Pile head structure and pile construction method

Abstract

To provide a pile head structure and a pile construction method which facilitate adjusting the horizontal and vertical positions of a core iron material even without joining a pillar to the core iron material.SOLUTION: A pile head structure includes a steel pipe 22 that is provided on the top of a cast-in-place pile (pile 20) and joined to foundation concrete (footing 14) of a structure, a core iron material (core steel frame 24) with the lower part embedded in concrete inside the steel pipe 22 and the upper part embedded in the foundation concrete, and a positioning member 44 that positions and fixes the core iron material in the central part of the steel pipe 22.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pile head structure and a pile construction method.

Background Art

[0002] Patent Document 1 below describes a joint structure between a steel column and a pile in which a connecting member joined to the steel column is fixed to the pile. According to such a configuration, a pulling force is transmitted between the steel column and the pile ground through the connecting member.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] While arranging a connecting member such as that in Patent Document 1 at the center of the pile, if the reinforcing cage is not fixed to a foundation such as a footing, the pile head becomes semi-rigid with respect to the foundation. As a result, the bending moment acting on the pile head is reduced, and in some cases, the cross-sectional dimensions of the pile and the foundation cross-sectional dimensions can be made smaller.

[0005] In order to reduce the bending moment acting on the pile head, it is necessary to accurately position the core steel material as a connecting member at the center of the pile. Also, in order to transmit the axial force between the footing and the pile, it is necessary to accurately position the core steel material in the height direction as well. However, for example, when using a core steel frame to which a steel column is not joined, the position of the core steel frame cannot be adjusted by adjusting the erection method of the steel column. Therefore, it is difficult to adjust the horizontal position and the position in the height direction of the core steel material.

[0006] In consideration of the above facts, an object of the present invention is to provide a pile head structure and a pile construction method in which the horizontal position and the position in the height direction of the core steel material can be easily adjusted without joining a column to the core steel material.

Means for Solving the Problem

[0007] The pile head structure according to claim 1 includes a steel pipe provided at the pile head of the driven pile and joined to the foundation concrete of the structure, a core reinforcing member with the lower part embedded in the concrete inside the steel pipe and the upper part embedded in the foundation concrete, and a positioning member for positioning and fixing the core reinforcing member at the center of the steel pipe.

[0008] In the pile head structure according to claim 1, the lower part of the core reinforcing member is embedded in the concrete inside the steel pipe provided at the pile head. And the upper part of this core reinforcing member is embedded in the foundation concrete of the structure. Thereby, it is possible to resist the pulling force acting on the driven pile from the structure during an earthquake. On the other hand, the steel pipe at the pile head is joined to the foundation concrete of the structure. Thereby, the vertical load of the structure can be supported by the pile.

[0009] Also, the core reinforcing member is positioned and fixed at the center of the steel pipe by the positioning member. Therefore, compared with the configuration in which reinforcing bars are arranged at the peripheral part of the pile, the bending moment acting on the pile head becomes smaller, so that the pile head becomes a semi-rigid joint with respect to the foundation concrete. And by the bending moment acting on the pile head becoming smaller compared with the case of a rigid joint, it is possible to rationally design the cross-sectional shape of the pile.

[0010] Furthermore, since the core reinforcing member is positioned by the positioning member, the horizontal position and the position in the height direction of the core reinforcing member can be adjusted without joining the columns.

[0011] The pile head structure according to claim 2 is the pile head structure according to claim 1, wherein the core reinforcing member is a steel structural member, and the positioning member is provided at two locations vertically, including an upper member fixed to the side surface of the steel structural member and the upper end portion of the steel pipe above, and a lower member fixed to the side surface of the steel structural member below and not fixed to the inner peripheral wall of the steel pipe.

[0012] In the pile head structure of claim 2, positioning members are provided at two locations vertically. Thereby, the core iron material can be arranged along the axial direction of the steel pipe. Further, if the upper member is fixed to the steel pipe in a state where the core iron material is arranged along the axial direction of the steel pipe, the vertical accuracy can be maintained without fixing the lower member to the steel pipe.

[0013] The pile head structure of claim 3 is the pile head structure according to claim 2, wherein the positioning member is formed to include an H-shaped steel welded to the steel frame member and protruding laterally, the upper member is fixed to the H-shaped steel, and includes a hanging member that is hooked on the upper end portion of the steel pipe to position in the vertical direction, and a fixing member that is fixed to the H-shaped steel and fixed inside the steel pipe.

[0014] In the pile head structure of claim 3, the upper member in the positioning member includes a hanging member that is hooked on the steel pipe to position in the vertical direction. Thereby, the load of the core steel frame can be deposited on the steel pipe without continuously lifting the core steel frame with a crane. Further, the upper member is fixed inside the steel pipe by the fixing member. Thereby, since the fixed portion is covered with concrete, it is difficult to corrode.

[0015] The construction method of the pile of claim 4 includes a step of lifting a steel pipe fixed to a steel bar cage and the upper end portion of the steel bar cage and inserting it into a pile hole, a step of hooking a positioning member fixed to a core iron material on the upper end portion of the steel pipe while holding the upper end portion of the steel pipe above the opening end of the pile hole to position the core iron material at the central portion of the steel pipe, a step of fixing the positioning member and the steel pipe, a step of inserting a tremie pipe into the steel pipe and placing concrete from above the upper end of the core iron material to below, a step of excavating the ground to expose the core iron material above the bedding surface, and a step of placing foundation concrete around the core iron material to embed the upper portion of the core iron material in the foundation concrete and joining the steel pipe to the foundation concrete.

[0016] In the method for driving a pile according to claim 4, the lower part of the core steel material is embedded in the concrete inside the steel pipe provided at the pile head. And the upper part of this core steel material is embedded in the foundation concrete of the structure. Thereby, it is possible to resist the pulling force acting on the displacement pile from the structure during an earthquake. On the other hand, the steel pipe at the pile head is joined to the foundation concrete of the structure. Thereby, the vertical load of the structure can be supported by the pile.

[0017] Also, the core steel material is positioned and fixed at the center of the steel pipe by the positioning member. For this reason, compared with the configuration in which reinforcing bars are arranged at the peripheral part of the pile, the bending moment acting on the pile head becomes smaller, so that the pile head becomes a semi-rigid joint with respect to the foundation concrete. And since the bending moment acting on the pile head becomes smaller compared with the case of a rigid joint, it is possible to rationally design the cross-sectional shape of the pile.

[0018] Furthermore, since the core steel material is positioned by the positioning member, the horizontal position and the height direction position of the core steel material can be adjusted without joining the columns.

Advantages of the Invention

[0019] According to the present invention, even without joining the columns to the core steel material, it is easy to adjust the horizontal position and the height direction position of the core steel material.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0021] Hereinafter, a pile head structure and a pile construction method according to an embodiment of the present invention will be described with reference to the drawings. Components denoted by the same reference numerals in the respective drawings mean the same components. However, unless otherwise specified in the specification, each component is not limited to one, and a plurality of them may exist.

[0022] Also, descriptions of overlapping configurations and reference numerals in the respective drawings may be omitted. Note that the present disclosure is not limited to the following embodiments, and appropriate changes can be made, such as omitting configurations, replacing them with different configurations, and using combinations of one embodiment and various modification examples, within the scope of the object of the present disclosure.

[0023] In each drawing, the directions indicated by the arrows X and Y are along the horizontal plane and are perpendicular to each other. Also, the direction indicated by the arrow Z is along the vertical direction (up and down direction). In each figure, the directions indicated by the arrows X, Y, and Z shall be the same as each other.

[0024] <Pile head structure> (Building) The pile head structure according to an embodiment of the present invention is applied to the building 10 shown in FIG. 1. The building 10 is a building having a basement floor and is an example of a structure in the present invention. The building 10 is supported by the site-cast piles 20 (hereinafter referred to as "piles 20"). The pile head of the pile 20 is fixed to the footing 14 to which the foundation beam 12 is connected. The footing 14 is an example of the foundation concrete in the present invention.

[0025] A column 16 is fixed to the footing 14. Beams 18 of each floor of the building 10 are spanned across the column 16. Among the structural surfaces surrounded by the column 16 and the beam 18, a vibration damping material (or seismic member) 30 is arranged on a part of the structural surfaces.

[0026] In FIG. 1, the vibration damping material 30 is illustrated as a wall-type viscous shear damper, but this vibration damping material (or seismic member) 30 may also be an oil damper (viscoelastic damper) or a steel damper (hysteretic damper) that is diagonally spanned within the structural surface surrounded by the column 16 and the beam 18, or a seismic member such as a seismic wall.

[0027] The pile head structure of the present invention is applied, as an example, to the piles 20 on the outer periphery of the building 10. Also, this pile head structure is also applied to the piles 20 provided directly below the column 16 on which a tensile axial force acts due to the action of the vibration damping material 30. That is, it is preferable to apply the pile head structure of the present invention to the piles 20 among the piles 20 that support the building 10 and to which a tensile axial force is likely to act during an earthquake.

[0028] (Pile head structure) The pile head portion of the pile 20 to which the pile head structure according to an embodiment of the present invention is applied includes a steel pipe 22 and a core steel frame unit 40, as shown in FIG. 2(A).

[0029] The steel pipe 22 is provided at the pile head of the pile 20 and joined to the footing 14 of the building 10. Specifically, the upper end of the steel pipe 22 is embedded in the lower end of the footing 14. Also, a steel bar cage 24 is fixed to the lower end of the steel pipe 22.

[0030] The core steel frame unit 40 includes a core steel frame 42 and a positioning member 44. The core steel frame 42 is an example of the core steel material in the present invention, and is an H-shaped steel with its lower part embedded in the concrete inside the steel pipe 22 and its upper part embedded in the footing 14. A plurality of stud bolts 42A are welded to the core steel frame 42. The stud bolts 42A are provided on both the inside of the steel pipe 22 and the inside of the footing 14.

[0031] The positioning member 44 is a member that positions and fixes the core steel frame 42 at the central part of the steel pipe 22. Also, the positioning member 44 is provided at two locations vertically, and includes an upper member 44A above and a lower member 44B below. The upper member 44A and the lower member 44B are formed using H-shaped steel.

[0032] The end face of the upper member 44A is welded to the side surface of the core steel frame 42 and protrudes laterally, and is fixed to the upper end of the steel pipe 22 as will be described later. On the other hand, the end face of the lower member 44B is welded to the side surface of the core steel frame 42 and protrudes laterally, and is not fixed to the inner peripheral wall of the steel pipe 22.

[0033] As shown in FIG. 2(B), two upper members 44A are provided, and are welded to both flanges of the core steel frame 42 respectively. The two upper members 44A are arranged in a straight line and have the same length respectively. Also, as shown in FIG. 2(A), two lower members 44B are provided, and are welded to both flanges of the core steel frame 42 respectively. The two lower members 44B are arranged directly below the upper members 44A respectively and have the same length respectively.

[0034] (Positioning structure) As shown in FIGS. 3(A) to 3(C), the upper member 44A includes a hook member 46 and a fixing member 48. The hook member 46 is provided at two locations on the flange of the upper member 44A.

[0035] The hook member 46 is an “L-shaped” steel material including a horizontal portion 46A welded to the upper flange of the upper member 44A and a vertical portion 46B extending downward from the tip of the horizontal portion 46A at a position spaced apart from the end face of the upper member 44A. In FIGS. 3(A) to 3(C), the welding bead B is shown as required.

[0036] A steel pipe 22 is disposed between the end face of the upper member 44A and the vertical portion 46B of the hook member 46. The horizontal portion 46A of the hook member 46 is disposed in contact with the upper end face of the steel pipe 22. Thereby, the height positions of the upper member 44A and the core steel frame 42 (see FIG. 2) with respect to the steel pipe 22 are positioned.

[0037] Also, as shown in FIG. 3(C), the vertical portion 46B of the hook member 46 and the steel pipe 22 are fixed by welding. Thereby, the planar positions of the upper member 44A and the core steel frame 42 (see FIG. 2) with respect to the steel pipe 22 are positioned.

[0038] The fixing member 48 includes a first fixing member 48A, a second fixing member 48B, and a temporary fixing bolt 48C. The first fixing member 48A is welded to the lower flange of the upper member 44A, and the second fixing member 48B is welded to the inner peripheral surface of the steel pipe 22. Also, the first fixing member 48A and the second fixing member 48B are welded to each other.

[0039] By these weldings, the lower flange of the upper member 44A is welded to the inner peripheral surface of the steel pipe 22. That is, the upper member 44A is fixed to the steel pipe 22 at two locations in the height direction by the hook member 46 and the fixing member 48. Thereby, the vertical straightness of the core steel frame unit 40 with respect to the front-rear direction (Y direction) of the paper surface in FIG. 2 can be ensured.

[0040] On the one hand, as described above, the lower member 44B is welded to the side surface of the core steel frame 42, but is not fixed to the inner peripheral wall of the steel pipe 22. However, since the upper member 44A and the lower member 44B are arranged at intervals in the vertical direction, the vertical straightness of the core steel frame unit 40 with respect to the horizontal direction (X direction) of the paper surface of FIG. 2 can be ensured.

[0041] Note that the temporary fixing bolt 48C shown in FIG. 3(A) is a bolt for holding the first fixing member 48A and the second fixing member 48B in a state of sandwiching the lower flange of the upper member 44A before these welds.

[0042] (Configuration inside the footing) As shown in FIG. 2(A), main reinforcing bars of the foundation beam 12 are arranged inside the footing 14. Among the main reinforcing bars, the upper end bars 12A are arranged above the core steel frame 42 and are used as continuous bars.

[0043] On the other hand, in the case of the lower end bars 12B, the reinforcing bars that interfere with the core steel frame 42 when used as continuous bars have their ends arranged inside the footing 14. Fixing tools 12C are fixed to the ends of the lower end bars 12B arranged inside the footing 14.

[0044] As a result, as shown in FIG. 4(A), the lower end bars 12B can also be passed through the center portion in the width direction of the foundation beam 12, so that the beam width of the foundation beam 12 can be reduced. On the other hand, when all of the lower end bars 12B are used as continuous bars as shown in FIG. 4(B), the beam width becomes larger compared to the case shown in FIG. 4(A). Note that the present invention can also include the arrangement of the lower end bars 12B as shown in FIG. 4(B).

[0045] <Construction method of pile> To construct the pile 20, first, as shown in FIG. 5(A), the ground G is drilled. Next, as shown in FIG. 5(B), the reinforcing cage 24 and the steel pipe 22 fixed to the upper end portion of the reinforcing cage 24 are lifted and inserted into the pile hole H.

[0046] At this time, as shown in Fig. 5(C), hold the steel pipe 22 above the open end of the pile hole H. To hold the steel pipe 22, temporarily fix a fixing rib 22A to the upper end of the steel pipe 22. Then, hook the fixing rib 22A on the gantry 20A arranged at the open end of the pile hole.

[0047] Then, with the steel pipe 22 held above the open end of the pile hole H, lift the core steel frame unit 40 and insert it into the steel pipe 22. Then, as shown in Fig. 5(D), position the core steel frame 42 at the central part of the steel pipe 22.

[0048] At this time, as shown in Fig. 7(A), hook a hooking member 46 fixed to the positioning member 44 (upper member 44A) of the core steel frame unit 40 on the upper end of the steel pipe 22. Then, as shown in Fig. 7(B), adjust the planar position of the core steel frame 42 with the hooking member 46 hooked on the upper end of the steel pipe 22.

[0049] After adjusting the planar position of the core steel frame 42, as shown in Fig. 7(C), weld the fixing member 48 to the upper member 44A and the steel pipe 22. Also, weld the hooking member 46 to the steel pipe 22. Thereby, the core steel frame 42 is positioned at the central part of the steel pipe 22. Also, the height position of the core steel frame 42 with respect to the steel pipe 22 is positioned.

[0050] Next, as shown in Fig. 5(E), insert the integrated core steel frame unit 40, steel pipe 22, and steel bar cage 24 to a predetermined depth of the pile hole H.

[0051] Then, as shown in Fig. 6(A), insert two tremie pipes P into the steel pipe 22 and place concrete into the pile hole H. At this time, as shown in Fig. 6(B), place concrete down to below the upper end of the core steel frame 42. Thereby, the pile 20 is constructed.

[0052] Next, as shown in Fig. 6(C), the ground G is excavated to expose the core steel frame 42 above the flooring surface. Finally, as shown in Fig. 6(D), after placing steel bars around the core steel frame 42, the concrete of the footing 14 is placed to embed the upper part of the core steel frame 42 in the footing 14. Also, the steel pipe 22 is joined to the footing 14.

[0053] <Function and Effect> In the pile head structure according to the embodiment of the present invention, as shown in Fig. 2(A), the lower part of the core steel frame 42 is embedded in the concrete inside the steel pipe 22 provided at the pile head. And the upper part of this core steel frame 42 is embedded in the footing 14.

[0054] Thereby, as shown by the arrow N1 in Fig. 1, it is possible to resist the pulling force acting on the pile 20 from the building 10 during an earthquake. On the other hand, as shown in Fig. 2(A), the steel pipe 22 at the pile head is joined to the footing 14. Thereby, as shown by the arrow N2 in Fig. 1, the vertical load of the building 10 and the axial force acting from the column 16 during an earthquake can be supported by the pile 20.

[0055] Also, the core steel frame 42 is positioned and fixed at the center of the steel pipe 22 by the positioning member 44. And there are no reinforcing bars arranged at the peripheral part of the pile 20. For this reason, compared with a configuration in which the core steel frame 42 is arranged eccentrically from the center of the steel pipe 22 or a configuration in which reinforcing bars are arranged at the peripheral part of the pile 20 instead of the core steel frame 42, the bending moment acting on the pile head of the pile 20 becomes smaller. Thereby, the pile head becomes a semi-rigid joint with respect to the footing 14. And since the bending moment acting on the pile head becomes smaller compared with the case of a rigid joint, it is possible to rationally design the cross-sectional shape of the pile 20.

[0056] Furthermore, since the core steel frame 42 is positioned by the positioning member 44, the horizontal position and the position in the height direction of the core steel frame 42 can be adjusted without joining a structural column or the like.

[0057] Also, in the pile head structure according to the embodiment of the present invention, the positioning members 44 are provided at two locations vertically (that is, the upper member 44A and the lower member 44B). Thereby, the core steel frame 42 can be arranged along the axial direction of the steel pipe 22.

[0058] Moreover, since the upper member 44A is fixed to the steel pipe 22 with the core steel frame 42 arranged along the axial direction of the steel pipe 22, the vertical accuracy can be maintained without fixing the lower member 44B to the steel pipe 22.

[0059] Also, in the pile head structure according to the embodiment of the present invention, as shown in FIGS. 3(A) to 3(C), the upper member 44A of the positioning member 44 is provided with a hooking member 46 that hooks on the upper end of the steel pipe 22 to position the vertical direction. Thereby, even if the core steel frame unit 40 is not continuously lifted by a crane, the load of the core steel frame unit 40 can be deposited on the steel pipe 22.

[0060] Moreover, the upper member 44A is also fixed inside the steel pipe 22 by a fixing member 48. Thereby, since the fixed part is covered with concrete, it is difficult to corrode.

[0061] <Other Embodiments> In the above embodiment, the upper member 44A and the lower member 44B of the H-shaped steel are used as the positioning members 44, but the embodiment of the present invention is not limited to this. For example, the lower member 44B may be omitted. When the lower member 44B is omitted, after visually confirming the vertical accuracy of the core steel frame 42, the hooking member 46 and the fixing member 48 shown in FIGS. 3(A) to 3(C) are welded to the steel pipe 22.

[0062] Also, as the positioning member, for example, deformed reinforcing bars may be used instead of the upper member 44A and the lower member 44B of the H-shaped steel. When deformed reinforcing bars are used as the positioning member, for example, as the core steel material, deformed reinforcing bars may be used instead of the core steel frame 42. The core reinforcing bars are formed by arranging a plurality of deformed reinforcing bars along the vertical direction.

[0063] Also, in the above-described embodiment, an "L-shaped" hooking member 46 is used for the upper member 44A, but the embodiments of the present invention are not limited to this. For example, a steel plate may be used as the hooking member and welded to the upper flange of the upper member 44A. The steel plate may be arranged in the in-plane direction along the upper flange of the upper member 44A, or may be arranged perpendicular to the upper flange of the upper member 44A. In this way, the hooking member may be any member that protrudes laterally from the upper member 44A and is hooked to the steel pipe 22.

[0064] Also, in the above-described embodiment, the fixing member 48 is used, but the embodiments of the present invention are not limited to this. For example, the fixing member 48 may be omitted. When the fixing member 48 is omitted, after visually confirming the vertical accuracy of the core steel frame 42, the hooking member 46 is welded to the steel pipe 22. Thus, the present invention can be implemented in various modes.

Explanation of Reference Numerals

[0065] 10 Building (Structure) 14 Footing (Foundation Concrete) 20 Pile 22 Steel Pipe 42 Core Steel Frame 44 Positioning Member 44A Upper Member 44B Lower Member 46 Hooking Member 48 Fixing Member G Ground H Pile Hole P Tremie Pipe

Claims

1. A steel pipe that is attached to the head of the cast-in-place pile and joined to the foundation concrete of the structure; A core iron material whose lower portion is embedded in the concrete in the steel pipe and whose upper portion is embedded in the foundation concrete; a positioning member for positioning and fixing the core iron material to the center of the steel pipe; A pile head structure equipped with

2. The core iron material is a steel frame material, The positioning members are provided at two locations, one above the other, An upper member fixed to a side surface of the steel frame and an upper end portion of the steel pipe at an upper portion; A lower member fixed to a side surface of the steel frame at a lower portion and not fixed to an inner peripheral wall of the steel pipe; Equipped with The pile head structure according to claim 1.

3. The positioning member is formed by including an H-shaped steel welded to the steel frame and protruding laterally, The upper member is A hook member fixed to the H-shaped steel and hooked onto the upper end of the steel pipe to position the steel pipe in the up-down direction; A fixing member fixed to the H-shaped steel and fixed to the inside of the steel pipe; Equipped with The pile head structure according to claim 2.

4. A step of lifting the reinforcing bar cage and the steel pipe fixed to the upper end of the reinforcing bar cage and inserting them into a pile hole; A step of hooking a positioning member fixed to a core iron material onto the upper end of the steel pipe while holding the upper end of the steel pipe above the open end of the pile hole, thereby positioning the core iron material to the center of the steel pipe; a step of fixing the positioning member and the steel pipe; a step of inserting a tremie pipe into the steel pipe and pouring concrete below an upper end of the core iron material; excavating the ground to expose the core iron material above a bedding surface; A step of pouring foundation concrete around the core iron material, embedding an upper portion of the core iron material in the foundation concrete, and joining the steel pipe to the foundation concrete; A pile construction method comprising the steps of:

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