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Official Journal of the Japan Wood Research Society

Bending creep of glued laminated timber (glulam) using sugi (Cryptomeria japonica) laminae with extremely low Young’s modulus for the inner layers


The main purpose of this study was to establish whether sugi lumber with an extremely low Young’s modulus, which is plentifully produced in southern Japan, can be practically used as laminae for glued laminated timber (glulam) from the viewpoint of long-term performance under loading. Bending creep tests were carried out on sugi (Cryptomeria japonica D. Don) glulam with extremely low Young’s modulus laminae (3–4 kN/mm2) for the inner layers, as were tests on hybrid glulam with Douglas-fir (Pseudotsuga menziesii Franco) laminae (14–15 kN/mm2) for the outermost layer and sugi laminae (including those with a Young’s modulus of 3–4 kN/mm2) for the inner layers. The specimens were eight glulam beams with different compositions that were 105 mm wide, 210 mm deep, and 3980 mm long. The term of the creep test was 4 years. The results are summarized as follows. First, there were no significant differences between the Young’s modulus or bending creep of glulam L30 (laminae with Young’s modulus of 3–4 kN/mm2) and that of glulam L50 (laminae with Young’s modulus of 5–6 kN/mm2) for the inner layers. Second, for asymmetric compositions, the behavior of increases and decreases of relative creep due to atmospheric changes showed opposite behavior for glulam loaded from the side of lower Young’s modulus and from the side of higher Young’s modulus. Third, the required experimental term for the creep test to estimate an accurate long-term curve is 1 or 2 years (with data for the first 6 months excluded) when the power law is used for the estimation. Fourth, the values of relative creep in 50 years obtained from the experimental term were much lower than 2, which is the standard value set by Notification No. 1459 of the Ministry of Construction in Japan, and these values were not affected by the composition of the laminae.


  1. Kamiya F (2004) Introduction to the research project “Development and evaluation of new structural material using local sugi lumber, among others” (in Japanese). Rep Forest Forest Prod Res Inst 508:2

    Google Scholar 

  2. Kamiya F (2005) Changes in wood-based materials and issues for the future (in Japanese). J Timber Eng 63:17–20

    Google Scholar 

  3. Kamiya F (2005) Development and evaluation for new structural materials using sugi and other regionally produced timbers (in Japanese). Jyutaku to Mokuzai 8:14–17

    Google Scholar 

  4. Tanaka H, Morita H, Murase Y (2008) Strength properties of nonstandard glulam using low-grade sugi laminae. In: Proceedings of the 10th World Conference on Timber Engineering, Miyazaki Japan, June 2–5, p 402

  5. Matsumoto A, Morita H, Fujimoto Y, Shiiba A, Iimura Y (2008) Strength performance of obi-sugi laminae with low modulus of elasticity. In: Proceedings of the 10th World Conference on Timber Engineering, Miyazaki, Japan, June 2–5, p 363

  6. Lu W, Erickson RW (1994) The effects of directed diffusion on the mechano-sorptive behavior of small redwood beams. Forest Prod J 44(1):8–14

    Google Scholar 

  7. Grossman PUA (1976) Requirements for a model that exhibits mechano-sorptive behaviour. Wood Sci Technol 10:163–168

    Article  Google Scholar 

  8. Arima T, Maruyama N (1988) Creep deflection of wood with knots and wood-based materials during changes of humidity (in Japanese). In: Summaries of Technical Papers of Annual Meeting of the Architectural Institute of Japan. Chiba, Japan, pp 123–124

  9. Arima T, Sato M, Mashita K (1981) Studies on evaluation method for long-term performance of wood-based materials and elements (in Japanese). Rep Build Res Inst 95:25–42

    Google Scholar 

  10. Aratake S, Arima T (1995) Creep of sugi sawn lumber in process of humidity changes (in Japanese). Mokuzai Gakkaishi 41: 359–366

    Google Scholar 

  11. Aratake S, Morita H, Arima T (2002) Creep of various structural members in ambient conditions — estimation of future deflections considering the longevity of wooden structures (in Japanese). Mokuzai Gakkaishi 48:233–240

    Google Scholar 

  12. Architectural Institute of Japan (2006) Creep deflection coefficient (in Japanese). In: Standard for Structural Design of Timber Structures. Maruzen, Tokyo, pp 165–168

  13. Ohashi Y, Matsumoto K, Sato T, Hirai T (2008) Long-term bending creep of wooden I-joists with Japanese softwood materials. In: Proceedings of the 10th World Conference on Timber Engineering, Miyazaki Japan, June 2–5, p 398

  14. Arima T (1967) The influence of high temperature on compressive creep of wood (in Japanese). Mokuzai Gakkaishi 13:36–40

    Google Scholar 

  15. Kawazoe M, Sobue N (2001) Effects of moisture cycling period and cross-sectional size of specimens on bending creep of wood under humidity cycling (in Japanese). Mokuzai Gakkaishi 47:81–91

    CAS  Google Scholar 

  16. Kimura M, Kusunoki T, Oshiumi S (2002) Bending creep behavior of full size Douglas fir glulam beams (in Japanese). J Struct Constr Eng 561:169–176

    Article  Google Scholar 

  17. Architectural Institute of Japan (1996) Duration of load and creep (in Japanese). In: Structural Design Notes for Timber Structures. Maruzen, Tokyo, pp 31–43

  18. Mori T, Kitamura T, Isoda H, Takahashi S, Sasagawa A (2003) The bending creep behavior of glulam beam under different temperature and humidity conditions (in Japanese). J Struct Eng 49B, 593–598

    Google Scholar 

  19. Aratake S, Arima T, Tanaka H (2006) Creep of sugi (Cryptomeria japonica D. Don) structural members processed by various drying methods. Trans Mater Res Soc Jpn 31:985–988

    Google Scholar 

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Correspondence to Shiro Aratake.

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Aratake, S., Morita, H. & Arima, T. Bending creep of glued laminated timber (glulam) using sugi (Cryptomeria japonica) laminae with extremely low Young’s modulus for the inner layers. J Wood Sci 57, 267–275 (2011).

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Key words

  • Creep
  • Mechanosorptive deflection
  • Power law
  • Sugi
  • Glulam