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  • 1.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Civil and Environmental Engineering, Division of Structural Engineering, Chalmers University of Technology.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Influence of Grain Inclination Angle on Shear Buckling of Laminated Timber Sheathing Products2018In: Structures, ISSN 2352-0124, Vol. 13, p. 36-46Article in journal (Refereed)
    Abstract [en]

    Recent advances in timber production industries have enabled production of new innovative laminated timber products having layers with grain inclination angle. This paper is aimed to study influence of grain inclination angle in the laminated veneer lumber (LVL) and plywood sheathings on their shear buckling loads. Two extreme edge conditions of simply supported and clamped edges are considered. First, an accurate differential quadrature (DQ) computational code is developed using MAPLE programming software to obtain eigen buckling values and their corresponding eigen mode shapes. Next, for convenience of engineering calculations, approximate algebraic formulae are presented to predict critical shear buckling loads and mode shapes of LVL and plywood panels having layers with grain inclination angle, with adequate accuracy. Furthermore, finite element (FE) modelling is conducted for several cases using ANSYS software to show validity and accuracy of the predicted results for the problem. It is shown that the highest shear buckling loads of LVL sheathings is achievable when the inclination angle of about 30° with respect to the shorter edges is considered for production of LVL panels, whereas the same angle with respect to the long edges of the LVL sheathings results in a relatively lower buckling load. Considering similar inclination angle with respect to any edges of a plywood sheathings will also results in its highest pre-buckling capacity. It is also demonstrated that, under optimal design and certain loading circumstances, LVL shows a higher shear buckling capacity compared to a similar plywood sheathing.

  • 2.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    On the Shear Buckling of Clamped Narrow Rectangular Orthotropic Plates2015In: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, Vol. 2015, article id 569356Article in journal (Refereed)
    Abstract [en]

    This paper deals with stability analysis of clamped rectangular orthotropic thin plates subjected to uniformly distributed shear load around the edges. Due to the nature of this problem, it is impossible to present mathematically exact analytical solution for the governing differential equations. Consequently, all existing studies in the literature have been performed by means of different numerical approaches. Here, a closed-form approach is presented for simple and fast prediction of the critical buckling load of clamped narrow rectangular orthotropic thin plates. Next, a practical modification factor is proposed to extend the validity of the obtained results for a wide range of plate aspect ratios. To demonstrate the efficiency and reliability of the proposed closed-form formulas, an accurate computational code is developed based on the classical plate theory (CPT) by means of differential quadrature method (DQM) for comparison purposes. Moreover, several finite element (FE) simulations are performed via ANSYS software. It is shown that simplicity, high accuracy, and rapid prediction of the critical load for different values of the plate aspect ratio and for a wide range of effective geometric and mechanical parameters are the main advantages of the proposed closed-form formulas over other existing studies in the literature for the same problem.

  • 3.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Al-Emrani, Mohammad
    Chalmers tekniska högskola .
    Exact Lévy-type solutions for bending of thick laminated orthotropic plates based on 3-D elasticity and shear deformation theories2017In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 163, p. 129-151Article in journal (Refereed)
    Abstract [en]

    Exact solutions for static bending of symmetric laminated orthotropic plates with different Lévy-type boundary conditions are developed. The shear deformation plate theories of Mindlin-Reissner and Reddy as well as the three-dimensional elasticity theory are employed. Using the minimum total potential energy principle, governing equilibrium equations of laminated orthotropic plates and pertaining boundary conditions are derived. Closed-form Lévy-type solutions are obtained for the governing equations of both theories using separation of variables method and different types of classical boundary conditions, namely simply-supported, clamped and free edge, are exactly satisfied. Thereafter, 3-D elasto-static equations for orthotropic materials are solved for bending analysis of laminated plates using two different approaches. First, the method of separation of variables is utilized and an exact closed-from solution is achieved for simply-supported laminated orthotropic plates. Next, a combined Fourier-Differential Quadrature (DQ) approach is employed to present a semi-numerical solution for bending of laminated orthotropic plates with Lévy-type boundary conditions based on the three-dimensional elasticity theory. High accuracy of the presented solutions are proven and comprehensive comparative numerical results are provided and discussed. Presented comparative numerical results can serve as benchmark for investigating the correctness of new solution methods which may be established in the future.

  • 4.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Architecture and Civil Engineering, Division of Structural Engineering, Chalmers University of Technology.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Challamel, Noël
    Université de Bretagne Sud, UBS – Institut Dupuy de Lôme, Centre de Recherche.
    A weak shear web model for deflection analysis of deep composite box-type beams2018In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 155, p. 36-49Article in journal (Refereed)
    Abstract [en]

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

  • 5.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Challamel, Noël
    Université de Bretagne Sud, UBS – Institut Dupuy de Lôme, Centre de Recherche.
    Stability analysis of three-layer shear deformable partial composite columns2017In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 106-107, p. 213-228Article in journal (Refereed)
    Abstract [en]

    This paper is focused on the effect of imperfect bonding and partial composite interaction between the sub-elements of a box-type column on the critical buckling loads. The box column is modelled as a symmetric three-layer composite structure with interlayer slips at the interfaces, based on the Engesser-Timoshenko theory with uniform shear deformation assumptions. Linear shear springs or slip modulus is considered at the interfaces to model the partial interaction between the sub-elements of the structure. The minimum total potential energy principle is utilized to obtain governing equations and boundary conditions. A direct analytical solution of the original governing equations is presented for obtaining exact buckling characteristic equation of the three-layer partial composite column with different end conditions including clamped-pinned end conditions. Also, the coupled equations are recast into an efficient uncoupled form and shown that there is a strong similarity with those for the two layer element. It is shown that the obtained formulae are converted to the known Euler column formulae when the slip modulus approaches infinity (i.e. perfect bonding) and no shear deformations in the sub-elements are considered. A differential shear Engesser-Timoshenko partial composite model is also employed and critical buckling loads, obtained from an inverse solution method, are compared to examine the validity and accuracy level of the uniform shear model. Comprehensive dimensionless numerical results are presented and discussed

  • 6.
    Atashipour, Seyed Rasoul
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Challamel, Noël
    University of Europeenne Bretagne, Laboratory Genie Civil & Genie Mecan, Université Européenne de Bretagne, Mechanics Division, Department of Mathematics, University of Oslo, LIMATB, Université Européenne de Bretagne, University of South Brittany, Lorient.
    The effect of weak shear webs on the deformations of timber box type beams2015In: Proceedings of the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing / [ed] J. Kruis; Y. Tsompanakis; B.H.V. Topping, Stirlingshire: Civil-Comp Press , 2015, article id 259Conference paper (Refereed)
    Abstract [en]

    This paper deals with deflection analysis of a deep composite box beam due to inplane shear deformations, especially the modelling of the shear deformations in the webs is considered. The beam is composed of three framing members with sheathings on both sides. The sheathings or webs between the framing members are modelled as shear media with equivalent slip moduli corresponding to the partially composite beam model with three separated layers and two interlayer slip areas. The minimum total potential energy principle is employed to obtain the governing equilibrium equations and corresponding boundary conditions. The coupled set of governing equations is recast into an uncoupled form and solved explicitly together with the corresponding boundary conditions. The closed-form solutions obtained are compared to those based on the conventional beam theories. It is shown that the model is capable of predicting accurately the deflections for a wide range of geometry and property parameters, especially for small shear stiffness (slip modulus) values for the webs. The formula for the deflection is reduced to the Timoshenko formula for full composite interaction when the shear slip modulus of the web approaches infinity. Comparative numerical results are presented to show the influence of bending deformations, shear deformations in the framing layers and the in-plane shear deformations in the sheathings

  • 7.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Källsner, Bo
    School of Engineering, Linnæus University, Växjö, Linnéuniversitetet, Linnaeus University, Växjö.
    Analytical models for splitting capacity of bottom rails in partially anchored timber frame shear walls based on fracture mechanics2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 3, p. 165-188Article in journal (Refereed)
    Abstract [en]

    Plastic design methods can be used for determining the load-carrying capacity of partially anchored shear walls. For such walls, the leading stud is not fully anchored against uplift and tying down forces are developed in the sheathing-to-framing joints and the bottom rail will be subjected to crosswise bending, leading to possible splitting failure of the rail. In order to use these plastic design methods, a ductile behaviour of the sheathing-to-framing joints must be ensured. In two earlier experimental programmes, the splitting failure capacity of the bottom rail has been studied. Two brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the side surface of the bottom rail. In this article, a fracture mechanics approach for the two failure modes is used to evaluate the experimental results. The comparison shows a good agreement between the experimental and analytical results. The failure mode is largely dependent on the distance between the edge of the washer and the loaded edge of the bottom rail. The fracture mechanics models seem to capture the essential behaviour of the splitting modes and to include the decisive parameters. 

  • 8.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    School of Engineering, Linnæus University, Växjö, Linnéuniversitetet, Linnaeus University, Växjö.
    Comparison of models and tests on bottom rails in timber frame shear walls experiencing uplift2015In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 94, p. 148-163Article in journal (Refereed)
    Abstract [en]

    The authors present two different studies: one experimental study and one where analytical models developed to calculate the splitting failure capacity of bottom rails in partially anchored timber frame shear walls are evaluated and validated. The experimental study was divided into three parts with specimens matched to each other: (1) first the splitting capacity and failure mode of bottom rails subjected to uplift were studied; (2) then material properties such as tensile strength perpendicular to the grain; and (3) fracture energy were determined by testing specimens cut from the specimens belonging to study (1). The experimental results were compared with models based on a linear fracture mechanics approach presented earlier, using as input values results from (2) and (3). Almost all tested models show good agreement with the test results. The models showing the best agreement have been selected and proposed to be used as basis for calculation of the splitting failure capacity of bottom rails in partially anchored timber frame shear walls.

  • 9.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    Linnaeus University, Växjö.
    Splitting capacity of bottom rails in partially anchored timber frame shear walls with double-sided sheathing2015In: The IES Journal Part A: Civil & Structural Engineering, ISSN 1937-3260, E-ISSN 1937-3279, Vol. 8, no 1, p. 1-23Article in journal (Refereed)
    Abstract [en]

    In partially anchored shear walls, the leading stud is not fully anchored against the uplift; hence the uplifting force is resisted by the sheathing-to-framing joint along the bottom rail. These joint forces will introduce crosswise bending and shear in the bottom rail leading to possible splitting failures. To design partially anchored shear walls, plastic design methods can be used and, therefore, the bottom rails must not fail in a brittle manner. In this paper, results of two experimental programmes with respect to the splitting capacity of bottom rails with double-sided sheathing due to uplift in partially anchored shear walls are presented. This was evaluated varying the distance between the washer edge and the edge of the bottom rail, and the pith orientation of the bottom rail. The experimental results show two brittle failure modes for the bottom rail: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the edge surface of the bottom rail. The results indicate that the distance from the edge of the washer to the edges of the bottom rail has a decisive influence on the load-carrying capacity and failure modes of the bottom rail.

  • 10.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    Linnaeus University, Växjö.
    Johnsson, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Test on the splitting failure capacity of the bottom rail due to uplift in partially anchored shear walls2012In: World Conference on Timber Engineering: Final Papers - Architecture and Engineering Case Studies / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 189-194Conference paper (Other academic)
    Abstract [en]

    Källsner and Girhammar have developed a new plastic design method for wood-frame shear walls at ultimate limit state. The method is capable of calculating the load-carrying capacity of partially anchored shear walls, where the leading stud is not necessarily anchored against uplift. In fully anchored shear walls, the leading stud needs to be anchored using some kind of hold-downs to resist uplift and the bottom rail needs to be fixed by anchor bolts to resist horizontal shear forces. In partially anchored shear walls, where hold-downs are not provided, the uplifting force is resisted by the sheathing-to-framing joints along the bottom rail. Hence, it is important that the bottom rail is anchored to the floor structure or foundation by anchor bolts and, therefore, able to transmit the forces to the structure below. Because of the eccentric load transfer, transverse bending is developed in the bottom rail and splitting of the bottom rail can occur. In order to use the plastic design method, a ductile behaviour of the sheathing-to-framing joints must be ensured. In this paper, results of tests on the splitting capacity of the bottom rail due to uplift in partially anchored shear walls are presented. Specimens with single-sided sheathing were tested, varying the size of washer, pith orientation of the bottom rails and anchor bolt position along the width of the bottom rail. The aim of the tests was to evaluate the influence of these parameters in order to avoid splitting failure of the bottom rail. Two types of brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the edge surface of the bottom rail along the line of sheathing-to-framing joints. These failure modes were mainly dependent on the washer size and the location of the anchor bolt. The results show that the distance between the edge of the washer and the loaded edge of the bottom rail has a decisive influence on the maximum load and the failure modes of the bottom rail.

  • 11.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    School of Engineering, Linnæus University, Växjö.
    Lidelöw, Helena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Splitting Capacity of Bottom Rail in Partially Anchored Timber Frame Shear Walls with Single-Sided Sheathing2014In: The IES Journal Part A: Civil & Structural Engineering, ISSN 1937-3260, E-ISSN 1937-3279, Vol. 7, no 2, p. 83-105Article in journal (Refereed)
    Abstract [en]

    Plastic design methods can be used for determining the load-carrying capacity of partially anchored shear walls, where hold-downs are not provided. In order to use these methods, a ductile behaviour of the sheathing-to-framing joints must be ensured. Since the forces in the anchor bolts and the sheathing-to-framing joints do not act in the same vertical plane, the bottom rail will be subjected to bending and shear in the cross-wise direction, and splitting of the bottom rail may occur. In this article, results of two experimental programmes on the splitting capacity of the bottom rail due to uplift in partially anchored shear walls are presented. Two brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the edge surface of the bottom rail along the line of the sheathing-to-framing joints. The results show that the distance between the edge of the washer and the loaded edge of the bottom rail has a decisive influence on the maximum load and the failure modes of the bottom rail.

  • 12.
    Caprolu, Giuseppe
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    Linnaeus University, Växjö.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Vessby, Johan
    Linnaeus University, Växjö.
    Analytical and experimental evaluation of the capacity of the bottom rail in partially anchored timber shear walls2012In: World Conference on Timber Engineering: Final Papers - Architecture and Engineering Case Studies / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 157-166Conference paper (Other academic)
    Abstract [en]

    Källsner and Girhammar have developed plastic design methods for light-frame timber shear walls that can be used for determining the load-carrying capacity when the shear walls are partially anchored. For such walls, the leading stud is not fully anchored against uplift and tying down forces are developed in the sheathing-to-framing joints. Since the forces in the anchor bolts and the sheathing-to-framing joints do not act in the same vertical plane, the bottom rail will be subjected to cross-wise bending, leading to possible splitting along the bottom side of the rail. Another possible brittle failure mode is splitting along the edge of the bottom rail in line with the sheathing-to-framing fasteners. An experimental program has been conducted using different anchor bolt locations, washer sizes and pith orientations. A fracture mechanics approach for the two failure modes is used to evaluate the experimental results. The comparison shows a good agreement between the experimental and analytical results. The failure mode is largely dependent on the distance between the edge of the washer and the edge of the bottom rail. The size of the washer seems also to have some influence on the failure load. The fracture mechanics models seem to capture the essential behaviour of the splitting modes and to include the decisive parameters. These parameters can easily be adjusted to experimental results and be used in design equations for bottom rails in partially anchored shear walls.

  • 13.
    Challamel, Noel
    et al.
    University of Europeenne Bretagne, Laboratory Genie Civil & Genie Mecan.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Boundary-Layer effect in composite beams with interlayer slip2011In: Journal of Aerospace Engineering, ISSN 0893-1321, E-ISSN 1943-5525, Vol. 24, no 2, p. 199-209Article 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.

  • 14.
    Challamel, Noël
    et al.
    Mechanics Division, Department of Mathematics, University of Oslo.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lateral-torsional buckling of partially composite horizontally layered or sandwich-type beams under uniform moment2013In: Journal of engineering mechanics, ISSN 0733-9399, E-ISSN 1943-7889, Vol. 139, no 8, p. 1047-1064Article in journal (Refereed)
    Abstract [en]

    This paper is devoted to the analytical and numerical modeling of the lateral-torsional stability of horizontally layered composite beams. Composite beams are classified as horizontally layered beams with interlayer slip or sandwich beams with a weak shear core. The governing differential equations of the out-of-plane behavior of horizontally layered composite beams are supported by variational arguments. In the theoretical analysis, a distinction is made between the influence of the shear connection at the interface with respect to the in-plane or transversal deformations and to the out-of-plane or lateral deformations, respectively. Some engineering results are presented for a partially composite beam under pure bending moment. In the case of noncomposite in-plane action (orthotropic connection), a simple closed-form solution is derived for the lateral-torsional buckling moment, and it is shown that the exact dimensionless buckling moment depends only on two structural parameters for beams composed of two identical subelements. The results are analogous to those obtained for the in-plane buckling of partially composite or sandwich-type beams, where the buckling moment increases with the stiffness of the shear connection. Prandtl’s valid solution for lateral-torsional buckling of ordinary beams is also found for composite beams in the case of noncomposite action in both the transversal and lateral directions. A generalization of Prandtl’s valid solution for composite beams with partial composite action in the lateral direction and noncomposite action in the transversal direction is derived. It is shown that the lateral-torsional buckling formulas are strongly affected by the kinematics of the connected shear layer. Also, the lateral-torsional buckling of partially composite beams with both in-plane and out-of-plane slip behavior is analyzed using the Rayleigh-Ritz method. This mathematical problem leads to a system of differential equations with nonuniform coefficients. An approximated solution is derived for the isotropic connection with isotropic noncomposite actions, whereas an exact solution is presented for the orthotropic connection with noncomposite in-plane action. Finally, the Rayleigh-Ritz approach is compared with some numerical results associated with the exact resolution of the differential equations with nonuniform coefficients. The Rayleigh-Ritz approach appears to be efficient to capture the main phenomena, including the nonmonotonic dependence of the buckling load to the connection parameter.Read More: http://ascelibrary.org/doi/abs/10.1061/(ASCE)EM.1943-7889.0000489

  • 15.
    Challamel, Noël
    et al.
    Université Européenne de Bretagne.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lateral-torsional buckling of vertically layered composite beams with interlayer slip under uniform moment2012In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 34, p. 505-513Article in journal (Refereed)
    Abstract [en]

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

  • 16.
    Challamel, Noël
    et al.
    University of Europeenne Bretagne, Laboratory Genie Civil & Genie Mecan.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Variationally-based theories for buckling of partial composite beam-columns including shear and axial effects2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 8, p. 2297-2319Article in journal (Refereed)
    Abstract [en]

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

  • 17.
    Crocetti, Roberto
    et al.
    Division of Structural Engineering, Lund University.
    Gustafsson, Per Johan
    Department of Building Sciences, Lund Institute of Technology.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Costa, L.
    Structural Engineer, Aurecon Group.
    Asimakidis, A.
    Stuctural Engineer, Sydark Konstruera, Malmö.
    Nailed Steel Plate Connections: Strength and Ductile Failure Modes2016In: Structures, ISSN 2352-0124, Vol. 8, no 1, p. 44-52Article in journal (Refereed)
    Abstract [en]

    This paper deals with theoretical and experimental investigations of nailed steel plate connections. For the experimental part, a total of 99 laboratory tests have been carried out in order to study failure mechanism and shear capacity of nailed steel plate connections. The testing programme comprised two nail lengths, two steel plate thicknesses and five nailing patterns. All tests related to loading of the plate in the direction of the grain of the wood. The nail patterns were designed to give ductile joint failure by yielding of the nails and/or bearing failure of the wood. The failure load was recorded and the mode and course of failure noted. For some of the specimens, deformation of the nails during loading was studied by means of an X-ray equipment.Deviations between the test results and contemporary consensus as manifested in the SS-EN 1995-1-1:2004 and the Johansen theory for ductile failure were found in several respects: development of the plastic hinges in the nails, influence of nail length, steel plate thickness and nail-to-nail and edge distances.The paper also presents an empirical equation based on multiple regression analysis of the test results was proposed as an attempt to predict the load-carrying capacity of nailed connections in shear.

  • 18.
    Daerga, Per-Anders
    et al.
    f.d. Umeå universitet.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Programmering av Matlab-rutiner för utvärdering av experiment med knutpunktsförband i MFB-systemet: Beröringsfri mätning av krafter och deformationer med Qualisys Motion Capture – Beskrivning av mätsystem och efterbehandling av mätdata2017Report (Other (popular science, discussion, etc.))
  • 19.
    Daerga, Per-Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    Linnéuniversitetet.
    Masonite flexible buildning system for multistorey timber buildnings2012In: World Conference on Timber Engineering, WCTE: final papers / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 426-431Conference 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 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 Ibeams 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-towallload 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.

  • 20.
    Daerga, Per-Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    Linnéuniversitetet.
    Slotted-in steel-plate connections for panel wall elements: experimental and analytical study2012In: World Conference on Timber Engineering: Final Papers - Architecture and Engineering Case Studies / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 451-460Conference paper (Refereed)
    Abstract [en]

    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.

  • 21.
    Daerga, Per-Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, Bo
    Linnéuniversitetet.
    Suspended floor element connections for the masonite flexible building system2012In: World Conference on Timber Engineering: Final Papers - Timber Engineering Challenges and Solutions / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 465-472Conference paper (Refereed)
    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

  • 22.
    Girhammar, Ulf Arne
    Department of TFE-Civil Engineering, Faculty of Science and Technology, Umeå University.
    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, p. 515-530Article 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) with the effective (partially) composite bending stiffness (EIeff) 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

  • 23.
    Girhammar, Ulf Arne
    Department of TFE-Civil Engineering, Faculty of Science and Technology, Umeå University.
    Composite beam-columns with interlayer slip-Approximate analysis2008In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 50, no 12, p. 1636-1649Article 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.

  • 24.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Deformationskapacitet hos balk-pelarinfästningar vid linbärverkan och skadetålighet hos dynamiskt överpåverkande konstruktioner1979Report (Other academic)
  • 25.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Dynamic deformations of elasto-plastic two-span beams subjected to loss of interior support: a comparative study of different calculation methods1978Report (Other academic)
  • 26.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Dynamic fail-safe behaviour of steel structures1980Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The fundamental behaviour and the capacity of steel structures subjected to loss of interior load-bearing elements are studied. The ultimate load-bearing and deformation capacity of certain beam-to-column connections and the dynamic fail-safe behaviour of some ordinary steel structures are investigated in detail. A number of different geometrical models of steel structures in the area of primary damage are analysed. Both bending and catenary action of the models are treated and the strength properties of both members and connections are considered. Two types of connections are investigated, viz. the "bolted heel connection" and the bolted end-plate connection (with a degree of moment rigidity of 25%). No stability problems are treated. A rigid-body method of analysis is applied. Design methods for the bolted heel and bolted end-plate connections under catenary action are proposed, which safely predict the over-all behaviour and the ultimate load-bearing and deformation capacity of each connection. For structures having these two types of connections, the static damage endurance capacity under catenary action is approximately equal. The applicability and accuracy of the riqid-body method is evaluated. The accuracy is determined by comparison with an elasto-plastic vibration theory and an equivalent mass-spring method. The rigid-body model proves to be a suitable model in order to determine the failsafe behaviour of most steel structures. The ultimate dynamic load-bearing capacity under bending action regarding member characteristics and under catenary action regarding partly member characteristics and partly joint characteristics is evaluated in great detail. It is found that the dynamic capacity under bending action approximately equals the static one provided that the greater deformations obtained under dynamic conditions can be absorbed. No regard to the time of removal of the load-bearing element is thus necessary if only the deformation capacity of the structure is verified. Also, strain-hardening effects and geometrical non-linearity need not be considered. The dynamic capacity under catenary action regarding member characteristics is only half of the static one, and regarding joint characteristics only one third of the static one for structures with bolted heel connections, and half of the static one for structures with bolted end-plate connections. The high efficiency of catenary action compared to bending action found under static conditions, is reduced considerably under dynamic conditions. For many practical cases only full end constraints, momentary loss of load-bearing elements and geometrical linearity need to be considered. The maximum column reactions at ultimate dynamic load always fall below the maximum reactions at ultimate static load. Deflections and reactions determined theoretically from the rigid-body models employed agree well with those measured.

  • 27.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Dynamisk överpåverkan på stålkonstruktioner: en problemöversikt1976Report (Other academic)
  • 28.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    General dynamic analysis of elasto-plastic structures with stationary plastic hinges1978Report (Other academic)
  • 29.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    On the boundary and matching conditions for dynamic beam element systems1978Report (Other academic)
  • 30.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Rabo - väggelement1980Report (Other academic)
  • 31.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Samverkanskonstruktioner i trä1983Report (Other academic)
  • 32.
    Girhammar, Ulf Arne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ultimate capacity of beam-column connections in damaged steel structures1987In: Proceedings of the International Conference on Steel and Aluminium Structures: Composite steel structures : advances, design and construction ; [proceedings of the International Conference on Steel and Aluminium Structures, Cardiff, UK, 8 - 10 July 1987] / [ed] R. Narayanan, London: Elsevier, 1987, p. 835-844Conference paper (Refereed)
    Abstract [en]

    An experimental study is presented of the ultimate force-deformation capacity of two types of beam-column connections commonly used in Sweden. The behaviour of the structural joints was investigated for damaged steel structures (due to a column collapse), which are capable of developing catenary action. For each type of connection, the idealized overall behaviour and ultimate capacity of the joint are discussed.

  • 33.
    Girhammar, Ulf Arne
    et al.
    Royal Swedish Fortifications Administration, Res. Dept.
    Andersson, Håkan E.
    Royal Inst. of Tech., Dept. of Steel Construction.
    Effect of loading rate on nailed timber joint capacity1988In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 114, no 11, p. 2439-2456Article in journal (Refereed)
    Abstract [en]

    The present study addresses the loading or deformation rate effect on the yield loads of nailed timber joints. Four different types of joints, which differed with respect to the thickness of the members and the angle of load to grain, were tested. The bearing strength of the wood and the bending strength of the nails were also tested in order to analytically verify the dynamic ultimate capacity of the joints. All tests were run with deformation rates from static loading values up to approximately 1 m/s (40 in./s). The pilot study results show that the strength of the nailed joints can be expressed in terms of the deformation rate. A logarithmic expression for the strength of the joints was obtained from regression analysis of approximately 200 results. The values obtained analytically agreed well with the experimental ones for the various joints tested

  • 34.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Atashipour, Seyed Rasoul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    A study on shear deformations of deep composite box-Type beams used in timber building structures2013In: Proceedings of the Fourteenth International Conference on Civil, Structural and Environmental Engineering Computing, 3-6 September 2013, Cagliari, Sardinia, Italy / [ed] Barry H.V. Topping; Peter Ivaniy, Stirlingshire: Civil-Comp Press , 2013Conference paper (Refereed)
    Abstract [en]

    The higher-order shear deformation beam theory of Reddy-Bickford predicts accurately the shear deflection without the need of a shear correction factor. However, for more complicated cross-sections, e.g. including holes, it is shown that this theory is not adequate. To be able to predict accurately the shear deflections of deep composite box-type cross-sectional beams, a simple engineering approach is used to derive a closed-form expression for the shear correction factor for those types of beams. The high accuracy and reliability of the developed procedure is demonstrated by comparing those results with accurate three-dimensional finite element results and with Timoshenko and Reddy-Bickford theories. A comprehensive parametric study is presented to investigate the effects of various mechanical properties and geometric dimensions of the box-type of beams for the various models. There is very good agreement between the proposed engineering method and the three-dimensional finite element model

  • 35.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Atashipour, Seyed Rasoul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Analysis of shear deflections of deep composite box-type of beams using different shear deformation models2015In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 155, p. 42-53Article in journal (Refereed)
    Abstract [en]

    The deflection of deep box-type elements due to shear deformations is treated. A closed-form expression for the shear correction factor is derived by using an energy approach. The high accuracy and reliability of the developed procedure is demonstrated by comparing its results with accurate 3-D finite element results and also with the results of the conventional theories of Timoshenko with constant shear coefficient and of Reddy–Bickford applied to this kind of cross-section. A comprehensive and comparative parametric study is presented to investigate the effects of various mechanical properties and geometric dimensions for the different models. Unlike the higher-order shear deformation theories, which are accurate only for beams with rectangular cross-sections, there is a very good agreement between the results of the proposed method and the 3-D FE model. Clearly, the proposed energy method is applicable to more complicated cross-sections, including those with abrupt changes in the geometry, e.g. due to holes.

  • 36.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Daerga, Per-Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Källsner, B.
    Linnéuniversitetet.
    Recommendations for design of anchoring devices for bottom rails in partially anchored timber frame shear walls2011In: 11th World Conference on Timber Engineering 2010, WCTE 2010, Red Hook: Curran Associates, Inc., 2011, Vol. 2, p. 1218-1227Conference paper (Refereed)
    Abstract [en]

    The authors have developed a new plastic design method for light-frame timber shear walls. The method is capable of analyzing the load-bearing capacity of partially anchored shear walls. For proper application of the plastic method it is necessary to ensure ductile behaviour of the sheathing-to-framing joints and to avoid brittle failure of the bottom rail in particular. In a partially anchored shear wall the leading stud is not fully anchored against uplift and corresponding tying down forces are developed in the sheathing-to-framing joints along the bottom rail in the sheathing segments close to the leading stud. These tying down forces in the joints may introduce a number of possible brittle failure modes or serviceability problems for the bottom rail that need to be eliminated or restricted in order for the plastic method to be applicable. This paper describes experimental results for proper design of washers or bearing plates for the anchor bolts in order to avoid splitting failure of and excessive washer indentation into the bottom rail. Specimens with both double and single sided sheathing and different locations of anchor bolts are studied. With respect to splitting of the bottom rail, the tests indicate that the failure load depends on the distance from the edge of the washer to the loaded edge of the bottom rail. With respect to large deformations due to bearing stresses of the washers of the anchoring bolts, the size of the washer is the most important parameter. The test results indicate that the bearing strength for large washers is lower than that proposed by Eurocode 5. In this paper, it is therefore proposed to make the bearing strength inverse proportional to the diameter or side length of the washer. Then, good agreement with the test results was found. The results show that failure due to splitting is the determining design mode.

  • 37.
    Girhammar, Ulf Arne
    et al.
    Swedish University of Agricultural Sciences.
    Gopu, Vijaya K. A
    Department of Civil Engineering, Louisiana State University, Baton Rouge, LA .
    Composite Beam-Columns with Interlayer Slip: Exact Analysis1993In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 119, no 4, p. 1265-1282Article in journal (Refereed)
    Abstract [en]

    Exact first- and second-order analyses for composite beam-columns with partial interaction and subjected to transverse and axial loading are presented. General closed-form solutions for the displacement functions and the various actions in the composite element are presented for the first- and second-order cases. In this paper, the axial loads acting on the composite elements are assumed to be proportioned in accordance with their relative axial stiffnesses so that their resultant acts at the centroid of the transformed cross-sectional area of the fully composite member. Resultant axial loads active at the centroid ensure that, in the first-order analysis, the composite elements are subjected to uniform axial strain through the depth of the member and that no bending is induced by the resultant axial load. The analysis procedures are applied to simply supported beam-columns subjected to an axial force and a uniformly distributed transverse load to obtain closed-form solutions for the internal actions and displacements. The difference in the first- and second-order analysis approaches is illustrated by applying the solutions to a given beam-column problem.

  • 38.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Gopu, Viljayak A.
    Luleå tekniska universitet.
    Analysis of the P-d effect in composite beam-columns of timber and concrete1986Report (Other academic)
  • 39.
    Girhammar, Ulf Arne
    et al.
    Royal Inst of Technology, Stockholm.
    Gopu, V.K.A.
    Royal Inst of Technology, Stockholm.
    Analysis of P-Δ effect in composite concrete/timber beam-columns1991In: Proceedings - Institution of Civil Engineers, ISSN 0307-8361, Vol. 92, no 2, p. 39-54Article in journal (Refereed)
    Abstract [en]

    The procedure for analysing composite beam-columns of timber and concrete is developed. The influence of the interlayer slip is considered in the theoretical development. Closed form solutions for the internal axial forces and moments, which act on the timber and concrete components, and the slip forces are presented for the first-order (elementary) and the second-order (P-Δ) cases. Approximate formulae for determining the magnification factors to be applied to the internal actions computed in the elementary case in order to account for the P-Δ effect are recommended for simply supported members. A comparison is made between the results obtained from the application of the approximate formulae and the second-order analysis approach for the case of a practical beam-column to illustrate the applicability of the approximate formulae in design situations.

  • 40.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Gustafsson, Per Johan
    Division of Structural Mechanics, Department of Building Sciences, Lund University.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Modeling of shear walls using finite shear connector elements based on continuum plasticity2017In: Frontiers of Structural and Civil Engineering, ISSN 2095-2430, E-ISSN 2095-2449, Vol. 11, no 2, p. 143-157Article in journal (Refereed)
    Abstract [en]

    Light-frame timber buildings are often stabilized against lateral loads by using diaphragm action of roofs, floors and walls. The mechanical behavior of the sheathing-to-framing joints has a significant impact on the structural performance of shear walls. Most sheathing-to-framing joints show nonlinear load-displacement characteristics with plastic behavior. This paper is focused on the finite element modeling of shear walls. The purpose is to present a new shear connector element based on the theory of continuum plasticity. The incremental load-displacement relationship is derived based on the elastic-plastic stiffness tensor including the elastic stiffness tensor, the plastic modulus, a function representing the yield criterion and a hardening rule, and function representing the plastic potential. The plastic properties are determined from experimental results obtained from testing actual connections. Load-displacement curves for shear walls are calculated using the shear connector model and they are compared with experimental and other computational results. Also, the ultimate horizontal load-carrying capacity is compared to results obtained by an analytical plastic design method. Good agreements are found.

  • 41.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Gustafsson, P.J.
    Department of Building Sciences, Lund Institute of Technology.
    Källlsner, Bo
    School of Engineering, Linnæus University, Växjö.
    Finite element modelling of shear walls using connector shear elements based on continuum plasticity2010In: Proceedings of the Tenth International Conference on Computational Structures Technology: Valencia, Spain, 14 - 17 September 2010, Klippen: Civil-Comp Press , 2010Conference paper (Refereed)
    Abstract [en]

    Light-frame timber buildings are often stabilised against lateral loads by using diaphragm action of roofs, floors and walls. The mechanical behaviour of the sheathing-to-timber joints has a significant impact on the structural performance of shear walls. Most sheathing-to-framing joints show non-linear load-displacement characteristics with plastic behaviour. This paper is focused on the finite element modelling of shear walls. The purpose is to present a new connector shear element based on the theory of continuum plasticity. The incremental load-displacement relationship is derived based on the elastic-plastic stiffness tensor including the elastic stiffness tensor, the plastic modulus, a function representing the yield criterion and a hardening rule, and another function representing the plastic potential. The plastic properties are determined from experimental results obtained from testing actual connections. Load-displacement curves for shear walls are calculated using the connector shear model and they are compared with experimental and other computational results. Also, the ultimate horizontal loadcarrying capacity is compared to results obtained by an analytical plastic design method. Good agreements are found

  • 42.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Jacquier, Nicolas
    Byggtekniska Byrån.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Stiffness model for inclined screws in shear-tension mode in timber-to-timber joints2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 136, p. 580-595Article in journal (Refereed)
    Abstract [en]

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

  • 43.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Juto, Henrik
    Provning av tvärböjning och spjälkning av syllen i partiellt förankrade skiv-regelväggar2014Report (Other academic)
  • 44.
    Girhammar, Ulf Arne
    et al.
    Department of TFE - Civil Engineering, Faculty of Science and Technology, Umeå University.
    Källsner, Bo
    School of Technology and Design, Växjö University.
    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, p. 321-337Article 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.

  • 45.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Källsner, Bo
    School of Engineering, Linnæus University, Växjö, Linnéuniversitetet, Linnaeus University, Växjö.
    Design against brittle failure of bottom rails in shear walls2016In: Proceedings of the Institution of Civil Engineers: Structures and buildings, ISSN 0965-0911, E-ISSN 1751-7702, Vol. 169, no 10, p. 782-793Article in journal (Refereed)
    Abstract [en]

    The authors have developed a new plastic design method for light-framed timber shear walls, which is capable ofanalysing the load-bearing capacity of partially anchored shear walls. For proper application of the plastic method it isnecessary to ensure ductile behaviour of the sheathing-to-framing joints and to avoid brittle failure of the bottomrail. In a partially anchored shear wall, the tying down forces are developed in the sheathing-to-framing joints alongthe bottom rail, which may introduce a brittle type of failure of the bottom rail that needs to be eliminated in orderfor the plastic method to be applicable. This paper deals with design of anchor bolts needed to tie down the bottomrail properly and it describes experimental results for proper design of washers for anchor bolts to avoid thesesplitting failures of the bottom rail. The effect of different washer sizes and location of the anchor bolts on the failureload when splitting of the bottom rail occurs is presented. The tests indicate that the failure load depends on thedistance from the edge of the washer to the loaded edge of the bottom rail. An explicit design equation for thecapacity of the bottom rail is presented.

  • 46.
    Girhammar, Ulf Arne
    et al.
    Umeå University.
    Källsner, Bo
    Växjö University.
    Effect of transverse walls on capacity of wood-framed wall diaphragms without tie-downs2008Conference paper (Refereed)
    Abstract [en]

    The structural behavior of a wood-framed wall diaphragm is to a large extent dependent on the 3-dimensional behavior of the whole building. In this connection the influence of transverse walls is an issue of special interest. A plastic design method capable of analyzing the behavior and capacity of partially anchored wood-framed wall diaphragms has been presented in earlier papers. In this paper, the plastic model is applied to the case where a wall diaphragm is connected to a transverse wall. The paper describes the theoretical analysis and the experimental results for sheathed wood-framed transverse walls of different geometrical configurations and with different boundary conditions. Transverse walls are studied by varying the number of sheet segments and the horizontal fixing of the top rail. The effect of the tying-down action of transverse walls on the vertical uplift is studied and the horizontal load-carrying capacity of wall diaphragms is analyzed.

  • 47.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Department of TFE-Civil Engineering, Faculty of Science and Technology, Umeå University.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Elasto-plastic model for analysis of influence of imperfections on stiffness of fully anchored light-frame timber shear walls2009In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 31, no 9, p. 2182-2193Article in journal (Refereed)
    Abstract [en]

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

  • 48.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods – Introducing a Handbook: Part 1: Design Principles for Horizontal Stabilisation2016In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 161, p. 618-627Article in journal (Refereed)
    Abstract [en]

    The authors have developed a plastic design method for sheathed timber frame shear walls. It has been presented and discussed for inclusion in Eurocode 5 and a Swedish handbook has been presented. In the plastic method, you can choose to transfer the anchoring force via the leading stud to the substrate, corresponding to a fully anchored shear wall (no uplift of studs), but you can also choose to utilize the sheathings to transfer the tensile force via the sheathing-to-framing joints to the substrate by anchoring the bottom rail, corresponding to a partially anchored shear wall (studs experience uplift). By the plastic method several alternatives for anchoring the wall are possible and they can also be combined in such a way that each of them take a portion of the uplifting force, e.g. through a simple tying down device, through the sheathing-to-framing joints and through anchoring of the shear wall to the transverse wall. The method also makes it possible to include the load-bearing capacity of wall segments including openings. The handbook treats primarily shear walls, but for the sake of completeness some aspects of the roof and floor diaphragms are also discussed. The interior force distribution in sheathed timber frame walls weak in shear is discussed, as are the fundamental difference between the effect of vertical loads on the stabilisation of walls which are rigid or weak in shear, and how the plastic design method is applied to multi-storey timber buildings

  • 49.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods – Introducing a Handbook: Part 2: Design of Joints and Anchoring Devices2016In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 161, p. 628-635Article in journal (Refereed)
    Abstract [en]

    In this part 2, the practical design and strength of a number of different joints is described: (1) Sheathing-to-framing joints – the plastic design method is based on the premise that the load-displacement relationship of the sheathing-to-framing joints has sufficiently large plastic deformation capacity; the sheathing-to-framing joints have great influence on the load-carrying capacity of the wall; (2) Stud-to-rail joints – by utilizing the shear capacity of the stud-to-rail joints, the plastic design method can be simplified and the load-carrying capacity can be increased; (3) Hold down devices for the (leading) stud – the capacity of the tying down force of the hold down determines whether the shear wall will act as fully or partially anchored; tying down the shear walls by connecting them to the transverse walls leads to a 3-dimensioonal behaviour that is a very favourable for the load-carrying capacity and the stiffness of the shear wall; through transverse walls the anchoring of the leading stud can be reduced or eliminated (those types of transverse wall connections are not discussed in detail in this paper); and (4) Anchoring devices for the bottom rail – in partially anchored shear walls it is necessary that the bottom rail is anchored to the substrate against uplift. Characteristic values for the different types of joints are given. Also, joints between the panels in the walls, roofs and floors are described briefly.

  • 50.
    Girhammar, Ulf Arne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Källsner, Bo
    Department of Building Technology, Linnaeus University.
    Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods – Introducing a Handbook: Part 3: Basics of the Plastic Design Method2016In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 161, p. 636-644Article in journal (Refereed)
    Abstract [en]

    Design of shear walls has been a topic of major discussions to develop a common European code for design of timber structures. The main problem has been that shear walls are fastened to the substrate in different ways in different countries and that this fact must be reflected in the code. In this part the requirements are given that must be met for the ductile characteristics of the sheathing-to-framing joints in order for the plastic design method to be applicable. The method is based on the plastic lower bound theory. The fundamental prerequisites for the method are that the static equilibrium for the structure is fulfilled and that the sheathing-to-framing joints are ductile. What requirements that should be made on the mechanical properties of the joints for the plastic design methods to be applicable and the precaution measures to take to avoid brittle behaviour are discussed. The two main principles for anchoring of sheathed timber frame shear walls, fully and partially anchored, are illustrated showing the static behaviour of the walls and the force distribution in the framing members and the sheathings. In addition, a general description of the design in the serviceability limit state is given. For medium-rise and taller buildings the serviceability limit state needs to be taken into account. There are no specified criteria for deformations in the present code.

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