JP2008223303A - Foundation structure of tower-like structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foundation structure of a tower-like structure such as a support and a tower, which has a column base portion for being completely fixed by mean of an unbonded anchor for introducing prestress, and which suppresses the formation of a crack in concrete to the utmost. <P>SOLUTION: A horizontal reinforcement 2a and a ring reinforcement 5 are arranged in a direction crossing the longitudinal direction of the unbonded anchor 1, on the unbonded anchor 1 for introducing the prestress, which is laid between a base plate 2a and the anchor plate 2b; and a vertical reinforcement 3 is arranged in a direction parallel to the longitudinal direction. When these reinforcements are arranged for the placing of the concrete 6, the thickness of the concrete 6 in the direction crossing the longitudinal direction of the unbonded anchor 1 is set as great as possible. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a foundation structure of a tower-like structure constructed up to a high position in the sky such as a pillar, a tower, a monument, etc. constructed on the ground, and particularly relates to a foundation structure using an unbonded anchor for introducing prestress. .

  There are various tower-like structures constructed on the ground, such as various towers, monuments, and chimneys. One of them is a tower for wind turbines, which is a column of wind turbines for wind power generation. At the top of the tower, there are a plurality of propeller blades (blades) supported by a horizontal axis, and heavy objects such as a generator that generates electricity by rotating the windmill and a rotating mechanism that adjusts the direction of the windmill to the windward is set up. Moreover, in order to improve the power generation efficiency stably, it is necessary to receive a strong wind to some extent, and it is desirable to position the top at a position as high as possible. That is, in a windmill tower, it is necessary to extend a top part to a high position as much as possible, and to support a heavy article on the top part.

  In the tower-like structure, a large horizontal load is received by the wind in the sky. For this reason, a bending moment acts as a tipping moment on the foundation of the tower-like structure. In particular, in the tower for wind turbines, in addition to the load in the horizontal direction, a complicated load is applied by rotating the blades of the wind turbine, changing the direction of the wind turbine by the rotation mechanism, and the combination of these various loads. There is a risk of overturning the tower for windmills. Moreover, in Japan, since the overturning moment due to the seismic load is large, a foundation structure that can cope with earthquakes in addition to wind loads is desired.

  For example, a ground anchor combined pile method disclosed in Patent Document 1, a wind power generation tower disclosed in Patent Document 2, and Patent Document 3 disclosed as a proposal for a basic structure of a high-rise building or a tower structure. There is an anchor frame of a windmill tower.

  Further, in Non-Patent Document 4, a method for designing a columnar reinforcing bar of a rising portion (pedestal) of a footing foundation is described. Regarding the design of an anchor bolt, a connecting member joined to a bolt lower end with a nut or the like. Examine whether the stress caused by (anchoring) satisfies the concrete tolerance and the tolerance of the anchoring member itself, and whether the anchor bolt surface adheres to the concrete It is supposed to be.

  Furthermore, in Non-Patent Document 5, the design is made with a smaller allowable pulling force determined by cone-shaped fracture of the headed anchor bolt and a smaller allowable value of the anchor bolt member itself.

Japanese Patent Publication No. 5-59219 JP 2002-122066 A JP 2004-278400 A Chimney structure design and construction guidelines (Japan Architecture Center) Various structural design guidelines (Architectural Institute of Japan)

  The support structure by the pile method disclosed in Patent Document 1 is mainly a building, which counters the buoyancy generated in the building by receiving a tipping moment due to a horizontal force caused by wind, earthquake, etc. Thus, when a complicated overturning moment occurs, reliability may not be ensured. Further, in the wind power generation tower disclosed in Patent Document 2, a tower body formed by stacking hollow cylinders and a prestressed concrete reinforcing member having a T-shaped cross section along the outer periphery on the base side of the tower body. The reinforcing member is coupled and fixed to the foundation and the tower body. In addition, an anchor frame disclosed in Patent Document 3 includes a pair of upper and lower ring-shaped anchor plates, a plurality of connection members that connect the pair of upper and lower anchor plates at a predetermined interval, and the connection between the connection members. A plurality of anchor bolts and a plurality of struts connected to the lower surface of the lower anchor plate for positioning the pair of upper and lower anchor plates at a predetermined height on the foundation, the connecting member and the struts Is made of steel pipe.

  In the basic structure disclosed in Patent Document 2 and Patent Document 3, a pedestal that is a base pedestal protruding from the center of the base member is formed, and a tower is fixed to the pedestal. And anchor bolts and struts. However, since the driven concrete and the anchor bolt are bonded and joined, if the falling moment is loaded and this bond breaks, the concrete will crack and if the allowable stress of the concrete is exceeded. There is a risk of damaging the concrete. For this reason, it is desirable that the foundation has a structure that does not have adhesion between the anchor bolt and the concrete, and has a structure using an unbonded anchor that reduces the load on the concrete by changing the load transmission mechanism.

  In addition, as disclosed in Non-Patent Document 4 and Non-Patent Document 5, the conventional tower-like structure foundation structure includes anchor bolts attached to concrete with reference to the pointers and the like, and nuts or the like at the lower end thereof. The connecting member (anchor ring) to be joined together is arranged at the rising part (pedestal) of the footing foundation, and is designed on the basis of resisting the overturning moment received from the upper structure by the columnar structure.

  The support structure of a tower-like structure (tower) typified by a chimney is a structure in which a pedestal that is a base pedestal protruding from the center of the base member is formed, and the tower is fixed to this pedestal. The fixing portion is composed of the anchor bolt and the connecting member (anchor ring) in the placed concrete. In addition, it is designed on the assumption that the concrete and the anchor bolt are bonded and joined. When a falling moment is loaded, a tensile force is transmitted through the concrete to the vertical reinforcing bars arranged beside the anchor bolt.

  On the other hand, if you want to adjust the natural period of the superstructure, like a tower for wind turbines, or if you want the legs to be completely fixed or close to this, use unbonded anchors and tighten tension on the anchor bolts after placing the concrete. It can be considered that the structure is given (prestress).

  When pre-stress is applied using an unbond anchor, a tensile load acts on the concrete around the unbond anchor in the longitudinal direction below the lower anchorage (anchor ring) of the unbond anchor and the cross direction of the unbond anchor. As a result, a stress state different from that of anchor bolts expected to adhere to concrete without prestressing will occur, and if there is a shortage of reinforcing bars required when prestressing is introduced, Even under normal load, cracks occur in the concrete, and if the cracks progress, the concrete may break along the unbond anchors. In addition, when the leg portion is completely fixed by this structure, the structure that resists the overturning moment is a columnar structure that transmits the tensile force to the vertical reinforcing bars arranged beside the anchor bolt via concrete. Is different.

  Therefore, the present invention takes into consideration the foundation shape and the arrangement of reinforcing bars that do not cause harmful cracking in the concrete even when prestress is introduced using an unbonded anchor, and can sufficiently resist the overturning moment. The purpose is to provide the basic structure of the tower structure.

  As a technical means for achieving the above-mentioned object, the foundation structure of the tower-like structure according to the present invention is such that the top part extends to a high position in the sky, and the overturning moment is generated by the external force acting on the top part and the column part. In the foundation structure of the tower-like structure on which a horizontal force or the like acts, the column base portion of the tower-like structure is fixed with an unbond anchor that introduces prestress, and a horizontal reinforcing bar is crossed in a direction crossing the longitudinal direction of the unbond anchor. The concrete is driven by placing a vertical reinforcing bar in a direction parallel to the unbond anchor.

  In the state where the tower-like structure is supported by the unbonded anchor introduced with the prestress, there is no adhesion between the unbonded anchor and the concrete, so that the load is not transmitted. However, the concrete surrounded by the unbonded anchor bolt and the anchor ring at the lower end where the prestress is introduced is firmly integrated, and the concrete tries to expand in a direction crossing the unbonded anchor bolt, and the top portion The overturning moment due to the external force acting on the steel also acts as bearing stress on the concrete surrounding the integrated concrete. For this reason, a horizontal rebar is arranged in a ring shape around the penetration portion of the anchor bolt to counter the bearing stress.

  Further, the foundation structure of the tower-like structure according to the invention of claim 2 is a part of the concrete, and a portion where a bearing pressure acts in a direction intersecting the longitudinal direction of the penetration portion of the unbond anchor is the support structure. It is characterized by securing a width that can appropriately arrange a ring-shaped reinforcing bar in a direction crossing the unbond anchor with respect to the pressure.

  In order to allow the concrete itself to counter the horizontal bearing stress that the concrete receives, the thickness in the direction of the bearing stress is increased to obtain the necessary shear resistance area. In what forms a pedestal, the wall thickness along the radial direction of a tower-like structure is made sufficiently large.

  Further, in the foundation structure of the tower-like structure according to the invention of claim 3, the lower end portion of the unbond anchor is disposed at a position sufficiently deeper than the pedestal portion of the portion where the tower-like structure is erected, It is characterized by being fixed to the base part, and has a structure that makes it easy to obtain the necessary shear resistance area.

  Although the entire top surface of the concrete may be a horizontal surface that does not form a pedestal, it is a pedestal having a height sufficiently lower than the length of the anchor bolt embedded in the concrete and has a cross-sectional area required for the bearing stress. If it has thickness, it does not need to be a horizontal plane. However, it is difficult to form a completely horizontal surface, and it is possible to form a pool of rainwater on the top surface of the concrete.

  Moreover, the basic structure of the tower-like structure according to the invention of claim 4 is characterized in that the tower-like structure is a column for wind power generation.

  In particular, it is the foundation structure of a tower for wind power generation where a large load acts.

  According to the basic structure of the tower-like structure according to the present invention, even after the prestress is introduced, the horizontal reinforcing bar and the vertical reinforcing bar arranged against the unbond anchor counteract the stress acting on the concrete. Thus, cracking of the concrete is suppressed, and thereafter, even when a tipping moment is applied by an external force such as wind, it is possible to prevent breakage.

  Further, according to the basic structure of the tower-like structure according to the invention of claim 2, the unbonded anchor portion into which the prestress is introduced is firmly integrated like an embedded column base, so that the horizontal concrete support It becomes a load transmission mechanism mainly consisting of pressure, and can withstand the overturning moment, preventing breakage due to concrete tension.

  Moreover, according to the foundation structure of the tower-shaped structure which concerns on invention of Claim 3, it is set as the structure which does not form a pedestal as much as possible, the shape of a foundation can be made simple, and construction is easy. In addition, the thickness of the concrete in the direction intersecting the longitudinal direction of the unbonded anchor can be easily increased.

  In addition, according to the tower structure basic structure according to the invention of claim 4, the wind turbine tower, which is provided with a wind turbine, a generator, or the like at the top, and which has a large overturning moment due to the load received by the wind, is collapsed. This can be prevented as much as possible.

  Hereinafter, the basic structure of the tower-like structure according to the present invention will be specifically described based on the illustrated preferred embodiment.

  As shown in FIG. 1, in this foundation structure, a tower-like structure such as a tower for wind turbines is fixed to the foundation by an unbond anchor 1 into which prestress is introduced. The unbonded anchor 1 is arranged with a pre-stress introduced between the base plate 2a and the anchor plate 2b. An appropriate number of horizontal reinforcing bars 3 are arranged in a direction intersecting the longitudinal direction of the unbonded anchor 1, and vertical reinforcing bars 4 in a direction parallel to the longitudinal direction of the unbonded anchor 1 are arranged.

  For example, since the hollow cylinder is formed by stacking hollow cylinders in the wind power generation tower, the unbond anchors 1 are arranged on the arc along the hollow cylinder at appropriate intervals. Although FIG. 1 shows a structure in which one unbonded anchor 1 is arranged in the radial direction of the tower-like structure, two or more unbonded anchors 1 can be arranged in the radial direction. The vertical reinforcing bars 4 are provided with a suitable number of ring-shaped reinforcing bars 5 along a circular arc concentric with the tower-like structure.

  Then, as shown in FIG. 2, concrete 6 is driven into the unbond anchor 1 and the reinforcing bars 3, 4, and 5 assembled in the structure. FIG. 2 is a cross-sectional view of the foundation portion provided with this foundation structure, and shows the reinforcement of the main portion. This concrete 6 has a horizontal pedestal portion 6a in which the heads of the unbond anchors 1 are arranged in an arc shape in the center of the upper surface, and an inclined surface 6b is formed from the end of the pedestal portion 6a to the outer edge. Yes. The slope may be a gentle slope that allows rainwater or the like to flow smoothly, as long as a thickness necessary for design is ensured in a horizontal direction that intersects the longitudinal direction of the unbond anchor 1. As long as this thickness is secured, a pedestal-type basic shape may be used. Moreover, you may be uniformly formed in the horizontal surface.

  And the anchor ring of the lower end part of the unbonded anchor is arranged at a position sufficiently deeper than the pedestal that is the pedestal part of the part where the tower-like structure is erected, so that it reaches the base that becomes the foundation part of the concrete. It is.

  In the foundation structure of the tower-like structure constituted as described above, for example, the concrete 6 around the unbond anchor 1 into which prestress is introduced in order to fix the tower for wind turbines, the unbond anchor as shown by the broken line in FIG. A tensile load acts on the longitudinal direction of 1 and the direction intersecting the longitudinal direction. With respect to these tensile loads, the horizontal rebar 3 arranged to intersect the longitudinal direction of the unbond anchor 1 and the vertical rebar 4 parallel to the longitudinal direction of the unbond anchor 1 respectively oppose each other and act on the concrete 6. To reduce the load. Therefore, the occurrence of cracks in the concrete 6 is suppressed as much as possible, and breakage is prevented.

  Also, when the horizontal load received by wind or earthquake acts as a tipping moment, in addition to the same load as described above, it has a structure that is firmly integrated like an embedded column base, Although the load transmission mechanism is mainly composed of concrete bearing pressure in the direction, the horizontal reinforcing bar 3 and the ring reinforcing bar 5 are arranged on the surrounding concrete 6 to counter the pressure of spreading in the radial direction. The occurrence of cracks in 6 is suppressed as much as possible, and breakage is prevented.

  In the above-described embodiment, the basic structure suitable for the tower of wind power generation has been described. However, the present invention is not limited to this, and it is used as the basic structure of a tower-like structure extended to a high position in the sky such as a monument or a chimney. You can also.

  According to the basic structure of the tower-like structure according to the present invention, the mechanism in which the column base is completely fixed by using the unbonded anchor introduced with prestress and the overturning moment is transmitted to the concrete is based on the shear strength of the concrete. Since it can be changed to bearing capacity, it becomes a foundation structure suitable for towers for wind turbines where large horizontal loads repeatedly act, and can be prevented from collapsing as much as possible, thereby extending the useful life of tower structures. Contribute.

It is a figure explaining the reinforcement of the foundation structure of the tower-like structure concerning this invention. It is sectional drawing which shows schematic structure of the basic structure of the tower-shaped structure which concerns on this invention. It is a figure explaining the outline of distribution of the load which acts on the circumference of the unbond anchor which introduced prestress.

Explanation of symbols

1 Unbond anchor
2a Base plate
2b Anchor plate 3 Horizontal reinforcing bar 4 Vertical reinforcing bar 5 Ring reinforcing bar 6 Concrete
6a pedestal
6b inclined surface

Claims (4)

In the basic structure of the tower-like structure in which the top part extends to a high position in the sky, and the overturning moment, the horizontal force, etc. act by the external force acting on the top part and the column part,
Fix the column base of the tower structure with an unbond anchor that introduces prestress,
A horizontal reinforcing bar is arranged in a direction crossing the longitudinal direction of the unbond anchor,
A foundation structure of a tower-like structure, wherein vertical reinforcing bars in a direction parallel to the unbond anchors are arranged and concrete is driven.   A portion of the concrete where a bearing pressure acts in a direction intersecting with the longitudinal direction of the penetration portion of the unbonded anchor appropriately applies a ring-shaped reinforcing bar in a direction intersecting the unbonded anchor with respect to the bearing pressure. The base structure of the tower-like structure according to claim 1, wherein a width that can be arranged is secured.   The lower end portion of the unbond anchor is disposed at a position sufficiently deeper than a pedestal portion of a portion where the tower-like structure is erected, and is fixed to a concrete base portion. The basic structure of the tower structure.   The foundation structure of the tower-like structure according to any one of claims 1 to 3, wherein the tower-like structure is a column for wind power generation.

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