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The strength of Glulam Beams with Holes - A Probabilistic Fracture Mechanics Method and Experimental Tests

https://research.thinkwood.com/en/permalink/catalogue2238
Year of Publication
2009
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Danielsson, Henrik
Organization
Lund University
Year of Publication
2009
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Holes
Strength
Research Status
Complete
Summary
This thesis deals with experimental tests and methods for strength analysis of glulam beams with holes. Test results and methods for strength analysis available in literature are compiled and discussed. The methods considered comprise both code strength design methods and more general methods for strength analysis. New strength tests of beams with quadratic holes with rounded corners are presented. The test programme included investigations of four important design para\-meters: material strength class, bending moment to shear force ratio, beam size and hole placement with respect to beam height. One important finding from these tests is the strong beam size influence on the strength. This finding is in line with previous test results found in literature but the beam size effect is however not accounted for in all European timber engineering codes. A probabilistic fracture mechanics method for strength analysis is presented. The method is based on a combination of Weibull weakest link theory and the mean stress method which is a generalization of linear elastic fracture mechanics. Combining these two methods means that the fracture energy and the stochastic nature of the material properties are taken into account. The probabilistic fracture mechanics method is consistent with Weibull weakest link theory in the sense that the same strength predictions are given by these two methods for an ideally brittle material. The probabilistic fracture mechanics method is also consistent with the mean stress method in the sense that the same strength predictions are given by these two methods for a material with deterministic material properties. A parameter study of the influence of bending moment to shear force ratio, beam size, hole placement with respect to beam height and relative hole size with respect to beam height is presented for the probabilistic fracture mechanics method. Strength predictions according to the probabilistic fracture mechanics method is also compared to the present and previous test results found in literature and also to other methods for strength analysis including code design methods. The probabilistic fracture mechanics method shows a good ability to predict strength, with the exception of very small beams.
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Mechanical Properties of Laminated Veneer Lumber Beams Strengthened with CFRP Sheets

https://research.thinkwood.com/en/permalink/catalogue2498
Year of Publication
2010
Topic
Mechanical Properties
Design and Systems
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Bakalarz, Michal
Kossakowski, Pawel
Organization
Kielce University of Technology
Publisher
Sciendo
Year of Publication
2010
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Mechanical Properties
Design and Systems
Keywords
Strengthening
Carbon Fibres
Timber Structures
Research Status
Complete
Series
Archives of Civil Engineering
Summary
This paper presents the results of the static work analysis of laminated veneer lumber (LVL) beams strengthened with carbon fabric sheets (CFRP). Tested specimens were 45mm wide, 100 mm high, and 1700 mm long. Two types of strengthening arrangements were assumed as follows: 1. One layer of sheet bonded to the bottom face; 2. U-shape half-wrapped reinforcement; both sides wrapped to half of the height of the cross-section. The reinforcement ratios were 0.22% and 0.72%, respectively. In both cases, the FRP reinforcement was bonded along the entire span of the element by means of epoxy resin. The reinforcement of the elements resulted in an increase in the bending strength by 30% and 35%, respectively, as well as an increase in the global modulus of elasticity in bending greater than 20% for both configurations (in comparison to the reference elements).
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Displacement-Based Seismic Design of Timber Structures

https://research.thinkwood.com/en/permalink/catalogue1891
Year of Publication
2011
Topic
Design and Systems
Seismic
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
LVL (Laminated Veneer Lumber)
Other Materials
Application
Wood Building Systems
Walls
Floors
Beams
Columns
Frames
Author
Loss, Cristiano
Publisher
University of Trento
Year of Publication
2011
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
LVL (Laminated Veneer Lumber)
Other Materials
Application
Wood Building Systems
Walls
Floors
Beams
Columns
Frames
Topic
Design and Systems
Seismic
Keywords
Direct Displacement-Based Design
Direct-DBD
Full-Scale
Single Family Houses
Multi-Storey
Connections
Research Status
Complete
Notes
Doctoral Thesis (PhD)
Summary
The research is aimed at developing seismic methods for the design and evaluation of the seismic vulnerability of wooden structures, using a displacement-based approach. After a brief introduction on the seismic behaviour of timber structures, the general Direct Displacement-Based Design (Direct-DBD) procedure and the state-of-the-art are presented, with clear reference to the application of the Direct-DBD method to wooden buildings. The strength of the Direct-DBD method is its ability to design structures in a manner consistent with the level of damage expected, by directly relating the response and the expected performance of the structure. The research begins with a description of the procedural aspects of the Direct-DBD method and the parameters required for its application. The research presented focuses on the formulation of a displacement-based seismic design procedure, applicable to one-storey wooden structures made with a portal system. This typology is very common in Europe and particularly in Italy. A series of analytical expressions have been developed to calculate design parameters. The required analytical Direct-DBD parameters are implemented based on the mechanical behaviour of the connections, made with metal dowel-type fasteners. The calibration and subsequent validation of design parameters use a Monte Carlo numerical simulation and outcomes obtained by tests in full-scale. After the description of the Displacement-Based method for one-storey wooden structures, a series of guidelines to extend the Direct-DBD methodology to other types and categories of timber systems are proposed. The thesis presents the case of a multi-storey wood frame construction, which is a simple extension of the glulam portal frame system. Part of this work has been done within the RELUIS Project, (REte dei Laboratori Universitari di Ingegneria Sismica), Research Line IV, which in the years between 2005 and 2008 involved several Italian universities and Italian institutes of research in the development of new seismic design methods. The Project produced the first draft of model code for the seismic design of structures based on displacement (Direct-DBD). This thesis is the background to the section of the model code developed for timber structures.
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Determining Optimised H3 LOSP Treatment Options for Decay Protection in Softwood Glulam

https://research.thinkwood.com/en/permalink/catalogue1930
Year of Publication
2011
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Cookson, Laurie
Publisher
Forest & Wood Products Australia
Year of Publication
2011
Format
Report
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
LOSP
CCA
TBTN
Treated Wood
Research Status
Complete
Summary
The objective of this research was to examine the LOSP treatment options available for H3 exposed glulam of Pinus radiata and P. elliottii. Test specimens were treated before or after gluing with azole LOSP, while some were treated with TBTN or CCA for comparison. They were then exposed at Innisfail or in an Accelerated Field Simulator (AFS) designed to give severe exposure and accelerated results. After 3.1–3.2 years, test specimens were given a performance rating from a scale of 8 (sound) to 0 (destroyed by decay). The results suggest that treating glulam before gluing will generally give better performance than treatment after gluing. Decay was more rapid in vertically exposed than horizontally exposed specimens, suggesting that glulam posts need special attention to prevent water penetration. End grain sealants based on copper naphthenate or zinc naphthenate gave improved decay resistance, but on their own were insufficient for post end protection. This suggests that a better approach would be to include barriers (caps) as well, or to use designs where the end is not exposed to rain or can drain away readily.
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Design of Post-Tensioned Timber Beams for Fire Resistance

https://research.thinkwood.com/en/permalink/catalogue4
Year of Publication
2012
Topic
Design and Systems
Fire
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Buchanan, Andrew
Abu, Anthony
Carradine, David
Moss, Peter
Spellman, Phillip
Year of Publication
2012
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Design and Systems
Fire
Keywords
Full Scale
Furnace Tests
Post-Tensioned
Box Beams
Vertical Loads
Failure
Conference
International Conference on Structures in Fire
Research Status
Complete
Notes
June 6-8, 2012, Zurich, Switzerland
Summary
This paper describes a series of three full-scale furnace tests on post-tensioned LVL box beams loaded with vertical loads, and presents a proposed fire design method for post-tensioned timber members. The design method is adapted from the calculation methods given in Eurocode 5 and NZS:3603 which includes the effects of changing geometry and several failure mechanisms specific to post-tensioned timber. The design procedures include an estimation of the heating of the tendons within the timber cavities, and relaxation of post-tensioning forces. Additionally, comparisons of the designs and assumptions used in the proposed fire design method and the results of the full-scale furnace tests are made. The experimental investigation and development of a design method have shown several areas which need to be addressed. It is important to calculate shear stresses in the timber section, as shear is much more likely to govern compared to solid timber. The investigation has shown that whilst tensile failures are less likely to govern the fire design of post-tensioned timber members, due to the axial compression of the post-tensioning, tensile stresses must still be calculated due to the changing centroid of the members as the fire progresses. Research has also highlighted the importance of monitoring additional deflections and moments caused by the high level of axial loads.
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Damping in Timber Structures

https://research.thinkwood.com/en/permalink/catalogue106
Year of Publication
2012
Topic
Design and Systems
Material
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Floors
Beams
Author
Labonnote, Nathalie
Organization
Norwegian University of Science and Technology
Year of Publication
2012
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Floors
Beams
Topic
Design and Systems
Keywords
Damping
Model
Panels
Spruce
Testing
Vibrations
Research Status
Complete
Summary
Key point to development of environmentally friendly timber structures, appropriate to urban ways of living, is the development of high-rise timber buildings. Comfort properties are nowadays one of the main limitations to tall timber buildings, and an enhanced knowledge on damping phenomena is therefore required, as well as improved prediction models for damping. The aim of this work has consequently been to estimate various damping quantities in timber structures. In particular, models have been derived for predicting material damping in timber members, beams or panels, or in more complex timber structures, such as floors. Material damping is defined as damping due to intrinsic material properties, and used to be referred to as internal friction. In addition, structural damping, defined as damping due to connections and friction in-between members, has been estimated for timber floors.
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Experimental and Analytical Investigation of Short-Term Behaviour of LVL–Concrete Composite Connections And Beams

https://research.thinkwood.com/en/permalink/catalogue150
Year of Publication
2012
Topic
Connections
Design and Systems
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
Timber-Concrete Composite
Application
Beams
Author
Khorsandnia, Nima
Valipour, Hamid
Crews, Keith
Publisher
ScienceDirect
Year of Publication
2012
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Timber-Concrete Composite
Application
Beams
Topic
Connections
Design and Systems
Mechanical Properties
Keywords
Four Point Bending Test
Screws
Load Deflection
Model
Full Scale
Research Status
Complete
Series
Construction and Building Materials
Summary
This paper reports the results of experimental push-out tests on three different types of timber–concrete composite (TCC) connections, including normal screw, SFS and bird-mouth. The load-slip diagrams obtained from lab tests are employed to calculate the slip modulus of the connections for serviceability, ultimate and near collapse cases based on Eurocode 5 recommendations. Additionally, four full-scale TCC beams with normal screw, SFS and bird-mouth are constructed and tested under four-point bending within the serviceability load range to verify the slip modulus of connections which derived from the push-out tests. Further, based on the experimental results and using nonlinear regression, an analytical model each one of the connections is derived which can be easily incorporated into nonlinear FE analyses of TCC beams.
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The Fire Performance of Post-Tensioned Timber Beams

https://research.thinkwood.com/en/permalink/catalogue159
Year of Publication
2012
Topic
Fire
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Spellman, Phillip
Organization
University of Canterbury
Year of Publication
2012
Format
Thesis
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Fire
Keywords
Failure Mechanisms
Full Scale
Post-Tensioning
Steel Tendons
Fire Resistance
Box Beams
Research Status
Complete
Summary
The focus of this research was to investigate the fire performance of post-tensioned timber beams. This was completed through a series of full-scale furnace tests, and the development of a fire resistance design method. Previous research has focused on the seismic performance and gravity frame performance of post-tensioned timber, both of which yielded promising results. There is however a commonly perceived increase in fire risk with timber building, particularly multi-storey timber buildings, and the fire performance of post-tensioned timber had not previously been investigated.
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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.
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Full-Scale Fire Tests of Post-Tensioned Timber Beams

https://research.thinkwood.com/en/permalink/catalogue257
Year of Publication
2012
Topic
Fire
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Spellman, Phillip
Carradine, David
Abu, Anthony
Moss, Peter
Buchanan, Andrew
Year of Publication
2012
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Fire
Keywords
Failure Mechanisms
Steel Anchorage
Full Scale
Furnace Tests
Post-Tensioned
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
July 15-19, 2012, Auckland, New Zealand
Summary
This paper describes a series of full-scale furnace tests on loaded post tensioned LVL beams. Each beam was designed to exhibit a specific failure mechanism when exposed to the standard ISO834 fire. In addition to the beams a number of steel anchorage protection schemes were also investigated. These included wrapping the ends in kaowool, using intumescent paint, covering the anchorage with fire rated plasterboard and covering the anchorage with timber (LVL). The results of the full-scale tests cover temperature distributions through the timber members during the tests, the temperatures reached within the cavity and those of the tendons suspended within the cavity, the relaxation of the tendons during the test, the failure mechanisms experienced, and a summary of the anchorage protection details and their effectiveness. Recommendations for the design of both post-tensioned timber beams and associated anchorages are also provided.
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226 records – page 1 of 23.