A STUDY ON THE HISTORICAL TRANSITION OF A VARIETY OF RYAKUKAMA (SCARF JOINTS) IN JAPANESE WOODEN STRUCTURES

要旨

After an introduction explaining the methodology applied in my general study on the development of Japanese traditional joints, this paper is divided into the following sections ; 1) an investigation into the first examples of Ryakukama in the histoty of Japanese wooden structures, 2) an atempt to trace the development of Ryakukama from various viewpoints. These include their forms, members to which they were applied, their positions in use (Fig-10) and compound joints created by combining Ryakukama with other basic joint types (Fig-3), 3) a discussion of the changing functions of Ryakukama, 4) an inquiry into the developing concept of Ryakukama in the minds of capenters. Conclusions are ; 1) that Ryakukama were brought to Japan from China with the idea of using Nuki (continuous horizontal bracing members) at the beginning of the Middle Ages, around 1200 A. D., 2) that the concept of Ryakukama changed twice during the Middle Ages. Ryakukama first appeared as one of various joints by which the connection of members (especially a pair of Nuki intersecting at a pillar) could be assured (Fig-6, 20, 21). In the second phase Ryakukama were regarded as joints to be used exclusively for Nuki and Kashira-Nuki. The third phase was marked by the use of Ryakukama to join concealed structural members, while it, was noted that Ryakukama and Kama were closely related both in terms of distinctive feature relative to function (Kama were used in revealed structural members) and in terms of common features relative to form and their compounds with Mechigai (another basic type of joint, fig-24).

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