再び注目を集める「超薄型ジャッキ（フラットジャッキ）工法」

摘要

The super thin-type Flat Jack was invented in 1938 by Dr. Eugene Freyssinet, who is the ancestor of the pre-stressed concrete (PC) technology, and it has been still now world-widely used since 70 years ago. Its structure is a deformable steel vessel made out of two thin steel plates, both of which are troughed at their peripheries and which edges are joined together by welding. At the external edge, two holes for hydraulic injection and air outlet are arranged. The principle is as follows; when a hydraulic pressure is applied from an injection whole, both faces of the jack are deformed separately to yield lifting power. Its special features and advantages are applicable at narrow spaces because of the thin jack, no breakdown due to a simple structure, light-weight and low cost. This is applied as a support and for movement of heavy structures, and also adjustment of structures deformed by concrete creep. And recently, the cases of applying for replacement of bridge shoes and for installation of the seismic control devices to the buildings are increasing. From now on, it is expected that any practical usages in the fields of designing and construction planning of structures are developed based on any novel ideas to utilize unique feature of the Flat Jack.%超薄型のフラットジャッキは，1938年にプレストレストコンクリート（PC）の視であるEugene Fressynet博士（フランス〉により発明され，70年を過ぎた現在も世界中で使用されている。構造は，周囲に半円形の凹みを有する2枚の薄い軟鋼板を溶接により接合したもので，外周部に注入口と排出口を有している。その原理は，注入口より液庄をかけて，ジャッキの両面は互いに引き離されるように変形し，大きな揚力が発生する。決あいな場所で使用可能であり，構造が単純で故障がなく，軽量で低価格という特長がある。重患物の支持．移級クリけプ変形の穆正等の俄に，僑梁支承の交換工事や建築物の免震化工事に使用されている。今後,　フラットジャッキの独特の特徴を生かし，構造物の設計や施工計画において,新しい発想に基づく，時代のニーズにあった合理的な使用方法が創造きれることが期待される。