Structural performance of hybrid Poplar-Beech cross-laminated-timber (CLT)

Abstract

The purpose of this research was to investigate the structural out-of-plane bending performance of three-layer hybrid cross-laminated-timber manufactured from outer layers of fast-growing Poplar (Populus alba) and a cross-layer of Iranian Beech species (Fagus orientalism) using polyurethane as a binder. The bending performance of the hybrid CLT was determined in both major and minor axis orientations in diverse span-to-thickness ratios by experimental and theoretical methods. It was compared to that of Poplar CLT reported in our previous research. The experimental and theoretical methods indicated that the bending performances comprising maximum shear force (Vmax), maximum bending moment (Mmax), apparent modulus of elasticity (MOEapp), modulus of rupture (MOR), shear strength (τmax), effective bending stiffness (EIeff), and effective shear stiffness (GAeff) of hybrid Poplar-Beech CLT in all span-to-thickness ratios at both major and orientations were greater than those of Poplar CLT. Moreover, in both orientations, the results of bending and shear stress distributions of the specimens showed that the hybrid Poplar-Beech CLT had greater load-carrying capacity than Poplar CLT. However, in both orientations, the failure modes of hybrid CLT were similar to those of Poplar CLT. The experimental dominant failure modes in the major axis orientation of CLTs were rolling shear and delamination, while tensile failure and crack were mainly observed in the minor axis orientation. In summary, in comparison with Poplar CLT, both experimental and theoretical results revealed that hybrid Poplar-Beech CLT had more tremendous potential for structural bending performance in the construction and building sector.