JP5939178B2 - Pile head coupling structure and pile head coupling method - Google Patents

Description

  The present invention relates to a technique for joining a pile head and a foundation slab. In particular, the present invention relates to a technique suitable for a connecting structure between a high bearing capacity type steel pipe pile and a foundation slab.

In recent years, due to the development of high-bearing-type steel pipe piles such as rotating piles and steel pipe soil cement piles, the load acting on each pile (always during an earthquake) tends to increase. Along with this, it is expected that a large load is also applied to the joint between the pile and the superstructure.
As a conventional pile head coupling structure, for example, there is a pile head coupling structure (referred to as structure A) described in a road bridge specification as shown in FIG. In this structure A, a plurality of intermediately reinforced reinforcing bars protrude from the head of the pile toward the foundation slag, and a tensile force between the pile and the foundation slab is received by the reinforcing reinforcing bars. However, in this structure A, it is difficult to obtain a sufficient strength of the pile head coupling portion relative to the strength of the pile body, and there is a concern that the entire foundation structure becomes unstable due to insufficient strength of the pile head coupling portion.

  Moreover, as a pile head coupling | bonding structure which strengthened the said structure A, as shown in FIG. 19, there exists a structure which carried out the field welding of the reinforcing bar to the pile outer periphery. In this pile head connection structure, an increase in the number of reinforcing bars may result in an overcrowded reinforcement, which may reduce workability and quality reliability. In addition, since the work of welding the reinforcing bar to the steel pipe pile is performed at the construction site, there is a risk that the strength and durability of the welded portion may be impaired due to work in the rain or a difference in welding technology level.

  Furthermore, there is a pile head coupling structure described in Patent Document 1. In this pile head coupling structure, as shown in FIG. 20, a cylindrical outer steel pipe with anchoring bars fixed is arranged around the head of the steel pipe pile, and the pile head, the foundation slab, Are described. At this time, an annular steel plate called a horizontal diaphragm is provided concentrically and integrally with the lower end of the outer steel pipe.

JP 2005-139731 A

However, in the pile head coupling structure described in Patent Document 1, it is necessary to arrange a horizontal diaphragm for load transmission in addition to a cylindrical outer steel pipe and anchored reinforcing bar welding, and it is troublesome to produce an outer steel pipe with a horizontal diaphragm. It takes.
Moreover, since it is necessary to provide a horizontal diaphragm in the shape of an inward flange with respect to a cylindrical outer steel pipe, it is necessary to arrange | position so that a pile center and an outer steel pipe center may become substantially concentric. For this reason, construction takes time. Further, in a plan view, the amount of the outer steel pipe protruding from the pile head in the outer diameter direction is defined by the horizontal diaphragm (see FIG. 21). For this reason, the required covering thickness B is arrange | positioned outside by the clearance gap between a steel pipe pile and an outer steel pipe, and a foundation slab enlarges that much.
This invention is made paying attention to the above points, and it aims at providing the coupling | bonding technique of the pile head and foundation slab which are easy to construct, aiming at the strengthening of the coupling | bonding more.

In order to solve the above problems, one embodiment of the present invention provides:
(1) In a pile head coupling structure in which at least a pile head is composed of a steel pipe and a foundation slab,
The outer shape of the coupling cylinder made of a frustum-shaped steel pipe with the axis facing up and down and the apex on the lower side, and fixed to the coupling cylinder and above the upper end position of the coupling cylinder A plurality of pile head anchoring reinforcing bars,
It is arranged in a state where the pile head of the pile is inserted into the lower opening of the coupling cylinder, and the coupling cylinder among the upper opening of the coupling cylinder and the pile head fixing reinforcing bar Reinforcing bar part located above the upper end position of is embedded in the foundation slab ,
The pile head fixing rebar extending upward is arranged to extend in the same direction as the side surface of the frustum-shaped coupling cylinder .

Next, the second aspect of the present invention is as follows.
(2) For the configuration described in (1) above, for preventing slippage, at least one of the outer peripheral surface of the pile head facing the coupling cylinder and the inner circumferential surface of the coupling cylinder facing the pile. The protrusion is provided.
Next, the third aspect of the present invention is as follows.
(3) With respect to the configuration described in (1) or (2) above, the vertical axis of the coupling cylinder is inclined with respect to a direction parallel to the axis of the pile or the axis of the pile.

Next, a fourth aspect of the present invention is as follows.
(4) After fixing a pile head fixing reinforcing bar beforehand with respect to the coupling cylinder as described in any one of said (1)-(3), lower end opening of the coupling cylinder which has the pile head fixing reinforcement A pile head characterized in that a pile head is arranged in the section and the pile head and the coupling cylinder are coupled by placing a filler between the pile head and the coupling cylinder. A bonding method is provided.
Examples of the filler include concrete, soil cement, and mortar.

According to the present invention, the tensile strength can be improved without providing a horizontal diaphragm by making the outer shape of the coupling cylinder into an upwardly expanding frustum shape. By eliminating the need for a horizontal diaphragm, the degree of freedom of arrangement of the coupling cylinder relative to the pile head is improved.
As a result, it is possible to provide a technique for joining the pile head and the foundation slab, which is easy to construct, although the strength of the joint can be increased. Moreover, it leads to quality improvement because it is easy to install.

It is a figure explaining the pile head coupling | bonding structure which concerns on embodiment based on this invention. It is a figure explaining the construction example which concerns on embodiment based on this invention. It is a figure explaining a load transmission mechanism. It is a figure which shows the example in the case of attaching attachment angle (alpha) to a pile head fixing reinforcement. It is a figure which shows the relationship between angle (alpha) and a stress increment. It is a schematic diagram which shows the transmission force between the cylinder for a coupling | bonding, and a pile head fixing reinforcement. It is a schematic diagram which shows the transmission force between the cylinder for a coupling | bonding and the pile head fixing reinforcement when a pile head fixing reinforcement is arranged in the vertical direction. It is a figure explaining the example at the time of inclining the axis | shaft of the cylinder for a coupling | bonding. It is a typical top view explaining the example at the time of inclining the axis | shaft of the cylinder for a coupling | bonding. It is a figure explaining the construction example of the example at the time of inclining the axis | shaft of the cylinder for a coupling | bonding. It is a figure explaining the example which laid discard concrete. It is a typical top view which shows the example of a reinforcement interference part. It is a figure which shows the example in the case of attaching attachment angle (alpha) to some pile head fixing rebars when the axis | shaft of the cylinder for a coupling | tilt is inclined. It is a figure in the case of changing the direction of reinforcement without bending a pile head fixation reinforcement. It is a figure explaining an Example. It is a figure explaining the example at the time of arranging a pile head fixation reinforcement in the perpendicular direction. It is a figure explaining the example at the time of arranging a pile head fixation reinforcement along the cylinder for connection. It is a figure explaining a prior art example. It is a figure explaining a prior art example. It is a figure explaining a prior art example. It is a figure which shows the required covering thickness B in the case of a prior art example. It is a figure explaining the item of a prior art example.

Next, embodiments of the present invention will be described with reference to the drawings.
(Pile head connection structure)
FIG. 1 is a diagram illustrating a pile head coupling structure according to the present embodiment.
The pile head coupling structure of the present embodiment is a coupling structure for coupling the foundation slab 2 located above the head 1a of the steel pipe pile 1 placed on the ground.
Here, a protrusion 3 for preventing slippage is formed on the pile head of the pile 1 of the present embodiment. The protrusion 3 for preventing the shift is formed so as to protrude laterally (outer diameter direction) from the outer peripheral surface of the pile head. In FIG. 1, an annular protrusion arranged concentrically on the pile head 1 a is illustrated as the protrusion 3 for preventing misalignment.

Moreover, as the pile 1 to which this embodiment is applied, a high-bearing-force type steel pipe pile such as a rotating pile, a steel pipe soil cement pile, or an SC pile can be exemplified.
In addition, the present invention can be applied to the pile 1 having a steel pipe at least at the head 1a of the pile 1. For example, even if it is the pile 1 which attached the cap-shaped steel pipe to the upper end part of a cement pile, this invention is applicable. That is, the preferred pile foundation targeted by the present invention is the steel pipe pile 1, but the pile 1 in which only the upper part (head) of the pile 1 such as an earthquake-resistant cast-in-place pile is formed using a steel pipe (the lower part is only reinforced concrete). It is also possible to apply the present invention to (formation).

(Component parts of pile head connection structure)
As parts constituting the pile head coupling structure of this embodiment, an inverted frustum-shaped coupling cylinder 4 and two or more pile head anchoring reinforcing bars 5 are provided.
The coupling cylinder 4 is formed of a frustum-shaped steel pipe whose outer shape is oriented with the axis L up and down and the apex P side down, that is, the bottom side is up. In addition, the inner peripheral surface shape of the coupling cylinder 4 may not be a frustum shape. The coupling cylinder 4 of the present embodiment will be described by taking as an example a case where the coupling cylinder 4 is configured by a truncated cone-shaped steel pipe whose diameter increases toward the upper side. The cross section of the cone is not limited to a circular shape, and may be employed even if it has another cross sectional shape such as a quadrangle.
The inner diameter of the lower end opening of the coupling cylinder 4 is such that the pile head can be inserted from below.

The inclination of the outer peripheral surface of the coupling cylinder 4 with respect to the vertical axis L is the diameter D of the pile head, and the outer diameter at the lower end surface of the coupling cylinder 4 is “1.05 × D”. It is preferable that the outer diameter at the upper end surface of the cylindrical body 4 is “1.3 × D” or more. The dimension (height) in the axis L direction of the coupling cylinder 4 is described as 2.0 × D. Usually, the height is considered to be set in the range of 1.5 × D to 2.0 × D.
The inclination angle θ of the outer peripheral surface of the coupling cylinder 4 with respect to the vertical axis L is preferably less than 45 degrees. When it is 45 degrees or more, the contribution to the transmission of the tensile force in the vertical direction becomes small. Furthermore, in consideration of the workability of the filler and the pile head fixing reinforcing bar reinforcement, the inclination angle θ is preferably 10 degrees or more.

Next, the pile head fixing rebar 5 will be described.
The pile head fixing reinforcing bar 5 may be a normal building reinforcing bar. The cross section of the pile head fixing rebar 5 is not limited to a circle, and may be a square or the like.
A plurality of pile head fixing rebars 5 are arranged at intervals in the circumferential direction with respect to the outer peripheral surface of the coupling cylinder 4, and the lower portion of each pile head fixing rebar 5 is connected to the coupling cylinder. 4 is fixed by welding or the like. Each pile head fixing rebar 5 is arranged so as to extend along the outer peripheral surface of the coupling cylinder 4 and extend in the same direction as the frustum shape angle (inclination angle of the frustum side surface) formed by the coupling cylinder 4. It is streaked. As described above, the pile head fixing reinforcing bar of the present embodiment has a plurality of pile heads around the apex P of the cone shape by arranging the axis L along the outer peripheral surface of the coupling cylinder 4. The fixing rebar is in a state of extending radially upward obliquely. The pile head fixing rebar 5 may be fixed to the coupling cylinder 4 in advance, or after the coupling cylinder 4 is attached to the pile head, the pile head fixing rebar 5 is attached to the coupling cylinder 4. May be fixed by welding or the like. The site construction is easier when the pile head fixing rebar 5 is fixed to the coupling cylinder 4 in advance. Further, the pile head fixing rebar 5 may be fixed to the inner peripheral surface side of the coupling cylinder 4.

  It should be noted that a part of the plurality of pile head fixing rebars 5 may be set to extend vertically upward with respect to the upper end surface of the coupling cylinder 4, but preferably all the pile head fixing rebars 5. However, it is preferable that the bars are arranged so as to extend in the same direction as the frustum shape angle (inclination angle of the frustum side surface) formed by the coupling cylinder 4.

(Pile head connection method)
As shown in FIG. 2, the coupling cylinder so that the head 1 a of the pile 1 that is previously placed on the ground and is erected on the ground is disposed in the lower end opening of the coupling cylinder 4. 4 is placed on the pile head 1a.
It is assumed that the pile head fixing rebar 5 is previously welded and fixed to the coupling cylinder 4 as described above. In addition, the welding of the pile head fixing rebar 5 may be performed on-site or may be performed in a factory.

  Next, a formwork (not shown) for the foundation slab 2 is installed, and reinforcing bars and beams for the foundation slab 2 are arranged in the formwork (see FIG. 1). At this time, the mold is installed at a position where the upper end surface of the coupling cylinder 4 can be completely embedded in the basic slab 2 or the vertical position of the coupling cylinder 4 is adjusted within an allowable range. Here, FIG. 1 illustrates an example in which the upper part of the connecting cylinder 4 is embedded in the lower part of the in-situ concrete 8, but the upper end surface of the connecting cylinder 4 is on the lower surface of the in-situ concrete 8. It may be in a contact state. In the case where the upper part of the connecting cylinder 4 is embedded in the lower part of the cast-in-place concrete 8, the connection becomes stronger.

Next, cast-in-place concrete 7 and 8 is placed as a filler in the coupling cylinder 4 and the mold. When the concrete 7 and 8 that have been driven are completely cured, the formwork is removed. Abandoned formwork may be used.
The filler to be placed in the coupling cylinder 4 and in the mold may be mortar or soil cement. Alternatively, the concrete 7 or the like may be placed in the coupling cylinder 4 first, and then the concrete 8 or the like may be placed in the mold.

(Effects etc.)
About the fixing structure of the frustum-shaped coupling cylinder 4 and the steel pipe pile 1, a filler such as concrete, mortar, or soil cement is provided between the inner surface of the frustum-shaped coupling cylinder 4 and the outer periphery of the steel pipe pile 1. By driving, the load is transmitted between the displacement preventing projection 3 provided on the pile head 1a of the steel pipe pile 1 and the frustum-shaped coupling cylinder 4 through these materials.

Further, between the frustum-shaped coupling cylinder 4 and the foundation slab 2, as shown in FIG. 3, pile head fixing reinforcing bars 5 fixed to the coupling cylinder 4 are embedded in the concrete of the foundation slab 2. Then, the load is transmitted by the adhesive force between the reinforcing bar and the foundation slab 2 concrete.
Here, by making the coupling cylinder 4 into an inverted cone shape, the load transmission of the tensile force in the vertical direction can be performed through the coupling cylinder 4. As a result, a conventional horizontal diaphragm becomes unnecessary. That is, since the cross-sectional performance of the pile head coupling portion is proportional to the square of the diameter of the coupling cylinder 4, the coupling cylinder 4 is formed into an inverted cone shape, so that the bending moment acting on the pile head is reduced. Resistance force (strength) increases and the "pile head coupling structure" corresponding to the pile head reaction force increase accompanying the increase in strength of the steel pipe pile 1 can be obtained.

In order to increase the load transmission force, as shown in FIG. 2, a protrusion 11 for preventing slippage may be provided on the inner surface of the lower end of the truncated conical cylinder 4.
And in the said pile head coupling | bonding structure, the following effect can be acquired.
The pile head reaction force accompanying the increase in strength of the target steel pipe pile 1 by transmitting the load between the pile 1 and the foundation slab 2 through the coupling cylinder 4 made of an inverted cone-shaped steel pipe. Load transmission corresponding to the increase is possible.

  Further, by making the coupling cylinder 4 an inverted cone-shaped steel pipe, the coupling cylinder 4 can sufficiently transmit a vertical load without providing a conventional horizontal diaphragm. As a result, the construction of the pile head coupling structure is simplified, the construction ease is improved, and the construction time is shortened. In addition, since the horizontal diaphragm for load transmission becomes unnecessary, the manufacturing cost is reduced.

  About the cylinder 4 for a coupling | bonding, the diameter of an upper end part is large compared with the lower end part in which a pile head is inserted. For this reason, when it considers in the reinforcement part of the pile head fixation reinforcement 5 embed | buried in the foundation slab 2, compared with the case where the same number of pile head fixation reinforcement 5 is fixed with respect to the cylindrical outer steel pipe like the past. The space between the pile head fixing reinforcing bars 5 is increased. That is, the reinforcing bar diameter is increased. As a result, the cross-sectional performance (proportional to the square of the diameter) of the pile head joint is improved, so that the resistance (strength) to the bending moment acting on the pile head increases, and the pile head accompanying the increase in strength of the steel pipe pile 1 A “pile head connection structure” corresponding to an increase in reaction force can be obtained.

Further, since the pile head fixing reinforcing bars 5 are arranged in such a manner as to spread radially from the bottom to the top, the interval between the reinforcing bars increases toward the upper side, and the reinforcement of the foundation slab 2 is facilitated. In addition, the part of the pile head fixing reinforcement 5 which protrudes from the upper end of the cylinder 4 for a coupling | bonding may protrude toward the perpendicular direction.
Moreover, since the space | interval between pile head fixing reinforcing bars 5 can be enlarged, the reinforcing bar reinforcement of the horizontal direction arranged in the foundation slab 2 becomes easy.
Here, using a cylindrical outer steel pipe as in the prior art, when trying to ensure the spacing between the pile head anchoring reinforcing bars 5 equivalent to the present embodiment, it is necessary to design the outer steel pipe with a larger diameter accordingly, The portion occupied by the pile head connection structure will be large.

In addition, since a horizontal diaphragm is unnecessary as described above, it is possible to set the inner diameter of the lower end portion of the coupling cylinder 4 to a diameter close to the outer diameter of the pile head. It is also possible to suppress an increase in the pile head coupling structure. Moreover, it is not necessary to arrange the lower end part of the coupling cylinder 4 concentrically with the pile 1.
As described above, by applying the present invention, it is possible to obtain a “pile head connection structure” having high strength, high workability and high quality reliability, and a compact shape of the foundation slab 2.

(About the attachment angle α of the pile head fixing rebar 5 to the outer peripheral surface of the connecting cylinder 4)
Here, in the above description, each pile head fixing rebar 5 is the same as the frustum shape angle (tilt angle of the frustum side surface) formed along the outer peripheral surface of the coupling cylinder 4 and formed by the coupling cylinder 4. The case where the bars are arranged so as to extend in the direction is described.
As shown in FIG. 1, if the pile head fixing rebar 5 is arranged so as to extend in the same direction as the frustum shape angle formed by the coupling cylinder 4, the load acting on the coupling cylinder 4 is only the tensile force. It is. The maximum stress σmax at that time can be expressed by the following equation.
σmax = Tp / (π · Di · t · cosθ)
here,
Tp: Tensile force acting on the pile
Di: Lower diameter of coupling cylinder t: Plate thickness of coupling cylinder θ: Frustum shape angle formed by coupling cylinder.

  On the other hand, as shown in FIG. 4, when the pile head fixing rebar 5 is coupled to the frustum surface of the coupling cylinder 4 with the mounting angle α, the load acting on the coupling cylinder 4 as the mounting angle α is increased. In addition to the tensile force described above, a bending moment is generated. As a result, the total stress acting on the coupling cylinder 4 is increased, and therefore, for example, it is necessary to increase the thickness of the four plates of the coupling cylinder.

FIG. 5 shows the relationship between the mounting angle α and the stress increase caused by the acting bending moment. As can be seen from FIG. 5, when the mounting angle α is 0 ° to 15 ° or less, the pace of stress increase does not change much, and the stress increment at 15 ° is about 26%, but when the mounting angle α exceeds 15 °, The pace of stress increase tends to increase gradually.
Thus, in order to reduce the total stress acting on the coupling cylinder 4, the bar head fixing rebar 5 is arranged as much as possible so as to extend in the same direction as the frustum shape angle formed by the coupling cylinder 4. However, in order to avoid variations in rebar mounting accuracy and interference between rebars that spread radially, when an attachment angle α formed between the pile head fixing rebar 5 and the frustum surface of the coupling cylinder 4 occurs, It is desirable to be within ± 15 °.

Here, as shown in FIG. 6, the pile head fixing rebar 5 is arranged to extend in the same direction as the frustum shape angle formed by the connecting cylinder 4, and as shown in FIG. 7, the pile head fixing The case where the reinforcing bars 5 are arranged so as to extend vertically upward from the upper end portion of the coupling cylinder 4 will be compared.
As shown in FIG. 6, when the pile head fixing rebar 5 is arranged to extend in the same direction as the frustum shape angle formed by the coupling cylinder 4, the load acting on the coupling cylinder as described above. Is the tensile force only. The maximum stress σmax at that time is “Tp / (π · Di · t · cos θ)” as described above.

On the other hand, as shown in FIG. 7, when the pile head fixing reinforcing bar 5 is bent and arranged vertically upward, it has a large attachment angle with respect to the frustum surface of the coupling cylinder, and thus acts on the coupling cylinder. In addition to the tensile force, the load to be generated generates an excessive bending moment. As a result, the total stress acting on the coupling cylinder increases, so that it is necessary to increase the plate thickness of the coupling cylinder as compared with the structure of the present invention. Further, in the pile head coupling structure as shown in FIG. 7, in order to fix the pile head fixing rebar 5, the fixing bar needs to be largely bent in advance at the upper end portion of the coupling cylinder 4, which increases the processing cost. At the same time, there is a concern about early failure due to a decrease in elongation performance due to plastic working. On the other hand, there is no such concern when arranging the pile head fixing reinforcing bars 5 so as to extend in the same direction as the frustum shape angle formed by the coupling cylinder 4.
From this point of view, it is not preferable to arrange all the plurality of pile head fixing rebars 5 at the upper end portion of the coupling cylinder 4 so as to be arranged vertically upward. In order to avoid interference with other reinforcing bars, it may be appropriately arranged to arrange the bars vertically upward.

(Modification)
Here, it is not necessary to arrange the axis L of the coupling cylinder 4 so as to be coaxial with the pile 1. For example, in order to avoid interference with the reinforcement of the foundation slab 2, the vertical axis L of the coupling cylinder 4 is appropriately tilted from the vertical direction or the axis L of the pile 1 or a direction parallel to the axis L. Also good. Here, when the axis L of the pile 1 is in the vertical direction, the vertical direction is the reference. However, when the axis L of the pile 1 is tilted, the axis L for the pile 1 is used as a reference. The axis L of the cylinder 4 is set.

Moreover, it is necessary to ensure the required covering thickness B set beforehand on the outer peripheral surface side of the foundation slab 2 on the basis of the coupling cylinder 4 and the pile head fixing rebar 5. At this time, when the coupling cylinder 4 close to the outer circumferential surface of the foundation slab 2 is arranged coaxially with the pile 1, the dimension from the position of the pile 1 to the outer circumferential surface (slab 2 edge) of the foundation slab 2 is large. Become.
At this time, as shown in FIG. 8, by tilting the vertical axis L of the coupling cylinder 4 from the vertical direction H toward the direction away from the edge of the nearest slab 2, in the plan view, in the vicinity of the pile head The cover thickness from the position can be reduced. That is, as the vertical axis L of the coupling cylinder 4 is set so that the outer surface of the coupling cylinder 4 near the edge of the nearest slab 2 approaches the vertical direction (direction parallel to the edge of the slab 2), The covering thickness from the position near the pile head can be set small.

FIG. 9 is a schematic plan view showing an example in which the vertical axis L of each coupling cylinder 4 is inclined in a direction away from the nearest edge of the slab 2. In addition, the vertical axis L of the coupling cylinder 4 that couples the piles 1 arranged at the corners of the foundation slab 2 is inclined in a direction away from the two slab 2 edges.
By doing in this way, the overhang | projection to the basic | foundation slab 2 edge direction of the cylinder 4 for coupling | bonding is relieve | moderated, and it becomes possible to design the shape of the basic | foundation slab 2 compactly by that much.
FIG. 10 illustrates the arrangement of the coupling cylinder 4 and the relationship with the basic slab 2 in this case.
In addition, in order to stabilize the fixed position when the frustoconical coupling cylinder 4 is tilted, as shown in FIG.
Moreover, you may utilize the cylinder 4 for a connection of frustum shape as a formwork at the time of concrete slab 2 concrete placement.

Moreover, about manufacture of the cylinder 4 for a truncated cone shape, you may manufacture by a spiral manufacturing method from a flat plate, You may manufacture by plate bending process, casting, and forging.
Here, in the structure in which the upper side of the vertical axis L of the coupling cylinder 4 as shown in FIG. 8 is inclined from the vertical direction H toward the direction away from the edge of the nearest slab 2, the interval between adjacent piles When the length of the reinforcing bar is small or the length of the reinforcing bar at the head of the pile is long, adjacent reinforcing bars may interfere with each other and the construction may be difficult. FIG. 12 is a schematic plan view showing the above case. The dashed-dotted line in FIG. 12 has shown the front-end | tip position of a pile head fixed reinforcement, and the part which these overlapped becomes a reinforcement interference part.

  In order to eliminate the reinforcing bar interference part, at least a part of the pile head fixing reinforcing bar 5 located in the reinforcing bar interference part is attached so as to have an angle with respect to the frustum surface of the coupling cylinder 4 as shown in FIG. It is possible. In this case, as described above, a bending moment is generated, and the total stress acting on the coupling cylinder 4 is increased. To prevent this, as shown in FIG. You may employ | adopt the structure which attaches a curvature gradually in the other side, and changes a direction, without attaching an angle to the attachment part to the body 4. FIG. That is, the pile head fixing rebar 5 may be curved without forming a sharp bent portion.

If the structure which has equivalent intensity | strength is designed based on this embodiment with respect to the structural example of the pile head coupling | bonding structure A as described in the above-mentioned road bridge specification shown in FIG. 22, it will become the structure shown in FIG.
In the case of the structure shown in FIG. 15, the amount of reinforcing bars can be reduced to about 45% compared to structure A, and the interval between adjacent reinforcing bars can be increased to about four times. Thus, the pile head connection structure based on this embodiment turns into a structure excellent in cost efficiency and workability with respect to the pile head connection structure A as described in a road bridge specification.
In addition, the head 3a of the steel pipe pile 1 is provided with a protrusion 3 for preventing slippage for load transmission.

As shown in FIG. 16, when a structure having the same strength as the structure example of the pile head coupling structure when all the pile head fixing reinforcing bars 5 are bent and vertically arranged is arranged, the structure shown in FIG. Become.
In the case of the structure shown in FIG. 16, the maximum stress acting on the connecting cylinder by the tensile force and the bending moment is determined by Chang et al. (“An Asymptotic solution of Conical Shells of Constant Thickness”, AIAA, Vol. 5, No. 5). 11, pp. 2028-2033.) Since θ = 30 ° and approximately σ _M = 0.6σ _N , σmax = σ _M + σ _N = 1.6 × σ _N = 1.6 × Tp / (π · Di · (where σ _{M is the} stress due to the bending moment, σ _{N is the} stress due to the tensile force, Tp is the tensile force acting on the pile, Di is the lower diameter of the coupling cylinder, and t is the bond. Plate thickness of the cylinder, θ: frustum-shaped angle formed by the coupling cylinder). From this equation, the required thickness t of the connecting cylinder is calculated to be 19 mm.

On the other hand, in the case of the present embodiment shown in FIG. 17, the maximum stress degree is 12 mm when the required plate thickness t of the coupling cylinder is calculated from σmax = σ _N = Tp / (π · Di · t · cos θ), Compared to the structure shown in FIG. 16, the plate thickness is reduced by 37%. Thus, it can be seen that it is preferable to arrange the pile head anchoring reinforcing bars 5 so as to extend in the same direction as the frustum shape angle formed by the coupling cylinder 4 rather than arranging the pile head fixing reinforcing bars 5 vertically upward.

DESCRIPTION OF SYMBOLS 1 Pile 2 Foundation slab 3 Protrusion 4 Coupling cylinder 5 Pile head anchoring reinforcement 7, 8 Concrete L Vertical axis P Vertex θ Inclination angle

Claims (4)

In the pile head connection structure where the pile head and the foundation slab are combined at least with the pile head,
The outer shape of the coupling cylinder made of a frustum-shaped steel pipe with the axis facing up and down and the apex on the lower side, and fixed to the coupling cylinder and above the upper end position of the coupling cylinder A plurality of pile head anchoring reinforcing bars,
It is arranged in a state where the pile head of the pile is inserted into the lower opening of the coupling cylinder, and the coupling cylinder among the upper opening of the coupling cylinder and the pile head fixing reinforcing bar Reinforcing bar part located above the upper end position of is embedded in the foundation slab ,
The pile head fixing structure, wherein the pile head fixing rebar extending upward is arranged to extend in the same direction as a side surface of the frustum-shaped coupling cylinder .   2. A protrusion for preventing displacement is provided on at least one of an outer peripheral surface of the pile head facing the coupling cylinder and an inner peripheral surface of the coupling cylinder facing the pile. The pile head connection structure described in 1.   The pile head coupling structure according to claim 1 or 2, wherein the vertical axis of the coupling cylinder is inclined with respect to a direction parallel to the pile axis or the pile axis.   A pile head anchoring reinforcing bar is fixed in advance to the coupling cylinder according to any one of claims 1 to 3, and then piled in a lower end opening of the coupling cylinder having the pile head anchoring reinforcing bar. A pile head coupling method, wherein a head is arranged and a pile head is coupled with a coupling cylinder by placing a filler between the pile head and the coupling cylinder.

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