JP6505291B2 - Design method of pile head joint and calculation method of allowable bending moment - Google Patents

Description

  The present disclosure relates to a method of designing a pile head joint and a method of calculating an allowable bending moment.

  The pile foundation supporting the superstructure generally has a plurality of piles and a foundation concrete portion such as a pile cap or footing provided so as to surround the upper end (pile head) of the pile. In order to strengthen the connection between the pile head and the foundation concrete part, for example, as disclosed in Patent Document 1, a joint member and reinforcing bars are used. The pile head, the joint member, the reinforcing bars and the foundation concrete part constitute a pile head joint.

More specifically, in the pile head joint portion disclosed in Patent Document 1, a plurality of joint members are attached to the outer peripheral surface of the pile head at intervals in the circumferential direction. The joint member has a lower plate portion and an upper plate portion mutually spaced apart in the axial direction of the pile head, and the screw portion of the reinforcing bar is coupled to the lower plate portion of the joint member. The shaft portion of the reinforcing bar extends through the insertion portion of the upper plate portion of the joint member and protrudes upward from the end face of the pile head.
In the pile head joint portion disclosed in Patent Document 1, even if the reinforcement portion is formed with a screw portion by screwing the upper concrete portion by pushing the upper plate portion upward, the pile head and the foundation are disclosed. It is possible to effectively reinforce the joint of the concrete part.

JP 2015-34458 A

As a result of investigations by the present inventors, in the pile head joint portion disclosed in Patent Document 1, depending on the presence or absence of a crack in the base concrete portion and the presence or absence of yield in the upper plate portion of the joint member, It turned out that it is necessary to calculate the allowable bending moment separately. There is no description at all in Patent Document 1 about the necessity of such cases.
If the allowable bending moment of the pile head joint can be accurately understood by dividing the case into a pile head, joint members, reinforcement bars and foundation concrete so that the bending moment generated in the pile head can be reliably resisted. While being able to determine the specification of a part, it can suppress that a specification becomes excessive. As a result, by separately calculating the allowable bending moment of the pile head joint, it is possible to secure a sufficient allowable bending moment at low cost.

  In view of the above-described circumstances, an object of at least one embodiment of the present invention is to attach a joint member having a lower side projection and an upper side projection which are mutually separated in the axial direction of the pile head to the outer peripheral surface of the pile head Realizes a sufficient amount of allowable bending moment at a low-cost specification at the pile head joint where the foundation concrete part adheres to the shaft part of the reinforcing bar in which the screw part is connected to the lower side projection part It is an object of the present invention to provide a method of designing a possible pile head joint and a method of calculating an allowable bending moment.

(1) A method of designing a pile head joint according to at least one embodiment of the present invention,
With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The shaft portion of the reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head and protrudes upward from the end face of the pile head ,
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that a crack occurs between the part of the foundation concrete part surrounding the part,
While considering the tensile yield strength of the shaft portion of the reinforcing bar, the allowable bending moment is calculated by disregarding the resistance acting on the base concrete portion from the joint member.

  According to the above configuration (1), when assuming that a crack occurs in the base concrete portion, the tensile yield strength of the shaft portion of the reinforcing bar is taken into consideration, while the resistance acting on the base concrete portion from the joint member is ignored. By calculating the allowable bending moment, the allowable bending moment can be accurately calculated. As a result, according to the above configuration (1), it is possible to realize a pile head joint having a sufficiently large allowable bending moment with a low-cost specification.

(2) A method of designing a pile head joint according to at least one embodiment of the present invention,
With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that no cracks occur between the part of the foundation concrete part surrounding the part,
The allowable bending moment is calculated in consideration of the tensile yield strength of the screw portion of the reinforcing bar and the resistance acting on the base concrete portion from the joint member.

  According to the above configuration (2), when it is assumed that no crack occurs in the base concrete portion, the tensile yield strength of the screw portion of the reinforcing bar is taken into consideration, and the resistance acting on the base concrete portion from the joint member is taken into account Then, the allowable bending moment can be accurately calculated by calculating the allowable bending moment. As a result, according to the above configuration (2), it is possible to realize a pile head joint having a sufficiently large allowable bending moment with a low-cost specification.

(3) A method of designing a pile head joint according to at least one embodiment of the present invention,
With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion continuous with the lower end side of the shaft portion and having a cross-sectional area smaller than that of the shaft portion;
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation process,
A first allowable bending moment as the allowable bending moment is calculated in consideration of the tensile yield strength of the screw portion of the reinforcing bar and the resistance acting on the base concrete portion from the joint member. Bending moment calculation process,
A second allowable bending moment is calculated as the allowable bending moment while ignoring the resistance acting on the base concrete portion from the joint member while taking into consideration the tensile yield strength of the shaft portion of the reinforcing bar. Bending moment calculation process,
An allowable bending moment selecting step of comparing the first allowable bending moment and the second allowable bending moment and selecting the smaller one of the first allowable bending moment and the second allowable bending moment as the allowable bending moment; Including.

  According to the above configuration (3), by selecting the smaller one of the first allowable bending moment and the second allowable bending moment as the allowable bending moment, safety can be obtained regardless of the occurrence of cracks in the base concrete portion. In anticipation, it is possible to realize a pile head joint having a sufficiently large allowable bending moment with a low cost specification.

(4) In some embodiments, in the above configuration (3),
In the allowable bending moment selection step, when the yield strength of the upper projection is smaller than the difference between the tensile yield strength of the shaft and the tensile yield strength of the screw, the first allowable bending moment is the allowable bending. Selected as a moment.

  According to the above configuration (4), when the yield strength of the upper projection is smaller than the difference between the tensile yield strength of the shaft of the reinforcing bar and the tensile yield strength of the screw, the first allowable bending moment is the allowable bending moment Selected as That is, if the yield strength of the upper projection is smaller than the difference between the tensile yield strength of the shaft of the reinforcing bar and the tensile yield strength of the screw, the upper projection yields and the first allowable bending moment Is determined to be small, and the first allowable bending moment is selected as the allowable bending moment. Thus, according to the above configuration (4), the allowable bending moment can be accurately calculated in anticipation of safety, and a pile head joint having an allowable bending moment of a sufficient size is realized with a low-cost specification It is possible.

(5) In some embodiments, in any one of the above configurations (1) to (4)
In the allowable bending moment calculation step,
The resistance bending moment of the reinforcing bars protruding upward from the end of the pile head and the foundation concrete part surrounding the reinforcing bars is assumed to be the bending moment that is imposed by the virtual RC section including the end face of the pile head,
The diameter of the pile head is Dp,
Let D be the diameter of the virtual RC section,
Assuming that the length of the foundation concrete portion adhering to the shaft portion of the reinforcing bar is Le between the lower projection and the upper end of the upper projection in the axial direction of the pile head as follows:
Dp + Le ≦ D ≦ Dp + 2Le
The diameter D of the virtual RC cross section is set and calculated so as to satisfy the relationship represented by

According to the above configuration (5), the resistance bending moment of the reinforcing bars projecting upward from the end of the pile head and the foundation concrete portion surrounding the reinforcing bars is a virtual RC cross section including the end face of the pile head Assuming a bending moment to bear, the following equation:
Dp + Le ≦ D ≦ Dp + 2Le
Since the diameter D of the virtual RC cross section is set so as to satisfy the relationship expressed by equation (4), the size of the virtual RC cross section diameter can be set larger than in the prior art. The larger the virtual RC cross-sectional diameter, the smaller the stress acting on the foundation concrete part and the pile head, and the larger the allowable bending moment can be calculated. As a result, according to the above configuration (5), it is possible to realize a pile head joint having a sufficiently large allowable bending moment with a low-cost specification.

(6) The allowable bending moment calculation method for a pile head joint according to at least one embodiment of the present invention,
With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The shaft portion of the reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head and protrudes upward from the end face of the pile head ,
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that a crack occurs between the part of the foundation concrete part surrounding the part,
While considering the tensile yield strength of the shaft portion of the reinforcing bar, the allowable bending moment is calculated by disregarding the resistance acting on the base concrete portion from the joint member.

  According to the above configuration (6), when assuming that a crack occurs in the base concrete portion, the tensile yield strength of the shaft portion of the reinforcing bar is taken into consideration, while the resistance acting on the base concrete portion from the joint member is ignored. By calculating the allowable bending moment, the allowable bending moment can be accurately calculated. As a result, according to the above configuration (6), it is possible to realize a pile head joint having a sufficiently large allowable bending moment with a low-cost specification.

(7) The allowable bending moment calculation method for a pile head joint according to at least one embodiment of the present invention,
With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that no cracks occur between the part of the foundation concrete part surrounding the part,
The allowable bending moment is calculated in consideration of the tensile yield strength of the screw portion of the reinforcing bar and the resistance acting on the base concrete portion from the joint member.

  According to the above configuration (7), when assuming that no cracks occur in the base concrete portion, the tensile yield strength of the screw portion of the reinforcing bar is considered, and the resistance acting on the base concrete portion from the joint member is taken into consideration Then, the allowable bending moment can be accurately calculated by calculating the allowable bending moment. As a result, according to the above configuration (7), it is possible to realize a pile head joint having a sufficiently large allowable bending moment with a low-cost specification.

(8) The allowable bending moment calculation method for a pile head joint according to at least one embodiment of the present invention,
With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion continuous with the lower end side of the shaft portion and having a cross-sectional area smaller than that of the shaft portion;
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation process,
A first allowable bending moment as the allowable bending moment is calculated in consideration of the tensile yield strength of the screw portion of the reinforcing bar and the resistance acting on the base concrete portion from the joint member. Bending moment calculation process,
A second allowable bending moment is calculated as the allowable bending moment while ignoring the resistance acting on the base concrete portion from the joint member while taking into consideration the tensile yield strength of the shaft portion of the reinforcing bar. Bending moment calculation process,
An allowable bending moment selecting step of comparing the first allowable bending moment and the second allowable bending moment and selecting the smaller one of the first allowable bending moment and the second allowable bending moment as the allowable bending moment; Including.

  According to the above configuration (8), by selecting the smaller one of the first allowable bending moment and the second allowable bending moment as the allowable bending moment, safety can be obtained regardless of the occurrence of cracks in the base concrete portion. In anticipation, it is possible to realize a pile head joint having a sufficiently large allowable bending moment with a low cost specification.

  According to at least one embodiment of the present invention, a joint member having a lower projection and an upper projection spaced apart from each other in the axial direction of the pile head is attached to the outer peripheral surface of the pile head, said lower projection In pile head joints where the foundation concrete part is attached to the shaft of the deformed rebar with the screw part connected to the pile head, the pile head joint which can realize a sufficient amount of allowable bending moment with a low-cost specification And a method of calculating an allowable bending moment are provided.

It is a figure which shows the schematic structure of a structure. It is a figure for demonstrating a pile head junction part. It is a figure which shows the pile head in FIG. 2, a joining member, a reinforcement bar, and an anchor body roughly, a left half is a side view, and a right half is sectional drawing. It is a figure which shows a joining member schematically, (a) is a front view, (b) is a side view, (c) is a top view, and (d) is a bottom view. It is a side view which shows a reinforcing bar schematically. It is sectional drawing which shows roughly a pile head, a joining member, and a part of reinforcement bar. It is a top view which shows roughly a part of pile head and a joining member. It is a flowchart which shows roughly the procedure of the design method of the pile head junction part which concerns on 1st Embodiment. It is a figure for demonstrating the resistance mechanism model for calculating an allowable bending moment, (a) is mechanism I, (b) is mechanism II, and (c) is a figure for demonstrating mechanism III. It is a figure for demonstrating the reason which can consider the tensile yield strength of the axial part of a reinforcement in the state B which the crack has generate | occur | produced. It is a figure for demonstrating the load-bearing increase of the foundation concrete part by the bearing pressure effect in a pile head junction part. It is a figure for demonstrating the yield strength increase of the foundation concrete part by the bearing pressure effect in the eccentric compression state in a pile head joint part. It is a figure which shows roughly the horizontal loading test device of a pile head junction part. It is a graph which shows the application pattern of the horizontal loading force made to act on a pile-head junction part by the horizontal loading test device of FIG. It is the photograph which went around the foundation concrete part of a pile head joint part after the horizontal loading test using a horizontal loading test device, and photographed the internal condition of the foundation concrete part. It is the photograph which went around the foundation concrete part of a pile head joint part after the horizontal loading test using a horizontal loading test device, and photographed the internal condition of the foundation concrete part. It is the photograph which went around the foundation concrete part of a pile head joint part after the horizontal loading test using a horizontal loading test device, and photographed the internal condition of the foundation concrete part. It is the photograph which went around the foundation concrete part of a pile head joint part after the horizontal loading test using a horizontal loading test device, and photographed the internal condition of the foundation concrete part. It is a figure for demonstrating that the virtual RC cross-sectional diameter D was set from the generation | occurrence | production condition of the crack in a foundation concrete part. It is a figure for demonstrating the symbol in [Equation 1]-[Equation 3]. It is a figure for demonstrating the symbol in [Equation 4]. In the case of the state A in which a crack does not generate | occur | produce, it is a figure for demonstrating that the determination position of reinforcement cross-section strength differs from the case of the state B in which a crack has generate | occur | produced. It is a flow chart which shows a rough procedure of an allowable bending moment calculation process in a design method of a pile head connection concerning a 3rd embodiment. It is a flowchart which shows the rough procedure of an allowable bending moment selection process in the case of being Cc> = Tby-Tsy. It is a flow chart which shows a rough procedure of specification propriety determination process in a design method of a pile head connection concerning a 4th embodiment. It is a figure for demonstrating the symbol in [Equation 5] and [Equation 6]. It is a graph which shows the distribution in the direction of an axis of the pile head of the force which acts on a reinforcement in the case of the state B which the crack has generate | occur | produced. It is a graph which shows distribution in the direction of an axis of a pile head of force which acts on a reinforcement in the case of the state A which a crack does not generate. It is a flow chart which shows a rough procedure of a design method of a pile head connection concerning a 5th embodiment. It is a flow chart which shows a rough procedure of a design method of a pile head connection concerning a 6th embodiment. It is a flow chart which shows a rough procedure of a method of designing a pile head joint according to a seventh embodiment and a method of manufacturing a pile head joint according to an eighth embodiment. It is a figure for demonstrating the pile arrangement | positioning used for pile stress integrated analysis. It is a graph which shows the analysis result of a pile stress integral analysis, and is a graph which shows the NM curve of pile P1 at the time of N value = 3.0. It is a graph which shows the analysis result of a pile stress integral analysis, and is a graph which shows the NM curve of pile P1 at the time of N value = 1.0. It is a graph which shows the analysis result of pile stress integral analysis, and is a graph which shows the NM curve of pile P2 at the time of N value = 1.0. It is sectional drawing which shows roughly a pile head of another pile head junction which can be designed with the design method of the pile head junction which concerns on 1st Embodiment, a joining member, a reinforcement, and a part of partition member. It is a figure which shows a partition member roughly, (a) is a front view, (b) is a side view, and (c) is a top view. It is a top view which shows a pile head, a joining member, and a partition member roughly. It is a figure which expands and shows a part of FIG. It is a figure for demonstrating the effect of a partition member. It is a figure showing roughly a pile head of other pile head joints which can be designed by a design method of a pile head joint concerning a 1st embodiment, a joint member, reinforcement bars, and a part of partition member, and a left half Is a side view and the right half is a sectional view. It is a top view which shows a pile head, a joining member, and a partition member roughly. It is a figure which shows schematic structure of a partition member, Comprising: (a) is a top view, (b) is a longitudinal cross-sectional view.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, but are merely illustrative. Absent.
For example, a representation representing a relative or absolute arrangement such as “in a direction”, “along a direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” is strictly Not only does it represent such an arrangement, but also represents a state of relative displacement with an angle or distance that allows the same function to be obtained.
For example, expressions that indicate that things such as "identical", "equal" and "homogeneous" are equal states not only represent strictly equal states, but also have tolerances or differences with which the same function can be obtained. It also represents the existing state.
For example, expressions representing shapes such as quadrilateral shapes and cylindrical shapes not only represent shapes such as rectangular shapes and cylindrical shapes in a geometrically strict sense, but also uneven portions and chamfers within the range where the same effect can be obtained. The shape including a part etc. shall also be expressed.
On the other hand, the expressions "comprising", "having", "having", "including" or "having" one component are not exclusive expressions excluding the presence of other components.

  Hereinafter, although the design method and manufacturing method of the pile head joint part which concern on embodiment of this invention are demonstrated, an example of the pile head joint part of design object is demonstrated first as the premise.

[Composition of a pile head joint]
FIG. 1 is a view showing a schematic configuration of a structure 1. The structure 1 includes piles 2, pile caps 4 a joined to pile heads of the piles 2, beams 5 connecting pile caps 4 a with each other, and piles 2 via pile caps 4 a. It has a supported upper structure 6. The pile 2, the pile cap 4 a and the beam 5 constitute a pile foundation 8 for supporting the superstructure 6.
The pile foundation 8 may have a footing in place of the pile cap 4a. Below, pile cap 4a and footing are also called foundation concrete part 4.

  FIG. 2 is a view for explaining the pile head joint portion 10. FIG. 3 is a view schematically showing the pile head, the joint member, the reinforcing bars (fixing bars), and the fixing body in FIG. 2, wherein the left half is a side view and the right half is a cross-sectional view. FIG. 4 is a view schematically showing the bonding member, where (a) is a front view, (b) is a side view, (c) is a top view, and (d) is a bottom view. FIG. 5 is a side view schematically showing a reinforcing bar. FIG. 6 is a cross-sectional view schematically showing a pile head, a joint member and a part of a reinforcing bar. FIG. 7 is a top view schematically showing a part of a pile head and a joining member.

As shown in FIGS. 1 to 7, the pile head joint portion 10 includes an upper end portion (pile head) 12 of the pile 2, a plurality of joint members 14, a plurality of reinforcing bars 16, and a foundation concrete portion 4. Is equipped.
The pile 2 may be a cast-in-place pile or a prefabricated pile. However, the joining member 14 is fixed to the outer peripheral surface of the cylindrical pile head 12 by welding. For this reason, in the case of cast-in-place piles, the pile 2 is a steel pipe concrete pile. Also, in the case of a prefabricated pile, the pile 2 is a steel pipe pile (SPP pile) or a concrete pile with outer shell steel pipe (SC pile) or concrete in which a steel reinforcing band is attached to the upper end Piles, for example, reinforced concrete piles (RC piles), prestressed concrete piles (PC piles, PRC piles), or high strength prestressed concrete piles (PHC piles) or the like.
In the present embodiment, the pile 2 is an SC pile and covers a cylindrical concrete portion 17 made of concrete, a metal end plate 18 covering both ends of the concrete portion 17, and an outer peripheral surface of the concrete portion 17 And an outer shell steel pipe 19. The end plate 18 has an annular shape and is welded to the shell steel pipe 19.

The plurality of joint members (joint couplers) 14 are made of metal, and are fixed to the outer peripheral surface of the pile head 12 by welding at intervals in the circumferential direction of the pile head 12.
The plurality of reinforcing bars 16 are made of metal and are attached to the pile head 12 via the joint members 14 respectively.
The foundation concrete portion 4 is made of concrete and surrounds the pile head 12, the plurality of joint members 14, and the plurality of reinforcing bars 16.
Although not shown in the figure, in the foundation concrete part 4, a split preventing reinforcement, a main reinforcement of the beam 5 and the like may be arranged.

Here, the reinforcement bar 16 has a shaft portion 20 having irregularities on the surface, and a screw portion 21 connected to one end of the shaft portion 20 and having a cross-sectional area smaller than that of the shaft portion 20. The reinforcing bars 16 may have screw portions 21 on both sides of the shaft portion 20. In this case, a nut as the fixing body 22 may be screwed into the screw portion 21 on the upper end side of the reinforcing bar 16.
For example, as the reinforcing bar 16, a deformed rebar as shown in FIG. 5 can be used.

  The bonding member 14 has a lower protrusion 23 and an upper protrusion 24. The lower protrusion 23 and the upper protrusion 24 are fixed to the outer peripheral surface of the pile head 12 by welding, and project laterally from the outer peripheral surface of the pile head 12. The upper protrusion 24 is disposed above the lower protrusion 23 in the axial direction of the pile head 12. For example, the joining member 14 is welded to the outer peripheral surface of the pile head 12 so that the position of the upper surface of the upper projection 24 coincides with the position of the upper end face of the pile head 12 in the axial direction of the pile head 12 Be done.

  The screw portion 21 of the reinforcing bar 16 is coupled to the lower projection 23. For example, as shown in FIG. 4, a screw hole 26 is formed in the lower protrusion 23, and the screw portion 21 is screwed into the screw hole 26. Alternatively, although not shown, a through hole is formed in the lower protrusion 23, and a nut is welded to the lower side of the lower protrusion 23 coaxially with the through hole. In this case, the nut can be regarded as a part of the lower projection 23, and by screwing the screw 21 into the nut, it can be regarded that the screw 21 is screwed to the lower projection 23. it can.

The shaft portion 20 of the reinforcement bar 16 extends between the lower projection 23 and the upper projection 24 in the axial direction of the pile head 12 and protrudes upward from the end face of the upper projection 24 and the pile head 12 Extend.
Thus, the upper projection 24 is shaped to allow passage of the reinforcing bars 16. On the other hand, the upper projection 24 has a portion of the foundation concrete portion 4 attached to the portion of the shaft portion 20 of the reinforcement bar 16 extending between the lower projection 23 and the upper projection 24 and the axis of the pile head 12 It is configured to engage in a direction.
For example, as shown in FIG. 4, the upper protrusion 24 has a fork portion 29 having a notch 28 for permitting passage of the reinforcing bar 16, and the fork portion 29 is concrete attached to the shaft portion 20. A portion of the portion 4 and an axial direction of the pile head 12 are engaged with each other.

Preferably, the joining member 14 further includes a connecting portion 30 integrally formed with the lower protrusion 23 and the upper protrusion 24, two reinforcing beam portions 32, and two reinforcing rib portions 34.
The connecting portion 30 has a plate shape extending in the axial direction and circumferential direction of the pile head 12, and connects the lower protrusion 23 and the upper protrusion 24 to each other. The connection portion 30 has a curved surface 35 which can be disposed along the outer peripheral surface of the pile head 12 on the pile head 12 side.
The reinforcing beam portion 32 extends in the axial direction of the pile head 12 and has a prismatic shape. The reinforcing beam portion 32 is integrally formed on both sides of the connecting portion 30 in the circumferential direction of the pile head 12. The reinforcing beam portion 32 extends between the lower protrusion 23 and the upper protrusion 24.
The reinforcing rib portion 34 is integrally formed at a corner formed between the reinforcing beam portion 32 and the lower protrusion 23.

Preferably, as shown in FIG. 7, both sides of the connection portion 30 in the circumferential direction of the pile head 12 are welded to the outer peripheral surface of the pile head 12. For this purpose, a grooved surface 36 inclined relative to the outer peripheral surface of the pile head 12 is provided on both sides of the connection portion 30 in the circumferential direction of the pile head 12, and the grooved surface 36 and the outer periphery of the pile head 12 A weld bead 38 is formed between the faces. Preferably, the grooved surface 36 and the weld bead 38 extend from the lower projection 23 to the upper projection 24 in the axial direction of the pile head 12.
In addition, the shape of the joining member 14 is not limited to what was mentioned above, For example, the joining member described in Unexamined-Japanese-Patent No. 2015-34458 can be used.

[Design Method of Pile Head Joint According to First Embodiment]
FIG. 8 is a flowchart schematically showing a procedure of a method of designing a pile head joint portion according to the first embodiment. FIG. 9 is a view for explaining a resistance mechanism model for calculating an allowable bending moment.
As shown in FIG. 8, the method of designing a pile head joint portion includes a specification selection process S1, an allowable bending moment calculation process S2, and a specification suitability determination process S3.

  In the specification selection step S1, the specifications of the pile head 12, the joint member 14, the reinforcement bars 16, and the base concrete portion 4 are selected. The specification of the pile head 12 is the specification of the pile 2 and is a pile diameter, a pile type, a material, and the like. The specification of the bonding member 14 refers to the shape, size, material and the like of the bonding member 14. The specifications of the reinforcing bars 16 include the shape, size, material, and the like of the reinforcing bars 16. The specification of the base concrete part 4 refers to the shape, size, material and the like of the base concrete part 4.

In the allowable bending moment calculation step S2, an allowable bending moment (short-term allowable bending moment) sMa of the pile head joint portion 10 is calculated based on the specification selected in the specification selection step S1.
In the specification suitability determination process S3, the suitability of the specification selected in the specification selection process S1 is determined based on the allowable bending moment sMa. For example, in the specification suitability determination step S3, the allowable bending moment sMa and the generated bending moment M ₀ of the pile head are compared, and if the generated bending moment M ₀ is smaller than the allowable bending moment sMa, the selected specification is appropriate It is determined that

  Here, in the allowable bending moment calculation step S2, the allowable bending moment sMa is calculated based on the resistance mechanism model shown in FIG. When a shear force Q acts on the pile head joint portion 10 and a bending moment M is generated, it is considered that the following mechanisms I, II, and III appropriately combine to resist the bending moment M.

The mechanism I is a resistance as a virtual RC cross section in which the reinforcement bar 16 is regarded as a main bar as shown in FIG. 9A, and a compressive force C acting on the reinforcement bar 16 and the pile head 12 and a reinforcement bar It is a resistance to the pulling force T acting on the 16. Hereinafter, the component of the allowable bending moment sMa according to the mechanism I is also referred to as a first allowable bending moment component sMa1.
The mechanism II is a resistance to the compressive force C acting on the outer peripheral surface of the pile head 12 from the foundation concrete portion 4 as shown in FIG. 9 (b). The component of the allowable bending moment sMa according to the mechanism II is hereinafter also referred to as a second allowable bending moment component sMa2.
The mechanism III is a resistance to the compressive force C acting on the asperities of the joint member 14 from the base concrete portion 4 as shown in FIG. 9C. The component of the allowable bending moment sMa according to mechanism III is hereinafter also referred to as a third allowable bending moment component sMa3.

Then, in the allowable bending moment calculation step S2 of the present embodiment, the upper side portion 40 of the foundation concrete portion 4 surrounding the portion of the shaft portion 20 of the reinforcement bar 16 projecting upward from the end face of the pile head 12 and the lower side projection portion It is assumed that a crack 44 is generated between the lower portion 42 of the foundation concrete portion 4 surrounding the portion of the stem portion 20 of the reinforcing bar extending between the upper projection 24 and the upper projection 24 (FIG. 9 (a)) reference). The cracks 44 typically extend obliquely downward 45 degrees from the upper protrusion 24. For this reason, the crack 44 is also referred to as a diagonal crack 44.
In the following description, the state in which the crack 44 is not generated is also referred to as "state A", and the state in which the crack 44 is generated is also referred to as "state B". In this embodiment, it is assumed that the state is B.

In the case of state B, due to the presence of the crack 44, mechanism III in the resistance mechanism model can not be expected, and the resistance based on mechanism III needs to be ignored.
On the other hand, regardless of the presence or absence of the crack 44, it is necessary to consider the tensile yield strength of the reinforcing bar 16 as mechanism I, but if the crack 44 is present, the tensile yield strength of the reinforcing bar 16 is The tensile yield strength of the shank 20 of the reinforcement bar 16 can be taken into account. The cross-sectional area of the shaft portion 20 is larger than the cross-sectional area of the screw portion 21, and the tensile yield strength of the shaft portion 20 is larger than the tensile yield strength of the screw portion 21. For this reason, being able to consider the tensile yield strength of the shaft portion 20 of the reinforcement bar 16 works advantageously in calculating the allowable bending moment sMa.

  FIG. 10 is a diagram for explaining the reason why the tensile yield strength Tby of the shaft portion 20 of the reinforcement bar 16 can be considered in the state B. When the crack 44 occurs, the lower portion 42 of the base concrete portion 4 adheres to the reinforcing bar 16 below the crack 44, so that the generation of the resistance force Fsb due to the adhesion can be expected. And, usually, the sum (Fsb + Tsy) of the resistance Fsb and the tensile yield strength Tsy of the screw portion 21 is designed to be equal to or higher than the tensile yield strength Tby of the shaft portion 20. The reinforcement bar 16 can withstand up to Tby.

For this reason, in the allowable bending moment calculation step S2 of the present embodiment, when calculating the resistance of the reinforcing reinforcement 16 projecting upward from the end of the pile head 12 and the foundation concrete portion 4 surrounding the reinforcing reinforcement 16, reinforcement is performed. The allowable bending moment sMa is calculated while neglecting the resistance acting on the foundation concrete part 4 from the joint member 14 while taking into consideration the tensile yield strength Tby of the shaft part 20 of the reinforcement 16. That is, the first allowable bending moment component sMa1 is calculated as the allowable bending moment sMa.
To calculate the allowable bending moment sMa in consideration of the tensile yield strength Tby, specifically, the allowable bending moment sMa is calculated using a function including the tensile yield strength Tby as a variable directly or indirectly. It means that.

  According to the above-described method for designing a pile head joint, in the case of assuming that a crack 44 occurs in the foundation concrete part 4, that is, in the case of the state B, the tensile yield strength Tby of the shaft part 20 of the reinforcement bar 16 is considered. On the other hand, the allowable bending moment sMa can be accurately calculated by calculating the allowable bending moment sMa while ignoring the resistance acting on the base concrete part 4 from the joint member 14. As a result, according to the above-described method of designing a pile head joint, it is possible to realize the pile head joint 10 having a sufficiently large allowable bending moment sMa with a low-cost specification.

  In addition, in the design method of a pile head junction part mentioned above, the resistance based on mechanism II may or may not be considered. When considering the resistance based on the mechanism II, the sum (sMa1 + sMa2) of the first allowable bending moment component sMa1 and the second allowable bending moment component sMa2 may be calculated as the allowable bending moment sMa. As described above, in consideration of the resistance based on the mechanism II, the allowable bending moment sMa is increased, and the specifications of the pile head 12, the joint member 14, the reinforcement bar 16, and the base concrete portion 4 can be suppressed. On the other hand, if the resistance based on the mechanism II is not taken into consideration, the allowable bending moment sMa becomes small, and a safety factor can be expected.

Hereinafter, mechanisms I to III shown in FIGS. 9A to 9C will be described in detail.
[Mechanism I]
The resistance based on the mechanism I is the resistance due to the compressive force C generated in the pile head 12 and the tensile force T of the reinforcing bars 16. Here, as shown in FIG. 11, the pile head joint portion 10 compresses the concrete of the foundation concrete portion 4 (pile cap 4a) larger than the pile cross sectional area Ac. For this reason, the compressive strength fc of the concrete in contact with the pile head joint portion 10 is increased by the local bearing effect. The ratio of the pile cap cross sectional area (bearing area) A ₀ to the pile cross sectional area (bearing pressure area) Ac is 5 or more, and a bearing effect of 2 or more can be expected in a pure compression state. In addition, the compressive strength fc of the concrete becomes (A ₀ / Ac) ^0.5 times by the bearing effect.

Then, as shown in FIG. 12, in consideration of the eccentrically compressed state due to bending, the bearing area Ac ′ becomes smaller than the pile cross sectional area Ac, and the bearing effect becomes larger.
In the calculation of the resistance based on the mechanism I, that is, the first allowable bending moment component sMa1, in the present embodiment, the increase in resistance due to the bearing effect is introduced by enlarging the virtual RC cross-sectional diameter D.
As in the present embodiment, when calculating the short-term allowable bending moment sMa of the pile head joint portion 10, the reinforcing bars 16 resist the tensile force T, and a cylindrical body having a virtual RC cross section is generated in the foundation concrete portion 4. It is general to think that it bears the compression force C.

  In the case of the pile head joining method by the main bar fixing method as in this embodiment, it is described in "Guide to Building Foundation Structure Design (1988)" of the Architectural Institute of Japan and the Road Association "Pile Foundation Design Handbook 2006 revised edition" Generally, a method of performing cross-sectional inspection of a pile head joint as a virtual RC cross section having a diameter D obtained by adding 200 mm to a pile diameter. Recently, in the Japan Association of Roads “Road Bridge Designation and Commentary IV Substructure edition” revised in March 2012, the diameter D of the virtual RC cross section is 0.25 Dp + 100 mm for the pile diameter Dp (additional diameter is maximum A method is shown in which the diameter is checked by adding 400 mm). At the Japan Highway Association, the diameter D of the virtual RC cross section has been revised and revised. Therefore, also when calculating the allowable bending moment sMa in the present embodiment, it is possible to adopt the cross section inspection method of the pile head joint portion 10 assuming the virtual RC cross section.

  Here, FIG. 13 schematically shows a horizontal load test device 50 of the pile head joint portion 10, and FIG. 14 shows an application pattern of horizontal load. The horizontal force test apparatus 50 can apply a horizontal force by the actuator 51 and can measure the horizontal displacement d1. The member angle on the vertical axis of the graph shown in FIG. 14 is a value (d1 / 1600) obtained by dividing the horizontal displacement d1 by 1600 which is the distance from the pile head to the load application point. Also, the horizontal force test apparatus 50 can measure the vertical displacements d2 and d3.

FIGS. 15 to 18 are photographs of the internal condition of the foundation concrete portion 4 taken through the foundation concrete portion 4 of the pile head joint portion 10 after the horizontal force test using the horizontal force testing device 50. And FIG. 19 is a figure for demonstrating that the virtual RC cross-sectional diameter D was set from the generation | occurrence | production condition of the crack in the foundation concrete part 4. FIG.
In addition, in FIGS. 13-19, the up-down direction of the pile head junction part 10 is reversed from the relationship of the structure of the horizontal-force-test apparatus 50. FIG.

  As shown in FIG. 15 to FIG. 18, after the horizontal force test, a crack 52 extending obliquely downward from the lower protrusion 23 at an angle of about 45 degrees is generated inside the foundation concrete part 4. Therefore, the length (hereinafter also referred to as the effective adhesion length) in which the foundation concrete portion 4 is attached to the shaft portion 20 of the reinforcement bar 16 between the lower projection 23 and the upper end of the upper projection 24 is Le In this case, a value obtained by adding 2Le to the pile diameter Dp is set as the maximum value of the diameter D of the virtual RC cross section. That is, the reinforcing bar 16 resists the tensile force, and the compressive force generated in the foundation concrete portion 4 is borne by the cylindrical body having the virtual RC cross-sectional diameter D (where D = Dp + 2Le).

Preferably, between the diameter D of the virtual RC cross section and the pile diameter Dp, the following equation:
Dp + Le ≦ D ≦ Dp + 2Le
The diameter D is selected such that the relationship indicated by.
More preferably, between the diameter D of the virtual RC cross section and the pile diameter Dp,
Dp + 1.5Le ≦ D ≦ Dp + 2Le
The diameter D is selected such that the relationship indicated by.
For example, the effective adhesion length Le is 140 mm or more and 200 mm or less.

  By selecting the diameter D of the virtual RC cross-section in this manner, the size of the virtual RC cross-sectional diameter D can be set larger than in the past. The larger the virtual RC cross-sectional diameter D is, the smaller the stress acting on the foundation concrete part 4 and the pile head 12 can be, and the larger the allowable bending moment sMa can be calculated. As a result, according to the above-described configuration, it is possible to realize a pile head joint having a sufficiently large allowable bending moment sMa with a low cost specification.

Then, the first short-term allowable bending moment component sMa1 according to Mechanism I can be calculated as follows, with reference to the "Recommended structure calculation criteria and commentary (2010)" of the Architectural Institute of Japan.
The first allowable bending moment component sMa1 of the pile head joint portion 10 with respect to the allowable axial force Na can be obtained by the following equation (1). The allowable axial force Na of the virtual RC cross section is one of N _{1 to} N ₃ whichever is smaller.

  Incidentally, the first moment of inertia Scn and the second moment of area Icn of the concrete portion in the virtual RC cross section are in accordance with the following equation (2).

  The first moment of area Sn and the second moment of area In with respect to the neutral axis are in accordance with the following [Equation 3].

The symbols in the formulas represent the following, and FIG. 20 shows the details of these symbols. In the state B in which the crack 44 is generated, the nominal cross-sectional area of the shaft portion 20 of the reinforcement bar 16 is used as the nominal cross-sectional area _ab of one reinforcement bar in the equation shown in [Equation 3].
a _b : Nominal cross-sectional area of one reinforcing bar (mm ² )
D: Diameter of virtual RC cross section (mm)
D _b : Arrangement diameter of reinforcement bars (mm)
d _c : Distance from the compression edge to the center of gravity of the compression side reinforcement (mm)
d _t : The distance from the tension edge to the center of gravity of the tensile reinforcement (mm)
f _c : Permissible compressive stress of concrete foundation part (N / mm ² )
f _b : Permissible compressive stress or tensile stress of reinforcement (N / mm ² )
I _cn : Second moment of area (mm ⁴ ) with respect to the neutral axis formed by the compressed concrete surface
I _n : second moment of area on neutral axis (mm ⁴ )
_s M _a1 : First short-term allowable bending moment component (N · mm)
n _e : Young's modulus ratio R: Radius of virtual RC section (mm)
R _b : Placement radius of reinforcement (mm)
S _cn : First moment of area section S _n relative to the neutral axis formed by the compressed concrete surface S ₁ : First moment of area section (mm ³ )
X ₀ : Distance from center of virtual RC section to neutral axis (mm)
θ: Angle to determine the neutral axis position in the circular section (rad)
θ _i : Placement angle of reinforcement position (rad)

[Mechanism II]
The second short-term allowable bending moment component sMa2 according to mechanism II is due to bearing resistance of the base concrete portion 4 and can be calculated by the following equation (4). As the bearing strength σ _c of the mechanism II, 2/3 · F _c which is the allowable compression stress degree of the RC structure can be used.
However, with respect to bearing capacity sigma _c, it may be taken into consideration an increase in compressive strength due to restraint effect of the pile cap 4a which pile 2 is embedded.
In the allowable bending moment calculation step S2, the second short-term allowable bending moment component sMa2 may or may not be considered.
FIG. 21 shows the details of the symbols in the formula.

[Mechanism III]
The third short-term allowable bending moment component sMa3 according to mechanism III is replaced by the allowable tensile strength of the reinforcing bars 16 with the compressive strength C _c due to the unevenness of the joint member 14 in the equation shown in [Equation 1] It can be calculated with reference to “Calculation criteria and explanations (2010)” (RC allows local plasticization of concrete at short-term allowance). The strength of the compressive reaction force of the unevenness of the joint member 14 is considered to be determined by the bearing failure of the concrete (in this case, the oblique cracks 44 from the joint member 14 do not occur. The yield strain of the reinforcing bars 16 is the concrete compression yield). Greater than strain).
However, the third short-term allowable bending moment component sMa3 is ignored in the allowable bending moment calculating step S2 when it is assumed that the oblique crack 44 is generated in the pile head joint portion 10.
Also, if the expected resistance by mechanisms III, the joining member 14 is designed so as not to yield the compression force C _c.

[Design Method of Pile Head Joint according to Second Embodiment]
Hereinafter, the design method of the pile head joint part which concerns on 2nd Embodiment is demonstrated. In the description of the embodiments below, differences from the above-described embodiments will be mainly described, and descriptions of the same or similar configurations will be omitted or simplified.

In the method of designing a pile head joint according to the second embodiment, in the allowable bending moment calculation step S2,
・ Reinforcement bar extending between the upper side portion 40 of the foundation concrete portion 4 surrounding the portion of the shaft portion 20 of the reinforcement bar 16 projecting upward from the end face of the pile head 12, and between the lower side projection 23 and the upper side projection 24 Assuming that no crack 44 occurs between the lower portion 42 of the foundation concrete portion 4 surrounding the portion of the shaft portion 20 of 16, and
-When calculating the resistance of the reinforcement portion 16 projecting upward from the end of the pile head 12 and the foundation concrete portion 4 surrounding the reinforcement portion 16, the tensile yield strength Tsy of the screw portion 21 of the reinforcement portion 16 is taken into consideration It differs from the design method of the pile head joint according to the first embodiment in that the allowable bending moment sMa is calculated in consideration of the resistance acting on the foundation concrete part 4 from the joint member 14 as well.

That is, in the second embodiment, assuming that the crack 44 is not generated in the state A, the first 1 'allowable bending moment component sMa1' by the mechanism I and the third allowable bending moment component sMa3 by the mechanism III are considered. . That is, the sum (sMa1 ′ + sMa3) of the first ′ allowable bending moment component sMa1 ′ and the third allowable bending moment component sMa3 is calculated as the allowable bending moment sMa.
The calculation method of the first 'allowable bending moment component sMa1' is the nominal cross-sectional area of the screw portion 21 of the reinforcement bar 16 as the nominal cross-sectional area _ab of one reinforcement bar in the equation shown in [Equation 3] Is different from the calculation method of the first allowable bending moment component sMa1 only in that
On the other hand, the second allowable bending moment component sMa2 according to the mechanism II may or may not be considered as in the first embodiment.

Here, FIG. 22 is a diagram for explaining that the determined position of the reinforcing muscle section strength is different from that in the first embodiment (see FIG. 10). In the state A in which the crack 44 is not generated, the resistance Fsb from the base concrete part 4 can not be expected as in the case of the state B. For this reason, it is necessary to consider the tensile yield strength Tsy of the screw portion 21 as the tensile yield strength of the reinforcing bar 16, and for that reason, in the equation shown in [Equation 3], the nominal cross-sectional area a _{b of} one reinforcing bar As, the nominal cross-sectional area of the screw portion 21 of the reinforcing bar 16 is used.

According to the design method of the pile head joint portion according to the above-described second embodiment, when it is assumed that the crack 44 does not occur in the base concrete portion 4, that is, in the case of the state A, the screw portion 21 of the reinforcement bar 16 The allowable bending moment sMa can be accurately calculated by calculating the allowable bending moment sMa in consideration of the resistance acting on the foundation concrete part 4 from the joint member 14 while considering the tensile yield strength Tsy. As a result, according to the method of designing the pile head joint portion according to the second embodiment, the pile head joint portion 10 having an allowable bending moment sMa of a sufficient magnitude can be realized with a low-cost specification.
Note that calculating the allowable bending moment sMa in consideration of the tensile yield strength Tsy and the resistance acting on the base concrete part 4 from the joint member 14 is, specifically, directly or indirectly using the tensile yield strength Tsy as a variable. It means that the allowable bending moment sMa is calculated using the function included in and the function directly or indirectly including the resistance acting on the base concrete part 4 from the joint member 14 directly or indirectly.

[Design Method of Pile Head Joint According to Third Embodiment]
Hereinafter, a method of designing a pile head joint according to the third embodiment will be described.
The method of designing a pile head joint according to the third embodiment is different from the method of designing a pile head joint according to the first embodiment and the second embodiment in the allowable bending moment calculation step S2. FIG. 23 is a flowchart showing a schematic procedure of allowable bending moment calculating step S2 in the method of designing a pile head joint portion according to the third embodiment.

As shown in FIG. 23, the allowable bending moment calculating step S2 in the method of designing a pile head joint portion according to the third embodiment includes a first allowable bending moment calculating step S4, a second allowable bending moment calculating step S5, and an allowable bending. It has a moment selection step S6.
In the first allowable bending moment calculation step S4, while considering the tensile yield strength Tsy of the screw portion 21 of the reinforcing bar 16, taking into consideration the resistance acting on the base concrete portion 4 from the joint member 14, the allowable bending moment sMa The first allowable bending moment sMaA is calculated. The first allowable bending moment sMaA is an allowable bending moment sMa calculated by the method of designing the pile head joint according to the second embodiment described above.

  In the second allowable bending moment calculation step S5, while considering the tensile yield strength Tby of the shaft portion 20 of the reinforcing bar 16, while ignoring the resistance acting on the base concrete portion 4 from the joint member 14, the allowable bending moment sMa The second allowable bending moment sMaB is calculated. The second allowable bending moment sMaB is an allowable bending moment sMa calculated by the method of designing the pile head joint portion according to the first embodiment described above.

  Then, in the allowable bending moment selection step S6, the first allowable bending moment sMaA and the second allowable bending moment sMaB are compared, and the smaller of the first allowable bending moment sMaA and the second allowable bending moment sMaB is taken as the allowable bending moment sMa. select.

  According to the design method of the pile head joint portion according to the third embodiment described above, the smaller one of the first allowable bending moment sMaA and the second allowable bending moment sMaB is selected as the allowable bending moment sMa. Regardless of the occurrence, it is possible to realize a pile head joint 10 having a sufficiently large allowable bending moment with a low-cost specification in anticipation of safety.

Preferably, the compressive strength Cc acting on the joint member 14 from the base concrete part 4 by the mechanism III is larger than the difference between the yield strength Tby of the shaft part 20 of the reinforcement bar 16 and the yield strength Tsy of the shaft part 20 It is set as (Cc T Tby-Tsy). FIG. 24 shows a schematic procedure of the allowable bending moment selection step S6 in such a case (Cc ≧ Tby−Tsy).
The allowable bending moment selection step S6 includes a yield determination step S7, a first allowable bending moment selection step S8, and a second allowable bending moment selection step S9.
In the yield determination step S7, it is determined whether or not the upper projection 24 is to yield by the compressive force Cc acting on the upper projection 24 from the base concrete portion 4.

If it is determined that the upper protrusion 24 is to yield as a result of the determination in the yield determination step S7, the first allowable bending moment selection step S8 is executed. In the first allowable bending moment selection step S8, the first allowable bending moment sMaA is selected as the allowable bending moment sMa.
On the other hand, when it is determined that the upper projection 24 does not yield as a result of the determination in the yield determination step S7, the second allowable bending moment selection step S9 is performed. In the second allowable bending moment selection step S9, a second allowable bending moment sMaB is selected as the allowable bending moment sMa.

  According to the above configuration, when the yield strength of the upper projection 24 is smaller than the difference between the tensile yield strength Tby of the shaft portion 20 of the reinforcement bar 16 and the tensile yield strength Tsy of the screw portion 21, the first allowable bending Moment sMaA is selected as allowable bending moment sMa. That is, when the yield strength of the upper projection 24 is smaller than the difference between the tensile yield strength Tby of the shaft portion 20 of the reinforcement bar 16 and the tensile yield strength Tsy of the screw portion 21, the upper projection 24 yields. Therefore, it is judged that the first allowable bending moment sMaA becomes smaller, and the first allowable bending moment sMaA is selected as the allowable bending moment sMa. Thus, according to the above configuration, the allowable bending moment sMa can be accurately calculated in anticipation of safety, and the pile head joint portion 10 having the sufficient allowable bending moment can be realized with a low-cost specification It is.

[Design Method of Pile Head Joint According to Fourth Embodiment]
Hereinafter, a method of designing a pile head joint according to the fourth embodiment will be described. The method for designing a pile head joint portion according to the fourth embodiment includes the first to third embodiments in that the generated bending moment M _θ is calculated in consideration of the elastic rotational stiffness K ₀ in the specification suitability determination step S3. It differs from the design method of the pile head joint of form.
FIG. 25 shows a schematic procedure of the specification suitability determination step S3 in the method of designing a pile head joint portion according to the fourth embodiment. The specification suitability determination step S3 includes an elastic rotational stiffness calculation step S10, a generated bending moment calculation step S11, and a bending moment comparison determination step S12.

In the elastic rotational stiffness calculation step S10, the elastic rotational stiffness K ₀ of the pile head joint portion 10 based on the rotational angle (pile head rotational angle) θ ₀ of the pile head 12 corresponding to the allowable bending moment sMa and the allowable bending moment sMa. Calculate At this time, as follows, and when divided into each range of the axial force acting on the pile head joint 10, to calculate the elastic rotational stiffness K _0.
In the case of 0 <axial force, the elastic rotational stiffness K ₀ is not taken into consideration (fixed degree α ₀ = 1).
In the case of axial force ≦ 0, the elastic rotational stiffness K ₀ is calculated by the following equation (5).

In the case of the state B, the pile head rotation angle θ ₀ can be obtained by the following equation [6] according to the determined position (see FIG. 10) of the cross-sectional strength of the reinforcement bar 16. FIG. 26 shows the details of the symbols in the formula. In Equation 6, 0.5 sfa · ψb · lb ₁ and 0.5 sfa · ψb · lb ₂ represent the resistance acting on the shaft 20 by the adhesion of the base concrete portion 4. The resistance increases in proportion to the distance from the determined position of the cross-sectional strength, and the resistance reduces or cancels the tensile force acting on the shaft 20 according to the distance from the determined position of the cross-sectional strength. As a result, the distribution of force in the axial direction of the pile head 12 is as shown in FIG. 27, and the area of the hatched area in FIG. 27 is divided by ( _ab · Eb) The elongation amount δb can be obtained.

  As Ty in the above [Equation 6], the tensile yield strength Tby of the shaft portion 20 of the reinforcement bar 16 can be used. Moreover, you may use what multiplied the coefficient of 0-1, the tensile yield strength Tby of the axial part 20 as Ty.

On the other hand, in the case of the state A, the pile head rotation angle θ ₀ can be determined by the following equation 7 according to the determined position (see FIG. 22) of the cross-sectional strength of the reinforcement bar 16. In Equation 7, 0.5 sfa · ψb · (lb ₁ + lb ₂ ) represents the resistance that acts on the shaft portion 20 due to the adhesion of the base concrete portion 4. The resistance increases in proportion to the distance from the determined position of the cross-sectional strength, and the resistance reduces or cancels the tensile force acting on the shaft 20 according to the distance from the determined position of the cross-sectional strength. As a result, the distribution of force in the axial direction of the pile head 12 is as shown in FIG. 28, and the area of the hatched area in FIG. 28 is divided by ( _ab · Eb) The elongation amount δb can be obtained.

  As Ty in the above [Equation 7], the tensile yield strength Tsy of the screw portion 21 of the reinforcing bar 16 can be used. Further, as Ty, one obtained by multiplying the tensile yield strength Tsy of the screw portion 21 by a coefficient of 0 to 1 may be used.

In the generated bending moment calculation step S11, the pile is produced taking into account the elastic rotational rigidity K ₀ of the pile head joint portion 10 under the condition that axial compressive force does not act on the pile head 12 (axial force ≦ 0). When the assumed horizontal force H acts on the head 12, the generated bending moment M _θ generated in the pile head 12 is calculated. For this purpose, the elastic rotation stiffness K ₀ is used to determine the degree of fixation α ₀ at the time of elasticity, as shown in the following [Equation 8]. Then, the bending moment (rigid connections generated bending moment) M ₀ occurs when the horizontal force H acts, by multiplying the fixed degree alpha _0, generating bending Request moment M _theta.

In the bending moment comparison determination step S12, it is determined whether or not the generated bending moment M _θ calculated in the generated bending moment calculating step S11 is smaller than the allowable bending moment sMa. As a result of the determination, if the generated bending moment M _θ is smaller than the allowable bending moment sMa (sMa> M _θ ), the pile head 12, the joint member 14, the reinforcing bars 16 and the foundation concrete selected in the specification selecting step S1. It is determined that the specifications of the part 4 are appropriate, and if the generated bending moment M _θ is equal to or larger than the allowable bending moment sMa (sMa ≦ M _θ ), it is determined that the specifications are inappropriate. That is, one of the conditions for determining that the specifications of the pile head 12, the joint member 14, the reinforcement bars 16 and the foundation concrete part 4 are appropriate is that the generated bending moment M _θ is smaller than the allowable bending moment sMa (sMa > M _θ ).

L ₀ is the distance (rotational radius) from the outermost reinforcement bar to the rotation center O, but as shown in FIG. It may be set to the same value as the distance to the center of the reinforcing bar 16 or may be set to the same value as the pile diameter Dp. The turning radius L ₀ is usually smaller than the distance from the end of the compression side stake head 12 to the center of the tension side reinforcement bar 16 or the pile diameter Dp, and if the turning radius L ₀ is set larger, the safety Can be expected. Of course, the turning radius L ₀ may be determined more accurately by simulation or experiment.

Conventionally, in the case of the pile head joint portion 10 in which the foundation concrete portion 4 adheres to the reinforcing bars 16, the generated bending moment M _θ generated at the pile head 12 is calculated as the fixation degree α ₀ is 1. (M _θ = M ₀ ).
In this respect, according to the examination by the present inventors, even if the base concrete portion 4 is attached to the reinforcing bar 16, even if the fixing degree α ₀ is not set to 1, the generated bending moment M _θ is calculated. It has been found that there is a good case, that is, there may be cases where the generated bending moment M _θ may be calculated taking into account the elastic rotational stiffness K ₀ . Specifically, it was found that when the axial direction compressive force is not applied to the pile head 12, calculation may be made without setting the fixing degree α ₀ to 1.

Therefore, in the method of designing a pile head joint according to the fourth embodiment, the elastic rotational rigidity K ₀ of the pile head joint 10 is considered under the condition that no axial compressive force is applied to the pile head 12. The generated bending moment M _θ generated in the pile head 12 when the assumed horizontal force H acts on the pile head 12 is calculated. As described above, by considering the elastic rotational rigidity K ₀ of the pile head joint portion 10, the fixing degree α ₀ can be made smaller than 1 and the generated bending moment M _θ can be made small. Thus, under the condition that the axial compressive force on the pile head 12 is not acting, it is possible to reduce the occurrence bending moment M _theta, is possible to reduce the bending moment M _theta generation than the allowable bending moment sMa it can. As a result, according to the method of designing a pile head joint portion according to the fourth embodiment, the pile head joint portion 10 having an allowable bending moment sMa of a sufficient magnitude can be realized with a low-cost specification.

In addition, as an analysis method used in the design of the pile foundation 8, a spring element obtained by discretizing the ground, a method by a multilayer ground analysis model in which the pile 2 is replaced with a beam element, and a solution of an elastic bearing beam in a semi-infinite uniform ground There is a method (Chang's method). The former is regarded as the detailed method, and the latter as the simplified method. In the case of the detailed method, it is possible to evaluate elastic rotational rigidity by directly providing a rotary spring at the pile head joint portion 10. On the other hand, the simple method, in order to consider the elastic rotation stiffness of the pile head joint 10, it is necessary to introduce a degree of fixation alpha _0. Although there are several calculation methods for calculating the pile head fixation degree α ₀ , in the fourth embodiment described above, a method relating to the solution of an elastic bearing beam by using the equation shown in [Equation 8] The pile head fixation degree α ₀ is calculated by
Under such circumstances, the elastic rotational stiffness K ₀ can be evaluated using any equation other than the equation shown in [Equation 8], and can be evaluated not only by other simplified methods but also by detailed methods.

[Design Method of Pile Head Joint According to Fifth Embodiment]
Hereinafter, a method of designing a pile head joint portion according to the fifth embodiment will be described. In the method of designing a pile head joint according to the fifth embodiment, the elastic rotational stiffness K ₀ is calculated using the larger of the first allowable bending moment sMaA and the second allowable bending moment sMaB in the specification suitability determination step S3. In the point, it differs from the design method of a pile head joint part of a 4th embodiment.
FIG. 29 is a flowchart showing a schematic procedure of a method of designing a pile head joint portion according to a fifth embodiment. The design method of the pile head joint according to the fifth embodiment selects the larger of the first allowable bending moment sMaA and the second allowable bending moment sMaB (maximum allowable bending moment: sMah = max (sMaA, sMaB)). It further includes step S13. Then, in the elastic rotational stiffness calculation step S10 ′, the elastic rotational stiffness K ₀ is calculated by dividing the maximum allowable bending moment sMah by the pile head rotational angle θ ₀ .

According to the method of designing the pile head joint portion according to the fifth embodiment described above, as in the case of the fourth embodiment, the generated bending moment under the condition that the axial direction compressive force does not act on the pile head 12 M _θ can be reduced, and the generated bending moment M _θ can be smaller than the allowable bending moment sMa.
On the other hand, when elastic rotational rigidity K ₀ is underestimated, that is, when the degree of fixation α ₀ is underestimated, the calculated bending moment M _θ becomes too small. When the generated bending moment M _θ and the allowable bending moment sMa are compared, there may be a problem in the validity of the comparison result.
In this respect, according to the method of designing the pile head joint portion according to the fifth embodiment described above, the maximum allowable bending moment sMah and the pile head which are the larger of the first allowable bending moment sMaA and the second allowable bending moment sMaB Since the elastic rotational stiffness K ₀ of the pile head joint portion 10 is calculated based on the rotational angle θ _{0 of} 12, the magnitude of the elastic rotational stiffness K ₀ is prevented from being underestimated. As a result, according to the method of designing a pile head joint portion according to the fifth embodiment, the validity of the result when the generated bending moment M _θ and the allowable bending moment sMa are compared is secured, and the sufficient size of A pile head joint 10 having an allowable bending moment sMa can be reliably realized with a low-cost specification.
Preferably, the maximum allowable bending moment sMah is an allowable bending moment obtained by accumulating all of the mechanisms I, II and III. That is, the maximum allowable bending moment sMah is the sum of the first allowable bending moment component sMa1, the second allowable bending moment component sMa2, and the third allowable bending moment component sMa3.

  Preferably, in the elastic rotational stiffness calculation steps S10 and S10 ′, as shown in the above [Equation 6] or [Equation 7], in consideration of the adhesion of the base concrete portion 4 to the shaft portion 20 of the reinforcement bar 16, A step of calculating the amount of extension δb of the reinforcing bar 16 located on the pulling side is included.

If elongation of δb is excessively calculated, the rotational angle theta ₀ of pile head 12 is overestimated, the elastic rotational stiffness K ₀ of the pile head joint 10 is underestimated. If elastic rotational rigidity K ₀ is underestimated, that is, if the degree of fixation α ₀ is underestimated, the generated bending moment M _θ to be calculated becomes too small. When the generated bending moment M _θ and the allowable bending moment sMa are compared, there may be a problem in the validity of the comparison result.
In this respect, according to the above configuration, since the amount of elongation δb of the reinforcing bars 16 is calculated in consideration of the adhesion of the base concrete portion 4 to the shaft portion 20 of the reinforcing bars 16, the amount of elongation δb may be excessively calculated. It is prevented. As a result, according to the above configuration, the validity of the result when the generated bending moment M _θ and the allowable bending moment sMa are compared is secured, and the pile head joint portion 10 having the allowable bending moment sMa of a sufficient size. Can be realized with low cost specifications.

[Design Method of Pile Head Joint According to Sixth Embodiment]
Hereinafter, a method of designing a pile head joint portion according to the sixth embodiment will be described. In the method of designing a pile head joint according to the sixth embodiment, the bending moment (rigid connection generated bending moment) M ₀ and the allowable bending moment obtained without taking into consideration the pile head rotation angle θ ₀ in the specification suitability determination step S3 It differs from the design method of the pile head joint of the fourth embodiment in that it is compared with sMa.
FIG. 30 is a flow chart showing a schematic procedure of a method of designing a pile head joint portion according to a sixth embodiment. The method of designing a pile head joint according to the sixth embodiment further includes a rigid joint generated bending moment comparison / determination step S14. In the rigid connection generated bending moment comparison / determination step S14, the pile head 12 is operated when the assumed horizontal force H acts on the pile head 12, which is calculated ignoring the elastic rotational rigidity K ₀ of the pile head joint 10 It is determined whether the generated rigid connection generated bending moment M ₀ is larger than the allowable bending moment sMa.
And one of the conditions for determining that the specifications of the pile head 12, the joint member 14, the reinforcement bars 16 and the foundation concrete part 4 are appropriate is the bending moment generated in the rigid connection at the bending joint comparing / determining step S 14. It is determined that M ₀ is larger than the allowable bending moment sMa.

According to the design method of the pile head joint portion according to the sixth embodiment described above, when the bending moment M ₀ generated by the rigid connection calculated by neglecting the rotation angle θ ₀ of the pile head 12 is larger than the allowable bending moment sMa Since it is determined that the specifications of the pile head 12, the joint member 14, the reinforcement bars 16 and the foundation concrete part 4 are appropriate, the specifications of the pile head 12, the joint members 14, the reinforcement bars 16 and the foundation concrete part 4 Is prevented from becoming excessive. As a result, according to the method of designing a pile head joint portion according to the sixth embodiment, the pile head joint portion 10 having an allowable bending moment sMa of a sufficient magnitude can be reliably realized with a low-cost specification.

[Design Method of Pile Head Joint According to Seventh Embodiment]
Hereinafter, a method of designing a pile head joint portion according to the seventh embodiment will be described. In the method of designing a pile head joint according to the seventh embodiment, the specification selection step S1, the allowable bending moment calculation step S2, and the specification suitability determination step S3 such that the allowable bending moment sMa approaches the generated bending moment M _θ. Is different from the method of designing a pile head joint according to the first to sixth embodiments.
Preferably, as shown in FIG. 31, the specification selection step S1, the allowable bending moment calculation step S2 and the specification suitability determination step S3 are repeated until the generated bending moment M _θ becomes smaller than the allowable bending moment sMa.
More preferably, rigid to the joining generating the bending moment M ₀ becomes larger than the allowable bending moment SMA, specification selection step S1, the allowable bending moment calculation step S2 and specifications appropriateness determination step S3 is repeated.

[Method of Manufacturing Pile Head Joint according to Eighth Embodiment]
Hereinafter, a method of manufacturing a pile head joint portion according to the eighth embodiment will be described. The manufacturing method of the pile head joint portion according to the eighth embodiment is appropriate according to the design method of the pile head joint portion according to any one of the above-described first to seventh embodiments as shown in FIG. The pile head joint portion constructing step S16 of constructing the pile head joint portion 10 on the basis of the specifications of the pile head 12, the joint member 14, the reinforcement bars 16, and the foundation concrete portion 4 determined as
In the pile head joint construction step S16, at least the pile 2 is built on the ground, the joint member 14 is welded to the outer peripheral surface of the pile head 12, the reinforcement bar 16 is joined to the joint member 14, and the pile head 12 It has a process of placing concrete around.

  According to the method of manufacturing a pile head joint according to the eighth embodiment, a pile head determined to be appropriate by the method of designing a pile head joint according to any one of the first to seventh embodiments described above Since the pile head joint portion 10 is constructed based on the specifications of the portion 12, the joint member 14, the reinforcing bars 16 and the foundation concrete portion 4, the pile head joint portion 10 having a sufficiently large allowable bending moment sMa is reduced in cost Can be realized with the following specifications.

〔Example〕
1. Confirmation of validity of allowable bending moment and elastic rotational stiffness Repeated pile head horizontal load test was conducted for the purpose of verification of bending performance of pile head joint and validity of design method.
1) Test method and test body specifications Table 1 shows the test body specifications, and FIG. 13 shows a horizontal load test device 50 of the pile head joint portion 10. The tests were conducted with a total of six tests, taking pile diameters (φ 400 and φ 600), axial forces (0 kN and 1500 kN), diameters of reinforcement bars (D35 and D41) and the number of reinforcement bars (6 and 10) as verification parameters. . The pile was a concrete filled steel pipe simulating an outer shell steel pipe wound concrete pile (SC pile). The steel pipe is provided with an end plate equivalent to the wall thickness of the SC pile at the same diameter, and the same concrete as the foundation concrete part was cast (filled) inside the steel pipe. Concrete filled steel pipes are designed so that failure does not occur prior to failure of the pile head joint.
In addition, in order to measure the strain distribution of the reinforcing bars in the joint member, a plurality of strain gauges were attached to each reinforcing bar.
Also, by measuring the rotation angle theta ₀ of pile head, in order to obtain experimental values eK ₀ of elastic rotational stiffness _{K 0,} it was measured vertical displacement d2, d3.

As shown in FIG. 13, the upper portion of the pile was provided with a square steel pipe from a position 100 mm above the foundation concrete surface, and was joined to the horizontal load test device 50 by high strength anchor joining. As a method of producing a test body, a pile was disposed on the upper side and a foundation concrete portion on the lower side, a formwork was constructed, and concrete was cast to a predetermined height in the pile. After concrete curing, non-shrink mortar was placed at the flange position of the square steel pipe.
Then, horizontal loading was performed on each test body in the horizontal loading pattern shown in FIG.

2) Test results (1) Allowable bending moment Table 2 shows the experimental value Me of the allowable bending moment obtained from the test results and the allowable bending moment sMa (calculated value) obtained based on the mechanisms I, II and III. .

As shown in Table 2, the test body 3 is a test body in which the reinforcement screw portion yield precedes the occurrence of the oblique crack. The ratio of the experimental value to the calculated value of the short-term allowable bending moment is 1.12 to 1.50 (average 1.28), and the short-term allowable bending moment can be accurately calculated based on the mechanisms I, II and III. I understand that.
The calculated value is smaller than the experimental value. This is considered to be the effect that the resistance of the mechanism II is increased due to the bearing effect, and the effect not considering the frictional resistance around the embedded pile. If the calculated value is smaller than the experimental value, it is considered to be safe and to be preferable.

(2) the elastic rotational stiffness Table 3 shows a comparison of the rotational stiffness eK ₀ when short allowable bending moment at the time of the experiment and calculated cK ₀ of elastic rotational stiffness K ₀ (design value). The degree of fixation α ₀ in the table defines the ratio of the theoretical solution of the bending moment of the pile head in the case of full fixation of the pile head to the equivalent value in consideration of the rotational rigidity of the pile head. It is a value obtained from the equation shown in the above [Equation 8] as 0. The following can be understood from Table 3.
(I) The ratio of the elastic rotational stiffness cK ₀ obtained by calculation to the short-term allowable rotational stiffness eK ₀ obtained by the experiment is 1.00 to 2.85.
(Ii) the ratio of the elastic fixing of alpha ₀ obtained by calculation with respect to the fixed degree alpha ₀ obtained in the experiment is 1.00 to 1.16.
(Iii) Since the ratio of the elastic fixation degree α ₀ obtained by the calculation to the fixation degree α ₀ obtained by the experiment substantially exceeds 1.0, in consideration of the elastic rotational rigidity cK ₀ obtained by the calculation It can be confirmed that the calculated generated bending moment M _θ gives an evaluation on the safety side at the time of design.

2. Confirmation of Validity of Permissible Bending Moment, Virtual RC Cross Section Diameter and Elastic Rotational Rigidity 1) Pile Stress Integrated Analysis Pile stress integrated analysis at a pile head joint using joining members was performed under the following conditions.
(1) Building Superstructure: RC structure 12F scale Pile arrangement: 12m x 36m (1 x 6 spans) (see Figure 32)
(2) Design axial force The design axial force is shown in Table 4 below.

(3) External force for design Horizontal force of upper part and base part: 66000 × 0.15 = 9900 kN
Horizontal force of foundation weight: 1862 × 0.1 = 186 kN
Design external force 10100 kN
(4) Ground conditions The ground conditions, pile specifications and reinforcement bar specifications are shown in Tables 5 to 7 below.
As ground conditions, two cases where N value of depth 0-8m is 1 or 3 were set, and pile specification and reinforcement bar specification were selected for each case. Table 7 also shows pile head displacement, pile head bending, and shear force.

(5) Analysis method-The elastic rotational stiffness is calculated on the assumption that the place where pullout is occurring is fixed at 0.9. Elsewhere, the degree of fixation is considered to be 0.999, and elastic rotational stiffness is calculated.
-The short-term fluctuation axial force at the four corners (Y1-X1, etc.) is set as 130% of the long-term axial force including the pile cap weight. The number of pillars is reduced.
・ We carried out surface ground N value with 1.0 and 3.0.
(6) Analysis Results FIG. 33 shows the NM curve of the pile P1 when the N value = 3.0. FIG. 34 shows the NM curve of the pile P1 when the N value = 1.0. FIG. 35 shows the NM curve of the pile P2 when the N value = 1.0.
(I) As shown in FIG. 33 and FIG. 34, in the range where the compression force is less than 0, by calculating the generated bending moment M _θ in consideration of the elastic rotational rigidity, the generated bending moment M _θ is a short-term allowable bending It can be seen that it can be made smaller than the moment sMa.
(Ii) As shown in FIG. 35, also in the pile P2 to which a compressive force always acts, the generated bending moment M _θ is determined from the short-term allowable bending moment sMa by appropriately selecting the specification (shaft diameter) of the reinforcing bars It can also be seen that it can be made smaller.
In FIG. 35, when the shaft diameter of the reinforcing bar is D41, the generated bending moment M _θ is smaller than the short-term allowable bending moment sMa, but assuming that the virtual RC cross-sectional diameter D is considered as this premise It must be noted. By considering the virtual RC cross-sectional diameter D, it is possible to increase the first allowable bending moment component sMa1 according to the mechanism I, and consequently to increase the allowable bending moment sMa. Under this premise, when the shaft diameter of the reinforcing bar is D41, the generated bending moment M _θ is smaller than the short-term allowable bending moment sMa.

The present invention is not limited to the above-described embodiments, and includes the embodiments in which the above-described embodiments are modified, and the embodiments in which these embodiments are appropriately combined.
For example, according to the above-described pile head joint design method, pile head joints other than the above-described pile head joint 10 can also be designed. FIG. 36 schematically shows a part of a pile head joint 100 a that can be designed by the method of designing a pile head joint according to the first embodiment.
The pile head joint portion 100 a is different from the pile head joint portion 10 in that the pile head joint portion 100 a further includes a plurality of partition members 102 a corresponding to the joint member 14.
The partition member 102a has a wedge shape (groove shape) as shown in FIG. 37, and has, for example, a U-shaped cross-sectional shape. The partition member 102 a has a pair of rectangular side walls (first side walls) 104 and a semi-cylindrical side wall (second side wall) 106 connecting the first side walls 104 to each other. As shown in FIGS. 38 and 39, the first side walls 104 are disposed on both sides of the corresponding joining member 14 in the circumferential direction of the pile head 12, and are disposed parallel to each other with the joining member 14 interposed therebetween. Be done. The partition member 102 a is fixed to the pile head 12 by welding, for example, spot welding or spot welding to the outer peripheral surface of the pile head 12. The second side wall 106 is disposed to face the outer peripheral surface of the pile head 12 with the joining member 14 interposed therebetween.

The first side wall 104 and the second side wall 106 are laterally separated from the joint member 14 and the portion (shaft member inner portion) 20 a of the shaft portion 20 extending between the lower projection 23 and the upper end surface of the upper projection 24. A space is present inside the partition member 102a, that is, between the first side wall 104 and the second side wall 106 and the joint member inner portion 20a. The space constituting the foundation concrete portion 4 is filled with the space.
In addition, when the space inside the partition member 16a is narrow and it is difficult to be filled with concrete, a curable material such as mortar or grout is filled inside the partition member 102a before placing the concrete of the base concrete part 4 You may

  According to the pile head joint portion 100a described above, one partition member 102a constitutes one partition wall 108 disposed on the side of the joint member inner portion 20a of the shaft portion 20 of one corresponding reinforcing bar 16 The foundation concrete portion 4 can be divided into the inside and the outside in the radial direction of the reinforcing bars 16 on the side of the joint member inner portion 20 a of the shaft portion 20. By partitioning the foundation concrete portion 4 in this manner, as shown in FIG. 40, a portion of the foundation concrete portion 4 adhered to the joint member inner portion 20 a of the shaft portion 20 in the radial direction of the reinforcement bar 16 (adhesion portion The connection between the (proximal part) 110 and the part (distal part) 112 of the base concrete part 4 outside the dividing wall 108 is cut off. Thereby, when a bending moment acts on the pile head joint portion 100a, the attached portion 110 of the foundation concrete portion 4 is easily displaced relative to the distal portion 112, and as shown in FIG. 40, from the attached portion 110 A force (resistance due to adhesion) Fsb that acts on the upper protrusion 24 is generated.

  As a result, in calculating the allowable bending moment sMa, the resistance Fsb can be taken into consideration in addition to the tensile yield strength Tsy of the screw portion 21. However, a relationship represented by Tby ≦ Tsy + Fsb is usually established. As a result, when calculating the allowable bending moment sMa, it becomes possible to take into consideration the tensile yield strength Tby of the shaft portion 20 of the reinforcement bar 16 regardless of the presence or absence of cracking in the base concrete portion 4 and the allowable bending moment Can be calculated easily. That is, the second allowable bending moment sMaB can be calculated as the allowable bending moment sMa, and the design method of the pile head joint according to the first embodiment can be adopted.

FIG. 41 schematically shows a part of a pile head joint 100 b that can be designed by the method of designing a pile head joint according to the first embodiment.
The pile head joint portion 100b is different from the pile head joint portion 100a in that the pile head joint portion 100b includes partition members 102b instead of the plurality of partition members 102a.
As shown in FIGS. 41 to 43, the partition member 102b has a cylindrical peripheral wall 114, and the peripheral wall 114 is disposed so as to surround the pile head 12 with a predetermined space. The peripheral wall 114 is disposed to collectively surround the joint member inner portions 20 a of the plurality of joint members 14 and the plurality of reinforcing bars 16, and the inside of the joint members of the plurality of joint members 14 and the plurality of reinforcement bars 16 One partition wall 116 disposed laterally of the portion 20a is configured.

  According to the pile head joint portion 100 b described above, the adhesion portion 110 of the base concrete portion 4 and the base concrete portion 4 in the radial direction of the reinforcing bars 16 by the peripheral wall 114 arranged to surround the pile head 12. The connection between the distal portion 112 can be blocked in a simple configuration.

Preferably, as shown in FIGS. 41 to 43, the partition member 102b has an annular plate 118 connected to the upper end of the peripheral wall 114 and disposed along the end face of the pile head 12. The annular plate 118 has a plurality of openings 120 through which the reinforcing bars 16 are inserted.
According to the above configuration, by arranging the annular plate 118 on the end face of the pile head 12, the partition wall 116 can be easily arranged. Note that, for example, the partition member 102b can be easily fixed to the pile head 12 by fixing the annular plate 118 to the pile head 12 with a bolt (not shown).

  Finally, the method for designing a pile head joint according to the above-described embodiment is an invention related to a method, but according to the present invention, a program for causing a computer to execute the method is also provided as an invention of a product. Of course it is possible.

DESCRIPTION OF SYMBOLS 1 Structure 2 Pile 4 Foundation concrete part 4a Pile cap 5 Beam 6 Superstructure 8 Pile foundation 10, 100a, 100b Pile head joint 12 Pile head 14 Joint member (joint coupler)
DESCRIPTION OF SYMBOLS 16 Reinforcement line 17 Concrete part 18 End plate 19 Outer shell steel pipe 20 Shaft part 20a Joint member inner part 21 Screw part 22 Fixing body 23 Lower side projection 24 Upper side projection 26 Screw hole 28 Notch 29 Fork part 30 Connection part 32 Reinforcement Beam portion 34 Reinforcement rib portion 35 Curved surface 36 Groove surface 38 Weld bead 40 Upper portion 42 Lower portion 44 Crack 50 Horizontal force testing device 51 Actuator 52 Crack 102a, 102b Partition member 104 First side wall 106 Second side wall 108 Partition Wall 110 attached part (proximal part)
112 distal portion 114 peripheral wall 116 partition wall 118 annular plate 120 opening

Claims (8)

With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The shaft portion of the reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head and protrudes upward from the end face of the pile head ,
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that a crack occurs between the part of the foundation concrete part surrounding the part,
While considering the tensile yield strength of the shaft portion of the reinforcing bar, the allowable bending moment is calculated by disregarding the resistance acting on the base concrete portion from the joint member How to design. With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that no cracks occur between the part of the foundation concrete part surrounding the part,
In addition to taking into consideration the tensile yield strength of the screw portion of the reinforcing bar, the allowable bending moment is calculated in consideration of the resistance acting on the foundation concrete portion from the joint member. How to design. With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion continuous with the lower end side of the shaft portion and having a cross-sectional area smaller than that of the shaft portion;
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation process,
A first allowable bending moment as the allowable bending moment is calculated in consideration of the tensile yield strength of the screw portion of the reinforcing bar and the resistance acting on the base concrete portion from the joint member. Bending moment calculation process,
A second allowable bending moment is calculated as the allowable bending moment while ignoring the resistance acting on the base concrete portion from the joint member while taking into consideration the tensile yield strength of the shaft portion of the reinforcing bar. Bending moment calculation process,
An allowable bending moment selecting step of comparing the first allowable bending moment and the second allowable bending moment and selecting the smaller one of the first allowable bending moment and the second allowable bending moment as the allowable bending moment; A method of designing a pile head joint characterized by including. In the allowable bending moment selection step, when the yield strength of the upper projection is smaller than the difference between the tensile yield strength of the shaft and the tensile yield strength of the screw, the first allowable bending moment is the allowable bending. 4. A method as claimed in claim 3, characterized in that it is selected as a moment. In the allowable bending moment calculation step,
The resistance bending moment of the reinforcing bars protruding upward from the end of the pile head and the foundation concrete part surrounding the reinforcing bars is assumed to be the bending moment that is imposed by the virtual RC section including the end face of the pile head,
The diameter of the pile head is Dp,
Let D be the diameter of the virtual RC section,
Assuming that the length of the foundation concrete portion adhering to the shaft portion of the reinforcing bar is Le between the lower projection and the upper end of the upper projection in the axial direction of the pile head as follows:
Dp + Le ≦ D ≦ Dp + 2Le
The diameter D of the said virtual RC cross section is set and calculated so that the relationship represented by these may be satisfy | filled, The design method of the pile-head junction in any one of the Claims 1 to 4 characterized by the above-mentioned. With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The shaft portion of the reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head and protrudes upward from the end face of the pile head ,
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that a crack occurs between the part of the foundation concrete part surrounding the part,
While considering the tensile yield strength of the shaft portion of the reinforcing bar, the allowable bending moment is calculated by disregarding the resistance acting on the base concrete portion from the joint member Permissible bending moment calculation method. With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion having a cross-sectional area smaller than that of the shaft portion.
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation step,
A portion of a foundation concrete portion surrounding a portion of a shaft portion of the reinforcing bar projecting upward from an end face of the pile head, and a shaft portion of the reinforcing bar extending between the lower projection and the upper projection Assuming that no cracks occur between the part of the foundation concrete part surrounding the part,
In addition to taking into consideration the tensile yield strength of the screw portion of the reinforcing bar, the allowable bending moment is calculated in consideration of the resistance acting on the foundation concrete portion from the joint member. Permissible bending moment calculation method. With a pile head,
A plurality of joining members fixed to the outer peripheral surface of the pile head;
A plurality of reinforcing bars each attached to the pile head via the joint member;
The pile head, the plurality of joint members, and a foundation concrete part made of concrete surrounding the plurality of reinforcement bars,
The reinforcing bar is
A shaft having irregularities on the surface,
And a screw portion continuous with the lower end side of the shaft portion and having a cross-sectional area smaller than that of the shaft portion;
The joining member is
A lower projection fixed to the outer peripheral surface of the pile head;
An upper protrusion fixed to the outer peripheral surface of the pile head, the upper protrusion being disposed above the lower protrusion in the axial direction of the pile head;
The threaded portion of the reinforcing bar is coupled to the lower projection,
The reinforcing bar extends between the lower projection and the upper projection in the axial direction of the pile head, and extends upward from the end face of the pile head.
In the design method of the pile head joint,
An allowable bending moment calculating step of calculating an allowable bending moment of the pile head joint,
In the allowable bending moment calculation process,
A first allowable bending moment as the allowable bending moment is calculated in consideration of the tensile yield strength of the screw portion of the reinforcing bar and the resistance acting on the base concrete portion from the joint member. Bending moment calculation process,
A second allowable bending moment is calculated as the allowable bending moment while ignoring the resistance acting on the base concrete portion from the joint member while taking into consideration the tensile yield strength of the shaft portion of the reinforcing bar. Bending moment calculation process,
An allowable bending moment selecting step of comparing the first allowable bending moment and the second allowable bending moment and selecting the smaller one of the first allowable bending moment and the second allowable bending moment as the allowable bending moment; The allowable bending moment calculation method of a pile head joint characterized by including.

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