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Design Equations for Dowel Embedment Strength and Withdrawal Resistance for Threaded Fasteners in CLT

https://research.thinkwood.com/en/permalink/catalogue226
Year of Publication
2014
Topic
Connections
Material
CLT (Cross-Laminated Timber)
Author
Kennedy, Shawn
Salenikovich, Alexander
Munoz, Williams
Mohammad, Mohammad
Year of Publication
2014
Country of Publication
Canada
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Keywords
Embedment Strength
Threaded Fasteners
withdrawal resistance
Lag Screws
Self Drilling Screws
Canada
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
The Canadian standard for engineering design in wood (CSA O86) adopted the European yield model for calculations of the lateral resistance of connections with dowel-type fasteners. This model takes into account the yielding resistance of the fastener, the assembly's geometry and the embedment strength of wood. The latter is considered a function of the relative density of wood and diameter of the fastener. The purpose of this study is to verify the significance of these variables as applied to the embedment strength for threaded dowel-type fasteners of diameters 6.4 mm and greater in Canadian glulam products. The importance of this research is justified by the growing interest in the use of large-diameter threaded fasteners in heavy timber and hybrid structures of high load-bearing capacity. Based on the results of 960 tests, a new design model for the embedment strength is proposed for potential implementation in CSA O86 standard and the impact of such a change is presented.
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Experimental Investigations of Shear Connections with Self-Tapping-Screws for Cross-Laminated-Timber Panels

https://research.thinkwood.com/en/permalink/catalogue2295
Year of Publication
2019
Topic
Design and Systems
Connections
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems

The Influences of Moisture Content Variation, Number and Width of Gaps on the Withdrawal Resistance of Self Tapping Screws inserted in Cross Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue1359
Year of Publication
2016
Topic
Connections
Moisture
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Silva, Catarina
Branco, Jorge
Ringhofer, Andreas
Lourenço, Paulo
Schickhofer, Gerhard
Publisher
ScienceDirect
Year of Publication
2016
Country of Publication
Netherlands
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Moisture
Mechanical Properties
Keywords
Withdrawal Tests
Withdrawal Resistance
Self-Tapping Screws
Moisture Content
Gaps
Language
English
Research Status
Complete
Series
Construction and Building Materials
Summary
A large experimental campaign comprised of 470 withdrawal tests was carried out, aiming to quantify the withdrawal resistance of self-tapping screws (STS) inserted in the side face of cross laminated timber (CLT) elements. In order to deeply understand the “CLT-STS” composite model, the experimental tests considered two main parameters: (i) simple and cyclic changes on moisture content (MC) and (ii) number and width of gaps. Regarding (i), three individual groups of test specimens were stabilized with 8%, 12% and 18% of moisture content and one group was submitted to a six month RH cycle (between 30% and 90% RH). Concerning (ii), different test configurations with 0 (REF), 1, 2 and 3 gaps, and widths equal to 0mm (GAP0) or 4mm (GAP4), were tested. The influences of MC and number of gaps were modeled by means of least square method. Moreover, a revision of a prediction model developed by Uibel and Blaß (2007) was proposed. The main findings of the experimental campaign were: the decrease of withdrawal resistance for specimens tested with MC=18% in most configurations; the unexpected increase of withdrawal resistance as the number of gaps with 0mm increased; and, the surprising increase of withdrawal resistance for REF specimens submitted to the RH cycle.
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Prediction of Withdrawal Resistance for a Screw in Hybrid Cross-Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue2687
Year of Publication
2020
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Pang, Sung-Jun
Ahn, Kyung-Sun
Kang, Seog Goo
Oh, Jung-Kwon
Publisher
SpringerOpen
Year of Publication
2020
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Mechanical Properties
Keywords
Self-Tapping Screws
Withdrawal Resistance
Screw
Withdrawal Stiffness
Withdrawal Strength
Connections
Language
English
Research Status
Complete
Series
Journal of Wood Science
Summary
The aim of this study was to predict the withdrawal resistance of a screw in hybrid cross-laminated timber (CLT) composed of two types of lamina layers. A theoretical model to predict the withdrawal resistance was developed from the shear mechanism between a screw and the layers in hybrid CLT. The parameters for the developed model were the withdrawal stiffness and strength that occurs when a screw is withdrawn, and the penetration depth of a screw in layers of a wood material. The prediction model was validated with an experimental test. Screws with two different diameters and lengths (Ø6.5 × 65 mm and Ø8.0 × 100 mm) were inserted in a panel composed of solid wood and plywood layers, and the withdrawal resistances of the screws were evaluated. At least 30 specimens for each group were tested to derive the lower 5th percentile values. As a result, the developed model predictions were 86–88% of the lower 5th percentile values of hybrid CLT from the properties of the lamina layer. This shows that the withdrawal resistance of hybrid CLT can be designed from the properties of its layer.
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Résistance à l’Enfoncement et à l’Arrachement de Connecteurs Filetés Dans le Bois Lamellé-Collé et Lamellé-Croisé (CLT)

https://research.thinkwood.com/en/permalink/catalogue1144
Year of Publication
2014
Topic
Connections
Design and Systems
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Author
Kennedy, Shawn
Organization
Université Laval
Year of Publication
2014
Country of Publication
Canada
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Topic
Connections
Design and Systems
Keywords
dowel embedment strength
Threaded Fasteners
withdrawal resistance
Language
French
English
Research Status
Complete
Summary
Commercial construction has witnessed a new enthusiasm in the use of timber as primary structural material. Engineered wood products such as glued-laminated timber and cross-laminated timber (CLT) play an important part in this development. These products allow wood construction to reach new heights. However, certain gaps in knowledge need to be filled to attain the full potential of wood construction, especially with regards to connections. First, current equations for dowel embedment strength and withdrawal resistance of fasteners in sawn timber and glued-laminated timber are deficient. Secondly, no design methods are provided for dowel embedment strength or withdrawal resistance of fasteners in cross-laminated timber in the 2009 edition of Canadian standard for engineering design in wood CSA O86-09 (2009). For these reasons, the goals of the research project are established in three main objectives: -Develop a design equation for withdrawal resistance for threaded fasteners in sawn timber and glued-laminated timber; -Evaluate the performance of dowel embedment equations for sawn timber and glued-laminated timber from different international standards, and determine the influence of variables on their accuracy; -Develop equations for dowel embedment strength and withdrawal resistance of fasteners in cross-laminated timber. After the compilation of results and analysis of withdrawal and embedment tests with threaded fasteners on sawn timber, glued-laminated and cross-laminated timber, the most accurate design models for each product were proposed. Each proposal includes an impact study showing the influence of the proposed design models, in case of adoption in the next edition of the CSA O86 standard.
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Free
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