JPH0524304B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to the structure of the roof of a large concrete tank, particularly when the roof is a large tank for low-temperature liquefied gas and the roof is made of a dome made of prestressed concrete. This project concerns the structure and construction method of the part that connects the outer edge of the dome and the top of the side wall, and is primarily concerned with new issues in the field of construction technology, and is aimed at increasing energy efficiency through large tanks for storing fuel resources. The aim is to contribute to industry.

Conventional Technology Energy storage is a national concern, and interest in large tanks as storage facilities for low-temperature liquefied gases such as liquefied petroleum gas (LPG) and liquefied natural gas (LNG) is increasing, and construction technology is also changing. Correspondingly, progress has been made toward larger sizes in parallel with technology for low temperatures. In other words, in terms of tank capacity, a single LNG tank has a capacity of 130,000 kiloliters, and due to the location, the tank, which is underground, has side walls and bottoms that are several meters long, which reduces the temperature stress caused by low temperatures. A great deal of effort has been put into processing, and results have been achieved.

However, when it comes to tank roofs, the mainstream is still a steel frame structure consisting of membrane plates and frames, and it has become clear that there is a limit to increasing the size of tanks.

On the other hand, reinforced concrete buildings with large spans are designed with semicylindrical or dome-shaped roofs, and prestressing methods are also used in consideration of the characteristics of concrete. As for stress handling, there are known examples at nuclear facilities, so it may be possible to consider the use of prestressed concrete for large underground tanks, but at the same time, it is a challenge to deal with spans of several tens of meters and low temperatures. Overcoming this problem has not been achieved in Japan.

Problems to be Solved by the Invention Concrete is used for underground structures, especially cylindrical tanks, because of the characteristics of concrete, which acts as a compressive material under the pressure of the surrounding earth, and also as a storage tank for low-temperature liquefied gas. Its use largely depends on its durability. This durability can be utilized for storage tank roof slabs, but concrete as a flat plate requires a support structure, and at the same time, its own weight is a drawback, resulting in a heavy load on the steel structure and pillars for support. It is no longer suitable for spans.

Therefore, it is possible to design a concrete dome using a curved surface so that tension is not applied to the concrete, but a design using prestressing to deal with membrane stress has been carried out, and a ring provided on the outer periphery is used. Apply compressive force to the beam. This compression appears as a horizontal displacement of the peripheral edge, and simultaneously causes displacement of the side wall through the joint with the top of the side wall. In other words, the top of the side wall acts as a large restraint against the prestress of the roof, and not only does it have to carry an excessive external force due to the prestress of the dome, but this external force also affects the design of the side wall. Causes and consequences are interrelated.

Other problems arise from the construction side of large domes. In other words, large tanks have a depth of several tens of meters, and in order to construct a dome at the upper opening, it is necessary to erect shoring from the deep bottom, and the cost of temporary construction, including the cost of dismantling and transporting the dome, is high. If this is avoided and the opening is supported with steel frames, a full-fledged steel frame structure will be erected in a place that will no longer be needed after the concrete structure becomes self-supporting. In any case, the scale factor will have a large effect on the support for the underside of the concrete dome, and conditions will almost prohibit concrete construction.

Means for Solving the Problems In view of the above-mentioned problems in designing and constructing a large underground tank for low-temperature liquefied gas using reinforced concrete, the present invention proposes a structure in which the roof of a large cylindrical underground tank made of reinforced concrete is The roof dome is made of prestressed concrete and has a ring beam part made of prestressed concrete, and the prestressed cables are placed on the top surface of the side wall of the frame and arranged in the circumferential direction around the outer periphery of the roof dome. By joining together the annular body to form the roof part, the tank structure can be divided into the roof part and the side wall part of the frame, and furthermore, the bottom surface of the annular body and the top of the side wall A sliding mechanism made by stacking two steel plates vertically is placed between the surface and the annular body so that the annular body can slide against the side wall of the building frame when prestress is applied to the annular body. It is characterized in that it is configured to absorb horizontal displacement of the peripheral edge of the dome so that the influence of the introduction of prestress does not affect the side wall.

Furthermore, the present invention provides a tank roof structure divided into a roof part and a body side wall part as described above, in which a large number of connecting rods are provided upright on the top of the body side wall, and the connecting rods are connected to the roof structure. By providing a mechanism for connecting the roof portion to the side wall of the frame body, which is characterized by passing through a number of sleeves embedded vertically in the annular body according to the position, both sides can be connected with a simple structure. Another feature is that parts can be combined.

The present invention also provides a method for constructing a roof structure for a concrete underground tank equipped with the above-mentioned sliding mechanism, which comprises: (a) a ring in which a prestress cable is buried on the bottom of the constructed tank frame; A process of forming a prestressed concrete roof dome as precast concrete, which includes a beam part on the outer periphery and a prestress cable inside the roof dome, (b) a step of forming the roof dome from the ring beam part of the roof dome to the entire roof dome; (c) An annular body placed on the top surface of the side wall of the building frame via a sliding mechanism consisting of two steel plates stacked one above the other, and The process of constructing an annular body on which a prestressing cable is arranged so that it can slide against the side wall of the building frame when prestressing is introduced.

(d) lifting the roof dome from the bottom of the tank body along the side wall of the tank body and placing it at the position where it joins the annular body; (e) pouring concrete into the gap between the annular body and the ring beam to form the annular shape. (f) A process of introducing secondary prestress in the circumferential direction of the annular body and making the entire roof dome a prestressed concrete structure; (g) The annular body into which the above prestress has been introduced,
By providing a method for constructing a roof structure for a concrete underground tank that includes the step of fixing it at a position above the top surface of the side wall, the construction method reduces the scale factor of the shoring required for conventional dome construction as described above. It is also characterized by the fact that it has achieved the following.

Embodiments Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a cross-sectional view showing the structure of the roof periphery of the present invention, and FIG. 2 is a schematic diagram of a large concrete underground tank for low-temperature liquefied gas. In the figure, 1 shows the entire underground tank. Taking a 130,000 kiloliter tank as an example, it has a diameter of 65 m and a depth of 40 m. The planar shape is circular, the side wall 2 is designed to be 3 m thick, and the bottom plate 3 is designed to be 8 m thick. Most of them will be constructed by being buried below the ground level GL. 4 is a tank 1 installed between the tops of the side walls 2;
The roof is formed into a circular dome and is designed as a concrete dome with a rise D at the highest point in the center. Therefore, hereinafter the roof 4 will be referred to as a "roof dome".

Next, the details of the roof dome 4 will be explained with reference to FIG. 1. The roof dome 4, which is a concrete dome, consists of a sunken part 41 at the center, a haunch part 42 at its outer periphery, and a ring beam part 43 at its outer periphery. , In addition to placing reinforcing bars R for normal reinforced concrete,
Beam reinforcing bars RB are arranged in the ring beam section 43. This roof dome 4 is further prestressed.
It is designed as concrete (hereinafter abbreviated as PS), and has a prestressed cable P in the radial direction toward the center of the dome and a cable PB in the circumferential direction within the ring beam section 43, with the cable PB shown in the diagram. A prestress is introduced into the roof dome 4 by a post-tension method.

Next, 5 is the joint between the roof dome 4 and the side wall 2, which is the top of the side wall of the building structure, and the outer edge of the roof, and is formed into an independent annular body with a pentagonal cross section and a circular plane. be done. The shape of this annular body 5 is such that the lower surface 51 is connected to the top surface 2 of the side wall 2.
The slope 52 is folded upward inwardly, and the height of the inner surface is made equal to the height of the outer circumferential surface of the roof dome 4, that is, the outer circumferential surface 44 of the ring beam portion 43. This annular body 5 is also designed as a PS, and in addition to regular reinforcing bars (not shown), a prestress cable PC is arranged in the circumferential direction near the outer periphery, and it is configured as a ring beam. Note that in FIG. 1, a line 5 is drawn on the inner circumference of the annular body 5.
5 (dotted line 55 in FIG. 3) and a hatched area 54 is a part to be post-cast concrete when joining with the roof dome 4, as will be described later. An uneven surface for joining is provided near the outer circumferential surface 44 of 4 and the partition line 55, and a large number of multistage shear reinforcing bars RS provided on the dome side and the annular body 5 side are joined to each other at this portion. A partition line 55 is defined in the width of the post-cast concrete 54 in consideration of the anchoring part of the prestress cable PB of the ring beam part 43 and the dimensions of the uneven surface formation.

Next, to explain the connection of the lower surface 51 of the annular body 5 with the side wall 2, a supporting metal fitting 6 is provided at the center of the upper surface of the top surface 21 of the side wall 2, and joint plates 7 are laid on the inside and outside of the supporting metal fitting 6. ing. Support hardware 6
is the main part of the sliding mechanism that deals with the relative displacement of the two parts when prestress is introduced into a pair of two steel plates 61 and 62, and the opposing surfaces of each steel plate are made of Teflon (Polymer). DuPont's registered trademark for tetrafluoroethylene) processing is applied, and anchor bars into the concrete are welded to the back side. In the example where the side wall 2 is 3 m thick, steel plates 61 and 62 are used.
The width is 0.9m, the thickness is 4.5m, and the Teflon processing thickness is 50m.
It is micron. A flooded rubber sheet with a thickness of 10 m/m is selected for the joint plate 7. The inner joint plate 7 made of a rubber sheet is further divided into inner and outer parts at a groove 22 provided on the top surface 21, and a water stop plate 8, which is installed when concrete is poured for the side wall 2, is buried in the lower half between these parts. It has been launched. The water stop plate 8 is
A 2m/m thick stainless steel plate made of SUS304.
It has a corrugated part 81 in the center of the 900 m/m, and both edges are bent to form an anchor part 82, and the corrugated part 81 is located in the groove 22 and the groove 56 on the annular body 5 side, The space within the groove is filled with a synthetic resin foam (for example, "Esahome") 83 to enable the corrugated portion to deform. Reference numeral 9 denotes a sealing material for the main joint portion provided on the outer edge of the joint plate 7, which is made of an appropriate material and is later packed here to block rainwater and outside air. As described above, the underground tank 1 has a sliding mechanism between the frame and the roof.

Note that M in the figure is a seal plate for maintaining the airtightness of the roof after the tank 1 is completed.
The inner surface of the concrete is lined with a 6 m/m steel plate, and a deformable bend MC is provided at the corner of the joint between the annular body 5 and the side wall 2 to follow the relative displacement of the two.

Next, a second aspect of the invention will be described regarding a coupling mechanism between the annular body 5 and the side wall 2 with respect to the sliding mechanism at the top of the side wall.

During storage of normal low-temperature liquefied gas, the internal pressure of the boil-off gas is 0.15 kg/
^cm2 , which is approximately equal to the dome's own weight, so even if buoyancy acts between them, it is minimal.

In addition, the rise D of the roof dome 4 is 10 m, and the uplift due to negative pressure acting on the roof surface is small.
Can be ignored along with the above.

However, when the tank 1 encounters an earthquake, the roof dome 4 as the above-ground part receives a large horizontal force and moves completely independently of the frame parts such as the side walls 2. In particular, since the roof dome 4 employs a sliding mechanism for relative displacement with respect to the introduction of prestress, the top of the side wall is in an unrestrained state. Therefore, in the present invention, a coupling mechanism as shown in FIG. 3 is adopted. That is, 11 and 12 are large-diameter connecting rods that are welded and positioned to the reinforcing bars in the side wall 2, and stand upright in the required number with a length that protrudes beyond the top surface 57 of the annular body 5. A sleeve 13 passes through the body 5. Numeral 14 is a base plate applied to the top surface, and 15 is a tie beam on the base plate, and the connecting rods 11 and 12 are tied to the annular body 5 by nuts 16.

Reference numeral 25 indicated by a dotted line in FIG. 3 is a circular restraining wall formed upright from concrete on the outer periphery of the side wall 2, and 25A is a notch formed on the outer periphery of the lower surface of the annular body 5 corresponding to the restraining wall 25. Although this configuration is a well-known means for absorbing displacement between prestressed concrete and ordinary fixed concrete, it can be part of the coupling mechanism of the present invention, and the joint plate 7 can also be prestress cable pc
It is also possible to design a system that is compatible with

Function Next, the function of the present invention and the invention of the third construction method will be explained by referring to the steps of tank construction. When constructing a large underground tank, the underground portion thereof can be constructed using known construction methods, and usually a continuous underground wall W is constructed first. In other words, as shown in the left half of Figure 2, the ground surface GL
A groove T is excavated from above on the outer periphery of the side wall 2, concrete is poured into it to construct a continuous underground wall W, and then the wall body 2 is constructed and the bottom plate 3 is poured.

Next, a cent form C for the roof dome 4 is assembled on the upper surface of the bottom plate 3 inside the constructed tank, and its upper surface is formed into a curved surface matching the lower surface of the roof dome 4. Then, the reinforcing bars R and RB are placed in the specified locations, the sheaths for the prestress cables P and PB are placed, and concrete is poured.After the concrete hardens, the cables P and PB are inserted into each sheath and posted. If prestress is introduced into the dome concrete by tension,
Roof dome 4 will be completed as a single, sunken-shaped precast concrete block of PS.

Meanwhile, at the top of the side wall 2, an annular body 5 is constructed.
To do this, as shown in Fig. 3, after configuring the above-mentioned sliding mechanism on the top of the side wall 2,
1 and inner formwork F2, and steel vertical butterfly 23A,
23B to the top of the side wall 2 with anchor bolts 24. Next, the sleeve 13 is inserted into the connecting rods 11 and 12 that stand upright from the side wall 2, and concrete for the annular body 5 is poured. In that case, lot line 5
A concavo-convex portion 58 is formed on the outside of 5.

Once the annular body 5 is completed, the connecting rods 11 and 12
A tensioning beam 15 is stretched across the frame and tightened with a nut 16 to fix the annular body 5 to the top of the side wall 2, and then a lifting jack J is installed using the tensioning beam 15. (Fig. 2) Next, a lifting wire is attached to the concrete roof dome 4 constructed from the tank bottom, and its upper end is attached to the jack J, so that the roof dome 4 is suspended around the entire upper surface of the annular body 5. The roof dome 4 is gradually lifted vertically by scanning the jack J. This reaction force is of course received by the side wall 2 via the annular body 5.

Once the roof dome 4 has been raised to a predetermined height, the jack J is held there, and the upper rising part F2A of the inner formwork F2 is dismantled and a mold is placed on the part that will become the lower surface of the post-cast concrete 54, as shown in the third figure. Frame F
Supplementing 2B, ring beam part 4 of roof dome 4
A shear reinforcing bar RS is connected between the outer circumferential surface 44 of No. 3 and the division line 55 of the annular body 5, and post-cast concrete 54 is placed. It is preferable to use non-shrinkage concrete as this concrete, and it is also advantageous for the division line 55 to be a slope that opens upward and slightly outward.

When the post-cast concrete 54 completely hardens, the roof dome 4 and the annular body 5 become an integral concrete roof part and are supported on the side wall 2 (right half of Fig. 2). 12 can be loosened, allowing prestress to be applied to the entire roof. Therefore, prestress is introduced into the prestress cable PC in the circumferential direction of the annular body 5. This prestress external force becomes a second prestress on the roof dome 4,
The precast dome 4 is constructed after the first prestress is introduced during construction, and then during lifting and the annular body 5.
After passing through the stress state at the time of joining, a prestress is applied to the final state, and during this process it behaves in the direction of the dome's upheaval, allowing it to be designed in a stable state as a dome.

During this time, the annular body 5 contracts in the circumferential direction due to prestressing, reducing its radius and increasing the radius of the annular body 5 to the top surface of the side wall 2.
1 and is displaced inward (arrow in Figure 1). and,
This displacement is absorbed by a sliding mechanism mainly consisting of the supporting hardware 6, and the steel plates 61 and 62 are treated with Teflon so that they move relative to each other and slide.

The displacement of the annular body 5 affects the water stop plate 8 whose upper half is buried in concrete and whose lower half is buried in the side wall 2, but since the water stop plate 8 deforms without much resistance at its corrugated portion 81. , displacement can be followed, and the airtightness and liquidtightness of the joints are ensured.

Similarly, the relationship between the thickness of the connecting rods 11 and 12 and the inner diameter of the insertion sleeve 13 is designed to accommodate the above displacement, so that displacement due to tension in the cable PC will not cause shearing of the connecting rods 11 and 12. can do. The deformation displacement of the annular body 5 due to the second prestress applied to the first prestress of the ring beam part 43 is designed to be on the order of about 5 cm on the radius, and the corrugated part 81 of the water stop plate 8, The design of the groove portions 22 and 56 containing the grooves can also be designed effectively to absorb the displacement of prestress. Further, even when the restraining wall 25 is provided, the roof portion can be freely displaced inward.

Once the roof concrete in which the annular body 5 and the roof dome 4 are integrated is stabilized as prestressed concrete through the above steps, grout is injected into the sleeve 13 to fix the connecting rods 11 and 12, and tighten the Connecting rod 1 via beam 15
Once 1 and 12 are fixed, the tank body and roof are stably joined together by the above-mentioned joining mechanism, and a tank having a PS dome roof is completed.

Effects of the Invention As described above, the present invention connects the roof and the frame of a large underground tank by providing a coupling mechanism and a sliding mechanism between the two.
It is possible to overcome all the problems associated with constructing a large-span roof dome with prestressed concrete, opening up a new path for future storage facilities, and also developing a construction method suitable for such structures. It can be said that it will make a great contribution to the construction industry and ultimately the energy industry.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a detailed sectional view mainly showing the sliding mechanism at the joint between the body and roof of a circular underground tank;
Figure 2 is a cross-sectional view along one diameter showing the general structure of the underground tank and the construction of the roof section on the left and right halves, and Figure 3 is a detailed cross-sectional view mainly showing the coupling mechanism at the same position as Figure 1. It is. 1...tank, 2...side wall, 3...bottom plate, 4...
...Roof dome, 43...Ring beam section, 44...
...Outer peripheral surface, 5... Annular body, 51... Lower surface, 54...
...Post-cast concrete, 55... Lot line, 6...
Sliding mechanism, 61, 62... steel plate, 7... joint plate,
8...Water stop plate, 81...Corrugated part, 9...Sealing material, 11, 12...Joining rod, 13...Sleeve, 15...Tightening beam, F1, F2...Formwork, 25...Suppression Wall, P, PB, PC...Prestress cable.

Claims (1)

[Scope of Claims] 1. In the roof structure of a large cylindrical underground tank made of reinforced concrete, the roof includes a roof dome 4 made of prestressed concrete and having a ring beam part 43 made of prestressed concrete on the outer periphery, and a side wall 2 of the frame. An annular body 5 placed on the top surface 21 of the body and having a prestress cable (PC) arranged in the circumferential direction is integrally joined to the bottom surface 51 of the annular body 5 and the top of the side wall 2. Face 21
A sliding mechanism 6 formed by stacking two steel plates 61 and 62 vertically is disposed between the annular body 5 and the annular body 5.
A roof structure for a concrete underground tank, characterized in that the annular body 5 is configured to be able to slide against a side wall 2 of a frame when prestress is introduced into the tank. 2 Between the lower surface 51 of the annular body 5 and the top surface 21 of the side wall 2, there is a water stop plate 8 having an elastic joint material 83 buried across both surfaces and a corrugated portion 81.
A roof structure for a concrete underground tank according to claim 1, wherein the roof structure is provided with: 3. In the roof structure of a large cylindrical underground tank made of reinforced concrete, the roof includes a prestressed concrete roof dome 4 having a prestressed concrete ring beam part 43 on the outer periphery, and a top surface 21 of the frame side wall 2. The frame side wall 2 has a plurality of connecting rods 11, 12 standing upright on its top 21. A roof structure for an underground concrete tank, characterized in that the connecting rods 11 and 12 are inserted through a plurality of sleeves 13 vertically buried in the annular body 5 according to their positions. 4 The annular body 5 and the frame side wall 2 are injected with filling grout for fixing the connecting rods 11 and 12 into the sleeve 13, and the connecting rods 11 and 12 are connected to the top surface 57 of the annular body 5 using a tightening beam 15. The roof structure of a concrete underground tank according to claim 3, wherein the roof structure is fixed by tightening to the annular body 5. 5. The frame side wall 2 is provided with a restraining wall 25 raised up on the outer periphery of its top surface 21, and the annular body 5 is provided with a notch 25A on its lower surface for accommodating the restraining wall. Roof structure of the concrete underground tank described in paragraph 4. 6 In the construction method when forming the roof of a large cylindrical underground tank made of reinforced concrete into a dome made of prestressed concrete, (a) a ring beam with a prestressed cable buried on the bottom plate 3 within the constructed tank frame; Part 4
3 on the outer periphery and a prestressed cable inside the roof dome. Step of introducing primary prestress, (c) two steel plates 61 on the top surface 21 of the side wall 2 of the frame;
The annular body 5 is mounted via a sliding mechanism 6 formed by overlapping two parts 62 vertically, and a prestress cable (PC) is disposed along the circumferential direction, and when prestress is introduced, the annular body 5 is placed on the frame side wall 2. (d) lifting the roof dome 4 from the bottom of the tank body along the side wall 2 of the tank body and fixing it at the joining position with the annular body 5; (e) Concrete is poured into the gap between the annular body 5 and the ring beam part 43 to connect the annular body 5 and the roof dome 4.
(f) A process of introducing secondary prestress in the circumferential direction of the annular body 5 and making the entire roof part of prestressed concrete; (g) Annular body 5 into which the above prestress is introduced
A method for constructing a roof structure for a concrete underground tank, comprising the step of fixing the above at a position on the top surface 21 of the side wall.