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Adhesive Bonding of Structural Hardwood Elements

https://research.thinkwood.com/en/permalink/catalogue75
Year of Publication
2015
Topic
Mechanical Properties
Serviceability
Moisture
Material
Glulam (Glue-Laminated Timber)
CLT (Cross-Laminated Timber)
Author
Hassani, Mohammad
Organization
ETH Zurich
Year of Publication
2015
Format
Thesis
Material
Glulam (Glue-Laminated Timber)
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Serviceability
Moisture
Keywords
Abaqus
Adhesives
Beech
Bonding
Delamination
Finite Element Model
Fracture
Long-term
Model
Hardwood
Research Status
Complete
Summary
The current research investigated the delamination process of adhesively bonded hardwood (European beech) elements subject to changing climatic conditions. For the study of the long-term fracture mechanical behavior of gluedlaminated components under varying moisture content, the role of moisture development, time- and moisture-dependent responses are absolutely crucial. For this purpose, a 3D orthotropic hygro-elastic, plastic, visco-elastic, mechano-sorptive wood constitutive model with moisture-dependent material constants was presented in this work. Such a comprehensive material model is capable to capture the true historydependent stress states and deformations which are essential to achieve reliable design of timber structures. Besides the solid wood substrates, the adhesive material also influences the interface performance considerably. Hence, to gain further insight into the stresses and deformations generated in the bond-line, a general hygro-elastic, plastic, visco-elastic creep material model for adhesive was introduced as well. The associated numerical algorithms developed on the basis of additive decomposition of the total strain were formulated and implemented within the Abaqus Finite Element (FE) package. Functionality and performance of the proposed approach were evaluated by performing multiple verification simulations of wood components, under different combinations of mechanical loading and moisture variation. Moreover, the generality and efficiency of the presented approach was further demonstrated by conducting an application example of a hybrid wood element.
Online Access
Free
Resource Link
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Analysis of Hygroscopic Self-Shaping Wood at Large Scale for Curved Mass Timber Structures

https://research.thinkwood.com/en/permalink/catalogue2162
Year of Publication
2019
Topic
Design and Systems
Material
CLT (Cross-Laminated Timber)
Author
Grönquist, Philippe
Wood, Dylan
Hassani, Mohammad
Wittel, Falk
Menges, Achim
Rüggeberg, Markus
Organization
ETH Zurich
University of Stuttgart
Publisher
American Association for the Advancement of Science
Year of Publication
2019
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Topic
Design and Systems
Keywords
Moisture Content
Architecture
Self-Shaping
Research Status
Complete
Series
Science Advances
Summary
The growing timber manufacturing industry faces challenges due to increasing geometric complexity of architectural designs. Complex and structurally efficient curved geometries are nowadays easily designed but still involve intensive manufacturing and excessive machining. We propose an efficient form-giving mechanism for large-scale curved mass timber by using bilayered wood structures capable of self-shaping by moisture content changes. The challenge lies in the requirement of profound material knowledge for analysis and prediction of the deformation in function of setup and boundary conditions. Using time- and moisture-dependent mechanical simulations, we demonstrate the contributions of different wood-specific deformation mechanisms on the self-shaping of large-scale elements. Our results outline how to address problems such as shape prediction, sharp moisture gradients, and natural variability in material parameters in light of an efficient industrial manufacturing.
Online Access
Free
Resource Link
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