: A computer aided numerical model for the simulation of the in-plane bending strength of CLT beams is presented. The model uses the Monte-Carlo-Method to generate mechanical characteristics of board lamellae and is suitable for the investigation of statistical effects such as homogenisation and size effects. Six different types of CLT beams, varying in size and in layup, were tested to validate the model and except for beams with only one lamella in direction of the beam height good agreement was found between the experimental results and the model’s simulations.
International Convention of Society of Wood Science and Technology
June 23-27, 2014, Zvolen, Slovakia, p.761-768
The mission of the Hardwood Scanning Center at Purdue University is to increase the
global competitiveness of the United States hardwood industry and to conserve the
hardwood resource by development of manufacturing technologies which will enable
hardwood industry to “see inside a tree” and use this information to make better
The Hardwood Scanning Center partnered with Microtek, GmbH of Italy in the
development of an industrial grade log CT scanner. World’s first three industrial CT log
scanners have been installed in last 12 months in mills around the world and we will
briefly discuss their application. The Hardwood Scanning Center also developed
visualization and optimization software for the hardwood veneer and sawmill operations.
This presentation will provide an overview of state-of-the-art in CT scanning of logs.
The paper examines the behaviour of structural timber members subjected to axial compression or combined axial compression and bending. Based on experimental and numerical investigations, the accuracy of the existing approach in Eurocode 5 for the design of timber members subjected to axial compression or combined axial compression and bending is assessed and modifications are suggested. By means of extensive experimental investigations, a data base was created for the validation of calculation models and for the assessment of design concepts. In order to assess the behaviour of timber members subjected to axial compression or combined axial compression and bending, strain-based calculation models were developed.
The investigations indicate that the existing approach of Eurocode 5 based on 2nd order analysis can lead to an overestimation of the load-bearing capacity. Hence, a modified design approach was developed which agrees with the results of the Monte Carlo simulations very well and thus ensures a safe and economical design of timber members subjected to compression or combined compression and bending.
CLT panels consist of several layers of lumber stacked crosswise and glued together on their faces. Prototype Sugi CLT floor panels were manufactured and bending and internal shear tests were carried out under the different parameters of lumber MOE, number of layers, thickness of lumber and thickness of CLT panels. On the basis of above tests, internal shear strength, bending stiffness and moment carrying capacity were estimated based on the lumber properties by Monte Carlo method. Bending stiffness EI of CLT panels could be estimated by adopting parallel layer theory and equivalent section area. Experimental moment carrying capacity showed 12% higher value than the calculated moment carrying capacity by average lumber failure method, and also showed 45% higher value than the calculated moment carrying capacity by minimum lumber failure method due to the reinforcement of the outer layer by the neighboring cross layer. Experimental internal shear force of CLT panel showed 30% higher value than the calculated one.
Cross-laminated timber (CLT) panels consist of several layers of lumber stacked crosswise and glued together on their faces. Prototype sugi CLT floor panels were manufactured and bending tests were carried out under the different parameters of lumber modulus of elasticity (MOE), number of layers, thickness of lumber and thickness of CLT panels. On the basis of above tests, bending stiffness and moment carrying capacity were predicted by Monte Carlo method. MOE of lumber was measured by using grading machine and tensile strength of lumber was assumed to be 60 % of bending strength based on the obtained bending test. Bending stiffness EI of CLT panels could be estimated by adopting composite theory and equivalent section area. Experimental moment carrying capacity showed 12 % higher value than the calculated moment carrying capacity by average lumber failure method, and also showed 45 % higher value than the calculated moment carrying capacity by minimum lumber failure method due to the reinforcement of the outer layer by the neighboring cross layer.
Compressive strength of cross-laminated timber (CLT) is one of the important mechanical properties which should be considered especially in design of mid-rise CLT building because it works to resist a vertical bearing load from the upper storeys. The CLT panel can be manufactured in various combinations of the grade and dimension of lamina. This leads to the fact that an experimental approach to evaluate the strength of CLT would be expensive and time-demanding. In this paper, lamina property-based models for predicting the compressive strength of CLT panel was studied. A Monte Carlo simulation was applied for the model prediction. A set of experimental compression tests on CLT panel (short column) was conducted to validate the model and it shows good results. Using this model, the influence of the lamina’s width on the CLT compressive strength was investigated. It reveals that the CLT compressive strength increases with the increase in the number of lamina. It was thought that repetitive member effect (or dispersion effect) is applicable for the CLT panel, which was explained by the decrease of the variation in strength. This dependency of the number of lamina needs further study in development of reference design values, CLT wall design and CLT manufacturing.
This thesis examines the behaviour of structural timber members subjected to compression alone or in combination with bending. Based on experimental and numerical investigations, the knowledge on the behaviour of these timber members is extended and advanced calculation models are developed. In addition, the accuracy of existing approaches for the design of these members is assessed and modifications are suggested.
By means of extensive experimental investigations, a data base was created which can be used for the validation of calculation models and for the assessment of design concepts. The experimental investigations are carried out on eccentrically loaded compression members made of glued laminated timber. Different parameters such as the strength class of the glued laminated timber or the slenderness ratio of the members are investigated.
In this thesis the reliability of the design of unreinforced notched beams is evaluated and recommendations for the design of reinforced notched beams are given. The review of design approaches for reinforced notched beams shows, that so far the reinforcement is designed only with regard to the perpendicular to grain force acting in the notch corner. The evaluation of test results from literature shows that a stiff reinforcement has the best reinforcing effect but initial cracking cannot be prevented. The failure behaviour of the reinforced notch is studied in more detail by means of experiments and a FE model. Initial cracking of the reinforced notch comes along with crack opening, whereas ultimate failure with excessive crack growth is accompanied by shearing of the crack. An analytical model is presented for the description of the structural behaviour of reinforced notched beams. The parallel and perpendicular to the grain stiffness of the reinforcement is accounted for in the model. A high stiffness of the reinforcement parallel to the grain is required in order to reduce the mode 1 loading of the notch corner and to prevent initial cracking. The mode 2 loading of the crack increases with increasing crack length. In order to achieve higher load-carrying capacities for notched beams with longer cracks, reinforcement with high stiffness parallel to the grain is required. Recommendations are given for the required reinforcement of notched beams in order to restore the shear capacity of the reduced cross-section.
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.