JP3754698B1 - Steel tower basic structure - Google Patents

Abstract

[PROBLEMS] To reduce the construction time, reduce the amount of excavation, and reduce the amount of concrete placement by enabling the foundation to be scaled down in a foundation structure with multiple piles with relatively small diameters installed in the ground. To provide a foundation structure of a steel tower that can be used.
In a foundation structure of a steel tower in which a plurality of pile bodies 1, 1... Placed in the ground and a main pillar 2 of the steel tower are joined via a concrete structure 3, the concrete structure 3 is A structure formed by placing concrete 6 in a steel pipe 5 having a plurality of steps in the vertical direction, with ribs 4, 4... The tops of a plurality of piles 1, 1... Placed in the ground are joined to the lower side of the concrete structure 3, and the lower main surface of the tower main pedestal 2 is supported in multiple steps. It is assumed that the main pedestal column portion K provided with the pressure plates 7, 7... Is embedded in the concrete structure 3.
[Selection] Figure 1

Description

  The present invention relates to a steel tower foundation structure in which a plurality of pile bodies placed in the ground and a main pillar of a steel tower are joined via a concrete structure.

  As a foundation structure for supporting the main pedestal of the steel tower, when the support layer is relatively deep, as shown in FIG. 6, a plurality of pile bodies 50, 50. Thereafter, a footing 51 is formed of reinforced concrete so as to be connected to the tops of these piles 50, 50... And a method of connecting the footing 51 and the main pedestal 52 of the steel tower is generally used (the following patent document). 1 etc.).

The fixing structure between the footing 51 and the main pedestal 52 is roughly divided into a bolt fixing method, a contact material fixing method, and a pressure plate fixing method. As shown in FIG. 6, the bolt fixing method is a method in which a base plate 53 provided on the bottom surface of the main pedestal 52 is fixed by a plurality of anchor bolts 54, 54... 7 (A) to (C), a mounting plate 56 is fixed to the lower peripheral surface of the main pedestal embedded in the footing 51 by welding or the like, and a pair of left and right angles sandwiching the mounting plate 56 A fixing method in which a plurality of bolts 57 and 57 are joined to each other at a plurality of locations around the periphery, and the support plate fixing method includes the bottom surface of the main pedestal 52 embedded in the footing 51 and / or the support plate fixing method as shown in FIG. In this method, fixing is performed by ring-shaped pressure bearing plates 58, 58,... Provided on the outer surface so as to protrude outward.
On the other hand, as shown in FIG. 9 (A), the jointing method between the footing and the pile head is a ring shape provided so as to protrude outward on the outer surface of the pile head immersed in the footing 51. The bearing plates are fixed by the bearing plates 59, 59, and a plurality of reinforcing bars 60, 60 are disposed so as to straddle the pile head and the footing 51 as shown in FIG. 9B. Reinforcing bar joining method is used.

On the other hand, in order to simplify the foundation structure, in Patent Document 2 below, steel pipe piles 70, 70... For rotary press-fit having excavation blades larger than the pile diameter at the lower end are pressed into the ground in an oblique direction. In the steel tower foundation structure that is connected and fixed to the lower end of the steel tower leg 71 at the upper end of the steel pipe piles 70, 70 for rotary press fitting, the steel pipe pile 70 for rotary press fitting installed in the ground in an oblique direction; A steel tower foundation structure has been proposed in which the steel tower legs 71 extending upward are linear.
Japanese Patent Laid-Open No. 9-3882 JP 2003-166254 A

  In the foundation of the power transmission tower, as shown in FIG. 11, it is more strongly affected by the wire tension, the typhoon, the seasonal wind and the like than the influence of the weight of the tower and the weight of the wire. Become. As a result, the overturning moment becomes larger than the total compressive load due to other factors, so compression load acts on the leeward steel tower legs, while compressive load (pushing force) acts on the leeward steel tower legs. About 70% of the lifting load (pullout force) is applied. Further, a bending moment is applied by a couple of forces due to the pushing force and the pulling force, and a horizontal force is applied.

Therefore, in the foundation (footing) for supporting the tower leg, as shown in FIG. 12, if the footing becomes too shallow in the fixing portion of the main pedestal 52 and the footing 51, the base of the main pedestal 52 is centered. The corn-like shear crack 61 may be generated and the fixing portion may be destroyed. As shown in FIG. 13, when the pile body 50 is too close to the outer edge of the footing 51, split crack-like shear cracks 62, 62,... is there. Furthermore, when the footing is too thin, there is a problem that a cone-shaped shear crack 61 may occur around the pile body 50 as shown in FIG.
Therefore, if the footing 51 is designed so as to have sufficient proof strength against these pushing force, pulling force, bending moment, and horizontal force so as not to cause cracks, the footing scale becomes large and the footing becomes large. As a result, the amount of excavation increased and the amount of concrete placement increased, which caused much time and labor for the construction.

  On the other hand, in the case of the foundation structure described in Patent Document 2, since there is no footing, the above-mentioned problems will be solved. However, in order to place a large-diameter steel pipe pile 70 in the ground, a large size is required. Heavy machinery is necessary, and there is a problem that it cannot be adopted or is difficult to construct a steel tower foundation particularly in a mountainous area.

  Therefore, the main problem of the present invention is to reduce the construction time, reduce the amount of excavation, and reduce the amount of excavation by making the foundation smaller in the foundation structure type in which a plurality of pile bodies with relatively small diameters are installed in the ground. The purpose is to provide a foundation structure for a steel tower that reduces the amount of casting.

In order to solve the above-mentioned problem, as the present invention according to claim 1, in a foundation structure of a steel tower in which a plurality of pile bodies placed in the ground and a main pedestal of a steel tower are joined via a concrete structure. ,
The concrete structure is a structure formed by placing concrete in a steel pipe having a plurality of steps in the vertical direction with a rib for fixing a slippage fixed on the inner wall surface along the circumferential direction, A top portion of a plurality of pile bodies placed in the ground is joined to the lower side of the concrete structure, and a fixing member is provided at a lower portion of the main tower pillar, and the fixing member is provided. A foundation structure of a steel tower is provided in which a main pedestal column portion is embedded in the concrete structure.

In the present invention described in claim 1, first, as a concrete structure for joining a plurality of pile bodies placed in the ground and a main pedestal of a steel tower, the inner wall surface is fixed along the circumferential direction. It is set as the structure formed by placing concrete in the steel pipe which has the rib for ribs provided in multiple steps in the up-down direction.
Conventionally, the design of the anchoring part of the tower main pedestal was reinforced by the anchoring strength based on the allowable tensile stress and allowable shear stress of the concrete, but it is predicted that it will not be sufficient from safety detection. In some cases, in order to further improve the fixing strength, reinforcement based on empirical rules has been made, and thus over-reinforcement was sometimes made. In view of this situation, the present applicant has conducted extensive studies on efficient foundation design and reinforcement. As a result, as disclosed in JP 2000-345571 A, continuous stress acts on the main pedestal. Then, horizontal cracks and vertical cracks (split cracks) occur in the concrete. And in the case of the support pressure fixing method, it is greatly affected by the occurrence of the above-mentioned split crack, and when this split crack occurs, the knowledge that even if one of them reaches the foundation surface, it will break down. I came to get. In addition, the inventors of the present application dramatically improve the fixing strength by reinforcing the direction perpendicular to the split crack, that is, the circumferential direction of the main pedestal with a steel pipe, and improving the restraint of the concrete to suppress split fracture. What we can do is gained from a dozen model experiment and numerical analysis.

  Accordingly, if it is possible to suppress the split crack as much as possible, the fixing strength can be improved and the joint portion (foundation portion) can be reduced, so that a concrete structure having the above structure is formed. The tops of a plurality of pile bodies placed inside are joined, a fixing member is provided at the lower part of the main tower pillar, and the main pillar part provided with the fixing member is embedded in the concrete structure The basic structure is the same.

  As a result, by constraining the concrete on which the steel pipe is placed from the outside (periphery), split cracks can be prevented, and the anchoring strength of the concrete structure can be greatly improved. Since it can be arranged close to the wall surface, the scale of the concrete structure can be greatly reduced. In addition, since the scale of the concrete structure can be reduced, the construction time can be shortened, the excavation amount can be reduced, and the concrete placement amount can be reduced.

  Furthermore, by using a concrete structure composed of the steel pipe and concrete, it is possible to easily install a plurality of piles and to easily absorb construction errors of main piles and sub-piles. Become.

  As the present invention according to claim 2, the foundation structure of the steel tower according to claim 1, wherein the plurality of pile bodies are small-diameter piles having a diameter of 400 mm or less or a diameter of 1/6 or less of the steel pipe diameter. The As the pile body, it is desirable to arrange a plurality of, preferably 4 to 6, small-diameter piles having a diameter of 400 mm or less or a diameter of 1/6 or less of the steel pipe diameter as compared with the large-diameter pile. Especially in mountainous areas, large heavy machinery cannot be brought in. Therefore, it is recommended to create as many small-diameter piles as necessary on the ground using a small drilling machine. The small-diameter pile may be a cast-in-place pile or a steel pipe pile, which will be described in detail later.

  As a third aspect of the present invention, the rib for preventing misalignment is disposed on the upper side and the lower side, respectively, with respect to the bearing plate arrangement portion of the main tower pillar. A foundation structure of the steel tower is provided.

  In the present invention described in claim 3, the misalignment prevention ribs are arranged on the upper side and the lower side, respectively, with the bearing plate arrangement part of the buried part of the main tower pillar as a boundary. Is. The load from the main pedestal acting on the concrete structure has both cases of indentation force and pull-out force depending on the direction of wind load and seismic load. In order to function effectively, it is preferable that the support plate is disposed on the upper side and the lower side of the support plate placement site.

  As the present invention according to claim 4, the foundation structure of the steel tower according to any one of claims 1 to 3, wherein most of the concrete structure is embedded in the ground.

  The concrete structure can be built in a form to be placed on the ground. However, in order to suppress the displacement of the foundation, a footing can be embedded in the ground and the displacement can be suppressed by earth pressure resistance. It is desirable to build in state.

  In the present invention according to claim 5, when the diameter of the tower main pedestal column is φ, the section length of the bearing plate in the tower main pedestal column is L, and the inner diameter of the steel pipe is D, L / φ = 2. It is -5, and the basic structure of the steel tower in any one of Claims 1-4 which satisfy | fills the conditions of D / phi = 2-10 is provided.

  As the present invention according to claim 6, there is provided the foundation structure of the steel tower according to any one of claims 1 to 5, further comprising a diagonal pile driven in a diagonally downward direction from a steel pipe peripheral wall portion of the concrete structure. .

  In this invention of the said Claim 6, it is made to equip with the slant pile put toward the diagonally downward direction from the steel pipe surrounding wall part of the said concrete structure. By providing the inclined piles, the pulling strength can be greatly improved.

As this invention which concerns on Claim 7, the foundation structure of the tower in any one of Claims 1-5 provided with the connection beam which connects the concrete structures of the said adjacent tower main pedestal pillar is provided.
In the present invention according to the seventh aspect, a connecting beam for connecting the concrete structures of adjacent main tower pillars is provided. By connecting the concrete structures with connecting beams, the displacement of the foundation can be greatly suppressed.

  As the present invention according to claim 8, there is provided the foundation structure of a steel tower according to any one of claims 1 to 5, wherein the number of the main tower pillars is 2 to 4. Instead of a large steel pipe column, it can also be used in an upper structure with 2 to 4 truss structure columns. In the case of a small-scale steel tower, all four main pedestal columns are placed in one steel pipe. It can be fixed.

  As described above in detail, according to the present invention, in the foundation structure type in which a plurality of piles having a relatively small diameter are installed in the ground, as a concrete structure, for the displacement prevention fixed to the inner wall surface along the circumferential direction. Adopting a structure created by placing concrete in a steel pipe with multiple ribs in the vertical direction, the fixing strength can be drastically improved, and the foundation part can be scaled down It becomes like this. As a result, it is possible to shorten the construction time, the excavation amount, the concrete placement amount, and the like.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First embodiment]
As shown in FIG. 1, the steel tower foundation structure according to the present invention includes a plurality of pile bodies 1, 1... Placed in the ground and a main pedestal 2 of the steel tower via a concrete structure 3. In joining, the concrete structure 3 is struck with concrete 6 in a steel pipe 5 having a plurality of vertically extending ribs 4, 4... Fixed on the inner wall surface along the circumferential direction. A top of the plurality of pile bodies 1, 1... Placed in the ground is joined to the lower side of the concrete structure 3, and the main tower pillar Are provided in a plurality of stages on the outer surface of the lower part 2, and the main pedestal column portion K on which the bearing plates 7, 7... Are disposed is embedded in the concrete structure 3. Is.

In more detail below,
As the concrete structure 3, for example, a thick steel pipe having a diameter of about 1000 to 5000 mm and a thickness of about 20 to 30 mm is preferably used. The misalignment prevention ribs 4, 4... Fixed to the inner wall surface may have any cross-sectional shape as long as it is a protrusion shape that can reliably prevent slippage with the concrete 6 to be placed. . For example, as shown in FIG. 5 (A), the rebar / steel bar 4a may be fixed by welding along the inner wall surface of the steel pipe 5, or as shown in FIG. 5 (B), a square steel material. 4b may be used, or a flat bar 4c may be used as shown in FIG.

In the illustrated example, the steel pipe 5 is a steel circular pipe, but a steel pipe such as a square pipe or a polygonal pipe may be used. In addition, the concrete structure 3 can be built in such a form that it is placed on the ground, but in order to reduce the displacement due to earth pressure resistance, the concrete structure 3 is mostly built in a state where it is buried in the ground. Is desirable.
As described above, both the pushing force and the pulling force act on the main pedestal 2 depending on the direction of wind load, etc., so that both the pushing force and the pulling force can be handled. The misalignment prevention ribs 4 are preferably arranged on the upper side and the lower side of the support main plate 2 of the tower main pedestal 2 as a boundary. Actually, it is desirable that the steel pipes 5 are arranged at almost equal intervals in the vertical direction.

  The main pedestal column 2 is provided with a plurality of steps on the outer surface of the lower part thereof, and in the example shown in the figure, the support plates 7, 7... Are provided, and the support plate disposition site K is substantially at the center of the concrete structure 3. It is embed | buried in the concrete structure 3 so that it may be located. The cross-sectional dimension of the main pedestal 2 is not particularly limited, but is approximately 300 to 3000 mm. The bearing plate 7 has a structure in which a ring plate is fixed around the main pedestal 2 by welding or the like, but the planar shape of the bearing plate 7 may be a polygonal shape or the like. In this embodiment, the pressure plate method is adopted as the fixing method of the main pedestal 2. However, the anchor material fixing method shown in FIG. 7 can also be adopted.

  Further, in the illustrated example, an example of a steel pipe column is shown as the steel tower main pedestal 2, but the main pedestal 2 can be, for example, angle steel, for example, as shown in FIG. 4. As described above, the number of the main leg pillars 2 may be two to four, and the assembly pillars 2 ′ or the like in which these are connected by a plurality of diagonal members 2a, 2a.

  The pile body 1 can be any one of steel pipe piles, cast-in-place piles, ready-made piles, etc., regardless of the pile type. It is desirable that the pile body 1 has a diameter that allows at least two or more, preferably about 4-6, to be evenly arranged in the steel pipe 5, but preferably has a diameter of 400 mm or less or a diameter of the above-described diameter from the viewpoint of workability. It is desirable to use a small-diameter pile having a diameter of 1/6 or less of the diameter of the steel pipe 5. For the construction of the small-diameter pile, for example, if a hole is drilled in the ground by drilling, a steel pipe or a ready-made pile is inserted into the hole, and a solidified material such as grout material or concrete or high-fluidity concrete is placed around the hole. It may be configured to be filled and fixed, or can be constructed as a cast-in-place pile by inserting an assembly bar into the perforation and filling concrete or high-fluidity concrete. For the drilling of the ground, a rotary type or the like is used when the ground is weak, and a rotary hitting down-the-hole hammer (trade name) or the like is suitably used when the ground is a bedrock or a bedrock layer in the middle. be able to.

  In the illustrated example, the pile body 1 and the concrete structure 3 are joined using a reinforcing bar fixing system in which fixed reinforcing bars 8, 8,... A bearing plate joining method may be employed in which fixing is performed on the outer surface of the pile head inserted into the ring 3 by a bearing plate such as a ring provided so as to protrude outward.

  The construction of the foundation structure detailed above is as follows. First, if the construction part of the concrete structure 3 is excavated, the steel pipe 5 is installed, and then the pile body 1, 1. Create 1 ... in the ground. Thereafter, the fixing bars 8, 8... Are installed, the base portion of the main pedestal 2 is positioned at a predetermined position in the steel pipe 5, and fixed by a temporary fixing member (not shown). After all the reinforcement work has been completed, concrete is placed.

[Second embodiment]
Next, the foundation structure according to the second embodiment shown in FIG. 2 is provided with a diagonal pile 10 that is driven obliquely downward from the peripheral wall portion of the steel pipe 5 of the concrete structure 3. By providing the slant pile 10 integrally with the concrete structure 3, not only the pushing force is improved, but also the pulling strength can be greatly improved. In addition, although the said example of the diagonal pile 10 was made into the example of illustration, you may make it provide multiple.
In the construction, first, if the construction part of the concrete structure 3 is excavated in the ground, the steel pipe 5 is installed after drilling from the wall surface of the excavation part and placing the slant pile 10. In the wall surface of the steel pipe 5, an insertion port 5 a for the fixing bar 11 is formed in advance for integration with the oblique pile 10.

Next, the pile bodies 1, 1... Are drilled to form the pile bodies 1, 1. After that, the fixing muscles 8, 8... Are installed, the base portion of the main pedestal 2 is positioned at a predetermined position in the steel pipe 5 and fixed by a temporary fixing member (not shown), and the predetermined portion in the steel pipe 5 is set. When reinforcing bars are placed and the fixing bars 11 are inserted from the insertion port 5a of the steel pipe 5 and all the placing work is completed, concrete is placed.
In addition, concrete is also cast on the outer portion of the insertion port 5 a of the steel pipe 5, and the head of the oblique pile 10 is fixed so as to be integrated with the concrete structure 3.

[Third embodiment]
Next, the foundation structure according to the third embodiment shown in FIG. 3 is provided with connecting beams 12 so as to connect the concrete structures 3 and 3 of the adjacent tower main pedestal columns 2. By connecting the concrete structures 3 and 3 to each other by the connecting beam 12, the displacement of the foundation can be greatly suppressed.

  First of all, if the construction part of the concrete structure 3 is excavated in the ground, if the drilling part forms a through hole for installing the connecting beam 12 by horizontal drilling from the wall surface of the excavation part, or if it is relatively shallow Forms a groove in the connecting beam installation portion by open excavation, and after forming the connecting beam 12, the steel pipe 5 is installed. An insertion port 5a for the fixing bar 11 is formed in advance on the wall surface of the steel pipe 5 so as to be integrated with the connecting beam 12 in advance.

  Next, the pile bodies 1, 1... Are drilled to form the pile bodies 1, 1. After that, the fixing muscles 8, 8... Are installed, the base portion of the main pedestal 2 is positioned at a predetermined position in the steel pipe 5 and fixed by a temporary fixing member (not shown), and the predetermined portion in the steel pipe 5 is set. When reinforcing bars are placed and the fixing bars 11 are inserted from the insertion port 5a of the steel pipe 5 and all the placing work is completed, concrete is placed.

  Further, concrete is also cast on the outer portion of the insertion port 5 a of the steel pipe 5 to fix the end of the connecting beam 12 so as to be integrated with the concrete structure 3.

[Design of fixing strength by this fixing method]
Next, a method for designing a steel tower foundation according to the present invention will be described.
This design method has a reasonable design because the ultimate strength is the fracture mode (yield strength of the steel pipe 5, the adhesion strength of the concrete around the bearing plate, the strength of the rib 4 for slippage prevention) after preventing the split fracture. Become.

(2)支圧板７周囲のコンクリート付着耐力（応力度）は、次式(2)によって決定する。

(3)前記ズレ止め用リブ４の耐力を検討するために、ズレ止め用リブ４の溶接部のせん断応力度は次式(3)にて決定する。

(4)前記ズレ止め用リブ４に接するコンクリートの支圧応力度は、次式(4)にて決定する。

(5)前記ズレ止め用リブ４の内周に接するコンクリートのせん断応力度は、次式(5)にて決定する。

The fixing strength design by this joining method can be designed based on the following formula in consideration of the following matters.
(1) The yield strength (stress) of the steel pipe 5 that restrains the concrete is determined by the following equation (1).

(2) The concrete adhesion strength (stress level) around the bearing plate 7 is determined by the following equation (2).

(3) In order to examine the proof stress of the misalignment prevention rib 4, the shear stress degree of the welded portion of the misalignment prevention rib 4 is determined by the following equation (3).

(4) The bearing stress level of the concrete in contact with the misalignment prevention rib 4 is determined by the following equation (4).

(5) The degree of shear stress of the concrete in contact with the inner periphery of the displacement preventing rib 4 is determined by the following equation (5).

The basic structure of the steel tower which concerns on a 1st form example is shown, (A) is a longitudinal cross-sectional view, (B) is a cross-sectional view. The basic structure of the steel tower which concerns on a 2nd form example is shown, (A) is a longitudinal cross-sectional view, (B) is a right view, (C) is a cross-sectional view. It is a longitudinal cross-sectional view which shows the basic structure of the steel tower which concerns on a 3rd form example. FIG. 6 is a longitudinal sectional view showing a modification of the main pedestal 2. FIG. 4 is a view showing an example of the misalignment prevention rib 4 (A) to (C). The basic structure of the conventional steel tower is shown, (A) is a longitudinal sectional view, and (B) is a transverse sectional view. The anchoring material fixing method of the main pedestal 52 is shown, (A) is a footing longitudinal section, (B) is a plan view of the anchoring material, and (C) is a side view of the anchoring material. FIG. 5A is a longitudinal sectional view and FIG. 5B is a transverse sectional view showing a pressure plate fixing method of the main pedestal 52. (A) is a figure which shows the bearing plate fixing system of the pile body 50, (B) is a figure which shows a reinforcing bar fixing system. It is a side view which shows the basic structure of the simple steel tower which concerns on a prior art example. It is an external-force action state figure by the wind load with respect to a steel tower foundation. It is a figure which shows the destruction form (the 1) of a footing. It is a figure which shows the destruction form (the 2) of a footing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pile body, 2 ... Main pedestal column, 3 ... Concrete structure, 4 * 4a-4c ... Rib for rib prevention, 5 ... Steel pipe, 6 ... Concrete, 7 ... Supporting plate, 8.11 ... Fixing reinforcement, 10 ... Diagonal piles, 12 ... connected beams

Claims (8)

In the foundation structure of a steel tower in which multiple piles placed in the ground and the main pedestal of the steel tower are joined via a concrete structure,
The concrete structure is a structure formed by placing concrete in a steel pipe having a plurality of steps in the vertical direction with a rib for fixing a slippage fixed on the inner wall surface along the circumferential direction, A top portion of a plurality of pile bodies placed in the ground is joined to the lower side of the concrete structure, and a fixing member is provided at a lower portion of the main tower pillar, and the fixing member is provided. A foundation structure of a steel tower, wherein a main pillar portion is embedded in the concrete structure.   The foundation structure of a steel tower according to claim 1, wherein the plurality of pile bodies are small-diameter piles having a diameter of 400 mm or less or a diameter of 1/6 or less of the steel pipe diameter.   The steel tower foundation structure according to any one of claims 1 and 2, wherein the misalignment prevention ribs are arranged on an upper side and a lower side, respectively, with a bearing plate arrangement portion of the main tower pillar as a boundary.   The said concrete structure is the foundation structure of the steel tower in any one of Claims 1-3 by which most is embed | buried under the ground.   When the diameter of the tower main pedestal column is φ, the section length of the bearing plate in the tower main pedestal column is L, and the inner diameter of the steel pipe is D, L / φ = 2 to 5 and D / φ The foundation structure of the steel tower in any one of Claims 1-4 which satisfy | fills the conditions of = 2-10.   The foundation structure of the steel tower in any one of Claims 1-5 provided with the diagonal pile cast toward diagonally downward from the steel pipe surrounding wall part of the said concrete structure.   The foundation structure of the steel tower in any one of Claims 1-5 provided with the connection beam which connects the concrete structures of the said adjacent steel tower main pedestal column. The foundation structure of the steel tower according to any one of claims 1 to 5, wherein the number of the main tower pillars is 2 to 4.

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