JP2009293349A - Joint structure between pile and foundation, construction method thereof, and joint method of pile to foundation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint structure between a foundation of a structure and a pile head, capable of attaining both improvement in rigidity and strength to compression axial force and reduction in bending rigidity to bending moment, a construction method thereof, and a joint method between the pile and the foundation. <P>SOLUTION: The joint structure comprises: a connecting part 30 which is smaller in planar shape than a concrete pile 10 and connects the center of the upper surface of the concrete pile 10 to a footing 20; and plates 40 laminated to be vertically separable, the plate surrounding the circumference of the connecting part 30 and being closely interposed between the concrete pile 10 and the footing 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a joint structure between a foundation and a pile in a structure such as a building, and more particularly to a technique capable of improving rigidity and strength against a compression axial force and reducing bending rigidity.

Conventionally, a rigid joint structure in which a foundation (footing or pile cap) and a pile in a structure such as a building are completely fixed has been the mainstream. However, when a large horizontal force or rotational force is generated in the structure due to an earthquake or the like, in the rigid joint structure, the bending moment tends to concentrate on the joint portion between the pile and the foundation and is easily damaged. For this reason, as a seismic design, it is necessary to increase the amount of bar arrangement to the piles and foundations around the joints and the concrete, and this has contributed to an increase in cost in terms of design and construction.
On the other hand, recently, a joining structure that reduces the concentration of bending moment has been proposed (for example, Patent Document 1).

Patent Document 1 discloses a joint structure in which a pile and a foundation are connected by a column steel frame, a steel concrete column, or a steel reinforced concrete column having a smaller planar shape than the pile, with a gap between the top surface and the bottom surface of the pile. ing. According to such a joint structure, the rigidity against the bending moment is reduced by securing the rigidity and strength against the compression axial force transmitted from the foundation to the pile with the column steel, etc., while making the planar shape of the column steel smaller than the pile. Can be made.
JP 2000-144904 A

  However, in the joint structure between the foundation and the pile described in Patent Document 1, the concentration of the bending moment generated in the joint structure is reduced as the planar shape of the joint portion between the foundation and the pile is reduced. Since it is necessary to sufficiently transmit the compression axial force to the pile, there is a limit in reducing the planar shape of the joint portion.

  The present invention has been made in view of the above points, and has a simple structure and is a foundation of a structure capable of achieving both improvement in rigidity and strength against compression axial force and reduction in bending rigidity against bending moment. The purpose of the present invention is to provide a joint structure between a pile and a pile head, its construction method, and a joint method between a pile and a foundation.

In order to achieve the above object, the present invention is a joint structure between a pile and a foundation provided thereon,
A plane shape smaller than the pile, and a connecting portion that connects the center of the upper surface of the pile and the foundation,
It is made of a material having a higher compressive strength than the pile or the foundation, and surrounds the periphery of the connecting portion, and is interposed between the pile and the foundation, and is stacked so as to be separated from each other in the vertical direction. And a plurality of plates.
According to the joint structure of the present invention, the compression axial force acting between the foundation and the pile can be sufficiently transmitted through both the connecting portion and the plate during normal times.

  Here, since the plate surrounds the periphery of the connecting portion, the plate restrains the expansion in the horizontal direction that occurs in the connecting portion when a compression axial force acts on the connecting portion from the periphery. Strength and toughness are improved.

  Further, when a bending moment is generated in the joint structure of the present invention, the bending rigidity can be effectively reduced by separating the plates on the side where the tensile stress is generated by the bending moment.

  In addition, when the plates are separated from each other, the compressive stress is locally concentrated at the portion where the opposite plates are in contact with each other, but the bottom plate and the upper surface of the pile are in contact with each other. Therefore, the concentrated compressive stress is distributed over the entire bottom surface of the lowermost plate and transmitted to the top surface of the pile, so that damage to the head of the pile due to the stress concentration can be suppressed.

  Therefore, according to the joint structure of the present invention, the pile firmly supports the foundation during normal times, and damage to the head of the pile due to concentration of bending moment can be suppressed during an earthquake.

  Moreover, in this invention, the said plate is a plate required for the compressive axial force which acts between a pile and a foundation from the point of an allowable stress degree design by consisting of a material with a compressive strength larger than the said pile or the said foundation. Since the planar shape can be set smaller than the rigid joint structure, the rigidity against the bending moment can be further reduced.

  In the present invention, the plate may be made of steel or precast concrete.

  In the present invention, the plate may include a main body member surrounding the connection portion and a restraining member provided around the main body member so as to restrain the main body member. The plate having this configuration is, for example, a composite member in which a main body member is made of concrete having a compressive strength equivalent to that of a pile or a foundation, and a steel pipe that restrains the concrete as a restraining member is provided around the concrete.

  By configuring the plate in this way, the compressive strength and toughness of the plate against a compressive load acting in the vertical direction can be improved as compared with the case of a single concrete configuration.

  In the present invention, at least one of the plurality of plates may have a planar shape smaller than the pile. According to this structure, the bending rigidity with respect to a bending moment can be reduced much more effectively.

  Moreover, in this invention, it is good also as a plate upper one among the several plates above a lowermost plate having a planar shape smaller than the said lowermost plate. According to this configuration, at the time of an earthquake, bending rigidity is reduced in a plate (hereinafter referred to as a second plate) that is one plane higher than the lowermost plate, which has a smaller planar shape than the lowermost plate. The compressive axial force transmitted from the foundation to the pile is not transmitted directly from the second stage plate to the top surface of the pile, but is distributed and transmitted over a wide range from the bottom plate having a larger planar shape than the second stage plate. As a result, damage to the head of the pile can be suppressed.

  In the present invention, the number of stacked plates is three, and the planar shape of the intermediate plate located in the middle of the three stacked plates is the plane of the upper and lower plates of the intermediate plate. It may be smaller than the shape.

  Further, in the present invention, the plate having a planar shape smaller than the pile is a lowermost plate among the stacked plates, and a contact portion of the upper surface of the pile with the lowermost plate is the plate. It is good also as being depressed rather than the peripheral part of the upper end surface of a pile. According to this configuration, the compression axial force transmitted from the abutting portion to the head of the pile acts on the inside of the pile as compared to when the abutting portion is not depressed, and thus resists the compression axial force. Since the concrete cross section spreads and the compression axial force is dispersed and transmitted from the inside of the pile, damage to the head of the pile can be suppressed.

  In addition, when the pile is a concrete pile, a ring-shaped or spiral shear reinforcement bar is usually arranged around the main bar, and the concrete inside the pile is constrained from the surrounding area, so that the strength and deformation of the concrete can be reduced. Since the performance is improved, the fracture due to the splitting of the concrete pile is suppressed. According to this configuration, the compression shaft transmitted to the depressed portion is compared with the case where the contact portion of the upper surface of the pile is not depressed. Since the restraining force of the shear reinforcement bars placed around the upper side of the depression is added to the force, the restraining effect of the shear reinforcement bars can be applied more effectively, and the concrete pile Contributes to the suppression of split fracture.

  In the present invention, the depressed portion of the upper surface of the pile may have a tapered shape that decreases from the upper end surface of the pile toward the contact portion. According to this structure, the damage to the concrete of the head of a pile by the deformation | transformation of a plate produced when a compression axial force acts on the lowermost plate can be suppressed.

  Moreover, in this invention, it is good also as providing the shearing transmission member which penetrates the inside of the said connection part between the said pile and the said foundation, and transmits a shear force between the said pile and the said foundation. According to this structure, the shearing force produced between a pile and a foundation can be transmitted effectively. Even if a bending moment is generated in the joint structure, the shear transmission member is arranged through the inside of the connecting portion, so that the rigidity against the bending moment is difficult to increase.

  In the present invention, the shear transmission member may not be attached to at least one of the pile or the foundation. According to this configuration, since no tensile force is generated in the shear transmission member, damage to the surrounding concrete can be suppressed.

  In the present invention, the shear transmission member may be capable of transmitting a tensile force between the pile and the foundation by being fixed to the pile and the foundation. According to this structure, the tensile force produced between a pile and a foundation can be transmitted effectively.

  In the present invention, the shear transmission member may not be attached to the pile in the head region of the pile, and may be fixed to the pile at a position below the head region of the pile.

  For example, if a tensile force is generated between the pile and the foundation when the shear transmission member is attached to the pile in the head region of the pile, the tensile stress tends to concentrate on the pile head. Although the head may be damaged, according to this configuration, since the shear transmission member is not attached to the pile in the head region of the pile, the tensile force is applied to the pile from a position below the head region of the pile. It can be transmitted to the inside, whereby the tensile stress is dispersed and transmitted in a wide range inside the pile, so that damage to the head of the pile can be suppressed.

  Even when a bending moment occurs, the bending moment tends to increase as it approaches the upper end of the pile, whereas the tensile axial force acting on the shear transmission member due to the bending moment spreads widely from the inside of the pile. Since it will be distributed and transmitted, the damage to the concrete of the head of a pile can be controlled.

  Moreover, in this invention, it is good also as providing the restraint member which restrains the concrete of the head of the said pile around the head of the said pile. According to this configuration, by restraining the head of the pile, the strength and deformation performance of the concrete of the head of the pile are improved, so that it is possible to suppress breakage due to splitting of the head of the pile.

  The present invention also relates to a method for constructing a joint structure between a pile and a foundation provided thereon, and constructs a concrete pile having a plurality of plates having an annular shape stacked in a vertical direction so as to be separated from each other at the upper end. The pile construction process to be performed, and the formwork for building the foundation are installed on the upper side of the pile so that the space in the formwork and the space in the ring of the stacked plates communicate with each other, and A concrete placing step of placing concrete in the mold and in the ring of the stacked plates.

  Moreover, this invention is a joining method of a pile and the foundation provided on it, Comprising: Between the center of the upper surface of the said pile, and the said foundation, it connects with the connection part which has a planar shape smaller than the said pile. A plurality of plates that are stacked so as to be vertically separated from each other are interposed between the pile and the foundation while surrounding the periphery of the connecting portion.

  According to the present invention, with a simple configuration, a joint structure between a foundation of a structure and a pile head capable of achieving both improvement in rigidity and strength against compression axial force and reduction in bending rigidity against bending moment, and A construction method and a method for joining a pile and a foundation can be provided.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
This embodiment demonstrates the case where this invention is applied to the junction structure of a concrete pile and the footing provided on it, for example.

  1A and 1B show a bonding structure 1 according to a first embodiment, where FIG. 1A is a cross-sectional view, and FIG. 1B is a cross-sectional view taken along line AA of FIG.

  As shown in FIG. 1A, a concrete pile 10 that supports a footing 20 of a structure such as a building has a plurality of main bars 12 extending in the vertical direction near the outer periphery of the concrete pile 10 and surrounds the main bars 12. A ring-shaped or spiral-shaped shear reinforcement bar 14 is arranged.

  The joint structure 1 of the present embodiment is constructed between the concrete pile 10 and the footing 20 provided on the concrete pile 10, and a connecting portion 30 that connects the concrete pile 10 and the footing 20; And a plate 40 provided around the connecting portion 30.

  The connecting part 30 is a part that connects the center of the upper surface of the concrete pile 10 and the footing 20, which has a smaller planar shape than the concrete pile 10, and is constructed together with the concrete pile 10 or the footing 20, for example. It is concrete. Note that reinforcing bars extending in the vertical direction (hereinafter referred to as dowel reinforcing bars 50) may be arranged in the connecting portion 30 so as to straddle between the concrete pile 10 and the footing 20. The dowel reinforcing bar 50 mainly functions to transmit a shearing force from the footing 20 to the concrete pile 10. As the dowel reinforcing bar 50, for example, round steel can be used. The dowel reinforcement 50 is installed so that adhesion does not arise between the concrete (at least one of the concrete pile 10 and the footing 20) to be built.

  In addition, as a member installed in the inside of the connection part 30 here, as long as shear force is fully transmitted from the footing 20 to the concrete pile 10, it will not be restricted to the dowel reinforcement 50, but what kind of member is used. Good (for example, steel frame). Further, when the shearing force can be sufficiently transmitted by the frictional force between the plate 40, the concrete pile 10 and the footing 20, and the resistance against the shearing force of the connecting part 30, the inside of the connecting part 30 is particularly good. It is not necessary to provide a member for transmitting a shearing force such as the dowel rebar 50.

  The plate 40 is, for example, a steel plate having an annular shape (see FIG. 1B). The material of the plate 40 is not limited to steel, and any material may be used as long as the material has a higher compressive strength than the concrete constituting the concrete pile 10 or the footing 20. For example, precast concrete may be used.

  In the joint structure 1 of the present embodiment, a disk-shaped plate 40 having an opening at the center surrounds the periphery of the connecting portion 30 and is laminated so that no gap is generated between the concrete pile 10 and the footing 20. It is inserted in the state that was made. Note that the two plates 40 are merely installed in an overlapping manner and can be separated from each other. The plate 40 is installed so that there is no gap between the inner periphery of the opening of the plate 40 and the outer periphery of the connecting portion 30. Each plate 40 may be provided with an anchor bolt or the like for fixing to the concrete pile 10 or the concrete of the footing 20.

FIG. 2 is a process diagram showing a method for constructing the joint structure 1 according to the first embodiment.
As shown in FIG. 2, the construction method of the joint structure 1 includes a concrete pile construction step S <b> 10, a footing form installation step S <b> 20, and a concrete placing step S <b> 30 on the footing 20 and the connecting portion 30.

  In the concrete pile construction process S10, for example, the hole 16 is formed by excavating the ground, the reinforcing liquid such as the main reinforcement 12 and the shear reinforcement 14 is built by filling the hole with the stabilizing liquid, and the lower end of the excavated hole 16 is formed. The concrete pile 10 is constructed by inserting the tremely pipe 18 and pulling it out while placing the concrete, and the plate 40 is installed at the upper end of the concrete pile 10.

  Here, the plate 40 is placed in advance so as to cover the hole before placing the concrete in the hole 16, and the tremy tube 18 is inserted into the hole while being inserted into the ring of the plate 40, The concrete is placed at the upper end of the concrete pile 10 by placing it in the entire hole. The plate 40 is not limited to this, and concrete may be placed in the whole hole first, and then placed on the upper surface of the concrete before the concrete is cured.

  Further, the plate 40 may be installed in a state of being laminated in advance, or the lower first plate 40a is installed on the upper end of the concrete pile 10 to harden the concrete of the concrete pile 10, and then the second plate 40b may be placed on the first plate 40a.

  In addition, the dowel reinforcing bar 50 is inserted into the ring head of the plate 40 by inserting a part of the lower end of the plate 40 before the concrete is hardened after placing the concrete of the pile, and the upper part of the plate 40 is Install so that it protrudes upward from the ring.

  In the footing formwork installation step S <b> 20, a formwork 22 for constructing the concrete footing 20 is installed on the upper side of the concrete pile 10. At this time, the interior of the mold 22 and the space in the ring of the plate 40 are in communication with each other.

  Finally, in the concrete placing step S30 on the footing 20 and the connecting portion 30, concrete is placed on the inside of the mold 22 of the footing 20 and the ring of the stacked plates 40, and the concrete is cured and hardened. The joining structure 1 according to the first embodiment is constructed by demolding.

  3A and 3B are cross-sectional views for explaining the behavior of the joint structure 1 of the first embodiment. FIG. 3A shows a normal time and FIG. 3B shows an earthquake.

  As shown in FIG. 3A, in a normal state, a load transmitted from a structure such as a building through the footing 20 acts on the joint structure 1 as a compression axial force. In this case, the laminated plate 40 is interposed between the concrete pile 10 and the footing 20 without a gap, so that the compression axial force acts on both the connecting portion 30 and the laminated plate 40. For this reason, the load transmitted via the footing 20 can be sufficiently transmitted to the concrete pile 10.

  Further, here, since the plate 40 restrains the expansion in the horizontal direction generated in the connecting portion 30 when the compression axial force acts on the connecting portion 30 from the periphery, the compressive strength of the connecting portion 30 is effectively improved.

  On the other hand, as shown in FIG. 3B, in the event of an earthquake, not only a horizontal force acts on the structure, but also a falling moment that the structure swings may act. A bending moment is generated in the joint structure 1 between the pile 10 and the footing 20. In this case, in the joint structure 1, the plates on the side where the tensile stress is generated (the left side in the figure) are separated by a bending moment, and the bending rigidity acting on the joint structure 1 is effectively reduced.

  Further, at this time, although compressive stress is locally concentrated at the contact portion between the plates on the opposite side (right side in the figure) where tensile stress occurs, the upper surfaces of the first plate 40a and the concrete pile 10 are Since it is in the contact state, the concentrated compressive stress is distributed over the entire bottom surface of the first plate 40 a and is transmitted to the concrete on the top surface of the concrete pile 10. For this reason, it can suppress that a breakage arises in the upper surface of the concrete pile 10. FIG.

  Moreover, since it is installed so that adhesion may not arise between the concrete (at least one of the concrete pile 10 and the footing 20) in which the dowel rebar 50 is built, of the connection part 30 which the tensile stress by a bending moment generate | occur | produces. Even if it acts on the inside, tensile stress is not transmitted to the concrete pile 10 and the footing 20 through the dowel reinforcing bar 50, so that damage to the concrete around the dowel reinforcing bar 50 can be suppressed.

  Even if a bending moment is generated in the joint structure, the shear transmission member is arranged through the inside of the connecting portion, so that the rigidity against the bending moment is difficult to increase.

  Further, the horizontal force generated in the structure at the time of the earthquake is effectively transmitted from the footing 20 to the concrete pile 10 through the dowel reinforcing bar 50 arranged inside the connecting portion 30.

FIG. 4 is a cross-sectional view of the joint structure 2 according to the second embodiment.
As shown in FIG. 4, in the joining structure 2 of the second embodiment, the planar shape of the second plate 40b of the joining structure 1 of the first embodiment is smaller than that of the first plate 40a.

  Also in the joint structure 2 of the present embodiment, when the bending moment acts on the structure, the first plate 40a and the second plate 40b are separated from each other as in the joint structure 1 of the first embodiment. As a result, the bending rigidity with respect to the bending moment is reduced, and even if a local concentration of compressive stress occurs between the plates 40 at this time, the first plate 40a is in contact with the upper surface of the concrete pile 10, so that The compressive stress is dispersed and transmitted to the concrete pile 10.

  On the other hand, in the joint structure 2 of the present embodiment, the planar shape of the joint structure between the concrete pile 10 and the footing 20 is reduced in the second plate 40b, so that the bending rigidity with respect to the bending moment is reduced as compared with the joint structure 1. Can be made. Even if the axial rigidity is small in the second plate 40b, the compressive axial force can be sufficiently transmitted because the compressive strength is high.

  When the normal compression axial force is applied, the planar shape of the second plate 40b is smaller than that of the first plate 40a. Therefore, the contact portion between these plates has a compressive stress compared to the joint structure 1 of the first embodiment. However, since the compressive axial force is distributed and transmitted from the first plate 40a having a larger planar shape than the second plate 40b to the upper surface of the concrete pile 10, the load on the pile head is reduced. .

FIG. 5 is a cross-sectional view of the joint structure 3 according to the third embodiment.
As shown in FIG. 5, in the joint structure 3 of the third embodiment, a third plate 40c is further laminated on the second plate 40b described in the joint structure 2 of the second embodiment, and the third plate The plate 40 c is embedded in the footing 20. Here, the third plate 40c is also made of a material having a higher compressive strength than the concrete constituting the concrete pile 10 or the footing 20 as in the first plate 40a and the second plate 40b.

  Also in the joint structure 3 of the present embodiment, when a bending moment acts on the structure, the second plate 40b and the first plate 40a or the third plate 40c are separated from each other, so that the second implementation is performed. The effect of suppressing bending rigidity reduction and damage to a pile head is acquired similarly to the joining structure 2 of a form.

  Moreover, since the 3rd plate 40c is laminated | stacked on the 2nd plate 40b, and is embedded in the footing 20, the load which acts between the footing 20 and the 3rd plate 40c at the time of a normal time or an earthquake, Since the entire contact surface between the footing 20 and the third plate 40c is dispersed and transmitted, damage to the concrete constituting the footing 20 can be suppressed.

FIG. 6 is a cross-sectional view of the joint structure 4 according to the fourth embodiment.
As shown in FIG. 6, in the joint structure 4 of the fourth embodiment, two plates 40 are used, and the planar shape of the lower first plate 40a is made smaller than the planar shape of the concrete pile 10, and the upper side The second plate 40 b is embedded in the footing 20.

  Similarly to the bonding structure 2 of the second embodiment or the bonding structure 3 of the third embodiment, the bonding structure 4 of the present embodiment is also generated in the bonding structure by reducing the planar shape of the first plate 40a. The bending rigidity with respect to the bending moment to be reduced can be reduced.

  However, in the joint structure 4 of this embodiment, since the planar shape of the first plate 40a is small, the compression transmitted from the first plate 40a to the upper surface of the concrete pile 10 when a compression axial force is generated in the joint structure 4 There is a risk of increasing the stress and causing damage to the pile head.

  Therefore, in the joint structure 4 of the present embodiment, the contact portion 10a of the upper surface of the pile with the first plate 40a is formed so as to be recessed from the peripheral edge portion of the upper end surface of the pile. Thereby, the compressive axial force transmitted from the abutting portion 10a to the pile head acts on the inside of the pile as compared with the case where the abutting portion 10a is not depressed, and thus the concrete cross-sectional shape resists the compressive axial force. Is spread and dispersed and transmitted from the inside of the pile over a wide range, so that damage to the pile head can be suppressed.

  In addition, the concrete pile 10 is provided with shear reinforcement bars 14, and the concrete inside the pile is restrained from the surroundings, so that the strength and deformation performance of the concrete at the time of compressive axial force action are improved. Although it is the structure which can suppress the fracture | rupture by 10 splitting, Furthermore, in the joining structure 4 of this embodiment, when the contact part 10a of the pile upper surface is depressed, the compressive force transmitted to the said depressed part On the other hand, since the restraining force of the shear reinforcing bars 14 arranged around the upper side of the depressed portion is added, the restraining effect of the shear reinforcing bars 14 can be more effectively applied, and further the concrete. This contributes to suppression of breakage due to splitting of the pile 10.

  Moreover, in the junction structure 4, the taper 10b is formed so that the depression part of the upper surface of the concrete pile 10 may reduce toward the contact part 10a from the upper end surface of the concrete pile 10. FIG. Thereby, the damage to the concrete of the pile head by the deformation | transformation of the plate which arises when compression axial force acts on the 1st plate 40a can be suppressed.

  In addition, although the joining structure 4 which concerns on 4th embodiment is constructed | assembled by the method substantially the same as the joining structure 1 which concerns on 1st embodiment, it constructs as follows about concrete pile construction process S10.

  FIG. 7: is sectional drawing which shows concrete pile construction process S10 in construction of the junction structure 4 which concerns on 4th embodiment, The figure (a) is at the time of concrete placement, The figure (b) is at the time of concrete hardening. Show.

  As shown in FIG. 7A, in the construction of the joint structure 4 according to the fourth embodiment, when the plate 40 is provided in the concrete pile construction step S10, for example, the annular mold 19 having a tapered shape in the cross section is surrounded. In the state where the first plate 40a provided on the pile head is installed on the pile head, concrete is placed throughout the hole. As the annular mold 19, for example, a polystyrene foam material that can be easily removed after the concrete is hardened can be used.

  Then, as shown in FIG. 7 (b), after the concrete placed in the hole is cured, the annular mold 19 is removed, so that the first plate 40a comes into contact with the depressed portion, and the concrete pile 10 A structure having a tapered shape that reduces from the upper end surface of the concrete pile 10 toward the abutting portion 10a can be constructed in the depressed portion of the upper surface.

FIG. 8 is a cross-sectional view of the joint structure 5 according to the fifth embodiment.
As shown in FIG. 8, the joint structure 5 of the fifth embodiment is similar to the joint structure 4 of the fourth embodiment by making the planar shape of the first plate 40 a smaller than the planar shape of the concrete pile 10. The bending rigidity with respect to the bending moment generated in the joint structure is reduced.

  However, in the joint structure 5 of the fifth embodiment, instead of forming a depression on the top surface of the pile as in the joint structure 4 of the fourth embodiment, the steel pipe 60 that restrains the concrete of the pile head around the pile head is provided. Provided. In addition, what restrains the concrete of a pile head is not restricted to the steel pipe 60, What is necessary is just to be able to restrain the circumference | surroundings of concrete of a pile head, such as winding an FRP sheet or FRP fiber.

  In this structure, since the pile head is restrained by the steel pipe 60, the strength and deformation performance of the concrete at the time of compressive axial force action are improved, so that it is possible to suppress breakage due to splitting of the pile head.

  Moreover, although the joining structure 5 of 5th embodiment is constructed | assembled by the method substantially the same as the joining structure 1 which concerns on 1st embodiment, it constructs as follows in concrete pile construction process S10.

  FIG. 9: is sectional drawing which shows concrete pile construction process S10 in construction of the junction structure 5 which concerns on 5th embodiment, The figure (a) is at the time of concrete placement, The figure (b) is after concrete placement. Indicates.

  As shown to Fig.9 (a), in construction of the junction structure 5 which concerns on 5th embodiment, in concrete pile construction process S10, after providing the steel pipe 60 in the upper end in the excavated hole, concrete is laid. . And as shown in FIG.9 (b), after placing concrete in the whole hole, the plate 40 is mounted in the upper end, and the dowel reinforcement 50 is built.

  According to the joint structures 1 to 5 of each embodiment described above, the planar shape is smaller than that of the concrete pile 10, and the coupling portion 30 coupled to the footing 20 from the center of the upper surface of the concrete pile 10, By providing a plate 40 that surrounds the periphery and is interposed between the concrete pile 10 and the footing 20 without a gap and is stacked so as to be vertically separated from each other, the concrete pile 10 and the footing 20 The compression axial force acting between the two can be sufficiently transmitted through both the connecting portion 30 and the plate 40.

  Here, since the plate 40 surrounds the periphery of the connecting portion 30, the plate 40 constrains the expansion in the horizontal direction that occurs in the connecting portion 30 when a compression axial force acts on the connecting portion 30 from the periphery. The compressive strength of the connecting part 30 is improved.

  Further, when a bending moment is generated in the joint structures 1 to 5 of each embodiment, the bending rigidity is effectively reduced by separating the plates 40 on the side where the tensile stress is generated by the bending moment. Can do.

  Here, the bending rigidity decreases as the planar shape of the plate 40 becomes smaller, whereas the plate 40 is made of a material (steel material or precast concrete) having a compressive strength higher than that of the concrete pile 10 or the footing 20. Become. That is, by calculating the size of the planar shape of the plate 40 necessary for the compressive axial force acting between the concrete pile 10 and the footing 20 according to the material from the point of design of allowable stress, the plate 40 You may change a planar shape small.

  Further, when the plates 40 are separated from each other, the compressive stress is locally concentrated at the contact portion between the plates 40, but the first plate 40a and the upper surface of the concrete pile 10 are in contact with each other. Since the compressive stress to be concentrated is distributed over the entire bottom surface of the first plate 40a and transmitted to the top surface of the pile, damage to the head of the concrete pile 10 due to the stress concentration can be suppressed.

  As described above, according to the joining structures 1 to 5 of the embodiments, the concrete pile 10 firmly supports the footing 20 in normal times and suppresses damage to the head of the concrete pile 10 due to concentration of bending moment during an earthquake. can do.

  In the joint structure 4 of the fourth embodiment, the taper 10b is formed in the depressed portion on the upper surface of the pile. However, the present invention is not limited to this, and the taper 10c is also formed between the second plate 40b and the footing 20. Also good.

  FIG. 10 is a cross-sectional view showing a joint structure 400 in which a taper 10c is formed between the outer peripheral surface of the second plate 40b and the footing 20 in the joint structure 4 according to the fourth embodiment.

  According to the joining structure 400 shown in FIG. 10, by forming the taper 10c between the outer peripheral surface of the second plate 40b and the footing 20, the second plate 40b generated when a compression axial force acts on the second plate 40b. Damage to the footing concrete due to deformation of can be suppressed. This structure is also applicable to the joint structure 3 of the third embodiment or the joint structure 5 of the fifth embodiment.

  Further, the dowel rebar 50 used in the joint structures 1 to 4 according to the present embodiment is provided mainly for the function of transmitting the shearing force generated between the footing 20 and the concrete pile 10 and does not transmit the pulling force. However, in the joint structure located at the outer edge of the structure (hereinafter referred to as the outer column joint structure), a mechanism for transmitting the pulling force generated between the concrete pile 10 and the footing 20 is provided. Also good. This is because the pulling force may act between the concrete pile 10 and the footing 20 when a falling moment acts on the structure during the earthquake in the outer column joint structure. This is because it is necessary to communicate.

  FIG. 11 is a cross-sectional view of the outer column bottom joint structure 100. In addition, although FIG. 11 changes the dowel reinforcement 50 in the joining structure 1 of 1st embodiment, it is not restricted to this, About the dowel reinforcement 50 in the joining structures 2-5 which concern on 2nd-5th embodiment. Can be configured similarly.

  As shown in FIG. 11, in the outer column lower joint structure 100, the dowel rebar 50 used in the joint structure 1 is changed to a large core rebar 52 having a planar shape, and the rebar is fixed to footing concrete at the upper end of the core rebar 52. A fixing plate 54 is provided. Thereby, the tensile force produced between the concrete pile 10 and the footing 20 can be transmitted reliably.

  Further, the length of the core rebar 52 is sufficiently secured as compared with the dowel rebar 50, and the pile head region X is installed so that no adhesion occurs between the core rebar 52 and the concrete. Thereby, when a pulling force acts between the footing 20 and the concrete pile 10, the tensile stress transmitted from the footing 20 to the concrete pile 10 through the core rebar 52 is concentrated on the pile head without being concentrated. It can be transmitted to the inside of the pile from a position below the head region X. As a result, the pulling force is dispersed and transmitted from the inside of the pile in a wide range, thereby suppressing damage to the pile head. Can do.

  Even when a bending moment occurs, the bending moment tends to increase as it approaches the upper end of the pile, whereas the tensile axial force acting on the shear transmission member due to the bending moment spreads widely from the inside of the pile. Since it will be distributed and transmitted, damage to the concrete of a pile head can be controlled.

  Further, the horizontal force generated in the structure at the time of the earthquake is also effectively transmitted from the footing 20 to the concrete pile 10 through the core reinforcing bar 52, similarly to the dowel reinforcing bar 50.

  In addition, the outer column lower joint structure 100 includes the fixing plate 54 as a configuration for reliably transmitting the tensile force generated between the concrete pile 10 and the footing 20, but is not limited thereto, and the core reinforcing bar 52 and the footing are not limited thereto. 20 and the concrete pile 10 can be sufficiently secured, the fixing plate 54 need not be provided.

  Moreover, in the joining structure 2 which concerns on 2nd embodiment, although the diameter of the 1st plate 40a is made the same diameter as the concrete pile 10, it is not necessary to make the diameter of the 1st plate 40a necessarily the same diameter as the concrete pile 10. Absent.

  FIG. 12 is a cross-sectional view of the joint structure 200 when the diameter of the first plate 40a of the joint structure 2 of the second embodiment is set to be smaller than the diameter of the concrete pile 10.

  As shown in FIG. 12, when the diameter of the first plate 40 a is set smaller than the diameter of the concrete pile 10, the first plate 40 a is installed so as to be embedded in the head of the concrete pile 10. The diameter of the second plate 40b is set to be smaller than the diameter of the first plate 40a.

  Thus, by installing the first plate 40a so as to be embedded in the head of the concrete pile 10, the compression axial force transmitted from the footing 20 to the first plate 40a via the second plate 40b is applied to the concrete pile. By being disperse | distributed widely and transmitted to 10 from the inside of a pile, damage to the head of a pile can be suppressed.

  In addition, when setting the diameter of the 1st plate 40a to a different diameter from the concrete pile 10 in this way, while setting the diameter of the 1st plate 40a smaller than the diameter of the concrete pile 10, the 1st plate 40a is piled. It is also applicable to other joining structures, provided that the diameter of the second plate 40b, which is embedded in the head of the first plate 40a, is smaller than that of the first plate 40a. (For example, the joining structure 3 of the third embodiment).

  Moreover, in the joining structures 1-5 of each embodiment, although it decided to use what consists of a material (steel material or precast concrete) whose compressive strength is larger than the concrete pile 10 or the footing 20 as the plate 40, it is not restricted to this. Alternatively, a plate 405 having the following configuration may be used.

  13A and 13B show the plate 405. FIG. 13A is a cross-sectional view, and FIG. 13B is a cross-sectional view taken along the line BB in FIG.

  As illustrated in FIG. 13, the plate 405 includes a main body member 410 that surrounds the periphery of the connecting portion 30, and a restraining member 420 that is provided around the main body member 410 so as to restrain the main body member 410. The main body member 410 is concrete having a compressive strength equivalent to that of the concrete pile 10 or the footing 20, and the restraining member 420 is a steel pipe provided around the concrete.

  By configuring the plate 405 in such a configuration, the compression strength and toughness of the plate against a compressive load acting in the vertical direction can be improved as compared with the case of a single concrete configuration, and the plate 405 is used in the same manner as the plate 40. be able to.

  In addition, the compressive strength of main body member 410 itself is not specifically limited, If the compressive strength of the plate 405 which consists of the main body member 410 and the steel pipe 420 becomes larger than the concrete which comprises the concrete pile 10 or the footing 20. Good.

  The restraining member 420 is not limited to a steel pipe, and any member that can restrain the periphery of the main body member 410 such as winding an FRP sheet or FRP fiber may be used.

  Furthermore, the plurality of plates used in the bonding structures 1 to 5 of each embodiment may be configured by a single type of the plate 40 or the plate 405, or configured by a combination of a plurality of types of the plate 40 and the plate 405. It is good also as what to do.

The joining structure 1 which is 1st embodiment is shown, The figure (a) is sectional drawing, The figure (b) is AA sectional drawing of the figure (a). It is process drawing which shows the construction method of the junction structure 1 of 1st embodiment. It is sectional drawing for demonstrating the behavior of the junction structure 1 of 1st embodiment, The figure (a) shows the normal time, The figure (b) has shown the time of an earthquake. It is sectional drawing of the junction structure 2 which is 2nd embodiment. It is sectional drawing of the junction structure 3 which is 3rd embodiment. It is sectional drawing of the junction structure 4 which is 4th embodiment. It is sectional drawing which shows concrete pile construction process S10 in construction of joining structure 4 concerning a 4th embodiment, the figure (a) shows at the time of concrete placement, and the figure (b) shows at the time of concrete hardening. It is sectional drawing of the junction structure 5 which is 5th embodiment. It is sectional drawing which shows concrete pile construction process S10 in construction | assembly of the junction structure 5 which concerns on 5th embodiment, The figure (a) shows at the time of concrete placement, and the figure (b) shows after concrete placement. In the joint structure 4 according to the fourth embodiment, it is a cross-sectional view showing a joint structure 400 in which a taper 10 c is formed between the outer peripheral surface of the second plate 40 b and the footing 20. It is sectional drawing of the outer pillar lower junction structure 100. FIG. It is sectional drawing of the joining structure 200 at the time of setting the diameter of the 1st plate 40a of the joining structure 2 of 2nd embodiment smaller than the diameter of the concrete pile 10. FIG. The plate 405 is shown, the figure (a) is sectional drawing, the figure (b) is BB sectional drawing of the figure (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Junction structure concerning 1st embodiment 2 Junction structure concerning 2nd embodiment 3 Junction structure concerning 3rd embodiment 4 Junction structure concerning 4th embodiment 5 Junction structure concerning 5th embodiment DESCRIPTION OF SYMBOLS 10 Concrete pile 10a Contact part 10b, 10c Taper 12 Main reinforcement 14 Shear reinforcement 20 Footing 22 Formwork 30 Connection part 40, 40a, 40b, 40c, 405 Plate 50 Dowel reinforcement 52 Core reinforcement 54 Fixing plate 60 Steel pipe 100 Outer column bottom Bonding structure 410 Main body member 420 Restraining member S1 Concrete pile construction process S2 Footing form installation process S3 Concrete placing process X Pile head region

Claims (15)

It is a joint structure between the pile and the foundation provided on it,
A plane shape smaller than the pile, and a connecting portion that connects the center of the upper surface of the pile and the foundation,
It is made of a material having a higher compressive strength than the pile or the foundation, and surrounds the periphery of the connecting portion, and is interposed between the pile and the foundation, and is stacked so as to be separated from each other in the vertical direction. A joint structure of a pile and a foundation characterized by comprising a plurality of plates.   The said plate consists of steel materials or precast concrete, The joining structure of the pile and foundation of Claim 1 characterized by the above-mentioned.   2. The pile according to claim 1, wherein the plate includes a main body member surrounding the periphery of the connecting portion and a restraining member provided around the main body member so as to restrain the main body member. Joining structure with the foundation.   The pile-foundation structure according to any one of claims 1 to 3, wherein at least one of the plurality of plates has a planar shape smaller than the pile.   5. The pile-foundation joint structure according to claim 4, wherein one of the plurality of plates that is one upper than the lowermost plate has a smaller planar shape than the lowermost plate.   The number of layers of the plate is three, and the plane shape of the intermediate plate located in the middle of the plates stacked on the three sheets is smaller than the plane shape of the upper and lower plates of the intermediate plate. The joint structure between a pile and a foundation according to claim 4, wherein the pile is a foundation.   The plate having a smaller planar shape than the pile is a lowermost plate among the stacked plates, and a contact portion of the upper surface of the pile with the lowermost plate is a peripheral edge of the upper end surface of the pile. The pile-foundation structure according to claim 4, wherein the pile is depressed more than the portion.   The pile-foundation structure according to claim 7, wherein the depressed portion of the upper surface of the pile has a tapered shape that decreases from the upper end surface of the pile toward the contact portion.   9. The apparatus according to claim 1, further comprising a shear transmission member that extends through the connection portion between the pile and the foundation and transmits a shearing force between the pile and the foundation. The joint structure of the pile according to item 1 and the foundation.   The said shearing transmission member is not adhering to at least any one of the said pile or the said foundation, The joining structure of the pile and foundation of any one of Claims 1-9 characterized by the above-mentioned.   The said shear transmission member can transmit tensile force between the said pile and the said foundation by being fixed to the said pile and the said foundation, The any one of Claims 1-10 characterized by the above-mentioned. The joint structure of the pile and foundation described in the item.   The shear transmission member does not adhere to the pile in the head region of the pile, and is fixed to the pile at a position below the head region of the pile. Joint structure between pile and foundation.   The joint structure of the pile and foundation of any one of Claims 1-12 provided with the restraint member which restrains the concrete of the head of the said pile around the head of the said pile. A method for constructing a joint structure between a pile and a foundation provided on the pile,
A pile construction step of constructing a concrete pile having a plurality of plates having an annular shape stacked in the vertical direction so as to be separable from each other; and
The foundation construction formwork is installed on the upper side of the pile so that the space in the formwork and the space in the ring of the laminated plates communicate with each other, and in the formwork and the lamination A method for constructing a joint structure between a pile and a foundation, comprising: a concrete placing step for placing concrete in an annulus of a formed plate. A method of joining a pile and a foundation provided on the pile,
The center of the upper surface of the pile and the foundation are connected by a connecting portion having a planar shape smaller than the pile,
A method for joining a pile and a foundation, comprising interposing a plurality of plates stacked so as to be separated from each other in a vertical direction between the pile and the foundation while surrounding the periphery of the connecting portion.

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