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Engineers’ Views on Serviceability in Timber Buildings

https://research.thinkwood.com/en/permalink/catalogue858
Year of Publication
2015
Topic
Serviceability
Application
Wood Building Systems
Author
Näslund, Ida
Organization
Luleå University of Technology
Year of Publication
2015
Country of Publication
Sweden
Format
Report
Application
Wood Building Systems
Topic
Serviceability
Keywords
Stabilisation
Stiffness
Deformation
Serviceability Limit State
Mid-Rise
Dynamic Properties
Language
English
Research Status
Complete
Summary
Higher timber buildings are produced around the world. The interest for higher timber buildings has increased. Design in ultimate limit state is well known, but little focus has been put on serviceability limit state especially on higher timber buildings. In this report result from interviews with structural engineers/designers, timber frame suppliers, and development managers are presented. The focus has been on serviceability limit state in mid-rise timber buildings. The experience and knowledge with the respondents varies, which has given a wide perspective of the area
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Timber Concrete Composite Floors with Cross Laminated Timber - Structural Behavior & Design

https://research.thinkwood.com/en/permalink/catalogue2723
Year of Publication
2020
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Application
Floors
Author
Forsberg, Albin
Farbäck, Filip
Publisher
Lund University
Year of Publication
2020
Country of Publication
Sweden
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Floors
Topic
Design and Systems
Keywords
TCC
Timber Composites
Structural Behavior
Design Methods
Gamma Method
Equivalent Gamma Method
Extended Gamma Method
RFEM
First Natural Frequency
Serviceability Limit State
Ultimate Limit State
Language
English
Research Status
Complete
Summary
Due to the increasing environmental awareness, the transition pace to renewable materials has increased, and the use of timber in construction is no exception. However, using timber in high rise building applications comes with structural challenges, e.g dynamic issues originating from timber being lightweight compared to conventional building materials. Some of the structural challenges with timber can be resolved by the implementation of Timber Concrete Composites (TCC), which increases the effective bending stiffness by adding a concrete layer connected to the underlying timber floor. Furthermore, the higher self-weight of concrete contributes to improved dynamic performance. Despite the fact that the TCC floor is a versatile and quite common structural design solution in Europe, the TCC knowledge in the Swedish construction industry is limited. The main scope of the thesis is to raise this knowledge of TCC by studying the structural behavior and develop applicable design methods. Both analytical design methods and FE-modelling are addressed. The content is limited to TCC floors with a 5-layer Cross-Laminated Timber (CLT) section, with use of notches or screws as shear connectors. In CLT design, the Gamma method is commonly used and applicable to a CLT layup up to 5 layers. This method can, by a slight modification, be applicable for TCC sections with a 5-layer CLT as well. The concrete layer on top is regarded as an additional longitudinal layer, flexibly connected to the CLT section. The Equivalent gamma method and the Extended gamma method are two modified versions of the conventional Gamma method, valid for TCC floors with 5-layer CLT sections. Each method determines the effective bending stiffness accurately, compared to FE-modelling and laboratory test results. The Extended gamma method has a more solid theoretical base compared to the Equivalent gamma method, and is considered the recommended design method. The simplified methodology of the Equivalent gamma method is theoretically questionable, hence its recommended use is for preliminary calculations only. The following concluding remarks can be drawn from the analysis of the structural behavior of TCC floors: - The shear connectors should be concentrated to areas of high shear flow, i.e. close to support, for optimal structural performance. - An increased ratio of timber in the longitudinal, load-bearing direction of the CLT section increases the effective bending stiffness of the TCC. - The concrete layer increases the effective bending stiffness due to the high Young's modulus. However, the high density of concrete entails a thin concrete layer thickness to achieve a light-weight and structural efficient TCC system, and the decisive optimisation factor is the ratio of mass-to-effective bending stiffness, m/EI.
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Vibrational Behaviour of Cross Laminated Timber Floors in Residential Buildings

https://research.thinkwood.com/en/permalink/catalogue1738
Year of Publication
2016
Topic
Acoustics and Vibration
Material
CLT (Cross-Laminated Timber)
Application
Floors
Author
Zimmer, Severin
Augustin, Manfred
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Floors
Topic
Acoustics and Vibration
Keywords
Boundary Conditions
Serviceability Limit State
Elastomers
Frequency
In Situ
Laboratory Tests
Residential
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 4835-4844
Summary
This paper will discuss the relevancy of different boundary conditions that relates to the dynamic behaviour of CLT floors to show the opportunities of adopting the findings for the verification of the serviceability limit state. Based on a literature research and measurements in the laboratory and in situ in different objects the evaluated boundary conditions are different static systems, supporting conditions, non-load bearing internal walls, flexible carriers, joints between CLT elements, elastomers and floor constructions. Furthermore a theoretical investigation on the low frequency behaviour of floating screeds was conducted. Abstracted from the results it can be stated that elastomers can generally be neglected in their influence on low frequency vibration modes except when the partial clamping due to the load of superimposed storeys at the supports should be taken into account. The effect of partial clamping on low frequency vibration can be calculated adequately but is lowered if elastomers are used to improve the building physics. A big influence was observed at non-load bearing internal walls as they are able to change the eigenmodes of a floor into ones with higher frequency. Overall the laboratory measurements agreed well with the analytic solutions while differences in comparison of calculations with in situ measurements rise with the complexity of the boundary conditions.
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