Elastic behavior of Cross Laminated Timber and timber panels with regular gaps: Thick-plate modeling and experimental validation

Abstract

In the present paper, the influence of periodic gaps between lamellas of Cross Laminated Timber (CLT) on the panel's elastic behavior is analyzed by means of a periodic homogenization scheme for thick plates having periodic geometry. Both small gaps, due to the fabrication process of not-gluing lateral lamellas, and wider gaps are investigated. The results obtained with the periodic homogenization scheme are compared to existing closed-form solutions and available experimental data. It appears that the plate bending stiffness can be well predicted with both homogenization and simplified methods, while only the homogenization approach is in agreement with the experimental in-plane and out-of-plane shear behavior. The influence of several properties of CLT lay-up on the mechanical response is pointed out as well.

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

“…Following Hashin (1986Hashin ( , 1987 variational principles, Nairn (2017) also suggested an equivalent layer in-plane shear modulus. Finally, Franzoni et al (2017Franzoni et al ( , 2018 also studied this behavior at the scale of a CLT plate with small or large gaps by means of a periodic plate homogenization scheme and suggested closed-form formula.…”

“…Finally, the detailed treatment of the cross layer shear stiffness G C Z requires also a 3D analysis as it involves complex interactions with the upper and lower longitudinal layers. Neglecting the influence of the sawing pattern, this analysis was achieved by Franzoni et al (2017Franzoni et al ( , 2018 and closed-form formula were suggested as well. This required a modeling based on a thick plate homogenization scheme (Lebée and Sab, 2012b;Sab and Lebée, 2015).…”

“…Nevertheless, for α > 30°, (2b/t < 4), the difference between free and glued narrow edges numerical upper bounds is becoming significant as the free edges bound is dropping rapidly (recall that the closed-form lower bound is only valid for glued edges). Hence for aspect ratios smaller than 4, the closed-form bound should be used with care and more refined approaches are required for estimating the cross-layer shear stiffness modulus, such as periodic plate homogenization techniques (Sab and Lebée, 2015;Franzoni et al, 2017), taking annual rings orientation into account.…”

“…Finally, the in-plane shear stiffness modulus G LC is involved in shear walls. Particularly, the narrow edge gluing and the board aspect ratio have a strong influence on G LC (Moosbrugger et al, 2006;Bogensperger et al, 2010;Franzoni et al, 2017). All these parameters necessitate recommendations depending on timber strength class, on the board aspect ratio and on the narrow edge gluing as suggested in the draft for a revised version of the Eurocode 5-1-1 (2015), but the sawing pattern may also be taken into account.…”

A shear strength criterion for the buckling analysis of CLT walls

“…• CLT3 is an aerated CLT with a similar configuration to CLT2 (80 − 40 − 40 − 40 − 80), but with 50% of voids in the three central layers. (This kind of configuration becomes indeed more and more popular in the last decade [24,25,26]. Similar local properties will be considered as CLT2 except for the rolling shear strength for which an equivalent strength of 2 is chosen because the contact between the central layer is ensured by one fourth ( 2 ) of the total surface, so that the maximum stress is four times the average evaluated by expression (13b).…”