JP2000220152A - Pile head construction for steel pipe pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a joint portion between a pile head and a foundation and reduce assembling work on the job site by jointing a base plate having anchoring steel bars with the diameter larger than that of the pile diameter at the pile head to the pile head portion of the steel pipe pile. SOLUTION: An inner peripheral surface of a ring-shaped base plate 11 is fixed by groove welding to the outer peripheral surface 10 of a pile head portion 3 of a steel pipe pile 1 embedded in earth 2, and the lower ends of a plurality of anchoring steel bars 6 arranged in a circular shape are fixed to the upper surface of the base plate 11. When the steel pipe pile 1 has a rotary wing 18, the anchoring steel bars 6 and the base plate 11 are attached to the pile head portion 3 of the steel pile 1 in factory and processed and the pile can be embedded to the earth 2 while rotating the steel pipe pile 1 on the job site. If the steel pipe pile 1 is of a drive type, the base plate 11 and the pile head cap 14 are fixed by groove welding 13, 16 to the pile head portion 3 above the ground after driving the steel pipe pile 1, and the welding work can be performed smoothly if the ground is excavated near the pile head portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention simplifies the joint structure between a pile head and a foundation, uses factory-produced products, reduces on-site connection (joining), and secures a pile head anchoring rebar and a foundation. The present invention relates to a pile head structure of a steel pipe pile which enables smooth connection with a reinforcing bar.

[0002]

2. Description of the Related Art In a steel pipe pile which is driven into the ground and buried, a pile head joining structure for joining a pile head and a foundation (beam) is made as shown in FIG. 14 to FIG. 16 or FIG. I have. 14 to 16 show a method in which a bending moment is applied to a virtual reinforced concrete section by a reinforcing bar welded to the outer surface of a pile head.

In this conventional example, a steel pipe pile 1 is driven into the underground 2, a pile head cap 5 is welded to a top end surface 4 of a pile head 3 projecting upward from the ground 2, and a pile head is mounted. Part 3
The lower ends of the plurality of anchoring bars 6 are directly applied to the outer periphery of
Secured by welding on site. The pile head 3 and the anchoring bar 6 are buried in a concrete foundation (footing) 8. In the design, the virtual cross section 7 in the foundation in FIGS. 14 and 15 is designed with a virtual cross section of +100 mm from the outer periphery of the pile, so that the virtual cross section 7 is reduced. Therefore virtual section 7
Stiffness on the tensile side often decreases.

[0004] In the above-mentioned pile head structure, when the diameter (L) of the pile head 3 of the steel pipe pile 1 is 900φ, forty forty D29 anchoring reinforcing bars 6 are directly welded to the outer periphery of the pile head 3. F
C (concrete strength) = 300 kg / cm2 is achieved. As described later with reference to FIG. 6, when a bending moment and an axial force act on the steel pipe pile 1 due to the horizontal force at the time of an earthquake, the steel pipes need to have a large number (40) of the anchoring bars 6 as described later. A tensile force and a compressive force act on the pile 1, and a tensile force and a compressive force also act on the anchoring reinforcing bar 6 directly welded to the steel pipe pile 1. This is because an anchoring bar for tensile force is required.

In the above-mentioned pile head structure, FIG.
As shown in the figure, the anchoring rebar 6 welded to the outer periphery of the pile head 3
Are arranged at regular intervals in a circular shape, and some of the large number of anchoring reinforcing bars 6 are woven in a mesh shape on a concrete foundation (footing) 8 as shown in FIG. Of basic reinforcing bar 9 (intersection of mesh-like reference line)
24, it interferes with (collides with) the rebar, and there is a problem that the layout work is not smooth.

The above problem also occurs in the pile head structure shown in FIG. FIG. 17 shows a pile head obtained by arranging anchoring reinforcing bars 6 in a circular shape at equal intervals inside a steel pipe pile head 3, inserting a fixing bar 6 a using a band reinforcing bar 6 a, and placing a concrete filling 20. It is a part structure. Also in the pile head structure of FIG. 17, similarly to the case of FIG. 16, a large number of anchoring reinforcing bars 6 arranged in a circle at equal intervals inside the pile head 3 are meshed in the concrete foundation 8. Rebars that interfere with the knitted and laid base rebars 9 may appear, making it difficult to perform the rebar work smoothly.

[0007]

As described above, the conventional steel pipe pile head structure has the following disadvantages. In the structure in which the anchoring reinforcing bar 6 is directly welded to the outer periphery of the pile head, the arrangement of the anchoring reinforcing bar 6 becomes dense, and the welding operation and inspection of the anchoring bar 6 take time. Since the rigidity of the conventional pile head is often not assured, the deformation of the pile head during an actual earthquake or the like may be larger than the value calculated by fixing the pile head. Further, the anchoring reinforcing bars 6 welded to the outer periphery of the pile head 3 at equal intervals, or the anchoring reinforcing bars 6 are arranged at equal intervals in a circular shape inside the steel pipe pile head 3 and fixed using the band reinforcing bar 6a. Regardless of the pile head structure in which the object is inserted and the filling concrete 20 is cast, each anchoring reinforcing bar 6 interferes with the base reinforcing bar 9, it takes time to assemble the reinforcing bar, and the operation does not go smoothly. . However, as described above, there is a problem that the factors (1) to (2) are intertwined, and the construction and construction of the pile head structure of the steel pipe piles take time and the construction cost increases. An object of the present invention is to provide a pile head structure of a steel pipe pile which has solved the above-mentioned drawbacks.

[0008]

In order to achieve the above object, a pile head structure for a steel pipe pile according to the present invention is configured as follows. The first invention is characterized in that a base plate with a fixing rebar larger than the pile head pile diameter is joined to the pile head of the steel pipe pile. According to a second aspect of the present invention, the top end face of the pile head is not cut, and is located above the upper surface of the base plate having a predetermined thickness. The inner diameter of the base plate is welded to the outer periphery of the pile head. It is characterized by having done. A third invention is characterized in that a pile head cap is provided inside the pile head, and an outer periphery of the pile head cap and an inner periphery of the pile head are welded. The fourth invention is characterized in that the pile head cap is a flat plate or a plate having a predetermined thickness and has a conical cross section that is convex downward. A fifth aspect of the present invention is characterized in that a groove is formed on a pile head, and a base plate with a fixing reinforcing bar serving also as a pile head cap is joined thereto, or bolted to the pile head. According to a sixth aspect of the present invention, a large number of anchoring reinforcing bars arranged in a ring are arranged on respective meshes (intersections of mesh reference lines) of the base reinforcing bars arranged in a mesh.
The distance from the annular center is changed for each anchoring bar, so that the anchoring bars are fixed to the base plate with unequal intervals. A seventh invention is characterized in that the fixing rebars are arranged such that the virtual lines connecting the plurality of fixing rebars arranged at the unequal intervals form a polygon. An eighth invention is characterized in that the outer shape of the base plate is provided in a shape similar to a polygon formed by imaginary lines connecting the plurality of fixing rebars. According to a ninth aspect of the present invention, a large number of anchoring reinforcing bars arranged annularly at the pile head of a steel pipe pile are arranged on respective meshes (mesh-like reference line intersections) of the base reinforcing bars arranged in a mesh shape. By changing the distance from the annular center for each anchoring bar, the intervals between the anchoring bars are unevenly arranged. The tenth invention is characterized in that the fixing rebars are arranged such that imaginary lines connecting many fixing rebars arranged at unequal intervals form a polygon.

According to the present invention, by welding a base plate with anchoring bars larger than the diameter of the pile head to the outer periphery of the pile head of the steel pipe pile, it is possible to impart the same seismic resistance as before with less anchoring bars than before. The joint between the head and the foundation can be simplified, and the connection (joining) on site can be reduced.

Further, in the present invention, by providing the anchoring bars rising from the pile head in an arrangement that avoids interference with the base reinforcing bars arranged in a mesh shape, the work for avoiding interference with the base beam reinforcing bars can be omitted. The performance is improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the first embodiment of FIGS. 1 and 2,
Outer peripheral surface 10 of pile head 3 of steel pipe pile 1 buried underground 2
In addition, the inner peripheral surface of the ring-shaped base plate 11 having a large thickness is fixed by a groove welding 13 via a backing metal 12. The lower ends of a plurality of fixing reinforcing bars 6 provided in a circular arrangement on the upper surface of the base plate 11 are fixed by screw connection or welding (an example of welding is shown in the figure). Inside the pile head 3, the outer periphery of the pile head cap 14 in which the pile head cap 14 is disposed and the inner periphery of the pile head are fixed to each other by groove welding 16 via a backing metal 15. The top end face 17 of the pile head 3 protrudes slightly above the upper surfaces of the base plate 11 and the pile head 3.
Since no welding or the like is performed, no processing of the cut surface is required, and no special processing is required. Further, as in the related art, a groove may be formed on the pile head and welding may be performed.

When the steel pipe pile 1 is a rotary pile having a rotary blade 18 at the lower end thereof, the anchoring reinforcing bar 6 and the base plate 11 are attached to the pile head of the steel pipe pile 1 at a factory.
It can be processed and buried in the ground 2 while rotating the steel pipe pile 1 on site. When the steel pipe pile 1 is a driving pile, the base plate 11 and the pile head cap are provided on the outer circumference and the inner circumference of the pile head 3 on the ground after driving the steel pipe pile 1 into the ground at a predetermined depth. The groove 14 is fixed by groove welding 13 and 16. However, in the welding work of the base plate 11, if the ground around the pile head is slightly excavated and welded, the welding work can be performed smoothly. After the base plate 11 with the anchoring rebar 6 is welded to the pile head 3 in this way, the foundation concrete 8 is cast so that these are buried.

FIGS. 3 and 4 show a second embodiment. In this example, instead of the flat pile head cap 14 in the first embodiment, a pile head cap having a predetermined thickness and a downwardly convex conical cross section is used. An example in which a cone head 21 is fixed to a pile head by a groove welding 22 is shown. The cone head 21 is formed into a conical shape by cutting a flat steel plate having a predetermined thickness into a sector shape, welding both end edges thereof, expanding at an inclination angle of approximately 60 °, and having an opening 23 at the tip. . An outer peripheral portion of the cone head 21 is engaged with an inner edge of an upper end of the pile head 3, and a groove weld 22 is formed on a groove formed on the top end surface 17.
And fix it.

By forming the cone head 21 in such a conical cross-sectional shape, a pile head cap having improved strength, lighter weight, and a higher strength can be constituted with less steel material.

FIG. 5 shows a third embodiment. In this example, by excavating the ground around the pile head 3 of the steel pipe pile 1 driven into the ground 2, the pile head 3 Is protruding. Further, a groove is formed by cutting the top end face 17 of the pile head 3, and a groove welding 16 a is applied thereto by utilizing the space of the excavation recess 19, so that the pile head top end face 17 is formed. A base plate 11a having a diameter larger than the diameter of the steel pipe pile 1 and having a fixing reinforcing bar 6 serving also as a pile head cap is fixed. Instead of the groove welding 16a, the base plate 11a may be fixed to the pile head top end face 17 by bolt connection (however, not shown).

In the steel pipe pile head structure according to the first, second and third embodiments of the present invention, the diameter of the steel pipe pile 1 is 900φ, and the base plates 11 and 11a are 80 mm thick and have an outer diameter of 1 mm.
It is provided at 300φ. Accordingly, the base plates 11 and 11a are moved from the outer periphery of the steel pipe pile 1
The fixing bar 6 is projected outward with a width of 00 mm, and is welded to the upper surfaces of the protruding base plates 11 and 11a. Further, according to the head structure of the steel pipe pile of the present invention, 90
In the steel pipe pile 1 of 0φ, the anchoring reinforcing steel 6 of D29 is provided on the upper surfaces of the base plates 11 and 11a projecting outward from the pile head 3
(Concrete strength) = by welding 28
240 / cm2 could be achieved.

That is, according to each of the above-described embodiments of the present invention, when the steel pipe pile 1 having the same diameter as that of the conventional steel pipe pile 1 is disposed on the pile head 3 and the reinforcing steel 6 of the same type as that of the conventional steel pipe, the reinforcing steel of D29 is provided. The following benefits are achieved. (A) Anchorage bar 6
Can be reduced from 12 to 40 by changing the number from 40 to 28. (B) The concrete strength (FC) becomes 300 → 240 kg / cm 2 in the case of the same ultimate strength,
g / cm2.

The above (A) and (B) can be understood from FIG. Figure (A) shows the conventional pile head structure, Figure (B)
In the pile head structure of the present invention, FIG. 4 shows a state of force acting when a bending moment M (tm) during an earthquake and an axial force N (t) act on the pile head. In the structure of the conventional example, the steel pipe pile diameter is 900φ, M (tm): 400 tm, N (t): 100
In the case of 0t, the anchoring reinforcing bar 6 is directly welded to the outer periphery of the pile head 3. When the pile head is simply considered to be a square with the outer shape L of the pile head as one side, e: eccentric distance e = 400/1000 = 0.4, e / L = 0.4 / 0.
9 = 0.44 ≧ 1/6 = 0.16. According to the above equation, in the conventional structure, as shown in FIG. 6A, a compressive force indicated by a downward arrow and a tensile force indicated by an upward arrow act on the pile head 3 during an earthquake. Therefore, in order to balance the compressive force and the tensile force, a rebar for tensile force is required in addition to the rebar for compressive force.

In the present invention, when the base plate 11b is a square having a side length of L1 and L1 is 2.4 m, the above equation becomes e / L1 = 0.4 / 2.4 = 0.16 = 1.
/ 6, and no tensile force acts on the pile head 3. Therefore,
It can be seen that no tension rebar is required and the number of anchoring rebars 6 can be reduced as compared to the conventional example.

FIG. 7 is a graph showing the mutual relationship between the ultimate strength (bending moment) M (tm) of the present invention and the conventional structure in the pile head on the horizontal axis and the axial force N (t) on the vertical axis. Have been. The illustrated solid line indicates the change curve in the pile head structure of the present invention, and the illustrated dotted line indicates the change curve in the conventional structure. As can be seen from the figure, in the present invention, although the number of fixing reinforcing bars is reduced by 12 compared to the conventional example, it is possible to exhibit almost the same proof stress as the conventional one. In the illustrated example, the fixing rebar 6 is shown as an example of the fixing rebar, but the present invention can also be implemented by welding a dowel bar or a stud to the base plate 11.

8 to 10 show a fourth embodiment of the present invention. In Embodiments 1 to 3 described above, since a large number of fixing reinforcing bars 6 are arranged in a circle at equal intervals, the concrete foundation 8
In order to avoid the interference with the base reinforcing bar 9 woven in a mesh shape and arranged in the inside, it is necessary to carry out the work.
This problem has been solved. That is, the fourth embodiment
In this case, a large number of anchoring reinforcing bars 6 fixed to the base plate 11 in a ring shape are arranged from the center of the circle so as to be arranged on the respective meshes (mesh reference line intersections) 24 of the base reinforcing bars 9 arranged in a mesh. By changing the distance for each fixing reinforcing bar, a large number of fixing reinforcing bars are fixed to the base plate 11 with unequal intervals.

In the illustrated example, the fixing rebars 6 are arranged such that a virtual line 25 connecting a number of fixing rebars 6 arranged at unequal intervals forms a polygon. In addition, the fixing rebar 6
In order to avoid interference with the base reinforcing bar 9, a method of arranging in a plurality of rows can be adopted (however, not shown).

FIGS. 11 and 12 show Embodiments 5 and 6 of the present invention. In Embodiment 4 described above, the outer shape of the base plate 11 to which a number of fixing reinforcing bars 6 are fixed at irregular intervals (polygon) is circular, whereas in Embodiments 5 and 6, the base plates 11c and 11d The outer shape,
It is approximated to the shape of a polygonal virtual line 25 connecting the fixing rebars 6. That is, the outer shape of the base plates 11c and 11d is an octagon with rectangular corners cut off or a rectangle with the corners left, so that the fixing reinforcing bars 6 in a polygonal arrangement are well balanced with the base plates 11c and 11d. Can be placed.

FIG. 13 shows a seventh embodiment of the present invention. In the seventh embodiment, a number of anchoring reinforcing bars 6 that are annularly disposed in the pile head 3 of the steel pipe pile through the placement of the filling concrete 20 are respectively meshed with the basic reinforcing bars 9 arranged in a mesh shape. (Mesh reference line intersection)
By changing the distance from the annular center for each anchoring bar, the intervals between the anchoring bars are unevenly arranged. In other words, as shown in the drawing, a large number of fixing rebars are arranged such that imaginary lines connecting them form a polygon (octagon).

[0025]

According to the pile head structure of the steel pipe pile according to the present invention, the same strength as that of the conventional steel pipe can be maintained even if the pile-reinforcing steel bar is reduced, so that the reinforcement of the foundation and the pillar are easily arranged.
Further, by appropriately increasing the width of the base plate to be welded to the pile head, a design that does not generate a tensile force can be performed.
This eliminates the need for anchoring rebar for tensile force, prevents the displacement of rebars and studs for horizontal force buffering during an earthquake, simplifies the joint between the pile head and the foundation, and uses many factory-produced products. This has the effect of reducing the connection (joining) of the components. Further, a structure capable of securing the continuity of rigidity of the pile head joint is possible.

In the present invention, the anchoring bars rising from the diameter of the pile head are arranged so as to easily avoid interference with reinforcing bars such as a base reinforcing bar, a foundation beam reinforcing bar, a column reinforcing bar, and a floor reinforcing bar arranged in a mesh shape. Therefore, the work of improving the workability by eliminating the conventional trouble of avoiding the interference with these various types of reinforcing steel is improved, and as a total effect of the present invention achieved by combining them, the construction of the pile head structure of the steel pipe pile is performed. Can be performed quickly and easily, and the construction cost can be reduced.

[Brief description of the drawings]

1 is a plan view of a pile head shown in FIG. 2;

FIG. 2 is a side sectional view and a partially enlarged view of a steel pipe pile head according to Embodiment 1 of the present invention.

FIG. 3 is a plan view of a pile head shown in FIG. 4;

FIG. 4 is a side sectional view and a partially enlarged view of a steel pipe pile head according to Embodiment 2 of the present invention.

FIG. 5 is a side sectional view of a steel pipe pile head according to Embodiment 3 of the present invention.

6 (A) and 6 (B) are explanatory diagrams showing the state of action of a bending moment and an axial force acting on a pile head according to a conventional example and the present invention during an earthquake.

FIG. 7 is a graph showing the relationship between the bending moment acting on the pile head and the axial force in the structures of the conventional example and the first to third embodiments of the present invention.

FIG. 8 is a plan view showing a state where a fixing rebar is fixed to a base plate as a fourth embodiment.

FIG. 9 is a plan view showing a state in which a number of fixing reinforcing bars are connected by virtual lines in FIG.

FIG. 10 is a plan view showing a state in which a large number of anchoring reinforcing bars and basic reinforcing bars arranged in a mesh form are joined together in FIG.

FIG. 11 is a plan view showing an octagonal base plate to which a fixing rebar is fixed as Embodiment 5;

FIG. 12 is a plan view showing a base plate having a rectangular outer shape to which a fixing rebar is fixed as Embodiment 6;

13A and 13B show a seventh embodiment, in which FIG. 13A is a longitudinal side view of the inside of a steel pipe pile head in which an anchoring bar is annularly arranged via middle-filled concrete, and FIG. Plan view of the
(C) is a top view of the state of connection between the anchoring reinforcing bar and the mesh of the basic reinforcing bar arranged in a mesh shape.

FIG. 14 is a plan view of the pile head of FIG. 15;

FIG. 15 is a side sectional view of a first example of a conventional steel pipe pile head.

16 (A) is a side view of the pile head shown in FIG. 15,
(B) is a plan view of the same figure (A), (C) is an explanatory plan view showing a state of connection between the fixing rebar of the same (B) and a rebar in a mesh shape buried in the foundation.

FIG. 17 is a side sectional view of a second example of the conventional steel pipe pile head.
(B) is a plan view of the same figure (A), (C) is an explanatory plan view showing a state of connection between the fixing rebar of the same (B) and a rebar in a mesh shape buried in the foundation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steel pipe pile 2 underground 3 pile head 4 top end face 5 pile head cap 6 anchored reinforcing bar 6a band reinforcing bar 7 virtual section 8 concrete foundation 9 foundation reinforcing bar 10 outer peripheral surface 11, 11a, 11b, 11c base plate 12 backing metal 13 groove Welding 14 Pile head cap 15 Backing metal 16, 16a Groove welding 17 Top end surface 18 Rotor blade 19 Excavation recess 20 Filling concrete 21 Cone head 22 Groove welding 23 Opening 24 Mesh (mesh-shaped reference line intersection) 25 Virtual line

Claims (10)

[Claims] 1. A pile head structure for a steel pipe pile, wherein a base plate with an anchoring bar larger than the pile head pile diameter is fixed to the pile head of the steel pipe pile. 2. A top end face of the pile head is not treated with a cut surface, and is located above an upper surface of the base plate having a predetermined thickness, and an inner diameter portion of the base plate and an outer periphery of the pile head are welded. The pile head structure of a steel pipe pile according to claim 1, wherein: 3. The pile head of a steel pipe pile according to claim 2, wherein a pile head cap is disposed inside the pile head, and an outer periphery of the pile head cap and an inner periphery of the pile head are welded. Construction. 4. The pile head structure for a steel pipe pile according to claim 3, wherein said pile head cap is made of a flat plate or a plate having a predetermined thickness and has a downwardly convex conical sectional shape. 5. The pile head structure for a steel pipe pile according to claim 1, wherein a top end surface of the pile head is cut to form a groove, and a base plate with a fixing bar serving also as a pile head cap is welded or bolted. 6. The fixed reinforcing bars are arranged at a distance from the center of the ring so that the plurality of anchoring bars arranged in a ring are arranged at the respective meshes (intersection points of the mesh-like reference lines) of the base reinforcing bars arranged in a mesh shape. The pile head structure of a steel pipe pile according to any one of claims 1 to 5, wherein the distance between the anchoring reinforcing bars is made unequal to be fixed to the base plate by changing every time. 7. The pile of steel pipe piles according to claim 6, wherein the anchoring reinforcing bars are arranged such that imaginary lines connecting the plurality of anchoring bars arranged at the unequal intervals form a polygon. Head structure. 8. A pile head structure for a steel pipe pile according to claim 7, wherein the outer shape of said base plate is provided in a shape similar to a polygon formed by imaginary lines connecting said plurality of anchoring bars. . 9. A plurality of anchoring reinforcing bars arranged annularly on a pile head of a steel pipe pile so as to be arranged on respective meshes (intersections of mesh reference lines) of basic reinforcing bars arranged in a mesh shape. By changing the distance from the center for each anchoring bar,
A pile head structure for steel pipe piles, wherein the spacing between the anchoring bars is uneven. 10. The pile of steel pipe piles according to claim 9, wherein the anchoring reinforcing bars are arranged such that imaginary lines connecting the plurality of anchoring bars arranged at the unequal intervals form a polygon. Head structure.