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  • 1.
    Abdeljaber, Osama
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Scaling an OMA Modal Model of a Wood Building Using OMAH and a Small Shaker2020In: Topics in Modal Analysis & Testing: Volyme 8 / [ed] Dilworth B., Mains M., Springer, 2020, p. 151-157Conference paper (Refereed)
    Abstract [en]

    Operational modal analysis, OMA, results in unscaled mode shapes, since no forces are measured. Yet, obtaining a scaled modal model, i.e. knowing the modal mass of each mode (assuming proportional damping), is essential in many cases for structural health monitoring and load estimation. Several methods have therefore recently been developed for this purpose. The so-called OMAH method is a recently developed method for scaling OMA models, based on harmonic excitation of the structure. A number of frequencies are excited, one by one, and for each frequency, one or more frequency response values are calculated, that are then used for estimation of the modal masses of each mode, and residual effects of modes outside the frequency of interest. In the present paper, measurements were made on a four-story office building which was excited with a small, 200 N sine peak electrodynamic shaker. It is demonstrated that this small shaker was sufficient to excite the building with a force level of approx.. 1.8 N RMS close to the first eigenfrequency of the building, which was sufficient to produce harmonic response across the building. Reliable modal masses were possible to obtain within an accuracy of 6%. This demonstrates the feasibility of the OMAH method.

  • 2.
    Amaddeo, Carmen
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Ambient Vibration Tests and Modal Analysis of a Six-Story Lightweight Timber Frame Building2023In: World Conference on Timber Engineering (WCTE 2023): 19-22 June, Oslo, World Conference on Timber Engineering (WCTE) , 2023, p. 2898-2906Conference paper (Refereed)
    Abstract [en]

     This paper describes the in-situ ambient vibration tests of a lightweight timber frame building, performed in order to obtain its modal properties. Our case study is a six-story lightweight timber frame building in Varberg, Sweden. Five battery-driven wireless data acquisition units with a total of 14 uni-axial accelerometers were used to perform the in-situ measurements. Accelerations along the two horizontal directions were recorded with a duration of approximately 40 minutes. Two different only-output frequency and time domain Operational Modal Analysis (OMA) methods were used to evaluate the dynamic properties of the building. The modal parameters obtained from the in-situ measurements, such as natural frequencies and mode shapes, were compared with the parameters obtained from the Finite Element (FE) model of the structure. To perform a detailed numerical analysis of the light-frame timber building, all lateral-load resisting system components were modelled. The FE model was calibrated in function of the results obtained from the OMA of the building. Based on the obtained results from the calibrated FE model, it was possible to conclude that the non-structural elements have an influence on the global dynamic response of the building.

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  • 3.
    Amaddeo, Carmen
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dynamic characterization of a six-story light-weight timber-frame building2022In: Proceedings of the SHATIS 2022: 6th International Conference on Structural Health Assessment of Timber Structures, 7-9 September 2022, Prague, 2022 / [ed] Jiřı Kunecky & Hana Hasnıkova, Institute of Theoretical and Applied Mechanics , 2022, p. 173-179Conference paper (Refereed)
    Abstract [en]

    Multi-story residential and commercial timber buildings are an efficient solution for sustainable cities. Numerous projects have been and are expected to be realized in Sweden. In-situ wind-induced ambient vibrations tests have been conducted on a six-story light-weight timber-frame building in Varberg (Sweden). The load-bearing structure is composed of outer walls and some interior walls. For horizontal stabilization, the walls are supported by a bracings system realized with steel rods. To perform the in-situ measurements, multiple battery-driven data acquisition units, with uni-axial accelerometers have been used. Repeated measurements at different positions have been performed to be able to collect data at each floor and along both directions (longitudinal and transversal). Two different Operational Modal Analysis (OMA) methods have been used to evaluate the modal parameters: frequency, damping and mode shapes. The in-situ dynamics properties have been compared with the dynamic properties obtained from the Finite Element (FE) model of the structure.

  • 4.
    Amaddeo, Carmen
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    System identification of a six-story lightweight timber frame building using ambient vibration measurements at different environmental conditions2023In: Experimental Vibration Analysis for Civil Engineering Structures. EVACES 2023 / [ed] Limongelli, M.P., Giordano, P.F., Quqa, S., Gentile, C., Cigada, A., Springer, 2023, p. 569-578Conference paper (Refereed)
    Abstract [en]

    Ambient vibrations of a six-story lightweight timber frame building were measured under different environmental conditions in order to obtain the modal parameters of the structure. Changes in temperature and relative humidi-ty in timber can influence its response in terms of modal parameters. Namely, a moisture content change in the timber can affect stiffness, strength, and shape of the elements as well as the properties of the connections. Monthly measure-ments have been performed on a six-story lightweight timber frame building in Varberg, Sweden, built in 2021. The in-situ tests were performed using five bat-tery-driven data acquisition units with 14 uni-axial accelerometers. Additional-ly, the building is permanently monitored using temperature and humidity sen-sors, starting ever since its construction phase. The ambient vibration data have been analyzed using two different only-output methods. The results obtained under different temperature and humidity conditions were compared in order to assess the effect of the environmental conditions in the building. This infor-mation can be used to ensure the building meets safety and performance re-quirements, as well as to identify potential issues that may need to be addressed during building design.

  • 5.
    Amaddeo, Carmen
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Larsson, Carl
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Finander, Per
    SAAB Combitech, Sweden.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Development of a modular data acquisition system for structural health monitoring2024In: Vibroengineering Procedia, 2024Conference paper (Refereed)
    Abstract [en]

    Dynamic measurements are widely used to perform structural health monitoring of existing structures and operational modal analysis. This paper describes the design steps and applications of a multi-channel modular data acquisition system to perform in-situ and laboratoryscale experimental and operational modal analysis. The main advantages of a modular system compared to a traditional data acquisition system are flexibility, easy and fast deployment, and minimal interference with the surroundings. Several experiments have been conducted in order to validate and evaluate the data acquisition system. The results show that the system is versatile and can acquire high-quality and reliable data.

  • 6.
    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.

  • 7.
    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.

  • 8.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Schweigler, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dodoo, Ambrose
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Competitive CLT - Improving the competitive advantage of CLT-based building systems through engineering design andreduced carbon footprint: Final report2024Report (Other academic)
  • 9.
    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)
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  • 10.
    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.

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  • 11.
    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

  • 12.
    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.

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  • 13.
    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.

  • 14.
    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.

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  • 15.
    Dodoo, Ambrose
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Structural engineering and carbon footprints of CLT buildings: Commentary2022In: Buildings & Cities, ISSN 2632-6655 , Vol. 17 JanuaryArticle in journal (Other academic)
  • 16.
    Dodoo, Ambrose
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Truong, Nguyen Le
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Exploring the synergy between structural engineering design solutions and life cycle carbon footprint of cross-laminated timber in multi-storey buildings2022In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, no 1, p. 30-42Article in journal (Refereed)
    Abstract [en]

    Low-carbon buildings and construction products can play a key role in creating a low-carbon society. Cross-laminated timber (CLT) is proposed as a prime example of innovative building products, revolutionising the use of timber in multi-storey construction. Therefore, an understanding of the synergy between structural engineering design solutions and climate impact of CLT is essential. In this study, the carbon footprint of a CLT multi-storey building is analysed in a life cycle perspective and strategies to optimise this are explored through a synergy approach, which integrates knowledge from optimised CLT utilisation, connections in CLT assemblies, risk management in building service-life and life cycle analysis. The study is based on emerging results in a multi-disciplinary research project to improve the competitiveness of CLT-based building systems through optimised structural engineering design and reduced climate impact. The impacts associated with material production, construction, service-life and end-of-life stages are analysed using a process-based life cycle analysis approach. The consequences of CLT panels and connection configurations are explored in the production and construction stages, the implications of plausible replacement scenarios are analysed during the service-life stage, and in the end-of-life stage the impacts of connection configuration for post-use material recovery and carbon footprint are analysed. The analyses show that a reduction of up to 43% in the life cycle carbon footprint can be achieved when employing the synergy approach. This study demonstrates the significance of the synergy between structural engineering design solutions and carbon footprint in CLT buildings.

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  • 17.
    Dorn, Michael
    Vienna University of Technology.
    3D-Modeling of Dowel-Type Timber Connections2009Report (Other academic)
  • 18.
    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)
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  • 19.
    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

  • 20.
    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)
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  • 21.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Klaeson, Jonas
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Structural Health Monitoring of House Charlie2019Report (Other academic)
    Abstract [en]

    House Charlie is an office building located in Växjö, Sweden, with approx. 5,700 m2 area on four floors, fitting 3,700 m2 of office space, and 2,000 m2 of restaurants and conference rooms. The load-bearing structure is a column-beam system made from glued laminated timber (Glulam) with the flooring made from cross-laminated timber (CLT). The house is equipped with a net-work of sensors which were already installed during the construction phase. The design of the network was done in collaboration between the Department of Building Technology from Linnaeus University and SAAB, in close contact Videum and JSB, the owner and constructor, respectively. In the network, two sensor cards collect data from the sensor (displacement, relative humidity, temperature, vibrations, as well as weather station data) which is accessible via a 3G-router from the outside. Except for power supply the network is work-ing independently from the buildings facilities. The building was erected and the network installed during spring 2018, since then the network is providing data. The report describes the measurement network and its sensors as well as their positioning within the building. Additionally the results are presented for the time-span July 2018-December 2019 as well as an interpretation of the first 1.5 years of run-time are given.

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  • 22.
    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.

  • 23.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    de Borst, Karin
    Eberhardsteiner, Josef
    Experiments on dowel-type timber connections2013In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 47, p. 67-80Article in journal (Refereed)
    Abstract [en]

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

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  • 24.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Habrova, Karolina
    Czech Univ Life Sci Prague, Czech Republic.
    Koubek, Radek
    Daikin UK, UK.
    Serrano, Erik
    Lund University, Sweden.
    Determination of coefficients of friction for laminated veneer lumber on steel under high pressure loads2021In: Friction, ISSN 2223-7690, E-ISSN 2223-7704, Vol. 9, p. 367-379Article in journal (Refereed)
    Abstract [en]

    In this study, static coefficients of friction for laminated veneer lumber on steel surfaces were determined experimentally. The focus was on the frictional behaviors at different pressure levels, which were studied in combination with other influencing parameters: fiber orientation, moisture content, and surface roughness. Coefficients of friction were obtained as 0.10-0.30 for a smooth steel surface and as high as 0.80 for a rough steel surface. Pressure influenced the measured coefficients of friction, and lower normal pressures yielded higher coefficients. The influence of fiber angle was observed to be moderate, although clearly detectable, thereby resulting in a higher coefficient of friction when sliding perpendicular rather than parallel to the grain. Moist specimens contained higher coefficients of friction than oven-dry specimens. The results provide realistic values for practical applications, particularly for use as input parameters of numerical simulations where the role of friction is often wrongfully considered.

  • 25.
    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.

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  • 26.
    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.

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    abstract
  • 27.
    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)
  • 28.
    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.

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  • 29.
    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.

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  • 30.
    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.

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  • 31.
    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.

  • 32.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Larsson, Carl
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Coupling of Weather Data to Moisture content in an Timber Building2022In: Proceedings of the SHATIS’22: 6th International Conference on Structural Health Assessment of Timber Structures, 7-9 September 2022, Prague, 2022 / [ed] Jiřı Kunecky & Hana Hasnıkova, Institute of Theoretical and Applied Mechanics , 2022, p. 150-155Conference paper (Refereed)
    Abstract [en]

    Wood and wood-based products interact with the surrounding environment. The interaction with moisture is particularly interesting since it influences the structural properties and may lead to degradation. A structural health monitoring system was established in House Charlie, a four-story office building in Växjö, Sweden, made from timber. It has been running since summer 2018, collecting vibration data and information on temperature and humidity at multiple positions within the façade and the slab. The present work shows that the moisture content within a slab of the building varies throughout the years, attributed to an ongoing dry-out and seasonal changes. Furthermore, the variation is directly coupled with the weather data from a public weather station in Växjö.

  • 33.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Larsson, Carl
    Linnaeus University, Faculty of Technology, Department of Building Technology. Skanska Teknik, Sweden.
    Amaddeo, Carmen
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Changes in eigenfrequencies of CLT elements due to a variation of ambient conditions2023In: Experimental Mechanics in Engineering and Biomechanics: Proceedings ICEM 2020th International Conference on Experimental Mechanics, Porto 2-7 July 2023, INEGI-Instituto de Engenbaria Mecanica e Gestao Industrial, 2023, p. 989-990, article id 20001Conference paper (Refereed)
    Abstract [en]

    Wood is widely used in the construction sector and gaining increased market share. It isinteracting with the surrounding so that its mechanical and geometrical properties (stiffness,strength, swelling, density, …) change with temperature and humidity levels. In a full-scalebuilding, the eigenfrequencies are hence also varying with the climate. In the current paper,results from a preliminary experimental study are presented. A beam made from cross-laminated timber was hanging freely supported inside a climate chamber. Enforced vibrationsfrom a controlled shaker were taken to obtain the eigenfrequencies. With decreasing moisturecontent, the first and third eigenfrequencies were increasing (bending modes) while the secondeigenfrequency was decreasing (torsional mode). A finite element study allowed for checkingwhich parameters is influencing to which degree so that individual changes can be combined.

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  • 34.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Larsson, Carl
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Amaddeo, Carmen
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Samband mellan styvhet och ändring av fukthalt i KL-trä vid lågmekanisk belastning: Slutrapport till förstudieprojekt2023Report (Other academic)
    Abstract [sv]

    Korslimmat trä (KL-trä) tillverkas av brädor som limmas ihop korsvis i flera skikt. Skivorna som erhållsanvänds som byggelement, mestadels för väggar och bjälklagselement. Utgångsmaterialet trä tarstår i jämvikt med det omgivande klimatet och kommer därför ändra fuktkvoten. I studien undersöktesen skiva av KL-trä under varierande fuktförhållanden i en klimatkammare hos Linnéuniversitetet.Egenfrekvenser samt fuktkvoten följdes upp och sambandet med klimatet studerades. Det visade sigatt första och tredje uppmätta egenfrekvensen (böjning) visade negativ korrelation med omgivandefukten, den gick upp när fukten minskades (och tvärtom). För andra egenfrekvensen (torsion)däremot visade sig ett mer komplicerat samband. Ett flertal möjliga orsaker presenteras som förklaring. Medverkande organisationer var Linnéuniversitetet som huvudpart samt SödraSkogsägarna och Saab som bidragit som stödfunktionen och bollplank.

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  • 35.
    Dorn, Michael
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Tuvendal, Helena
    Södra skogsägarna, Sweden.
    Henrik, Oxfall
    Swerea, Sweden.
    Serrano, Erik
    Lund university, Sweden.
    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.

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  • 36. 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-Net project 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.

  • 37.
    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.

  • 38.
    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.

  • 39.
    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 och Teknik, ISSN 0281-658X, E-ISSN 2002-8350, 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.

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  • 40.
    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.

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  • 41.
    Kozłowski, Marcin
    et al.
    Silesian University of Technology, Poland;Lund University, Sweden.
    Lenk, Peter
    ARUP, UK.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Honfi, Dániel
    RISE Research Institutes of Sweden, Sweden.
    Sjöström, Johan
    RISE Research Institutes of Sweden, Sweden.
    Structural considerations on timber-glass composites at fire scenarios2018In: Challenging Glass 6: Conference on Architectural and Structural Applications of Glass, CGC 2018 - Proceedings, TU Delft Open , 2018, p. 229-240Conference paper (Refereed)
    Abstract [en]

    This paper focuses on a recently developed concept, in which glass is combined with timber to provide post-breakage strength and ductility. This combination allows for good post-breakage performance and overall robustness of timber-glass composite beams and wall elements, which has been reported in several publications. The application of timber-glass elements in practice, however, raises important issues related to structural fire performance. The paper elaborates on this issue and provides general information about the behavior of glass, timber and adhesives at elevated temperatures and under fire conditions. Furthermore, it presents ideas and strategies developed for potential application of timber-glass composites in practical situations. The paper presents also initial results from an on-going research project on fire performance of timber-glass composites Copyright © with the authors. All rights reserved.

  • 42.
    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.

  • 43.
    Larsson, Carl
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Modal Analysis and Finite Element Model Updating of a Timber-concrete Hyblrid Building2022In: Proceedings of SHATIS 2022: 6th International Conference on Structural Health Assessment of Timber Structures, 7-9 September 2022, Prague, 2022 / [ed] Jiří Kunecký & Hana Hasníková, Institute of Theoretical and Applied Mechanics , 2022, p. 193-199Conference paper (Refereed)
    Abstract [en]

    In recent years, there has been a rapid development of new timber products, such as cross-laminated timber, leading to an increase in buildings using timber as a structural material. House Charlie, a 4-story office building in Växjö, Sweden, is a typical example of a hybrid building that uses glulam timber for the post-beam system combined with slabs in cross-laminated timber and shear walls in concrete. A structural health monitoring system has been installed, collecting data ever since its completion in 2018. This work presents the building's modal performance collected by geophones under ambient vibrations over three years, which are used to calibrate a finite element model. The effects of changes in different material properties and model assumptions on the overall dynamic behavior of the building are shown. The aim is to establish a structural model that captures the actual behavior of the built structure that uses both timber and concrete as structural materials.

  • 44.
    Larsson, Carl
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bolmsvik, Åsa
    Skanska Sverige AB, Sweden.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Long-term analysis of the environmental effects on the global dynamic properties of a hybrid timber-concrete building2022In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 268, article id 114726Article in journal (Refereed)
    Abstract [en]

    With the increased availability of timber materials, such as cross-laminated timber, the number of buildings using timber as a structural material has been rapidly increasing. As these buildings are new to the market, limited data and research on their long-term structural modal performance are available. This is particularly important in timber buildings since the material properties of wood are highly affected by environmental factors, especially the moisture content. Over time, the evolution of the dynamic properties is essential for damage indication in structural health monitoring systems since natural changes can mask the influence of damage. This work presents three years of observations from a structural monitoring system collecting data ever since completing a four-story timber-concrete hybrid building in Sweden. Ambient vibrations of the building were measured using geophones, resulting in 3,100 datasets. The temperature and relative humidity were measured both externally using a weather station and internally using sensors embedded in several walls and a slab in the building. The observed natural frequencies of the building vary with +/- 0.2 Hz around the mean value over time. Linear regression analysis shows a significant correlation between the moisture content of a cross-laminated timber slab and the natural frequencies (coefficient of determination R2 up to 0.84). A predictive model for the natural frequencies is presented, taking seasonal variations and a dry-out of the structure into account. Variations from the expected values are +/- 0.1 Hz at most. The model clearly narrows the error margins for damage indication in a structural health monitoring system.

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  • 45.
    Larsson, Carl
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Abdeljaber, Osama
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dynamic Evaluation of a Nine-Story Timber-Concrete Hybrid Building during Construction2023In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 289, article id 116344Article in journal (Refereed)
    Abstract [en]

    Timber-concrete hybrid buildings are an innovative solution to increase the amount of timber materials used in modern buildings. This study presents a dynamic evaluation of a nine-story timber-concrete hybrid residential building during construction. The building consists of a seven-story structure in cross-laminated timber (CLT) on top of two stories in concrete. Ambient vibration tests were conducted seven times during the 13-month construction period, including tests with only the structural elements in place and tests of the finished building with the façade, non-structural walls, and other internal finishing. The results show a clear decrease in the natural frequencies of the building as the building gets higher and more elements are installed. However, a slight increase in the natural frequency was observed following the installation of the non-structural walls in the final construction stage. A corresponding finite element analysis is presented for each test, providing additional insights into the parameters typically used in the structural design process. The study demonstrates the importance of properly selecting reduction factors for CLT elements in a dynamic finite element analysis. It also shows the importance of considering non-structural walls, both regarding weight and stiffness, even in buildings where the number of non-structural walls is relatively small compared to structural walls.

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  • 46.
    Larsson, Carl
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    A Survey of the design of timber-concrete hybrid buildings in Sweden2023In: World Conference on Timber Engineering (WCTE 2023), 19-22 June, Oslo / [ed] Nyrud A.Q., Malo K.A., Nore K., Alsen K.W.L., Tulebekova S., Staehr E.R., Bergh G., Wuyts W., Oslo: World Conference on Timber Engineering (WCTE) , 2023, p. 4338-4344Conference paper (Refereed)
    Abstract [en]

    There is a growing interest in timber buildings in Sweden and increased availability of Glulam (GLT) andparticularly Cross Laminated Timber (CLT) products. Timber buildings, though, often have difficulties in fulfilling theperformance requirements of a building project. The use of concrete elements in addition to timber elements in the load-bearing structure is a widespread solution, introducing timber-concrete hybrid buildings. The study presents responsesfrom interviews regarding ten different timber-concrete hybrid building projects in Sweden with a load-bearing structureabove the foundation level in both timber and concrete. Four main types of timber-concrete hybrids were found: a CLTstructure on top of a concrete structure, a post-beam system in GLT with CLT slabs and concrete walls, a post-beamsystem in GLT with concrete hollow core slabs, and a timber structure with some slabs in concrete. The results show thattimber-concrete hybrid buildings are flexible and suitable for various construction types. The reasons for using concretein timber construction were primarily to increase self-weight, obtain longer span lengths, and overcome shear wallcapacity issues. There is still a lack of competence in the design of structural timber projects, and at most, five differentstructural designers were involved in the load-bearing design of a single building. This highlights issues regarding projectmanagement of the design process within timber-concrete hybrid buildings

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  • 47.
    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)
  • 48.
    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, 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.

  • 49.
    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”

  • 50.
    Pantak, Marek
    et al.
    Cracow University of Technology, Poland.
    Schirén, Whokko
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Larsson, Carl
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Dynamic characteristics and dynamic response of timber footbridges to dynamic human activities2023In: World Conference on Timber Engineering (WCTE 2023), 19-22 June, Oslo, World Conference on Timber Engineering 2023 (WCTE 2023) , 2023, p. 1930-1935Conference paper (Refereed)
    Abstract [en]

    The dynamic action of footbridge users in different forms of activity (especially during walking andrunning) may cause an excessive vibration of the footbridge deck and may disturb the comfort of use of the structure. Thedynamic susceptibility of the footbridges varies depending on the construction material used to build the footbridge andthe typical construction solutions (construction details) resulting from the construction material used. The paper presentsthe basic dynamic characteristics of timber footbridges of various structural solutions, collected during dynamic field testsof these structures. The obtained results indicate relatively high dynamic resistance of timber footbridges to the dynamicloads generated by users under normal conditions of use. In addition, the results show that in the case of timberfootbridges, it is possible to consider changing the requirements of international standards defining the range of naturalfrequencies sensitive to the dynamic impact of users. In the case of timber footbridges, characterized by a relatively highself-weight (compared to steel footbridges), high stiffness and high damping, it is possible to consider changing therequirements for performing forced vibration analyses only for structures with fundamental vertical vibration frequency fv <= 3.0 Hz instead of the currently defined fv <= 5.0 Hz.

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