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Withdrawal Properties of Threaded Rods Embedded in Glued-Laminated Timber Elements

https://research.thinkwood.com/en/permalink/catalogue217
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Stamatopoulos, Haris
Organization
Norwegian University of Science and Technology
Year of Publication
2016
Country of Publication
Norway
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
Topic
Connections
Mechanical Properties
Keywords
Withdrawal Properties
Threaded Rods
Finite Element Model
Language
English
Research Status
Complete
Summary
There is a complete lack of guidelines for the estimation of the withdrawal stiffness of threaded rods with larger diameters. Moreover, Eurocode 5 imposes a limitation to the angle between the rod-axis and the grain direction (a = 30°) without taking into account that splitting may be prevented by reinforcement. The lack of knowledge of proper design, documentation of mechanical behaviour, design guidelines and design codes for threaded rods are barriers for the development of timber connections with these fasteners. The withdrawal properties (capacity and stiffness) of axially loaded threaded rods were investigated in the present thesis by use of experimental, analytical and numerical methods. An overview of the background information and research on withdrawal of screws and threaded rods is presented in Part I of the present thesis. Part II consists of 4 appended papers where the findings of this Ph.D. project are presented. Part III consists of 3 appendices where some analytical remarks together with the detailed experimental and numerical results are presented. According to experimental observation, the specimens exhibited high withdrawal capacity and stiffness (without initial soft response). Based on the experimental results, the necessary input parameters for the analytical method were quantified. In particular, simple expressions for the mean and 5%-percentile withdrawal strength, the shear stiffness and the brittleness were developed. In general, the analytical estimations and the experimental results were in good agreement. Numerical estimations overestimated stiffness especially for small angles and short embedment lengths; however this overestimation was smaller in the case of longer rods. Finally, the experimental results from tests with pairs of rods showed that the effectiveness per each rod was quite high, despite the fact that rods were placed with small edge distances and spacings.
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Connections with Threaded Rods in Moment Resisting Frames

https://research.thinkwood.com/en/permalink/catalogue1495
Year of Publication
2016
Topic
Mechanical Properties
Connections
Material
CLT (Cross-Laminated Timber)
Application
Frames
Author
Arne Malo, Kjell
Stamatopoulos, Haris
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Frames
Topic
Mechanical Properties
Connections
Keywords
Moment Resistance
Threaded Rods
Beam Column Connection
Rotational Stiffness
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 200-208
Summary
Building owners often state requirements that new buildings shall have open and flexible architecture in order to allow flexible use and future changes. A way to improve timber buildings in that direction is to increase the stiffness of the connections between horizontal and vertical members of the structural systems. This paper presents some numerical and analytical considerations with respect to the stiffness requirements for moment resisting timber connections. It also presents experimental tests and results for a moment resisting connection with inclined threaded rods installed in predrilled holes.
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Effect of Rod-to-Grain Angle on Capacity and Stiffness of Axially and Laterally Loaded Long Threaded Rods in Timber Joints

https://research.thinkwood.com/en/permalink/catalogue1371
Year of Publication
2018
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Cepelka, Martin
Arne Malo, Kjell
Stamatopoulos, Haris
Publisher
Springer Berlin Heidelberg
Year of Publication
2018
Country of Publication
Germany
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Topic
Connections
Mechanical Properties
Keywords
Threaded Rods
Axial Loads
Lateral Loads
Rod-to-Grain
Joints
Boundary Conditions
Load-to-Rod
Language
English
Research Status
Complete
Series
European Journal of Wood and Wood Products
ISSN
1436-736X
Summary
Long threaded rods have recently been widely used as a reinforcement of glued laminated timber in perpendicular to the grain direction. The recent research has thus focused mainly on the withdrawal properties of the threaded rods in the axial direction. Utilizing their large withdrawal stiffness and strength, the threaded rods can also effectively be used as connectors in moment resisting timber joints. Yet, in joints, the threaded rods are often imposed to a non-axial loading, due to inclination of the rod axis to the grain as well as loading direction different from the rod axis. No design models are currently available for the combined axial and lateral loading of the threaded rods. In the present work, the effects of the rod-to-grain and load-to-rod angles on capacity and stiffness of the threaded rods are investigated by use of experiments and finite element models. Based on those, analytical expressions for determining stiffness and capacity of axially and laterally loaded threaded rods are proposed, intended as a basis for practical joint design. Furthermore, effect of various boundary conditions applied at the rod-ends is studied.
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Performance of Self-Tapping Screws and Threaded Steel Rods in Shear Reinforcement of Glulam Beams

https://research.thinkwood.com/en/permalink/catalogue1628
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Jockwer, Robert
Steiger, René
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Connections
Mechanical Properties
Keywords
Norway Spruce
Reinforcement
Self-Tapping Screws
Threaded Steel Rod
Stiffness
Strength
Load Carrying Capacity
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 2813-2822
Summary
Norway spruce glulam beams with artificial horizontal slits of different length and depth were reinforced using self-tapping screws and threaded steel rods in order to restore their load-carrying capacity and stiffness. The study aimed at evaluating the effects of strength and stiffness of the applied reinforcing elements on the load-carrying capacity and stiffness of glulam beams after retrofitting. Self-tapping screws and threaded steel rods of different diameter have been evaluated in the study and different numbers of reinforcing elements have been applied. Shear failure of the beams with artificial slits of different depth was provoked in loading cycles with stepwise installation of the reinforcing elements in the beam parts failed in the preceding test. The reinforcing effect of the tested self-tapping screws and threaded steel rods reached and partly exceeded the estimated level calculated with selected analytical models. Unfavourable structural behaviour arose in some cases from crack opening during installation of the rods causing a very low initial stiffness. Comparison of test results to calculations of stiffness and load-carrying capacity of the reinforced beams applying the -method, the shear analogy method and a truss model revealed that the -method and the shear analogy method provided the best estimates of strength / stiffness of the reinforced beams.
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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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Moment Resisting Frames and Connections Using Threaded Rods in Beam-to-Column Timber Joints

https://research.thinkwood.com/en/permalink/catalogue2001
Year of Publication
2018
Topic
Design and Systems
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Frames
Wood Building Systems

Self-Tapping Screws and Threaded Rods as Reinforcement for Structural Timber Elements - A State-Of-The-Art Report

https://research.thinkwood.com/en/permalink/catalogue448
Year of Publication
2015
Topic
Connections
Serviceability
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Author
Dietsch, Philipp
Brandner, Reinhard
Publisher
ScienceDirect
Year of Publication
2015
Country of Publication
Netherlands
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Topic
Connections
Serviceability
Keywords
Reinforcement
Threaded Rods
Self-Tapping Screws
Shear Stress
Europe
Language
English
Research Status
Complete
Series
Construction and Building Materials
Summary
In timber engineering, self-tapping screws, optimized primarily for axial loading, represent the state-of-the-art in fastener and reinforcement technology. Their economic advantages and comparatively easy handling make them one of the first choices for application in both domains. This paper focuses on self-tapping screws and threaded rods applied as reinforcement, illustrating the state-of-the-art in application and design approaches in Europe, in conjunction with numerous references for background information. With regard to medium to large span timber structures which are predominately erected by using linear timber members, from e.g. glued laminated timber, the focus of this paper is on their reinforcement against stresses perpendicular to grain as well as shear. However, latest findings with respect to cross laminated timber are included as well.
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Bond Behavior Between Softwood Glulam and Epoxy Bonded-In Threaded Steel Rod

https://research.thinkwood.com/en/permalink/catalogue450
Year of Publication
2015
Topic
Design and Systems
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Ling, Zhibin
Liu, Weiqing
Lam, Frank
Yang, Huifeng
Lu, Weidong
Publisher
American Society of Civil Engineers
Year of Publication
2015
Country of Publication
United States
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Topic
Design and Systems
Mechanical Properties
Keywords
Bonding Behavior
Failure Modes
Joints
Load Capacity
Softwood
Threaded Steel Rod
Pull-Pull
Language
English
Research Status
Complete
Series
Journal of Materials in Civil Engineering
Summary
This study aims to develop an improved understanding of the interfacial bond behavior of softwood glulam joints with bonded-in threaded steel rod. A total of 39 glulam joints with bonded-in single-threaded steel rods were tested to failure in the pull-pull configuration. The test results were presented in term of failure modes, load-relative movement response, pullout strength, and the corresponding slip. The distributions of bonded-in rod axial strain, interfacial bond stress, and relative movement were also analyzed to evaluate the local bond stress– relative movement response in the bond line. The results confirmed that the bond-relative movement response is dependent on the locations along the anchorage length, and the bond-relative movement responses located near both the loaded end and the anchorage end were observed to be stiffer than those at other locations. Finally, the predictions for the load capacity of the glulam joints with bonded-in threaded steel rod were carried out based on several existing empirical formulas.
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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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Withdrawal of Axially Loaded Connectors from Timber Elements - Theory and Validation

https://research.thinkwood.com/en/permalink/catalogue639
Year of Publication
2014
Topic
Connections
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Author
Stamatopoulos, Haris
Arne Malo, Kjell
Year of Publication
2014
Country of Publication
Canada
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Topic
Connections
Mechanical Properties
Keywords
Axially Loaded Connectors
Withdrawal Capacity
Stiffness
threaded rods
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
Connections consisting of axially loaded connectors embedded in timber elements can be a strong and competitive alternative to dowel-type connections. Such connections combine high capacity and stiffness. However, especially in the case of screwed-in threaded rods, the up-to date theoretical models and available experimental results are limited. In this paper, a general theoretical model that predicts the withdrawal capacity and stiffness of connections with axially loaded connectors is presented. The model is validated with an experimental study of withdrawal of threaded rods from glulam elements.
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10 records – page 1 of 1.