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Nonlinear Pre-Yield Modal Properties of Timber Structures with Large-Diameter Steel Dowel Connections

https://research.thinkwood.com/en/permalink/catalogue132
Year of Publication
2014
Topic
Connections
Acoustics and Vibration
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Frames
Author
Harris, Richard
Reynolds, Thomas
Chang, Wen-Shao
Publisher
ScienceDirect
Year of Publication
2014
Country of Publication
Netherlands
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Frames
Topic
Connections
Acoustics and Vibration
Keywords
Dowel-Type Connection
Modal Analysis
Cyclic Loading
Energy Dissipation
Language
English
Research Status
Complete
Series
Engineering Structures
Summary
In timber structures, the connections are generally flexible in comparison to the members they connect, and so contribute significantly to the dynamic properties of the structure. It is shown here that a widely-used form of connection, the dowel-type connection, exhibits nonlinear stiffness and energy dissipation, even at pre-yield loads, and that this nonlinearity affects the modal properties of structures with such connections. This study investigates that behaviour by modal analysis of a portal frame and a cantilever beam constructed from timber with steel dowel connections. The observed nonlinearity is explained qualitatively by considering the measured force-displacement response of individual connectors under cyclic load, which show a reduction in stiffness and an increase in energy dissipation with increasing amplitude of vibration. The structures were tested by modal analysis under slow sine sweep and pseudo-random excitation. Under pseudo-random excitation, a linear single degree-of-freedom curve fit was applied to estimate the equivalent linear modal properties for a given amplitude of applied force. Under slow sine sweep excitation, the frequency response function for the structures was observed to show features similar to a system with a cubic component of stiffness, and the modal properties of the structures were extracted using the equation of motion of such a system. The consequences for structural design and testing are that two key design parameters, natural frequency and damping, vary depending on the magnitude of vibration, and that parameters measured during in-situ testing of structures may be inaccurate for substantially different loads.
Online Access
Free
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Dynamic Behaviour of Dowel-Type Connections Under In-Service Vibration

https://research.thinkwood.com/en/permalink/catalogue884
Year of Publication
2013
Topic
Connections
Serviceability
Acoustics and Vibration
Material
Solid-sawn Heavy Timber
Application
Frames
Beams
Author
Reynolds, Thomas
Organization
University of Bath
Year of Publication
2013
Country of Publication
United Kingdom
Format
Thesis
Material
Solid-sawn Heavy Timber
Application
Frames
Beams
Topic
Connections
Serviceability
Acoustics and Vibration
Keywords
dowel-type connections
Embedment
Nonlinear Behaviour
Time Dependent Behaviour
Energy Dissipation
Portal Frames
Language
English
Research Status
Complete
Summary
This study investigated the vibration serviceability of timber structures with dowel-type connections. It addressed the use of such connections in cutting-edge timber structures such as multi-storey buildings and long-span bridges, in which the light weight and flexibility of the structure make it possible that vibration induced by dynamic forces such as wind or footfall may cause discomfort to occupants or users of the structure, or otherwise impair its intended use. The nature of the oscillating force imposed on connections by this form of vibration was defined based on literature review and the use of established mathematical models. This allowed the appropriate cyclic load to be applied in experimental work on the most basic component of a dowel-type connection: a steel dowel embedding into a block of timber. A model for the stiffness of the timber in embedment under this cyclic load was developed based on an elastic stress function, which could then be used as the basis of a model for a complete connector. Nonlinear and time-dependent behaviour was also observed in embedment, and a simple rheological model incorporating elastic, viscoelastic and plastic elements was fitted to the measured response to cyclic load. Observations of the embedment response of the timber were then used to explain features of the behaviour of complete single- and multiple-dowel connections under cyclic load representative of in-service vibration. Complete portal frames and cantilever beams were tested under cyclic load, and a design method was derived for predicting the stiffness of such structures, using analytical equations based on the model for embedment behaviour. In each cyclic load test the energy dissipation in the specimen, which contributes to the damping in a complete structure, was measured. The analytical model was used to predict frictional energy dissipation in embedment, which was shown to make a significant contribution to damping in single-dowel connections. Based on the experimental results and analysis, several defining aspects of the dynamic response of the complete structures, such as a reduction of natural frequency with increased amplitude of applied load, were related to the observed and modelled embedment behaviour of the connections.
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Free
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Experimental Testing of Load-Bearing Timber–Glass Composite Shear Walls and Beams

https://research.thinkwood.com/en/permalink/catalogue860
Year of Publication
2015
Material
Timber-Glass Composite
Application
Shear Walls
Beams
Author
Kozlowski, Marcin
Dorn, Michael
Serrano, Erik
Publisher
Taylor&Francis Online
Year of Publication
2015
Country of Publication
United Kingdom
Format
Journal Article
Material
Timber-Glass Composite
Application
Shear Walls
Beams
Keywords
Shear Loading
Vertical Loading
Adhesives
Four Point Bending Test
Load Carrying Capacity
Language
English
Research Status
Complete
Series
Wood Material Science & Engineering
Summary
The paper presents results from the experimental testing of load-bearing timber–glass composite shear walls and beams. Shear wall specimens measuring 1200 × 2400 mm2 manufactured with three adhesives of varying stiffness were tested. Twelve specimens with a single 10 mm thick glass pane and one specimen with an additional insulating glass unit were produced. The testing procedures involved various loading conditions: pure vertical load and different combinations of shear and vertical loading. The test results showed that the adhesive had only a minor influence on the buckling load which was the main failure mechanism. 240 mm high and 4800 mm long timber–glass beams manufactured with adhesives of different stiffness were tested. For the webs, two types of glass were used: annealed float and heat-strengthened glass, in both cases 8 mm thick panes were used. In total, 12 beams were tested in four-point bending until failure. Despite the considerable difference in adhesive stiffness, beam bending stiffness was similar. Concerning load-bearing capacity, the beams with heat-strengthened glass were approximately 50% stronger than the beams made using annealed float glass.
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Free
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NMIT Arts & Media Building - Damage Mitigation Using Post-Tensioned Timber Walls

https://research.thinkwood.com/en/permalink/catalogue1850
Year of Publication
2018
Topic
Design and Systems
Seismic
Material
LVL (Laminated Veneer Lumber)
Application
Floors
Walls
Columns
Beams
Wood Building Systems
Author
Devereux, Carl
Holden, Tony
Buchanan, Andrew
Pampanin, Stefano
Publisher
New Zealand Timber Design Society
Year of Publication
2018
Country of Publication
New Zealand
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Application
Floors
Walls
Columns
Beams
Wood Building Systems
Topic
Design and Systems
Seismic
Keywords
Earthquake
Structural
Shear
Post-Tensioning
Language
English
Research Status
Complete
Series
New Zealand Timber Design Journal
Online Access
Free
Resource Link
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