Inpost - Inpost

…If the friction between the voussoirs is large enough, or the voussoirs are bonded together with mortar, or the left and right sides of the arch are sufficiently solidified by walls so that the voussoirs do not move, the load on the arch is transferred to the lower voussoirs one after another, reaching both ends of the arch, forming a very strong opening (doorway, window). The members that support both ends of the arch are called imposts, and they also serve as decoration for the upper ends of the columns and walls that support the arch, and as supports for both ends of the formwork. Arches have the advantage that the members that form the arch have almost no bending force, but in return they generate lateral pressure (thrust, also called arch thrust) diagonally downward toward the outside at both ends of the arch. …

*Some of the terminology that mentions "impost" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…迫石と迫石のあいだの摩擦力が十分大きいか，迫石が相互にモルタルで接着されているか，アーチの左右が壁で十分固められていて，迫石が移動することがなければ，アーチの上にかかる荷重は次々に下位の迫石に伝達されて，アーチの両端に達し，ひじょうに堅固な開口部(戸口，窓)を形づくる。アーチの両端を支える部材を迫元(インポスト)といい，アーチを支える柱や壁の上端の装飾ともなり，また型枠の両端を支持する支承物の役割を果たす。アーチは，アーチを形づくる部材にほとんど曲げの力が生じないという長所がある代りに，アーチの両端部に，外方へ向かって斜め下方への横圧力(スラスト，アーチ推力ともいう)を生ずる。…

※「インポスト」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報