples and specimens treated with different types of surface coatings were studied. The experiments were numerically simulated by using the multi-Fickian model. The model describes the moisture transport process in wood which is characterized by three phenomena: (a) bound water diffusion, (b) water vapor diffusion and (c) coupling between the two phases through sorption. The model is implemented into the Abaqus FEM code. The numerical results are found to be in agreement with the experimental data.

  • 10.
    Gonzalez, Ignacio
    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.
    Analysis of the annual variations in the dynamic behavior of a ballasted railway bridge using Hilbert transform2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 60, p. 126-132Article in journal (Refereed)
    Abstract [en]

    In this paper the variations in dynamic properties (eigenfrequency and damping) due to seasonal effects of a single span, ballasted railway bridge are studied. It is demonstrated that both the eigenfrequency and characteristic damping vary importantly with environmental conditions and amplitude of vibration. For this, acceleration signals corresponding to roughly a year of monitoring are analyzed with the Hilbert transform and the instantaneous frequency and equivalent viscous damping ratio are calculated during the free vibrations. Over 1000 trains passages were analyzed, with temperatures ranging from -30 to +30°C and amplitudes of vibration varying from 0.5m/s2 to 0. The location of the accelerometers allowed for separation of the signals into their bending and torsional components. It was found that during the cold season, with months of temperatures below 0°C, the dynamic properties varied the most. Not only did the frequencies (for small vibrations) differ more than 9% even for a given temperature, but the non-linearity present in the structure did also change in a matter of hours. These findings are important in the context of Structural Health Monitoring. Any system that aims at warning early in the onset of damage by analyzing changes in the dynamic characteristic of a structure needs to first fully understand and account for the natural variability of these parameters, often much larger than what could be expected from reasonable levels of damage.

  • 11.
    Gonzalez, Ignacio
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Seasonal effects on the stiffness properties of a ballasted railway bridge2013In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 57, p. 63-72Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Hansson, Håkan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Experiments on penetration of ogive nosed penetrators in normal strength and high performance concreteIn: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Other academic)
  • 13.
    Heng, Piseth
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Hjiaj, Mohammed
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Limam, Ali
    An enhanced SDOF model to predit the behaviour of a steel column impacted by a rigid body2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 152, p. 771-789Article in journal (Refereed)
    Abstract [en]

    The transient dynamic response of a steel beam-column subjected to impact loading is a complex phenomenon involving large localized plastic deformations and non-smooth contact interactions. Exposed to high intensity of the contact force generated from impact, the beam-column may undergo large displacement and inelastic deformation. Previous research has shown that a calibrated elasto-plastic single degree of freedom system is able to reproduce both the displacement and the force time-history of a steel beam subjected to non-impulsive loading or low-velocity impact. In these models, the static force-displacement curve is derived from either experiments or detailed 3D nonlinear analysis. Tri-linear resistance function has been extensively used to reproduce the different stages of the response including catenary effects. A rigorous treatment of such a complex problem calls for the use of non-smooth analysis tools to handle the impulsive nature of the impact force, the unilateral constraint, the impenetrability condition and the discontinuity of the velocity in a rigorous manner. In this paper, we present a non-smooth elasto-plastic single degree of freedom model under impact loading that permits the use of arbitrary resistance function. Adopting the non-smooth framework offers tools such as differential measures and convex analysis concepts to deal with unilateral contact incorporating Newton’s impact law. The mid-point scheme is adopted to avoid numerical unrealistic energy decay or blowup. Furthermore, the non-penetration condition is numerically satisfied by imposing the constraint at only the velocity level to guarantee energy-momentum conservation [1]. The explicit expression of resistance functions of the beam that are used in the SDOF model are obtained from a simplified nonlinear static analysis of two beam-column models. In the analysis, a linear relation between normal force and bending moment is assumed for the plastification of the hinges. Two proposals to simplify the explicit expressions of the model’s response behavior are given. Performing an energy-based analysis, we predict maximum displacement that is needed to absorb the kinetic energy arising from the impact for different coefficient of restitution. The numerical examples underline the validity of the model by showing good agreement with the predictions of reference models.

  • 14.
    Inagaki, Kenta
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Ekh, Johan
    Fredriksson, Johan
    Zahrai, Said
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Mechanical response of electrical cables to imposed motionIn: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Other academic)
  • 15.
    Johansson, Christoffer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ni Nuallain, Nora Aine
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Pacoste, Costin
    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.
    A methodology for the preliminary assessment of existing railway bridges for high-speed traffic2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 58, p. 25-35Article in journal (Refereed)
    Abstract [en]

    The Swedish government is considering upgrading the train speed along three railway lines in the Southern part of Sweden from 200 km/h to 250 km/h. According to the current design code, this requires that the bridges be examined with dynamic simulations to avoid excessive vibrations. This paper employs a method that can be used at an early stage to estimate the expected cost of upgrading a bridge network. The results revealed that 70% of the plate/beam bridges, 64% of the closed slab-frame bridges, and 41% of the open slab-frame bridges are expected to not fulfill the requirement on the maximum bridge deck acceleration for ballasted tracks.

  • 16.
    Johansson, Christoffer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Ni Nuallain, Nora Aine
    Pacoste, Costin
    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.
    Probabilistic Dynamic Analysis of Existing Railway Bridges for High-Speed TrafficIn: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Other academic)
    Abstract [en]

    The Swedish government is considering upgrading the train speed along three railway lines in the Southern part of Sweden from 200 km/h to 250 km/h. According to the current design code, this requires that the bridges be examined with dynamic simulations to avoid excessive vibrations. This paper employs a method that can be used at an early stage to estimate the expected cost of upgrading a bridge network. The results revealed that 70% of the plate/beam bridges, 64% of the closed slab-frame bridges, and 41% of the open slab-frame bridges are expected to not fulfil the requirement on the maximum bridge deck acceleration for ballasted tracks.

  • 17.
    Karoumi, Raid
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Wiberg, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Liljencrantz, Axel
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Monitoring traffic loads and dynamic effects using an instrumented railway bridge2005In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 27, no 12, p. 1813-1819Article in journal (Refereed)
    Abstract [en]

    This paper presents a cost-effective method for the assessment of actual traffic loads on an instrumented bridge. The instrumentation of a newly constructed integral-type railway bridge in Stockholm (Sweden) is described. A complete “Bridge Weigh-in-Motion” (B-WIM) system, with axle detection and accurate axle-load evaluation, was implemented using only four concrete embedded strain transducers. A temporary accelerometer was attached to the edge beam of the bridge to evaluate the eigenfrequencies, predict possible wheel/rail defects, and check whether the acceleration limit value for ballast instability (as given in railway bridge design codes) is exceeded. The main objective of the monitoring project has been to increase the knowledge of actual traffic loads and their effect on railway bridges, through both measurements and numerical simulations. Some very early but representative results are presented, and the efficiency of the algorithms and usefulness of the monitoring program highlighted.

  • 18.
    Leander, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Monitoring and enhanced fatigue evaluation of a steel railway bridge2010In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 32, no 3, p. 854-863Article in journal (Refereed)
    Abstract [en]

    During routine inspections of the Soderstrom Bridge in central Stockholm, one of Sweden's most important railway bridges, cracks were found in the web of the main steel beams. The finding initiated theoretical Studies which showed that the cracks developed mainly due to poorly designed connections of the cross beams and out-of-plane bending of the web. The Studies also showed an alarming result regarding the remaining fatigue life of the stringers and the cross beams. However, no cracks or other damage have been found on these components during the inspections. To explore the differences between the theoretical indications and the inspected reality, an extensive monitoring program has been performed. This article describes the monitoring program and the analysis methods used. Some results regarding the remaining fatigue life based on measured and theoretical values are presented. (C) 2009 Elsevier Ltd. All rights reserved.

  • 19. Leitner, M.
    et al.
    Khurshid, Mansoor
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Stability of high frequency mechanical impact (HFMI) post-treatment induced residual stress states under cyclic loading of welded steel joints2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 143, p. 589-602Article in journal (Refereed)
    Abstract [en]

    This paper investigates the effect of cyclic loading on the stability of compressive residual stress fields induced by high frequency mechanical impact (HFMI) post-weld treatment. First, the effectiveness of the post-treatment technique is shown by fatigue tests incorporating mild steel S355 and high strength steel S960 longitudinal stiffener specimens. Extensive X-ray residual stress measurements support the beneficial impact on the compressive residual stress state for mild and high-strength steel structures. They also illustrate that cyclic loading leads to a significant local relaxation of this condition. Second, a numerical simulation chain incorporating a structural weld simulation, numerical analysis of the HFMI-treatment, and a final cyclic loading step for the investigated mild steel specimen is set-up. The results show that the residual stresses at the surface of the weld toe are in agreement to the X-ray measurements for both the as-welded and HFMI-treated condition, which basically proofs the applicability of the manufacturing simulation. The numerical computation including the first five load-cycles demonstrates that the simulated residual stress relaxation again exhibits consistent results with the measurements. An additional utilization of an analytical relaxation model from literature reveals that the estimation of the residual stress state in the high-cycle fatigue region is well employable. Therefore, the scientific results in this paper proof the applicability of the presented consecutive numerical-analytical procedure to assess the local compressive residual stress stability of HFMI-treated welded steel joints in both the low- and high-cycle fatigue region.

  • 20.
    Liu, Zhendong
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Rønnquist, A.
    Application of tuned-mass system on railway catenary to improve dynamic performance2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 165, p. 349-358Article in journal (Refereed)
    Abstract [en]

    Finding a simple and practical method to improve the dynamic behaviour of a specific structure is always desirable in civil and mechanical engineering. The railway catenary system is the overhead power line above the track, interacting together with the train-based pantograph to transfer electric power. Due to vertical stiffness variation and a propagating wave along the catenary, the fluctuation of the contact force becomes significant with operational speed increasing. Therefore, this has become one of the key factors which limits the operational speed and service life of key components. Wire misalignment, structural errors and uneven mass distribution of the catenary can further deteriorate the contact stability. In order to achieve a higher speed on existing lines, the catenary needs large-scale modification implying long out-off-service time. From the designing aspect, all components directly fixed to the catenary, like clamps, steady arms and other fittings, are made as light and small as possible to minimize disturbances. However, in other engineering applications, some well-designed additional mass systems are adopted aiming to improve their dynamic performance. In order to take advantage of these unavoidable masses on the catenary, an investigation on lumped-mass distribution in single-pantograph and multi-pantograph operations is performed with help of a 3D pantograph-catenary finite element (FE) model. The results show that a rightly-tuned mass, here the implementing location and the elasticity of its connection, can positively change the dynamic performance without implementing large-scale modification to the existing system. Through a brief discussion on the mechanism of this positive effect, this paper proposes that applying some artificial tuned-mass system can be a possible method to overcome unfavourable working conditions or even allow speed increase on existing lines.

  • 21.
    Magnusson, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hallgren, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Tyréns.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Numerical analyses of shear in concrete structures subjected to distributed blast loads2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Refereed)
  • 22.
    Mahdavi Shahri, Meysam
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Höglund, Torsten
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Eurocode 9 to estimate the fatigue life of friction stir welded aluminium panels2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 45, p. 307-313Article in journal (Refereed)
    Abstract [en]

    Eurocode 9 is a standard that covers the design of building and engineering structures made from wrought and cast aluminium alloys. A part of the Eurocode 9 handles the design of aluminium structures susceptible to fatigue. Eurocode 9 has data for aluminium alloys and welded structures for conventional welding methods (fusion welding) except for friction stir welding processes. The present study compares fatigue test results from friction stir welded joints with fatigue curves of traditional fusion welded joints which are presented in Eurocode 9. The results are in reasonable agreement with experimental data and FEM predictions. This suggests that Eurocode 9 can be used for estimating the fatigue strength of friction stir welded joints.

  • 23.
    Malm, Richard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Field testing and simulation of dynamic properties of a tied arch railway bridge2006In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 28, no 1, p. 143-152Article in journal (Refereed)
    Abstract [en]

    This paper deals with the dynamic effects on a tied arch railway bridge during train passages. The bridge is located in Ange municipality in central Sweden. Large vibrations of the hangers were observed during train passages and field measurements have been performed to study the train induced vibrations of the hangers. According to the Palmgren-Miners linear damage rule, there is a great risk of fatigue in the threaded parts of the hangers. The low damping in the hangers has a large influence of the risk of fatigue failure. A 3D finite element model of the bridge has been developed where the dynamic vehicle-bridge interaction was modelled using contact surface formulation with a sprung mass train system. The measured data results are compared with the results from the FE model to give a better understanding of the dynamic behaviour of the bridge.

  • 24.
    Malm, Richard
    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.
    Time-dependent analyses of segmentally constructed balanced cantilever bridges.2010In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 32, no 4, p. 1038-1045Article in journal (Refereed)
    Abstract [en]

    Segmentally constructed concrete cantilever bridges often exhibit larger deflections than those predicted by the design calculations The slender and long spans in combination with the fact that permanent loads are only partially compensated for by prestressing are reasons for the large deflections that increase during the life time of the bridge, although at a decreasing rate The rate of drying shrinkage may be one reason for the accelerating displacement of cast-in-place bridges The construction of continuous spans instead of introducing joints has both comfort and durability advantages The continuous span is however more complicated to design, and secondary restraint moments due to creep, shrinkage and thermal effects develop at the connection The results of analyses of the stepwise cast-in-place construction of a balanced cantilever bridge with time-dependent material properties show both higher deflect ion than those originally assumed in the design calculations and high stresses in the webs due to stressing of the tendons in the bottom flange The analyses show significant effects of creep during cantilevering and of a non-uniform drying shrinkage rate on the continuous bridge

  • 25.
    Mellat, Peyman
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Pettersson, Lars
    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.
    Dynamic behaviour of a short span soil-steel composite bridge for high-speed railways - field measurements and FE-analysis2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 69, p. 49-61Article in journal (Refereed)
    Abstract [en]

    The dynamic response from passing trains at high speed is studied for a short span soil-steel composite bridge. Field measurements have been performed, comprising steel strains, vertical crown displacements and accelerations in the steel and the backfill. Soil material damping properties are estimated through analysis of the field measurements. Approaches for numerical modelling are presented, focusing on the dynamic response from passing trains. Both 2D and 3D continuum models are compared with the measured response. Based on the models, the influence of the Young’s modulus of the backfill on the bridge behaviour is investigated. The 3D-model also enables estimation of the load distribution, which is found to increase at higher train speeds. An effective width to be used in 2D analyses is proposed. A dynamic design check using the high-speed train load models in the Eurocode is presented, that for the studied bridge envisage a resonance peak at about 320 km/h.

  • 26. Navik, Petter
    et al.
    Ronnquist, Anders
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Identification of system damping in railway catenary wire systems from full-scale measurements2016In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 113, p. 71-78Article in journal (Refereed)
    Abstract [en]

    Damping is an important property in predicting the response of any civil or mechanical engineering structure, including railway catenary systems. Numerical models describing the pantograph-catenary interaction are dependent on a proper description of the structural damping for both systems to obtain accurate results. A proper description of the damping in different pantographs can easily be found in the literature. However, few studies have considered the damping properties in railway catenary systems even though such systems are considered to be lightly damped. The aim of this study was to identify the system damping of catenary sections by thoroughly analyse several recorded acceleration time series. These time series were sampled in several points on three different existing railway catenary systems, rendering a good description of the system damping in the frequency range of 0-20 Hz. The covariance-driven stochastic subspace identification (Cov-SSI) method was used to analyse the time series, and Rayleigh coefficients were successfully identified for all three catenary sections. (C) 2016 Elsevier Ltd. All rights reserved.

  • 27.
    Ni Nuallain, Nora Aine
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Johansson, Christoffer
    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.
    Pacoste-Calmanovici, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Applicability of probabilistic methods for assessing a network of bridges for future high-speed trafficIn: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Refereed)
  • 28.
    Ni Nuallain, Nora Aine
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Department of Civil, Structural & Environmental Engineering, Trinity College Dublin, Ireland.
    Risk based optimisation of seismic retrofit strategies for integral concrete bridgesIn: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Other academic)
  • 29.
    Sangiorgio, Filippo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Mancini, Giuseppe
    Politecnico di Torino.
    Probabilistic Investigation on the Ultimate Load Behaviour of RC Structures Designed According to EN 1992-1-1 and Subjected to Multiple Failure Modes2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Other academic)
  • 30. Shams-Hakimi, Poja
    et al.
    Zamiri, Farshid
    Al-Emrani, Mohammad
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Experimental study of transverse attachment joints with 40 and 60 mm thick main plates, improved by high-frequency mechanical impact treatment (HFMI)2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 155, p. 251-266Article in journal (Refereed)
    Abstract [en]

    In recent years, high-frequency mechanical impact (HFMI) treatment has grown in popularity due to its efficiency in improving the fatigue strength of welded joints. The fatigue performance of HFMI-treated welded steel joints has, however, not been thoroughly studied for plate thicknesses above 30 mm. In this study, 40 and 60 mm thick main plates with non-load-carrying transverse attachments have been fatigue tested under constant amplitude four-point bending, both in as-welded and HFMI-treated condition to investigate the fatigue performance for large plate thicknesses, typical for weldments in bridges. Axial fatigue strengths were estimated by a modification of the experimental results with fracture mechanics calculations. The main conclusions are that HFMI treatment can result in significant fatigue strength improvement even for large main plate thicknesses and that the difference in fatigue strength between bending and axial loading is negligible for the specimen geometries used in this study.

  • 31. Shu, Jiangpeng
    et al.
    Zhang, Ziye
    Gonzalez, Ignacio
    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.
    The application of a damage detection method using Artificial Neural Network and train-induced vibrations on a simplified railway bridge model2013In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 52, p. 408-421Article in journal (Refereed)
    Abstract [en]

    A damage detection algorithm based on Artificial Neural Network (ANN) was implemented in this study using the statistical properties of structural dynamic responses as input for the ANN. Sensitivity analysis is performed to study the feasibility of using the changes of variances and covariances of the dynamic responses of the structure as input to the ANN. A finite element (FE) model of a one-span simply supported beam railway bridge was developed in ABAQUS (R), considering both single damage case and multi-damage case. A Back-Propagation Neural Network (BPNN) was built and trained to perform damage detection. A series of numerical tests on the FE model with different vehicle properties was conducted to prove the validity and efficiency of the proposed approach. The results reveal not only that the ANN, together with the statistics, can correctly estimate the location and severity of damage;but also that the identification of the damage location is more difficult than that of the damage severity. In summary, it is concluded that the use of statistical property of the structural dynamic responses as damage index along with the Artificial Neural Network as tool for damage detection for an idealized model of a bridge is reliable and effective.

  • 32.
    Svedholm, Christoffer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Sweden.
    Zangeneh, Abbas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Sweden.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Sweden.
    François, S.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Vibration of damped uniform beams with general end conditions under moving loads2016In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 126, p. 40-52Article in journal (Refereed)
    Abstract [en]

    In this paper, an analytical solution for evaluating the dynamic behaviour of a non-proportionally damped Bernoulli–Euler beam under a moving load is derived. The novelty of this paper, when compared with other publications along this line of work is that general boundary conditions are assumed throughout the derivation. Proper orthogonality conditions are then derived and a closed form solution for the dynamical response for a given eigenmode is developed. Based on this, the dynamical response of the system to any load can be determined by mode superposition. The proposed method is particularly useful for studying various types of damping mechanisms in bridges, such as soil–structure interaction, external dampers, and material damping. Several numerical examples are presented to validate the proposed method and provide insight into the problem of non-proportionally damped systems. The numerical examples also allow for some interesting observations concerning the behaviour of modal damping for closely spaced modes (with respect to undamped natural frequencies).

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

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

  • 34.
    Wadi, Amer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ViaCon AB, Sweden .
    Pettersson, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Skanska Sweden AB - Major Projects, Sweden .
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Flexible culverts in sloping terrain: Numerical simulation of soil loading effects2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 101, p. 111-124Article in journal (Refereed)
    Abstract [en]

    This paper investigates the performance of flexible culverts – often referred to as soil–steel composite bridges (SSCB) – when constructed in sloping topography. A number of 2D finite element models were created to simulate three case studies compromising two pipe arches and one high profile arch. The models were generated to investigate the effect of different surface slopes for different depths of soil cover. The aim was to understand and perceive the change of sectional forces in the structure with respect to slope increase under different soil covers. In addition, the effect of structure presence in the soil was also investigated in terms of soil stability. The results enable to realize the susceptibility of such structures to low heights of soil cover when built in sloping environment, which is seen in the incremental change in displacements and sectional forces, specially the bending moments. It is also found that the geometrical aspects of the profile shapes have more pronounced effect on their performance when introducing steeper slopes. The safety factor of soil stability is found to decrease when introducing such structures in the soil.

  • 35.
    Wallin, Joakim
    et al.
    KTH.
    Leander, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Strengthening of a steel railway bridge and its impact on the dynamic response to passing trains2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 2, p. 635-646Article in journal (Refereed)
    Abstract [en]

    Two different strengthening methods for a through-girder steel railway bridge are investigated. The studied structure is the Soderstrom Bridge, located in the city of Stockholm, Sweden. Due to fatigue problems, it is in need of assessment and strengthening. In one of the methods, arches are added under the bridge modifying the structural system and lowering the stress ranges for all structural members. The other method consists of prestressing the floor beams. This increases their stiffness and transforms the mean stress in the lower flanges from tension to compression. A 3D finite element model is created and verified with measurements. The different strengthening methods are tested in the model by dynamic analysis with moving train loads. The strengthening methods show some positive effect concerning the fatigue life. Changes in vertical bridge deck acceleration for high speed traffic are also presented. A comparison between the European code and the Swedish code regarding vertical bridge deck acceleration levels for high speed traffic shows large differences for the bridge.

  • 36. Yildirim, Halid Can
    et al.
    Leitner, Martin
    Marquis, Gary B.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. Department of Applied Mechanics, School of Engineering, Aalto University, Aalto, Finland.
    Stoschka, Michael
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. Department of Aerospace Engineering, Khalifa University of Science, Technology and Research (KUSTAR), P.O. Box: 127788, Abu Dhabi, United Arab Emirates.
    Application studies for fatigue strength improvement of welded structures by high-frequency mechanical impact (HFMI) treatment2016In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 106, p. 422-435Article in journal (Refereed)
    Abstract [en]

    In 2013, a new guideline for the design of high-frequency mechanical impact (HFMI) treatment was drafted. The proposed design curves were made based on the fatigue data of axially-loaded welded joints which were manufactured from high-strength steels. All the S-N curves were shown to be conservative with respect to the existing fatigue data for laboratory-scale specimens of longitudinal, transverse, and butt welds. In reality, structures in civil, offshore, mechanical engineering and ship industries generally include large-scale and more complicated components rather than laboratory-scale specimens. Therefore, this paper firstly presents the validation of design proposals by considering fatigue data sets for large-scale welded structures. In total, 62 fatigue data points for bridge, crane and beam-like components are reported, in which the yield strength varies from 250 to 725 MPa, and stress ratio varies from -1 to 0.56. Validations are then extended also for cover plates by performing fatigue tests of 23 weld details both in as-welded and HFMI-treated cases for the use of crane industry. Both the extracted and obtained fatigue data are found to be in good agreement with the previously-proposed design guidelines for nominal and effective notch stress assessment.

  • 37.
    Zangeneh, Abbas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Stockholm, Sweden.
    Svedholm, Christoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Stockholm, Sweden.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Swedish Transport Adm, Solna, Sweden.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Stockholm, Sweden.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Identification of soil-structure interaction effect in a portal frame railway bridge through full-scale dynamic testing2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 159, p. 299-309Article in journal (Refereed)
    Abstract [en]

    This paper is devoted to identify the effect of soil-structure interaction on the dynamic response of,a portal frame railway bridge. The study aims to validate the accuracy of numerical models in evaluating the dynamic stiffness and modal properties of the bridge-soil system. To achieve this aim, a controlled vibration test has been performed on a full-scale portal frame bridge to determine the modal properties of the system through measuring Frequency Response Functions. The results of the dynamic test provide reference data for FE model calibration as well as valuable information about the dynamic behavior of this type of bridges. Using the experimental data, an FRF-based model updating procedure was used to calibrate a full 3D solid model involving the entire bridge track-soil system. Both measured and computed responses identify the substantial contribution of the surrounding soil on the global damping of the system and highlight the importance of the soil-structure interaction on the dynamic response of this type of bridges. The identified modal damping ratio corresponding to the fundamental bending mode of the studied bridge was nearly 5 times higher than the recommended design values. A simplified model for the surrounding soil was also proposed in order to attain a less complicated model appropriate for practical design purposes.

  • 38.
    Ülker-Kaustell, Mahir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Influence of non-linear stiffness and damping on the train-bridge resonance of a simply supported railway bridge2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 41, p. 350-355Article in journal (Refereed)
    Abstract [en]

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

  • 39.
    Ülker-Kaustell, Mahir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Simplified analysis of the dynamic soil-structure interaction of a portal frame railway bridge2010In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 32, no 11, p. 3692-3698Article in journal (Refereed)
    Abstract [en]

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

1 - 39 of 39
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