Abstract
Cross-laminated timber (CLT) is an engineered wood product made up of layers of structurally graded timber, where subsequent layers are oriented orthogonally to each other. In CLT, the layers oriented in transverse direction, generally termed as cross-layer, are subjected to shear in radial–tangential plane, which is commonly known as rolling shear. As the shear modulus of cross-layers is significantly lower than that in other planes, CLT exhibits higher shear deformation under out-of-plane loading in contrast to other engineered wood products such as laminated veneer lumber (LVL) and glue laminated timber (GLT). Several analytical methods such as Timoshenko, modified gamma and shear analogy methods were proposed to account for this excessive shear deformation in CLT. This paper focuses on the effectiveness of Timoshenko method in hybrid CLT, in which hardwood cross-layers are used due to their higher rolling shear modulus. A comprehensive numerical study was conducted and obtained results were carefully analyzed for a range of hybrid combinations. It was observed that Timoshenko method could not accurately predict the shear response of CLTs with hardwood cross layers. Comprehensive parametric analysis was conducted to generate reliable numerical results, which were subsequently used to propose modified design equations for hybrid CLTs.
Highlights
Structural timber products can be classified into structurally graded timber boards and engineered wood products
The presented numerical study compared the accuracy of Timoshenko method for Cross-laminated timber (CLT) panels under out-of-plane bending over a range of rolling shear modulus considering softwood–hardwood hybrid compositions
It was observed that when the rolling shear modulus of the cross-layer of a CLT is considerably higher than that of the longitudinal layers, i.e., hardwood middle layer combined with softwood outer layers, the deflection predicted using Timoshenko method was significantly different from that obtained from FE
Summary
Structural timber products can be classified into structurally graded timber boards and engineered wood products. CLT offers relatively lower bending stiffness when compared to an equivalent GLT section This can be attributed to the orthogonal layout of cross-layers and the lower rolling shear modulus in timber [6]. A number of analytical methods such as Shear analogy, Timoshenko, modified gamma, and k-methods are currently used to evaluate the performance of CLT under out-of-plane loading. Shear analogy and Timoshenko methods are considered to be relatively more accurate for determining deflection in CLT [3]. Experimentally verified numerical models are used to examine the performance of Timoshenko method in predicting the deflection of CLT panels covering wide range of geometric properties and varying rolling shear modulus. A modification co-efficient for the Timoshenko method has been proposed to account for the effect of higher rolling shear modulus in hybrid CLT. The proposed technique has been validated against available bending tests on relevant CLT panels
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