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Analysis and Tests of Lateral Resistance of Bolted and Screwed Connections of CLT

https://research.thinkwood.com/en/permalink/catalogue2956
Year of Publication
2022
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Huo, Liangliang
Zhu, Enchun
Niu, Shuang
Wu, Guofang
Organization
Harbin Institute of Technology
China Academy of Forestry
Editor
Ozarska, Barbara
Monaco, Angela
Publisher
MDPI
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Mechanical Properties
Connections
Keywords
Lateral Resistance
European Yield Model
Bolt Connection
Screw Connectors
Emdedment Stress
Research Status
Complete
Series
Forests
Summary
The lateral resistance of dowel-type connections with CLT is related to its lay-up, species of the laminations and even the manufacture method. Treating the CLT as homogeneous material, current methods develop new equations through test results or make use of the existing equations for the embedment strength already used in design codes; thus, the lateral resistance of dowel-type connections of CLT can be calculated. This kind of approach does not take the embedment stress distribution into account, which may lead to inaccuracy in predicting the lateral resistance and yield mode of the dowel-type connections in CLT. In this study, tests of the bolted connections and the screwed connections of CLT were conducted by considering the effects of the orientation of the laminations, the thickness of the connected members, the fastener diameter and strength of the materials. The material properties including yield strength of the fasteners and embedment strength of the CLT laminations were also tested. Using analysis of the dowel-type connections of CLT by introducing the equivalent embedment stress distribution, equations for the lateral resistance of the connections based on the European Yield Model were developed. The predicted lateral resistance and yield modes were in good agreement with the test results; the correctness and the feasibility of the equations were thus validated.
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High-cycle fatigue behaviour of a timber-to-timber connection with self-tapping screws under lateral loading

https://research.thinkwood.com/en/permalink/catalogue2936
Year of Publication
2021
Topic
Mechanical Properties
Application
Wood Building Systems
Author
Niebuhr, Peter
Sieder, Mike
Organization
iBHolz Technische Universität Braunschweig
Publisher
Springer
Year of Publication
2021
Format
Journal Article
Application
Wood Building Systems
Topic
Mechanical Properties
Keywords
Self-Tapping Screws
European Yield Model
Fatigue Behaviour
Research Status
Complete
Series
European Journal of Wood and Wood Products
Summary
The high-cycle fatigue behaviour of a timber-to-timber connection with self-tapping screws is examined with the fasteners under bending due to their alignment lateral to the load direction. The cyclic tests were carried out with a sinusoidal non-reversed load (R=0.1) with a loading frequency of 5 Hz. The examined connection is designed for the quasistatic failure mechanism with two plastic hinges per shear plane according to Johansen’s theory (European Yield Model), which is mirrored in the observed fatigue failure. Based on 30 cyclic tests on four nominal stress levels (S={0.47,0.41,0.31,0.20}) in the finite-life regime the respective Wöhler-curve is obtained, showing high conformity with the test data due to a consideration of the specific density of the individual specimens. It is shown that the examined fasteners show a superior fatigue behaviour under bending compared to axial loading. A simple safe-side approach for the application of Wöhler-curves for axial loading of threaded fasteners to the present case of fastener bending is proposed, extending the field of possible applications for the results of existing and future studies of the behaviour under axial loading.
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Influence of different types of reinforcements on the embedment behavior of steel dowels in wood

https://research.thinkwood.com/en/permalink/catalogue3082
Year of Publication
2016
Topic
Mechanical Properties
Connections
Author
Lederer, Wolfgang
Bader, Thomas K.
Unger, Gerhard
Eberhardsteiner, Josef
Organization
Vienna University of Technology
Publisher
Springer
Year of Publication
2016
Format
Journal Article
Topic
Mechanical Properties
Connections
Keywords
Dowel-Type Connection
Embedment Strength
European Yield Model
Research Status
Complete
Series
European Journal of Wood and Wood Products
Summary
In this study, dowel displacement-embedment stress relationships for different types, numbers and positions of reinforcements were experimentally investigated using a half-hole embedment test setup. Tests were performed parallel to the grain and in compression. Screws with a full or partial thread at different positions below the dowel and oriented strand board, plywood and nail plates on the loaded surfaces of the specimens, served as reinforcements. Test results underline their potential for an increased ductility of dowel-type connections. Comparison of reinforced and unreinforced specimens suggests premature failure of the unreinforced wood and consequently, an underestimation of the embedment strength as it is subsequently used in the design of dowel connections using the European yield model. This was supported by the investigation of cracks on the surface of the specimens visualized by means of a full-field deformation measurement system. It could be demonstrated that the strength in the embedment test even further increases if the reinforcement elements actively contribute to the load transfer. This property however cannot be considered as embedment strength, but represents the strength of a connection system. Test data is compared to the design equation in Eurocode 5.
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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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