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7 records – page 1 of 1.

Ambient Vibration Testing and Modal Analysis of Multi-Storey Cross Laminated Timber Buildings

https://research.thinkwood.com/en/permalink/catalogue237
Year of Publication
2014
Topic
Acoustics and Vibration
Wind
Serviceability
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Reynolds, Thomas
Bolmsvik, Åsa
Vessby, Johan
Chang, Wen-Shao
Harris, Richard
Bawcombe, Jonathan
Bregulla, Julie
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Acoustics and Vibration
Wind
Serviceability
Keywords
Modal Properties
Multi-Storey
Damping
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
The ambient movement of three modern multi-storey timber buildings has been measured and used to determine modal properties. This information, obtained by a simple, unobtrusive series of tests, can give insights into the structural performance of these forms of building, as well as providing information for the design of future, taller timber buildings for dynamic loads. For two of the buildings, the natural frequency has been related to the lateral stiffness of the structure, and compared with that given by a simple calculation. In future tall timber buildings, a new design criterion is expected to become important: deflection and vibration serviceability under wind load. For multi-storey timber buildings there is currently no empirical basis to estimate damping for calculation of wind-induced vibration, and there is little information for stiffness under wind load. This study therefore presents a method to address those gaps in knowledge.
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Ambient Vibration Tests of a Cross-Laminated Timber Building

https://research.thinkwood.com/en/permalink/catalogue313
Year of Publication
2015
Topic
Wind
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Shear Walls
Author
Reynolds, Thomas
Harris, Richard
Chang, Wen-Shao
Bregulla, Julie
Bawcombe, Jonathan
Publisher
ICE Publishing
Year of Publication
2015
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Shear Walls
Topic
Wind
Keywords
Damping
Dynamic Movement
In Situ
Multi-Storey
Stiffness
Modal Properties
Ambient Vibration Method
Research Status
Complete
Series
Proceedings of the Institution of Civil Engineers - Construction Materials
Summary
Cross-laminated timber has, in the last 6 years, been used for the first time to form shear walls and cores in multi-storey buildings of seven storeys or more. Such buildings can have low mass in comparison to conventional structural forms. This low mass means that, as cross-laminated timber is used for taller buildings still, their dynamic movement under wind load is likely to be a key design parameter. An understanding of dynamic lateral stiffness and damping, which has so far been insufficiently researched, will be vital to the effective design for wind-induced vibration. In this study, an ambient vibration method is used to identify the dynamic properties of a seven-storey cross-laminated timber building in situ. The random decrement method is used, along with the Ibrahim time domain method, to extract the modal properties of the structure from the acceleration measured under ambient conditions. The results show that this output-only modal analysis method can be used to extract modal information from such a building, and that information is compared with a simple structural model. Measurements on two occasions during construction show the effect of non-structural elements on the modal properties of the structure.
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Building Higher with Light-Weight Timber Structures: The Effect of Wind Induced Vibrations

https://research.thinkwood.com/en/permalink/catalogue89
Year of Publication
2015
Topic
Acoustics and Vibration
Wind
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Author
Johansson, Marie
Linderholt, Andreas
Bolmsvik, Åsa
Jarnerö, Kirsi
Olsson, Jörgen
Reynolds, Thomas
Organization
Inter-noise
Year of Publication
2015
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Topic
Acoustics and Vibration
Wind
Keywords
Mid-Rise
High-Rise
Vibration Properties
Conference
Inter-noise 2015
Research Status
Complete
Notes
August 9-12, 2015, San Francisco, California, USA
Summary
During the last years the interest in multi-storey timber buildings has increased and several medium-to-high-rise buildings with light-weight timber structure have been designed and built. Examples of such are the 8-storey building Limnologen in Växjö, Sweden, the 9- storey Stadthaus in London, UK and being constructed at the moment, the 14-storey building Treet in Bergen, Norway. These are all light-weight and flexible structures which raise questions regarding the wind induced vibrations. For the building in Norway, the calculated vibration properties of the top floor are on the limit of being acceptable according to the ISO 101371 vibration criteria for human comfort. This paper will give a review of building systems for medium-to-high-rise timber buildings. Measured vibration properties for some medium-to-high-rise timber buildings will also be presented. These data have been used for calculating the peak acceleration values for two example buildings for comparison with the ISO standards. An analysis of the acceleration levels for a building with double the height has also been performed showing that designing for wind induced vibrations in higher timber buildings is going to be very important and that more research into this area is needed.
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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
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
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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Lateral-Load Resistance of Cross-Laminated Timber Shear Walls

https://research.thinkwood.com/en/permalink/catalogue1238
Year of Publication
2017
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Author
Reynolds, Thomas
Foster, Robert
Bregulla, Julie
Chang, Wen-Shao
Harris, Richard
Ramage, Michael
Publisher
American Society of Civil Engineers
Year of Publication
2017
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Shear Walls
Topic
Connections
Mechanical Properties
Keywords
Vertical Load
Lateral Load
Pullout Tests
Steel Connectors
Offset-Yield Criterion
Research Status
Complete
Series
Journal of Structural Engineering
Summary
Cross-laminated timber shear wall systems are used as a lateral load resisting system in multistory timber buildings. Walls at each level typically bear directly on the floor panels below and are connected by nailed steel brackets. Design guidance for lateral load resistance of such systems is not well established and design approaches vary among practitioners. Two cross-laminated two-story timber shear wall systems are tested under vertical and lateral load, along with pull-out tests on individual steel connectors. Comprehensive kinematic behavior is obtained from a combination of discrete transducers and continuous field displacements along the base of the walls, obtained by digital image correlation, giving a measure of the length of wall in contact with the floor below. Existing design approaches are evaluated. A new offset-yield criterion based on acceptable permanent deformations is proposed. A lower bound plastic distribution of stresses, reflecting yielding of all connectors in tension and cross-grain crushing of the floor panel, is found to most accurately reflect the observed behavior.
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Free
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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
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
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.
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Free
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Wind-Induced Vibration of Tall Wood Buildings

https://research.thinkwood.com/en/permalink/catalogue1105
Year of Publication
2011
Topic
Wind
Connections
Material
Glulam (Glue-Laminated Timber)
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Reynolds, Thomas
Chang, Wen-Shao
Harris, Richard
Organization
TRADA
Year of Publication
2011
Format
Report
Material
Glulam (Glue-Laminated Timber)
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Wind
Connections
Keywords
Across-Wind Vibration
Turbulence
Along-Wind Vibration
Vortex Shedding
Research Status
Complete
Summary
Wind-induced vibration is an important design consideration in tall buildings in any structural material. The two main forms of wind-induced vibration - across-wind vibration due to vortex shedding and along-wind vibration due to turbulence - were taken into consideration when undertaking this study. Both types are addressed in Eurocode 1. This research summary discusses a study which, following a sensitivity study into the effect of stiffness and damping on wind-induced vibration, addresses a shortfall in current knowledge of stiffness in dowel-type connections. This type of connection is found in the glulam frame and CLT structures currently at the forefront of tall timber construction, and its behaviour was investigated by measuring and analysing stiffness and damping under oscillating loads representative of wind-induced vibration. This research summary covers a number of factors relating to wind-induced vibration which must be considered when constructing a tall timber building, such as how to assess connection stiffness under in-service vibration. The various conditions were then applied to a case study - the proposed Barentshaus building.
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7 records – page 1 of 1.