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Structural Behaviour of Glued Laminated Timber Beams with Unreinforced and Reinforced Notches

https://research.thinkwood.com/en/permalink/catalogue311
Year of Publication
2014
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Jockwer, Robert
Organization
ETH Zurich
Year of Publication
2014
Country of Publication
Switzerland
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Finite Element Model
Load Carrying Capacity
notch
Monte Carlo
Failure Behavior
Language
English
Research Status
Complete
Summary
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.
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Structural Behaviour of Glued Laminated Timber Beams Pre-Stressed by Compressed Wood

https://research.thinkwood.com/en/permalink/catalogue303
Year of Publication
2012
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Anshari, Buan
Wei Guan, Zhong
Kitamori, Akihisa
Jung, Kiho
Komatsu, Kohei
Publisher
ScienceDirect
Year of Publication
2012
Country of Publication
Netherlands
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Compressed Wood
Reinforcement
Pre-Stressing
Moisture Content
Language
English
Research Status
Complete
Series
Construction and Building Materials
Summary
In this study, glulam beams were strengthened by inserting compressed wood (CW) blocks into the precut rectangular holes with one-thirds of the beam depth from the top of the beams. This practice was to make use of moisture-dependent swelling nature of the compressed wood which was conditioned with the moisture content significantly lower than the ambient one. The test results showed that a pre-camber was produced in the mid-span of the beam reinforced due to expansion of the compressed wood blocks on the top part of the beam. As a result, significant initial tensile and compressive stresses were generated on both the top and the bottom extreme fibres of the beam, respectively. Subsequent bending tests revealed that the initial stiffness and load carrying capacity of the pre-stressed beams were increased significantly in comparison to the beam without pre-stressing.
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Influence of Varying Material Properties on the Load-Bearing Capacity of Glued Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue173
Year of Publication
2014
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Fink, Gerhard
Organization
ETH Zurich
Year of Publication
2014
Country of Publication
Switzerland
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Knot Clusters
Non-Destructive
Tensile tests
Load Carrying Capacity
Joints
Model
Language
English
Research Status
Complete
Summary
Glued laminated timber (GLT) is a structural product composed of several layers of timber boards glued together. GLT components have many advantages, such as the larger range of available component dimensions to choose from, the environmental sustainability or the e- cient ratio between weight and load-bearing capacity. Because of that, GLT beams have been established as one of the most important products in timber engineering in the last decades. As a natural grown material, timber properties exhibit higher variability, compared with other building materials. The variability is pronounced not only between dierent structural elements but also within single elements, the latter being highly related to the occurrence of knot clusters. Due to the highly inhomogeneous structure of timber, the prediction of the material properties of GLT beams is aected by large uncertainties. In the presented thesis, the in uence of varying material properties on the load-bearing capacity of GLT beams was investigated. Thus the thesis contributes to develop the quality of GLT beams, in terms of reliability and eciency. Detailed, non-destructive investigations of altogether 400 timber boards were performed. Thereby, dierent strength and stiness related indicators, such as the position and characteristic of knots, or the eigenfrequency, were assessed. Furthermore, non-destructive tensile test were performed to estimate the stiness properties of knot clusters. Out of the investigated timber boards, GLT beams having a precisely-known beam setup were fabricated. As a result, the exact position of each particular timber board (and each particular knot cluster) within the GLT beams was known. Afterwards, bending tests were performed to estimate the load-bearing capacity of these GLT beams. Thereby, the in uence of knot clusters and nger joint connections on the deformation and failure behaviour was investigated. In addition to the experimental investigations, a probabilistic approach for modelling GLT beams (referred to as GLT model ) was developed. Thereby, at rst, timber boards are simulated according to their natural growth characteristics. Afterwards, out of the simulated timber boards, virtual GLT beams are fabricated. Finally, the load-bearing behaviour of these GLT beams is estimated by using a numerical model. To assure the quality of the numerical model, it was validated with the test results. Using the GLT model, the in uence of dierent parameters, such as the position and characteristics of knots, or the quality of nger joint connections, on the load-bearing capacity of GLT beams was investigated. One further goal of this thesis was the investigation of machine-grading indicators, that are measured during the grading process. Therefore, all the investigations presented in this thesis are conducted for indicators measured in laboratory and machine-grading indicators. The same applies for the GLT model, which was also developed for both types of indicators
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Behaviour of Glued-Laminated (Glulam) Beams and Columns Subjected to Simulated Blast Loads

https://research.thinkwood.com/en/permalink/catalogue1549
Year of Publication
2016
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Columns
Author
Lacroix, Daniel
Doudak, Ghasan
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Columns
Topic
Mechanical Properties
Keywords
Blast Loads
Static Loads
Dynamic Loads
Dynamic Tests
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 1199-1206
Summary
This paper presents preliminary results from an experimental program investigating the dynamic behaviour of glulam beams and columns subjected to simulated blast loads. A total of eight glulam beams and columns were tested destructively under static and dynamic loads. Based on the dynamic tests conducted on the beams, an increase in strength under dynamic loading, relative to that measured under the static loading, was observed. A material predictive model that accounts for high strain-rate effects is developed. The experimental displacement-time histories were reasonably well predicted through a single-degree-of-freedom approach which used the proposed resistance model as input.
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Behaviour of FRP Retrofitted Glued-Laminated (Glulam) Beams Subjected to Simulated Blast Loads

https://research.thinkwood.com/en/permalink/catalogue1550
Year of Publication
2016
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Lacroix, Daniel
Doudak, Ghasan
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Retrofitted
Static Loads
Dynamic Loads
GFRP
Damage
Predictive Model
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 1207-1214
Summary
Preliminary results from an experimental program investigating the behaviour of retrofitted glulam beams subjected to static and dynamic loads are presented in this paper. The effect of glass fibre-reinforced-polymer (GFRP) laminates applied on the tension side was investigated under both static and dynamic loading as a potential retrofit on undamaged specimens. Furthermore, previously damaged beams were restored by applying GFRP confinement to the damaged region. The experimental results showed that the capacity of the retrofitted beams was improved significantly and the restored beams attained a significant level of their original dynamic capacity. Future work involves the development of a material predictive model that can account for the high-strain rate effects as well as investigating more retrofit options.
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Assessment of Connections in Cross-Laminated Timber Buildings Regarding Structural Robustness

https://research.thinkwood.com/en/permalink/catalogue1948
Year of Publication
2018
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems

Experimental Behaviour of Structural Size Glued Laminated Guadua Bamboo Members

https://research.thinkwood.com/en/permalink/catalogue528
Year of Publication
2014
Topic
Mechanical Properties
Material
Other Materials
Application
Beams
Columns
Author
Correal, Juan
Echeverry, Juan
Yamin, Luis
Ramírez, Fernando
Year of Publication
2014
Country of Publication
Canada
Format
Conference Paper
Material
Other Materials
Application
Beams
Columns
Topic
Mechanical Properties
Keywords
Bending Strength
Flexural Tests
Compression Tests
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
This study presents the experimental evaluation of the behaviour of beams and columns made of Glued Laminated Guadua (GLG) bamboo. Flexural tests were conducted on structural size beams of various span lengths and two lamination orientations (horizontal and vertical) in order to evaluate the different capacities achieved according to the predominant induced stresses, bending or shear. Experimental results indicated a reduction of bending strength as the member’s size increased whereas lamination in the vertical direction presented 12% higher values of modulus of rupture (MOR), and 9% higher values of modulus of elasticity (MOE) compared to equivalent results for lamination in the horizontal direction. Additionally, compression tests were performed on structural size columns with various slenderness ratios and two lamination orientations. Although minor differences were found for lamination orientation, lower capacities were observed as the slenderness ratio increased. This experimental data is expected to be used in order to propose adjustment factors for structural size beams as well as the determination of the column stability factor.
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Behaviours of Larch Glued Laminated Timber Beams Exposed to Standard Fire Heating During the Cooling Phase Study on Fire Performance of Structural Glued Laminated Timber Beams Part 1

https://research.thinkwood.com/en/permalink/catalogue1112
Year of Publication
2015
Topic
Fire
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Kanjo, Hinjin
Hidemasa, Yusa
Horio, Takehito
Hirashima, Takeo
Takumi, Matsumoto
Saito, Kiyoshi
Publisher
J-STAGE
Year of Publication
2015
Country of Publication
Japan
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Fire
Keywords
Larch
Load Bearing Capacity
Charring Rate
Cooling
Language
Japanese
Research Status
Complete
Series
Architectural Institute of Japan Structural System
ISSN
1881-8153
Summary
Timber elements, which are different from other structural elements, have a characteristic problem in that the load bearing capacity decreases due to self-burning in the case of a fire, and this self-burning may continue after other fuel in the room has been exhausted. Therefore, the structural fire performance of timber elements should be clarified during not only the heating phase, but also the cooling phase. However, in examining the load bearing capacity of timber elements in a fire, few studies have considered the cooling phase. In the present paper, the fire performance of glued, laminated timber beams is discussed based on load-bearing fire tests that take the cooling phase into consideration.
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Load Bearing Behaviour of Self-Tapping Screws in Laser-Drilled Guideholes

https://research.thinkwood.com/en/permalink/catalogue1501
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Trautz, Martin
Koj, Christoph
Uchtmann, Hermann
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Topic
Connections
Mechanical Properties
Keywords
Self-Tapping Screws
Laser Drilling
Pull-Out Strength
Guideholes
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 270-277
Summary
Self-tapping screws, used as efficient reinforcements or connectors for timber and glulam structures, tend to “stray” from the designated axis when long and slender screws are applied. To provide a highly precise installation, the predrilling of guideholes using laser radiation has been examined. While laser cutting is already common in machining thin wood-based panels (plywood, chipboard, etc.), laser drilling has not yet been applied for higher drill depths. Based on preliminary tests, pulsed fibre laser radiation was used to drill through glulam species in different angles to the wood fibre direction to examine the geometry and thermal modification of the boreholes. Thereafter self-tapping screws were installed in the laser-drilled guideholes and their pull-out resistance was determined in comparison to screws installed in mechanically drilled holes and screws installed without predrilling. The results of the tests show the high potential for further development of this innovative wood processing method in timber construction.
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Flexural Response of Glued Laminated (Glulam) Beams Subjected to Blast Loads

https://research.thinkwood.com/en/permalink/catalogue492
Year of Publication
2014
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Lacroix, Daniel
Viau, Christian
Doudak, Ghasan
Year of Publication
2014
Country of Publication
Canada
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Strain
Flexural Behaviour
Blast Loads
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
An extensive body of research is currently available on the behaviour of concrete and steel structures when subjected to blast threats, however, little to no details on how to address the design or retrofitting of wood structures are available. In this paper, preliminary results, both experimental and analytical, are presented on the flexural behaviour of glulam beams under high strain rates. A total of three 80 mm x 228 mm x 2,500 mm glulam beams with a clear span of 2,235 mm were subjected to simulated blast loads using a shock tube. The preliminary experimental results showed that a brash tension failure mode was observed on the tension laminate. It was also shown that a simplified SDOF model, using linear elastic resistance curves, was capable of predicting the failure displacement and level of damage with reasonable accuracy.
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10 records – page 1 of 1.