Validation of the Heat and Moisture Transfer within Wooden Building Assemblies under Fire Exposure and its Mechanical Impact on the Building Structure

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H00798
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 23:Architecture, building engineering, and related fields
• Research Institution: Waseda University
• Principal Investigator: Hasemi Yuji 早稲田大学, 理工学術院, 名誉教授 (40298138)
• Co-Investigator(Kenkyū-buntansha): 鍵屋 浩司 東北工業大学, 建築学部, 教授 (90298191) ; 伯耆原 智世 早稲田大学, 理工学術院, 専任講師 (70908061) ; 板垣 直行 秋田県立大学, システム科学技術学部, 教授 (00271891)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 大規模木造 / 火災 / 力学的性能 / 熱・水分移動 / 含水率 / 入射熱

Outline of Final Research Achievements

The limit for the measurement of moisture content of wooden members has been expanded to the extent that changes in moisture content could be traced from air-drying conditions at ambient temperature to the end of standard fire-resistance test. Thermal conductivity of wood at high temperature at different fiber directions was measured for the development of heat/moisture transfer model, resulting in the extremely strong anisotropy in the fiber directions; it strongly suggests that the transfer of water in axial direction of a wooden load bearing member can affect its mechanical performance. From these results, several mysteries in the fire behavior of wood such as the fact that the relationship between the deformation and span of wooden beams during a fire tends to be different from that of steel or concrete, and the inconsistency between the charring rate and the mechanical performance of wood during fire heating have been found to be caused by moisture transfer due to fire heating.

Free Research Field

建築学

Academic Significance and Societal Importance of the Research Achievements

実用化が期待されている火災加熱下の木材の含水率測定法については、実際的な火災加熱条件下で常温から沸点まで、更に自然冷却の過程までの動的測定が可能となった。この成果は今後の木質部材の耐火性能予測に関する研究の推進に多大な影響を及ぼすと考える。火災加熱下の木造部材における熱水分移動モデルについて、高温での熱伝導率の異方性が顕著なこと、熱分解時に発熱を伴うことなど、新しい知見を得た。これらを通じ、従来、原因不明だった火災加熱下での木造部材の特異な挙動のいくつかについて原因を明らかにした。今後、木構造の防耐火性能の合理的開発・評価の確立に寄与すると考える。