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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
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Knot Clusters
Non-Destructive
Tensile tests
Load Carrying Capacity
Joints
Model
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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UT System : A Structural System to Build Taller Urban Timber Houses with Aspired Spatial Flexibility

https://research.thinkwood.com/en/permalink/catalogue277
Year of Publication
2014
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Author
Silva, Catarina
Branco, Jorge
Lourenço, Paulo
Organization
International Association for Housing Science
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Topic
Design and Systems
Keywords
Urban Densification
Tall Timber
Urban Timber (UT) System
Moisture
Durability
Fire Resistance
Acoustic Performance
Joints
Conference
40th IAHS World Congress on Housing
Research Status
Complete
Notes
December 16-19, 2014, Funchal, Portugal
Summary
In past few years, in consequence to the continuous increase of urban densities and seeking for a more sustainable profile for construction, some new proposals for tall timber city housing have emerged. The development of new wood-based materials, like cross laminated timber (CLT), has made possible to believe to build high with timber. Demonstration buildings located in different locations around the world contribute to the development of this new concept of urban housing. With the exception of few recent proposals based on hybrid systems, majority of buildings so far built are fully based in the monolithic construction system offered by CLT panels. Despite all the advantages related with this monolithic system, two main important weaknesses related with architectural freedom have been pointed out: the excessive compartmentalization of inner spaces and the external expression of an extruded box with reduced openings. Inspired on new CLT/steel and CLT/concrete hybrid proposals and their advantages in comparison to the CLT monolithic system, a CLT/glulam hybrid construction system, named UT system (urban timber system), has been developed. CLT remains the main structural material in the UT system but, glulam linear elements are used to reduce the CLT walls both inside and in the building perimeter. Further, based in the bundled tube concept, UT system looks into the possibility of overcome eccentricity problems caused by non-symmetrical location of vertical cores and consequently, offers more design freedom. UT system is described and illustrated, considering concerns related with structural system, tall building specificities, construction sequences, architectural design possibilities, moisture effects, durability, fire resistance, acoustic performance and joints between timber elements.
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New Design Approach for Wood Brittle Failure Mechanisms in Timber Connections

https://research.thinkwood.com/en/permalink/catalogue317
Year of Publication
2014
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
LVL (Laminated Veneer Lumber)
Author
Zarnani, Pouyan
Quenneville, Pierre
Year of Publication
2014
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
LVL (Laminated Veneer Lumber)
Topic
Connections
Mechanical Properties
Keywords
Joints
Fasteners
European Yield Model
New Zealand
Ductile
Brittle
Failure Mechanisms
Conference
Australasian Structural Engineering Conference
Research Status
Complete
Notes
July 9-11, 2014, Auckland, New Zealand
Summary
Timber construction has experienced considerable progress in recent years. In such progress, apart from the implementation of new engineered timber products, the advancement of timber joints has played a significant role. The design procedures for timber connections in most design codes are based mainly on the yielding capacity of the fasteners using the European Yield Model (EYM). While the EYM theory provides accurate predictions for connections that fail in a ductile fashion, it does not take into account the failure of the connections due to the brittle rupture of wood as the consequence of fasteners group effect. Such a significant gap in the design of connections also applies to the New Zealand (NZS 3603) and Australian (AS 1720.1) timber design standards. A new design approach is presented which allows the practitioners to predict the connection capacity associated with different brittle wood failure mechanisms. An extensive testing regime has been conducted on high load-transfer capacity joints using timber rivets under longitudinal and transverse loadings on New Zealand Radiata Pine laminated veneer lumber (LVL) and glulam. The results verify the proposal and prove its reliability. A design guide was also developed which could eventually become a design clause in the next revision of the New Zealand timber design standard NZS 3603.
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Racking Resistance and Ductility of CLT Shear Walls Under Horizontal and Vertical Loads

https://research.thinkwood.com/en/permalink/catalogue457
Year of Publication
2014
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Yasumura, Motoi
Ito, Yoshimasa
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Mechanical Properties
Connections
Keywords
Yield Load
Ultimate Load
Failure Modes
Joints
Hold-Down
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
The determination procedure of the failure mechanism of CLT shear walls due to the failure of joints was presented in the 45th CIB-W18 meeting in Vaxjo1. It showed that the reliability based analysis based on the ultimate capacity of fasteners predicted quite well the failure process of shear walls when a rigid loading beam was applied. However, the failure process due to the failure of hold-down connectors was not very clear when the flexible loading beam was used. Therefore additional lateral loading tests were conducted by using flexible loading beam as shown in Fig.1 with different procedures to determine the failure mode. This new procedure based on the yield strength of shear plates and the ultimate capacity of hold-down connectors showed better determination of the failure mechanism of CLT shear walls without conspicuous slips between CLT panels. This paper shows the racking test results of CLT shear walls with different failure modes. The failure modes of shear walls were designed by using reliability analysis considering the failure of the hold down connections at the bottom end of shear wall and that of the joints connecting two CLT panels at the centre of the wall. It was shown that the design of joints with the yield capacity Py for the central joints SP and the ultimate capacity Pu for the hold down connection HD (Mode III) determined well the precedence of HD failure without slips in SP and showed high capacity, while Modes I and II failure showed higher ductility than Mode III failure.
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Screwed Joints in Cross Laminated Timber Structures

https://research.thinkwood.com/en/permalink/catalogue508
Year of Publication
2014
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Walls
Author
Flatscher, Georg
Bratulic, Katarina
Schickhofer, Gerhard
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Walls
Topic
Connections
Mechanical Properties
Keywords
Joints
Cyclic Tests
Monotonic Tests
Screws
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
Approximately 60% of all joints in solid timber structures assembled with Cross Laminated Timber (CLT) are realised with screws. Although, the behaviour of axially loaded self-tapping single screws is already well known, only minor experiences are available regarding the behaviour of screwed wall joints. Furthermore, since seismic resistance of CLT structures depends to a great amount on the connections’ ability to dissipate energy, it is important to extend the knowledge on their behaviour more thoroughly. This paper gives a brief overview of the results obtained from experimental monotonic and cyclic tests that were carried out not only on screwed CLT single joints, but also on wall tests with screwed joints. Additionally, the question on modelling the behaviour of a screwed wall joint based on the behaviour of a single screw will be discussed within the present contribution as well. Aforementioned tests are part of an extensive ongoing study investigated at the Graz University of Technology, Institute of Timber Engineering and Wood Technology (TU Graz) and at the competence centre holz.bau forschungs gmbh (hbf).
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Moment Resistance of Post-And-Beam Joints with Concealed Metallic Connectors

https://research.thinkwood.com/en/permalink/catalogue621
Year of Publication
2014
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Humbert, Jérôme
Lee, Sang-Joon
Park, Joo-Saeng
Park, Moon-Jae
Year of Publication
2014
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Connections
Mechanical Properties
Keywords
Moment Resistance
Post and Beam
Joints
Metallic Connectors
Monotonic
Reverse Cyclic Loading
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
This paper presents a study on the moment resistance of post-and-beam joints with concealed metallic connectors aimed at replacing in a more modern design the wood-wood joints of traditional Korean Hanok timber houses. Several variations of the design of the connectors are investigated to optimize the moment resistance of the joints. Experimental tests are conducted under monotonic and reversed cyclic loading. The performance of the joint is evaluated in terms of peak moment resistance, as well as ductility and energy dissipation. Results show that optimization in the design can improve the moment resistance of the joint while preventing the brittle wood fracture and favoring a more ductile plasticizing of the connector, for the benefit of safety.
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Development of CLT Shear Frame Using Metal Plate Insert Connections

https://research.thinkwood.com/en/permalink/catalogue697
Year of Publication
2014
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Kitamori, Akihisa
Nakashima, Shoichi
Isoda, Hiroshi
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Connections
Mechanical Properties
Keywords
Failure Mode
Joints
Steel Plate
Strength
Steel Connectors
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
The purpose of this study is to develop a high strength leg joint for shear wall made of small size cross laminated timber panel in a simple system. The joint of CLT in which steel plate was inserted in the central slit and fixed by high strength bolt at inside of short steel pipes was proposed. In order to grasp the failure mode and strength of CLT member, material tests on embedment and shear were carried out using small CLT blocks. The test results indicated that there is few reinforce effect by cross bonding of each lamina. It was concluded that the precise estimation of the strength of CLT member is important in order to develop the joint proposed in this paper.
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Shear Properies of Timber-to-Timber Joints with Large Size Self-Tapping Screws

https://research.thinkwood.com/en/permalink/catalogue1003
Year of Publication
2014
Topic
Connections
Material
CLT (Cross-Laminated Timber)
Author
Kobayashi, Kenji
Yasumura, Motoi
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Keywords
self-tapping screw
Shear Tests
Joints
Timber-to-Timber
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
Cross Laminated Timber (CLT) is a new material for midrise timber structures. CLT panels made of Japanese species like Sugi (Cryptomeria japonica D.Don) are developed in Japan. Seismic resistance of CLT structures are mainly determined by the performances of panel-to-panel connections. One of the main fasteners for CLT connections is large size self-tapping screws. It is possible to use not only CLT panels but also glulam structures. But there are few data for these joints and not used so much in Japan. In this study, shear tests of timbet-to-timber joints including CLT panels with large size self-tapping screws and several material tests were conducted. And estimating equations of single shearing properties were validated. In this study, shear tests of timbet-to-timber joints including CLT panels with large size self-tapping screws and several material tests were conducted. And estimating equations of single shearing properties were validated. Estimation curves were fitted well with test curves. It is confirmed that estimating equations are valid for timber-to-timber connections of large size self-tapping screws.
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Study on Shear Performance of CLT Joints Using Long Vise Part 2 Result of Experiments, Consideration and Conclusion

https://research.thinkwood.com/en/permalink/catalogue1008
Year of Publication
2014
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Author
Township, Onishi
Nasu, Hideyuki
Karibe, Yuki
Organization
Architectural Institute of Japan
Year of Publication
2014
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Topic
Connections
Mechanical Properties
Keywords
Floor-Wall Connection
Joints
Mid-Rise
Shear Test
Fracture Behavior
Long Vise
Research Status
Complete
Summary
Innovative steel - Cross Laminated Timber (CLT) connections are key elements in developing hybrid steeltimber composite floors with desirable strength and serviceability performance. The performance of floors mainly relies on the load-slip behavior of connections for composite action. The long-term behavior of timber is mainly affected by elastic and mechano-sorptive creep, resulting in a different total slip than the initially observed one. In this study, the long-term load-slip behavior of two different types of connections with pre-tensioned high-strength bolts and dog screws are experimentally assessed at two different stress levels. Furthermore, the effect of grain orientation on the results is studied by considering specimens with parallel and perpendicular grain orientations under sustained loads. Load-slip curves show a stable performance of a composite action over time. Furthermore, an analytical model is fitted to the loadslip vs time data which can be used to predict long-term behavior of floors in future.
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Study on Shear Performance of CLT Joints Using Long Vise Part 1 Summary of Experiments and Test Pieces

https://research.thinkwood.com/en/permalink/catalogue1009
Year of Publication
2014
Topic
Connections
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Author
Nasu, Hideyuki
Township, Onishi
Karibe, Yuki
Organization
Architectural Institute of Japan
Year of Publication
2014
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Topic
Connections
Keywords
Floor-Wall Connection
Mid-Rise
Shear Test
Fracture Behavior
Long Vise
Joints
Research Status
Complete
Summary
Innovative steel - Cross Laminated Timber (CLT) connections are key elements in developing hybrid steeltimber composite floors with desirable strength and serviceability performance. The performance of floors mainly relies on the load-slip behavior of connections for composite action. The long-term behavior of timber is mainly affected by elastic and mechano-sorptive creep, resulting in a different total slip than the initially observed one. In this study, the long-term load-slip behavior of two different types of connections with pre-tensioned high-strength bolts and dog screws are experimentally assessed at two different stress levels. Furthermore, the effect of grain orientation on the results is studied by considering specimens with parallel and perpendicular grain orientations under sustained loads. Load-slip curves show a stable performance of a composite action over time. Furthermore, an analytical model is fitted to the loadslip vs time data which can be used to predict long-term behavior of floors in future.
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41 records – page 1 of 5.