Method for constructing cylindrical tank
A method for constructing a cylindrical tank which has a metallic inner tank and a concrete outer tank includes a step of building up a PC wall in an outer circumferential edge portion of a base plate, a step of assembling an outer tank roof on the base plate other than the outer circumferential edge portion of the base plate, a step of lifting the outer tank roof which is on the base plate using a jack-up unit while the PC wall is being built up and then holding the outer tank roof on the PC wall, and a step of assembling the inner tank independently of the outer tank roof in a space under the outer tank roof which is created due to the lifting.
1. A method for constructing a cylindrical tank which has a metallic inner tank and a concrete outer tank, comprising:
a step of building up a sidewall of the concrete outer tank in an outer circumferential edge portion of a base portion of the concrete outer tank;
a step of assembling a roof portion of the concrete outer tank on the base portion of the concrete outer tank other than the outer circumferential edge portion;
a step of lifting the roof portion of the concrete outer tank which is on the base portion of the concrete outer tank using a jack-up unit while the sidewall of the concrete outer tank is being built up and then holding the roof portion on the sidewall of the concrete outer tank; and
a step of assembling the metallic inner tank independently of the roof portion of the concrete outer tank in a space under the roof portion of the concrete outer tank which is created due to the lifting by alternately repeating lifting of an inner tank lateral plate using the jack-up unit and attachment of a next inner tank lateral plate to a lower side of the lifted inner tank lateral plate,
wherein the method further includes installing a hanging-side jack stand in the sidewall of the concrete outer tank above the roof portion of the concrete outer tank, installing a hanged-side jack stand in the roof portion of the concrete outer tank, and installing the jack-up unit across the hanging-side jack stand and the hanged-side jack stand, and the step of lifting the roof portion of the concrete outer tank includes hoisting the roof portion of the concrete outer tank using the jack-up unit,
wherein positions of the hanging-side jack stand and the jack-up unit in a vertical direction can be changed during the step of lifting the roof portion of the concrete outer tank, and
wherein the lifting of the roof portion of the concrete outer tank using the jack-up unit and the lifting of the inner tank lateral plate using the jack-up unit are performed independently and in parallel with each other.
2. The method for constructing a cylindrical tank according to claim 1 , comprising:
a step of assembling the roof portion of the concrete outer tank in a state in which the roof portion is held on the sidewall of the concrete outer tank.
3. The method for constructing a cylindrical tank according to claim 2 , wherein during the step of assembling the roof portion of the concrete outer tank in the state in which the roof portion is held on the sidewall of the concrete outer tank, building up of the sidewall of the concrete outer tank continues.
4. The method for constructing a cylindrical tank according to claim 3 , wherein during the step of assembling the roof portion of the concrete outer tank in the state in which the roof portion is held on the sidewall of the concrete outer tank, assembling of the metallic inner tank continues.
5. The method for constructing a cylindrical tank according to claim 1 ,
wherein the sidewall of the concrete outer tank is built up by placing concrete using an outer tank lateral plate as an inner side mold, the method comprising:
a step of forming an opening portion in the outer tank lateral plate in advance;
a step of fitting an anchor portion which is connected to an anchor that is embedded in concrete in the opening portion of the outer tank lateral plate; and
a step of supporting the jack-up unit via the anchor portion that is fitted in the opening portion of the outer tank lateral plate.
6. The method for constructing a cylindrical tank according to claim 5 , wherein the anchor portion comprises an anchor plate secured to both the anchor and to the outer tank lateral plate.
7. The method for constructing a cylindrical tank according to claim 1 , comprising:
a step of providing the jack-up unit at a top portion of the sidewall of the concrete outer tank after the sidewall of the concrete outer tank is built up to lift the roof portion of the concrete outer tank;
a step of providing a protruding portion on an inner circumferential face of the sidewall of the concrete outer tank to regulate a height at which the roof portion of the concrete outer tank is lifted; and
a step of attaching the roof portion of the concrete outer tank whose height is regulated by the protruding portion to the inner circumferential face of the sidewall of the concrete outer tank via a coupler.
8. The method for constructing a cylindrical tank according to claim 1 , comprising:
a step of assembling the roof portion of the concrete outer tank on a plurality of trestles located on the base portion.