JP4214029B2 - Low-fixation pile head joint structure - Google Patents

Description

  The present invention relates to a low-fixed pile head joint structure that prevents breakage at a pile head.

  As a method of joining a pile head and a foundation of a ready-made concrete pile, there is known a construction method in which a plurality of steel bars are welded or screwed on an end steel plate of a ready-made concrete pile.

  For example, in Patent Document 1, in a pile head joint structure in which a male screw portion formed at a lower end portion of a reinforcing bar is screwed into a female screw hole formed in a pile head end plate, an outer peripheral surface is formed in a polygonal shape, and an inner peripheral surface is There is described a pile head joint reinforcing bar reinforcing structure in which a cylindrical member that surrounds a reinforcing bar is formed in a substantially upper half part and a reinforcing member in which a screw groove that is screwed into the male screw part is formed in a substantially lower half part.

  The reinforcing structure described in Patent Document 1 makes it difficult to bend the base of a reinforcing bar with a reinforcing member, and aims to improve earthquake resistance against breakage due to buckling or the like as expected when a large earthquake occurs.

  However, in the above-mentioned reinforcement structure, the foundation slab, which is considered to be an infinitely rigid rigid body, and the pile head are fixed (rigidly connected), so a large horizontal force acts on the pile head during the earthquake depending on the building. As a result, a large bending moment is applied, and damage may concentrate on the pile head. In particular, the pile head is also a part that is difficult to repair later, and the occurrence of damage to this part may cause a serious situation.

  As a pile head joint structure for solving the above problem, for example, in Patent Document 2, a damper material is provided around a stud standing on the upper surface of a pile head end plate, and the stud with the damper material is provided as a foundation slab. A so-called “low-fixed pile head joint structure” is described in which the pile head is semi-fixed (intermediate between the pile head fixation and the pin) by being embedded inside.

Japanese Patent No. 2922834 JP 2000-336665 A

  According to the pile head joint structure described in Patent Document 2, when a displacement action is applied between the pile and the foundation slab in response to an earthquake or the like, the stud is displaced in the damper material, and the pile head or foundation slab Damage and destruction can be prevented.

  However, in the above structure, the displacement of the stud is limited to a narrow displacement range of the damper material, and in particular, the vertical displacement action due to the lifting of the upper structure during an earthquake is not sufficiently considered.

  In recent years, a building with a seismic isolation device interposed between the foundation and the base has been proposed. However, this building with a seismic isolation device requires a special seismic isolation device, which increases costs.

  In view of the above problems, the present invention provides a novel pile head joint structure capable of preventing damage and destruction of a pile head and an upper structure.

  As a result of intensive studies to solve the above problems, the present inventor has found that the following pile head joint structure is optimal.

That is, the present invention, the steel rods (stud) erected through hole which is opened in pile head end plate, a pile joint structure disposed the embedded steel bars in a basis such as footings, the pile Is a prestressed concrete pile, the through-hole is a screw hole for a tension bolt used when pre-stress is introduced, and the steel bar has an enlarged portion larger than the through-hole at the lower end, and the enlarged portion is A low-fixation pile head joint structure characterized in that it is erected in a state of being separated from the lower side of the end plate and from the lower surface of the end plate.

The low fixed degree pile head joint structure of the present invention is further characterized as:
“There is a gap between the enlarged portion and the end plate, and a cushioning material is disposed in the gap.”
"The enlarged portion is a nut-like member, having a structure in which a steel rod attached to the nut-like member having a male screw portion",
Including the.

  According to the low-fixed pile head joint structure of the present invention, since the uplift of the superstructure during an earthquake is allowed until the enlarged part of the steel bar reaches the lower surface of the pile head end plate, the stress on the pile head This can effectively prevent damage and destruction of the pile head and the superstructure.

  The greatest feature of the low-fixation pile head joint structure of the present invention is that a steel rod having an enlarged portion larger than the through hole established in the pile head end plate of a ready-made concrete pile is used. The structure is such that the steel rod is vertically erected in a state of being spaced apart from the lower surface of the end plate and allows the vertical displacement of the steel bar until the enlarged portion reaches the lower surface of the pile head end plate.

  Hereinafter, specific embodiments of the low-fixation pile head joint structure of the present invention will be described, but the present invention is not limited to these embodiments, and each member within the scope of the gist of the present invention. Etc. are allowed.

(First embodiment)
The low fixed degree pile head joint structure of this example is demonstrated using FIG. 1 thru | or FIG. FIG. 1 is a top view of a ready-made concrete pile and represents a pile head end plate. FIG. 2 is an elevational sectional view showing the pile head joint structure. FIG. 3 is a cross-sectional view taken along the plane AA ′ in FIG.

  1 to 3, 10 is a pile body (ready-made concrete pile), 11 is a pile head end plate, 12 is a through hole formed in the pile head end plate, 13 ′ is a PC steel wire through hole, and 13 is PC steel. Reference numeral 14 denotes a steel bar (stud), 15 denotes an enlarged portion of the steel bar, 16 denotes a cylindrical body, 17 denotes a shielding plate, and 20 denotes a base such as a footing.

  The pile body 10 of this example is a long cylindrical ready-made hollow concrete pile, specifically, a pretension type centrifugal force high strength prestressed concrete pile (PHC pile). The pile head joint structure of the present invention can be applied not only to PHC piles but also to PRC concrete piles or SC piles.

  A pile head end plate 11 is fixed to an end portion of the pile body 10, and a plurality of through holes 12 are formed in the pile head end plate 11. As will be described in detail later, the through-hole 12 of this example is also a screw hole for a tension bolt used when pre-stress is introduced. For this reason, it is not necessary to prepare a special end plate, and the manufacturing cost increase of a pile can be prevented.

  As shown in FIG. 2 and FIG. 3, the low-fixation pile head joint structure of this example is a joint structure in which a steel rod 14 is erected through the through hole 12 and this steel rod 14 is embedded in a foundation 20. It has become. The steel bar 14 has an enlarged portion 15 larger than the through-hole 12 at the lower end, and the enlarged portion 15 is erected in a state of being separated from the lower surface of the pile head end plate 11. Further, the steel rod 14 and the enlarged portion 15 below the pile head end plate 11 are accommodated in the tubular body 16 and insulated from the concrete of the pile body 10.

  Due to the structural features described above, in the low-fixed pile head joint structure of this example, the floating portion 15 of the steel bar 14 is caused to lift up the upper structure (foundation 20) during an earthquake as shown in FIG. It is permissible until the lower surface of the pile head end plate 11 is reached. 4A is a sectional view in the same direction as FIG. 3, and FIG. 4B is a sectional view in the orthogonal direction.

  The distance from the lower surface of the pile head end plate 11 to the enlarged portion 15 is appropriately designed in consideration of the vertical shape due to the uplift of the upper structure during an earthquake, considering the planar shape and height of the upper structure. Is preferred.

  Specifically, the low fixed degree pile head joint structure of this example is realized as shown in FIG. 5, for example. 5 is a cross-sectional view corresponding to FIG.

  In manufacturing the pile body 10, first, as shown in FIG. 5A, the male threaded portion 53 of the tension bolt 52 is screwed into the through hole (screw hole) 12 of the pile head end plate 11 via the tension plate 51. The tension bolt 52 further has a shaft portion 54 and a male screw portion 55 having a predetermined length in front of the male screw portion 53. Next, the nut-like member 15 serving as the above-described enlarged portion is screwed and fixed to the male screw portion 55 at the lower end of the tension bolt. Next, the tension bolt 52 and the nut-like member 15 are surrounded, and the cylindrical body 16 is provided in contact with the lower surface of the pile head end plate 11.

  The nut-like member 15 of this example is not circular but rectangular, the short side is about the same as the diameter of the through hole 12, and the long side is larger than the diameter of the through hole 12.

  Next, after applying the tension force in the direction of the arrow in the drawing via the tension plate 51 and the tension bolt 52 and centrifugally forming the pile body 10 with the PC steel wire 13 being tensioned, the tension plate 51 and the tension bolt 52 are Remove. At this time, since the nut-like member 15 is rectangular, the tension bolt 32 can be easily and reliably removed without rotating together. Then, as shown in FIG. 5B, a structure in which the nut-like member 15 is disposed away from the lower surface of the pile head end plate 11 in a state where the nut-like member 15 is accommodated in the cylindrical body 16 is completed.

  After the pile body 10 having the above structure is buried in the ground by a conventionally known method, a steel rod 14 having a male threaded portion at the tip is passed through a through hole 12 and a nut-like member as shown in FIG. A shielding plate 17 that shields the through hole 12 is disposed while being screwed to 15. Also at this time, the nut-like member 15 does not rotate together, and the steel rod 14 can be easily and reliably attached to the nut-like member 15. Then, by constructing a foundation 20 such as a footing on the top of the pile body 10, a pile head joint structure in which the steel bar 14 is embedded and arranged in the foundation 20 is completed.

  Note that the steel rod 14 of this example has a smaller diameter than the through-hole 12, and a predetermined gap is formed between the steel rod 14 and the pile head end plate 11. When the foundation 20 is constructed, the shielding plate 17 prevents the concrete from entering the gap portion between the enlarged portion 15 of the steel bar 14 and the pile head end plate 11 from the gap.

  As described above, in the low fixed degree pile head joint structure of the present example, by allowing the upper structure to lift during the earthquake until the enlarged portion 15 of the steel bar 14 reaches the lower surface of the pile head end plate 11, It is possible to reduce stress on the pile head and effectively prevent damage and destruction of the pile head and the superstructure.

  Further, by designing the diameter of the through-hole 12 to be larger than that of the steel bar 14 as in this example, the through-hole 12 is kept until the steel bar 14 comes into contact with the pile head end plate 11 as shown in FIG. It is possible to displace the inside of the pile, and it is possible to more effectively prevent damage and destruction of a foundation such as a pile head or footing.

  As is clear from the description of this example, the “expanded part of the steel bar” in the present invention is not only a part processed directly on the steel bar itself, but also a member of a predetermined size at the end of the steel bar. When (the nut-like member 15) is attached, this member is indicated.

(Second Embodiment)
In this example, as shown in FIG. 7, an example in which a coil spring 71 is disposed as a cushioning material in a gap formed between the enlarged portion 15 of the steel bar 14 and the pile head end plate 11 in the first embodiment. FIG. 7A shows a normal state, and FIG. 7B shows a state at the time of displacement.

  In the low-fixed pile head joint structure of this example, by absorbing the impact when the enlarged portion 15 of the steel rod 14 abuts the pile head end plate 11 due to the lifting of the upper structure during an earthquake by the coil spring 71, It is possible to effectively prevent the steel bar enlarged portion or the pile head end plate from being broken.

  In the present invention, the cushioning material is not limited to a coil spring, and other spring materials such as a leaf spring, and further elastic rubber can be used.

(Third embodiment)
The low fixed degree pile head joint structure of this example is shown in FIG. FIG. 8A is a top view of a ready-made concrete pile. FIG.8 (b) is sectional drawing in the BB 'surface in Fig.8 (a), and represents the pile head junction structure.

  The difference from the first and second embodiments is that a reinforcing member is provided at the pile head portion. If a gap is formed between the enlarged portion 15 of the steel bar 14 and the pile head end plate 11 as in the previous embodiment, the strength of the pile head portion in the axial direction may be insufficient. For this reason, it is preferable to provide the reinforcing steel bar 81 and / or the reinforcing steel pipe 82 so as to cover at least the gap forming region of the pile head as shown in the figure. Thereby, damage and destruction of a pile head can be prevented very effectively.

(Fourth embodiment)
In the embodiment described above, an enlarged portion (the aforementioned nut-like member 15) larger than the through-hole previously opened in the pile head end plate at the time of manufacturing the pile body is embedded in the pile body, In this example, a predetermined space is formed below the through hole of the pile head end plate, and a predetermined size is formed in this space. An example of standing a steel rod having an enlarged portion of is shown.

  FIG. 9 is a cross-sectional view corresponding to FIG. 3, (a) shows the structure of the pile body, and (b) shows a state where a steel bar is erected on the pile body.

  When manufacturing the pile body 10, for example, by centrifugally forming a pad of a predetermined length through a through hole (screw hole) 12 of the pile head end plate 11 and then removing the padding, FIG. As shown, a space 91 having a predetermined length substantially the same diameter as the through hole 12 is formed under the through hole 12. As the stuffing, a material that does not deform during centrifugal molding and can be easily removed, for example, a hard foamed plastic or the like is preferable. In addition, if this padding is removed after pile body embedding, it can serve as curing of the through-hole 12.

  Then, after the pile body 10 is buried in the ground, the steel rod 14 having the enlarged portion 15 having substantially the same diameter as the through hole 12 is erected in the space 91 through the through hole 12. At this time, as shown in FIG. 9 (b), the steel rod 14 is passed through a perforated nut 92 having a hole having substantially the same diameter as the steel rod 14, and the perforated nut 92 is screwed into the through-hole 12. Thus, the same structure as the previous example can be realized.

  In the low-fixed pile head joint structure of this example, by allowing the uplift of the superstructure during an earthquake until the enlarged portion 15 of the steel bar 14 reaches the lower surface of the perforated nut 92, Stress can be reduced and damage and destruction of the pile head and superstructure can be effectively prevented.

  Moreover, in the case of this example, manufacture of the pile body 10 is simplified, and the standing work of the steel rod after the pile body is laid is facilitated, and there is a great merit in terms of manufacturing and construction of the pile. is there.

  As is clear from the description of the present example, the “through hole formed in the pile head end plate” in the present invention is not limited to the opening directly formed in the pile head end plate itself (the through hole 12). When the member (the perforated nut 92) further having a through hole is fixed and attached to the opening (the through hole 12) formed in the pile head end plate itself as described above, the transparent member has such a through hole. Refers to the hole.

It is a top view of the ready-made concrete pile concerning the example of 1st Embodiment of this invention, and represents the pile head end plate. It is an elevation sectional view showing the low fixed degree pile head joining structure concerning the 1st example of an embodiment of the present invention. It is sectional drawing in the A-A 'surface in FIG. 1, and is an expanded sectional view which shows the characteristic part of the pile head junction structure which concerns on the 1st Example of this invention. It is explanatory drawing of the effect in the low fixed degree pile head junction structure which concerns on the 1st Example of this invention. It is explanatory drawing of the construction procedure of the low fixed degree pile head joint structure which concerns on the 1st Example of this invention. It is explanatory drawing of the effect in the low fixed degree pile head junction structure which concerns on the 1st Example of this invention. It is explanatory drawing of the effect in the low fixed degree pile head joining structure which concerns on the 2nd Example of this invention. It is explanatory drawing of the example of 3rd Embodiment of this invention, (a) is a top view of a ready-made concrete pile, (b) is sectional drawing in the BB 'surface in (a), and a pile head junction structure Represents. It is explanatory drawing of the example of 4th Embodiment of this invention, (a) shows the structure of a pile body, (b) has shown the state which stood the steel bar in the pile body.

Explanation of symbols

10 Pile bodies (ready-made concrete piles)
11 Pile head end plate 12 Through hole 13 PC steel wire 13 'PC steel wire through hole 14 Steel rod (stud)
DESCRIPTION OF SYMBOLS 15 Expanded part of steel bar 16 Cylindrical body 17 Shielding board 20 Foundation slab 51 Tension plate 52 Tension bolt 53 Male thread part 54 Shaft part 55 Male thread part 71 Coil spring 81 Reinforcement reinforcement 82 Reinforcement steel pipe 91 Space 92 Perforated nut

Claims (3)

A pile head joint structure in which a steel rod is erected through a through hole established in a pile head end plate, and the steel rod is embedded in a foundation such as a footing,
The pile is a prestressed concrete pile, and the through hole is a screw hole for a tension bolt used when prestress is introduced,
The steel bar has an enlarged portion larger than the through hole at a lower end thereof, and the enlarged portion is erected in a state of being separated from the lower side of the end plate and from the lower surface of the end plate. Fixed pile head joint structure.   The low-fixation pile head joint structure according to claim 1, wherein a gap is provided between the enlarged portion and the end plate, and a cushioning material is disposed in the gap.   3. The low-fixation pile head joint structure according to claim 1, wherein the enlarged portion is a nut-like member and has a structure in which a steel rod having a male screw portion is attached to the nut-like member.

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