Shinbashira

The shinbashira (心柱, also 真柱 or 刹/擦 satsu) refers to a central pillar at the core of a pagoda or similar structure.

The shinbashira has long been thought to be the key to the Japanese pagoda's exceptional earthquake resistance, when newer concrete buildings may collapse.

Hōryū-ji, the world's oldest wooden structure, was found to have in 2001 a shinbashira from a tree felled in 594 AD. Their examples continue in impending centuries in other tō (塔, pagoda) like the Hokkiji in Nara in 8th century, and Kaijūsenji of Kyoto.

The pillar structure is made out of straight trunks of Japanese Cypress (hinoki). The pillar runs the entire (but see below) length of the pagoda, and juts out of the top 'layer' of the pagoda, where it supports the finial of the pagoda.

The initial architectural forms included the pillar ingrained deep within the foundation(shinso 心礎)Hōryūji Gojū-no-tou 法隆寺五重塔,(Gojū-no-tō: 5-layered-pagoda) was found to be 3m below ground level.

At this time, pillars were tapered and became roughly circular from the point where they rose beyond the roof, starting as hexagonal from the base. This shaping was necessary as metal pieces were fit to the central pillar to support the spire. Later uses starting 12c involve them suspended just above the ground, thus making them suspensions like the Nikkō Tōshōgū Gojū-no-tū 日光東照宮五重塔 (1818) in Tochigi prefecture.

Size had a bearing on the fragmentation of the pillars found in the 8th century. The central pillar of Gojuu-no-tou at Hōryūji has a height of 31.5 m with a diameter of 77.8 cm at base, 65.1 cm in the middle and approximately 24.1 cm at the midpoint on the spire. Such huge pillars had to be divided into three sections: from the base stone to the third floor; from the fourth story to the point where the spire begins, and the spire section. The shaft of a three-storied pagoda (sanjuu-no-tou 三重塔), is divided between the second and third stories and again where the spire begins. During the 8c, shinbashira were erected on a base stone set at ground level. Example: Hokkiji Sanjuuu-no-tou 法起寺三重塔 (742) in Nara. (see Earthquake Resistance below)

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