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  • 1.
    Afshar, R
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    van Dijk, N.P.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Bjurhager, Ingela
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Comparison of experimental testing and finite element modelling of a replica of a section of the Vasa warship to identify the behaviour of structural joints2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 147, p. 62-76Article in journal (Refereed)
    Abstract [en]

    Modelling in design of new support systems necessitates the joint stiffness of the existing wooden structures. In valuable structures, e.g. in cultural heritage, or structures with inaccessible joints, these stiffness values must be estimated, e.g. by testing joints in tailored replicas of the original parts. Although a simplified structure, the replica, can call for finite element (FE) modelling to capture the stiffness parameters. The first step in such a process is to compare FE predictions with experimental tests, for validation purposes. The reasons for unavoidable differences in load-displacement behaviour between model predictions and experimental test should be identified, and then possibly remedied by an improved model. Underlying causes like the complex shape of joints, geometrical uncertainties, contact mechanisms and material nonlinearity are generally too computationally expensive to be included in a full-scale model. It is therefore convenient to collect such effects in the contact penalty stiffness in the joint contact areas where stresses are high, which influences the resulting joint stiffness. A procedure for this is here illustrated for the case of the 17th century Vasa shipwreck A replica of a section of the ship has been constructed, and its joints were tested in bending-compression, in-plane shear and rotation. The FE simulations showed stiffer behaviour than the experimental results. Therefore, a normal penalty stiffness in contact surfaces of the joint were introduced, and used as a calibration parameter to account for the simplifying assumptions or indeliberate imprecision in the model, e.g. concerning boundary conditions, material properties and geometrical detail. The difference between numerical predictions and experimental results could then be significantly reduced, with a suitable normal penalty stiffness value. Once an acceptable finite element model has been obtained, it is shown how this can be used to identify stiffness values for joints in the physical structure with compensation for degradation of material properties due to aging and conservation treatment.

  • 2.
    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.

  • 3.
    Ahola, A.
    et al.
    Lappeenranta Lahti Univ Technol LUT, Sch Energy Syst, POB 20, FI-53851 Lappeenranta, Finland..
    Bjork, T.
    Lappeenranta Lahti Univ Technol LUT, Sch Energy Syst, POB 20, FI-53851 Lappeenranta, Finland..
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Fatigue strength capacity of load-carrying fillet welds on ultra-high-strength steel plates subjected to out-of-plane bending2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 196, article id UNSP 109282Article in journal (Refereed)
    Abstract [en]

    Weld root fatigue strength capacity is an important design criterion in load-carrying (LC) fillet welded joints subjected to cyclic loads. This paper elaborates on the weld root fatigue strength capacity of fillet welded LC joints made of ultra-high-strength steel (UHSS) and subjected to out-of-plane bending. Experimental fatigue tests are carried out using constant amplitude loading with an applied stress ratio of R = 0.1 with both pure axial, i.e. DOB = 0 (degree of bending, bending stress divided by total stress) and bending, i.e. DOB = 1.0, load conditions. The applicability of different approaches - nominal weld stress, effective notch stress concepts, and 2D linear elastic fracture mechanics (LEFM) - for the fatigue strength assessment of weld root capacity is evaluated. Furthermore, a parametric LEFM analysis is used to evaluate the effect of weld penetration on the root fatigue strength capacity in axial and bending loading. The results indicate that in the case of bending, nominal weld stress can be calculated using the linear stress distribution over the joint section and FAT36 as a reference curve. In the bending loading, for the joints failing from the weld toe, a mean fatigue strength of up to 185 MPa in the nominal stress system was achieved, indicating that the reference curve FAT63 is overly conservative. The ENS concept with FAT225 seemed to be slightly unconservative for assessing the root fatigue strength capacity. LEFM analyses revealed that in the case of increasing weld penetration and bending loading, weld root fatigue strength capacity seemed to correlate with the nominal weld stress calculated using effective weld throat thickness, while in axial loading, weld stress should be calculated using external throat thickness summed with penetration length.

  • 4.
    Alabbasi, Sateh
    et al.
    Qatar University, Qatar.
    Hussein, Mohammed
    Qatar University, Qatar.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Avci, Onur
    University of Leeds, UK.
    A numerical and experimental investigation of a special type of floating-slab tracks2020In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 215, article id 110734Article in journal (Refereed)
    Abstract [en]

    Floating-Slab Tracks (FST) are predominantly used for mitigating railway-induced vibrations where the concrete slab is mounted on soft resilient bearings to provide vibration isolation. This paper presents a research study on the dynamic behavior of a special type of FST used in the recently built subway system in Doha, Qatar. The special FST has a continuous concrete slab with periodic grooves. Therefore, the track can be modeled as a periodic structure with a slab unit having two elements with different cross-sections. Extensive numerical and experimental investigations were conducted on a multi-unit full-scale mockup track representing the special FST. A fast running model based on the Dynamic Stiffness Method was developed and examined, in an initial numerical exercise, against a detailed Finite Element model for a track with a finite length. In the experimental campaign, a test was performed with an impact hammer to identify the actual vibration response of the mockup track. Results from the experimental investigations were then used for model updating of the fast running model. The model updating process was carried out according to an automated hybrid optimization approach that combines genetic algorithms with a local search method. Finally, the updated model was extended to an infinite model to investigate the influence of varying grooves thickness on the dynamic behavior of the special track with infinite length for both bending and torsion scenarios. The investigations suggested that reducing the thickness below 50% of the full thickness of the slab significantly affects the dynamic behavior of the special FST.

  • 5. 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.

  • 6.
    Andersen, Michael Styrk
    et al.
    University of Southern Denmark, Denmark.
    Johansson, Jens
    University of Southern Denmark, Denmark.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Hansen, Svend Ole
    University of Southern Denmark, Denmark ; Svend Ole Hansen ApS, Denmark.
    Aerodynamic stability of long span suspension bridges with low torsional natural frequencies2016In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 120, p. 82-91Article in journal (Refereed)
    Abstract [en]

    Classical flutter of suspended bridge decks can be avoided if the torsional frequencies are lower than the vertical. Wind tunnel tests of single boxes and twin box section models with torsional natural frequencies above and below the vertical frequency has been conducted. Flutter was avoided in all tests where the torsional frequency was lower than the vertical. But too low torsional stiffness caused large static displacements of the girder at medium–high wind speeds and steady state oscillations driven by a combination of torsional divergence and stalling behavior at the critical wind seed. In order to design aerodynamically stable suspension bridges with low torsional natural frequencies it is suggested to increase the mass moment of inertia and provide adequate torsional stiffness by the main cables spacing.

  • 7.
    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

  • 8.
    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.

  • 9.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Architecture and Civil Engineering, Division of Structural Engineering, Chalmers University of Technology.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Challamel, Noël
    Université de Bretagne Sud, UBS – Institut Dupuy de Lôme, Centre de Recherche.
    A weak shear web model for deflection analysis of deep composite box-type beams2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 155, p. 36-49Article in journal (Refereed)
    Abstract [en]

    Deep box-type beams, consisting of framing members and sheathings, are sensitive to shear deformations and hence appropriate refined theories or complicated magnification factors are needed to be used to obtain accurate results. For sheathings or webs between the framing members that are weak in shear, additional shear deformations occur corresponding to the relative axial displacement between the framing members. These sandwich-type or partial interaction-type of in-plane shear behaviour between the framing members, needs to be taken into account, especially when the web shear stiffness is very low. The composite box-type beam treated here is composed of three framing members with sheathings on both sides. To incorporate effects of the sheathings shear deformations between the framing members on the deflection, the sheathings, here called web interlayers, are modelled as shear media with equivalent slip moduli corresponding to a partially interacting composite beam model. Governing equilibrium equations of the model are obtained using the minimum total potential energy principle and solved explicitly. The obtained results are compared with those based on different conventional beam theories and 3-D finite element (FE) simulations. It is shown that the model is capable of predicting accurately the deflection for a wide range of geometry and property parameters. It is demonstrated that the deflection of such deep box-type beams can be expressed as the summation of three different effects, namely bending deformations, conventional shear deformations in the framing members and sheathings, and additional in-plane shear deformations or shear slips of the weak web causing relative axial displacements between the framing members.

  • 10.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilimaa, jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    In-situ methods to determine residual prestress forces in concrete bridges2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 135, p. 41-52Article in journal (Refereed)
    Abstract [en]

    Levels of residual prestress forces are key parameters when assessing the structural behaviour of existing prestressed concrete bridges. However, these parameters are often unknown and not easy to determine. To explore them, two existing non-destructive and destructive approaches have been further developed for practical application and demonstrated on a multi-span continuous girder bridge. The evaluation of the prestress forces was part of an extensive experimental programme aimed to calibrate and develop assessment methods. Due to the pursuit of practical applications for existing bridges, the main focus was on non-destructive methodology, combining experimental data and finite element modelling to obtain the residual prestress forces. Assuming that the initial prestress force corresponded to 85% of the characteristic 0.2% proof strength of the reinforcing steel, estimated losses in investigated sections ranged between 5 and 70%. However, determined residual prestress forces were generally higher than theoretically based estimates accounting for friction and time-dependent losses in the prestressing system. In addition to describing in detail the methods for prestress evaluation, this paper presents suggestions for improvements and further studies, based on experiences from the field tests.

  • 11.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    O'Connor, Alan
    Department of Civil, Structural and Environmental Engineering, Trinity College Dublin.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Pedersen, Claus
    Department of Bridges, Rambøll Danmark A/S.
    Moment redistribution in RC beams: A study of the influence of longitudinal and transverse reinforcement ratios and concrete strength2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 80, p. 11-23Article in journal (Refereed)
    Abstract [en]

    In this paper, the results from an experimental programme, aimed at investigating moment redistribution in statically indeterminate reinforced concrete structures, are presented and compared with theoretical analysis of the structural behaviour. Due to the nonlinear structural behaviour of reinforced concrete structures, linear elastic analysis can lead to an inaccurate assessment of the behaviour and, therefore, it can become necessary to use more advanced methodologies to achieve sufficiently accurate analysis. Furthermore, more advanced methods can enable a higher degree of performance optimisation of structures than those resulting from the simplified approaches adopted by existing design codes based on linear elastic analysis with redistribution of internal forces. In order to assess the load-carrying capacity at the ultimate limit state (ULS), a model combining plastic and nonlinear analysis is presented. The evolution of moment redistribution to structural collapse was studied experimentally for continuous two-span beams. The focus of the experiments was on the influence of the longitudinal tensile reinforcement ratio at the intermediate support, the transverse reinforcement ratio and the concrete strength. The experimental response at the ULS was further compared with the predicted distribution of internal forces according to the theoretical model. Evaluation of the experimental study indicated a highly nonlinear structural behaviour of the tested beams with the distribution of moment differing from linear elastic analysis, even for low load levels. The evolution of moment redistribution and the moment redistribution at the ULS were appreciably dependent on the arrangement of longitudinal reinforcement, whilst the transverse reinforcement ratio had a marginal impact up to yielding of the longitudinal reinforcing steel, with the concrete strength slightly reducing the degree of moment redistribution. For those beams which failed in flexure, predictions from the theoretical model presented were in good agreement with the experimental results. However, several beams collapsed in shear-related failure modes.

  • 12.
    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.

  • 13.
    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.

  • 14.
    Blomfors, Mattias
    et al.
    Chalmers University of Technology, Sweden.
    Larsson Ivanov, Oskar
    Lund University, Sweden.
    Honfi, Daniel
    RISE - Research Institutes of Sweden, Built Environment, Building Technology.
    Engen, Morten
    Multiconsult ASA; NTNU, Norway.
    Partial safety factors for the anchorage capacity of corroded reinforcement bars in concrete2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 181, p. 579-588Article in journal (Refereed)
    Abstract [en]

    Many reinforced concrete bridges in Europe and around the world are damaged by reinforcement corrosion and the annual maintenance costs are enormous. It is therefore important to develop reliable methods to assess the structural capacity of corroded reinforced concrete structures and avoid unnecessary maintenance costs. Although there are advanced models for determining the load carrying capacity of structures, it is not obvious how they should be used to verify the performance of existing structures. To confidently assess the bond of corroded reinforcement in concrete, for example, the calculation model must give a sufficient safety margin. When designing new structures, semi-probabilistic approaches (such as the partial safety factor method) are adopted to achieve the target reliabilities specified in structural design codes. This paper uses probabilistic methods to develop partial factors for application in an existing bond model, to assess the safety of corroded reinforced concrete structures. The response of the bond model was studied using Monte Carlo (MC) simulations for several design cases, with probability distributions fitted to the results. Partial factors were then derived, based on these distributions. Furthermore, an MC-based simulation technique called “importance sampling” was used to study the reliability of several deterministic bond assessments conducted using these partial factors. The results show that deterministic assessments which use the proposed partial factors lead to a safety level at least equal to the target value. The results presented in this paper will support the assessment of reinforced concrete structures with anchorage problems and give a reasonable approximation of the anchorage capacity with sufficient safety margin. When generalised to cover other failure modes and structural configurations, this will enable better utilisation of damaged structures and lead to major environmental and economical savings for society.

  • 15.
    Blomfors, Mattias
    et al.
    RISE - Research Institutes of Sweden, Built Environment, CBI Swedish Cement and Concrete Research Institute. Chalmers University of Technology, Sweden.
    Zandi, Kamyab
    Chalmers University of Technology, Sweden.
    Lundgren, Karin
    Chalmers University of Technology, Sweden.
    Coronelli, Dario
    Politecnico di Milano, Italy.
    Engineering bond model for corroded reinforcement2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 156, p. 394-410Article in journal (Refereed)
    Abstract [en]

    Corrosion of the reinforcement in concrete structures affects their structural capacity. This problem affects many existing concrete bridges and climate change is expected to worsen the situation in future. At the same time, assessment engineers lack simple and reliable calculation methods for assessing the structural capacity of structures damaged by corrosion. This paper further develops an existing model for assessing the anchorage capacity of corroded reinforcement. The new version is based on the local bond stress-slip relationships from fib Model Code 2010 and has been modified to account for corrosion. The model is verified against a database containing the results from nearly 500 bond tests and by comparison with an empirical model from the literature. The results show that the inherent scatter among bond tests is large, even within groups of similar confinement and corrosion level. Nevertheless, the assessment model that has been developed can represent the degradation of anchorage capacity due to corrosion reasonably well. This new development of the model is shown to represent the experimental data better than the previous version; it yields similar results to an empirical model in the literature. In contrast to many empirical models, the model developed here represents physical behaviour and shows the full local bond stress-slip relationship. Using this assessment model will increase the ability of professional engineers to estimate the anchorage capacity of corroded concrete structures.

  • 16.
    Bolmsvik, Åsa
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Damping Assessment of Light Wooden Assembly With and Without Damping Material2013In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 49, p. 434-447Article in journal (Refereed)
    Abstract [en]

    Damping elastomers are often used in lightweight wooden constructions and are believed to have good sound insulating effects. In the present study the influence on the structural behaviour by using elastomer damping material (Sylomer®) in the joints, with particular respect to footsteps and floor vibrations, has been investigated. A full scale wooden mock-up was assembled with two different joint configurations and studied under free-free boundary conditions. In the first configuration, the joints between the floor and underlying walls were screwed together. In the second configuration the floor was resting free on top of ribs of elastomer damping material, equivalent to normal building practice when this material is used. Both configurations were analysed and evaluated using experimental modal analysis, in the frequency interval 10-115 Hz.

     

    The relative (viscous) damping ratios of the modes were found to be on average 1.2% for the screwed configuration and 2.1% for the configuration with elastomer damping material in the joints. The damping was found to vary significantly between modes in the elastomer case. It was found that at low frequencies damping was high for modes with large motion on the edge where the elastomer material was. At higher frequencies (above approx. 40 Hz), however, the damping for this configuration decreased. This is believed to be caused by a vibration isolation effect of the elastomer, decoupling the floor from the walls at higher frequencies.

     

    To assess the differences in vibration levels between the two configurations, mean acceleration levels of well spread points on the different building parts where computed and evaluated. It was found that above approximately 70 Hz, the mean vibration level in the elastomer configuration was significantly lower than for the screwed configuration. Below 70 Hz, however, for many frequencies the mean vibration level for the elastomer configuration was significantly higher than for the screwed configuration (as should be expected in vibration isolation). Problems with springiness and footsteps are due to loads in the frequency range of 10 to 50 Hz, this could indicate that elastomers, used as in the present study, could worsen these types of problems, although improving higher frequency acoustic performance.

  • 17.
    Bolmsvik, Åsa
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Linderholt, Andreas
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Ekevid, Torbjörn
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    FE Modelling of Light Weight Wooden Assemblies: parameter study and comparison between analyses and experiments2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 73, p. 125-142Article in journal (Refereed)
    Abstract [en]

    A finite element (FE) analysis of a model representing a mock-up structure previously investigated experimentally is investigated in this study. The aim is to make a correlation and calibration between test and analysis of the full scale wooden structure; both eigenmodes and acceleration levels are compared. Large scatter is found in material properties used for light weight wooden structures in literature. In this study, a parameter evaluation is therefore made to show how different properties influence the dynamic behaviour of the structure. It is shown that the wood beam material properties influence the behaviour of the light weight wooden structure FE model most.

    Two types of junctions are modelled and evaluated; a tied connection is used to simulate screwed junctions and spring/dashpot elements are used to represent elastomer junctions between the floor and the walls. The springs and dashpots used to model the elastomer in the junction work well in the bearing direction but need to be improved to obtain correct rotational stiffness, shear motion and friction. There are still many unknown parameters in a complex wooden structure that remain to be investigated. However, the results presented in this paper add data to be used for FE modelling of a complex wooden structure.

  • 18.
    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.

  • 19.
    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.

  • 20. Challamel, Noel
    et al.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lateral-torsional buckling of vertically layered composite beams with interlayer slip under uniform moment2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 34, p. 505-513Article in journal (Refereed)
    Abstract [en]

    The lateral-torsional stability of vertically layered composite beams with interlayer slip is investigated in this paper, based on a variational approach. Vertically layered elements are typically used in timber engineering but also in case of laminated glass elements. Both across-longitudinal or vertical slip due to rotation and longitudinal or horizontal slip due to lateral deflection are discussed. The theoretical framework of the lateral-torsional buckling problem is given, and some engineering closed-form solutions are presented for partially composite beams under uniform bending moment. Simplified kinematical relationships neglecting the axial and vertical displacements of the sub-elements give unrealistic values for the lateral-torsional buckling moment. Refined kinematical assumptions remove this peculiarity and render sound buckling moment results. Inclusion of the horizontal and vertical slips significantly affect the lateral-torsional buckling moment of these vertically laminated elements. A single lateral-torsional buckling formulae is derived, depending on both the horizontal and the vertical connection parameters. (C) 2011 Elsevier Ltd. All rights reserved.

  • 21. Challamel, Noel
    et al.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology.
    Variationally-based theories for buckling of partial composite beam-columns including shear and axial effects2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 8, p. 2297-2319Article in journal (Refereed)
    Abstract [en]

    This paper is focused on elastic stability problems of partial composite columns: the conditions for the axial load not to introduce any pre-bending effects in composite columns; the equivalence, similarities and differences between different sandwich and partial composite beam theories with and without the effect of shear, with and without the effect of axial extensibility, and also the effect of eccentric axial load application. The basic modelling of the composite beam-column uses the Euler-Bernoulli beam theory and a linear constitutive law for the slip. In the analysis of this reference model, a variational formulation is used in order to derive relevant boundary conditions. The specific loading associated with no pre-bending effects before buckling is geometrically characterized, leading to analytical buckling loads of the partial composite column. The equivalence between the Hoff theory for sandwich beam-columns, the composite action theory for beam-columns with interlayer slip and the corresponding Bickford-Reddy theory, is shown from the stability point of view. Special loading configurations including eccentric axial load applications and axial loading only on one of the sub-elements of the composite beam-column are investigated and the similarity of the behaviour to that of imperfect ordinary beam-columns is demonstrated. The effect of axial extensibility on kinematical relationships (according to the Reissner theory), is analytically quantified and compared to the classical solution of the problem. Finally, the effect of incorporating shear in the analysis of composite members using the Timoshenko theory is evaluated. By using a variational formulation, the buckling behaviour of partial composite columns is analysed with respect to both the Engesser and the Haringx theory. A simplified uniform shear theory (assuming equal shear deformations in each sub-element) for the partial composite beam-column is first presented, and then a refined differential shear theory (assuming individual shear deformations in each sub-element) is evaluated. The paper concludes with a discussion on this shear effect, the differences between the shear theories presented and when the shear effect can be neglected. 

  • 22.
    Challamel, Noël
    et al.
    Université Européenne de Bretagne.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lateral-torsional buckling of vertically layered composite beams with interlayer slip under uniform moment2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 34, p. 505-513Article in journal (Refereed)
    Abstract [en]

    The lateral-torsional stability of vertically layered composite beams with interlayer slip is investigated in this paper, based on a variational approach. Vertically layered elements are typically used in timber engineering but also in case of laminated glass elements. Both across-longitudinal or vertical slip due to rotation and longitudinal or horizontal slip due to lateral deflection are discussed. The theoretical framework of the lateral-torsional buckling problem is given, and some engineering closed-form solutions are presented for partially composite beams under uniform bending moment. Simplified kinematical relationships neglecting the axial and vertical displacements of the sub-elements give unrealistic values for the lateral-torsional buckling moment. Refined kinematical assumptions remove this peculiarity and render sound buckling moment results. Inclusion of the horizontal and vertical slips significantly affect the lateral-torsional buckling moment of these vertically laminated elements. A single lateral-torsional buckling formulae is derived, depending on both the horizontal and the vertical connection parameters.

  • 23.
    Challamel, Noël
    et al.
    University of Europeenne Bretagne, Laboratory Genie Civil & Genie Mecan.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Variationally-based theories for buckling of partial composite beam-columns including shear and axial effects2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 8, p. 2297-2319Article in journal (Refereed)
    Abstract [en]

    This paper is focused on elastic stability problems of partial composite columns: the conditions for the axial load not to introduce any pre-bending effects in composite columns; the equivalence, similarities and differences between different sandwich and partial composite beam theories with and without the effect of shear, with and without the effect of axial extensibility, and also the effect of eccentric axial load application. The basic modelling of the composite beam-column uses the Euler-Bernoulli beam theory and a linear constitutive law for the slip. In the analysis of this reference model, a variational formulation is used in order to derive relevant boundary conditions. The specific loading associated with no pre-bending effects before buckling is geometrically characterized, leading to analytical buckling loads of the partial composite column. The equivalence between the Hoff theory for sandwich beam-columns, the composite action theory for beam-columns with interlayer slip and the corresponding Bickford-Reddy theory, is shown from the stability point of view. Special loading configurations including eccentric axial load applications and axial loading only on one of the sub-elements of the composite beam-column are investigated and the similarity of the behaviour to that of imperfect ordinary beam-columns is demonstrated. The effect of axial extensibility on kinematical relationships (according to the Reissner theory), is analytically quantified and compared to the classical solution of the problem. Finally, the effect of incorporating shear in the analysis of composite members using the Timoshenko theory is evaluated. By using a variational formulation, the buckling behaviour of partial composite columns is analysed with respect to both the Engesser and the Haringx theory. A simplified uniform shear theory (assuming equal shear deformations in each sub-element) for the partial composite beam-column is first presented, and then a refined differential shear theory (assuming individual shear deformations in each sub-element) is evaluated. The paper concludes with a discussion on this shear effect, the differences between the shear theories presented and when the shear effect can be neglected. (C) 2011 Elsevier Ltd. All rights reserved.

  • 24.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    de Borst, Karin
    Eberhardsteiner, Josef
    Experiments on dowel-type timber connections2013In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 47, p. 67-80Article in journal (Refereed)
    Abstract [en]

    Dowel-type connections are commonly used in timber engineering for a large range of structural applications. The current generation of design rules is largely based on empiricism and testing and lacks in many parts a stringent mechanical foundation. This often blocks an optimized use of the connections, which is essential for the design of economically efficient structures. Moreover, it severely limits the applicability of the design rule, such as restrictions regarding splitting behavior or maximum ductility (e.g. maximum allowable deformations) are missing. Therefore, the demands due to a large and quickly evolving variety of structural designs in timber engineering are not reflected. The aim of this work is to study the load-carrying behavior of the connection in detail, including all loading stages, from the initial contact between dowel and wood up to the Ultimate load and failure. Distinct features during first loading as well as during unloading and reloading cycles are identified and discussed. The knowledge of the detailed load-carrying behavior is essential to understanding the effects of individual parameters varied in relation to the material and the connections design. The suitability of the current design rules laid down in Eurocode 5 (EC5) is assessed and deficiencies revealed. Tests on 64 steel-to-timber dowel-type connections loaded parallel to the fiber direction were performed. The connections were single-dowel connections with dowels of twelve millimeter diameter. The test specimens varied in wood density and geometric properties. Additionally, the effects of dowel roughness and lateral reinforcement were assessed. The experiments confirmed that connections of higher density show significantly higher ultimate loads and clearly evidenced that they are more prone to brittle failure than connections using light wood. The latter usually exhibit a ductile behavior with an extensive yield plateau until final failure occurs. With increased dowel roughness, both, ultimate load and ductility are increased. The test results are compared with corresponding design values given by EC5 for the strength and the stiffness of the respective single-dowel connections. For connections of intermediate slenderness, EC5 provided conservative design values for strength. Nevertheless, in some of the experiments the design values overestimated the actual strengths considerably in connections of low as well as high slenderness. As for the stiffness, a differentiation according to the connection width is missing, which gives useful results only for intermediate widths. Furthermore, the test results constitute valuable reference data for validating numerical simulation tools, which are currently a broad field of intensive interest.

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  • 25. Dvinskikh, Sergey
    et al.
    Henriksson, Marielle
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek.
    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)
  • 26.
    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.

  • 27.
    Edskär, Ida
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Dynamic Properties of Cross-Laminated Timber and Timber Truss Building Systems2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 186, p. 525-535Article in journal (Refereed)
    Abstract [en]

    Incorrect prediction of dynamic properties of tall buildings can lead to discomfort for humans. It is therefore important to understand the dynamic characteristics such as natural frequency, mode shape and damping and the influence they have on acceleration levels. The aim of this study is to compare two timber building system, one with cross laminated panels and one with post-and-beam elements with diagonals for stabilisation. Empirical formulae for predicting the natural frequency and mode shape are compared to measured and numerical results. Tall building assumptions such as ‘line-like’ behaviour and lumped mass at certain points were evaluated for both systems. The post-and-beam system showed a stiffer behaviour than the cross laminated system where more shear deformation occurred. Empirical formulae should be used with care until more data is collected.  For the post-and-beam systems an assumption of linearity may be appropriate, but for cross laminated systems the approximation can give results on the unsafe side. Finally, the relationship between stiffness and mass for cross laminated timber systems and its effect on dynamic properties needs to be further investigated.

  • 28. Fall, David
    et al.
    Shu, Jiangpeng
    Two-way slabs: Experimental investigation of load redistributions in steel fibre reinforced concrete2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 80, p. 61-74Article in journal (Refereed)
    Abstract [en]

    In the design of two-way reinforced concrete slabs, e.g. using the strip or yield line design method, the possibility of redistributing the load between different loading directions is used. The main aim of the present study was to investigate how fibres affect the structural behaviour such as the possibility for redistribution, crack patterns and load-carrying capacity. The investigation was conducted by means of experiments on two-way octagonal slabs, simply supported on four edges, centrically loaded with a point load. The slabs spanned 2.2m in both directions and the reinforcement amount was twice as large in one direction as in the other, in order to provoke uneven load distribution. Three slabs of each reinforcement configuration were produced and tested: conventionally reinforced slabs, steel fibre reinforced slabs and a combination of both reinforcement types. The reaction force on each supported edge was measured on five rollers per edge. A moderate fibre content (35kg/m3) of double hook-end steel fibres was used. The steel fibres affected the structural behaviour significantly by providing post-cracking ductility and by increasing the ultimate load-carrying capacity by approximately 20%. Most significant, the steel fibres influenced the load redistribution in such a way that more load could be transferred to supports in the weaker direction after cracking. Further, more evenly distributed support reactions were obtained in the slabs containing both reinforcement types compared to the case when only conventional reinforcement was used. The slabs reinforced by steel fibres alone did not experience any bending hardening; however, a considerable post-cracking ductility was observed. Furthermore, the work presented in this paper will provide results suitable for use in benchmarking numerical and analytical modelling methods for steel fibre reinforced concrete, as the experimental programme also included extensive testing of material properties.

  • 29.
    Gervásio, Helena
    et al.
    ISISE, Department of Civil Engineering, University of Coimbra.
    Rebelo, Carlos
    ISISE, Department of Civil Engineering, University of Coimbra.
    Moura, André
    ISISE, Department of Civil Engineering, University of Coimbra.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Silva, Luis Simões da
    ISISE, Department of Civil Engineering, University of Coimbra.
    Comparative life cycle assessment of tubular wind towers and foundations: Part 2: Life cycle analysis2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 74, p. 292-299Article in journal (Refereed)
    Abstract [en]

    In the first part of the paper the design of tubular towers and respective onshore foundations was addressed. The considered solutions were based on steel, concrete and hybrid steel-concrete tubular towers supporting multi-megawatt turbines of 2, 3.6 and 5 MW power with hub heights of 80, 100 and 150 m respectively. In this second part of the paper, the life cycle analysis of the designed case studies is performed and conclusions about their environmental impact are drawn. Two different scenarios concerning the lifetime of the towers were established. The first scenario considers 20 years lifetime and two different construction methods for the connection of the steel segments, the first based in current technology using flange connections and the second using newly developed friction connections. Assuming equal importance for all environmental categories in this scenario, it may be concluded that for heights up to 100 m hybrid towers with friction connections are the most efficient solution. For higher heights, the concrete tower becomes more efficient. The second scenario considers an increased total lifetime of 40 years, assuming the reuse of the tower after 20 years of operation. In this case, the use of friction connections in steel towers enhances the possibility of dismantling and reusing the tower potentiating much better performance in relation to the environmental category of global warming.

  • 30.
    Gečys, Tomas
    et al.
    Vilnius Gediminas Technical University, Lithuania.
    Daniunas, Alfonsas
    Vilnius Gediminas Technical University, Lithuania.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Wagner, Leopold
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    3D finite element analysis and experimental investigations of a new type of timber beam-to-beam connection2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 86, p. 134-145Article in journal (Refereed)
    Abstract [en]

    Abstract A new type of semi-rigid timber beam-to-beam connection and its behavior under bending is presented. This connection consists of four identical steel parts, which are inserted into the timber beams in the tension and compression zone of the connection. These steel parts are easily connected by mounting bolts on the construction site. In order to avoid initial slip, gaps between the timber and the steel parts are filled using two different types of filler materials, namely cement based (CEM) or polyurethane based (PUR) filler. In this study, the connection is modeled by means of the Finite Element (FE) Method and the modeling results are compared to the results of an experimental assessment of the proposed connection under bending. The material model for timber encompasses a Hill criterion in combination with cohesive surface contact in order to depict both, yielding in compression and brittle failure in shear and tension perpendicular to the grain. The experimentally observed decisive failure mode, i.e. shear block failure, could be reproduced by the model. Subsequently, the FE model was used to investigate the effect of using different filler materials, or not considering the filler in the analysis at all. In addition, a particular influence of clamping bolts in the timber on the strength of the connection was revealed. The FE analysis excluding these bolts showed good agreement with the experiments in terms of the strength of the connection, while considering these bolts led to an overestimation of the strength. This is a consequence of the considerable influence of the clamping bolts on stresses perpendicular to the grain in the timber in the block-shear area, and therefore, on shear failure initiation. Using the CEM filler hardly changed the overall behavior of the connection as compared to the analyses without filler material, while the PUR filler leads to a less ductile overall behavior. This is well in line with experimental observations. The application of modeling approaches for timber has proven suitable for the analysis of such a type of timber beam-to-beam connection and, consequently, might be used for further optimization of this connection.

  • 31.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Jacquier, Nicolas
    Byggtekniska Byrån.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Stiffness model for inclined screws in shear-tension mode in timber-to-timber joints2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 136, p. 580-595Article in journal (Refereed)
    Abstract [en]

    A stiffness model for inclined screws in timber joints, or as shear connectors in composite timber-to-timber members, is presented. Elastic conditions applicable to the initial or linearized part of the load-deformation response in the serviceability limit state are assumed. The model for the stiffness or slip modulus is general in nature; it includes both the dowel (or shearing) action and withdrawal action of the screw, the friction between the members and it takes into account possible dissimilar properties and geometries of the different parts of the joint configuration. The model is simplified in the sense that the screw is assumed rigid and the withdrawal stresses along the length of the screw are assumed evenly distributed. However, the effects of flexibility and extensibility of the screw are taken into account by applying a theoretically derived correction factor for the embedment and withdrawal stiffness modulus, respectively. The proposed model is illustrated showing the total stiffness versus the inclination, as well as the relative contributing effect from the shearing and withdrawal stiffness, respectively, the influence of the friction coefficient. Also, the effect of dissimilar properties and geometries between the two parts of the joint is illustrated. Experimental verification of the proposed model is also given. Comparisons with other stiffness models are also made.

  • 32.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology.
    Jacquier, Nicolas
    Byggnadstekniska Byrån.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Stiffness model for inclined screws in shear-tension mode in timber-to-timber joints2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 136, p. 580-595Article in journal (Refereed)
    Abstract [en]

    A stiffness model for inclined screws in timber joints, or as shear connectors in composite timber-to timber members, is presented. Elastic conditions applicable to the initial or linearized part of the load deformation response in the serviceability limit state are assumed. The model for the stiffness or slip modulus is general in nature; it includes both the dowel (or shearing) action and withdrawal action of the screw, the friction between the members and it takes into account possible dissimilar properties and geometries of the different parts of the joint configuration. The model is simplified in the sense that the screw is assumed rigid and the withdrawal stresses along the length of the screw are assumed evenly distributed. However, the effects of flexibility and extensibility of the screw are taken into account by applying a theoretically derived correction factor for the embedment and withdrawal stiffness modulus, respectively. The proposed model is illustrated showing the total stiffness versus the inclination, as well as the relative contributing effect from the shearing and withdrawal stiffness, respectively, the influence of the friction coefficient. Also, the effect of dissimilar properties and geometries between the two parts of the joint is illustrated. Experimental verification of the proposed model is also given. Comparisons with other stiffness models are also made. (C) 2017 Elsevier Ltd. All rights reserved.

  • 33. Girhammar, Ulf Arne
    et al.
    Källsner, Bo
    SP- Sveriges Tekniska Forskningsinstitut, Trätek.
    Elasto-plastic model for analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 9, p. 2182-2193Article in journal (Refereed)
    Abstract [en]

    In order to stabilize timber-framed buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with the influence of imperfections such as gaps and uplift on the stiffness and the horizontal displacement of fully anchored shear walls. The significance of analyzing the effects of imperfections is evident when evaluating the stiffness of shear walls; tests of walls show that the horizontal displacement is underestimated in calculations using the stiffness of sheathing-to-framing joints as obtained from experiments. Also, in real structures where hold-downs are used, the influence of gaps and uplift should be included in order to obtain realistic displacements in the serviceability limit state. The analytical model is based on ideal plastic behavior of the mechanical sheathing-to-timber joints with stresses parallel to the perimeter of the frame and on linear elastic behavior for stresses perpendicular to the bottom rail. Using this elasto-plastic model, the equations for the stiffness and the deflection versus the number of segments in the wall are derived. The fully anchored condition for the shear walls is simulated by applying a diagonal load to the shear wall. Three types of imperfections are evaluated: Walls with gaps at all studs, a gap only at the trailing stud, and gaps at all studs, except at the trailing stud. It is shown that the effect of imperfections on the stiffness of the wall in the initial stage is considerable. Depending on the distribution of the gaps and the number of segments included in the shear wall, the displacement of the shear wall is increased several times compared to that of a fully anchored wall diaphragm with no gaps; e.g. for a single segment wall more than four times. However, for walls with more than six segments the effect of imperfections can be neglected. Finally, the theoretical model is experimentally verified.

  • 34. Girhammar, Ulf Arne
    et al.
    Källsner, Bo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Elasto-plastic model for analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 9, p. 2182-2193Article in journal (Refereed)
  • 35.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Källsner, Bo
    Elasto-plastic model for analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 9, p. 2182-2193Article in journal (Refereed)
    Abstract [en]

    In order to stabilize timber-framed buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with the influence of imperfections such as gaps and uplift on the stiffness and the horizontal displacement of fully anchored shear walls. The significance of analyzing the effects of imperfections is evident when evaluating the stiffness of shear walls; tests of walls show that the horizontal displacement is underestimated in calculations using the stiffness of sheathing-to-framing joints as obtained from experiments. Also, in real structures where hold-downs are used, the influence of gaps and uplift should be included in order to obtain realistic displacements in the serviceability limit state. The analytical model is based on ideal plastic behavior of the mechanical sheathing-to-timber joints with stresses parallel to the perimeter of the frame and on linear elastic behavior for stresses perpendicular to the bottom rail. Using this elasto-plastic model, the equations for the stiffness and the deflection versus the number of segments in the wall are derived. The fully anchored condition for the shear walls is simulated by applying a diagonal load to the shear wall. Three types of imperfections are evaluated: Walls with gaps at all studs, a gap only at the trailing stud, and gaps at all studs, except at the trailing stud. It is shown that the effect of imperfections on the stiffness of the wall in the initial stage is considerable. Depending on the distribution of the gaps and the number of segments included in the shear wall, the displacement of the shear wall is increased several times compared to that of a fully anchored wall diaphragm with no gaps; e.g. for a single segment wall more than four times. However, for walls with more than six segments the effect of imperfections can be neglected. Finally, the theoretical model is experimentally verified.

  • 36.
    Girhammar, Ulf Arne
    et al.
    Department of TFE-Civil Engineering, Faculty of Science and Technology, Umeå University.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Elasto-plastic model for analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 9, p. 2182-2193Article in journal (Refereed)
    Abstract [en]

    In order to stabilize timber-framed buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with the influence of imperfections such as gaps and uplift on the stiffness and the horizontal displacement of fully anchored shear walls. The significance of analyzing the effects of imperfections is evident when evaluating the stiffness of shear walls; tests of walls show that the horizontal displacement is underestimated in calculations using the stiffness of sheathing-to-framing joints as obtained from experiments. Also, in real structures where hold-downs are used, the influence of gaps and uplift should be included in order to obtain realistic displacements in the serviceability limit state. The analytical model is based on ideal plastic behavior of the mechanical sheathing-to-timber joints with stresses parallel to the perimeter of the frame and on linear elastic behavior for stresses perpendicular to the bottom rail. Using this elasto-plastic model, the equations for the stiffness and the deflection versus the number of segments in the wall are derived. The fully anchored condition for the shear walls is simulated by applying a diagonal load to the shear wall. Three types of imperfections are evaluated: Walls with gaps at all studs, a gap only at the trailing stud, and gaps at all studs, except at the trailing stud. It is shown that the effect of imperfections on the stiffness of the wall in the initial stage is considerable. Depending on the distribution of the gaps and the number of segments included in the shear wall, the displacement of the shear wall is increased several times compared to that of a fully anchored wall diaphragm with no gaps; e.g. for a single segment wall more than four times. However, for walls with more than six segments the effect of imperfections can be neglected. Finally, the theoretical model is experimentally verified

  • 37.
    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.

  • 38.
    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.

  • 39.
    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)
  • 40.
    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.

  • 41.
    Hochreiner, Georg
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Structural behaviour and design of dowel groups: experimental and numerical identification of stress states and failure mechanisms of the surrounding timber matrix2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 131, p. 421-437Article in journal (Refereed)
    Abstract [en]

    Dowel-type fasteners in combination with steel plates are widely used in engineered timber structures. Since dowel groups are designed as semi-rigid connections subjected to an arbitrary set of internal forces, the corresponding structural behaviour of the surrounding timber matrix must be considered in the design process accordingly, including the effect of reinforcements. Corresponding stress states and failure mechanisms in the timber matrix of dowel groups are discussed herein. Surface strain fields from tests of dowel groups under complex loading situations were used to identify the sequence of cracking, as well as to assign the related failure modes. First cracking events were caused by stress peaks at the most loaded dowels and by a combination of shear stresses and stresses perpendicular to the grain, while later crack- ing events were associated with a predominant action of individual stress components. Thus, the non- linear global moment-relative rotation behaviour of dowel groups could be related to failure mechanisms in the surrounding timber matrix. The corresponding strain state was qualitatively as well as quantita- tively reproduced by means of a numerical model, which gave access to stresses in the timber matrix and has potential to be implemented as a sub-model in engineering design software. The numerical model supported the feasibility of a decomposition of the stress state due to the global bending moment into stresses caused by a couple of equal forces parallel and perpendicular to the grain, which could be used in the design process. Based on experimental and numerical findings, essential aspects for a design procedure for the timber matrix in dowel groups loaded by a combination of internal forces are proposed. 

  • 42.
    Huang, Zheng
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, China.
    Meng, Shaoping
    School of Civil Engineering, Southeast University, Nanjing, China.
    Bagge, Niklas
    Department of Bridge & Hydraulic Design, WSP Sverige AB, Gothenburg, Sweden.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Validation of a numerical method for predicting shear deformation of reinforced concrete beams2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 197, article id 109367Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to validate a 2D nonlinear finite element (FE) model for estimating the post-cracking shear deformation of reinforced concrete (RC) beams. The proposed FE model treated the cracked concrete as an orthotropic material in the framework of the fixed-crack approach. The experimental data for both the overall response (including the total and shear-induced deflection) and the detailed response (including the mean shear strain, mean vertical strain and principal compressive strain angle) of five I-section RC beams, monitored by the main authors of this paper with the Digital Image Correlation technique, were used to verify the proposed model. In addition, 27 further test beams evaluated in independent research programs were collected to assemble a database. The proposed FE model was further verified against the database. Two additional FE models (the rotating-crack model developed in this work and Response-2000 developed by Bentz (2000)) were also evaluated by simulating the detailed responses of the beams in the database. The results obtained validate the proposed FE model for predicting the post-cracking shear deformation of RC beams and indicate that the proposed FE model is more suitable for simulating the shear behaviour of RC beams than the rotating-crack model or Response-2000.

  • 43.
    Huang, Zheng
    et al.
    School of Civil Engineering, Southeast University,Nanjing, China.
    Tu, Yongming
    School of Civil Engineering, Southeast University,Nanjing, China.
    Meng, Shaoping
    School of Civil Engineering, Southeast University,Nanjing, China.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A practical method for predicting shear deformation of reinforced concrete beams2020In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 206, article id 110116Article in journal (Refereed)
    Abstract [en]

    This paper presents a practical method for predicting the deflections, including both the flexure and shear contributions, of reinforced concrete (RC) beams. The shear force - shear strain (V-γ) curve of a section in the shear span of RC beams is represented by a piecewise model and the tangent shear stiffness after shear cracking, Kt,cr, is assumed to be constant. A 2D finite element model, which has been validated for predicting shear deformation of RC beams, was used to identify factors that may affect the shear reduction factor (the ratio of Kt,cr to the elastic shear stiffness) and establish methodology for predicting the V-γ curve. Two types of methods, integration-form and closed-form, for predicting the total deflection were developed, in which the flexure-induced deflection (FD) was predicted using the Bischoff model while the shear-induced deflection (SD) was predicted using the method proposed in this paper. Comparison of the predictions with experimental results confirms that the Bischoff model provides reliable predictions of FDs of RC beams with and without shrinkage. It also shows that the proposed method can provide accurate predictions for SD after shear cracking, provided the effect of shrinkage on the shear cracking load is adequately quantified.

    Support from: National Natural Science Foundation of China (No. 51378104) and A Project Funded by the Priority Academic Program Development ofJiangsu Higher Education Institutions. The Development Fund of the Swedish Construction Industry (SBUF), the Swedish Research Council Formas and Elsa and Sven Thysell Foundation

  • 44.
    Huang, Zheng
    et al.
    School of Civil Engineering, Southeast University, Nanjing, China.
    Tu, Yongming
    School of Civil Engineering, Southeast University, Nanjing, China.
    Meng, Shaoping
    School of Civil Engineering, Southeast University, Nanjing, China.
    Sabau, Cristian
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Popescu, Cosmin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Infrastructure, Materials and Structures, Norut, Narvik, Norway.
    Experimental study on shear deformation of reinforced concrete beams using digital image correlation2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 181, p. 670-698Article in journal (Refereed)
    Abstract [en]

    This paper presents an experimental program aimed at providing reliable and comprehensive experimental data for assessing the available models of predicting the shear deformation of diagonally-cracked reinforced concrete (RC) beams. The non-contact measuring technique, Digital Image Correlation (DIC), was used to monitor the full-field displacement and strain in the shear span of five RC beams with thin webs. Virtual measuring grids were created to measure the mean shear strain and other critical deformation results which reflects the mechanism of shear deformation after shear cracking (i.e. the principal compressive strain angle, the principal compressive strain, the mid-depth longitudinal strain and the mean vertical strain). The experimental mean shear strain and other critical deformation results were compared with the predictions with several available models. The comparison indicates the available models fail to reproduce the principal compressive strain angle, the mid-depth longitudinal strain and the mean vertical strain which constitute the key parameters in estimating the shear deformation after shear cracking. As a result, significant discrepancies in the shear deformation of the beams tested in this paper are observed between the experimental and calculated results. It is also found that the predicted shear deformation of a number of beam specimens tested by other researchers with the available models deviates considerably from the experimental results. In general, the existing models are not capable of providing accurate predictions of the shear deformation of RC beams and further investigation into this topic is needed.

  • 45.
    Huo, Jinxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics. Sandvik Min & Rock Technol, R&D Dept Min Tools, SE-81181 Sandviken, Sweden.
    van Dijk, Nico P.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Elastic properties of rhombic mesh structures based on computational homogenisation2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 172, p. 66-75Article in journal (Refereed)
    Abstract [en]

    Flat mesh structures are used in a wide variety of applications. In particular, meshes with a rhombic unit cell are frequently employed due to their simplicity and relative ease of manufacture. This paper studies the in-plane elastic properties of such a structure as a function of the geometrical parameters by means of homogenisation techniques. We compare predicted elastic in-plane properties (i) including only bending mode of the struts, cf. Gibson-Ashby model, (ii) including both bending and stretching modes of the struts, obtained by homogenisation using beam elements and (iii) by homogenisation using beam-spring elements accounting additionally for strut joint deformation, and (iv) numerical results of elastic properties obtained by homogenisation using solid elements. The expressions of the predicted elastic properties are presented in analytical form. The homogenised elastic properties accounting for both bending and stretching matches very well with those from the model including only bending. The axial deformation of struts thus has negligible impact on the overall elastic behaviour. The complex deformation in the strut joint was also captured in the homogenised using beam-spring elements, and the results agree better with the solid element results. It is concluded that a finite-element-based homogenisation approach could serve as a straightforward analytical method to obtain elastic properties of mesh structures. This approach automatically includes all deformation mechanisms as opposed to the classical unit cell analyses of bending beams.

  • 46.
    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)
  • 47.
    Jarnerö, Kirsi
    et al.
    Technical Research Institute of Sweden, SP Wood Technology, Vidéum Science Park,Växjö.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vibration properties of a timber floor assessed in laboratory and during construction2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 82, p. 44-54Article in journal (Refereed)
    Abstract [en]

    Natural frequencies, damping ratios and mode shapes of a prefabricated timber floor element have been assessed experimentally in laboratory with different boundary conditions and in situ (in field) at different stages of construction. In laboratory the change in modal parameters was studied with free-free boundary conditions and simply supported on two sides. Three different simply supported tests with changes in boundary conditions were carried out; the floor placed on the support without any fastening or interlayer between support and floor, the floor screwed to the supports and the floor placed on an elastic interlayer between support and floor. The in situ tests were carried out first on the single floor element and then on the entire floor of the room into which the floor element was built in. The damping ratio of the floor increased from 1% to 3% when simply supported in laboratory to approximately 5% when placed upon a polyurethane interlayer (Sylodyn) in situ, and to approximately 6% when fully integrated in the building. Thus the in situ conditions have considerable influence on the damping and the values assessed are very high in comparison with damping values suggested in design codes. Regarding natural frequencies it was concluded that the major change in these occur as the floor element is coupled to the adjacent elements and when partitions are built in the studied room, the largest effect is on those modes of vibration that are largely constrained in their movement.

  • 48.
    Jarnerö, Kirsi
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Brandt, Anders
    University of Southern Denmark, Denamark.
    Olsson, Anders
    Linnaeus University, Sweden.
    Vibration properties of a timber floor assessed in laboratory and during construction2015In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 82, p. 44-54Article in journal (Refereed)
    Abstract [en]

    Natural frequencies, damping ratios and mode shapes of a prefabricated timber floor element have been assessed experimentally in laboratory with different boundary conditions and in situ (in field) at different stages of construction. In laboratory the change in modal parameters was studied with free-free boundary conditions and simply supported on two sides. Three different simply supported tests with changes in boundary conditions were carried out; the floor placed on the support without any fastening or interlayer between support and floor, the floor screwed to the supports and the floor placed on an elastic interlayer between support and floor. The in situ tests were carried out first on the single floor element and then on the entire floor of the room into which the floor element was built in. The damping ratio of the floor increased from 1% to 3% when simply supported in laboratory to approximately 5% when placed upon a polyurethane interlayer (Sylodyn®) in situ, and to approximately 6% when fully integrated in the building. Thus the in situconditions have considerable influence on the damping and the values assessed are very high in comparison with damping values suggested in design codes. Regarding natural frequencies it was concluded that the major change in these occur as the floor element is coupled to the adjacent elements and when partitions are built in the studied room, the largest effect is on those modes of vibration that are largely constrained in their movement.

  • 49.
    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.

  • 50.
    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.

123 1 - 50 of 112
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