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15 records – page 1 of 2.

An experimental 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/catalogue3197
Year of Publication
2022
Topic
Connections
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Author
Schweigler, Michael
Akter, Shaheda T.
Sabaa, Stephen
Bader, Thomas K.
Organization
Linnaeus University
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Floors
Walls
Topic
Connections
Keywords
Compression Perpendicular To Grain
Stress Dispersion
Nominal Stiffness
Nominal Strength
Digital Image Correlation
Research Status
Complete
Series
Engineering Structures
Summary
In platform-type multi-story cross-laminated timber (CLT) buildings, gravity loads from upper floors, and vertical reaction forces from horizontal actions, like wind loads, cause substantial compressive forces in the CLT-floor elements. The combination of these high forces with a comparable low compression stiffness and strength perpendicular to the grain of timber, makes the compression perpendicular to the grain (CPG) verification of CLT an important design criterion. In this experimental study, CPG of CLT was investigated by means of typical wall-to-floor connections in CLT platform-type structures. CLT-wall elements were used for load application to transmit forces through the CLT-floor element by CPG. Compared to load application by steel elements, as it commonly is done in experiments, lower stiffness but similar strength were found for CLT walls. The study of different connection types showed the highest stiffness and strength for connections assembled with screws, followed by pure wood-to-wood contact, while connections with acoustic layers between the floor and wall elements showed the lowest stiffness and strength. In addition, these connections were tested for center and edge load position on the CLT-floor element. The strength for center and edge position compared to full surface loaded specimens increased linearly with the activated material volume, as determined by earlier proposed stress dispersion models. The stress dispersion effect was visualized by surface strain measurements using digital image correlation technique. Also, the stiffness increased with the activated material volume. Stress dispersion in the CLT-floor allowed to explain the increase in stiffness and strength with decreasing CLT-wall thickness. Strength values at different strain levels, and stiffness and strength increase factors suitable for the engineering design of CLT structures are provided.
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An innovative timber-steel hybrid beam consisting of glulam mechanically reinforced by means of steel rod: Analytical and preliminary numerical investigations

https://research.thinkwood.com/en/permalink/catalogue3135
Year of Publication
2021
Topic
Mechanical Properties
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Author
Wang, Tianxiang
Wang, Yue
Crocetti, Roberto
Franco, Luca
Schweigler, Michael
Wålinder, Magnus
Organization
KTH royal institute of technology
Univiersità IUAV di Venezia
Linnaeus University
Publisher
Elsevier
Year of Publication
2021
Format
Journal Article
Material
Glulam (Glue-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Hybrid Structure
Mechanical Connection
Shear Key
Timber-Steel Hybrid Beam
Analytical Model
Numerical Analysis
Retrofitting Techniques
Research Status
Complete
Series
Journal of Building Engineering
Summary
There is an increasing interest in large-dimensional timber structural elements within the construction sector in order to fulfil the combined demand of sustainability, open spaces and architectural flexibility. Current timber technology allows for efficient production of long-size beams, but many problems are related to their overall high costs due to difficulties in transportation, manufacturing on site and handling during the mounting phase. Hence, the aim of this work is to propose and study an innovative timber-steel hybrid structural element composed of shorter pieces of beams connected and reinforced by means of a system consisting of steel shear keys and steel rods. The small timber elements and steel devices can be prefabricated with low costs and easily assembled into large elements at the construction sites. The proposed system can also be used for retrofitting of existing timber members when it is necessary to increase their strength, stiffness and ductility. The structural behavior of the proposed system was therefore studied both as a connection and as a retrofitting technique, which were analyzed via two types of hybrid beams, one with a splice at mid-span and one without, separately. A simple glulam beam with the same geometrical characteristics of the two hybrid structures was also investigated for the comparison of the structural behavior. The analytical results show that the hybrid beams with and without splice have both obtained significant increasement in the stiffness, strength and ductility. The numerical analyses are limited in the elastic stage due to the elastic mechanical properties assigned to the structural components. The numerical results show good agreement with the analytical ones for each type of beam in terms of the stiffness in the elastic stage. Finally, the influence of the parameters such as the distance between shear keys, slip modulus of shear keys and diameter of rod, on the structural behavior of hybrid beams is discussed in this paper.
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Cross-laminated timber for building construction: A life-cycle-assessment overview

https://research.thinkwood.com/en/permalink/catalogue3002
Year of Publication
2022
Topic
Environmental Impact
Material
CLT (Cross-Laminated Timber)
Author
Younis, Adel
Dodoo, Ambrose
Organization
Linnaeus University
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Environmental Impact
Keywords
Carbon Footprint
Life Cycle Assessment
Climate Change
Sustainable Multi-story Construction
Research Status
Complete
Series
Journal of Building Engineering
Summary
The building industry is a large contributor to greenhouse gas (GHG) emissions and a vast consumer of natural resources. It is estimated that, in the next 40 years, around 415 Gt of CO2 will be released as a result of global construction activities. Therefore, improvements in construction technologies are essential to reduce GHG emissions and thereby attain national and international goals to mitigate climate change. Cross-laminated timber (CLT) has emerged as an innovative alternative material to steel/concrete in building construction, given its relatively low carbon footprint, not to mention its high strength-to-weight ratio, simple installation, and aesthetic features. CLT is a structural composite panel product developed in the early 1990s, and the contemporary generation of CLT buildings are yet to reach the end of their service life. Accordingly, there has been growing interest to understand and optimize the performance of CLT in building construction. In view of that, this paper presents an overview on the feasibility of using CLT in buildings from a life-cycle assessment (LCA) standpoint. The authors performed a brief review on LCA studies conducted in the past decade pertaining to the carbon footprint of CLT buildings. On average, the findings of these studies revealed about 40% reduction in carbon footprint when using CLT in lieu of conventional construction materials (steel/concrete) for multi-story buildings. Furthermore, the paper explores the challenges associated with conducting LCA on CLT buildings, identifies the gaps in knowledge, and outlines directions for future research.
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Determination of Coefficients of Friction for Laminated Veneer Lumber on Steel under High Pressure Loads

https://research.thinkwood.com/en/permalink/catalogue2822
Year of Publication
2021
Topic
Connections
Material
LVL (Laminated Veneer Lumber)
Application
Wood Building Systems
Author
Dorn, Michael
Habrova, Karolina
Koubek, Radek
Serrano, Erik
Organization
Linnaeus University
Czech University of Life Sciences Prague
Lund University
Publisher
Springer Nature
Year of Publication
2021
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Application
Wood Building Systems
Topic
Connections
Keywords
Static Friction
High Pressure
Angle-to-grain
Moisture Content
Steel
Research Status
Complete
Series
Friction
Summary
In this study, static coefficients of friction for laminated veneer lumber on steel surfaces were determined experimentally. The focus was on the frictional behaviors at different pressure levels, which were studied in combination with other influencing parameters: fiber orientation, moisture content, and surface roughness. Coefficients of friction were obtained as 0.10–0.30 for a smooth steel surface and as high as 0.80 for a rough steel surface. Pressure influenced the measured coefficients of friction, and lower normal pressures yielded higher coefficients. The influence of fiber angle was observed to be moderate, although clearly detectable, thereby resulting in a higher coefficient of friction when sliding perpendicular rather than parallel to the grain. Moist specimens contained higher coefficients of friction than oven-dry specimens. The results provide realistic values for practical applications, particularly for use as input parameters of numerical simulations where the role of friction is often wrongfully considered.
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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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Dynamical Properties of a Large Glulam Truss for a Tall Timber Building

https://research.thinkwood.com/en/permalink/catalogue2036
Year of Publication
2018
Topic
Wind
Mechanical Properties
Connections
Material
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Trusses
Author
Landel, Pierre
Linderholt, Andreas
Johansson, Marie
Organization
Linnaeus University
Year of Publication
2018
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems
Trusses
Topic
Wind
Mechanical Properties
Connections
Keywords
Dynamic Properties
Finite Element (FE) Model
Vibration Test
Conference
World Conference on Timber Engineering
Research Status
Complete
Summary
When designing a tall timber building, the accelerations due to wind loads are in many cases decisive. The parameters governing the dynamic behaviour of the building are the structure's stiffness, damping and mass together with the loads. The first two parameters are not well-known during the serviceability limit state of timber structures generally and of timber connections specifically. In this study, dynamical properties of a large glulam truss, a part of the vertical and horizontal structural system in a residential six-storey timber building, are estimated from measurements made in the manufacturing plant. The timber members of the truss are joined with slotted-in steel plates and dowels. Forced vibrational test data are used to extract the dynamical properties. Finite element (FE) models, supported by the experimental results, were developed and simulations, to study the influence of the connection stiffnesses on the total behaviour, were performed. The vibration test results of measurements made on separate structural parts give valuable input to model timber structures and better possibilities to simulate the dynamic behaviour of tall timber buildings as well as the load distribution in wooden structures in the serviceability limit state.
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Dynamic Response of Tall Timber Buildings Under Service Load - The DynaTTB Research Program

https://research.thinkwood.com/en/permalink/catalogue3015
Year of Publication
2020
Topic
Acoustics and Vibration
Application
Wood Building Systems
Author
Abrahamsen, Rune
Bjertnæs, Magne
Bouillot, Jacques
Brank, Bostjan
Cabaton, Lionel
Crocetti, Roberto
Flamand, Olivier
Garains, Fabien
Gavric, Igor
Germain, Olivier
Hahusseau, Ludwig
Hameury, Stephane
Johansson, Marie
Johansson, Thomas
Ao, Wai Kei
Kurent, Blaž
Landel, Pierre
Linderholt, Andreas
Malo, Kjell
Manthey, Manuel
Nåvik, Petter
Pavic, Alex
Perez, Fernando
Rönnquist, Anders
Stamatopoulos, Haris
Sustersic, Iztok
Tulebekova, Saule
Organization
Norwegian University of Science and Technology
University of Exeter
University of Ljubljana
Linnaeus University
Year of Publication
2020
Format
Conference Paper
Application
Wood Building Systems
Topic
Acoustics and Vibration
Keywords
Timber Building
Wind Load
Discomfort
Modelling
Damping
Full Scale
Conference
International Conference on Structural Dynamics
Research Status
Complete
Summary
Wind-induced dynamic excitation is becoming a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and measured to estimate their key dynamic properties (natural frequencies and damping), no systematic evaluation of dynamic performance pertinent to wind loading has been performed for the new and evolving construction technology used in TTBs. The DynaTTB project, funded by the Forest Value research program, mixes on site measurements on existing buildings excited by heavy shakers, for identification of the structural system, with laboratory identification of building elements mechanical features coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and provide key elements to FE modelers. The first building, from a list of 8, was modelled and tested at full scale in December 2019. Some results are presented in this paper. Four other buildings will be modelled and tested in spring 2021.
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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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Long-term analysis of the environmental effects on the global dynamic properties of a hybrid timber-concrete building

https://research.thinkwood.com/en/permalink/catalogue3188
Year of Publication
2022
Topic
Acoustics and Vibration
Material
Timber-Concrete Composite
Author
Larsson, Carl
Abdeljaber, Osama
Bolmsvik, Åsa
Dorn, Michael
Organization
Linnaeus University
Publisher
Elsevier
Year of Publication
2022
Format
Journal Article
Material
Timber-Concrete Composite
Topic
Acoustics and Vibration
Keywords
Structural Health Monitoring
Ambient Vibration Monitoring
Environmental Monitoring
Research Status
Complete
Series
Engineering Structures
Summary
With the increased availability of timber materials, such as cross-laminated timber, the number of buildings using timber as a structural material has been rapidly increasing. As these buildings are new to the market, limited data and research on their long-term structural modal performance are available. This is particularly important in timber buildings since the material properties of wood are highly affected by environmental factors, especially the moisture content. Over time, the evolution of the dynamic properties is essential for damage indication in structural health monitoring systems since natural changes can mask the influence of damage. This work presents three years of observations from a structural monitoring system collecting data ever since completing a four-story timber-concrete hybrid building in Sweden. Ambient vibrations of the building were measured using geophones, resulting in 3,100 datasets. The temperature and relative humidity were measured both externally using a weather station and internally using sensors embedded in several walls and a slab in the building. The observed natural frequencies of the building vary with ± 0.2 Hz around the mean value over time. Linear regression analysis shows a significant correlation between the moisture content of a cross-laminated timber slab and the natural frequencies (coefficient of determination up to 0.84). A predictive model for the natural frequencies is presented, taking seasonal variations and a dry-out of the structure into account. Variations from the expected values are ± 0.1 Hz at most. The model clearly narrows the error margins for damage indication in a structural health monitoring system.
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Modular multi-storey construction with cross-laminated timber: Life cycle environmental implications

https://research.thinkwood.com/en/permalink/catalogue3266
Year of Publication
2022
Topic
Environmental Impact
Material
CLT (Cross-Laminated Timber)
Author
Al-Najjar Ahmad
Dodoo, Ambrose
Organization
Linnaeus University
Publisher
Taylor&Francis Online
Year of Publication
2022
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Environmental Impact
Keywords
Modular Construction
Carbon Footprint
Life Cycle Assessment
Research Status
Complete
Series
Wood Material Science & Engineering
Summary
In this study, the life cycle environmental implications of modular multi-storey building with cross-laminated timber (CLT) volumetric elements are analysed, considering the product, construction, service life, end-of-life and post-use stages. A bottom-up attributional approach is used to analyse the environmental flows linked to the global warming potential (GWP), acidification potential (AP) and eutrophication potential (EP) impacts of the building for a 50-year reference study period. The result shows that the building’s life cycle impacts can vary considerably, depending on the energy production profile for the operation of the building. The product, construction and end-of-life stages constitute a significant share of the life cycle impacts, and the importance of these stages increase as the energy production profile evolves towards a low-carbon energy mix. For the GWP, the product and construction stages constitute 13% of the total life cycle impact when the operational energy is based on a coal-based marginal electricity. The contribution of this stage increases to 81% when electricity is based on a plausible long-term Swedish average mix. The patterns of the life cycle EP and AP impacts are also closely linked to the energy production profile for the assessment. The analysis shows that a 5% reduction in the GWP impact in the product stage is achievable with emerging solutions for the improved structural design of CLT buildings. This study highlights the need for strategies to improve the life cycle environmental profile of modular CLT buildings.
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15 records – page 1 of 2.