This paper presents the formulae and finite element analysis models for predicting the Modulus of Elastic (MOE) and Modulus of Rupture (MOR) of Cathay poplar finger-jointed glulam. The formula of the MOE predicts the MOE of Cathay poplar glulam glued with one-component polyurethane precisely. Three formulae are used to predict the MOR, and Equation (12) predicts the MOR of Cathay poplar glulam precisely. The finite element analysis simulation results of both the MOE and MOR are similar to the experimental results. The predicted results of the finite element analysis are shown to be more accurate than those of the formulae, because the finite element analysis considers the glue layers, but the formulae do not. Three types of typical failure modes due to bending were summarized. The bending properties of Cathay poplar glulam were compared to those of Douglas fir glulam. The results show that Cathay poplar glulam has a lower stiffness, but a marginally higher strength. One-component polyurethane adhesive is shown to be more effective than resorcinol formaldehyde resin adhesive for Cathay poplar glulam. This study shows that Cathay poplar has the potential to be a glulam material in China.
Cross-Laminated Timber (CLT) is a relatively new construction material that has not gained popularity in Hungary yet. Producing such building elements using Hungarian raw materials may help to establish this technique. The purpose of our research was to examine the possibility of producing CLT using Hungarian I-214 hybrid poplar. One three-layer panel was produced using Hungarian hybrid polar and polyurethane resin, and tested in bending. The MOR of the poplar CLT was found to be comparable to low-grade softwood CLT, but the MOE was lower than the requirement. Poplar raw material may be suitable for CLT production by selecting higher grade raw material using nondestructive testing, or as a secondary raw material mixed in with softwood.
Society of Wood Science and Technology International Convention
Failure modes of Cross Laminated Timber (CLT) plates reach by an excess of tensile stress on
finger joints, shear stress on transverse layer due to rolling shear effect and by natural
vibration. The Probability of Failure (POF) of CLT plates can be estimated from the probability
distribution of their ruptures and stiffnesses, as well as their correlation coefficients. In this
context, the aim of this paper is to estimate the load capacity of Cross Laminated Timber plates
from a specific probability of failure and the experimental results of mechanical and physical
properties. For this purpose, CLT plates were manufactured with wood species of Pinus taeda
L., from Brazilian reforestation plantations. Four-point bending tests were conducted to
investigate the failure behavior of the CLT plates. Density and moisture content were obtained
from small specimens extracted from these plates. Monte Carlo simulation was carried out to
predict the probabilistic loads that produce the failure of CLT plates, considering the failure
occasioned by natural vibration as well. Experimental and numerical results of the failure
modes were compared and the maximum loads to an acceptable probability of failure of the
several CLT lengths were estimated too.
The behaviour of timber-steel hybrid beams for buildings is very complex because of the combination of the two very different materials that are wood and steel. Numerical simulation of such behaviour requires an accurate description of orthotropic material’s behaviour with damage. This paper describes 3D-Finite Element (FE) simulation results obtained using an elasto-plastic model coupled with an isotropic ductile damage, and implemented into ABAQUS/Explicit FE software. After a short presentation of the constitutive equations and their related numerical aspects, the validation of the model was carried out by simulating timber-steel hybrid beams. Good agreement was found between FE and experimental results, showing the good capability of the model to predict the ductile damage evolution in bending test of timber-steel hybrid structures.
The paper describes experimental and numerical analyses on a completely new connection system developed for CLT (Cross Laminated Timber) constructions. The innovative solution herein proposed, named X-RAD, consists of a point-to-point mechanical connection system, fixed to the corners of the CLT panels. This connection, that is designed to be prefabricated, is made of a metal wrapping and an inner hard wood element which are fastened to the panel by means of allthreaded self-tapping screws. Such system permits to reduce significantly the number of bolts/fasteners required to assemble two or more panels together or to connect them to the foundation. This results in the enhancement of the installation process in terms of speed, quality and safety. One of the reasons that fuelled the development of the presented system, is the desire of offering a solution to those issues (e.g. to satisfy ductility and energetic dissipation requirements) commonly related to the seismic safety of timber structures. In other words there was the will of defining a system able to guarantee an adequate level of ductility and energetic dissipation.