JPH0826550B2 - Sliding base-isolated offshore structure with contact pressure adjustment function - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an offshore structure constructed by a dry dock, towed, sunk, and then installed. Examples of concrete structures include offshore oil development platforms, marine leisure facilities, power generation and
Examples include industrial plant barges such as methanol and pulp.

[0002]

[Prior Art] Offshore oil development platform,
The general procedure for constructing an offshore structure consists of the following steps.

A structure body is built in a dry dock.

Water is poured into the dry dock so that the structure body is in a floating state, and the equipment is equipped.

A floating structure is towed to the site.

The structure is sunk and installed.

After the horizontal external force such as waves, tidal current, wind, earthquake, ice pressure, etc. is poured so as not to slide, sand ballast is added, concrete ballast is placed, etc. to add weight to increase sliding resistance.

The procedure may be performed in a dry dock.

[0009]

When the gravity type offshore structure as described above is to be constructed on a coastal or offshore sea in an earthquake area such as Japan, there are the following problems.

(A) In the conventional method, since weight is added so as not to slip with respect to an earthquake, the seismic inertial force increases, and it is difficult to secure a sufficient sliding safety factor.

(B) Offshore structures are more buoyant than land structures, and in the event of an earthquake, they are also subject to hydrodynamic pressure due to the surrounding seawater, making it difficult to ensure a safety factor for sliding.

(C) When the seabed is soft, not only the construction cost for ground improvement but also the construction of a gravity type offshore structure may be impossible.

As means for solving the above problems,
It is conceivable that the slab portion of the offshore structure is separated into a foundation side slab and a body side slab to allow sliding on the contact surface between the foundation side slab and the body side slab against a predetermined horizontal external force.
However, even in that case, there are the following problems.

(1) In soft ground, there is a risk of slipping between the foundation side slab and the ground, or the ground breaking.

(2) When relocated to a location where the environmental load such as water depth, earthquake, or wave is different, there is a possibility that appropriate sliding resistance may not be obtained.

(3) At the time of installation, it is necessary to have a device that is tightly connected to the base side slab when it is towed integrally with the main body.

(4) At the time of relocation, the foundation side slab is left behind on the seabed and is difficult to recover.

(5) When relocating to a location where the water depth is deep, a function of adjusting is required.

The present invention is intended to solve the above-mentioned problems when the bottom plate of an offshore structure has a double bottom plate structure.

[0020]

The sliding seismic isolation type offshore structure of the present invention is designed in the gravity type offshore structure according to the following criteria, for example.

(1) The weight of the structure including the ballast is reduced. However, with respect to waves, tidal currents, and winds that occur frequently, the sliding resistance due to gravity does not cause slippage.

(2) Sliding is allowed for a design earthquake (a target earthquake designed so that the stress of the structure is lower than the yield point or lower than the short-term allowable stress).

(3) In the case of accident load (the maximum load that can be considered historically and geologically such as earthquake or ship collision), sliding is allowed and the structure is fatally destroyed. Design not to.

In order to make the above possible, in the present invention, the base slab portion of the structure has a double bottom slab structure so that the bottom slab is slid between the two slabs to control the sliding resistance.

That is, the slab portion of the gravity type offshore structure is separated into a main body side slab and a foundation side slab supporting the gravitational offshore structure. It is configured to allow sliding on the contact surface with the side slab.

The contact surface between the foundation-side bottom slab and the main-body-side bottom slab is a smooth finished surface of metal, plastic, tile, stone, cement mortar, concrete or the like, so that the sliding resistance coefficient can be grasped and the sliding Predictive analysis of behavior can be facilitated.

Further, for example, with respect to the above-mentioned accident load, a rising wall is provided in the peripheral portion of the foundation-side bottom slab to form a predetermined gap with the main body of the structure, and is made of rubber or wood as required. By providing means such as providing an anti-corrosion device and designing the structural strength of the rising wall to be weaker than the main body side,
Even if there is a local damage, a structure that prevents the fatal damage on the main body side is considered by restraining the displacement of the sliding structure main body to some extent and absorbing seismic energy.

In the present invention, in the seismic isolation type offshore structure having such a double bottom slab structure, in order to solve the problems described in the preceding paragraph, the outer circumference between the foundation side slab and the main body side slab is sealed by an O ring or the like. Then, the contact pressure is arbitrarily adjusted by applying water pressure to the gap of the contact surface via a pipe.

The water pressure between the contact surfaces can be adjusted by a contact pressure adjusting device which is constructed by connecting piping to a constant water level box which keeps the water pressure in the gap constant.

By making the constant water level basin movable up and down, the water pressure between the contact surfaces can be arbitrarily adjusted from 0 to more than the water pressure due to the outer water level, and the sliding resistance can be adjusted by changing the contact pressure. The double bottom slab can be integrated in the case of towing.

[0031]

EXAMPLES Next, the illustrated examples will be described.

FIGS. 2 and 3 show, as an example, a case where the double bottom plate structure of the present invention is applied to an offshore oil development platform.

As shown in the figure, the lower bottom slab of the hollow structure main body 1 is separated into a main body side slab 3 and a base side slab 2 which supports it.

The structure body 1 has a dry section 4 in the center, and water ballast 5 and sand ballast 6 are injected or put into the outer side of the dry section 4 to create a gravity type structure such as waves, tidal currents, winds and small and medium-sized earthquakes. On the other hand, it does not slide. In addition, on-structure equipment 1 has built-in equipment 7 such as living facilities and work equipment.

FIG. 3 shows the details of the bottom slab. The base side base plate 2a and the main body side slide, which are made of stainless steel plate or Teflon processed steel plate, are provided on the contact surfaces of the base side bottom plate 2 and the main body side bottom plate 3, respectively. The plate 3a is integrated with the concrete surface, and the structure main body 1 slides with respect to the foundation bottom slab 2 when a horizontal external force of a predetermined amount or more, for example, the above-described design earthquake is applied to the platform.

Further, in the present embodiment, a downward base skirt portion 8 and an upward rising wall 9 are formed in the peripheral portion of the base side slab 2. The base skirt portion 8 penetrates into the sea bottom surface 10 to fix the base side bottom plate 2 to the sea bottom surface 10.

The rising wall 9 limits the sliding of the structure body 1 when the structure body 1 slides due to a design earthquake or accident load. 11 is provided. The impact protection device 11 in the present embodiment uses a cylindrical rubber fender made of synthetic rubber or the like.

With respect to the design earthquake, it slides in the range of play δ, and the defense device 11 does not work. That is, the defense device 11
Works effectively only under accident loads or destructive earthquakes and absorbs some of the kinetic energy.

To protect the anti-defense device 11, the structure body 1
The gap between the rising wall 9 and the rising wall 9 is filled with a filling material 12 such as Styrofoam that does not restrain the sliding, and a sealing material 13 is attached to the upper surface thereof to prevent foreign matter from entering.

Further, in the figure, reference numeral 14 is a tension bolt for tightly connecting the foundation bottom slab 2 to the structure body 1 at the time of towing, and reference numerals 15 and 15a denote the tension bolts 1 later.
This is the audit corridor used when 4 is to be removed. In the present invention, since the base side bottom plate 2 and the main body side bottom plate 3 can be integrated by adjusting the water pressure in the gap portion of the contact surface, these are not necessarily required, but they can be used together.

FIG. 1 shows an embodiment of a contact pressure adjusting mechanism by water pressure according to the present invention.
A constant water level basin 51 is installed, a header pipe 52 is passed through, and the water pressure acting on the contact portion between the foundation side bottom plate 2 and the main body side bottom plate 3 is controlled. As a result, the sliding resistance acting on the contact portion can be controlled so that the structure body 1 slides in a predetermined design earthquake.

The constant water level basin 51 is installed in the dry section 4 of the shaft portion of the structure body 1 to supply the leaked water to the water supply pump 5.
3 intermittently replenishes the constant water level measure 51 through the water supply pipe 54 to maintain the water level of the constant level measure 51, and the weir 55.
The structure is such that the water that has passed over is sent to the drainage pit 56 and returned to the sea by the drainage pump 57 through the drainage pipe 58.

Further, by using flexible or expandable pipes for the water supply riser pipe 54a, the constant water pressure riser pipe 52b, and the drainage riser pipe 58a, the constant water level basin 51 can be moved up and down to set an arbitrary constant water level. It has a structure that can be secured. Further, an O-ring 59 is mounted as a sealing material around the contact portion between the base side bottom plate 2 and the main body side bottom plate 3.

The contact pressure adjusting function will be described below.

When the water level of the constant water level basin 51 is made lower than the external water level, the water between the contact surfaces is squeezed to the constant water level basin 51 through the constant water pressure pipe 52a, the header pipe 52 and the constant water pressure riser pipe 52b. Even if water leaks from the O-ring 59, the water pressure between the contact surfaces is kept constant by spontaneously flowing out from the constant water level grid 51.

When the water level of the constant water level grid 51 is made higher than the external water level, the constant water pressure riser pipe 52 b and the header pipe 52
Water pressure is applied between the contact surfaces through the constant pressure pipe 52a. If water leaks from the O-ring 59, the water level meter 5
In order to keep the water level of 1 constant, water is replenished by the pump 53.

At the time of installation and relocation, by reducing the water pressure between the contact surfaces, the base side bottom plate 2 is brought into close contact with the main body side bottom plate 3 by the external water pressure. Usually, this pressure is sufficient to support the weight of the base side slab 2 and to be integrated with the main body side slab 3.

By keeping the constant water level basin 51 at an appropriate height, an arbitrary pressure can be exerted between the bottom plate contact surfaces, and as a result, the sliding resistance can be adjusted arbitrarily.

[0049]

【The invention's effect】

(1) The stability of the structure can be maintained due to the sliding resistance of the gravity type structure against waves, tidal currents, and winds that frequently occur.

(2) For horizontal external force beyond the design earthquake,
By sliding the main body of the offshore structure on the foundation side slab,
Absorb seismic energy and exert seismic isolation effect. Also,
Even in that case, the stability in the vertical direction as a gravity structure is maintained.

(3) For accident load, the kinetic energy is absorbed by sliding, and at the same time, a rising wall is provided in the peripheral portion of the foundation side slab, and the shape of the strain energy due to the deformation of the protection device or the rising wall is formed. Thus, it is possible to absorb kinetic energy and prevent harmful displacement to the main body of the marine structure, and at the same time prevent fatal damage to the main body.

(4) By adjusting the water pressure in the gap between the contact surfaces, it is possible to obtain an arbitrary sliding resistance, and to relocate to a location with different environmental loads such as water depth, earthquake, or wave, or with different ground conditions. Also, proper sliding resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a structure of a main part in an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing an example in which a sliding seismic isolation type offshore structure is applied to a platform.

FIG. 3 is an enlarged view of a main part corresponding to FIG.

[Explanation of Codes] 1 ... Structure body, 2 ... Foundation side bottom plate, 2a ... Foundation side base plate, 3 ... Body side bottom plate, 3a ... Body side sliding plate, 4 ... Dry section, 5 ... Water ballast, 6 ... Sand ballast , 7 ... Overlaid equipment, 8 ... Foundation skirt part, 9 ... Standing wall, 10 ... Sea bottom, 11 ... Impact protection device, 12 ... Filling material, 1
3 ... Sealing material, 14 ... Tension bolt, 15, 15a
… Auditorium, 51… Water level measure, 52… Header pipe, 5
2a ... Constant water pressure pipe, 52b ... Constant water pressure riser pipe, 53 ... Water supply pump, 54 ... Water supply pipe, 54a ... Water supply riser pipe, 5
5 ... weir, 56 ... drainage pit, 57 ... drainage pump, 58 ...
Drain pipe, 58a ... Drain riser pipe, 59 ... O-ring

Continuation of front page (56) Reference JP-A-60-102412 (JP, A) JP-A-63-151725 (JP, A) JP-A-61-196078 (JP, A) JP-A-57-69288 (JP , A)

Claims (2)

[Claims] 1. A gravity type marine structure installed on a sea bottom, wherein a bottom plate portion of the marine structure is divided into a main body side bottom plate and a base side bottom plate which supports the main body side bottom plate, and the base side bottom plate. And the body-side bottom slab are sealed, and the contact pressure is arbitrarily adjusted by applying water pressure to the gap between the contact surfaces of the foundation-side bottom slab and the body-side bottom slab, and the foundation is fixed against horizontal external force above a predetermined level. A sliding seismic isolation type offshore structure having a contact pressure adjusting function, which is configured to allow sliding on the contact surface between the side slab and the main body side slab and not slide against a horizontal external force of less than that. 2. A structure in which a gap between the contact surfaces and a constant water level basin installed in the offshore structure are connected by a pipe, and the contact pressure can be arbitrarily adjusted by the water level of the constant water level basin. A sliding seismic isolation type offshore structure having the described contact pressure adjusting function.