Super thin-type Flat Jack
By J. Akama, T. Kato and M. Nakamura
Concrete Journal, Vol.49, No.2, Feb. 2011
- Synopsis
- 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 adventages 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.
- Keywords:
- freyssinet, flat jack, narrow spaces, replacement works of bridge shoes, seismic control works for building
