Thesis
Cross-laminated strand-veneer composite mass timber panels for building construction
Washington State University
Master of Science (MS), Washington State University
2023
DOI:
https://doi.org/10.7273/000004975
Abstract
Cross-laminated timber (CLT) is gaining popularity for use in building mid-rise buildings. The variations in grain patterns and growth rings in the wood laminates cause differential shrinking and swelling behavior in CLT, which could result in delamination at the glue line. Additionally, the shear stress acting on the radial-tangential plane perpendicular to grain or rolling shear stress often results in premature failure. Another challenge in mass timber construction using CLT is to protect it from exposure to a high moisture environment and ensure long-term durability. To mitigate these issues, this study proposes to utilize thermally modified wood strands in a commercial autoclave to manufacture cross-laminated strand veneer lumber (CLSVL) that is durable and dimensionally stable. In the first part of the study, wood strands were hydrothermally treated in a closed inert environment with nitrogen gas at various temperatures (165°C, 170°C, and 180°C) and pressures (0.8 MPa and 1.4 MPa) with a constant dwelling time of 120 minutes. It was found that the lower pressure of 0.8 MPa decreased the boiling point of water in a high-temperature environment, which helped to increase the rate of extraction of hemicellulose from the wood resulting in a 35% reduction in equilibrium moisture content (EMC). Similarly, a 38% reduction in thickness swelling at 165°C & 0.8 MPa was obtained for thermally modified (TM) veneers while maintaining mechanical properties, implying a significant improvement in dimensional stability.
In the second part of the study, CLSVL manufactured from thermally modified strands (165°C and 0.8MPa for 120 minutes) were evaluated for mechanical and physical properties. No significant differences were observed for effective bending stiffness, shear stiffness, bending resistance, and shear resistance of control and thermally modified (TM) panels. The shear analogy model (SAM) showed good predictions of mechanical properties. Better dimensional stability with a 25% reduction in water absorption and a 59% reduction in thickness swell was observed for TM-CLSVL panels without rolling shear failure for both flexural and shear specimens.
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Details
- Title
- Cross-laminated strand-veneer composite mass timber panels for building construction
- Creators
- Rajan Adhikari
- Contributors
- Vikram Yadama (Advisor)Donald Bender (Committee Member)Karl Englund (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 134
- Identifiers
- 99901019839001842
- Language
- English
- Resource Type
- Thesis