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  • 1.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Bocquet, Jean-Francois
    ENSTIB/LERMAB, University of Lorraine, France.
    Schweigler, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Lemaitre, Romain
    ENSTIB/LERMAB, University of Lorraine, France.
    Numerical modeling of the load distribution in multiple fastener connections2018Inngår i: Design of Connections in Timber Structures: A state-of-the-art report by COST Action FP1402/WG3 / [ed] Carmen Sandhaas, Jorgen Munch-Andersen, Philipp Dietsch, Aachen: Shaker Verlag, 2018, s. 221-239Kapittel i bok, del av antologi (Fagfellevurdert)
  • 2.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Bocquet, Jean-Francois
    University of Lorraine, France.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Lemaitre, Romain
    University of Lorraine, France.
    Numerical modeling of the load distribution in multiple fastener joints2017Inngår i: International Conference on Connections in Timber Engineering – From Research to Standards: Proceedings of the Conference of COST Action FP1402 at Graz University of Technology / [ed] Reinhard Brandner, Andreas Ringhofer & Philipp Dietsch, Graz: Verlag der Technischen Universität Graz , 2017, s. 136-152Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Numerical modeling approaches, for the determination of load distribution in laterally loaded joints, as well as for the assignment of stiffness properties of joints for the structural analysis, are summarized in this contribution. The effect of the nonlinearity and the load-to-grain orientation dependence of connection slip, of elastic deformation in the surrounding wood matrix, and of the deviation between load and displacement direction are discussed. Comparison of various models demonstrates the pronounced effect of the load-to-grain orientation dependence and the nonlinearity in connection slip on the load distribution, particularly in case of moment loading. The effect of elastic deformation in the wood matrix on the load distribution increases with increased size of joints, even more pronounced when joints are loaded by a shear force perpendicular to the grain. In case of normal force loading, the non-uniform load distribution due to elastic deformation in the wood matrix reduces rapidly with increased relative joint displacement. Pros and cons of the modeling approaches as well as necessary input data are discussed in relation to the design process and European standardization.

  • 3.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Schweigler, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Numerical modelling of the rope effect in laterally loaded dowel-type connections2018Inngår i: 6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7), 11 – 15 June 2018, Glasgow, UK, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Theory of laterally loaded dowel-type fasteners is well understood in relation to their bending deformation as a consequence of lateral embedment stresses in wood. Modelling of the so- called rope effect has however attracted less attention. The rope effect in laterally loaded connections is evoked by withdrawal resistance of the shank as well as by axial resistance of the head of the fasteners. It describes the development of tensile forces along the axis of the fastener, as a consequence of its bending deformation and axial constrains. Hilson [1] emphasized the pronounced contribution of frictional forces in the shear planes that contribute to increased strength of laterally loaded connections. The axial force component parallel to the shear plane however will only become significant for large relative displacements. Different kind of numerical models have been proposed for the simulation of dowel-type connections, including 3D FEM with elasto-plastic material models, with damage mechanics, or so-called foundation models. In this contribution, calculations with a beam-on-nonlinear foundation method [2] will be presented. The model was extended to account for increased lateral connection strength due to withdrawal resistance of fasteners. This was implemented in terms of axial springs that encompass a withdrawal force-relative displacement relationship, similar to the lateral springs that hold information on the embedment behaviour. Friction between the connected timber members was taken into account by the frictional coefficient times the force component perpendicular to the shear plane, which is a result of the axial force in the fastener.

    Calculations were performed for different types of dowel-type fasteners, including screws, smooth shank nails, annular-ringed shank nails and smooth dowels. Model predictions were compared to experimental data and showed good agreement. This encourages the use of the beam model for the engineering design of dowel-type connections in timber structures based on a deeper understanding of structure-connection relationships [3].

  • 4.
    Bader, Thomas K.
    et al.
    Technische Universität Wien, Austria.
    Schweigler, Michael
    Technische Universität Wien, Austria.
    Hochreiner, Georg
    Technische Universität Wien, Austria.
    Eberhardsteiner, Josef
    Technische Universität Wien, Austria.
    Berechnungsmodell für das Last-Verformungsverhalten von Stabdübelgruppen im Ingenieurholzbau2014Inngår i: Berichte der Fachtagung Baustatik-Baupraxis 12, München: Technischen Universität, München , 2014, s. 113-121Konferansepaper (Annet vitenskapelig)
    Abstract [de]

    In diesem Beitrag wird ein Berechnungsmodell für das Last-Verformungsverhalten von Stabdübelgruppen vorgestellt, mit dem lokale Verbindungsmittelkräfte und Verbindungsmitteldeformationen mit zugehörigen globale Schnittgrößen und Relativverformungen konsistent berechnet werden können. Grundlage dafür bildet das Last-Verformungsverhalten des Einzeldübels, das mit Hilfe eines baustatischen Modellierungsansatzes hergeleitet wird. Ein wesentlicher Eingangsparameter dieses Modells ist die Lochleibungsfestigkeit von Holz, die für beliebige Kraft-Faserrichtungen experimentell untersucht wurde. Mit Hilfe des vorgestellten Berechnungsmodells für Stabdübelgruppen können die Tragfähigkeit einer Verbindung unter einer beliebigen Kombination von Normalkraft, Querkraft und Momentenbeanspruchung und die zugehörige Relativverformung berechnet werden. Mit dem vorgestellten Berechnungsmodell kann der lastfallabhängige Einfluss einer Verbindung auf Schnittgrößen-Verformungsinteraktionen direkt in der baustatischen Berechnung von Holzkonstruktionen berücksichtigt werden.

  • 5.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Schweigler, Michael
    Technische Universität Wien, Austria.
    Hochreiner, Georg
    Technische Universität Wien, Austria.
    Eberhardsteiner, Josef
    Technische Universität Wien, Austria.
    Ingenieurmodelle für die Strukturmodellierung und Nachweisführung von stiftförmigen Verbindungen im Holzbau: (Engineering models for the structural design and verification of dowel-type connections in timber structures)2017Inngår i: Österreichische Ingenieur- und Architekten-Zeitschrift, ISSN 0721-9415, Vol. 162, nr 1-12, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Connections of elements in timber structures play an important role, not only due to their pronounced effect on the mechanical behavior of structures, but also due to the fact they can be decisive for the economic success of timber structures. Herein, approaches for a calculation of the ductile load-displacement behavior of dowel-type connections, of multi-dowel joints and of stresses in their timber matrix, by means of numerical methods, are presented. With these methods, kinematically compatible relative deformations of joints under arbitrary plane loading conditions and their effect on the mechanical behavior of timber structures can be reasonably predicted. The combination of the presented models and their integration in the structural analysis and the verification of timber structures lead to a more realistic prediction of their behavior (internal forces, stresses and deformations), as well as to a more economic design of timber structures. 

  • 6.
    Bader, Thomas K.
    et al.
    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.
    Load Distribution in Multi-Dowel Timber Connections under Moment Loading: Integrative Evaluation of Multiscale Experiments2016Inngår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE) / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna University of Technology, Austria , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The load distribution in multi-dowel timber connections under bending moments was investigated by means of an integrative evaluation of a hierarchically organized test program, which encompassed component tests as well as single dowel and multi-dowel connection tests. It was demonstrated that the anisotropic material behaviour of LVL, and consequently of wood in general, leads to a non-uniform distribution among the dowels.

  • 7.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). 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.
    Dorn, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Experimental Assessment of the Load Distribution in Multi-Dowel Timber Connections2016Inngår i: 17th International Conference on Experimental Mechanics, Rhodes, Greece, July 3-7, 2016, 2016Konferansepaper (Annet vitenskapelig)
    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.

  • 8.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria .
    Hochreiner, Georg
    Vienna University of Technology, Austria .
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Dorn, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Serrano, Erik
    Lund University.
    Experimental characterization of the global and local behavior of multi-dowel LVL-connections under complex loading2016Inngår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, nr 6, s. 2407-2424Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 9.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). 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
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Dorn, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Dowel deformations in multi-dowel LVL-connections under moment loading2015Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 3, s. 216-231Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    Bader, Thomas K.
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Serrano, Erik
    Lund University.
    Dorn, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Integrative experimental characterization and engineering modeling of single-dowel connections in LVL2016Inngår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 107, s. 235-246Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Hochreiner, Georg
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    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 matrix2017Inngår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 131, s. 421-437Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 12. Hochreiner, Georg
    et al.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Schweigler, Michael
    Esser, Gerold
    Hagmann, Stefan
    Glatz, Bernhard
    The Historic Roof Structure of the Spanish Riding School in Vienna: Structural Assessment2015Inngår i: Proceedings of the International Conference on Structural Health Assessment of Timber Structures, SHATIS15, Dolnoslaskie Wydawnictwo Edukacyjne (DWE) , 2015, s. 248-259Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In 2012, the historical roof structure of the Spanish Riding School, built in the years from 1729 to 1735 as part of the ensemble of the Vienna Imperial Palace (called Hofburg), was documented by students and staff of the Vienna University of Technology. The survey was performed deformation- accurate and included both, the main structure and corresponding joints. Consequently, the documentation highlights deviations from the initial perception of the roof structure such as broken joints, inactivity of compressive devices like knee braces or excessive displacements of single structural members. Probably, these damages led to strengthening measures (=additional substructures) that were added in recent times to avoid progressive failure. This documentation formed the basis for the assessment of this historical roof structure from a structural and timber engineering point of view, which will be presented herein. The focus of the structural modelling was placed on the assessment of the two initial structural concepts, namely the main hall with and without the timber dome structure that was added in 1734, by visualisation of the internal forces and displacements. For this purpose, the nonlinear load carrying capacities and failure modes of the carpentry joints were assessed. Subsequently, alternative structural systems could be found by iterative recalculation revealing the capabilities for redundancy of the timber roof structure. Corresponding results were checked again with in-situ observations. Consequently, the findings of this study highlight the benefits of integrating modern structural and timber engineering methods and tools in the context of building history and building survey.

  • 13.
    Hochreiner, Georg
    et al.
    Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Riedl, Christian
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Matrix Failure of Multi-Dowel Type Connections Engineering Modelling and Parameter Study2016Inngår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE), Vienna University of Technology, Austria , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A simplified numerical engineering model for the design of the surrounding timber matrix of dowel groups, developed within the framework of a commercial structural analysis software, is presented herein. This model was applied to highlight and reflect various dowel arrangements in timber to steel connections from building practice subjected to arbitrary sets of internal forces against the background of both the real mechanical behavior and the present practice of design. A parameter study revealed the interdependence of stresses in the timber matrix and geometrical and mechanical properties of dowel groups.

  • 14.
    Lemaitre, Romain
    et al.
    ENSTIB/LERMAB, University of Lorraine, France.
    Bocquet, Jean-Francois
    ENSTIB/LERMAB, University of Lorraine, France.
    Schweigler, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Beam-on-foundation modelling as an alternative design method for single fastener connections2018Inngår i: Design of Connections in Timber Structures: A state-of-the-art report by COST Action FP1402/WG3 / [ed] Carmen Sandhaas, Jorgen Munch-Andersen, Philipp Dietsch, Aachen: Shaker Verlag, 2018, s. 207-220Kapittel i bok, del av antologi (Fagfellevurdert)
  • 15.
    Lemaitre, Romain
    et al.
    ENSTIB/LERMAB, University of Lorraine, France.
    Bocquet, Jean-Francois
    ENSTIB/LERMAB, University of Lorraine, France.
    Schweigler, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Beam-on-foundation modelling as an alternative design method for timber joints with dowel-type fasteners: Part 1: Strength and stiffness per shear plane of single-fastener joints.2018Inngår i: 5th INTER Proceedings, 2018: International Network on Timber Engineering Research 2018, Karlsruher Institut für Technologie , 2018, artikkel-id 51-7-13Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Optimised manufacturing processes made possible the production of larger dimensions timber products, which allow for the design of remarkable structures. In the last version of the EN 1995-1-1, it seemed important to its drafters to propose design formulas to estimate stiffness of joints in accordance with the needs of that time. Aware of the technical jump that had to be managed, the proposed rules remained simple. However, simple design equations became insufficient to cope with present-day challenges, which are, e.g., related to the design of high-rise wooden buildings. In EN 1995-1-1, the resistant capacity of dowel-type timber joints is no longer determined by empirical formulas but it is based on the limit analysis proposed by Johansen (1949). This methodology however shows limits for complex joints even though many improvements have been made since its introduction (Blaß and Laskewitz 2000). In parallel with these analytical approaches, developments in computational mechanics made it possible to develop simple numerical methods (Foschi 1974, Hirai 1983), which taken even into account nonlinear phenomena. These approaches have remained unused in practical design due to their complex implementation and their high running time, at the time of their invention, while todays computational resources strongly reduced corresponding limitations. Thus, numerical modelling of connections can help engineers to fill the gaps of the EN 1995-1-1 and to cope with variability in connection design. For this purpose, dowel-type fasteners are numerically modelled as elastoplastic beams on a nonlinear foundation in engineered in wood-based products (Sawata and Yasumura 2003, Hochreiner et al. 2013). This method is called Beam-On-Foundation (BOF) modelling and shows huge potential for engineering design. The purpose of this paper is to show how this method can substitute and complement limit analysis and empirical stiffness formulas of timber joints with dowel-type fasteners.

  • 16.
    Schweigler, Michael
    Vienna University of Technology.
    A numerical model for slip curves of dowel connections and its application to timber structures2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Wood as a natural and renewable material currently experiences a revival as structural building material. New technologies and a new design standard request appropriate, modern design methods for timber structures. Particularly, the design of modern timber connections is of importance since more challenging timber constructions demand ambitious connections. Most connections in timber structures are compliant in the sense that relative deformations between the connected structural elements occur during load transfer. In particular dowel connections exhibit this behavior since load transfer in dowel connections is based on the compliant embedment behavior of stiff steel dowels in wood.

    The aim of this thesis is to develop a model for a consistent calculation of the load-deformation relationship of connections. Additionally, this model is applied to timber structures to study the influence of compliant connections on the structural behavior. As a basis for the modeling of dowel connections, properties of single-dowel connections are presented. Different responses of wood in case of different loading directions, as well as several models for the calculation of single-dowel slip curves are discussed. Significant differences in the predicted load-deformation behavior of single-dowels can be observed among these approaches. A sub-model is used to determine realistic single-dowel slip curves for arbitrary connection configurations. Furthermore, the state-of-the-art approach for the determination of connection slip curves of multi-dowel connections is discussed. The restriction of this approach to some specific design situations is highlighted. These limitations of the current design approach are the motivation to develop a model for the calculation of slip curves of multi-dowel connections. This model enables a straight forward determination of member forces and connection slip curves for an arbitrary set of deformations. The single calculation steps and the feasibility of application on arbitrary connection configurations are discussed. Furthermore, a modification of the model to determine the deformation and force distribution within the connection for specific member forces is presented.

    Finally, the model is applied to different connections to illustrate their behavior for simple design examples. Moreover, connection slip curves have been implemented in the structural analysis of a static indetermined system in order to illustrate the necessity of considering the compliance of connections in the design of timber structures. It is shown that negligence of the connection slip may lead to uneconomic or even unsafe timber structures. Furthermore, the importance of an exact definition of the connection slip curves is discussed. Even insignificant differences from standard configurations may lead to remarkable changes in the connection behavior and, consequently, in the behavior of the structure. Moreover, a considerable influence of the used method to describe the single-dowel behavior on the behavior of the connection and, consequently, on the structural behavior has been found.

  • 17.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Experimental characterization and parameterization of the load-to-grain angle dependent embedment behavior of dowel-type fasteners in laminated veneer lumber (LVL)2016Rapport (Annet vitenskapelig)
  • 18.
    Schweigler, Michael
    Vienna University of Technology.
    Nonlinear modeling of reinforced dowel joints in timber structures: a combined experimental-numerical study2018Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Steel dowels are indispensable elements for the design of joints in modern timber structures. Dowels are broadly used because of their flexibility in design and easy assembling on-site, as well as due to their advantageous mechanical behavior. Recent developments in reinforcement techniques allow for designing ductile dowel joints, which exhibit nonlinear slip behavior. However, currently applied limit state approaches for calculation of connection strength are not able to fully exploit the potential of dowel joints. This calls for development of more advanced calculation methods, which was aimed for in this thesis.

    For thorough understanding of the complex mechanical behavior of dowel connections, application of a so-called multiscale approach is advantageous. Thereby, nonlinear loaddeformation behavior of dowel connections is studied on different length scales, from the scale of connection components, up to the joint level. The aim of this thesis was to exploit knowledge from lower scales in models that finally allow for nonlinear analysis of timber structures. In the work at hand, this was achieved by a combined experimental-numerical analysis.

    Experimental studies on the nonlinear embedment slip of ductile dowel connections, and its relation to the orthotropic material behavior of wood, was one of the objectives of this work. Breaking new ground by testing up to large dowel displacements, at various angles to the grain, for unconstrained and constrained lateral displacement conditions, required development of new testing procedures and test setups. Test results gave access to nonlinear embedment slip curves and showed their dependence on loading direction and lateral displacement conditions.

    In the next step, embedment slip data were exploited in modeling of single-dowel connections. Beam-on-nonlinear foundation modeling was applied for this purpose. Validation of connection tests and a parameter study not only highlighted suitability of the calculation method, but allowed for gaining insight into limit states. Thus, beam-on-foundation modeling was found to be an attractive alternative to advanced 3D FEM models for engineering design.

    Parameterized equations for regression analysis of nonlinear slip curves, and interaction curves describing the grain angle dependence of mechanical parameters, were summarized in a literature review. With these equations at hand, a multi-dimensional parameterization method for the nonlinear slip as a function of the load-to-grain angle was developed. This method was applied to experimental data derived in embedment and single-dowel connection tests as well as in simulations. Analytical equations for connection slip are expected to facilitate engineering modeling at the single-dowel connection and joint level, respectively.

    Joint modeling aimed at establishing a calculation method suitable for engineering design with an attractive trade-off between modeling effort, calculation time and accuracy. This was tackled by a semi-analytical model based on nonlinear elastic springs for the dowel slip and rigid connection members. Thereby, global joint slip, and thus stiffness and strength of joints, as well as local load distribution within joints can be predicted. This model proved to be suitable for single-dowel-based and joint-based design concepts. Calculation examples showed pronounced influence of loading direction dependence and nonlinearity of dowel slip on local load distribution, as well as on global joint slip. Influence of interaction between internal forces on the joint stiffness became obvious from structural analysis with nonlinear joint slip.

    This work covers a combined experimental-numerical analysis of the slip behavior of ductile dowel joints, from the wood embedment and steel dowel bending behavior, the single-dowel slip, to the joint behavior, with final application in nonlinear structural analysis. Presented models predicted nonlinear slip with suitable accuracy and efficiency. Application of nonlinear joint slip in structural analysis showed the potential of ductile dowel joints, which could be exploited in engineering design by the herein presented multiscale modeling strategy.

  • 19.
    Schweigler, Michael
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Predicting strength of dowel-type timber connections with rope effect2018Inngår i: Engineering Mechanics Institute Conference (EMI 2018) May 29 - June 1, 2018, Cambridge, Massachusetts, USA, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The behavior of laterally loaded dowel-type fasteners is well established in relation to their bending deformation caused by lateral embedment stresses in wood. Modeling of the so-called “rope effect” has however attracted less attention. The rope effect in laterally loaded connections is evoked by withdrawal behavior of the shank as well as by axial resistance of the head of the fasteners. It describes the development of tensile forces along the axis of the fastener, as a consequence of its bending deformation and axial constrains. These tensile forces cause frictional forces in the shear planes of the connection, which considerably increase the strength of laterally loaded connections.

    Different kind of numerical models have been proposed for the simulation of dowel-type connections, including 3D FEM with elasto-plastic material models, with damage mechanics or with so-called foundation models. In this contribution, calculations with beam-on-nonlinear foundation method will be presented. Compared to conventional foundation models, elements to account for increased lateral connection strength due to withdrawal strength and rope effect of the fasteners were added. This was implemented in terms of axial springs that encompass a withdrawal force-relative displacement relationship, similar to the lateral springs considering the embedment behavior. In addition, friction between the connected timber members was taken into account by the frictional coefficient times the force component perpendicular to the shear plane, as a result of the axial force in the fastener. 

    Calculations were performed for different types of dowel-type fasteners, including screws, nails with a smooth shank, nails with an annular-ringed shank and smooth dowels. Model predictions were compared to experimental data and showed good correlation. This encourages the use of the beam model for the engineering design of dowel-type connections in timber structures based on a deeper understanding of structure-connection relationships.

  • 20.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Load Direction Dependency of the Embedment Behaviour of Dowel-Type Fasteners in Laminated Veneer Lumber2014Inngår i: 16th International Conference on Experimental Mechanics (ICEM16), July 7-11, 2014, University of Cambridge, UK, Cambridge, UK, 2014Konferansepaper (Annet vitenskapelig)
  • 21. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Eberhardsteiner, Josef
    The influence of displacement boundary conditions on the embedment behavior of dowel-type fasteners2016Inngår i: Presented at 33nd Danubia-Adria Symposium on Advances in Experimental Mechanics, Portorož, Slovenia, 2016, 2016Konferansepaper (Annet vitenskapelig)
  • 22.
    Schweigler, Michael
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Engineering modeling of semi-rigid joints with dowel-type fasteners for nonlinear analysis of timber structures2018Inngår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 171, s. 123-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plastic analysis in engineered structures requires ductility of structural components, which in timber structures is primarily provided by joints made of dowel-type fasteners. A prerequisite for nonlinear analysis is realistic modeling of joint stiffness and load distribution in dowel-type joints. A joint model suitable for structural analysis is presented and validated in this contribution. The semi-analytical joint model is based on kinematic compatibility and equilibrium considerations. It accounts for local fastener slip by means of nonlinear elastic springs. Influences of nonlinearity and orientation dependence of fastener slip are assessed. Elastic deformations of the timber in between dowels are however neglected. The model allows for predicting global joint stiffness, as well as load distribution within the joint, taking explicitly the effect of simultaneously acting internal forces into account. Model validation builds upon an experimental database that spans from embedment testing on the material scale up to joint testing on the structural scale. Application examples demonstrate the broad applic- ability of the model for structural analysis. Moreover, they illustrate effects of assumptions of fastener slip on the joint and structural behavior. Limitations, as well as pros and cons of these assumptions are discussed. Special attention is drawn to load distribution within the joint, since it is important for fastener-based design, currently prescribed by the European design standard. Load distribution in joints is also important for verification against brittle failure modes. As an alternative to fastener-based design, joint-based design, by means of a framework for applying the presented model to plastic design of timber structures with ductile joints, is proposed.

  • 23.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    A Novel Approach for the Load-Displacement Behavior of Single-Dowel Connections in Laminated Veneer Lumber2016Inngår i: 17th International Conference on Experimental Mechanics, Rhodes, Greece, July 3-7, 2016, 2016Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The load-to-grain orientation dependence of the mechanical behavior of single-dowel connections is discussed in this contribution. The effect of the anisotropy of wood was experimentally assessed by means of a novel biaxial test set-up. Thus, lateral reaction forces in addition to forces parallel to the prescribed displacement direction could be quantified. Material properties of the components, namely the steel dowel and the Laminated Veneer Lumber were measured as well. This comprehensive experimental dataset was further exploited in an engineering model for single-dowel connections.

  • 24. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Eberhardsteiner, Josef
    An engineering modeling approach for the load-deformation behavior of multi-dowel connections in timber structures2017Inngår i: EMI 2017: Engineering Mechanics Institute Conference, June 4-7, 2017, San Diego, 2017Konferansepaper (Fagfellevurdert)
  • 25.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    An Engineering Modeling Approach for the Non-Linear Load-Displacement Behavior of Single Dowel Connections: Parameter Study2016Inngår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE), Vienna University of Technology, Austria , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A beam on non-linear elastic foundation model for consistent determination of the non-linear loaddisplacement behavior of single dowel connections is presented. The influence of certain parameters, like the load-tograin direction or the side member thickness on the connection behavior is demonstrated by means of a parameter study and compared to experimental findings.

  • 26. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Hochreiner, Georg
    Eberhardsteiner, Josef
    Ein baustatischer Modellierungsansatz für das Last-Verformungsverhalten von Stabdübelgruppen im Ingenieurholzbau2014Konferansepaper (Annet vitenskapelig)
  • 27. Schweigler, Michael
    et al.
    Bader, Thomas K.
    Hochreiner, Georg
    Eberhardsteiner, Josef
    Experimental Characterization of Dowel Connections beyond the Elastic Domain2015Inngår i: Presented at 32nd Danubia-Adria-Symposium (DAS 32), Zilina, Slovakia, 2015, s. 62-63Konferansepaper (Annet vitenskapelig)
  • 28.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Load-Deformation Behavior of Single Dowel Connections in Timber Structures2015Konferansepaper (Annet vitenskapelig)
  • 29.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Lemaître, Romain
    University of Lorraine, France.
    Parameterization equations for the nonlinear connection slip applied to the anisotropic embedment behavior of wood2018Inngår i: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 142, s. 142-158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nonlinear numerical models for the engineering design of mechanical connections in anisotropic materials require nonlinear material behavior of their components, which are essentially determined by material or structural testing. Herein, a multi-step approach for the parameterization of the nonlinear and anisotropic connection slip behavior is presented and applied to the ductile embedment behavior of steel dowels in wood. For this purpose, previously proposed regression functions for the slip behavior are reviewed, and further possible equations are discussed. Their suitability in the description of typical shapes of slip curves observed in connection testing is assessed before certain combinations are applied to an experimental dataset of embedment tests of steel dowels embedded in Laminated Veneer Lumber. The dependence of the regression parameters on the displacement range in the experimental dataset and the benefit of using parameters with a physical interpretation for being able to exploit connection test data reported in literature is highlighted.

  • 30.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    Unger, Gerhard
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Load-to-grain angle dependence of the embedment behavior of dowel-type fasteners in laminated veneer lumber2016Inngår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 126, s. 1020-1033Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Load-to-grain angle dependence of the embedment behavior of steel dowels in laminated veneer lumber, as a consequence of the anisotropic material behavior of wood, is experimentally investigated in this study. As a novel issue, in addition to the stress dependence, the displacement path of the dowel depend- ing on the load-to-grain angle, is discussed. Full-hole embedment tests of screw-reinforced LVL speci- mens up to dowel displacements of two times the dowel diameter and thus, representative for highly ductile dowel connections were conducted. Tests were performed with unconstrained lateral displace- ment boundary conditions of steel dowels with a diameter of 12 mm and 16 mm. Surface deformations were monitored with a full-field deformation measurement system. Increasing the load-to-grain angle caused reduced quasi-elastic limits and loading stiffness. However, for load-to-grain angles of 60 and higher, a pronounced displacement-hardening effect, leading to high embedment stresses at large dowel displacements, was observed. For the investigated dowel diameters, surface strains and plastic deforma- tions around the dowel indicate an almost dowel diameter independent load bearing area, which might explain higher nominal embedment stresses and consequently a more pronounced hardening effect of the smaller dowel diameter. Dowel displacements perpendicular to the initial loading direction, i.e., non- linear displacement paths of the dowel, were related to the anisotropic stiffness of wood and densifica- tion effects close to the dowel. The established experimental dataset was compared to current European timber engineering design equations and could serve as input to analytical and numerical models of dowel connections. 

  • 31.
    Schweigler, Michael
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Vessby, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Constrained displacement boundary condition in embedment testing of dowel-type fasteners in LVL2017Inngår i: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 53, nr 6, artikkel-id e12238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of the loading orientation with respect to the grain direction of wood and the influence of the lateral dowel displacement boundary condition on the embedment behaviour of steel dowels in laminated veneer lumber (with parallel-laminated veneers) are investigated in this study. For limit states of the lateral boundary condition, the load-displacement behaviour was experimentally studied by means of full-hole embedment tests on screw-reinforced laminated veneer lumber, for two dowel diameters and up to large dowel displacements. A novel biaxial test set-up is proposed for embedment tests with constrained lateral dowel displacement boundary condition, in order to quantify laterally evoked reaction forces. Corresponding forces were found to change orientation with increasing dowel displacement and amounted to about 20% and 40% of the vertical reaction force for dowel displacements of 5 mm and twice the dowel diameter, respectively. The influence of the lateral displacement boundary condition was highlighted by comparison of the test data with a previously established data set for unconstrained embedment testing. Constrained loading showed a stiffer response and higher nominal embedment stresses, as well as a more pronounced displacement hardening, compared to unconstrained loading.

  • 32.
    Schweigler, Michael
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Sandhaas, Carmen
    Karlsruhe Institute of Technology, Germany.
    Database and paramterization of embedment slip curves2018Inngår i: Design of Connections in Timber Structures: A state-of-art report by COST Action FP1402/WG3 / [ed] Carmen Sandhaas, Jorgen Munch-Andersen, Philipp Dietsch, Aachen: Shaker Verlag, 2018, s. 87-93Kapittel i bok, del av antologi (Fagfellevurdert)
1 - 32 of 32
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