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Design of Connections in Timber Structures

https://research.thinkwood.com/en/permalink/catalogue1937
Year of Publication
2018
Topic
Connections
Design and Systems
Material
CLT (Cross-Laminated Timber)
Author
Bader, Thomas
Blaß, Hans Joachim
Bocquet, Jean-François
Branco, Jorge
Brandner, Reinhard
Manuel Cabrero, José
de Proft, Kurt
Descamps, Thierry
Dietsch, Philipp
Franke, Bettina
Franke, Steffen
Görlacher, Rainer
Jockwer, Robert
Jorissen, André
Kleiber, Marion
Lemaître, Romain
Munch-Andersen, Jørgen
Pazlar, Tomaž
Ranasinghe, Keerthi
Ringhofer, Andreas
Sandhaas, Carmen
Schweigler, Michael
Stepinac, Mislav
Tuhkanen, Eero
Verbist, Maxime
Yurrita, Miguel
Editor
Sandhaas, Carmen
Munch-Andersen, Jørgen
Dietsch, Philipp
Publisher
COST (European Cooperation in Science and Technology)
Year of Publication
2018
Format
Book/Guide
Material
CLT (Cross-Laminated Timber)
Topic
Connections
Design and Systems
Keywords
Eurocode 5
Fasteners
Screws
Dowel Type Fastener
Glued-In Rods
Numerical Modeling
Europe
Load Distribution
Research Status
Complete
Summary
This state-of-the-art report has been prepared within COST Action FP1402 Basis of structural timber design from research to standards, Working Group 3 Connections. The Action was established to create an expert network that is able to develop and establish the specific information needed for standardization committee decisions. Its main objective is to overcome the gap between broadly available scientific results and the specific information needed by standardization committees. This necessitates an expert network that links practice with research, i.e. technological developments with scientific background. COST presents the ideal basis to foster this type of joint effort. Chapter 8 Connections presents an integral part of Eurocode 5 and is in need of revision. This state-of-the-art report shall provide code writers with background information necessary for the development of the so-called Second Generation of the Eurocodes, now aimed to be produced in 2022.
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Development of Creep Deformations during Service Life: A Comparison of CLT and TCC Floor Constructions

https://research.thinkwood.com/en/permalink/catalogue2955
Year of Publication
2022
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Timber-Concrete Composite
Application
Floors
Author
Binder, Eva
Derkowski, Wit
Bader, Thomas
Organization
Linnæus University
Editor
Brandner, Reinhard
Publisher
MDPI
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Timber-Concrete Composite
Application
Floors
Topic
Mechanical Properties
Keywords
Serviceability Limit State
Gamma Method
Linear Viscoelasticity
Research Status
Complete
Series
Buildings
Summary
Cross-laminated timber (CLT) slabs in residential buildings need additional weight, e.g., in the form of screeds or gravel layers, to fulfill the criterion for the highest impact-sound class. The additional mass is, however, not exploited for the load bearing behavior, but adds additional weight and leads to an increased height of the floor construction. In this study, such a CLT floor construction with a construction height of 380 mm is compared with a composite slab consisting of a CLT plate with a concrete layer on top with a floor construction height of 330 mm. The timber concrete composite (TCC) slab has a different creep behavior than the CLT slab. Thus, the development of the time-dependent deflections over the service life are of interest. A straightforward hybrid approach is developed, which exploits advanced multiscale-based material models for the individual composite layers and a standardized structural analysis method for the structural slab to model its linear creep behavior. The introduced approach allows to investigate load redistribution between the layers of the composite structure and the evolution of the deflection of the slab during the service life. The investigated slab types show a similar deflection after 50 years, while the development of the deflections over time are different. The CLT slab has a smaller overall stiffness at the beginning but a smaller decrease in stiffness over time than the investigated TCC slab.
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Dowel Deformations in Multi-Dowel LVL-Connections Under Moment Loading

https://research.thinkwood.com/en/permalink/catalogue583
Year of Publication
2015
Topic
Connections
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
Author
Bader, Thomas
Schweigler, Michael
Hochreiner, Georg
Serrano, Erik
Enquist, Bertil
Dorn, Michael
Publisher
Taylor&Francis Online
Year of Publication
2015
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Topic
Connections
Mechanical Properties
Keywords
Ductility
Bending Moment
Steel Dowels
Double-Shear
Steel-to-Timber
Four Point Bending Test
Research Status
Complete
Series
Wood Material Science & Engineering
Summary
The aim of the experimental study presented herein is the assessment and quantification of the behavior of individual dowels in multi-dowel connections loaded by a bending moment. For this purpose, doubleshear, steel-to-timber connections with nine steel dowels arranged in different patterns and with different dowel diameters were tested in 4-point bending. In order to achieve a ductile behavior with up to 7° relative rotation, the connections were partly reinforced with self-tapping screws. The reinforcement did not influence the global load-deformation behavior, neither for dowel diameters of 12 mm nor for 20 mm, as long as cracking was not decisive. The deformation of the individual dowels was studied by means of a non-contact deformation measurement system. Thus, the crushing deformation, i.e. the deformation at the steel plate, and the bending deformation of the dowels could be quantified. In case of 12 mm dowels, the bending deformation was larger than the crushing deformation, while it was smaller in case of 20 mm dowels. Moreover, dowels loaded parallel to the grain showed larger bending deformations than dowels loaded perpendicular to the grain. This indicates that the loading of the individual dowels in the connection differs, depending on their location.
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Exploring the synergy between structural engineering design solutions and life cycle carbon footprint of cross-laminated timber in multi-storey buildings

https://research.thinkwood.com/en/permalink/catalogue2864
Year of Publication
2021
Topic
Environmental Impact
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Dodoo, Ambrose
Nguyen, Truong
Dorn, Michael
Olsson, Anders
Bader, Thomas
Organization
Linnaeus University
Publisher
Taylor&Francis Group
Year of Publication
2021
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Environmental Impact
Keywords
Life Cycle Analysis
Climate Impacts
Structural Design
Multi-Storey
Research Status
Complete
Series
Wood Material Science & Engineering
Summary
Low-carbon buildings and construction products can play a key role in creating a low-carbon society. Cross-laminated timber (CLT) is proposed as a prime example of innovative building products, revolutionising the use of timber in multi-storey construction. Therefore, an understanding of the synergy between structural engineering design solutions and climate impact of CLT is essential. In this study, the carbon footprint of a CLT multi-storey building is analysed in a life cycle perspective and strategies to optimise this are explored through a synergy approach, which integrates knowledge from optimised CLT utilisation, connections in CLT assemblies, risk management in building service-life and life cycle analysis. The study is based on emerging results in a multi-disciplinary research project to improve the competitiveness of CLT-based building systems through optimised structural engineering design and reduced climate impact. The impacts associated with material production, construction, service-life and end-of-life stages are analysed using a process-based life cycle analysis approach. The consequences of CLT panels and connection configurations are explored in the production and construction stages, the implications of plausible replacement scenarios are analysed during the service-life stage, and in the end-of-life stage the impacts of connection configuration for post-use material recovery and carbon footprint are analysed. The analyses show that a reduction of up to 43% in the life cycle carbon footprint can be achieved when employing the synergy approach. This study demonstrates the significance of the synergy between structural engineering design solutions and carbon footprint in CLT buildings.
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Influence of different types of reinforcements on the embedment behavior of steel dowels in wood

https://research.thinkwood.com/en/permalink/catalogue3082
Year of Publication
2016
Topic
Mechanical Properties
Connections
Author
Lederer, Wolfgang
Bader, Thomas K.
Unger, Gerhard
Eberhardsteiner, Josef
Organization
Vienna University of Technology
Publisher
Springer
Year of Publication
2016
Format
Journal Article
Topic
Mechanical Properties
Connections
Keywords
Dowel-Type Connection
Embedment Strength
European Yield Model
Research Status
Complete
Series
European Journal of Wood and Wood Products
Summary
In this study, dowel displacement-embedment stress relationships for different types, numbers and positions of reinforcements were experimentally investigated using a half-hole embedment test setup. Tests were performed parallel to the grain and in compression. Screws with a full or partial thread at different positions below the dowel and oriented strand board, plywood and nail plates on the loaded surfaces of the specimens, served as reinforcements. Test results underline their potential for an increased ductility of dowel-type connections. Comparison of reinforced and unreinforced specimens suggests premature failure of the unreinforced wood and consequently, an underestimation of the embedment strength as it is subsequently used in the design of dowel connections using the European yield model. This was supported by the investigation of cracks on the surface of the specimens visualized by means of a full-field deformation measurement system. It could be demonstrated that the strength in the embedment test even further increases if the reinforcement elements actively contribute to the load transfer. This property however cannot be considered as embedment strength, but represents the strength of a connection system. Test data is compared to the design equation in Eurocode 5.
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Load Distribution in Multi-Dowel Timber Connections Under Moment Loading - Integrative Evaluation of Multiscale Experiments

https://research.thinkwood.com/en/permalink/catalogue1499
Year of Publication
2016
Topic
Connections
Mechanical Properties
Material
LVL (Laminated Veneer Lumber)
Author
Bader, Thomas
Schweigler, Michael
Hochreiner, Georg
Eberhardsteiner, Josef
Year of Publication
2016
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Topic
Connections
Mechanical Properties
Keywords
Load Distribution
Steel Dowels
Steel Plates
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 244-252
Summary
The load distribution in multi-dowel timber connections under bending moments was investigated by means of an integrative evaluation of a hierarchically organized test program, which encompassed component tests as well as single-dowel and multi-dowel connection tests. It was demonstrated that the anisotropic material behaviour of Laminated Veneer Lumber, and consequently of wood in general, leads to a non-uniform load distribution among the dowels, even for multi-dowel connections with a circular arrangement of dowels. Model predictions from this study highlight inefficiencies of the simplified calculation approach, based on the polar moment of inertia, i.e., based on isotropic theory. Loads of dowels loaded parallel to the grain were found to be underestimated by up to 50%. Through the hierarchically organized experimental campaign with full-field deformation measurement techniques, load distribution effects could be related to the orthotropic material behaviour of wood expressed in terms of load-to-grain angle dependent slip curves of single-dowel connections.
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A Numerical Study of the Stiffness and Strength of Cross-Laminated Timber Wall-to-Floor Connections under Compression Perpendicular to the Grain

https://research.thinkwood.com/en/permalink/catalogue2839
Year of Publication
2021
Topic
Connections
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Walls
Floors
Author
Akter, Shaheda
Schweigler, Michael
Serrano, Erik
Bader, Thomas
Organization
Linnaeus University
Lund University
Editor
Brandner, Reinhard
Publisher
MDPI
Year of Publication
2021
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Walls
Floors
Topic
Connections
Mechanical Properties
Keywords
Parametric Study
Perpendicular to the Grain
Elasto-Plastic Behaviour
Numerical Modeling
Research Status
Complete
Series
Buildings
Summary
The use of cross-laminated timber (CLT) in multi-story buildings is increasing due to the potential of wood to reduce green house gas emissions and the high load-bearing capacity of CLT. Compression perpendicular to the grain (CPG) in CLT is an important design aspect, especially in multi-storied platform-type CLT buildings, where CPG stress develops in CLT floors due to loads from the roof or from upper floors. Here, CPG of CLT wall-to-floor connections are studied by means of finite element modeling with elasto-plastic material behavior based on a previously validated Quadratic multi-surface (QMS) failure criterion. Model predictions were first compared with experiments on CLT connections, before the model was used in a parameter study, to investigate the influence of wall and floor thicknesses, the annual ring pattern of the boards and the number of layers in the CLT elements. The finite element model agreed well with experimental findings. Connection stiffness was overestimated, while the strength was only slightly underestimated. The parameter study revealed that the wall thickness effect on the stiffness and strength of the connection was strongest for the practically most relevant wall thicknesses between 80 and about 160 mm. It also showed that an increasing floor thickness leads to higher stiffness and strength, due to the load dispersion effect. The increase was found to be stronger for smaller wall thicknesses. The influence of the annual ring orientation, or the pith location, was assessed as well and showed that boards cut closer to the pith yielded lower stiffness and strength. The findings of the parameter study were fitted with regression equations. Finally, a dimensionless ratio of the wall-to-floor thickness was used for deriving regression equations for stiffness and strength, as well as for load and stiffness increase factors, which could be used for the engineering design of CLT connections.
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7 records – page 1 of 1.