Measurement of rolling shear modulus of Cross Laminated Timber: Exploratory study using downscaled specimens under variable span bending tests

Rolling shear modulus and strength are the key factors affecting the mechanical performance of some wood products such as cross-laminated timber (CLT). As reported, rolling shear property strongly depends on the sawing pattern such as the aspect ratio and grain direction (grain mode). However, the mechanism behind this phenomenon has not yet been clarified. In this work, the rolling shear modulus and strength of spruce-pine-fir (SPF) with different grain modes and aspect ratios were experimentally investigated. In addition, a theoretical investigation was carried out to reveal the mechanism behind this phenomenon. The results exhibited that the rolling shear moduli of 0° and 90° grain-mode wood were the same. This value can be called the pure rolling shear modulus. Rolling shear modulus of wood with angles other than 0° and 90° can be calculated from the pure rolling shear modulus and grain angle. Therefore, this modulus can be called the apparent rolling shear modulus. Thus, using 0° and 90° grain-mode specimens to determine the pure rolling shear modulus and strength of wood is recommended.

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Influence of laminate direction and glue area on in-plane shear modulus of cross-laminated timber

SN Applied Sciences ◽

10.1007/s42452-020-03918-1 ◽

2020 ◽

Vol 2 (12) ◽

Author(s):

Jonas Turesson ◽

Zahra Sharifi ◽

Sven Berg ◽

Mats Ekevad

Keyword(s):

Finite Element ◽

Shear Modulus ◽

Compression Test ◽

Contact Area ◽

Tall Buildings ◽

Shear Stiffness ◽

Finite Element Simulations ◽

Plane Shear ◽

Cross Laminated Timber ◽

Diagonal Compression

AbstractThe use of cross-laminated timber (CLT) in constructing tall buildings has increased. So, it has become crucial to get a higher in-plane stiffness in CLT panels. One way of increasing the shear modulus, G, for CLT panels can be by alternating the layers to other angles than the traditional 0° and 90°. The diagonal compression test can be used to measure the shear stiffness from which G is calculated. A general equation for calculating the G value for the CLT panels tested in the diagonal compression test was established and verified by tests, finite element simulations and external data. The equation was created from finite element simulations of full-scale CLT walls. By this equation, the influence on the G value was a factor of 2.8 and 2.0 by alternating the main laminate direction of the mid layer from the traditional 90° to 45° and 30°, respectively. From practical tests, these increases were measured to 2.9 and 1.8, respectively. Another influence on the G value was studied by the reduction of the glue area between the layers. It was shown that the pattern of the contact area was more important than the size of the contact area.

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Low cycle fatigue tests and damage accumulation models on the rolling shear strength of cross-laminated timber

Journal of Wood Science ◽

10.1007/s10086-016-1547-6 ◽

2016 ◽

Vol 62 (3) ◽

pp. 251-262 ◽

Cited By ~ 9

Author(s):

Yuan Li ◽

Frank Lam

Keyword(s):

Shear Strength ◽

Damage Accumulation ◽

Low Cycle Fatigue ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Rolling Shear ◽

Cross Laminated Timber

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Comparison of Theoretical and Laboratory Out-of-Plane Shear Stiffness Values of Cross Laminated Timber Panels

Buildings ◽

10.3390/buildings8100146 ◽

2018 ◽

Vol 8 (10) ◽

pp. 146 ◽

Cited By ~ 3

Author(s):

Jan Niederwestberg ◽

Jianhui Zhou ◽

Ying-Hei Chui

Keyword(s):

Shear Modulus ◽

Cross Section ◽

Single Layer ◽

Beam Theory ◽

Shear Stiffness ◽

Plane Shear ◽

Shear Moduli ◽

Cross Laminated Timber ◽

Highly Sensitive ◽

Out Of Plane

The lay-up of cross laminated timber (CLT) leads to significant differences in properties over its cross-section. Particularly the out-of-plane shear behavior of CLT is affected by the changes in shear moduli over the cross-section. Results from laboratory shear tests are used to evaluate the shear stiffness of 3- and 5-layer CLT panels in their major and minor strength direction. The results are compared to calculated shear stiffness values on evaluated single-layer properties as well as commonly used property ratios using the Timoshenko beam theory and the shear analogy method. Differences between the two calculation approaches are pointed out. The shear stiffness is highly sensitive to the ratio of the shear modulus parallel to the grain to the shear modulus perpendicular to the grain. The stiffness values determined from two test measurements are compared with the calculated results. The level of agreement is dependent on the number of layers in CLT and the property axis of the CLT panels.

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Linear model to describe the working of a three layers CLT strip slab: Experimental and numerical validation

Advances in Structural Engineering ◽

10.1177/13694332211020403 ◽

2021 ◽

pp. 136943322110204

Author(s):

Martina Sciomenta ◽

Angelo Di Egidio ◽

Chiara Bedon ◽

Massimo Fragiacomo

Keyword(s):

Tangential Direction ◽

Elastic Model ◽

Bernoulli Beam ◽

Rolling Shear ◽

Bending Tests ◽

Linear Elastic ◽

Numerical Predictions ◽

Proposed Model ◽

Out Of Plane ◽

Euler Bernoulli Beam

Experimental out-of-plane, four-points bending tests were performed on two series of three-layered Cross Laminated Timber (CLT) panels made of Calabrian Beech and Calabrian Beech and Corsican Pine respectively. The predominant failure mechanism was rolling shear alongthe innerlayer and the glue line. A linear elastic model of a three-layered, CLT panel was developed to describe the stress distribution in CLT slabs in bending, with a focus on their load-bearing performance before the propagation of cracks. In the analytical model, each timber layer was defined as an Euler-Bernoulli beam. The two glue lines were modeled using extensional springs, infinitely rigid in the direction perpendicular to the beam’s axis, and with a defined stiffness in the tangential direction. The outer layers are assumed axially flexible whilethe innerone is regarded as axially rigid. The results of the proposed model were thus compared and validated with the experimental evidence and with additional FE numerical predictions given by 3D numerical simulations carried out in Abaqus.

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