Skip header and navigation

6 records – page 1 of 1.

Creep Behavior of Laminated Veneer Lumber from Poplar Under Cyclic Humidity Changes

https://research.thinkwood.com/en/permalink/catalogue2480
Year of Publication
2019
Topic
Mechanical Properties
Moisture
Material
LVL (Laminated Veneer Lumber)

Finite Element Modelling of Moisture Related and Visco-Elastic Deformations in Inhomogeneous Timber Beams

https://research.thinkwood.com/en/permalink/catalogue425
Year of Publication
2013
Topic
Mechanical Properties
Moisture
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Ormarsson, Sigurdur
Dahlblom, Ola
Publisher
ScienceDirect
Year of Publication
2013
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Moisture
Keywords
Inhomogeneous
Finite Element Model
Axial Deformation
Lateral Deformation
Shrinkage
Mechanosorption
Visco-Elastic
Research Status
Complete
Series
Engineering Structures
Summary
Wood is a hygro-mechanical, non-isotropic and inhomogeneous material concerning both modulus of elasticity (MOE) and shrinkage properties. In stress calculations associated with ordinary timber design, these matters are often not dealt with properly. The main reason for this is that stress distributions in inhomogeneous glued laminated members (glulams) and in composite beams exposed to combined mechanical action and variable climate conditions are extremely difficult to predict by hand. Several experimental studies of Norway spruce have shown that the longitudinal modulus of elasticity and the longitudinal shrinkage coefficient vary considerably from pith to bark. The question is how much these variations affect the stress distribution in wooden structures exposed to variable moisture climate. The paper presents a finite element implementation of a beam element with the aim of studying how wooden composites behave during both mechanical and environmental load action. The beam element is exposed to both axial and lateral deformation. The material model employed concerns the elastic, shrinkage, mechano-sorption and visco-elastic behaviour of the wood material. It is used here to simulate the behaviour of several simplysupported and continuous composite beams subjected to both mechanical and environmental loading to illustrate the advantages this can provide. The results indicate clearly both the inhomogeneity of the material and the variable moisture action occurring to have had a significant effect on the stress distribution within the cross-section of the products that were studied.
Online Access
Free
Resource Link
Less detail

Long-Term Experimental Investigation of Timber Composite Beams in Cyclic Humidity Conditions

https://research.thinkwood.com/en/permalink/catalogue636
Year of Publication
2014
Topic
Serviceability
Moisture
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Hailu, Mulugheta
Shrestha, Rijun
Crews, Keith
Year of Publication
2014
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Serviceability
Moisture
Keywords
Creep
Eurocode 5
Relative Humidity
Moisture Content
Mechanosorption
Long-term
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
A long term laboratory investigation on two six-meter-span timber composite beams was started from March 2012 at the University of Technology Sydney. These timber composites were made of laminated veneer lumber (LVL). The web and the flanges of the composite timber section were connected using screw-gluing technique. The specimens have been under sustained loads of (2.1kPa) and the environmental conditions was cyclically alternated between normal and very humid conditions whilst the temperature remained quasi constant (22 °C) –typical cycle duration was six to eight weeks. With regard to EC 5, the environmental conditions can be classified as service class 3 where the relative humidity of the air exceeds 85% and the moisture content of the timber samples reaches 20%. During the test, the mid-span deflection, moisture content of the timber beams and relative humidity of the air were continuously monitored. The paper presents the results and observations of the long-term test to-date and the test is continuing.
Online Access
Free
Resource Link
Less detail

Long-Term Performance of Timber-Concrete Composite Flooring Systems

https://research.thinkwood.com/en/permalink/catalogue310
Year of Publication
2015
Topic
Connections
Mechanical Properties
Serviceability
Moisture
Material
LVL (Laminated Veneer Lumber)
Timber-Concrete Composite
Application
Floors
Author
Hailu, Mulugheta
Organization
University of Technology Sydney
Year of Publication
2015
Format
Thesis
Material
LVL (Laminated Veneer Lumber)
Timber-Concrete Composite
Application
Floors
Topic
Connections
Mechanical Properties
Serviceability
Moisture
Keywords
Serviceability Limit States
Deflection
Long-term Behaviour
Creep
Mechanosorption
Eurocode
Research Status
Complete
Summary
The objectives and scope of this study are to conduct long-term experimental test on timber-concrete composite beams, analyse the results to determine the creep coefficient of the composite system and compare the experimental results with the analytical solutions in accordance with Eurocode 5, in which the effective modulus method is used to account the effect of creep. To achieve the aforementioned objectives, a long-term laboratory investigation was started in August 2010 on four 5.8m span TCC beams with four different connector types. The specimens have been under sustained loads of 1.7kPa and subjected to a cyclic humidity conditions whilst the temperature remains quasi constant (22 °C). During the test, the mid-span deflection, moisture content of the timber beams and relative humidity of the air are continuously monitored. The long-term test is still continuing, two TCC beams were unloaded and tested to failure after 550 days, while the other two TCC beams are still being monitored and this report included experimental results up to the first 1400 days only. The long-term investigation on the two timber only composite floor beams commenced on March 2013 and the results are reported for the first 800 days from their commencement.
Online Access
Free
Resource Link
Less detail

Long-term Tensile Behaviour of Engineered Wood in Parallel to Grain Direction

https://research.thinkwood.com/en/permalink/catalogue2082
Year of Publication
2018
Topic
Serviceability
Material
LVL (Laminated Veneer Lumber)
Author
Chiniforush, Alireza
Akbarnezhad, Ali
Thakore, Prajeet
Ataei, Abdolreza
Organization
University of New South Wales
Year of Publication
2018
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Topic
Serviceability
Keywords
Visco-Elastic
Mechanosorption Creep
Shrinkage
Swelling
Deformation
Tensile Load
Long-term
Temperature
Relative Humidity
Numerical Model
Conference
World Conference on Timber Engineering
Research Status
Complete
Summary
Long-term serviceability is an important aspect in the implication of wood as a construction material. In this study, a comprehensive experimental program aims to address all the required parameters in long-term constitutive models of wood available in the literature which was taken from inconsistent sources earlier. The experimental program considers the effect of viscoelastic and mechano-sorptive creep, shrinkage and swelling, thermal and moisture inelastic deformation, and deformation due to Young’s modulus changes. The tests include tensile loading of wood specimens invariable outdoor climatic conditions in different applied stress levels. Sustained tensile loads were applied in parallel to the grain direction to specimens of Splash Pine (Pinus elliottii), Pacific Teak (Tectona grandis), and Laminated Lumber Veneer (LVL) of Radiata Pine (Pinus radiata). Tests were conducted at three different stress levels simultaneously and environmental parameters viz. temperature and relative humidity were monitored continuously throughout the loading period. Complementary data for diffusion coefficient, shrinkage, and swelling were measured in three orthogonal directions. In addition, sorption-desorption isotherm of the sample in the range of 0-100% relative humidity is presented.
Online Access
Free
Resource Link
Less detail

Moisture Induced Stresses in Glulam: Effect of Cross Section Geometry and Screw Reinforcement

https://research.thinkwood.com/en/permalink/catalogue176
Year of Publication
2012
Topic
Mechanical Properties
Moisture
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Angst-Nicollier, Vanessa
Organization
Norwegian University of Science and Technology
Year of Publication
2012
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Moisture
Keywords
Moisture Induced Stress
Mechanosorption
Numerical model
Tensile Strength
Tensile Stress
Load Bearing Capacity
Self-Tapping Screws
Climate
Research Status
Complete
Summary
This thesis presents a state of the art on moisture induced stresses in glulam, complemented with own findings. These are covered in detail in the appended papers. The first objective was to find a suitable model to describe moisture induced stresses, in particular with respect to mechanosorption. A review of existing models led to the conclusion that the selection of correct material parameters is more critical to obtain reliable results than the formulation of the mechanosorption model. A series of laboratory tests was thus performed in order to determine the parameters required for the model and to experimentally measure moisture induced stresses in glulam subjected to one dimensional wetting/drying. Special attention was paid to using glulam from the same batch for all the experimental measurements in order to calibrate the numerical model reliably. The results of the experiments confirmed that moisture induced stresses are larger during wetting than during drying, and that the tensile stresses could clearly exceed the characteristic tensile strength perpendicular to grain.
Online Access
Free
Resource Link
Less detail

6 records – page 1 of 1.