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  • 1.
    Aminbaghai, Mehdi
    et al.
    Vienna University of Technology, Austria.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology. Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Pichler, Bernhard
    Vienna University of Technology, Austria.
    A Matrix-Vector Operation-Based Numerical Solution Method for Linear m-th Order Ordinary Differential Equations: Application to Engineering Problems2013In: Advances in Applied Mathematics and Mechanics, ISSN 2070-0733, E-ISSN 2075-1354, Vol. 5, no 3, p. 269-308Article in journal (Refereed)
    Abstract [en]

    Many problems in engineering sciences can be described by linear, inhomogeneous, m-th order ordinary differential equations (ODEs) with variable coefficients. For this wide class of problems, we here present a new, simple, flexible, and robust solution method, based on piecewise exact integration of local approximation polynomials as well as on averaging local integrals. The method is designed for modern mathematical software providing efficient environments for numerical matrix-vector operation-based calculus. Based on cubic approximation polynomials, the presented method can be expected to perform (i) similar to the Runge-Kutta method, when applied to stiff initial value problems, and (ii) significantly better than the finite difference method, when applied to boundary value problems. Therefore, we use the presented method for the analysis of engineering problems including the oscillation of a modulated torsional spring pendulum, steady-state heat transfer through a cooling web, and the structural analysis of a slender tower based on second-order beam theory. Related convergence studies provide insight into the satisfying characteristics of the proposed solution scheme.

  • 2.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Esser, Gerold
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    The Historical Roof Structure of the Leopold Wing of the Vienna Hofburg Palace: Structural Assessment2015In: Proceedings of the International Conference on Structural Health Assessment of Timber Structures (SHATIS'15), 2015Conference paper (Refereed)
    Abstract [en]

    In this case study, the structural behaviour of the historic roof structure of the “Leopold Wing”, part of the Hofburg, the Vienna Imperial Palace, is assessed. The current appearance of the roof is a consequence of several adaptions and extensions of the original structure that dates back to the 17th century. The main part of the roof was reconstructed in the early 1670s following a disastrous fire in February 1668. The structure had the shape of an M-roof consisting of two adjacent gable roofs. Probably in the 19th century, the centre part was closed, creating a mansard roof over the entire width of the building. Basically, the geometry of the structure is symmetric with respect to the middle wall. However, since the position of the middle wall is partly asymmetric, also the roof structure becomes asymmetric. Herein, the influence of the building history on the load-deformation behaviour of the roof structure is investigated. Therefore, structural analyses of the original M-roof and of the mansard roof are performed. The modelling of the historic roof structure is based on a deformation-accurate survey. In addition, the influence of the nonlinear, compliant behaviour of connections on the load-deformation behaviour of the timber structure is taken into account. A considerable influence of the connection slip on the deformation of the structure becomes obvious from the analysis. Consequently, consideration of the nonlinear behaviour of the joints reveals a realistic load transfer within the structure. The addition of structural elements caused additional dead loads, which increase long-term deformations.

  • 3.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. TU Wien, Austria.
    Schweigler, M.
    TU Wien, Austria.
    Hochreiner, Georg
    TU Wien, Austria.
    Eberhardsteiner, Josef
    TU Wien, Austria.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Lund University, Sweden.
    Integrative Research for an Enhanced Design of Dowel Connections2015In: Proceedings of the EUROMECH Colloquium 556 on Theoretical, Numerical, and Experimental Analyses in Wood Mechanics, 2015Conference paper (Refereed)
  • 4.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Serrano, Erik
    Lund University, Sweden.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Experimental Assessment of the Load Distribution in Multi-Dowel Timber Connections2016In: 17th International Conference on Experimental Mechanics, Rhodes, Greece, July 3-7, 2016, 2016Conference paper (Other academic)
    Abstract [en]

    An integrative, hierarchically organized testing procedure for the quantification of the load distribution in multi-dowel timber connections is presented herein. The use of contactless deformation measurement systems allowed the combination of test data from single dowel and multi-dowel connections, which gave access to the loads acting on each dowel over the full loading history. As a consequence of the anisotropic material behavior of wood, a nonuniform and progressively changing load distribution among the dowels was found.

  • 5.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria .
    Hochreiner, Georg
    Vienna University of Technology, Austria .
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Lund University.
    Experimental characterization of the global and local behavior of multi-dowel LVL-connections under complex loading2016In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, no 6, p. 2407-2424Article in journal (Refereed)
    Abstract [en]

    The thorough experimental characterization of a dowel-type connection under various combinations of bending moments and normal forces is presented in this study. Double-shear steel-to-timber connections with 12 and 20 mm steel dowels were tested in a 4-point bending test set-up. The load, between the connected steel and wood beams, was transferred by the dowels themselves and also via an additional (passive) contact device, which introduced an eccentric normal force in the timber beam. The behavior of the connections was studied at the global scale of the connection and at the local scale of the individual dowels. A non-contact deformation measurement system was used to assess the changes of the location of the center of relative rotation over the entire loading. At the same time, the head deformations of the individual dowels could be measured, giving a direct indication about the force distribution among the dowels. Due to reinforcement, connections behaved distinctly ductile with a global relative rotation of up to 3°. Pre-stressing of the contact device by a force of 40 kN yielded an even stiffer behavior. For the particular configurations tested herein, the center of rotation was found to be close to the vertical axis of symmetry of the joint and close to the top row of the dowels. Moreover, the superimposed vertical shift of the center of relative rotation in case of a delayed normal force could be quantified. © 2015 RILEM

  • 6.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Serrano, Erik
    Lund University, Sweden.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dowel deformations in multi-dowel LVL-connections under moment loading2015In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, no 3, p. 216-231Article in journal (Refereed)
    Abstract [en]

    The aim of the experimental study presented herein is the assessment and quantification of the behavior of individual dowels in multi-dowel connections loaded by a bending moment. For this purpose, double-shear, steel-to-timber connections with nine steel dowels arranged in different patterns and with different dowel diameters were tested in four-point bending. In order to achieve a ductile behavior with up to 7° relative rotation, the connections were partly reinforced with self-tapping screws. The reinforcement did not influence the global load–deformation behavior, neither for dowel diameters of 12 mm nor for 20 mm, as long as cracking was not decisive. The deformation of the individual dowels was studied by means of a non-contact deformation measurement system. Thus, the crushing deformation, that is, the deformation at the steel plate, and the bending deformation of the dowels could be quantified. In the case of 12 mm dowels, the bending deformation was larger than the crushing deformation, while it was smaller in the case of 20 mm dowels. Moreover, dowels loaded parallel to the grain showed larger bending deformations than dowels loaded perpendicular to the grain. This indicates that the loading of the individual dowels in the connection differs depending on their location.

  • 7.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Serrano, Erik
    Lund University.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Integrative experimental characterization and engineering modeling of single-dowel connections in LVL2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 107, p. 235-246Article in journal (Refereed)
    Abstract [en]

    In order to be able to realistically and consistently elucidate and subsequently simulate the load displacement behavior of single-dowel connections, the material behavior of the individual components, namely steel dowels and wood, needs to be investigated. The behavior of slotted-in, single-dowel steel-to-laminated veneer lumber (LVL) connections with dowel diameters of 12 and 20 mm is thoroughly discussed here in relation to steel dowel and LVL properties. In addition to connection tests at different load-to-grain directions of 0, 45 and 90, the corresponding embedment behavior of LVL was tested up to dowel displacements of three times the dowel diameter. The material behavior of steel dowels was studied by means of tensile and 3-point bending tests and accompanying finite element simulations. A pronounced nonlinear behavior of the single-dowel connections was observed for all load-to-grain directions. In case of loading perpendicular to the grain, a significant hardening behavior was obvious. Due to the anisotropic material properties of wood, enforcing a loading direction of 45 to the grain resulted in an additional force perpendicular to the load direction which was quantified in a novel biaxial test setup. Thus, a comprehensive and consistent database over different scales of observations of dowel connections could be established, which subsequently was exploited by means of engineering modeling. The comparison of experimental and numerical data illustrates the potential of the engineering modeling approach to overcome drawbacks of current design regulations, which are unable to appropriately predict stiffness properties of dowel connections. Moreover, the quasi-elastic limit of dowel connections was calculated and discussed by means of the model. (c) 2016 Elsevier Ltd. All rights reserved.

  • 8.
    Bocko, Jozef
    et al.
    Technical University of Košice, Slovakia.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nohajová, Viera
    Technical University of Košice, Slovakia.
    Application of Evolutionary Algorithm in Elasticity2015In: Applied Mechanics and Materials, ISSN 1660-9336, E-ISSN 1662-7482, Vol. 816, p. 363-368Article in journal (Refereed)
    Abstract [en]

    This article introduces evolutionary algorithms and their utilization in mechanicalengineering. First part of this work describes evolutionary algorithms and their characteristics. Themain body of evolutionary algorithms, the selection methods for parents and the types ofreproduction are explained in the next part of this article. Termination conditions are also discussed.Finally, the application of evolutionary algorithms to a problem in mechanical engineering isdescribed. Thereby, the material parameters for a Bodner-Partom model describing viscoelastoplasticmaterial behavior are determined by fitting data from experiments on Aluminum testsamples under tension load.

  • 9.
    Dorn, Michael
    Vienna University of Technology.
    3D-Modeling of Dowel-Type Timber Connections2009Report (Other academic)
  • 10.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    A combined material model for plasticity and fracture for wood2015In: Proceedings of the EUROMECH Colloquium 556 on Theoretical, Numerical, and Experimental Analyses in Wood Mechanics / [ed] Michael Kaliske, 2015Conference paper (Refereed)
  • 11.
    Dorn, Michael
    Vienna University of Technology.
    Investigations on the Serviceability Limit State of Dowel-Type Timber Connections2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Dowel-type steel-to-timber connections are commonly used to transfer a large range of loads. Although they are simple to produce and assemble, the load-carrying behavior and the local stress and strain distribution within the connection area are highly complex. In addition to that, wood is a challenging material from an engineering point of view due to its highly anisotropic structure and behavior and due to its natural origin, which results often in inhomogeneities. The failure characteristics of wood are very different in tension and shear and in compression, where brittle failure and plastic-ductile failure modes occur, respectively. The aim of this thesis is to study the load-carrying behavior of dowel-type steel-to-timber connections in detail. This is achieved by performing experimental tests on single-dowel connections. A large variety of influencing parameters is assessed, which include wood density, connection width, the dowel roughness, and the application of reinforcements in order to prevent brittle behavior. Separate stages in the loading history are identified, starting from an initial consolidation phase, the region of maximum stiffness during load increase, and the point of maximum connection strength. Ductility is of great interest as well as the final failure modes. During the experiments, unloading and reloading cycles are performed, where distinctively higher stiffnesses are observed than during the first loading. The results of the experiments are compared to the design practice in Eurocode 5 for strength and stiffness estimation. Strength prediction is conservative except for slender connections, while stiffness prediction complied with experimental results only for connections of intermediate width. The initial consolidation phase of the experiments is then investigated further. It is concluded, that the properties of the bore-hole surface, where not a smooth but a rough surface with valleys and rifts is encountered, is responsible for the initially low stiffness. The contact behavior is studied by conducting experiments on wood with varying surface characteristics, which are a result of using different cutting tools. A mathematical model for the soft contact behavior is proposed, which is based on the results of the experimental tests. It also includes the evolution of non-reversible deformations in the surface layer. Complementing the experiments, a simulation tool suitable for numerically assessing the mechanical behavior of the connections is developed. It allows to perform simulations by means of the Finite Element method on such connections and provides an enhanced insight into the stress and strain distribution in connections compared to the tests. Hereby, a three-dimensional material model for wood is established, which allows to model the anisotropy of wood in the elastic as well as in the plastic domain, based on the theory of small strains and small displacements. The combination of the developed models for the material as well as the contact behavior leads to realistic simulation results, which are verified by comparing model predictions with the experimental results on connections. It is confirmed, that the computed behavior agrees well with the experimental one and that the features observed during the experiments are well reproduced. Due to the limitations of the simulation tool to small deformations, ultimate load and brittle failure modes cannot be predicted. Nevertheless, the influence of various parameters on both can still be estimated. The modeling approach is suitable for application to more complex situations in the future, such as multi-dowel connections or connection loaded by generalized loads. Especially the contact model, which is a unique feature in the thesis, allows a realistic simulation of the distribution of the forces in such statically indeterminant situations

  • 12.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Proposal for a Failure Surface for Orthotropic Composite Materials2014In: / [ed] Oñate, Eugenio and Oliver, Xavier and Huerta, Antonio, 2014Conference paper (Refereed)
  • 13.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Non-Linear Connection Models in Timber Engineering2016In: Proceedings of the 2016 World Conference on Timber Engineering (WCTE) / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Conference paper (Refereed)
    Abstract [en]

    In this contribution, a numerical model for connections in engineered timber structures, using specially designed connection elements, is presented. The model considers the non-linear load-displacement relation typical for many types of connections on different levels and is presented on the example of dowel-type connections. The structural levels investigated herein are a) the embedment behaviour of a dowel into wood; b) the behaviour of a singledowel connection; and c) a multi-dowel connection under a general load case typical for structural applications. A special characteristic considered in the formulation of the connector elements is the unloading behaviour, which is characterized by an initial high unloading stiffness but a very low stiffness when the load is fully removed. The latter is due to remaining permanent deformations in the wood as well as in the metal connector. The modelling approach was found to correlate well with experimental data and gave new insight in the behaviour of dowel connections, particularly as regards the unloading and reloading behaviour with alternating load directions on the single-dowel connection scale.

  • 14.
    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.

  • 15.
    Dorn, Michael
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    3D-Modeling of Dowel-Type Timber Connections2010Conference paper (Other academic)
    Abstract [en]

    Typical elements in structural engineering (beams, trusses, plates and shells) can be investigatedby means of quite simple material models employing a small number of material properties,especially as wooden structures are loaded within the elastic domain only and plasticity is nottaken into account. When investigating details, e.g. connections, three-dimensional stress andstrain distributions occur. At areas with local stress concentrations, elastic limit states maybe reached at low global load levels, but local plasticity need not endanger the stability of theentire structure.

    This study investigates dowel-type steel-to-timber connections. In particular, the behavior ofwood under high pressure loads and when yielding as well as the influences of contact and frictionbetween dowel and wood and of the nonlinearity of steel when yielding on the load carryingcapacity of the connection are analysed. The aim is to createa tool for reliable prediction ofthe strength and deformation characteristics of dowel-type timber connections.

    For this purpose, an elasto-plastic material model for woodwas developed and implemented intothe Finite Element programAbaqususing anUMAT-subroutine. A closed, single-surface Tsai-Wufailure criterion is used in combination with an associatedflow rule. The current model is ableto predict failure in wood (brittle and ductile behavior) locally as well as the different loadcarrying mechanisms (rigid dowel or plastic hinges in the dowel) on a global level. Additionally,a series of experiments is planned for validation.

  • 16.
    Dorn, Michael
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Experiments on the Load-Displacement Behavior of Dowel-Type Steel-To-Timber Connections2011In: 28th Danubia-Adria-Symposium on Advances in Experimental Mechanics: 28 September - 1 October, 2011, Hotel Magistern, Siófok, Hungary, Budapest: Scientific Society for Mechanical Engineering , 2011, p. 255-256Conference paper (Refereed)
    Abstract [en]

    Dowel-type steel-to-timber connections are typical connections in structural timber-engineering, which can be designed very easily for various loads and load combinations. For practical purpose the design is regulated in national and international codes [1]. Nevertheless, the design codes are not satisfying at the moment. Refined analyses by means of FE-simulations which are currently underway shall provide the basis for improved design rules.

    In order to validate the simulation tool a comprehensive test series (78 tests in total) was carried out. Additionally, detailed insight into the loading behavior of dowel-type connections could be gained as well as into the influence of various factors, e.g. density of wood, dowel length, friction between dowel and wood, load speed, un-/reloading cycles, additionally applied reinforcement, etc.

  • 17.
    Dorn, Michael
    et al.
    Vienna University of Technology.
    Hofstetter, Karin
    Vienna University of Technology.
    Eberhardsteiner, Josef
    Vienna University of Technology.
    Three-Dimensional Modeling of Dowel-Type Steel-to-Timber Connections2011In: Book of Abstracts of the 18th Inter-Institute Seminar, Budapest, 2011Conference paper (Other academic)
  • 18.
    Dorn, Michael
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Nohajová, Viera
    Technical University in Košice, Slovakia.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Investigating Various Influences on the Embedment Strength and Stiffenss of Wood2011In: 28th Danubia-Adria-Symposium on Advances in Experimental Mechanics: 28 September - 01 October, 2011, Siófok, Hungary / [ed] István Ódor, Lajos Borbás, Budapest: Scientific Society for Mechanical Engineering , 2011, p. 253-254Conference paper (Refereed)
    Abstract [en]

    Many structural problems originate from the insufficient performance of connections. The most common connection type used in timber structures is the dowel-type connection. Dowel-type connections are easy to manufacture and can be designed for a large load range.

    In the formula for determining strength according to EC5 [1], embedment strength of wood is the basic parameter. Embedment strength values are dependent on wood density and dowel diameter. The formula for embedment strength is derived from experiments.

    The purpose of this study is to specify the influence of various parameters on the embedment strength and stiffness of wood specimens under a steel dowel. Strength design in EC5 does not consider for e.g. increased roughness between dowel and wood, neither is the positive influence of reinforcement by e.g. screws covered

    Embedment tests are performed according to the European [2] and American standard [3] for embedment tests and the differences will be reported.

    Embedment tests in fiber direction are performed on wood specimens with different densities, in which moreover the holes were drilled with various drilling devices. Dowels with different roughness (roughened with rasps or engrailment) were inserted, some of the specimens were reinforced by screws to prevent cracking of the wood.

    These embedment tests are the continuation of tests on the contact stiffness of wood on steel and the dependence on wood roughness and density.

  • 19.
    Dorn, Michael
    et al.
    Vienna University of Technology, Austria.
    Karin, de Borst
    University of Glasgow, Scotland.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Numerical Simulations of the Loading Process of Dowel-Type Timber Connections2012In: CD-ROM Proceedings of the 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) / [ed] J. Eberhardsteiner, H. J. Böhm, F. G. Rammerstorfer, Vienna University of Technology , 2012Conference paper (Refereed)
    Abstract [en]

    In order to maximize utilization, numerical simulations are gaining importance in the design of timber structures. Dowel-type steel-to-timber connections are commonly used for a wide variety of loads. The current design generation, namely the Eurocode (EC)5 [1], is based on empirical tests, and lacks in many aspects a stringent mechanical foundation. The optimization of connections plays an important role for the competitiveness of timber structures, which is often restricted due to the inabilityof the design concepts to capture the large variety of fields of applications. The mechanical behavior of these types of connections is mainly driven by stiffness differences between the steel dowel and the wood part, whereby the strength properties of the materials and the geometric layout of the connection considerable affect the connection’s stiffness and strength.

  • 20.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Kozłowski, Marcin
    Silesian University of Technology, Poland.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Design approaches for timber-glass beams2014In: Glass, facade, energy : Engineered Transparency International Conference at glasstec: Conference on Glass, Glass Technology, Facade Engineering and Solar Energy, 21 and 22 October 2014 / [ed] Schneider, Jens and Weller, Bernhard, 2014Conference paper (Refereed)
    Abstract [en]

    This paper relates to the mechanical performance of timber-glass composite beams, which take exceptional advantage of the combination of the materials involved. Beam bending tests were performed with beams made from float glass and heat-strengthened glass. Three different adhesive types were used: silicone, acrylate and epoxy. The test results show that, with a proper design, the timber is able to transfer load after glass failure and hence collapse is delayed and a ductile behavior can be obtained. The results from the tests were compared with an analytical method using the gamma-method and the agreement between the analytical method and the tests are shown to be excellent.

  • 21.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Kozłowski, Marcin
    Silesian University of Technology, Poland.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Development of large-scale load-bearing timber-glass structural elements2014In: WCTE 2014 - World Conference on Timber Engineering: Proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    The building industry demands ever more effective structural elements with a multitude of requirements at the same time. There is increasing interest for load-bearing glass elements which can be deployed in timber structures, e.g. in the outer façade or as column or beam elements within the building. In an on-going research project, the materials glass, timber and the adhesive combining the former have to be selected to fit each other but also suit the application. The mechanical properties are studied individually as well as in combined small-scale specimens experimentally. Furthermore,large-scale tests on beams and shear walls are performed. This is accompanied by numerical analysis to study a wide range of dimensions and variations as well as specific design situations. The final output of the project will be prototypes to beused in showcase projects.

  • 22.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Tuvendal, Helena
    Södra skogsägarna.
    Henrik, Oxfall
    Swerea.
    Serrano, Erik
    Lunds Tekniska Högskola.
    FBBB 4.3 Biobaserade skivmaterial: Experimentella undersökningar2018Report (Other academic)
    Abstract [sv]

    Rapporten är del av projektet Framtidens Byggande och Boende (FBBB), delprojekt 4.3 "Biobaserade skivmaterial". I denna rapport presenteras resultatet av de mekaniska drag- och böjprov såsom DTMA analys. Materialet ”Durapulp”, som tillverkas av Södra, är referensmaterialet i delprojektet. Provkroppar av Durapulp producerades med olika tillverkningsmetoder för att se skillnader i beteenden. Referensmaterialen är trä-baserade skivmaterial som anses vanligt förekommande i byggskeendet.

  • 23. Eriksson, Jerry
    et al.
    Ludvigsson, Mikael
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Load bearing timber glass composites: A WoodWisdom-Netproject for innovative building system2013In: COST Action TU0905 Mid-term Conference on Structural Glass / [ed] Jan Belis; Christian Louter; Danijel Mocibob, Boca Raton, Fla: CRC Press, 2013Conference paper (Refereed)
    Abstract [en]

    The aim of this three year project, which is part of the WoodWisdom-Net researchprogram, is to develop an innovative load bearing building system composed of timberglasscomposites. The structural loads applied onto these composites will be transferred to, andsupported by, the glass component, in contrary to today’s traditional solutions where glass elementsonly function as an environmental shield. Using such structural elements will make itpossible to largely increase the glass surface in buildings, allowing the presence of more naturallight in personal homes and office buildings.

    Timber-glass shear walls and beams will be developed taking into consideration long-term behaviorand seismic performance. Design concepts, feasibility studies and performance assessmentsof these components will be performed in order to improve the overall performance. Theproject also includes the development of new design calculations as well as the optimization ofmanufacturing methods.

    Material properties of timber, glass and adhesives will be determined from small and large scaleexperimental investigations, and will be used as input for theoretical calculations and modelingwork. The projects industrial partners will function as expertise and take part in the developmentand construction of demonstration objects.

    The project consortium is composed of academic and industrial partners from Austria, Sweden,Germany, Turkey, Slovenia, Chile, and Brazil. This paper presents material specifications andresults from small scale testing performed by the Swedish project partners.

  • 24.
    Hofstetter, Karin
    et al.
    Vienna University of Technology.
    Bader, Thomas Karl
    Vienna University of Technology.
    Dorn, Michael
    Vienna University of Technology.
    The Benefit of Micromechanical Modeling in Timber Engineering2010In: Proceedings of the 11th World Conference on Timber Engineering, June 20-24, 2010, Riva del Garda, Italy, 2010Conference paper (Refereed)
    Abstract [en]

    Due to its highly optimized structure across several length scales, wood exhibits a very complex mechanical behavior at the macroscale and a high variability of its material properties. Both constitute major obstacles to a broader application of this material for engineering purposes. The combination of multiscale modeling and powerful material models implemented in numerical simulation software such as the finite element method is considered as efficient strategy to overcome these limitations and to improve reliability and capabilities of current timber engineering design. Examples of such models and their application to numerical analysis of a dowel joint are shown in this paper.

  • 25.
    Horvatits, Johan
    et al.
    Vienna University of Technology.
    Gaubinger, Bernhard
    Vienna University of Technology.
    Dorn, Michael
    Vienna University of Technology.
    Cserno, Tamas
    Vienna University of Technology.
    Kollegger, Johann
    Entwicklung einer Vergussverankerung für Zugglieder aus Faserverbundwerkstoff2004In: Bauingenieur: Zeitschrift für das gesamte Bauwesen, ISSN 0005-6650, E-ISSN 1436-4867, Vol. 79, p. 101-110Article in journal (Refereed)
    Abstract [en]

    In general prestressed concrete structures are very durable and reliable. The durabilty of such structures can yet be sensitively affected by the influence of corrosion under certain circumstances. Corrosion may also lead to significant problems concerning the medium as well as long-term load carrying behaviour especially for stay cables, external post-tensioning systems or old structures with insufficient execution of prestressing works. The upcoming damages on prestressed steel tendons given by the corrosion problem and the resulting cost-intensive rehabilitation and maintainance measures introduced the application of alternative construction materials, such as fiber composites (fiber reinforced plastics – FRP) in civil engineering. Carbon fiber reinforced plastics (CFRP) offer a reliable alternative to conventional steel tendons due to their excellent mechanical and strength properties in fiber direction and high potential as tension elements in prestressed concrete structures or bridge constructions (stay cables). However the physical properties in transversal direction are very poor and characterized by a high sensitivity against lateral pressure. In order to exploit the high material capacities of CFRP, the key problem of an economic and efficient application in prestressed systems is to find a suitable anchorage system which prevents a premature failure of the CFRP tendon subjected to high lateral stresses and which further enables a uniform stress distribution inside the anchoring body.

  • 26.
    Karlsson, Viktor
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Wärnelöv, Morgan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Östman, Birgit
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Brandpåverkan på lastbärande trä-glasväggar2017In: Bygg & teknik, ISSN 0281-658X, Vol. 109, no 6, p. 44-47Article in journal (Other academic)
    Abstract [sv]

    Glas har flera av de egenskaper som eftersöks hos ett bärande material: hög styvhet, hög hållfasthet - och är dessutom transparant! Tillsammans med rätt lim och en träram bildas väggar som klarar stora laster. Linnéuniversitetet i Växjö har forskat inom detta ämne och gjort många tester på glasväggar. Resultaten visar att en bärande glasvägg kan ha lastkapacitet för att klara en bostadslast för 3-4 våningar. Nu har möjligheterna att även klara brandkraven undersökts i ett examensarbete.

  • 27.
    Kozłowski, Marcin
    et al.
    Silesian University of Technology, Poland.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Lund University, Sweden.
    Experimental testing of load-bearing timber–glass composite shear walls and beams2015In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, no 3, p. 276-286Article in journal (Refereed)
    Abstract [en]

    The paper presents results from the experimental testing of load-bearing timber–glass composite shear walls and beams. Shear wall specimens measuring 1200 × 2400 mm2 manufactured with three adhesives of varying stiffness were tested. Twelve specimens with a single 10 mm thick glass pane and one specimen with an additional insulating glass unit were produced. The testing procedures involved various loading conditions: pure vertical load and different combinations of shear and vertical loading. The test results showed that the adhesive had only a minor influence on the buckling load which was the main failure mechanism. 240 mm high and 4800 mm long timber–glass beams manufactured with adhesives of different stiffness were tested. For the webs, two types of glass were used: annealed float and heat-strengthened glass, in both cases 8 mm thick panes were used. In total, 12 beams were tested in four-point bending until failure. Despite the considerable difference in adhesive stiffness, beam bending stiffness was similar. Concerning load-bearing capacity, the beams with heat-strengthened glass were approximately 50% stronger than the beams made using annealed float glass.

  • 28.
    Kroon, Martin
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Andreasson, E.
    Tetra Pak, Sweden;Blekinge Institute of Technology, Sweden.
    Persson Jutemar, E.
    Tetra Pak, Sweden.
    Petersson, V.
    Tetra Pak, Sweden.
    Persson, L.
    Tetra Pak, Sweden.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, P.A.T.
    Malmö University, Sweden.
    Anisotropic elastic-viscoplastic properties of at finite strains of of injection-moulded low-density polyethylene2018In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 58, no 1, p. 75-86Article in journal (Refereed)
    Abstract [en]

    Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters.

  • 29.
    Lederer, Wolfgang
    et al.
    Vienna University of Technology.
    Bader, Thomas K.
    Vienna University of Technology.
    Dorn, Michael
    Vienna University of Technology.
    Muszynski, Lech
    Development of Integrated Imaging Methods for Investigation of Micromechanics of Dowel Connections for Engineered Wood Components2012In: CD-ROM Proceedings of the 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) / [ed] J. Eberhardsteiner, H. J. Böhm, F. G. Rammerstorfer, 2012Conference paper (Refereed)
  • 30.
    Murin, Justin
    et al.
    Slovak Univ Technol Bratislava, Slovakia.
    Aminbaghai, Mehdi
    Vienna Univ Technol, Austria.
    Hrabovsky, Juraj
    Slovak Univ Technol Bratislava, Slovakia.
    Balduzzi, Giuseppe
    Vienna Univ Technol, Austria.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Mang, Herbert A.
    Vienna Univ Technol, Austria;Tongji Univ, Peoples Republic of China.
    Torsional warping eigenmodes of FGM beams with longitudinally varying material properties2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 175, p. 912-925Article in journal (Refereed)
    Abstract [en]

    In this paper, the influence of torsional warping of thin-walled cross-sections of twisted Functionally Graded Material (FGM) beams with a longitudinal polynomial variation of the material properties on their eigenvibrations is investigated, considering the secondary deformations due to the angle of twist. The transfer relations needed for the transfer matrix method are derived. Based on them, the local finite element equations of the twisted FGM beam are established. The warping part of the first derivative of the twist angle, caused by the bimoment, is considered as an additional degree of freedom at the beam nodes. The focus of the numerical investigation, with and without consideration of the Deformation due to the Secondary Torsional Moment (STMDE), is on modal analysis of straight cantilever FGM beams with doubly symmetric open and closed cross sections. The influence of the longitudinal variation of the material properties and the secondary torsion moment on the eigenfrequencies is investigated. The obtained results are compared with the ones calculated by a very fine mesh of standard solid and warping beam finite elements.

  • 31.
    Nicklisch, Felix
    et al.
    Technische Universität Dresden, Germany.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Weller, Bernhard
    Technische Universität Dresden, Germany.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Joint study on material properties of adhesives to be used in load-bearing timber-glass composite elements2014In: Glass | Facade | Energy / [ed] Jens Schneider, Bernhard Weller, Technische Uni Dresden , 2014, p. 271-280Conference paper (Refereed)
    Abstract [en]

    Beyond its transparency, glass offers a large potential to fulfill load-bearing functions. Timber-glass composite elements take advantage of the high stiffness and strength of glass. At the same time the post-breakage behavior of the composite element increases significantly compared to the brittle failure of a pure glass. The current study relates to timber-glass composites where the composite action is obtained via a linear bondline connecting the glass pane to a timber frame. The full potential of these composite elements arises from the use of adhesives of medium and high stiffness which exhibit rather small deformations compared to e.g. structural silicones. A central objective of the research is the assessment and the optimization of the bondline properties with respect to stiffness of the adhesive. The paper summarizes the results of an in-depth study on commercially available adhesives and evaluates their general suitability in timber-glass composites.

    The material properties of the adhesives were determined by thorough mechanical testing of the bulk material in the first place under varying conditions, typically encountered in façades. The potential use in glass-timber composites was then evaluated using small bonded specimens comprising birch plywood or massive pine wood in combination with soda-lime glass. Failure modes were categorized in order to ascertain the influence of the timber strength on the load-bearing capacity.

    In order to guarantee reliable results from various sources, parts of the tests were executed repeatedly at different laboratories. Results were compared and validated throughout the project. Hence the results of this study provide a reliable basis for material models used in e.g. numerical analysis and engineered design solutions. The study presented here is part of the WoodWisdomNet project “LBTGC - Load Bearing Timber Glass Composites”

  • 32.
    Schweigler, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bolmsvik, Åsa
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Static and dynamic properties of connections in timber-frame structures: BOOST + FBBB project2018Report (Other academic)
    Abstract [en]

    Connections play an important role in timber frame structures, especially when approaching the market of multi-story buildings. Two questions faced by practitioners were studied: for the first is the deformation behavior of such structures, where connections between wall and floor elements play an important role for the global stability of the timber structure. For the second is the sound transmission within elements of high importance, particularly timber building systems face challenges. For that reason, the static and dynamic behavior of such connections was studied in a joined experimental program. Two different building systems were investigated in 13 different test setups of how a floor and wall elements were connected to each other. By adjusting connection elements, the influence of various parameters on the dynamic and static behavior was studied. Sound/vibration transmission over the wall-floor connection was the special interest of the dynamic study. The floor element was excited by a shaker, and the response of floor and wall element was measured by accelerometers. This allowed to identify eigenfrequencies and eigenmodes as well as the damping of the structure and the insertion loss over the connection, respectively. Distinct differences between the building systems of the different producers were seen, while adjustments within building systems influenced only slightly the dynamic behavior. For the static part of the study, the moment-rotation behavior of the wall-floor connection was investigated. Variations of connection designs and layouts were tested to better understand the load-transfer and the mechanical interaction using different connectors and connector arrangements. The nailed connection between vertical studs and the bottom rail of the wall element was identified as a soft point when loaded by a horizontal force perpendicular to the plane of the wall element. Using screws this connection showed a substantial improvement of the connection strength. Further adjustments on the connector arrangements showed only partly influence on connection stiffness and strength.

  • 33.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Load-bearing timber-glass shear walls2014In: Glass | Facade | Energy / [ed] Schneider, Jens and Weller, Bernhard, Technische Uni Dresden , 2014, p. 311-318Conference paper (Refereed)
    Abstract [en]

    Timber-glass composite shear wall elements were manufactured with different adhesives. The elements were 1200×2400 mm in size. 12 single pane elements and one element with an insulation glass unit (IGU) were manufactured. The load bearing glass pane was in all cases made from 10 mm float glass. The elements were tested in various loading conditions, involving pure vertical load and different combinations of in-plane shear and vertical loading. The test results show that the influence of the adhesive chosen on the ultimate (buckling) load is only of minor importance. This was also confirmed by finite element analyses.

  • 34.
    Trischler, Johann
    et al.
    Luleå University of Technology.
    Sandberg, Dick
    Luleå University of Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Effect of temperature during vital gluten adhesive preparation and application on shear-bond strength2018In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 32, no 4, p. 448-455Article in journal (Refereed)
    Abstract [en]

    If protein-based adhesives are to become a competitive bio-based alternative to synthetic adhesives, the preparation and application methods have to be considerable improved to reduce process time and thereby improve the economy of the adhesive system. The purpose of this study was to investigate the impact of the temperature during preparation and application on the shear-bond strength of an adhesive based on vital gluten for use in wood applications. Vital gluten was used in its natural form and mixed with water of different temperatures (preparation temperature 0 °C or 20 °C), and applied on beech veneer at different temperature (application temperature –10, 20, 60 and 100 °C). Tensile shear-bond strength samples were prepared and tested according to EN 205. The results showed that an increase in veneer temperature during application of the adhesive led to a decrease in the shear-bond strength, but that the preparation temperature of the adhesive had no influence on the strength.

  • 35.
    Trischler, Johann
    et al.
    Luleå University of Technology, Sweden.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Luleå University of Technology, Sweden.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vital gluten for particleboard production: effect of wood-particle moisture on board properties2018In: Forest products journal, ISSN 0015-7473, Vol. 68, no 2, p. 127-131Article in journal (Refereed)
    Abstract [en]

    The growing environmental awareness is leading to an increased interest in the use of bio-based adhesives and proteins such as vital gluten. The purpose of this study was to investigate the influence of the wood-particle moisture content, water application and press time on the internal bond strength, thickness expansion and thickness swelling of particleboards glued with vital gluten. Green and dried wood particles with similar moisture contents were achieved through drying or water addition and were blended with vital gluten powder and pressed for 1 to 3 minutes. The results show that not only the pressing time and moisture content, but also the way of achieving the moisture content has a strong impact on the performance of the boards. At comparable moisture content, never-dried (green) particles with high moisture content in combination with a dry adhesive application produced boards which performed better than boards made of dry particles with water addition to simulate liquid adhesive application.

1 - 35 of 35
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