JP7668178B2 - How to build structures - Google Patents

Description

The present invention relates to a method for constructing a structure and the structure itself.

In prestressed concrete tanks (hereafter referred to as PC tanks), vertical tension members are installed inside the walls for reinforcement. Multiple vertical tension members are placed at regular intervals around the circumference of the tank.

The prestressing steel wires are sometimes arranged in a U-shape as vertical tension members. In this case, after constructing a wall with a U-shaped sheath embedded in it, the top edge of the wall is used as a work space to insert tension members into the sheath, and tension is applied using a post-tensioning method (see, for example, Patent Document 1).

JP 2018-109318 A

However, the construction procedure for inserting the tendons into the U-shaped sheath was complicated, and required large equipment such as a crane and a device for pulling the tendons. There was also an issue of limited freedom in the placement of the tendons.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a method for constructing a structure that allows for easy placement of tension members, and a structure, etc.

In order to achieve the above-mentioned object, the present invention provides a method for constructing a structure, comprising the steps of: constructing a foundation having an anchoring hole; constructing a wall having an insertion hole communicating with the anchoring hole on the foundation; inserting a PC steel member consisting of a bundle of multiple PC steel strands into the insertion hole and the anchoring hole; filling the anchoring hole with a filler material to anchor the lower ends of the PC steel strands to the foundation; and tensioning the upper ends of the PC steel strands to anchor them to the wall, wherein the lower ends of the multiple PC steel strands are provided with enlarged diameter portions, the heights of the enlarged diameter portions vary depending on the PC steel strands , the foundation is formed of concrete, and the lower ends of the anchoring holes are located within the concrete of the foundation .
The fixing hole is, for example, linear.

In the present invention, the fixing hole in the foundation and the insertion hole in the wall are connected, a tension member such as a PC steel strand is inserted, and the fixing hole is filled with a filling material to fix the lower end of the tension member to the foundation. The tension member can be inserted into the insertion hole and the fixing hole while hanging down from the wall side, so construction is easy, and there is no need for the time and effort required when arranging the tension member in a U-shape, and there is a high degree of freedom in arranging the tension member. In addition, by filling the fixing hole with a filling material, the lower end of the tension member can be easily fixed to the foundation, and by fixing the upper end of the tension member to the wall after tensioning it, prestress can be suitably introduced into the wall.

It is desirable that the wall is a wall of a tank, and that the wall is constructed by installing precast blocks having the insertion holes in multiple layers, one above the other.
The method of the present invention can be suitably used, for example, when constructing a tank wall from precast blocks, and prestressing by tendons can be easily introduced into the tank wall.

In the present invention , the cross section of the lower end of the PC steel strand can be enlarged at the position of the enlarged diameter section, improving the anchoring effect of the PC steel strand to the base section and reducing the anchoring length.

According to the present invention, a structure is constructed comprising a foundation having an anchoring hole, and a wall body constructed on the foundation having an insertion hole communicating with the anchoring hole, wherein a tension member for introducing prestress into the wall body is inserted into the insertion hole and the anchoring hole, the lower end of the tension member is fixed to the foundation by filling material filled in the anchoring hole, and the upper end of the tension member is fixed to the wall body.

The present invention provides a method for constructing a structure that allows for easy placement of tension members, and the structure itself.

A diagram showing the PC tank 10. A diagram showing the process of constructing a wall 20. A diagram showing the anchoring portion of the PC steel strand 3. A diagram showing PC steel strands 3. Another example of the arrangement of PC steel strands 3a. Another example of the fixing hole 11. An example of constructing a wall 20 using cast-in-place concrete. An example of using PC steel bar 3b as tendon.

The following describes in detail a preferred embodiment of the present invention with reference to the drawings.

Figure 1 shows a PC tank 10, which is a structure constructed using a construction method according to an embodiment of the present invention.

The PC tank 10 is a tank that has a cylindrical wall 20 made of precast blocks 2 (hereinafter sometimes referred to as "blocks") on a foundation slab 1, and stores materials such as LNG (Liquefied Natural Gas) inside. A steel roof 30 is provided on the upper end of the wall 20.

PC steel strands 3 are buried in the wall 20, and their lower ends are fixed into the base plate 1. The PC steel strands 3 are vertical tension members, and multiple strands are provided at intervals around the tank circumference. Only some of these PC steel strands 3 are shown in Figure 1.

To construct the PC tank 10, as shown in FIG. 2(a), a base plate 1 is constructed, and then a block 2 is placed on top of the base plate 1. The base plate 1 is the foundation of the wall body 20, and is constructed from a disk-shaped concrete member.

The base plate 1 is provided with an anchoring hole 11 for inserting the lower end of the PC steel strand 3. The anchoring hole 11 is formed, for example, by embedding a linear sheath vertically into the concrete of the base plate 1. A plurality of anchoring holes 11 are provided at predetermined intervals around the tank circumference to match the arrangement of the PC steel strand 3.

The block 2 is a concrete member prefabricated in a factory or the like, and has insertion holes 21 for inserting the PC steel strands 3. The insertion holes 21 are formed, for example, by embedding a linear sheath vertically into the concrete of the block 2. The insertion holes 21 are provided at positions corresponding to the fixing holes 11 of the base slab 1, and when the block 2 is installed on the base slab 1, the insertion holes 21 of the block 2 communicate with the fixing holes 11 of the base slab 1.

The blocks 2 are arranged in a row in the circumferential direction of the tank on the base plate 1, and are installed in multiple layers up and down on the base plate 1 to the required height, as shown in Figure 2(b). This creates a wall body 20 made of blocks 2. The insertion holes 21 communicate between the upper and lower blocks 2.

After constructing the wall body 20 as shown in FIG. 2(b), the PC steel strands 3 are hung from the top of the wall body 20 into the insertion holes 21 of each block 2 that are connected vertically, and their lower ends are inserted into the fixing holes 11 of the base plate 1.

After the PC steel strands 3 are placed in this manner, the lower ends of the PC steel strands 3 are fixed in the fixing holes 11 of the foundation slab 1. FIG. 3(a) is a diagram showing the fixing portion of the PC steel strands 3. In this embodiment, the fixing holes 11 into which the lower ends of the PC steel strands 3 are inserted are filled with a filler 4, so that the lower ends of the PC steel strands 3 are fixed to the foundation slab 1. As the filler 4, for example, a cement-based material such as mortar is used, but the filler is not limited to this. In addition, by using a higher-strength filler ⁴ such as non-shrink mortar for PC grout having a compressive strength of 30 N/mm2 or more, the adhesion strength of the PC steel strands 3 can be increased and the fixing length can be reduced.

The base plate 1 is provided with an injection hole 41 that connects the surface of the base plate 1 to the bottom of the fixing hole 11, and an overflow pipe 42 that connects the surface of the base plate 1 to the top of the fixing hole 11. The filler material 4 is injected into the fixing hole 11 from the injection hole 41 and overflows from the overflow pipe 42 onto the surface of the base plate 1. This ensures that the filler material 4 is filled up to the top of the fixing hole 11. As shown in Figure 3(b), instead of the overflow pipe 42, a groove 42a with a similar function can be provided on the surface of the base plate 1.

Figure 4 (a) is a diagram showing a portion of the lower end of the PC steel strand 3. The PC steel strand 3 is formed by twisting multiple steel wires together in a spiral shape, and multiple PC steel strands 3 are bundled in parallel to be used as a multi-strand (PC steel material). A crimping grip 32 is provided at the lower end of the PC steel strand 3. In this embodiment, the crimping grip 32 forms an expanded diameter portion in the PC steel strand 3. However, as described below, it is also possible to form the expanded diameter portion using another metal fitting or the like.

Figure 4 (b) is a diagram showing the cross section of the multi-strand at the position of the crimping grip 32. The crimping grip 32 expands the diameter of the PC steel strand 3, which increases the cross section of the multi-strand and makes it easier for the filler 4 to fill the gaps in the PC steel strand 3, improving the fixing effect of the PC steel strand 3 and reducing the fixing length.

In this embodiment, the number and arrangement of the crimping grips 32 provided on the cross section of the multi-strand are set so that the cross section of the multi-strand does not become too large and interfere with insertion into the insertion hole 21 of the block 2 or the fixing hole 11 of the base plate 1.

The number and arrangement of the crimping grips 32 provided on one PC steel strand 3 are not particularly limited. For example, multiple crimping grips 32 can be attached at different heights on one PC steel strand 3. It is also possible to form an expanded diameter portion on the PC steel strand 3 using metal fittings other than the crimping grips 32. For example, when the number of PC steel strands 3 in a multi-strand is small, it is possible to form an apartment-type expanded diameter portion 32a by crimping a thick-walled cylindrical tube so that it circumscribes the PC steel strands 3, as shown in Figure 4 (c). A similar expanded diameter portion 32a can also be provided on some of the PC steel strands 3 in a multi-strand.

As shown in Figure 3, the lower end of the PC steel strand 3 is fixed to the base plate 1, and then the upper end of the PC steel strand 3 is tensioned at the top end of the wall body 20. Then, as shown in Figure 2 (c), the upper end of the PC steel strand 3 is fixed to the block 2 at the upper end of the wall body 20 by the fixing device 33, and the insertion hole 21 is filled with the filler material 4. After this, the other parts required for the PC tank 10 are provided, and the PC tank 10 is constructed.

As shown in FIG. 3, the block 2 at the lower end of the wall body 20 has an injection hole 43 that connects the surface of the block 2 to the bottom of the insertion hole 21, and the filler material 4 is injected from the injection hole 43 into the insertion hole 21, filling the insertion hole 21 of each block 2 from below. This allows the filler material 4 to be reliably filled into the insertion hole 21 while maintaining the quality of the filler material 4.

As described above, in this embodiment, the fixing holes 11 in the foundation plate 1 and the insertion holes 21 in the wall body 20 are connected, the PC steel strands 3 are inserted, and the fixing holes 11 are filled with the filler 4 to fix the lower ends of the PC steel strands 3 to the foundation plate 1. The PC steel strands 3 can be inserted hanging down from the wall body 20 side and inserted into the insertion holes 21 and the fixing holes 11, so construction is easy, there is no need for the time and effort required when arranging tension members in a U-shape, and there is a high degree of freedom in the arrangement of the PC steel strands 3.

Furthermore, by filling the fixing holes 11 with the filler 4, the lower end of the PC steel strand 3 can be easily fixed to the base plate 1, and by fixing the upper end of the PC steel strand 3 to the wall body 20 after tensioning it, prestress can be suitably introduced to the wall body 20.

In addition, in this embodiment, by attaching a crimping grip 32 to the lower end of the PC steel strand 3 to provide an enlarged diameter section, the cross section of the lower end of the PC steel strand 3 can be enlarged at the position of the crimping grip 32. Also, gaps are created between the PC steel strands 3, making it easier for the filler material 4 to enter, improving the fixing effect of the PC steel strand 3 to the base plate 1 and reducing the fixing length.

However, the present invention is not limited to the above embodiment. For example, in the PC tank 10, a short PC steel strand may be placed at the lower end of the wall body 20 for the purpose of densely arranging tension members at the lower end of the wall body 20. In such a case, as shown in FIG. 5(a), when the block 2 at the lower end of the wall body 20 is installed, a short PC steel strand 3a may be placed in the same manner as described above, its lower end may be fixed to the base plate 1, and the upper end of the PC steel strand 3a may be tensioned and fixed to the block 2 at the lower end of the wall body 20 by a fixing device 33. The wall body 20 is constructed by stacking further blocks 2 on top of the block 2 as shown by the dashed line.

As shown in FIG. 5(b), the lower end of the wall 20 may have a haunch 22 on the outside. In such a case, the insertion hole 21 of the block 2 and the fixing hole 11 of the base plate 1 may be formed diagonally along the slope of the haunch 22, and the PC steel strand 3a may be inserted diagonally into these insertion holes 21 and fixing holes 11. In the example shown in the figure, the upper end of the PC steel strand 3a is fixed to the inner surface of the lower end of the wall 20, and tensioning can be performed after the block 2 at the lower end of the wall 20 is placed, as well as after the wall 20 is constructed. In addition, the PC steel strand 3 that runs the entire length of the wall 20, as in the above-mentioned embodiment, is provided separately at a position different from the PC steel strand 3a in both cases of FIG. 5(a) and (b).

Furthermore, by making the sheath embedded in the base plate 1 frustum-shaped, it is possible to make the anchoring holes 11 frustum-shaped, widening from the top to the bottom, as shown in Figure 6. This improves the anchoring effect of the PC steel strands 3.

In addition, in this embodiment, the wall 20 is constructed using precast blocks 2, but the method of the present invention can also be applied to constructing the wall 20 by pouring concrete on-site, and the insertion hole 21 can be formed by embedding a previously installed sheath in the concrete.

In this case, for example, after constructing the base plate 1 in the same manner as above, concrete is poured in place to construct the wall body 20 as shown in Figure 7. At this time, the sheath installed beforehand is embedded in the concrete to form insertion holes 21, and the PC steel strands 3 are inserted into the insertion holes 21. Thereafter, the PC steel strands 3 are fixed and tensioned in the same manner as above, thereby introducing prestress into the wall body 20.

The method of the present invention can be suitably used when constructing the wall 20 of the PC tank 10, and can easily introduce prestress into the wall 20 using the PC steel strands 3. However, the method of the present invention is not limited to this, and can be applied to tanks other than the PC tank 10, and its use is not limited to storing LNG. The planar shape of the tank is not particularly limited, and it can be applied to tanks other than circular. Furthermore, it can be applied to structures other than tanks, and can be applied to all cases where a wall is constructed on a foundation and prestress is introduced into the wall using tendons, such as retaining walls, box culverts, and U-shaped culverts. For example, in the case of a box culvert or U-shaped culvert, the method of the present invention can be applied when forming a side wall on the bottom plate, which is the foundation.

The tension member is not limited to the PC steel strand 3. For example, PC steel bars can be used as tension members. In this case, as shown in FIG. 8(a), after constructing the base plate 1 in the same manner as described above, a block 2 is placed on the base plate 1, and a short PC steel bar 3b is inserted into the insertion hole 21 of the block 2, and its lower end is fixed to the fixing hole 11 in the same manner as described above. It is also possible to provide an anchor (not shown) at the lower end of the PC steel bar 3b to form an enlarged portion and improve the fixing effect for the filler material 4 in the fixing hole 11. On the other hand, a coupler joint 34 is provided at the upper end of the PC steel bar 3b. Then, as shown in FIG. 8(b), an upper block 2 is placed on the lower block 2, and as shown in FIG. 8(c), the PC steel bar 3b is inserted into the insertion hole 21 of the upper block 2, and its lower end is connected to the coupler joint 34.

By repeating the above-mentioned process of installing blocks 2 and connecting PC steel bars 3b, the PC steel bars 3b can be extended to any desired height, and there is no need to hang the PC steel strands 3 from the top of the wall body 20. The PC steel bars 3b can be extended up to the top of the wall body 20, but in this example, after connecting two PC steel bars 3b, one above the other, tension is applied to the connected PC steel bars 3b as shown in Figure 8 (d), and their upper ends are fixed to the top surface of the second block 2. The remaining blocks 2, shown by dashed lines, are then installed in the upper tier to construct the wall body 20. The tensioning material that reaches the top of the wall body 20 is provided separately at a different position from the PC steel strands 3a.

In the example of Figure 8, blocks 2 are used, but instead of installing blocks 2 in multiple stages, it is also possible to pour on-site concrete in multiple layers, and in the explanation of Figure 8 above, "installation of blocks 2" can be read as "pouring and hardening of concrete." The insertion hole 21 for passing the PC steel rod 3b can be formed by burying a sheath pipe in the concrete.

The above describes preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to these examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas disclosed in this application, and it is understood that these also naturally fall within the technical scope of the present invention.

1: Base plate (base part)
2: Precast block 3, 3a: PC steel strands (tension material)
4: Filler 10: PC tank (structure)
11: Fixing hole 20: Wall body 21: Insertion hole 30: Roof portion 32: Crimp grip (enlarged diameter portion)
33: Fixing tool

Claims (3)

constructing a foundation having fixing holes;
A step of constructing a wall body having an insertion hole communicating with the fixing hole on the foundation portion;
A step of inserting a PC steel member formed by bundling a plurality of PC steel strands into the insertion hole and the fixing hole;
A step of filling the fixing hole with a filler material to fix the lower end of the PC steel strand to the foundation part;
A step of tensioning the upper end of the PC steel strand and fixing it to the wall body;
Equipped with
An expanded diameter portion is provided at the lower end of each of the plurality of PC steel strands , and the height of the expanded diameter portion varies depending on the PC steel strand ;
A method for constructing a structure, characterized in that the foundation is formed of concrete, and the lower end of the fixing hole is located within the concrete of the foundation . The wall is a wall of a tank,
2. The method for constructing a structure according to claim 1, wherein the wall is constructed by installing precast blocks having the insertion holes in multiple layers, one above the other. The method for constructing a structure according to claim 1 or 2 , characterized in that the fixing holes are linear.

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