JP2018053618A - Structure of pile head joining part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a pile head joining part that reduces bending moment that is caused in a head of a precast concrete pile when an earthquake occurs, and that achieves a resistance function against pull-out force that is applied to an upper structure on a footing.SOLUTION: A pile head joining structure comprises a first steel cap (28) having a top part and a side part, which covers and is fixed on a head (12) of a precast concrete pile, and, a second steel cap (30) integrated with a footing (18), which covers the first cap. The second cap has a top part (36) abutting on a top part (32) of the first cap and a side part (38) defining a space (40) that allows the head of the precast concrete pile to rotate when an earthquake occurs. The inside of the side part of the second cap has a cylindrical surface (46) where the first cap comes into contact with a location (b) on a boundary between its top part and side part when horizontal displacement of the footing is within a setting range of 1 to 8 cm at the time of an earthquake.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a structure of a joint portion between a head of a ready-made concrete pile installed in the ground and a footing supported on the head of the ready-made concrete pile.

  Conventionally, as the structure of the joint between the head of the ready-made concrete pile and the footing that make up the pile foundation, one with a steel cap that is integrated with the footing on the head of the ready-made concrete pile has been proposed Has been. The cap includes a top portion and a side portion connected to the top portion, and the side portion surrounds the periphery of the head of the ready-made concrete pile and defines a truncated conical surface having a gradually increasing diameter (see Patent Document 1 described later). ).

  According to this, the space spreading toward the bottom defined by the truncated conical surface of the side portion of the cap allows rotation of the head of the ready-made concrete pile during an earthquake. This allowable rotation contributes to the reduction of the bending moment generated in the head of the ready-made concrete pile.

  By the way, the structure of the conventional joint portion lacks a means for exerting a resistance function against a pulling force applied to the upper structure on the footing. For this reason, the application object of the structure of the said conventional connection part is restrict | limited to the pile foundation which supports comparatively simple superstructure like a warehouse.

JP 58-153822 A

  The object of the present invention is to reduce the bending moment generated at the head of a ready-made concrete pile at the time of an earthquake in view of the above-described conventional situation, and to exhibit a resistance function against a pulling force applied to the superstructure on the footing. It is providing the structure of the joint part of a pile head which has a means to do.

  The present invention relates to a structure of a joint portion for a footing of a head of a cylindrical ready-made concrete pile installed in the ground and extending in the vertical direction, and the structure of the joint is covered on the head of the ready-made concrete pile and A fixed steel first cap having a top and a side continuous to the top, and a second steel cap overlying the first cap and integral with the footing; The second cap has a top portion that is in contact with the top portion of the first cap and a side portion that is connected to the top portion and defines a space that allows rotation of the head of the ready-made concrete pile during an earthquake. Here, the side portion of the second cap has a top portion and a side portion when the horizontal displacement of the footing during an earthquake is within a set range of 1 to 8 cm. It has a cylindrical surface that contacts at one point on the boundary.

  According to the present invention, the space defined by the side of the second cap that covers the first cap that covers the head of the ready-made concrete pile allows the head of the ready-made concrete pile to rotate during an earthquake. In particular, when the horizontal displacement of the footing during an earthquake is 1 cm or more, the allowable rotation of the head of the ready-made concrete pile contributes to the reduction of the bending moment generated at the top of the ready-made concrete pile. Further, in the present invention, when the side portion of the second cap is inside thereof, the horizontal displacement of the footing during an earthquake is within a set range of 1 to 8 cm. It has a cylindrical surface that contacts at one point on the boundary between the top and the side. According to this, a frictional force is generated between the first cap and the second cap with the contact. The frictional force provides resistance to pulling applied to the superstructure supported on the footing.

  A belt-like frictional force adjusting member surrounding the periphery of the side portion at and near the boundary between the top portion and the side portion of the first cap can be attached to the side portion of the first cap. The frictional force adjusting member includes, for example, a laminate of a plurality of fiber sheets (preferably a laminate of a plurality of carbon fiber sheets), a laminate of a plurality of resin sheets, or a rubber sheet. According to this, the contact of the first cap with the cylindrical surface of the second cap is made via the frictional force adjusting member. For this reason, the said frictional force produced with the said contact can be adjusted to a desired magnitude | size.

  The side portion of the second cap is composed of an upper portion that defines the cylindrical surface and a lower portion that is continuous with the cylindrical surface and defines a truncated conical surface whose diameter gradually increases downward, or the cylinder. An upper part that defines a surface and a lower part that defines a cylindrical surface having a diameter larger than that of the cylindrical surface, which are continuous with the cylindrical surface.

It is sectional drawing of the structure of the junction part of the pile head which concerns on one Embodiment of this invention. It is sectional drawing of the structure of the junction part of the pile head shown in FIG. 1 at the time of the occurrence of a comparatively small scale earthquake. It is sectional drawing of the structure of the junction part of the pile head shown in FIG. 1 at the time of the occurrence of a comparatively large earthquake.

  Referring to FIG. 1, a structure of a joint portion of a pile head according to an embodiment of the present invention, that is, a structure of a joint portion of a head 12 of a ready-made concrete pile 10 is indicated by a reference numeral 14 as a whole.

  The ready-made concrete pile 10 is installed in the ground 16 (underground) and extends in the vertical direction (vertical direction). The ready-made concrete pile 10 constitutes a pile foundation 20 together with a reinforced concrete footing 18 supported by the ready-made concrete pile. The pile foundation 20 supports an upper structure (not shown) such as a building constructed on the footing 18 on the ground 16. Reference numeral 21 denotes a reinforcing steel bar extending in the concrete of the footing 18. These reinforcing reinforcing bars 21 are fixed to a top portion 36 of a second cap 30 described later and extend upward from the top portion.

  The ready-made concrete pile 10 is composed of a centrifugally formed concrete pile with a shell steel pipe (SC pile), a high-strength prestressed concrete pile (PHC), a high-strength prestressed reinforced concrete pile (PRC), and the like, and has a cylindrical shape as a whole.

  The ready-made concrete pile 10 is installed in the ground by, for example, inserting the ready-made concrete pile 10 into a hole 24 formed by excavating the ground 16 while filling cement milk formed by stirring cement and water. Is called. The ready-made concrete pile 10 thrown into the hole 24 is filled with the cement milk in the hollow portion 26 and the surrounding space. The cement milk hardens with time to become a soil cement 22, and the ready-made concrete pile 10 and the ground 16 are united by the soil cement 22. In the illustrated example, the head 12 of the ready-made concrete pile 10 is exposed to the space above the ground 16 by root cutting with respect to the ground 16 applied after the cement milk is hardened. In addition, the inside of the head 12 which makes a part of the hollow part 26 of the ready-made concrete pile 10 can be filled with concrete (not shown) instead of filling it with the illustrated soil cement 22.

  The pile head joint structure 14 includes a steel first cap 28 that covers the head 12 of the ready-made concrete pile 10 and a steel that is integral with the footing 18 that covers the first cap. Second cap 30.

  The first cap 28 has a top portion 32 having a circular planar shape, and a cylindrical side portion 34 that is connected to the top portion and surrounds the periphery of the head 12 of the ready-made concrete pile 10. The first cap 28 is fixed to the ready-made concrete pile 10 via fixing means (not shown) such as a plurality of bolts that extend into the head 12 of the ready-made concrete pile 10 through the top portion 32.

  On the other hand, the second cap 30 is embedded in the footing 18. The second cap 30 embedded in the footing 18 is opened toward the ground 16 and is in contact with the ground 16.

  The second cap 30 has a top portion 36 having a circular planar shape and a side portion 38 connected to the top portion. The top 36 of the second cap 30 is on and in contact with the top 32 of the first cap 28, and the side 38 of the second cap 30 provides a space 40 around the side 34 of the first cap 28. Stipulate. The space 40 is a rotation of the head 12 of the ready-made concrete pile 10 during an earthquake, more specifically, a rotation of the head 12 that occurs when an earthquake force (horizontal external force) acts on the upper structure on the footing 18 (FIG. 2). And FIG. 3). The rotation occurs around a point a on the boundary between the top 32 and the side 34 of the first cap 28, which contacts the top 36 of the second cap 30. The ready-made concrete pile 10 supports the superstructure at one location a in the first cap 28 during the rotation.

  The side portion 38 of the second cap 30 that defines the space 40 includes an upper portion 42 that continues to the top portion 36 and a lower portion 44 that continues to the upper portion. Upper portion 42 defines a cylindrical surface 46 therein. The lower portion 44 defines a frustoconical surface 48 which is continuous with the cylindrical surface 46 and gradually increases in diameter downward. Instead of the frustoconical surface 48 shown in the figure, a large cylindrical surface (not shown) connected to the cylindrical surface 46 and having a larger diameter than the cylindrical surface can be used.

  In the illustrated example, a gap forming a part of the space 40 exists between the side portion 34 of the first cap 28 and the upper portion 42 (cylindrical surface 46) of the second cap 30, and the gap is filled. The side portion 34 of the first cap 28 is in close contact with the upper portion 42 of the second cap 30 through the frictional force adjusting member 50. The frictional force adjusting member 50 has a band shape, and is attached to the side portion 34 of the first cap 28, and the side portion 34 of the first cap 28 at and near the boundary between the top portion 32 and the side portion 34 of the first cap 28. Surrounding around. The frictional force adjusting member 50 includes, for example, a laminate of a plurality of fiber sheets (preferably a laminate of a plurality of carbon fiber sheets), a laminate of a plurality of resin sheets, a rubber sheet, and the like, and has a relatively large thickness. Have dimensions.

  The first cap 28 rotates in the head 12 of the ready-made concrete pile 10 when the footing 18 and thus the superstructure on the footing 18 is displaced in the horizontal direction due to an earthquake. By the way, when the horizontal displacement of the upper structure is less than 1 cm, the pulling force does not substantially act on the upper structure. Considering this, in the present invention, when the horizontal displacement of the superstructure is within a set range of 1 to 8 cm, that is, in the case of a relatively small earthquake, the pulling force acting on the superstructure is applied. Make it possible to compete.

  When the rotation occurs in the head portion 12 of the ready-made concrete pile 10, the first cap 28 has a second portion b on the boundary between the top portion 32 and the side portion 34 via the friction force adjusting member 50. It contacts the cylindrical surface 46 of the upper portion 42 of the second cap 30 (FIG. 2). At the time of contact, the frictional force adjusting member 50 is compressed in the other part b of the first cap 28, and the thickness dimension thereof is reduced. Further, the frictional force adjusting member 50 is placed in a state of being in contact with the cylindrical surface 46 of the second cap 30 without being compressed in other portions other than the other one location b.

  However, when the horizontal displacement of the superstructure is less than 1 cm, the amount of rotation of the head 12 of the ready-made concrete pile 10 is extremely small. At this time, since the compression amount of the frictional force adjusting member 50 is extremely small, the head portion 12 of the ready-made concrete pile 10 is substantially the second cap via the first cap 28 and the frictional force adjusting member 50. It can be considered that the first part 42 of 30 is rigidly joined. For this reason, the very small rotational energy of the head 12 of the ready-made concrete pile 10 is absorbed by the rigid joint.

  Next, when the horizontal displacement of the superstructure is within a setting range of 1 to 8 cm, the contact of the head 12 of the ready-made concrete pile 10 during the rotation, that is, the contact at the other location b is the first cap. A frictional force is generated between 28 and the second cap 30. The vertical length or height dimension of the cylindrical surface 46 is determined so that the contact occurs within this range. In the illustrated example, the frictional force adjusting member 50 exerts a frictional force between the first cap 28 and the second cap 30 not only at one other location b but also at other portions other than the one location b. Cause it to occur. The frictional force provides resistance to pulling applied to the superstructure on the footing 18. The frictional force can be set to a desired magnitude by selecting the frictional force adjusting member 50.

  Further, when the horizontal displacement of the superstructure exceeds the set range, that is, in the case of a relatively large earthquake, one place in the first cap 28 is accompanied with the rotation of the head 12 of the ready-made concrete pile 10. b moves through the upper portion 42 of the second cap 30 and into the lower portion 44. Accordingly, the one point b reaches the non-contact state in the lower portion 44 of the second cap 30 through the contact with the cylindrical surface 46 in the upper portion 42 of the second cap 30. The allowable rotation of the head 12 of the ready-made concrete pile 10 at the time of an earthquake is relatively large when the horizontal displacement of the superstructure is within a set range of 1 to 8 cm and exceeds the set range. In any case of a large-scale earthquake, it contributes to the reduction of the rotational moment generated in the head 12 of the ready-made concrete pile 10.

  It can replace with the example of illustration and can be set as the other example which abbreviate | omitted arrangement | positioning of the frictional force adjustment member 50 (not shown). In this other example in which the frictional force adjusting member 50 does not exist, the gap exists between the side 34 of the first cap 28 and the cylindrical surface 46 in the upper portion 42 of the second cap 30. . When the horizontal displacement of the superstructure exceeds 1 cm, this gap is such that one portion b of the first cap 28 directly contacts the cylindrical surface 46 in the second cap 30, and the first cap 28 It can be set to a size that generates a frictional force with the second cap 30. Also, in this example where the gap exists, the rigid joint to the head 12 of the ready-made concrete pile 10 is not provided. For this reason, when the horizontal displacement of the superstructure is less than 1 cm, the head 12 of the ready-made concrete 10 is simply allowed to rotate.

  In the other example, the size of the gap existing between the side portion 34 of the first cap 28 and the circumferential surface 46 of the second cap 30 can be set to zero. According to this, at the time of the rotation of the head 12 of the ready-made concrete pile 10, a portion b of the first cap 28 hits the cylindrical surface 46 of the second cap 30 and plastically deformed, and the plastic deformed state In contact with the cylindrical surface 46. This contact produces a frictional force similar to that described above, which opposes the pulling force of the superstructure, especially when the horizontal displacement of the superstructure is within a set range of 1-8 cm. However, when the horizontal displacement of the superstructure is less than 1 cm, the head 12 of the ready-made concrete pile 10 that rotates at a very small angle is placed in a substantially rigid connection state as described above, and ready-made concrete. The very small rotational energy of the head 12 of the pile 10 is absorbed by the rigid joint.

DESCRIPTION OF SYMBOLS 10 Ready-made concrete pile 12 Head 14 Pile head connection structure 16 Ground 18 Footing 20 Pile foundation 28 First cap 30 Second cap 32, 34 Top and side portions 36, 38 of the first cap Cap top and side 40 Spaces 42 and 44 defined by the side of the second cap First and second portions 46 Cylindrical surface 48 Frustum cone surface 50 Friction force adjusting members a and b First cap One place on the top and side borders and one other place

Claims (5)

The structure of the joint to the footing of the head of a cylindrical ready-made concrete pile installed in the ground and extending vertically,
A first cap made of steel having a top part and a side part connected to the top part, which is placed on and fixed to the head part of the ready-made concrete pile;
A steel-made second cap that covers the first cap and that is integral with the footing, the top contacting the top of the first cap, and the head of the ready-made concrete pile in the event of an earthquake connected to the top A second cap having a side defining a space allowing rotation of the part;
The side of the second cap is located on the boundary between the top and the side when the horizontal displacement of the footing during an earthquake is within a set range of 1 to 8 cm. A joint structure having a cylindrical surface that contacts at one location.   The side portion of the second cap includes an upper portion that defines the cylindrical surface and a lower portion that defines a truncated conical surface that is continuous with the cylindrical surface and gradually increases in diameter toward the lower side. The joint structure.   The side part of the said 2nd cap consists of the upper part which prescribes | regulates the said cylindrical surface, and the lower part which prescribes | regulates the cylindrical surface larger diameter than the said cylindrical surface connected to the said cylindrical surface. Structure.   And a belt-like frictional force adjusting member attached to the side of the first cap and surrounding the periphery of the side of the first cap at and near the boundary between the top and side of the first cap. The structure of the junction part of any one of Claims 1-3.   The said frictional force adjustment member is a structure of the junction part of Claim 4 which consists of a laminated body of a some fiber sheet, a laminated body of a some resin sheet, or a rubber sheet.

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