Rolling shear: Test configurations and properties of some European soft- and hardwood species

Ehrhart, Thomas; Brandner, Reinhard

doi:10.1016/j.engstruct.2018.05.118

Cited by 81 publications

(58 citation statements)

References 18 publications

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“…For these boards, the equivalent cross layer shear stiffness modulus lies between 100 and 150 MPa approximately which is twice to three times higher than the local rolling shear stiffness modulus G RT . Hence, the present closed-form bounds confirm previous observations obtained from experiments as well as numerical simulations (Aicher and Dill-Langer, 2000;Jakobs, 2005;Perret et al, 2018;Ehrhart and Brandner, 2018).…”

Section: Equivalent Cross-layer Shear Stiffness Modulus G C Zsupporting

confidence: 91%

“…Indeed, because of the stiffness contrast between the longitudinal layers and the cross layers it is possible to argue that the cross layer is mostly sheared by the longitudinal layers (Lebée and Sab, 2012a). Hence in practice the equivalent cross layer shear modulus is mostly determined experimentally from single lap shear tests (Ehrhart et al, 2015;Ehrhart and Brandner, 2018) where narrow edges are free. Following this global picture, a numerical finite elements study is achieved in order to compute an upper bound of the equivalent cross-layer shear stiffness modulus G C Z with glued and free narrow edges.…”

Section: Numerical Upper Bounds For the Cross-layer Shear Stiffness Mmentioning

confidence: 99%

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Equivalent stiffness of timber used in CLT: closed-form estimates and numerical validation

et al. 2019

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In this paper, a closed-form approach is presented to estimate rapidly the equivalent stiffness of boards used in Cross Laminated Timber (CLT) panels from local orthotropic behavior at ring scale for varying sawing patterns.It is first assumed that narrow edges are glued. In this case, closed-form Reuss and Voigt bounds are derived for the equivalent layer behavior of CLT. An application to Norway spruce boards is presented and reveals that the cross-layer (rolling) shear behavior lies between 100 and 150 MPa with a careful selection of the board sawing pattern. Then, using finite element method, upper bounds for the cross-layer shear stiffness modulus of boards with and without glued edges are calculated and theoretical predictions are compared with recommendations and experimental data from the literature.Finally, it appears that these bounds remain relevant for CLT layer with unglued narrow edges for common aspect ratios.

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Section: Equivalent Cross-layer Shear Stiffness Modulus G C Zsupporting

confidence: 91%

Section: Numerical Upper Bounds For the Cross-layer Shear Stiffness Mmentioning

confidence: 99%

Equivalent stiffness of timber used in CLT: closed-form estimates and numerical validation

et al. 2019

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“…Recently, experimental tests and numerical models have also been presented in Franzoni et al [10], in which the influence of large and small gaps between lateral boards (lamellas) on mechanical behavior of CLT panels subjected to vertical loads with respect to its mid-plane has been highlighted, while experimental measurements of rolling shear properties on soft and hardwood species were carried out by Zhou et al [11] and O' Ceallaigh et al [5]. An extensive experimental campaign (consisting of 342 tests), aimed to evaluate the rolling shear properties of six timber species, with three different sawing patterns and three different aspect ratios of specimens, has been conducted by Ehahart and Brandner [12].…”

Section: Rolling Shear Phenomenonmentioning

confidence: 99%

The Rolling Shear Influence on the Out-of-Plane Behavior of CLT Panels: A Comparative Analysis

Sandoli

Calderoni

2020

Buildings

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This paper deals with the influence of the rolling shear deformation on the flexural behavior of CLT (Cross-Laminated Timber) panels. The morphological configuration of the panels, which consist of orthogonal overlapped layers of boards, led to a particular shear behavior when subjected to out-of-plane loadings: the low value of the shear modulus in orthogonal to grain direction (i.e., rolling shear modulus) gives rise to significant shear deformations in the transverse layers of boards, whose grains direction is perpendicular with respect to the tangential stresses direction. This produces increases of deflections and vibrations under service loads, creating discomfort for the users. Different analytical methods accounting for this phenomenon have been already developed and presented in literature. Comparative analyses among the results provided by some of these methods have been carried out in the present paper and the influence of the rolling shear deformations, with reference to different span-to-depth (L/H) ratios investigated. Moreover, the analytical results have also been compared with those obtained by more accurate 2D finite element models. The results show that, at the service limit states, the influence of the rolling shear can be significant when the aspect ratios became less than L/H = 30, and the phenomenon must be accurately considered in both deflection and stress analysis of CLT floors. Contrariwise, in the case of higher aspect ratios (slender panels), the deflections and stresses can be evaluated neglecting the rolling shear influence, assuming the layers of boards as fully-connected.

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“…From their tests, they then calculate the shear creep of the cross-layer in order to extend their results to all CLT configurations. Their interpretation is however questionnable as the proper identification of the shear stiffness at layer scale is still under debate because its indirect measurement is extremely sensitive to the accuracy of the bending stiffness estimation in CLT panels [19,20]. Consequently, additional experimental data seems necessary to characterize directly the longitudinal-layer shear creep factor def,0−90 and the cross-layer shear creep factor def,90−90 .…”

Section: On the Influence Of Creepmentioning

confidence: 99%

“…Hence, the expression of the long term deflections of an imperfect beam ∞ (43) is similar to that of the short term deflection (20) and can be obtained by simply replacing the short term critical load cr,0 by the long term critical load cr,∞ (41). As a consequence, the long term normal strength criterion can be adapted from the short term criterion (27) by replacing the short term buckling load cr,0 by the long term critical load cr,∞ and considering long term elastic characteristics following the same approach :…”

Section: Long Term Buckling Of a Shear Weak Imperfect Columnmentioning

confidence: 99%

A shear strength criterion for the buckling analysis of CLT walls

Perret

Douthe

Lebée

et al. 2020

Engineering Structures

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The proper sizing of Cross Laminated Timber (CLT) walls for the construction of high rise buildings requires to take into account their low shear stiffness and their viscoelastic properties and to integrate them into the framework of actual building codes which are all based upon Ayrton-Perry approach of imperfect columns. The present paper starts thus by recalling the framework of Linear Buckling Analysis of shear weak columns using the Timoshenko beam model. Then, Ayrton-Perry approach of the buckling of imperfect columns is introduced and used to develop a normal stress strength criterion for CLT walls but also an additional shear strength criterion. Both criteria are compared for three characteristic sizes of initial imperfections. Afterwards, orthotropic creep is introduced and its effect on long term stability of shear weak members is investigated and an extension of the previous criteria to long term behaviour is developed. Throughout the study, three numerical examples are used for illustration (a low strength panel, a high strength and an aerated panel) revealing the importance of proposed shear strength verification and the need of experimental characterisation.

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Rolling shear: Test configurations and properties of some European soft- and hardwood species

Cited by 81 publications

References 18 publications

Equivalent stiffness of timber used in CLT: closed-form estimates and numerical validation

Equivalent stiffness of timber used in CLT: closed-form estimates and numerical validation

The Rolling Shear Influence on the Out-of-Plane Behavior of CLT Panels: A Comparative Analysis

A shear strength criterion for the buckling analysis of CLT walls

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