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  • 1. Challamel, Noel
    et al.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boundary-Layer Effect in Composite Beams with Interlayer Slip2011In: Journal of Aerospace Engineering, ISSN 0893-1321, Vol. 24, no 2, 199-209 p.Article in journal (Refereed)
    Abstract [en]

    An apparent analytical peculiarity or paradox in the bending behavior of elastic-composite beams with interlayer slip, sandwich beams, or other similar problems subjected to boundary moments exists. For a fully composite beam subjected to such end moments, the partial composite model will render a nonvanishing uniform value for the normal force in the individual subelement. This is from a formal mathematical point of view in apparent contradiction with the boundary conditions, in which the normal force in the individual subelement usually is assumed to vanish at the extremity of the beam. This mathematical paradox can be explained with the concept of boundary layer. The bending of the partially composite beam expressed in dimensionless form depends only on one structural parameter related to the stiffness of the connection between the two subelements. An asymptotic method is used to characterize the normal force and the bending moment in the individual subelement to this dimensionless connection parameter. The outer expansion that is valid away from the boundary and the inner expansion valid within the layer adjacent to the boundary (beam extremity) are analytically given. The inner and outer expansions are matched by using Prandtl's matching condition over a region located at the edge of the boundary layer. The thickness of the boundary layer is the inverse of the dimensionless connection parameter. Finite-element results confirm the analytical results and the sensitivity of the bending solution to the mesh density, especially in the edge zone with stress gradient. Finally, composite beams with interlayer slip can be treated in the same manner as nonlocal elastic beams. The fundamental differential equation appearing in the constitutive law associated with the partial-composite action in a nonlocal elasticity framework is discussed. Such an integral formulation of the constitutive equation encompassing the behavior of the whole of the beam allows the investigation of the mechanical problem with the boundary-element method.

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

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

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

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

  • 4.
    Daerga, Per-Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Kallsner, Bo
    A complete timber building system for multi-storey buildings2014In: Construction materials and structures, 2014, 1164-1171 p.Conference paper (Refereed)
    Abstract [en]

    The Masonite Flexible Building (MFB) system is a complete timber building system for commercial and residential multi-storey houses. The system is for tall and large buildings with long floor spans. The MFB system uses prefabricated wall, floor and roof elements which are delivered in flat packages and erected on the construction site. The MFB system might be classified as a panel construction, where the load-carrying structure consists of composite lightweight timber I-beams mechanically integrated with a composite laminated wood panel called PlyBoard T. The I-beams and the panel form a strong and rigid carcass for wall and floor elements, making the system well suited for high rise construction. A key feature of the MFB system is the connection technique which enables swift erection of the system units on site. The PlyBoard T panels are provided with a continuous slot along the periphery. The slot is used as a general connection interface for the joining of the wall elements. The floor elements are suspended and hooked onto the bearing walls using sheet steel hangers, allowing swift assembling of the floor deck and enabling direct vertical wall-to-wall load transfer parallel to grain. The paper presents the construction principles, system components and units, erection technique, functional and architectural aspects of the Masonite Building System.

  • 5.
    Daerga, Per-Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University of Technology.
    Källsner, Bo
    Linnæus University.
    Masonite Flexible Building System for Multi-Storey Timber Buildings2012In: World Conference on Timber Engineering 2012 (WCTE 2012) / [ed] Pierre Quenneville, 2012Conference paper (Other academic)
    Abstract [en]

    ABSTRACT: The Masonite Flexible Building (MFB) system is a complete timber building system for commercial and residential multi-storey houses. The system is subdivided into two market variants; XL and Light. The XL version is for tall and large buildings with long floor spans while the Light version is adapted for smaller buildings with lower loads. Though differing in technical performance, the functional criteria are the same for both variants. The MFB system uses prefabricated wall, floor and roof elements which are delivered in flat packages and erected on the construction site. The MFB system might be classified as a panel construction, where the load-carrying structure consists of composite light-weight timber I-beams mechanically integrated with a composite laminated wood panel called PlyBoard™. The I-beams and the panel form a strong and rigid carcass for wall and floor elements, making the system well suited for high rise construction. A key feature of the MFB system is the connection technique which enables swift erection of the system units on site. The plyboard panels are provided with a continuous slot along the periphery. The slot is used as a general connection interface for the joining of the wall elements. The floor elements are suspended and hooked onto the bearing walls using sheet steel hangers, allowing swift assembling of the floor deck and enabling direct vertical wall-to-wall load transfer parallel to grain. The paper presents the construction principles, system components and units, erection technique and functional and architectural aspects of the Masonite Building System.

    KEYWORDS: Masonite Flexible Building system, multi-storey timber buildings, slotted-in connections, suspended connections, functionality requirements.

  • 6.
    Daerga, Per-Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University of Technology.
    Källsner, Bo
    Linnæus University.
    Slotted-in Steel-Plate connections for Panel Wall Elements - Experimental and Analytical Study2012In: World Conference on Timber Engineering 2012 (WCTE 2012) / [ed] Pierre Quenneville, 2012, 451-460 p.Conference paper (Other academic)
    Abstract [en]

    ABSTRACT: This paper presents an experimental and analytical study of a steel plate connection for joining walls in the Masonite Flexible Building (MFB) system. These connections are used partly for splicing the wall elements and partly for tying down uplifting forces and resisting horizontal shear forces in stabilizing shear walls. The steel plates are inserted in a perimeter slot in the plyboard panel (a composite laminated wood panel) and fixed mechanically with screw fasteners. The load-bearing capacity of the slotted-in steel plate connections are determined experimentally and derived analytically for different failure modes. The test results show ductile post-peak load-slip characteristics, indicating that a plastic design method for shear walls can be applied to calculate the horizontal load-bearing capacity. The slotted-in steel plate connection concept can also be used for joining shear walls to transverse walls for tying down purposes in order to simplify the stabilization system of the building. The use of transverse walls for resisting uplifting forces introduces a three-dimensional behaviour of the wall junction and a more effective load transfer.

    KEYWORDS: Slotted-in steel plate timber connections, timber wall elements, multi-storey timber building, Masonite Flexible Building system.

  • 7.
    Daerga, Per-Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University of Technology.
    Källsner, Bo
    Linnæus University.
    Suspended Floor Element Connections for the Masonite Flexible Building System2012In: World Conference on Timber Engineering 2012 (WCTE 2012) / [ed] Pierre Quenneville, 2012, 465-472 p.Conference paper (Other academic)
    Abstract [en]

    The authors present an experimental study of a suspended floor element connection (sheet steel hangers) employed in the Masonite Flexible Building (MFB) system. The hangers are mounted with screws and are pre-attached to the floor elements at manufacturing. This arrangement makes the design of the hanger critical with respect to safety and load transfer redundancy, since the screws transfer all the loads, both withdrawal and shear forces can act simultaneously. Tests have been carried out to examine the structural behaviour of the hanger. The two most critical load cases, vertical floor load and horizontal wind suction load, and three different screw joint configurations were investigated. The results indicate that the vertical distance between the screw joint and the upper edge of the rim beam should be increased and that withdrawal forces on the screws should be kept as low as possible. Some suggestions for improving the present design are given and a modified design is proposed to enhance the load-bearing capacity and to improve the overall safety and redundancy.

  • 8.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A simplified analysis method for composite beams with interlayer slip2009In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 51, no 7, 515-530 p.Article in journal (Refereed)
    Abstract [en]

    A simplified static procedure is proposed for analysing and designing composite beams with interlayer slip. The method is parallel to the Eurocode 5 method, but it is general in nature and can be applied to arbitrary boundary and loading conditions. In contrast with Eurocode 5, a general and correct way of choosing the effective beam length of the problem is given by the present procedure, which is that the effective beam length equals the buckling length that is found in the corresponding column buckling problem. The procedure predicts the deflections and internal actions and stresses, in principle by replacing the fully composite bending stiffness (EI(infinity)) with the effective (partially) composite bending stiffness (EI(eff)) in the expressions for these quantities in the corresponding fully composite beam. This effective bending stiffness depends on two non-dimensional parameters: the composite action parameter (shear connection stiffness) and the relative bending stiffness parameter. The method is applied to a number of simple practical cases and the results obtained have been compared with the exact values. The applicability of the simplified analysis procedure was found to be very good, except for interlayer shear stresses. The error in the Eurocode 5 procedure, as compared with the method proposed in this paper, can in some cases be up to almost 30% depending on the boundary conditions.

  • 9.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Composite beam-columns with interlayer slip: approximate analysis2008In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 50, no 12, 1636-1649 p.Article in journal (Refereed)
    Abstract [en]

    An approximate second order analysis procedure for composite beam-columns with interlayer slip subjected to transverse loading and axial compressive loads is developed. The magnification factors to be applied to the first order solutions in order to estimate the deflections and internal forces obtained by the second order analysis approach are presented. The method of applying magnification factors to internal axial forces is discussed. The approximate second order analysis procedure is developed for the four Euler cases with various transverse load conditions. The procedure is applied to and the accuracy is illustrated for simply supported partially beam-columns of steel and concrete, and timber and concrete with different bending stiffness and interlayer slip properties. The deflections and internal forces obtained by the approximate method compared extremely well, except for slip forces in case of very flexible shear connectors, with those obtained by the more rigorous second order analysis approach for different composite action (partial interaction) parameters (shear connector stiffness values). The study also shows that the magnification factor associated with the deflections can be utilized to estimate also the internal actions, except shear forces in case of very flexible shear connectors, in the second order case with minimal error for simply supported beam-columns. Thus. for members with shear connector stiffness of structural significance the proposed approximate method can be used in general for simply supported beam-columns. For other boundary and loading conditions, the approximate method needs to be re-evaluated. The approach of using one magnification factor greatly simplifies the analysis task for those components.

  • 10.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kallsner, Bo
    Analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls: elastic model2009In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 42, no 3, 321-337 p.Article in journal (Refereed)
    Abstract [en]

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

  • 11.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Källsner, Bo
    Elasto-plastic model for analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 9, 2182-2193 p.Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Källsner, Bo
    Linnéuniversitetet, School of Engineering.
    Gustafsson, Per Johan
    Lunds universitet, Konstruktionsteknik.
    Johnsson, Helena
    Luleå tekniska universitet, Samhällsbyggnad och naturresurser.
    Stabilisering och bjälklag kritiska för höghus i trä2011In: Husbyggaren, ISSN 0018-7968, Vol. 53, no 1, 16-21 p.Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    INDUSTRI- OCH KONTORSBYGGANDE Stabilisering och bjälklagsutformning är kritiska moment vid byggandet av flervåningshus i trä. Bjälklagen måste bland annat klara stora spännvidder. Nu finns en nyutvecklad plastisk metod som ska säkra horisontalstabilisering. 

  • 13.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pajari, Matti
    Tests and analysis on shear strength of composite slabs of hollow core units and concrete topping2008In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 22, no 8, 1708-1722 p.Article in journal (Refereed)
    Abstract [en]

    Prestressed concrete hollow core slabs are commonly used as load-bearing floors and roofs. The upper surface of the hollow core slabs is usually levelled with a cast-in situ screed or concrete topping. Reducing the thickness of the precast unit and increasing the thickness of the concrete topping, but maintaining the load-carrying capacity for the whole composite section is technically and economically an interesting alternative. The expensive screed could be replaced by a cheaper concrete and installations could be embedded in the topping layer. Proper shear and bond strength at the interface is required for composite action. An experimental and theoretical study on the effect of structural topping on the shear capacity of hollow core slabs and of the adequacy of the shear or bond strength of the non-treated interface is presented. It is concluded that concrete topping can be used to improve the shear capacity of hollow core units. For the test specimens, the theoretical increase was of the order of 35%, which was verified by the tests. The bond strength at the interface is adequate and the topping interacts with the slab in a proper manner.

  • 14.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pan, Dan H
    Exact static analysis of partially composite beams and beam-columns2007In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 49, no 2, 239-255 p.Article in journal (Refereed)
    Abstract [en]

    The ordinary differential equations and general solutions for the deflection and internal actions and, especially, the pertaining consistent boundary conditions for partially composite Euler-Bernoulli beams and beam-columns are presented. Static loading conditions, including transverse and axial loading and first- and second-order analyses are considered. The theoretical procedure is applicable to general loading and boundary conditions for uniform composite beams and beam-columns with interlayer slip. Further, the exact closed form characteristic equations and their associated exact buckling length coefficients for composite Columns with interlayer slip are derived for the four Euler boundary conditions. It is shown that these coefficients are the same as those for ordinary fully composite (solid) columns, except for the Euler clamped-pinned case. For the clamped-pinned case, the difference between the exact buckling length coefficient and the corresponding value for solid Columns is less than 1.8%, depending oil the so-called composite action parameter and relative bending stiffness parameter. Correspondingly, the maximum deviation between the exact and approximate buckling load is at most 2.5%. These small differences can in most practical cases be neglected. Also, the maximum theoretical range for the relative bending stiffness for partially composite beams and beam-columns is derived. An effective bending stiffness, valuable in the determination of the critical buckling load for partially composite members, is derived. This effective bending stiffness is also Suitable for analysing approximate deflections and internal actions or stresses in composite beams with flexible shear connection. The beam-column analysis is applied to a specific case. The difference in the approaches to the first- and second-order analysis is illustrated and the results clearly show the magnification in the actions and displacements due to the second-order effect. The magnification of the internal axial forces is different from magnifications obtained for the other internal actions, since only that portion of an internal axial force that is induced by bending is magnified by the second-order effect.

  • 15.
    Girhammar, Ulf Arne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pan, Dan H
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gustafsson, Anders
    Nanyan Technological University.
    Exact dynamic analysis of composite beams with partial interaction2009In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 51, 565-582 p.Article in journal (Refereed)
  • 16.
    Grundberg, Staffan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå tekniska universitet.
    A Comparison of Exact and Approximate Analyses of Partially Interacting Composite Beam-Columns2015In: Proceedings of the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing / [ed] J. Kruis, Y. Tsompanakis and B.H.V. Topping, Stirlingshire, UK: Civil-Comp Press , 2015, 261Conference paper (Refereed)
    Abstract [en]

    Solutions of the static Euler-Bernoulli equations of composite beam-columns with interlayer slip have been compared with an approximate theory. The inter-layer force was taken to be proportional to the inter-layer slip. The general solutions were obtained for four different sets of boundary conditions corresponding to the four Euler cases: clamped-free, pinned-pinned, clamped-pinned and clamped-clamped. A transverse static point load was considered. The beam was axially loaded. The contribution of the axial force to the bending moment, or equivalently the work done by the axial force on the beam due to its deflection, was taken into account in the second order theory and neglected in the first order theory. In the approximate theory the second order effects were described by an approximate magnification factor obtained from critical loads calculated by approximating the buckling length coefficients of the composite beam with interlayer slip by the buckling length coefficients of a solid beam. The contribution of second order effects to deflections and internal actions were calculated in terms of exact magnification factors at different stiffness of the composite action and the results were compared with the approximate theory. Two composite beams were considered. The first was a combination of concrete and timber and the second was a combination of concrete and steel. The positions of the maximum internal shear forces were shown to occur at different positions in the two layers of the beam of concrete and steel when the exact first and second order calculations were compared. The approximate theory was fairly accurate for the deflection but showed higher deviations for other quantities. The approximate theory needs further evaluation. The exact results have been obtained by analytical calculations in combination with numerical evaluation.

  • 17.
    Grundberg, Staffan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå tekniska universitet.
    Hassan, Osama A. B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Vibration of axially loaded and partially interacting composite beams2014In: International Journal of Structural Stability and Dynamics, ISSN 0219-4554, Vol. 14, no 1, 1350047- p.Article in journal (Refereed)
    Abstract [en]

    The vibrations of axially loaded composite beams with partial interaction are considered. The equations of motion and the pertaining boundary conditions are derived from Hamilton's principle. Mainly free — but also forced — vibrations are considered. The natural frequencies are calculated as a function of the axial force and the stiffness of the interaction between the layers. The analytical result obtained for the eigenfrequencies of the simply supported beam is taken as a starting point for an approximation of the eigenfrequencies of beams subject to other boundary conditions. The proposed approximation — which has no numerical fitting parameters — is shown to be in good agreement with the exact solutions, especially for the case of a beam clamped at both ends.

  • 18.
    Grundberg, Staffan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hassan, Osama
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Dynamics of axially loaded and partially Interacting  composite beams2012In: Proceedings of the 15th european conference on composite materials, 2012Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to study the dynamics of partially interacting composite beams subjectedto axial loads, a situation occurring in e.g. beam-columns. The eigenfrequencies arederived for the simply supported composite beam subjected to an axial force. Measurements ofthe fundamental frequencies of a simply supported composite beam consisting of three layersare carried out considering different values of the applied axial force. The agreement betweenthe theoretical and experimental results is discussed. It is also shown that the application ofthe axial force introduces frictional moments at the boundaries, which make the experimentalboundary conditions deviate somewhat from those of an ideal simply supported beam.

  • 19.
    Hassan, O. A. B.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Assessment of footfall-induced vibrations in timber and lightweight composite floors2013In: International Journal of Structural Stability and Dynamics, ISSN 0219-4554, Vol. 13, no 2, 1350015- p.Article in journal (Refereed)
    Abstract [en]

    In this paper, the footfall-induced vibrations in typical timber and lightweight composite floors in residential buildings are investigated. The two-floor structures have approximately comparable distributed mass and that the transverse flexural stiffnesses of the two structures are not substantially different. An analysis is carried out to assess the floor acceptability of the two structures, based upon derived expressions as well as some design codes and guidelines such as the Eurocode. For the analysis, two cases are considered for each floor structure: a composite action and noncomposite action. It has been shown that use of composite action, under certain conditions, has more advantages than its noncomposite counterpart with respect to the floor acceptability for general residential applications. Moreover, the limitations of the different criteria of the codes, guidelines for assessing floor vibrations in timber and lightweight floor structures, and possible improvements of these criteria are discussed in this paper.

  • 20.
    Hassan, Osama
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf-Arne
    Luleå tekniska universitet.
    Assessment of human-induced vibrations in composite timbre floors2012In: Proceedings of the 15th European Conference on Composite Materials, Italien, 2012Conference paper (Refereed)
    Abstract [en]

    The authors investigate the human induced vibrations in typical composite timber floors inresidential buildings. Assessment methods given in different design codes and guidelines,such as the Eurocode, are discussed. A case study analysis based on the differentmethodologies is carried out to assess the acceptability of a specific timber floor. Twoextreme cases are considered: full and non-composite action. It is shown that compositeaction improves the floor acceptability for general residential applications. The limitations ofthe different criteria given in the codes and guidelines for assessing floor vibrations in timberfloor structures are discussed and, also, the possible improvement of these criteria.

  • 21.
    Hassan, Osama
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Grundberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Dynamics of partially interacting composite beams2012In: Proceedings of the 15th European Conference on Composite Materials, 2012Conference paper (Refereed)
    Abstract [en]

    In this work, a combined variational calculus and experimental approach are used to characterize the structural vibration behaviour of layered composite beams. Experimental dynamic tests are carried out on a composite simply supported beam with varied interaction strength between the layers. From the results, the influence of connections on the flexural natural frequencies, flexural deformation and damping is investigated. A good agreement between the derived theoretical equations and experimental results is obtained.

  • 22.
    Hassan, Osama
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Schedin, Staffan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Girhammar, Ulf Arne
    Luleå University.
    Experimental Analysis of Composite Timbre-Concrete Wall Element2012In: Proceedings of the 15th European conference on composite materials, 2012Conference paper (Refereed)
    Abstract [en]

    The authors present an experimental and theoretical study on a composite or hybrid element used in residential and agricultural buildings. The composite wall element consists of timber studs connected to a concrete plate by means of nail plate shear connectors. Experimental results are presented and compared with an analytical model for partial composite action. A good agreement is obtained between the analytical and experimental results. Also, some suggestions to improve the design of the composite element are discussed.

  • 23. Källsner, Bo
    et al.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analysis of fully anchored light-frame timber shear walls: elastic model2009In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 42, no 3, 301-320 p.Article in journal (Refereed)
    Abstract [en]

    In order to stabilize light-framed timber buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with an elastic analysis model for fully anchored sheathed wood frame shear walls. The model is based on the assumption of a linear elastic load-slip relation for the sheathing-to-framing joints. Only static loads are considered. The basic structural behaviour and assumptions for the elastic model are elucidated. Formulas for the load-bearing capacity and the deformation of the shear walls in the ultimate and serviceability limit states, respectively, are derived. Both a discrete point description and a continuous flow per unit length modelling of the fasteners are discussed. Also, the forces and displacements of the fasteners and sheathing are derived. The effect of different patterns and spacing of the fasteners on the capacity and displacement of the wall is illustrated. The influence of flexible framing members and shear deformations in the sheets, and also the effect of vertical loads on the shear wall, both with respect to tilting and second order effects, on the horizontal load-bearing capacity and displacement are evaluated. The stress distribution and the reaction forces at the ends of the different framing members are derived. The elastic model is experimentally verified and an illustrative example is given.

  • 24. Källsner, Bo
    et al.
    Girhammar, Ulf Arne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Plastic models for analysis of fully anchored light-frame timber shear walls2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 9, 2171-2181 p.Article in journal (Refereed)
    Abstract [en]

    In order to stabilise timber-framed buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with plastic analysis models for fully anchored sheathed shear walls. The models are based on the assumption of plastic load-slip relations for the sheathing-to-framing joints. Only static loads are considered. The basic structural behaviour and assumptions for the plastic models are elucidated. Both upper and lower bound methods are applied. The load-bearing capacity and the deformation of the shear walls in the ultimate and serviceability limit states, respectively, are derived. Both a discrete point description and a continuous flow per unit length modelling of the fasteners are discussed. Also, the forces and displacements of the fasteners and sheathing are derived. The influence of flexible framing members and shear deformations in the sheets, and also the effect of vertical loads on the shear wall, both with respect to tilting and second order effects, on the horizontal load-bearing capacity and displacement are evaluated. The stress distribution and the reaction forces at the ends of the different framing members are derived. The elastic model is experimentally verified and an illustrative example is given. The main objective of this work is to contribute to a better understanding of the structural behaviour of these fully anchored walls and form the basis for establishing a new plastic design method for partially anchored shear walls, i.e. a design method capable of analysing the more practical conditions of no or partial anchorage of the studs and/or bottom rail in real structures.

1 - 24 of 24
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