| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the quality and simplify the manufacturing process by providing a FRP layer on the inner face of an outer surface protection layer, providing a mortar layer on the inner face of the FRP layer, and providing an inner surface protection layer on the inner face of the mortar layer. SOLUTION: By the use of a filament winding machine, required thickness against inner pressure is made minimum, and a pipe-like FRP layer 3 is manufactured by helical winding of 55 deg.. The FRP layer 3 is loaded on a centrifugal machine, and while rotating it centering around the axis, unhardend mortar is poured therein, so as to form a pipe like mortar layer 2. By centrifugal force accompanying rotation, the unhardened mortar is pushed against the inner face of FRP layer 3 on the outside, and the FRP layer is pushed and spread. By stopping the rotation and releasing the centrifugal force after hardening the mortar, compression force in the circumferential direction is given to the hardened mortar layer 2, utilizing returning force to the initial form of the FRP layer 3, and hence fixed prestress is introduced to the mortar layer 2. |
