Shear Properties of Eastern Hemlock with Respect to Fiber Orientation for Use in Cross Laminated Timber

Bahmanzad, A.; Clouston, Peggi L.; Arwade, Sanjay R.; Schreyer, Alexander C.

doi:10.1061/(asce)mt.1943-5533.0003232

Cited by 14 publications

(8 citation statements)

References 13 publications

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“…(200 MPa) is approximately 35% higher than both the experimental and FEM results. These results seem to agree with the study by Bahmanzad et al [7] that showed the predicted shear modulus from Hankinson's equation for the tested specimen with the angle-ply of 30° (the only tested ± α angle-ply specimen with a grain orientation (α) less than 40°) has a larger difference from the experimental result compared to the other angle-ply specimens with grain orientations of 45°, 60° and 90°.…”

Section: Effect Of Angle-ply Grain Orientation On Shear Modulussupporting

confidence: 91%

Evaluating the Shear Stiffness of Asymmetric Angle-Ply Layers in Diagonal Cross-laminated Timber

kurzinski,

Crovella

2023

Preprint

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The perpendicular orientation of the cross-layer (s) makes Cross-laminated Timber (CLT) susceptible to rolling shear failure and reduced stiffness in bending. Under out-of-plane bending, rolling shear failure occurs in the cross layers along the radial-tangential plane. This weakness in CLT panels could be improved by varying the grain orientation of the cross-layers away from perpendicular-to-grain (90°), and closer to parallel-to-grain (0°). This paper studies the shear stiffness of a pair of asymmetric angle-ply layers rotated at angles from 90° to 70°, 40°, 20°, 10°, and 0°. These two layers with varying grain orientations were assumed to be representative of the inner layers of a four-ply Diagonal Cross-laminated Timber (DCLT) panel. For this purpose, Hankinson’s formula was applied in addition to two-plate shear tests and numerical modeling. The experimental testing and FE model results were compared with the theoretical values to evaluate the theory for shear stiffness prediction of the asymmetric angle-ply layers. The results of the three methods showed an agreement in predicting an increase in shear stiffness when the angle-ply orientation of the layers decreases from 90° to 0°. The results indicated that Hankinson’s formula seems to be a conservative theoretical predictor for the shear stiffness of diagonal layers. Regarding the experimental results, orienting the cross layers to an angle between 70° and 40° was shown to improve the rolling shear stiffness by 10% and 46% respectively. This research provides insights into innovations towards CLT development with improved rolling shear stiffness using diagonally-oriented layers.

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Section: Effect Of Angle-ply Grain Orientation On Shear Modulussupporting

confidence: 91%

Evaluating the Shear Stiffness of Asymmetric Angle-Ply Layers in Diagonal Cross-laminated Timber

kurzinski,

Crovella

2023

Preprint

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“…For Glr and Glt, the angle between the loading direction and the axial direction of wood fiber cells is small, leading to higher shear modulus. Bahmanzad et al [39] also confirmed that the shear modulus and strength were both decreased with the increasing of degree between fiber orientation and load direction of eastern hemlock wood, as well as the results of Zhang and Yang [15].…”

Section: Compressive Elastic Contents Of Beech Wood With Different Mo...mentioning

confidence: 69%

Effects of Moisture Content and Grain Direction on the Elastic Properties of Beech Wood Based on Experiment and Finite Element Method

Guan

Kei

2021

Forests

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Beech wood (Fagus sylvatica L.) is used in a wide range of wood products. However, the influence of the wood’s moisture content on its mechanical functions will affect its structural strength. It would be complicated and time-consuming to experimentally measure wood’s mechanical functions under different moisture contents. Therefore, it is necessary to establish a prediction formula between the moisture content and elastic constants, and then verify whether its mechanical functions within a wide range of moisture content can be studied by using FEM (finite element method). In this study, which was based on experimentation, we studied the influence of a wide range of moisture contents and grain direction on the compressive yield strength, modulus of elasticity and shear modulus of beech wood. The relationship between the moisture content and elastic constants was established; the moisture sensitivities of different elastic parameters were obtained. Ultimately, compression curves under different moisture contents were plotted out, using both FEM and experimentation. According to the results, the interaction of moisture with the grain direction had a significant effect on the elastic constants of wood, with grain direction having a greater effect on the elastic properties than the moisture content. Moreover, the decay function can be used to fit these experimental results well. The elastic constants of beech wood responded differently to the moisture content, depending on whether it was in the longitude or transverse directions. Finally, this study proved the feasibility of using FEM to simulate wood’s compressive performance with a wide range of moisture contents.

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“…Research work has been conducted to enhance the rolling shear strength of CLT panels. Bahmanzad et al (2020) reported higher ultimate loads and lower shear deformation with a brittle failure mechanism when the transverse layer was also oriented parallel to the outer layers rather than in a perpendicular arrangement. Similarly, Buck et al (2016) also reported an increase of 35% in modulus of rupture (MOR) when the transverse layer was oriented at 45.…”

Section: Introductionmentioning

confidence: 96%

Influence of densification on structural performance and failure mode of cross-laminated timber under bending load

Pradhan,

Mohammadabadi,

Entsminger

et al. 2024

BioRes

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The effect of densification of the laminas was studied relative to the shear performance of cross-laminated timber (CLT) specimens submitted to the bending test. The three-layered CLT panels were fabricated using loblolly pine (Pinus taeda L.). A compression ratio (CR) of 50% was used to densify the lumber using the thermomechanical densification technique. The process included plasticizing the lumbers by soaking them in boiling water for 10 minutes and then hot-pressing to the target thickness at 140 °C. Four groups were made, i.e., a control sample with all three layers non-densified, only mid-layer densified, all layers densified, and all layers planed to the same thickness of densified layers. Specimens were tested in short-span bending with a span-to-depth ratio of eight. For specimens having densified mid-layer, the failure mode changed from rolling shear to tensile failure of the outer layer, and the maximum shear stress was increased by 34%. Densification of the mid-layer at CR of 16% was sufficient to change the failure mode from rolling shear in mid-layer to tensile in outer layer. In the case of all-layer-densified specimens, the maximum rolling shear strength was increased by 129% compared to the control.

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Shear Properties of Eastern Hemlock with Respect to Fiber Orientation for Use in Cross Laminated Timber

Cited by 14 publications

References 13 publications

Evaluating the Shear Stiffness of Asymmetric Angle-Ply Layers in Diagonal Cross-laminated Timber

Evaluating the Shear Stiffness of Asymmetric Angle-Ply Layers in Diagonal Cross-laminated Timber

Effects of Moisture Content and Grain Direction on the Elastic Properties of Beech Wood Based on Experiment and Finite Element Method

Influence of densification on structural performance and failure mode of cross-laminated timber under bending load

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