Journal of Wood Science

, Volume 63, Issue 6, pp 625–634 | Cite as

Relationship between clamp force and pull-out strength in lag screw timber joints

  • Doppo Matsubara
  • Yoshiaki Wakashima
  • Yasushi Fujisawa
  • Hidemaru Shimizu
  • Akihisa Kitamori
  • Koichiro Ishikawa
Original article


This study empirically examines the relationship between clamp force and pull-out strength in lag screw joints of timber members, using data obtained in tightening tests and pull-out tests. Maximum clamp force per unit screw length as determined from the tightening tests was lower than the lower bound for the 95% tolerance range for pull-out strength per unit screw length as determined from the pull-out tests. Moreover, X-ray CT (computed tomography) observations of anchor members from both tests revealed that failure behavior clearly differed between the tightening test and the pull-out test: tightening caused damage to the wooden, female thread in addition to major splitting damage in the wood perpendicular to the grain near the tip of the lag screw.


Lag screw joints Clamp force Pull-out strength Tightening test 



This work was supported in part by the Science and Technology Research Promotion Program for Agriculture, Forestry, Fisheries and Food Industry.


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Copyright information

© The Japan Wood Research Society 2017

Authors and Affiliations

  • Doppo Matsubara
    • 1
  • Yoshiaki Wakashima
    • 2
  • Yasushi Fujisawa
    • 2
  • Hidemaru Shimizu
    • 3
  • Akihisa Kitamori
    • 4
  • Koichiro Ishikawa
    • 5
  1. 1.Tokyo Metropolitan Industrial Technology Research InstituteTokyoJapan
  2. 2.Toyama Prefectural Agricultural, Forestry and Fisheries Research CenterImizuJapan
  3. 3.Sugiyama Jogakuen UniversityNagoyaJapan
  4. 4.Research Institute for Sustainable HumanosphereKyoto UniversityUjiJapan
  5. 5.University of FukuiFukuiJapan

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