抄録
The moment carrying capacity of beam-to-column joint (Sashigamoi) on a large size column has sufficient strength property in structural designing the traditional timber buildings. The load carrying capacity of traditional timber joints such as Sashigamoi joint is based on timber-to-timber interlocking resistance. In general their complicated composition of members makes it difficult to estimate the structural performance. This paper reports the evaluation of rotational performance of one of the traditional timber joint with spline member connected by inclined shear-key (Shachi-sen).
At first we conducted a strength test of the joint with varying dimensional and loading conditions. From the moment-angle relationship of the test result and observation of failure mode, a different resistance mechanisms of symmetric and asymmetric bending situation was suggested. The one mechanism is horizontal resistance depending on tensile force of shear-key joint and bearing force on beam against column which is so called tensile bolt effect. The other working mechanism is bracket effect induced by vertical couple of force resistance applied at the tip of the spline and the tenon.
Then formulas based on mechanical models which are able to estimate not only stiffness and yield strength but also a large deformation behavior until final failure were proposed based on the above mentioned mechanism and experimental phenomena by considering the equilibrium of force and compatibility condition of the displacement. The working mechanism of tensile bolt effect was modeled in the tri-linear curve on which first yield is decided by compression yield and then followed by ultimate state caused by tensile strength of spline key joint, while the mechanism of bracket effect was modeled in bi-linear relationship.
Finally an additional series of experiment was carried out to verify the formula. The moment-rotation angle relationship of joints estimated by the proposed formula with inputting size parameter, material constant and tensile strength parameter of unit Shachi-sen joint which was obtained by the mechanical model proposed in the pre-reported paper. The results were in good agreement with the test results, which confirmed the certainty of the model.
