JP2016089443A - Pile head joint construction method and structure having pile head joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pile head joint and its construction method, the pile head joint that has a simpler structure or construction method, in which the transmission of moment is prevented or reduced between a pile and a base beam, and strength to the force of a tensile direction and shift direction is provided.SOLUTION: A pile head joint 20 is constructed as follows: a formwork 22 provided with a hole of a predetermined radius is disposed so that a core rebar 26 penetrates through a hole part with respect to a pile head 13 having a predetermined curved surface shape and having a core rebar 26 of a pile projected into the upper side being an extending direction of the pile; the footing 16 is constructed by placing concrete so that the formwork 22 becomes the bottom; and thereby a circumferential edge of the hole part is made to come into contact with the pile head 13 slidably, and the formwork 22 is further brought into a line contact with the pile head 13 and the formwork 22 being slidable with the pile head 13 is provided.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a method for constructing a pile head joint located between a pile head of a concrete pile and a structure (including a foundation beam or a footing thereof) to be joined to the pile head, and the pile head joint. It is related with the structure which has.

  In a concrete structure, a concrete foundation beam or footing (hereinafter simply referred to as “foundation beam”) that forms part of the structure is provided on a concrete pile driven into the ground. In addition, pillars are built.

  In concrete structures, from the viewpoint of earthquake resistance and the like, conventionally, a rigid connection between the pile and the foundation beam, that is, a connection in which both are completely fixed is employed. In general, a force in the pulling direction, a force in the displacement (shearing) direction, and a pile head moment are generated between the pile and the foundation beam, and it is necessary to ensure strength that can withstand each. However, the rigid joint has a problem that stress caused by the pile head moment is concentrated on the pile head particularly during an earthquake. Therefore, when using rigid joints, it was necessary to provide more reinforcing bars on the piles and foundation beams. As a result, the structure where a large number of rebars are installed requires the foundation beams and piles themselves to be large, resulting in an increase in the cost of the structure.

  On the other hand, the pile head joining method which can reduce transmission of a pile head moment is proposed. Specifically, at the joint part of the pile head with the foundation beam, a method of joining by so-called semi-rigid joining in which the cross-sectional area of the pile head is reduced and then joined to the foundation beam, or the pile head and the foundation beam This is a method of pin joining that allows relative displacement of the pin. Patent document 1 is an example of the said pin joining, and while allowing a relative displacement by joining a pile head and a foundation beam with a laminated rubber body, and providing a restraint body, the amount of the displacement is a predetermined range. A structure that restricts to is proposed. In this way, unlike the pile head fixed connection, which is a rigid connection that connects the pile and the foundation beam (a state that constrains the rotational displacement of the pile head joint), the stress at the time of the earthquake generated at the pile head joint is greatly increased. The effect of being relaxed is obtained.

JP 2000-120082 A

  However, according to the pile head pin coupling described in Patent Document 1, the laminated rubber that allows relative displacement between the pile and the foundation beam, and the constraint for allowing deformation of the laminated rubber within a certain range. There is a problem that it is necessary to provide a body and the structure of the pile head joint is complicated. In addition, of the force generated at the pile head joint, especially the force generated at the joint between the pile and the foundation beam, the force in the pulling direction (longitudinal direction of the pile), the displacement direction (the direction of shearing the pile head joint) The strength against force may not be enough. In such a case, there is still much room for improvement in order to solve the problem of simplifying the structure of the pile head joint while exhibiting sufficient performance against the force applied to the pile head joint during an earthquake. was there.

  The present invention has been made in the background of the above circumstances, and its object is a pile head joint having a simpler structure or construction method, and transmission of moment between the pile and the foundation beam An object of the present invention is to provide a method for constructing a pile head joint having strength against a force in a pulling direction or a displacement direction and a structure having the pile head joint while preventing or reducing the above.

  The method for constructing a pile head joint according to claim 1 for achieving the object is as follows: (a) a pile head joint between a pile head of a concrete pile and a structure joined to the pile head. And (b) a pile head having a predetermined curved surface shape in a part of a contact surface with the structure and having the core reinforcing bar of the concrete pile protruded in the extending direction of the concrete pile. ) A frame plate portion provided with a hole having a predetermined radius (a hole larger than the thickness of the core rebar) is disposed so that the core rebar penetrates the hole, and (d) the frame plate portion By constructing the structure by placing concrete so that the bottom becomes the bottom, the peripheral edge of the hole and the pile head are slidably brought into contact with each other. Moreover, the structure which has the pile head joint part concerning Claim 2 is a pile head joint structure which is a junction part of the pile head of (a) concrete pile, and the structure joined with this pile head, (B) The pile head has a curved surface shape at a part of the contact surface with the structure, (c) the concrete pile has a core reinforcing bar provided in the extending direction, and (d) the core reinforcing bar. Protrudes in the direction of the structure from the plane portion, and (e) the structure has a frame plate portion at the joint with the pile head, and (f) a hole having a predetermined radius in the frame plate portion. (A hole larger than the thickness of the core rebar) is provided, and the core rebar is inserted into the structure through the hole, and the periphery of the hole and the pile head are slidably in contact with each other. It is made to be made to be made.

  According to the construction method of the pile head joint part according to claim 1 and the structure having the pile head joint part according to claim 2, a part of the contact surface has a predetermined curved surface shape, and the core reinforcing bar of the concrete pile Is arranged such that a frame plate portion having a hole with a predetermined radius is provided to the pile head projected in the extending direction of the concrete pile so that the core rebar penetrates the hole, and the frame plate portion is Because the pile head joint is constructed so that the peripheral part of the hole and the pile head can be slidably contacted by constructing the structure by placing concrete so that it becomes the bottom In addition, it is possible to provide a pile head joint having a structure in which the concrete pile and the structure are relatively easily changed. In addition, the pile head having a curved surface and the frame plate portion having a hole come into contact with each other and are slidable. Therefore, the pile head and the frame plate portion have a convex curved surface and a concave curved surface, respectively. Since the curved surfaces do not need to be processed with high precision as in the case where they are configured to be in surface contact with each other, the construction is facilitated.

  Preferably, in the construction method of the pile head joint or the structure having the pile head joint, (a) the pile head has a metal lid that covers the surface of the pile head; The lid portion has a lid hole portion through which the core rebar is inserted. In such a configuration, the metal lid having a lower coefficient of friction than the concrete pile head and the frame plate of the structure are in contact with each other, so the pile head and the structure are easily displaced relatively. Therefore, even when a large force such as an earthquake acts on the pile head, the pile head moment is not transmitted and can be released.

  Further preferably, the construction method of the pile head joint portion or the pile head joint structure is such that at least one of the lid portion and the frame plate portion contacts at least the lid portion and the frame plate portion. It is characterized by being processed to reduce friction. In such a configuration, since the friction between the pile head and the structure becomes smaller, the pile head and the structure are easily displaced relatively, so a large force such as an earthquake acts on the pile head The pile head moment can not be transmitted even in the case of escape.

  Preferably, the lid portion is provided with a reinforcing material for preventing the lid portion from being deformed by a force applied radially outward to the lid portion. In such a configuration, when the axial force is transmitted to the pile head in the structure, the deformation of the lid can be suppressed even when the axial force tends to spread in the radial direction of the pile. . This reinforcing material is preferably an annular metal, and is provided on the inside or outside of the lid by welding or the like so as to surround the lid in the circumferential direction.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining an embodiment of the present invention. As shown in FIG. 1, between the pile 12 and the structure 14, more precisely, the pile head 13 that is the top of the pile and the footing 16 provided on the foundation beam 15 of the structure 14 are connected to the pile head. It is joined at the portion 20. The pile head joint portion 20 is a joint portion between the pile 12 and the structure 14, and specifically includes at least a pile head 13 and a formwork 22 described later. More specifically, the lid portion 24 and the lid hole portion 24 constituting the pile head 13, the pile main reinforcement 28 and the reinforcing frame 30 constituting the pile 12, and the formwork 22 that actually contacts the pile head 13 among the structures 14, the formwork The core 21 may include a recess 21 and a mold hole 23 provided on the core, and a core rebar 26 that connects the pile 12 and the footing 16. In the example of FIG. 1, the structure 14 is provided with four footings 16 on the four piles 12, and the pile head joints 20 with respect to the four piles 12 and the corresponding footings 16. Is provided. The pile head joint part 20 in a present Example respond | corresponds to the pile head joint structure of this invention. In addition, the number of the above-mentioned piles 12 in the present Example, the number of the footings 16, the magnitude | size of a structure, etc. are only examples, and aspects other than this are also possible.

  FIG. 2 is an external view for explaining the pile head joint portion 20, that is, the portion surrounded by the circle A in FIG. 1 in an enlarged manner. As shown in FIG. 2, the pile head 13 which is the upper end portion of the pile 12 is covered with a lid portion 24. The pile head 13 and the cover part 24 have a spherical shape in a part of the contact surface. The contact surfaces have curved surfaces such as a substantially spherical shape at positions facing each other. In addition, in the following description, the pile head 13 part including the cover part 24 is called a pile head. The pile 12 is provided by placing concrete in a vertical shaft after placing a pile main reinforcement 28 and a reinforcing frame 30 (see FIGS. 4 to 6), which will be described later. For example, the portion is provided by cutting so as to have the curved surface shape. For example, mortar is applied as an adhesive to the pile head 13 thus provided, and the lid portion 24 is covered. In this way, the lid portion 24 is fixed to the pile head 13.

  A mold 22 is provided at the bottom of the footing 16. This mold 22 corresponds to the frame plate portion of the present invention. The mold 22 includes a bottom mold 22a for forming the bottom of the footing 16 and a recess mold 22b for forming the recess 21 constituting the pile head joint. The recess form 22b is indicated by a broken line in FIG. By placing concrete along the mold 22, a concave portion 21 having a concave shape is formed on the upper side (the upper side in FIG. 2) as seen from the bottom of the footing 16. As shown by the dotted line in FIG. 2, the pile head, that is, the tip of the pile head 13 is accommodated in the recess 21. The formwork 22 is used as a formwork when the concrete is placed and the footing 16 is constructed. When the concrete is placed after the formwork 22 is provided on the pile 12. May be used as a mold and may be a so-called discarded mold without being removed after the concrete has been placed. The mold 22 is fixed to the footing 16 by a known method such as an anchor bolt (not shown).

  FIG. 3 is a diagram for explaining the configuration of the pile head and the configuration of the pile head joint 20 in the present embodiment. Among these, Fig.3 (a) is the figure which looked at the longitudinal direction front-end | tip part of the pile 12 from the top (upper in FIG. 2). In the present embodiment, the pile 12 has a columnar shape, and at least a part of the pile head 13 which is a tip portion thereof is covered with a lid portion 24. The lid portion 24 is a plate having a curved surface shape as described above, and is, for example, iron or stainless steel. In the present embodiment, the lid portion 24 is formed of a steel plate having a thickness of about 9 mm, for example. The lid portion 24 may be used as a discarded mold when the pile 12 is constructed by placing concrete. The curved surface shape of the lid portion 24 corresponds to the shape of the pile head 13. For example, when the pile head 13 has a spherical shape, the lid portion 24 also has a spherical shape. In this way, the inner surface of the lid portion 24 and the outer surface of the pile head 13 are bonded via the mortar as the adhesive applied between them. Further, the lid portion 24 is provided with a through hole as a lid hole portion 25 at the center portion of the pile head 13 in FIG. Therefore, the concrete of the pile head 13 at the top of the pile 12 is exposed through the lid hole 25. In addition, the concrete of the pile head 13 exposed from the lid hole portion 25 may have a planar shape with the lid hole portion 25 as an edge, or a curved shape so as to be continuous from the lid portion 24. A convex portion having a curved surface shape may bulge from the lid hole portion 25. Further, a plurality of core reinforcing bars 26 are provided inside the pile 12 so as to extend in the longitudinal direction of the pile 12, and the core reinforcing bars 26 are extended so as to protrude from the tip end portion of the pile 12. In addition, in FIG. 3A, the code | symbol of some core reinforcing bars 26 provided on the concentric circle of the pile 12 is abbreviate | omitted. A plurality of pile main bars 28 are provided concentrically on the outer side of the pile 12 in the radial direction of the pile 12 so as to extend in the longitudinal direction of the pile 12. In FIG. 3A, some of the pile main bars 28 are also omitted. The plurality of core rebars 26 are provided at positions passing through the lid hole 25 and protrude vertically upward from the pile 12 so as to penetrate the lid hole 25. As will be described later, these core reinforcing bars 26 are used as reinforcing bars for fixing the pile 12 and the footing 16.

  Moreover, FIG.3 (b) is a figure explaining the relationship with the formwork 22 which comprises the pile head junction part 20, Comprising: It is a figure which shows the AA 'cross section of the pile 12 in Fig.3 (a). . As shown to Fig.3 (a), when the diameter of the pile 12 in the pile head 13 is set as the pile head diameter B, the diameter of the cover part 24 is the outer diameter Bo, and the diameter of the cover hole part 25 in the cover part 24 is Bi. , The size of the recess 21 is determined so that the pile head 13 is accommodated in the recess mold 22 b of the mold 22. That is, the diameter βo of the recess 21 (see FIG. 6B) is set larger than the pile head diameter B. Further, the recess mold 22b is provided with a mold hole 23 having a predetermined radius that penetrates the recess mold 22b. The mold hole 23 corresponds to a hole having a predetermined radius according to the present invention. As will be described later, the mold hole 23 is arranged so that the core rebar 26 extends into the footing 16 through the mold hole 23.

  Further, when concrete is placed after the concave form 22b is placed in contact with the lid portion 24 of the pile head, the placed concrete, ie, the footing 16 is exposed from the lid hole 25. The pile head joint 20 is formed by joining with the concrete of the head 13. At this time, the diameter βi (see FIG. 6B) of the mold hole portion 23 (contact circle in FIG. 3B) is smaller than the outer diameter Bo of the lid portion 24 and is smaller than the inner diameter Bi. It is determined to be larger. That is, the diameter βi of the mold hole 23 corresponding to the predetermined radius of the present invention is larger than the inner diameter Bi surrounding the portion where the core rebar 26 is provided in the pile head 13 of the pile 12. Has been. The area of the contact surface (contact circle) between the footing 16 and the pile head 13 in the pile head joint 20 is, for example, about 0.8 times the column area. This is determined in consideration of the fact that the concrete shaft strength is expected to increase by about 20% due to the restraining effect of the restraining material. The area of this contact surface is, for example, in relation to the thickness of the pile 12, the diameter βi of the contact surface is about 1/3 of the pile diameter.

  In addition, the size of the inner diameter Bi in the pile head 13, that is, the diameter Bi of the lid hole portion 25 of the lid portion 24 in the pile head 13 is at least when the number of core rebars 26 is determined by a method described later, for example. The number of core rebars 26 is the size that can be arranged. Specifically, for example, the size is about 1/3 to 1/4 of the pile diameter B (diameter in a plane perpendicular to the longitudinal direction of the pile). Furthermore, the size of the outer diameter Bo at the pile head 13, that is, the diameter Bo of the lid portion 24 at the pile head 13 is the slip of the pile head that occurs when the pile 12 and the footing 16 rotate relatively (Rθ, The footing 16 and the pile 12 are determined so as not to interfere with each other. Specifically, for example, the size is about ½ of the pile diameter B.

  FIG. 4 is a diagram illustrating an A-A ′ cross section of the pile 12 in FIG. 3. The A-A ′ cross section in FIG. 3 is a cross section obtained by cutting the pile 12 in the longitudinal direction. As shown in FIG. 4, a pile head 13 that is a tip portion of the pile 12 is covered with a lid portion 24, and a lid hole portion 25 provided, for example, in a notch is provided at the center of the lid portion 24. It has been. As described above, a plurality of core rebars 26 fixed inside the pile 12 protrude from the pile head 13 through the lid hole portion 25. In order to maintain the strength of the pile 12, a plurality of pile main bars 28 are provided in the longitudinal direction of the pile 12. Further, the pile 12 is provided with a reinforcing frame 30 for restraining the concrete of the pile head 13 and fixing the core rebar, and also provided with a binding wire 32 for positioning the pile main reinforcement 28. In addition, in the example of FIG. 4, although the reinforcement frame 30 is provided in the upper part of the pile 12 containing the pile head 13, it achieves the objective of restraining the concrete of the pile head 13 as mentioned above. If there is any, how much part of the pile 12 is provided with the reinforcing frame 30 is not limited, and if the concrete of the pile head 13 is sufficiently strong without providing the reinforcing frame 30, the reinforcing frame 30 is not necessarily reinforced. There is no need to provide the frame 30.

  FIG. 5A is a diagram for explaining a B-B ′ cross section of the pile 12 in FIG. 4. The B-B ′ cross section in FIG. 4 is a cross section perpendicular to the longitudinal direction of the pile 12. As shown in FIG. 5, a reinforcing frame 30 is provided at the tip of the pile 12 including the pile head 13. The reinforcing frame 30 is surrounded by, for example, an annular inner annular frame 30a of a size that surrounds the plurality of core reinforcing bars 26, that is, an outer side of the plurality of core reinforcing bars 26, and a plurality of pile main reinforcing bars 28. In the cross section of the pile for connecting the outer annular frame 30b having an annular shape, that is, inside the plurality of pile main bars 38, and the inner annular frame 30a and the outer annular frame 30b. It includes a connecting frame 30c that extends (for example, concentrically in its cross section). The reinforcing frame 30 is made by, for example, forming rod-shaped steel or the like on, for example, an inner annular frame 30a having a predetermined shape, an annular outer annular frame 30b, and a connecting frame 30c and welding them. The reinforcement frame 30 can restrain the concrete at the pile head 13 or the like, and the strength of the pile head 13 can be increased even when a shearing force is applied between the pile head 13 and a mold 22 described later. Can be maintained. Further, by fixing the core reinforcing bar 26 using the inner annular frame 30a of the reinforcing frame 30 and fixing the pile main reinforcing bar 38 using the outer annular frame 30b, that is, arranging the reinforcing bars 30, the core reinforcing bar 26 and the pile main reinforcing bar 28 are arranged. Therefore, there is no need to separately provide a member for fixing, and the cost can be reduced.

  FIG.5 (b) is a figure for demonstrating the structure of the pile head 13 of the pile 12, Comprising: It is the figure which looked at the pile head 13 from the direction orthogonal to a longitudinal direction. In FIG. 5 (b), concrete to be placed is omitted for explanation. As shown in FIG. 5B, a plurality of core reinforcing bars 26 fixed to the reinforcing frame 30 are provided so as to protrude upward from the inside of the pile 12, and the plurality of core reinforcing bars 26 are It extends through the lid hole 25 of the lid 24. The plurality of pile main bars 28 are fixed to the reinforcing frame 30 and are connected to each other by a binding wire 32 to be fixed in position. In addition, the number of core rebars is determined according to the magnitude | size of the shear force which arises in the pile head junction part 20, so that it may mention later. Specifically, for example, based on the magnitude of the shear force at the end of the time when a force in the shear direction is applied (at the end of bending), with a certain margin so as not to break due to the shear force at the end It is determined. The pile 12 is, for example, a cast-in-place pile, and is provided by placing concrete after the pile main reinforcement 28, the reinforcing frame 30, the core reinforcement 26, and the like are disposed in the hole dug in the ground. Further, if necessary, the portion of the pile head 13 on which the concrete has been placed is cut out so that the surface corresponding to the curved surface having a predetermined radius is a flat portion corresponding to the cover hole 25. In this way, the shape is adjusted.

  FIG. 6 illustrates the shape of the mold 22. Of these, FIG. 6A shows the mold 22 viewed from the lower side (that is, the lower side in FIGS. 2 and 4, in other words, the pile 12 side). It is a figure. 6B is a cross-sectional view taken along the line CC ′ in FIG. 6A, and is a cross-sectional view when the mold 22 is viewed from the side (in other words, FIGS. 2 and 4 are viewed from the front). is there. The mold 22 is made of a metal plate such as a steel plate having a thickness of about 9 mm. The mold frame 22 is provided with a mold hole portion 23 which is a circular hole. The diameter of the mold hole 23 is βi. Further, a stepped portion 34 of the mold 22 is concentric with the center of the mold hole 23 and has a diameter larger than the diameter βi of the mold hole 23 so as to rise upward from the bottom mold 22a. Is provided. The step 34 is projected upward by a predetermined height γ from the bottom mold 22 by, for example, pressing. In other words, the bottomed cylindrical step 34 having the mold hole 23 on the bottom surface is provided as the concave mold 22b so that the bottom surface is on the top.

  FIG. 7 is a view when the footing 16 is constructed on the pile 12, and the configuration of the pile head joint 20 which is the joint between the pile head 13 and the footing 16 in the present invention and the construction method thereof will be described. FIG. Subsequently, the formwork 22 is overlaid on the pile 12 constructed as described with reference to FIG. At this time, the mold is such that the center of the lid portion 24 covered by the pile head 13 or the lid hole portion 25 thereof substantially coincides with the center of the step portion 34 of the mold frame 22 or the hole portion 23 of the mold frame 22. By installing the frame 22, the core rebar 26 of the pile 12 protruding through the lid hole portion 25 of the lid portion 24 passes through the hole portion 23 of the mold frame 22, and is then placed in the concrete of the footing 16 to be placed. Is located. Then, a concrete frame for the footing 16 is installed, and the footing 16 is constructed by placing concrete. At this time, the above-described mold frame 22 can be used as a part of the concrete frame. And the formwork 22 is used integrally with the footing 16 as it is even after the concrete is solidified.

  In the pile head joint portion 20 constructed in this way, as shown in FIG. 7, the pile 12 and the footing 16 are individually formed, and the lid portion 24 of the pile head 13 in contact with the footing 16 has a spherical shape. Therefore, when a particularly large pile head moment is applied, the pile 24 slides between the lid portion 24 of the pile head 13 and the peripheral edge portion of the formwork hole portion 23 of the footing 16. And the relative displacement of the footing 16 are allowed. At this time, since the peripheral edge of the mold hole 23 provided in an annular shape and the lid portion 24 having a spherical shape are in line contact, the relative displacement between the pile 12 and the footing 16 is smoother. Can be generated.

  Furthermore, in the pile head joint part 22 constructed in this way, in addition to being able to allow relative displacement between the pile 12 and the footing 16 when a pile head moment occurs as described above, Since the core rebar 26 is disposed between the pile 12 and the footing 26, it is sufficient for the force in the pulling direction (the longitudinal direction of the pile) and the force in the displacement direction (the direction in which the pile head joint is sheared). Have high rigidity.

  As shown in FIG. 3 described above, the diameter βi (see FIG. 6) of the mold hole 23 (contact circle in FIG. 3) of the mold 22 is larger than the diameter Bi of the lid hole 23 of the cover 22. Value. Further, the protruding length γ of the step portion 34 is the length of the pile head 13 in the protruding direction of the mold 22 (vertical direction in FIG. 6), and the relative relationship between the pile 12 and the footing 16 when a pile head moment occurs. Is determined in consideration of the maximum value of the amount of displacement. Specifically, as shown in FIG. 10 to be described later, when the pile 12 and the footing 16 are relatively displaced, the stepped portion 34 falls from the top of the lid portion 22 with respect to the assumed maximum displacement amount. The size is determined so that it does not occur. The length of the pile head 13 in the protruding direction of the mold 22 is determined by the thickness of the pile and the radius corresponding to the spherical shape of the pile head.

  FIG. 8 is a diagram illustrating a pile head joint portion configured according to the present embodiment, that is, a structure 14 having a pile head joint structure. The transmission of the axial force (force in the vertical axis direction) via the pile head joint 20 will be described with reference to FIG. As shown in FIG. 8, the pile 12 and the footing 16 are joined by a pile head joint portion 20. The footing 16 is provided integrally with the foundation beam 15 extending in the horizontal direction, and a column 17 is provided on the footing 16. These foundation beam 15 and column 17 are both made of reinforced concrete.

  A column main bar 19 is passed through the column 17 in the longitudinal direction (that is, the vertical direction in FIG. 9). The column main bar 19 extends further downward and reaches the inside of the footing 16. As described above, the pile main reinforcement 26 of the pile 12 also extends into the footing 16 through the pile head joint portion 20. A plurality of restraining members 18 for restraining the column main bars 19 and the pile main bars 26 are provided in the footing 16.

  In the configuration shown in FIG. 8, a load corresponding to the mass of the structure or the like is transmitted from the column 17 to the footing 16 below it as an axial force, that is, an axial force N. This axial force N is transmitted so as to spread within the footing 16 as conceptually indicated by a plurality of arrows (hereinafter referred to as “arrow N1”) denoted by reference numeral N1. Since the restraining material 18 is provided in the footing 16 as described above, the axial force that once tried to spread in the direction of the arrow N1 is referred to as a plurality of arrows (hereinafter referred to as “arrow N2”) denoted by the symbol N2. ) And concentrate again toward the center of the restraint 18. As a result, the axial force N is transmitted as an axial force N3 in the axial direction (downward in FIG. 9) from the footing 16 vertically downward to the pile 12 via the pile head joint 20.

  The axial force N3 transmitted from the footing 16 to the pile 12 has a plurality of arrows (hereinafter referred to as “arrow N4”) denoted by a symbol N4 in the pile 12 because the pile head 13 has a substantially spherical shape. .) Tries to spread from the center of the pile toward the outside in the radial direction. Therefore, it is conceivable that an outward force (F in FIG. 9 to be described later) is also applied to the pile head 13 and the lower portion of the lid portion 24 tends to spread. Accordingly, a reinforcing member 35 may be attached to the lid portion 24 in order to prevent the lid portion 24 from being deformed.

  The footing 16 and the pile 12 are in contact with each other at a pile head joint portion 20 having a narrow cross-sectional area. Therefore, in the transmission of the axial force between the footing 16 and the pile 12, the force concentrates on the pile head joint portion 20. Therefore, the reinforcing frame 30, particularly the reinforcing frame 30 a that reinforces the core rebar 26, is provided as described above so that the pile head does not break.

  In FIG. 8, the shape of the lid 24 is different from that of FIG. 3, but this shows another embodiment of the lid 24. That is, the lid 24 may be provided so as to cover only the substantially spherical convex portion of the pile head 13 as shown in FIG. 3 or the like, or the convex portion of the pile head 13 as shown in FIG. In addition, it may be provided so as to cover the upper part of the pile 12. Thus, the cover part 24 should just cover the part which slides with the peripheral part of the formwork hole part 23 in at least one part of the substantially spherical part of the pile head 13, ie, the pile head junction part 13. FIG.

  FIG. 9 is a diagram for explaining the outline of the configuration in which the reinforcing material is provided. The reinforcing member 35 is, for example, a reinforcing bar formed in an annular shape, and is configured to be fixed to the inner side (pile side) of the lid portion 24 by welding or the like as shown in FIG. Note that the reinforcing member 35 may be welded and fixed to the outside of the lid 24 as long as it does not hinder sliding between the lid 24 and the mold 22. With this reinforcing material 35, the force from the pillar 17 acts in the direction F of FIG. 9 on the pile head 13 and the lid portion 24, and the lid portion 24 can be prevented from spreading.

  FIG. 10 is a diagram for explaining a state in which the pile 12 and the footing 16 are relatively displaced when a lateral force Fs is applied to the structure having the pile head joint portion 20 of the present embodiment. In FIG. 10, the position of the pile 12 before displacement is indicated by a one-dot chain line, and the position of the pile 12 after displacement is indicated by a solid line.

  When a lateral force Fs is applied to the structure 20, the lateral force is transmitted from the footing 16 to the pile 12 joined by the pile head joint portion 20 by the core rebar 26, and a shearing force Q acts respectively. It will be. Before the lateral force Fs is applied, the pile head 13 of the pile 12 and the footing 16 are attached to each other at the pile head joint portion 20. When the lateral force Fs is large enough to break this adhesion, the force is transmitted by the contact between the side surface 34a of the step 34 of the mold 22 and the side surface 13a of the pile head 13.

  When the lateral force Fs is transmitted, a slip S is generated between the lid 24 of the pile head 13 and the edge of the hole 23 in the mold 22 of the footing 16. At this time, since the pile head portion 13 and the lid portion 24 have a substantially spherical shape as described above, the pile head portion 13 and the lid portion 24 are in line contact with the end edge portion of the annular hole portion 23 and slip smoothly. be able to.

Thus, a shearing force acts on the pile head 13 and the footing 16, and both move relative to each other in the horizontal direction, so that the axis is displaced and a bending moment M _θ is generated. Here, the magnitude of the bending moment M _θ is
M _θ = Nδ + h ₀ Q
It is represented by N is the magnitude of axial force (N), δ is the magnitude of horizontal displacement (m), h ₀ is the height of the spherical surface of the pile head 13 (m), and Q is the shearing force (N). In FIG. 10, B is a pile diameter (m), R is a rotation radius (m) of the lid 24, and θ is a rotation angle (rad) of the pile 12.

  Since the pile head is displaced by B / 2 sin θ in the vertical direction as shown in FIG. 10 due to the rotation of the pile 12, the value of the rotation radius R is set so that the pile head 13 and the footing 16 do not interfere with each other. It is determined. Specifically, for example, the rotation radius R is determined as R = B / 2. Here, B is the pile diameter.

  According to the above-described embodiment, a predetermined radius is applied to the pile head 13 having a predetermined curved surface shape at a part of the contact surface and the core rebar 26 of the pile 12 protruding upward in the extending direction of the pile 12. The mold 22 provided with the hole 23 is disposed so that the core rebar 26 penetrates the hole 23, and the footing 16 is constructed by placing concrete so that the mold 22 becomes the bottom. By this, since the peripheral part of the formwork hole part 23 and the pile head 13 are brought into slidable contact, the pile head joint part 20 having a structure in which the pile 12 and the footing 16 are relatively likely to fluctuate is provided. be able to. Further, the pile head 13 having a curved surface shape and the mold frame 22 having the mold frame hole portion 23 come into contact with each other, and they can be slid, so that the pile head 13 and the mold frame 22 have a convex curved surface and a concave curved surface, respectively. As in the case where they are configured so that they are in surface contact with each other, it is not necessary to process the curved surfaces with high precision, so that the construction becomes easy.

  Moreover, according to the above-mentioned Example, the pile head 13 has the metal cover part 24 which covers the surface of the pile head 13, and the cover part 24 has the cover hole part 25 in which the said core rebar 26 is penetrated. Since the metal lid 24 having a lower coefficient of friction than the concrete pile head 13 and the mold 22 of the footing 16 are in contact with each other, the pile head 13 and the footing 16 are easily displaced relatively. Therefore, even when a large force such as an earthquake acts on the pile head 13, it is not necessary to transmit the pile head moment to the foundation beam, and it can be released. Therefore, the cost required for constructing the structure 14 can be reduced by several percent.

  In the above-described embodiment, at least one of the lid 24 and the mold 22 is processed to reduce friction at least in a range where the lid 24 and the mold 22 are in contact with each other. It is characterized by. In this way, since the friction between the pile head 13 and the structure 14 becomes smaller, the pile head 13 and the structure 14 are easily displaced relatively, so that a large force such as an earthquake is applied to the pile head. Even when acting, the pile head moment is not transmitted and can be released.

  Subsequently, another embodiment of the present invention will be described. In the following description, portions common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  FIG. 11 is a diagram for explaining another embodiment of the present invention and corresponds to FIG. In the above-described embodiment, as shown in FIG. 7 and the like, the pile head 13 is a substantially spherical convex portion from the radial center of the tip portion of the pile 12, and the other portion is on the axis of the pile 12. The cross-sectional shape was vertical. In other words, the pile head diameter B and the outer diameter Bo are different from each other, but the present invention is not limited to such a mode. That is, as shown in FIG. 11, a substantially spherical convex portion may be provided over the entire radial direction of the tip portion of the pile 12. Even if it is such an aspect, when the pile head 13 is accommodated in the step part 34, the effect similar to the above-mentioned Example will be produced.

  FIG. 12 is a diagram for explaining another embodiment of the present invention and corresponds to FIG. In the above-described embodiment, as shown in FIG. 7, the step 22 is provided by forming the mold 22 from the bottom mold 22a and the recess mold 22b. In the present embodiment, the step portion 34 is constituted by a member different from the mold 22, specifically, an annular metal 38 attached to the mold 22. In the following embodiments, the pile head 13 will be described using the same shape as that shown in FIG. 11, but the shape of the pile head 13 is the same as that shown in FIG. Even if it exists, it is applicable similarly.

  As shown in FIG. 12, as in the above-described embodiment, the mold 22 of this embodiment is in contact with the lid portion 24 placed on the pile head 13, and the lid hole through which the core rebar 26 extending from the pile 12 passes. Although it has the part 25, it does not have the mold 22b for recessed parts in the above-mentioned Example, but is comprised from the plate-shaped mold 22. In other words, in this embodiment, the mold 22 is composed only of the bottom mold 22a, and the mold hole portion 23 is provided in the bottom mold 22a. The annular metal 38 has a shape such as a rectangular cross section, for example, and the height γ in the vertical direction is designed similarly to the height γ of the step portion 34 in the above-described embodiment. The upper end of the annular metal 38 is integrally fixed to the mold 22 by, for example, welding. The size of the annular metal 38 and the position to be fixed are the same when the relative movement between the pile 12 and the footing 16 is performed as in the case of the step 34 of the first embodiment. Even in this case, the pile 12 is determined so as not to get over the step portion 34 (annular metal 38). Further, the annular metal 38 may have a uniform cross section, or may be hollow as long as the strength in view of the above-described object is obtained.

  In the above-described embodiment, since the step portion 34 is an annular metal 38 provided on the mold 22 in the present embodiment, the same effect as the above-described embodiment by providing the step portion 34 can be obtained. In addition, since the mold 22 has a planar shape, it is possible to obtain an effect that its manufacture is easy and inexpensive.

  FIG. 13 is a view for explaining still another embodiment of the present invention and corresponds to FIG. In FIG. 7 described above, the pile head joint portion 20 is provided so that the lid portion 24 of the pile head 13 and the peripheral edge portion of the mold hole portion 23 of the mold frame 22 are in contact with each other. On the other hand, in FIG. 13, the lid portion 24 of the pile head 13 is in contact with the lid portion 24 of the pile head 13 at another portion provided in the mold frame in addition to the peripheral edge portion of the mold frame hole portion 23. Is different.

  That is, in FIG. 7 described above, the concave mold 22b of the mold 22 forms a bottomed cylindrical concave, but in this embodiment, as shown in FIG. The recess mold 22b is provided with a recess made of a combination of two bottomed cylinders having different diameters and depths. Specifically, the recess mold 22b is a relatively small subtotal provided concentrically with the first recess, together with a bottomed cylindrical first recess having a relatively large diameter and a shallow bottom from the bottom mold 22a. A deep bottomed cylindrical second concave portion is provided to overlap. Accordingly, the recess mold 22b is provided with the first step 34a by the first recess and the second step 34b by the second recess, and the first step 34a and the second step 34b. A convex portion 37 is provided between the two.

  Here, the size of the diameter and the depth of the first recess and the second recess is such that both the peripheral edge of the mold hole portion 25 and the convex portion 37 of the mold frame for recess 22 are formed on the lid portion 24 of the pile head 13. The size is determined so that it touches. In the concave mold 22b thus formed, both the peripheral edge of the mold hole 25 and the convex 37 can contact the lid 24 of the pile head 13, so that the load concentration at the contact portion is concentrated. Can be relaxed.

  FIG. 13B is a diagram illustrating still another aspect in which the convex portion 37 is provided. Instead of providing the first recess and the second recess in FIG. 13A, in FIG. 13B, a single recess is provided by the recess mold 22b as in the example shown in FIG. The convex portion 37 is provided by providing the annular metal member 40 on the surface of the concave portion facing the pile head 13.

  Specifically, the annular metal member 40 is fixed to the recess mold 22b by welding or the like. For example, since the metal member 40 has a rectangular cross section, the corner on the opposite side (the lower side in the figure) from the side in contact with the recess mold 22b and the inner side in the circumferential direction is the lid of the pile head 13 The convex portion 37 is in contact with the portion 24. The size and the mounting position of the metal member 40 are the same as in FIG. 13A. The peripheral edge of the mold hole portion 23 of the recess mold 22b and the projection 37 are the same as the lid 24 of the pile head 13. It is decided so that it can touch at the same time.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

  For example, the shape of the pile head 13 has a predetermined curved surface shape in the above-described embodiment. However, the shape is not limited to this, and may be a shape that can slide smoothly when displaced relative to the mold 22. For example, other shapes, for example, a part of an elliptical sphere may be used.

  Moreover, the number of the core reinforcement 26 and the pile main reinforcement 28 in the above-mentioned Example is an example, and is not limited to what was illustrated. Further, the shape of the reinforcing frame 30 is not limited to that of the embodiment, and the number of the connecting frames 30c is different, and the shapes of the inner annular frame 30a and the outer annular frame 30b are, for example, polygonal. It does not have to be annular.

  Moreover, in the above-mentioned embodiment, the shape of the pile 12 is shown to have a cylindrical cross section. However, the shape is not limited to this, and the pile head 13 having the shape of the present embodiment is provided on a prismatic pile. May be.

  Moreover, in the above-mentioned Example, the footing 16 was provided in the lower part of the structure 14, and the pile head joined part 20 was comprised by the pile head 13 and the footing 16 of the pile 12, In the case where the footing 16 is not provided on the structure 14 without being limited thereto, the pile head joint 20 may be configured by the pile head 13 and the foundation beam.

  Moreover, although the cross-sectional shape of the annular metal 38 in the above-described second embodiment is a rectangle, the shape is not limited to this, and may be a circle or an ellipse. In short, any shape may be used as long as it is slidable in line contact with the lid 24 while pressing the lid 24. Similarly, the cross-sectional shape of the annular metal 40 in the above-described fourth embodiment is not limited to a rectangular shape, and may be any shape as long as the convex portion 37 can be formed.

  Moreover, in the above-mentioned Example 4, the cover part 24 and the formwork 22 of the pile head 13 are slidable in two places, the peripheral part of the formwork hole part 25 and the convex part 37 of the formwork 22b for recessed parts. Although it touched, you may touch in more places.

It is a figure explaining the outline | summary of the structure and pile to which the pile head junction part which is one Example of this invention is applied. It is a figure explaining the general view of the pile head junction part which is one Example of this invention. It is a figure explaining the structure at the time of seeing the pile head which comprises the pile head junction part which is one Example of this invention from the top. It is a figure explaining the cross section of the longitudinal direction of the pile head which comprises the pile head junction part which is one Example of this invention, Comprising: It is A-A 'sectional drawing of FIG. It is a figure explaining the structure of the pile which comprises the pile head junction part which is one Example of this invention. (A) is a figure explaining the cross section perpendicular | vertical to the longitudinal direction of a pile, and is B-B 'sectional drawing of FIG. (B) is a figure explaining the structure of a pile head part except for concrete. It is a figure explaining the structure of the form which comprises the pile head junction part which is one Example of this invention, Comprising: (a) is the figure seen from the downward direction. (B) is C-C 'sectional drawing in (a). It is a figure explaining the structure of the pile head junction part which is one Example of this invention. It is a figure explaining a mode that axial force is transmitted via a pile head junction which is one example of the present invention. It is a figure explaining the reinforcing material of the cover part of the pile head which comprises the pile head junction part which is one Example of this invention. In the structure which has a pile head junction part which is one Example of this invention, it is a figure explaining the relative movement of a pile and a footing when the force of a shear direction is added. It is a figure explaining the shape of the pile head which comprises the pile head junction part in another Example of this invention, Comprising: It is a figure corresponding to FIG. It is a figure explaining the shape of the formwork which comprises the pile head junction part in another Example of this invention, Comprising: It is a figure corresponding to FIG. It is a figure explaining the shape of the formwork which comprises the pile head junction part in another Example of this invention, Comprising: It is a figure corresponding to FIG.

12: Pile 13: Pile head 14: Structure 16: Footing 20: Pile head joint 22: Formwork (frame plate part)
23: Formwork hole (hole)
24: Lid 25: Lid hole 26: Core rebar 28: Pile main bar

Claims (4)

A method for constructing a pile head joint between a pile head of a concrete pile and a structure to be joined to the pile head,
For a pile head having a predetermined curved surface shape in a part of the contact surface with the structure, and the core rebar of the concrete pile protruded in the extending direction of the concrete pile,
While arranging the frame plate portion provided with a hole of a predetermined radius so that the core rebar penetrates the hole,
By constructing the structure by placing concrete so that the frame plate portion becomes the bottom, the peripheral portion of the hole and the pile head can be slidably contacted,
A construction method of a pile head joint characterized by the above. A pile head joint structure that is a joint portion between a pile head of a concrete pile and a structure to be joined to the pile head,
The pile head has a predetermined curved surface shape on a part of the contact surface with the structure,
The concrete pile has a core reinforcing bar provided in the extending direction,
The core reinforcing bar protrudes from the plane portion toward the structure,
The structure has a frame plate at the joint with the pile head,
The frame plate portion is provided with a hole with a predetermined radius, the core rebar is inserted into the structure through the hole, and the peripheral edge portion of the hole and the pile head are slidably contacted,
Pile head joint structure characterized by The pile head has a metal lid that covers the surface of the pile head,
The lid portion has a lid hole portion through which the core rebar is inserted;
The pile head joint structure according to claim 2, wherein: At least one of the lid portion and the frame plate portion is processed to reduce friction in a range where at least the lid portion and the frame plate portion are in contact with each other;
The pile head joint structure according to claim 2 or 3, wherein

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