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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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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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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
Format
Journal Article
Material
Timber-Glass Composite
Application
Shear Walls
Beams
Keywords
Shear Loading
Vertical Loading
Adhesives
Four Point Bending Test
Load Carrying Capacity
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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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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