Effect of Changes in the Moisture Content due to Surrounding Relative Humidity on the Contact Stress in Traditional Mortise and Tenon Joints III.

Abstract

This research is focused on evaluating the effi ciency and failure mechanism of joints using a komisen Japanese traditional square key of compressed sugi Japanese ceder ; Cryptomeria japonica D. Don , and to evaluate to what extend hozo-komisen Japanese traditional mortise and tenon joint strength is being infl uenced by the recovery of compressed sugi komisen when exposed to long term humidity cycling.Compressed sugi komisen showed a change of yield and rupture mode compared to shirakashi Quercus myrsinaefolia Blume komisen, as did the komisen inserting direction into the joint because it has characteristic and anisotropic properties. The compressed sugi komisen joint C1R , when inserted according to the R type, yielded by shear of the komisen and reached its maximum strength P max : 12.5 kN just before rupture at 10 mm displacement at the tenon. The failure mode showed a different pattern, compared to the shirakashi komisen joint S1R where the central komisen yielded in bending. The strength of the compressed sugi komisen joint C1RH exposed to cyclic changes of humidity 40 80%RH during two years increased in maximum strength, yield strength, and energy absorption. This is in contrast to the shirakashi komisen joint C1RH that showed a dramatic and remarkable strength decrease when exposed to the climatic environment.

Evaluation on structural performance of compressed wood as shear dowel

“…As reported by Jung et al (2006), a CW peg with its annual ring radial to loading direction (08, flat-wise) in a mortise and tenon joint failed not by bending in the center but by shearing at two interface lines. The joint was more ductile and more reliable than those made of maple or oak.…”

“…wooden construction (Ohtani et al 2005;Jung et al 2006). The CW discussed in these quoted reports was not treated by heat, steam, or chemicals to permanently fix its dimensions, and therefore would spring back under cyclic humidity changes, and thus is expected to provide a huge benefit in maintaining tightness of the joint in service.…”

Development of a Hybrid Pin Joint with a Compressed Wooden Dowel and Metal Pipe

“…Aiming to improve the key-joint's performance, a hybrid pin (HP), composed of a compressed wooden dowel [3] [4] inserted in a stainless steel pipe is suggested in this research.…”