Original Paper(Vol.62 No.4 pp.274-279)

Estimation of Joint Strength of Large-Finger-Jointed Glued Laminated Timber

Yasunobu NODA, Takuro MORI and Kohei KOMATSU

Abstract:In this research, joint strength of glued laminated timber (glulam) of karamatsuiLarix kaempferijconnected by large finger joint (LFJ) whose finger length was 52 mm was estimated using results of tensile and bending strength of LF-jointed laminae. Adequate end-pressure of the LFJ with resorcinol resin adhesive was obtained to be 2-5 MPa by the linear portion of relation between load and displacement observed in the inserting compressing test. Using an equation for predicting the modulus of rupture (MOR) for glulam derived by Komatsu, 5th percentile lower limit value of bending strength of glulam connected by LFJ of 120 mm width were estimated by observed tensile and bending strength of LF-jointed laminae of 30 mm thick and 120 mm width. And joint strength of several cross section size glulam connected by LFJ, 120~120, 120~180 and 120~300 mm, were obtained by bending test. As a result, observed minimum joint strength on each section size were higher than the estimated MORs. Moreover, good agreement was obtained between estimated MOR curve and estimating strength by size factor for larger cross section size.

Key Words:Heavy timber construction, Finger joint, Glued joint, Tensile strength, Bending strength, Joint efficiency, Scale factor