Method for fabricating a gravity-based structure (GBS) at a specialized fabrication site
A gravity-based structure (GBS) includes central and protruding parts having a common base slab. For the central part, outer and inner walls and a top slab are cast in concrete so that the GBS forms a rectangular prism. As casting of individual outer wall sections is completed, a reinforcement cage is assembled, formwork is installed, and protruding part outer and inner walls are cast, the outer walls being formed along the base slab perimeter with a height lower than the central part outer wall height. As separate protruding part wall sections are cast, a reinforcing cage is assembled, formwork is installed for a protruding part top slab, and then cast. Post-tensioning of central part base and top slabs and central and protruding part outer and inner walls is done as central and protruding part top slab casting is completed and the concrete is cured, increasing buoyancy and reducing submersion.
1 . A method for fabricating a gravity-based structure (GBS), comprising:
assembling a first reinforcement cage for a rectangular base slab,
installing a first formwork and then concreting the base slab,
assembling, as separate sections of the base slab are concreted, second reinforcement cages for inner walls and outer walls and concreting the inner walls and the outer walls by slipforming,
assembling, as separate wall sections are concreted, a third reinforcement cage for a main top slab,
installing a second formwork and then concreting the main top slab, and
post-tensioning with reinforcement strands the main top slab and the base slab, as well as the inner walls and the outer walls,
wherein the GBS is fabricated including a central part and protruding part that have the common base slab, besides the inner walls and the outer walls as well as the main top slab are concreted for the central part of GBS, that takes form of a rectangular prism, as separate sections of the outer walls of the central part are concreted,
a fourth reinforcement cage is assembled, a third formwork is installed and concreting is performed for the inner walls and the outer walls of the GBS protruding part,
the outer walls of the GBS protruding part are made along a perimeter of the base slab, and at the same time a height of the outer walls of the protruding part is lower than a height of the outer walls of the central part, as separate wall sections of the protruding part are concreted,
a fifth reinforcement cage is assembled and a fourth formwork is installed for an additional top slab of the protruding part and then concreted, and the base slab and the main top slab, as well as the inner walls and the outer walls of the central part and protruding part are post-tensioned as the main top slab and the additional top slab are concreted and the concrete of the post-tensioned structures is cured.
2 . The method according to claim 1 , wherein the main top slab is concreted with upward bending of a central part of the main top slab so that the central part of the main top slab lowers on its own weight to a design position.
3 . The method according to claim 1 , wherein, as soon as separate sections of the main top slab are concreted, a sixth reinforcement cage is assembled, a fifth formwork is installed, embedments are set and supports for equipment are concreted on the main top slab.
4 . The method according to claim 1 , wherein, in the course of the inner walls and the outer walls of the central part being concreted, openings are left for formwork removal and further installation of equipment inside GBS compartments shaped by the inner walls and the outer walls of the central part and the main top slab and the base slab.
5 . The method according to claim 3 , wherein, simultaneously with concreting of the inner walls and the outer walls of the central part, a seventh reinforcement cage is assembled, a sixth formwork is installed and an intermediate slab is concreted, post-tensioned, and inside at least one compartment shaped by the inner walls and the outer walls of the central part, the intermediate slab and the main top slab, a tank for storage of liquids is arranged with panels, delivered through temporary wall openings.