STRENGTH OF CLT PANELS AT TENSION AND COMPRESSION ALONG GRAIN DIRECTION

Abstract

The bending strength of the plane and the tensile strength along the grain depend on the characteristic tensile strength of the boards along the grain, their coefficient of variation and the number of boards as a system, or the effective cross section of the CLT panel loaded along the grain direction. To date, studies have been performed to assess the tensile strength along the grain of the CLT panels, but there are no coefficients that take into account the possible load distribution similar to the bending strength from the plane of the panel. Neglecting the layers of crossboards when determining the net cross-sectional area Anet emphasizes the rationality of the introduction of a heterogeneous panel structure based on the strength class of boards, similar to combined plywood for beams, where high-strength boards are located in the upper and lower quarter or third of the cross section. The methodology showed in this paper for calculating the strength of inhomogeneous CLT panels shows its efficiency, which leads to optimization and material savings. The orthogonal structure of glued boards in the CLT panel when compressed perpendicular to the grain leads to strength and modulus of elasticity higher by 30% than for glued laminated timber, as indicated in the publication Brandner and Schickhofer (2014) [1], which also considers the stress dispersion model, previously developed by van der Put (1991, 2008, 2012) [4-6] according to which the stress dispersion along the fibers is 45 ° and 15 ° perpendicular to the grain. Studies of CLT panel samples have shown that the presence of gaps and compensatory cuts between the boards reduce the dispersion parameter by almost 2 times. With standard board thicknesses and the presence of cracks, the stress dispersion during compression perpendicular the panel plane is on average 35 °.