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Development of Novel Standardized Structural Timber Elements Using Wood-Wood Connections

https://research.thinkwood.com/en/permalink/catalogue2747
Year of Publication
2020
Topic
Design and Systems
Connections
Material
CLT (Cross-Laminated Timber)
Author
Gamerro, Julien
Publisher
Lausanne, EPFL
Year of Publication
2020
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Topic
Design and Systems
Connections
Keywords
Timber Construction
Connections
Digital Fabrication
Design for Manufacturing and Assembly
Structural Design
Structural Frameworks
Semi-Rigid Connection
Experimental
Shear Strength
Compression Strength
Wood-Wood Connections
Bending Test
Bending Stiffness
Numerical Model
Load Carrying Capacity
Slip Modulus
Language
English
Research Status
Complete
Summary
Traditional wood-wood connections, widely used in the past, have been progressively replaced by steel fasteners and bonding processes in modern timber constructions. However, the emergence of digital fabrication and innovative engineered timber products have offered new design possibilities for wood-wood connections. The design-to-production workflow has evolved considerably over the last few decades, such that a large number of connections with various geometries can now be easily produced. These connections have become a cost-competitive alternative for the edgewise connection of thin timber panels. Several challenges remain in order to broaden the use of this specific joining technique into common timber construction practice: (1) prove the applicability at the building scale, (2) propose a standardized construction system, (3) develop a convenient calculation model for practice, and (4) investigate the mechanical behavior of wood-wood connections. The first building implementation of digitally produced through-tenon connections for a folded-plate structure is presented in this work. Specific computational tools for the design and manufacture of more than 300 different plates were efficiently applied in a multi-stakeholder project environment. Cross-laminated timber panels were investigated for the first time, and the potential of such connections was demonstrated for different engineered timber products. Moreover, this work demonstrated the feasibility of this construction system at the building scale. For a more resilient and locally distributed construction process, a standardized system using through-tenon connections and commonly available small panels was developed to reconstitute basic housing components. Based on a case-study with industry partners, the fabrication and assembly processes were validated with prototypes made of oriented strand board. Their structural performance was investigated by means of a numerical model and a comparison with glued and nailed assemblies. The results showed that through-tenon connections are a viable alternative to commonly used mechanical fasteners. So far, the structural analysis of such construction systems has been mainly achieved with complex finite element models, not in line with the simplicity of basic housing elements. A convenient calculation model for practice, which can capture the semi-rigid behavior of the connections and predict the effective bending stiffness, was thus introduced and subjected to large-scale bending tests. The proposed model was in good agreement with the experimental results, highlighting the importance of the connection behavior. The in-plane behavior of through-tenon connections for several timber panel materials was characterized through an experimental campaign to determine the load-carrying capacity and slip modulus required for calculation models. Based on the test results, existing guidelines were evaluated to safely apply these connections in structural elements while a finite element model was developed to approximate their performance. This work constitutes a firm basis for the optimization of design guidelines and the creation of an extensive database on digitally produced wood-wood connections. Finally, this thesis provides a convenient design framework for the newly developed standardized timber construction system and a solid foundation for research into digitally produced wood-wood connections.
Online Access
Free
Resource Link
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Identifying Incipient Decay in Douglas-fir Bridge Components using X-Ray Computerized Tomography

https://research.thinkwood.com/en/permalink/catalogue2350
Year of Publication
2019
Topic
Design and Systems
Moisture
Serviceability
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Application
Bridges and Spans
Author
Senalik, Christopher
Wacker, James
Wang, Xiping
Wu, Xi
Year of Publication
2019
Country of Publication
United States
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Solid-sawn Heavy Timber
Application
Bridges and Spans
Topic
Design and Systems
Moisture
Serviceability
Keywords
X-ray Computerized Tomography
Wood Timber
Brown Rot Fungus
Incipient Decay
Language
English
Conference
International Nondestructive Testing and Evaluation of Wood Symposium
Research Status
Complete
Summary
In this report, wooden members of sizes typically used in bridge construction are examined using x-ray computerized tomography (CT) to determine the presence of internal decay. This report is part of an overall study in which Douglas-fir (Pseudotsuga menziesii) glue-laminated (glulam) beams and solid sawn timbers were inoculated with brown rot fungus, Fomitopsis pinicola, and exposed to aboveground conditions approximately 25 miles (40 km) north of Gulfport, Mississippi, USA. The goal of the overall study is to develop interior decay within the test specimens and then identify and characterize the decay using a variety of nondestructive testing (NDT) techniques. One NDT technique used is x-ray CT. The pixel brightness (PB) of CT scan images is proportional to the specific gravity (SG) at that location; high SG materials appear brighter whereas low SG materials appear darker. The consumption of wood by fungus decreases the wood SG; however, fungal progression takes place in areas where sufficient moisture is present. The presence of moisture increases wood SG as detected by the CT scan, which masks the effect of the fungal decay, which is a common co-occurrence with many NDT techniques. To identify incipient decay, it is necessary to examine the ring structure both within and outside of the area of moisture. Quantifying the extent of the decay requires correlating the PB to known SG values for both dry wood and wood of varying moisture content. In this report, the relationship between wood SG, moisture content, and PB was quantified.
Online Access
Free
Resource Link
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