Proceedings of the Institution of Civil Engineers - Construction Materials
Novel cross-laminated bamboo panels comprising three and five layers (G-XLam3 and G-XLam5) were tested in compression along the main (0°) and the transverse (90°) directions. Linear variable differential transformer (LVDT) and non-contact three-dimensional digital image correlation (DIC) measuring techniques were used separately to measure deformation in the elastic region, and the elastic moduli, Ep C,0 and Ep C,90, were derived. Mean elastic modulus values obtained using LVDTs exhibited a good match with analytically predicted values. In contrast, the elastic values obtained by the DIC method were considerably higher and presented a considerable scatter of results. For instance, the Ep C,0 for G-XLam3 and G-XLam5 panels were 17·22 and 15·67 GPa, and 14·86 and 12·48 GPa, using the DIC and LVDT methods, respectively. In general, G-XLam panels with a fifth of the cross-sectional thickness and twice the density of analogous cross-laminated timber exhibited an approximately two-fold increase in Ep C,0 and Ep C,90. Overall, this research provides guidelines for the assessment and standardisation of the testing procedures for similar engineered bamboo products using contact and non-contact methods and highlights the potential of using G-XLam panels in stiffness-driven applications and in combination with wood for structural purposes.
International Council for Research and Innovation in Building and Construction, Working Commission W18 - Timber Structures
August 26-29, 2013, Vancouver, Canada
Beams made of cross laminated timber (CLT) offer several advantages over solid or glued laminated timber beams due to their typical layup of orthogonally bonded layers. One major benefit of CLT is the high tensile strength perpendicular to the beam axis making CLT-beams less susceptible to cracks. Therefore, the use of CLT for the production of beams with tensile stresses perpendicular to the beam axis provides a considerably improved robustness. In Europe, the requirements for the production and design of CLT-products are currently governed by technical approvals. However, a draft European standard specifying the performance requirements of cross laminated timber products has already been published in 2011. Although most of today’s CLT-products are very similar in their structure and also efforts are made to develop standardised methods for design and verification of CLT, there is, so far, no general approach for the shear design of CLT-members loaded in plane. In fact, the strength properties and also the design methods given in different technical approvals for the verification of in plane shear stresses vary significantly and, moreover, for most products no information on the shear stiffness in plane direction is given at all. One main reason for the disparities seems to be the more complex calculation of shear stresses and deformations in CLT-members compared to traditional timber materials and therefore, in many cases, vastly simplified methods are used. The intention of the present paper is to contribute to the development of standardised methods for the shear design of CLT-members loaded in plane. Therefore, at first, analytical solutions for the calculation of shear stresses and shear deformations in CLT-beams loaded in plane are presented. The equations are then validated by test results.