JP5036065B2 - Pile head joint structure - Google Patents

Description

  The present invention relates to a joint structure between a foundation concrete structure portion of a building such as a footing or a lowermost slab and a pile head portion of a ready-made concrete pile. In particular, it is related with the joining structure with the hollow ready-made concrete pile which equips an end plate with a pile head end surface.

Known hollow concrete piles include centrifugal high-strength prestressed concrete piles (PHC piles), prestressed reinforced concrete piles (PRC piles), concrete piles with shell steel pipes (SC piles), and the like. In this type of hollow prefabricated concrete pile connection structure, it is connected to the foundation concrete structure part of the building via a pile head rebar with the lower part fixed to the pile head end plate provided on the pile head end face of the ready made concrete pile. The joining structure is widely known. In that case, a semi-rigid joint is also known in which a non-fixed portion that does not adhere to surrounding concrete is formed on a part of a pile head reinforcing bar (Patent Document 1). And, according to this semi-rigid joint structure, the degree of fixation of the pile head is reduced by the deformation of the pile head rebar in the non-fixed part, and the bending moment generated in the pile head is reduced. The effect that damage can be suppressed is also known.
JP 2000-144663 A

  By the way, in the case of a general joint form in which the concrete that constitutes the foundation concrete structure abuts against the end plate of the pile head, the tensile force against the bending moment acting on the pile head The pile head rebar resists, and the pile head rebar and concrete resist the compressive force. That is, the foundation concrete structure part above the end plate has a large resistance to vertical compression deformation. This resistance force against compressive deformation has a great influence on the behavior of the pile head joint, particularly the rotational deformation of the pile head joint. On the other hand, a structure is generally supported by multiple piles, and the axial force acting on each pile during an earthquake etc. varies depending on the installation position of each pile. Exists. In this way, the axial force on individual piles acting in the event of an earthquake, etc. fluctuates, and because of the influence of the restraining action on the compression direction from the concrete, the problem is that the fixing degree of each pile head, that is, the rotational rigidity, fluctuates. There was a serious technical problem. For this reason, the strength design of the building is extremely complex, and it becomes an enormous and complicated design work when trying to respond by changing the cross-sectional shape of the pile head individually considering the situation of each pile head, In addition, there is a problem that workability is greatly reduced.

  In view of the above-described conventional technical situation, the present invention reduces the restraining action by the concrete constituting the foundation concrete structure part, reduces the fluctuation of the rotational rigidity of the pile head due to the axial force, etc. The purpose is to provide a pile head joint structure that is effective in suppressing the effects of fluctuations in axial force and improving workability when dealing with individual pile head situations. It is.

In order to solve the above-mentioned problems, in the invention of claim 1, the foundation concrete structure part of the building and the pile head part of the ready-made concrete pile are formed using a plurality of pile head reinforcing bars whose lower end parts are fixed to the pile head end plate. In the pile head joining structure to be joined, a plurality of steel sleeves are disposed on the pile head end plates so as to be fitted on the pile head reinforcing bars, and above the pile head end plates on the steel sleeves. A steel plate is placed so as to cover the steel plate, and the steel sleeve holds a distance between the pile head end plate and the steel plate, and the steel sleeve compresses the pile head by acting on the pile head. The technical means of reinforcing the pile head rebar by sharing the above was adopted . As the following, the invention of claim 1, by forming the gap portion downwardly by a steel plate, while eliminating the restraint effect of the concrete for the pile head, depending on the steel sleeves pile It has the feature that the technical means of reinforcing the pile head rebar by sharing the compressive load acting on the part is adopted. That is, the formation of the void portion eliminates the restraining action from the concrete, reduces the fluctuation in the rotational rigidity of the pile head due to the axial force, suppresses the influence due to the fluctuation of the axial force during an earthquake, etc. having said compressive load on pile rebar be increased by forming at the points so as to reinforce the pile head rebar by relaxing and thus shared by the steel sleeves. The outer diameter of the steel plate is set to be substantially the same as the outer diameter of the ready-made concrete pile, for example (Claim 2 ).

Moreover, in invention of Claim 3 , while arrange | positioning several steel sleeves in the state externally fitted to the said pile head reinforcement on the said pile head end plate, obstruct | occlude the upper part of those steel sleeves, A technical means was adopted in which a void portion into which concrete does not flow was formed inside the steel sleeve, and the inside of the steel sleeve was used as a non-fixing portion. Further, in the invention of claim 4, a plurality of spacers made of foamed polystyrene or the like are disposed on the pile head end plate so as to be externally fitted to the pile head reinforcing bars, and the pile heads are formed by these spacers. The technical means of forming the non-fixed part at the lower part of the reinforcing bar and forming the part excluding the concrete around each non-fixed part was adopted. As mentioned above, in invention of Claim 3 and Claim 4 , by installation of the steel sleeves and spacers externally fitted to the respective pile head rebars, the lower portions of the pile head rebars are formed by those steel sleeves and spacers. By individually forming the part where the concrete is excluded around the formed non-fixed part, the contact area between the concrete and the pile head end face is reduced as a whole, and the fluctuation of the rotational rigidity of the pile head due to the axial force is reduced. It is characterized in that it employs technical means to reduce and suppress the effects of fluctuations in axial force during earthquakes. In other words, because the Young's modulus ratio of the reinforcing steel and steel sleeve to the concrete is large, even if the contact area of the concrete to the pile head end plate is slightly reduced, the proportion of load on the pile head reinforcing steel and steel sleeve increases. The influence by can be reduced.

According to the present invention, the following effects can be obtained.
(1) According to the present invention, the restraining action from the concrete on the pile head can be eliminated or reduced, so the fluctuation of the rotational rigidity of the pile head due to the axial force can be reduced, and the influence of the fluctuation of the axial force during an earthquake, etc. Can be suppressed.
(2) According to the first and second aspects of the invention, the constraining action of the concrete against the pile head can be effectively eliminated or reduced by the lower wide gap formed by the steel plate.
(3) Moreover, the pile head reinforcement is reinforced by sharing the compression load acting on Therefore pile head on the steel sleeves, that can reduce the impact of compressive load against the pile rebar be increased by forming the air gap Therefore, a well-balanced pile head joint structure can be obtained.
(4) Further, by changing the thickness or the like of the steel sleeves, since that can be conveniently performed action appropriate to the situation of each pile head, it is also very effective in improving the workability.
(5) In addition, to eliminate the restraint effect of the concrete for the pile head, from undergoing Therefore compressive force to the pile head rebar and steel sleeves, it facilitates the analysis of the behavior, simplifies design work Is also very effective.
(6) According to the inventions of claims 3 and 4 , in the installation work of the pile head reinforcing bars, the concrete sleeves and the spacers are individually fitted to the individual pile head reinforcing bars, thereby making the concrete and the concrete as a whole. The contact area with the pile head end face can be reduced to reduce the fluctuation of the rotational rigidity of the pile head due to the axial force. It is good.

The present invention is a pile head joint structure that joins a foundation concrete structure part of a building and a pile head of a ready-made concrete pile using a plurality of pile head reinforcing bars whose lower end part is fixed to the pile head end plate. Can be widely applied. As described above, by covering the top of the pile head end plate using a steel plate, even those with a form that eliminates or reduces the restraining action from the concrete on the pile head is externally fitted to each pile head rebar. By excluding concrete for each pile head rebar with a steel sleeve or spacer, it is possible to implement a configuration that reduces the concrete restraining action on the pile head. Further, regarding the fixing form of the pile head reinforcement to the foundation concrete structure part, it may be based on the adhesive force of the shaft part as in the following examples, or it is fixed by the fixing plate attached to the upper part and unbonded to the shaft part. A configuration in which a sheath tube or the like is externally fitted is also applicable. The steel plate may be a disk-shaped one or a ring-shaped one installed along the pile head end plate so as to cover the top of the pile head end plate. Further, the outer diameter of the steel plate is preferably substantially the same as the outer diameter of the pile head and covers the entire top of the pile head end plate, thereby eliminating the concrete restraining action on the pile head. The form which reduces the restraining action of concrete is also possible by partially covering the upper part of the pile head end plate. By the way, for this steel plate, it is configured so that the cast concrete does not flow below the steel plate by providing blocking means such as attaching a hanging ring member to the outer peripheral edge if necessary. To do. Regarding the steel sleeves are depending on the degree of reinforcement for the pile head reinforcement, we will specifically selected such thickness and material strength suitable for sharing compressive load acting on the pile head. Further, as mentioned above, by selecting and thickness and material strength of the steel sleeves in each pile head, corresponding it can also be conveniently carried out according to the situation of each pile head.

  1 and 2 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view showing an installed state, and FIG. 2 is an AA sectional view of the pile head. In the figure, 1 is a hollow ready-made concrete pile, and 2 is a pile head end plate installed on the upper end surface of the pile 1. As shown in the drawing, a plurality of pile head rebars 3 are erected on the pile head end plate 2 in a state where the lower end portions are fixed by screw connection or welding. Further, a steel sleeve 4 is fitted on each pile head reinforcing bar 3, and a disk-shaped steel plate 5 is placed on the steel sleeve 4, and the pile head is placed by the steel sleeve 4. By maintaining a gap between the end plate 2 and the steel plate 5, the gap 6 is formed. Male thread portions are formed at the bottom of each pile head rebar 3, and the steel plate 5 and the steel sleeve 4 are fastened to the pile head end plate 2 by a circular nut 7 screwed into these male thread portions. It is configured to be fixed. In the figure, reference numeral 8 shows a foundation concrete structure such as a footing or a bottom slab to be placed later, and in this embodiment, between the foundation concrete structure 8 and each pile head rebar 3. The foundation concrete structure portion 8 and the pile head portion of the ready-made concrete pile 1 are joined by the fixing force based on the adhesion force. Note that 9 in FIG. 2 is a fixing member made of a PC steel strand or the like installed adjacent to the installation position of each pile head rebar 3 in order to fix the pile head end plate 2 to the upper end surface of the pile 1. It is shown.

  Thus, when an external force is applied due to an earthquake or the like, the gap 6 is formed above the pile head end plate 2, so that the restraining action from the concrete constituting the foundation concrete structure portion 8 with respect to the pile head is It will be resolved. Therefore, the compression load in a present Example is shared by each pile head reinforcement 3 and the steel sleeve 4 externally fitted by them. Regarding the tensile load, when the steel sleeve 4 and the pile head rebar 3 are integrally coupled, the tensile load is shared by both members, but the steel sleeve 4 is simply connected to the pile head rebar. When the steel sleeve 4 is merely fitted externally to the steel plate 3, the steel sleeve 4 does not resist the tensile load. Incidentally, as described above, by selecting the material and the plate thickness of the steel sleeve 4, it is possible to easily carry out individual measures corresponding to individual load situations acting on the respective pile heads. By the way, in the case of a present Example, when the said foundation concrete structure part 8 is laid, the inflow of the concrete between the pile head reinforcing bars 3 below the steel plate 5 is prevented, and the said space | gap part 6 is formed. It is important to. For this reason, as described above, appropriate blocking means such as attaching a hanging ring member to the outer peripheral edge of the steel plate 5 as necessary is provided, and the cast concrete does not flow below the steel plate. It will be configured as follows.

3 and 4 show a second embodiment of the present invention. FIG. 3 is a longitudinal sectional view showing an installation state, and FIG. 4 is a sectional view taken along the line BB of the pile head. As shown in the figure, even in the case of the present embodiment, the pile head end plate 2 installed on the upper end surface of the hollow ready-made concrete pile 1 is fixed to the pile head end plate 2 by screw coupling, welding, or the like. There is no difference from the case of the first embodiment in that the head rebar 3 is erected. In the case of the present embodiment, a plurality of steel sleeves 10 are disposed in a state of being externally fitted to the pile head rebar 3, and the steel plates 5 are not used, and upper portions of the steel sleeves 10 are not used. It is characterized in that the gaps 12 are individually formed inside each steel sleeve 10 by tightening and fixing the opening in a state of being closed by the circular nut 11 . And in the case of a present Example, as shown in FIG. 4 , the contact area of the concrete with respect to the pile head end plate 2 can be reduced by the part of the space | gap part 12 formed in the inside of each steel sleeve 10. FIG. This can reduce the restraining action by the concrete and reduce the fluctuation of the rotational rigidity of the pile head due to the axial force, so that the steel sleeve 10 can be easily fitted to each pile head rebar 3. It is possible to suppress the influence due to the fluctuation of the axial force during an earthquake or the like by simple work. Incidentally, regarding the steel sleeve 10 according to the present embodiment, it may be configured to reinforce the pile head rebar 3 by setting the strength of the steel sleeve 10 large and sharing the compression load, On the contrary, it is possible to set the strength to be weak and not share the compressive load, but simply use it as a means for forming the gap 12 inside. Although not shown, since the hollow portion of the ready-made concrete pile 1 including the third embodiment to be described later is filled with earth and sand to the vicinity of the pile head after placing, when constructing the foundation concrete structure 8 There is no need to provide concrete flow-down prevention means (such as formwork).

5 and 6 show a third embodiment of the present invention. FIG. 5 is a longitudinal sectional view showing an installation state, and FIG. 6 is a CC sectional view of the pile head. As shown in the figure, even in the case of the present embodiment, the pile head end plate 2 installed on the upper end surface of the hollow ready-made concrete pile 1 is fixed to the pile head end plate 2 by screw coupling, welding, or the like. There is no difference from the case of the second embodiment in that the head rebar 3 is erected. In the case of the present embodiment, instead of the steel sleeve 10 , a plurality of spacers 13 made of foamed polystyrene or the like that are weak against compressive force are externally fitted to each pile head rebar 3, so In addition to forming non-fixed portions, each of the non-fixed portions is characterized in that a portion from which concrete is excluded is individually formed. And in the case of a present Example, as shown in FIG. 6 , the contact area of the concrete with respect to the pile head end plate 2 can be reduced only by the installation part of the spacer 13 , thereby reducing the restraining action by concrete. Since the fluctuation of the rotational rigidity of the pile head due to the axial force can be reduced, the simple operation of externally installing the spacer 13 on each pile head rebar 3 enables the fluctuation of the axial force during an earthquake or the like. It is possible to suppress the influence.

It is the longitudinal cross-sectional view which showed the installation state of 1st Example of this invention. It is AA sectional drawing of the pile head of the Example. It is the longitudinal cross-sectional view which showed the installation state of 2nd Example of this invention. It is BB sectional drawing of the pile head of the Example. It is the longitudinal cross-sectional view which showed the installation state of 3rd Example of this invention. It is CC sectional drawing of the pile head of the Example.

1: ready-made concrete pile, 2: pile head end plate, 3: pile head rebar, 4: steel sleeve, 5: steel plate, 6: gap, 7: circular nut, 8: foundation concrete structure, 9: Fixing member, 10 : steel sleeve, 11 : circular nut, 12 : gap portion, 13 : spacer

Claims (4)

  In a pile head joint structure in which a foundation concrete structure part of a building and a pile head part of a ready-made concrete pile are joined using a plurality of pile head rebars whose lower ends are fixed to the pile head end plate, the pile head end plate A plurality of steel sleeves are disposed in a state of being externally fitted to the pile head reinforcing bars, and a steel plate is placed on the steel sleeves so as to cover the top of the pile head end plates, and the steel The spacing between the pile head end plate and the steel plate is maintained by the sleeve, and the pile head reinforcement is reinforced by sharing the compressive load acting on the pile head by the steel sleeve. Pile head joint structure characterized by The pile head joint structure according to claim 1, wherein an outer diameter of the steel plate is substantially the same as an outer diameter of the ready-made concrete pile.   In a pile head joint structure in which a foundation concrete structure part of a building and a pile head part of a ready-made concrete pile are joined using a plurality of pile head rebars whose lower ends are fixed to the pile head end plate, the pile head end plate A plurality of steel sleeves are arranged in a state of being externally fitted to the pile head reinforcing bars, and the upper portions of the steel sleeves are closed to form a void portion in which no concrete flows into each steel sleeve. And a pile head joint structure characterized in that the inside of the steel sleeve is a non-fixed portion.   In a pile head joint structure in which a foundation concrete structure part of a building and a pile head part of a ready-made concrete pile are joined using a plurality of pile head rebars whose lower ends are fixed to the pile head end plate, the pile head end plate A plurality of spacers that are weak to compressive force made of foamed polystyrene or the like are disposed in a state of being externally fitted to the pile head reinforcement, and non-fixed portions are formed at the lower portion of the pile head reinforcement by the spacers. Pile head joint structure characterized in that it is configured to form a part that excludes concrete around the fixing part.

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