In a former paper by the authors , the elastic behavior of Cross Laminated Timber (CLT) and timber panels having periodic gaps between lateral lamellae has been analyzed. A thick plate homogenization scheme based on Finite Elements computations has been applied. The predicted behavior was in agreement with experimental results. In this paper, simplified closed-form solutions are derived in order to avoid FE modeling. Both cases of narrow gaps of CLT panels and wide gaps of innovative lightweight panels are investigated. CLT and timber panels with gaps are modeled as a space frame of beams connected with wooden blocks. The contribution of both beams and blocks to the panel’s mechanical response is taken into account, leading to closed-form expressions for predicting the panel’s stiffnesses and maximum longitudinal and rolling shear stresses. The derived closed-form solutions are in agreement with the reference FE results and they can be used for practical design purposes.
In this paper, the linear buckling of a heterogeneous thick plate is studied using the Bending–Gradient theory which is an extension of the Reissner–Mindlin plate theory to the case of heterogeneous plates. Reference results are taken from a 3D numerical analysis using finite-elements and applied to Cross Laminated Timber panels which are thick and highly anisotropic laminates. First, it is shown that critical buckling loads are close to the material failure load which proves the necessity of a design model for the buckling of Cross Laminated Timber panels. Second, the soft simple support boundary condition is introduced as an opposition to the conventional hard simple support condition. It is shown that this distinction could be taken into account for designing timber structures depending on the accuracy needed. Third, it is observed that for varying plate geometries and arrangements, the Bending–Gradient theory predicts more precisely the critical load of CLT panels than classical lamination and first-order shear deformation theories. Finally, it is demonstrated that one of the suggested projections of the Bending–Gradient on a Reissner–Mindlin model gives very accurate results and could favorably allow the development of engineering recommendations for estimating properly transverse shear effects.
Cross laminated timber (CLT) is leading the evolution of wood construction throughout the world. As atwo-dimensional plate-like construction product, the in-plane elastic constants of CLT panels are the fundamental parameters for serviceability design. The elastic constants including moduli of elasticity (MOE) in major and minor strength direction ( and y) and in-plane shear modulus ( xy) of full-size CLT panels with different dimensions and layups from three CLT producers were measured by a non-destructive test (NDT) method developed by the first author. In total, 51 CLT panels were tested with most of the testing conducted at CLT mills. The measured values were used to examine the existing effective stiffness prediction models of CLT. Results show that k-method can be used for predicting and y values of industrial size CLT with a large length/ width to thickness ratio. xy cannot be well predicted by k-method and is greatly affected by edge bonding and gaps. Gamma method and shear analogy method can include the effect of transverse shear to different extents into account in predicting apparent or y. Shear analogy method appears to predict closer apparent to the measured values than gamma method for CLT with small length to thickness ratio. However, the effect of transverse shear on apparent y is not as much as predicted by shear analogy method for CLT panels with width from 1 to 3 meters. NDT by modal testing was proven to be an efficient mechanical property evaluation method for full-size CLT panels.
This paper presents the development of two new types of hybrid cross-laminated timber plates (HCLTP) with an aim to improve structural performance of existing cross-laminated timber plates (Xlam or CLT). The first type are Xlam plates with glued timber ribs and the second type are Xlam plates with a concrete topping. A numerical...
In the present paper, the bending behavior of Cross Laminated Timber panels is investigated by means of the linear elastic exact solution from Pagano (1970; 1969). The resulting stresses are the input for a wood failure criterion, which can point out the first-crack load and the respective dominant failure mode. Heterogeneous layers are modeled as equivalent and homogeneous layers. This simplified and deterministic modeling gives results in good agreement with a reference experimental test. A comparison is made with respect to the panel’s global stiffness and failure stages within the apparent elastic stage. Finally, parameter studies are carried out, in order to quantify CLT limitations and advantages. The effect of varying properties like the panel’s slenderness, orientation of transverse layers and number of layers for a fixed total thickness are investigated.
A cross-laminated timber (CLT) wall plays the role of resisting shear stress induced by lateral forces as well as vertical load. Due to the press size, CLT panels have a limitation in size. To minimize the initial investment, some glulam manufactures wanted to make a shear wall element with small-size CLT panels and panel-to-panel connections and wanted to know whether the shear wall would have equivalent shear performance with the wall made of a single CLT panel. In this study, this was investigated by experiments and kinematic model analysis. Two shear walls made of small CLT panels were tested. The model showed a good agreement with test results in the envelope curve. Even though the shear walls were made of small panels, the global peak load did not decrease significantly compared with the wall made of a single CLT panel, but the global displacement showed a large increase. From this analysis, it was concluded that the shear wall can be designed with small CLT panels, but displacement should be designed carefully.
Cross-laminated timber (CLT) is well known as an interesting technical and economical product for modern wood structures. The use of CLT for modern construction industry has become increasingly popular in particular for residential timber buildings. Analyzing the CLT behavior in high thermal environment has attracted scholars’ attention. Thermal environment greatly influences the CLT properties and load bearing capacity of CLT, and the investigation can form the basis for predicting the structural response of such CLT-based structures. In the present work, the finite element method (FEM) is employed to analyze the thermal influence on the deformation of CLT. Furthermore, several factors were taken into consideration, including board layer number, hole conformation, and hole position, respectively. In order to determine the influence, several numerical models for different calculation were established. The calculation process was validated by comparing with published data. The performance is quantified by demonstrating the temperature distribution and structural deformation.