JP4242000B2 - Seismic pile - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pile excellent in earthquake resistance.
[0002]
[Prior art]
As a result of the damage survey of the Great Hanshin Earthquake that occurred in 1995, it was revealed that many cast-in-place piles and PHC ready-made piles were bent and fractured near the depth of 4 to 6 m from the ground surface and near the pile head. . This is because a large horizontal displacement occurs in the intermediate layer consisting of a soft-viscous soil layer and a loose sand layer, and as a result, there is a strong layer existing above and below the intermediate layer and a pile site located at the boundary of the intermediate layer. The cross-sectional force such as a great shearing force and bending moment is generated, and the pile is broken by receiving the cross-sectional force.
[0003]
[Problems to be solved by the invention]
At the present time, the behavior of piles during an earthquake has almost been elucidated, and it is known that the position at which the bending moment increases almost coincides with the actual pile failure position. Therefore, in the design of piles against earthquakes, it is known that the pile can be reduced by rotating the pile against the bending moment acting on the pile at the cross-sectional position where the bending moment acts greatly. A lot of trial and error has been done so far.
However, a method with excellent practicality has not been developed from the viewpoint of structural rationality, structural safety, and cost, and it has been desired to be developed immediately.
[0004]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a seismic pile excellent in seismic resistance that has a simple structure and is easy to construct.
[0005]
[Means for Solving the Problems]
In short, the seismic pile according to claim 1 is for connecting the main reinforcing bar to a pile main body composed of a plurality of main reinforcing bars and concrete arranged in the axial direction and an arbitrary position orthogonal to the axial direction of the pile main body. The end portion of the first main reinforcing bar arranged in one direction with the connecting member as a boundary is fixed to the connecting member and is opposite to the first main reinforcing bar. The end portion of the second main reinforcing bar is attached to the connecting member via an elastic member so as to be expandable and contractable in the axial direction, and the elastic member is provided on the connecting member. It is characterized by being inserted into a guide pipe .
Here, it is necessary to provide the connection material at a position where the cross-sectional force (particularly the bending moment) acting on the pile body is increased.
[0006]
In here, the elastic member, rubber or a coil spring, or it is obtained by a combination of the rubber and the coil spring, it is preferable from the actual construction.
[0007]
Therefore, according to the present invention, the first main reinforcing bar is fixed to the connecting member, and the second main reinforcing bar is attached to the connecting member via the elastic member so as to be expandable and contractable in the axial direction. The main body can have a hinge structure at the connecting member. Therefore, for the bending moment acting on the pile body, by rotating and deforming around the part of the connecting material, the sectional force is reduced, and an earthquake-resistant structure that can resist shear stress Can do.
[0008]
The earthquake-resistant pile according to claim 2 is the earthquake-resistant pile according to claim 1 , wherein the connecting material is a connecting plate having an opening in the center.
[0009]
Therefore, according to the present invention, since the connecting material is a connecting plate having an opening in the center, particularly when a cast-in-place pile is constructed, a treme tube is inserted into the opening to place concrete. Therefore, the construction can be easily performed.
[0010]
Also, seismic pile according to claim 3, wherein, in the seismic pile according to claim 1 or claim 2, surrounds the outer periphery of the connecting member, that is provided with a freely waterproof member expands and contracts in the axial direction It is a feature.
Furthermore, the earthquake-resistant pile according to claim 4 is the earthquake-resistant pile according to any one of claims 1 to 3 , wherein the connecting material and the main reinforcing bar are formed or covered with a rust-proof material. It is a feature.
[0011]
Therefore, according to the present invention, since the outer periphery of the connecting material is surrounded by the elastic waterproof member, the connecting material and the main material can be used even when cracks occur in the concrete of the pile body around the connecting material. Corrosion of reinforcing bars can be prevented.
Further, since the connecting material and the main reinforcing bar are formed or covered with a rust-proof material, corrosion of the connecting material and the main reinforcing bar can be prevented.
[0012]
Furthermore, the seismic pile according to claim 5 is characterized in that in the seismic pile according to any one of claims 1 to 4 , a shear reinforcing bar is arranged around the connecting material.
[0013]
Therefore, according to the present invention, since the reinforcing portion is reinforced by arranging a shear reinforcing bar around the connecting material, even if a shearing force acts on the connecting material simultaneously with a bending moment, the shear reinforcement is provided. Since the reinforcing bars resist the shearing force, it is possible to prevent the development of oblique cracks that occur in the concrete of the pile body.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. In addition, in each embodiment, the same code | symbol is attached | subjected to the element which plays the same role, and the description is abbreviate | omitted.
[0015]
1st Embodiment (1) Configuration of Seismic Pile As shown in FIG. 1, the seismic pile according to the present invention is a pile main body K and an intermediate portion of the pile main body K at a position orthogonal to the axial direction. It consists of a seismic joint J that is provided.
[0016]
The pile body K includes a plurality of main reinforcing bars S1 and S2 arranged in the axial direction, and a band reinforcing bar (shear reinforcing steel) arranged in a circumferential direction so as to surround the main reinforcing bars S1 and S2. (Not shown) and the main part is composed of the main reinforcing bars S1 and S2 and the concrete C integrated with the belt reinforcing bars.
The main reinforcing bars are provided with a plurality of first main reinforcing bars S1 that are arranged upward and second main reinforcing bars S2 that are arranged downward with the seismic joint J as a boundary.
[0017]
The first main reinforcing bar S1 and the second main reinforcing bar S2 are arranged in holes 31 and 32 of the ring plate 30 to be described later while alternately shifting the positions. Further, the end portions of the first main reinforcing bar S1 and the second main reinforcing bar S2 on the ring plate 30 side are formed with screw nodes (not shown) so that the nuts 12 and 22 can be easily screwed together.
[0018]
The seismic joint J is formed by a ring plate 30 that is a connecting material, and is fixed to the first main reinforcing bar S1 and the second main reinforcing bar S2 at the first main reinforcing bar fixing part 10 and the second main reinforcing bar attaching part 20, respectively. Is attached.
The ring plate 30 is a steel disk having a circular opening at the center, and a plurality of holes 31 for fixing and attaching the first main reinforcing bar S1 and the second main reinforcing bar S2 to the upper surface part of the ring plate 30. , 32 are formed at predetermined intervals.
[0019]
As shown in FIG. 4, the first main reinforcing bar S <b> 1 has a lower end inserted through the hole 31 and is fixed by a pair of washers 11 and nuts 12 from both sides of the ring plate 30.
As shown in FIG. 2 (a), the second main rebar S2 has an upper end inserted through the hole 32 and a hard rubber 35 provided at the upper part of the ring plate 30. A pair of washers 21 and nuts 22 are attached to both sides of the ring plate 30 so as to be extendable in the axial direction.
The hard rubber 35 is inserted into the cylindrical guide pipe 34 and is elastically deformed between the upper washer 21 and the nut 22 and the ring plate 30, and the elastic force is applied to the second main rebar S2. It is configured to be able to support.
[0020]
Therefore, when a bending moment is applied to the seismic pile, the tensile force and the elastic force of the hard rubber 35 are applied to the second main rebar S2 on the tension side, so that the second main rebar S2 is an axial ring. It can extend greatly below the plate 30.
[0021]
Here, a supplementary explanation will be given regarding the elastic member.
In the embodiment, the hard rubber 35 is used as the elastic member. However, as another embodiment of the elastic member, the steel spring 36 (FIG. 3A) formed in a coil shape or the hard rubber 35 is used. A composite member (FIG. 3B) in which the steel spring 36 is embedded can be used.
[0022]
In addition, if a high damping rubber having both a spring function and a damping function is used as the elastic member, even if the earthquake-resistant joint portion J is repeatedly subjected to a seismic force, it can be displaced without providing a damping member such as a damper. This is very suitable because it can be attenuated and a seismic isolation effect can be expected.
[0023]
If the spring constant of the elastic member is increased, the restoring characteristics of the earthquake-resistant joint portion J will increase. Therefore, the selection of the elastic member and the setting of the spring constant are designed to be optimal for the entire earthquake-resistant pile and structure. It will be necessary.
[0024]
(2) Action of earthquake-resistant pile The earthquake-resistant pile according to the present invention is configured as described above, and its action will be described below.
Here, FIG. 5 is a side sectional view showing an external force acting on the seismic pile according to the present invention (in the figure, the bending moment is indicated as M) and deformation (in the figure, the rotation angle is indicated as φ). FIG. 6 is a diagram showing the relationship between the bending moment (M) acting on the seismic joint J of the seismic pile and the rotation angle (φ).
[0025]
When a bending moment M acts on the seismic pile in the arrow direction of FIG. 5 due to the earthquake, a tensile force is generated in the second main reinforcing bar S2 on the left side of FIG. 5 and the hard rubber 35 is compressed and deformed. A downward biasing force (see FIG. 2B) acts. Therefore, the second main reinforcing bar S2 extends downward from the ring plate 30 and deforms (FIG. 6 (state between op)). At this time, while a tensile force smaller than the tensile strength of the concrete C is acting, the concrete C on the tension side resists integrally with the second main reinforcing bar S2. However, if a tensile force higher than the tensile strength is applied, cracks C1 are concentrated on the lower side of the ring plate 30 and grow large, so that the integrity of the concrete C and the second main reinforcing bar at that portion is lost. As a result, the concrete C cannot resist the tensile force.
[0026]
Therefore, compared with the part (hereinafter referred to as “general part”) in which the concrete C and the second main reinforcing bar S2 are integrated, the earthquake-resistant joint part J can be subjected to a large rotational deformation with respect to a smaller bending moment. That is, it becomes a hinge (FIG. 6 (state shown between pq)). For this reason, when a bending moment acts, the pile main body K can be rotationally deformed around the seismic joint J, and the bending moment acting on the part can be reduced.
[0027]
Furthermore, when the bending moment increases, the earthquake-resistant joint portion J further undergoes rotational deformation. However, when the deformation of the hard rubber 35 reaches a limit, the second main reinforcing bar S2 is fixed to the ring plate 30. . Therefore, the second main reinforcing bar S2 is integrated with the first main reinforcing bar S1 and the ring plate 30, and can resist the bending moment. Therefore, after the large rotational deformation occurs, the earthquake-resistant joint portion J has the same bending strength as that of the general portion (the state shown between qr).
[0028]
Further, a shearing force acts on the earthquake-resistant joint portion J simultaneously with the bending moment. At that time, even if the pile main body K is greatly deformed by rotation with respect to the bending moment, the band reinforcing bars are arranged, so that the band reinforcing bars resist the shearing force, and thus occur in the concrete C. Diagonal cracks do not develop.
[0029]
As described above, the ultimate strength for the bending moment of the earthquake-resistant pile according to the present invention is the same throughout the earthquake-resistant pile, and the earthquake-resistant joint portion J is generally provided at a place where the maximum bending moment is theoretically generated. Therefore, the earthquake-resistant pile will not bend and break at the part of the pile other than the earthquake-resistant joint portion J.
[0030]
For reference, FIG. 6 (left part) also shows the relationship between the bending moment (M) acting on the general part and the deformation angle (φ) caused by bending deformation. According to this, it can be seen that the earthquake-resistant joint portion J has a larger deformation angle than the general portion and allows a very large bending deformation. Therefore, even if the earthquake-resistant joint portion J undergoes large shear deformation due to liquefaction of the ground during an earthquake, the pile body K greatly rotates and deforms following the ground deformation, thereby reducing the bending moment. Therefore, the diameter of the pile main body K and the number of main reinforcing bars S1, S2 can be reduced as compared with the case where the earthquake-resistant joint portion J is not provided.
[0031]
Further, FIG. 7A shows a bending moment generated in the pile K ′ and the footing F ′ when a plurality of conventional piles K ′ are joined to the footing F ′ (or the foundation beam) at the head. FIG. 7B shows the distribution of bending moment generated in the seismic pile and footing F when a plurality of seismic piles are joined to the footing F at the head.
According to this, since the bending moment acting on the footing F is reduced as the bending moment is reduced in the earthquake-resistant joint portion J, not only the pile body K but also the cross-sectional area of the footing F can be reduced.
[0032]
Further, since the hard rubber 35 is interposed between the upper end portion of the second main reinforcing bar S2 and the ring plate 30 in the second main reinforcing bar mounting portion 20 of the earthquake-resistant joint portion J, the hard rubber 35 is exempted. The seismic response acceleration transmitted from the ground can be interrupted at the seismic joint J. Therefore, the bending moment acting on the seismic pile can be reduced, and the acceleration response due to the earthquake to the structure built on the upper part of the pile foundation and the upper structure can be reduced, and the structure etc. is designed as a seismic isolation structure be able to.
[0033]
(3) Construction method of earthquake-resistant pile The earthquake-resistant pile according to the present invention can be easily constructed by a method substantially the same as the method for constructing a conventional cast-in-place pile.
Hereinafter, an example of a construction method of a seismic pile will be briefly described with reference to FIG.
[0034]
First, a hole 52 is excavated in the target ground 50 by a bentonite mud construction method such as a reverse circulation method (FIG. 10A).
Next, the reinforcing bar 53 pre-assembled in the ground part is connected by a mechanical grip joint (or a lap joint of the reinforcing bar) and inserted into the hole 52 filled with the muddy water 51, thereby reinforcing the reinforcing bar. The eaves 53 are built (FIG. 10B).
The seismic joint is formed by providing the ring plate 30 at a desired position when assembling the reinforcing bar 53 and connecting the main reinforcing bars S1 and S2 to the ring plate 30.
After the building of the reinforcing bar 53 is completed, the tremy tube 54 is inserted into the reinforcing bar 53 (FIG. 10C). Then, while replacing the muddy water 51 and the concrete C using the tremy pipe 54, the underwater concrete is cast to complete the earthquake-resistant pile (FIG. 10 (d)).
[0035]
As described above, the method for constructing a seismic pile according to the present invention is the same as the conventional method for constructing a cast-in-place pile except that the seismic joint J is provided on the reinforcing bar 53. Therefore, the earthquake-resistant joint portion J can be reliably provided at an arbitrary position, and the earthquake-resistant pile can be easily constructed without causing inconveniences such as an increase in construction cost.
The ring plate 30 has a circular opening at the center. Therefore, when placing the underwater concrete, the concrete C can be placed using the tremy tube 54 in the same manner as the conventional construction method, and therefore the filling property of the concrete C is completely affected. It is very good at not giving.
[0036]
Further, as materials for forming the earthquake-resistant joint portion J, there are the ring plate 30 and washers 11 and 21 and nuts 12 and 22 provided at the ends of the main reinforcing bars S1 and S2, and the guide pipe 34 and the hard rubber 35. In addition, since no special processing or the like is required, the seismic pile can be constructed at a very low cost.
[0037]
Second Embodiment As described above, in the earthquake-resistant pile described in the first embodiment, cracks C1 concentrate on the portion of the concrete C on the tensile side below the earthquake-resistant joint portion J (see FIG. 5). Therefore, if you continue to use the seismic pile after receiving a major earthquake, the crack C1 is still open, so that groundwater and permeated water from the ground permeate from the site, Corrosion proceeds to the main reinforcing bars S1 and S2 and the steel ring plate 30.
The second embodiment is an earthquake-resistant pile for solving the above-described problems, and can prevent corrosion of the main reinforcing bars S1 and S2 and the steel ring plate 30.
[0038]
As shown in FIG. 8, the seismic pile of the second embodiment is provided with a waterproof rubber ring 40 that is a waterproof member so as to surround the outer periphery of the ring plate 30 to the seismic pile of the first embodiment. It is. The water-stop rubber ring 40 is formed of a cylindrical outer peripheral portion 40a and two-stage protruding portions 40b and 40c that protrude in a direction orthogonal to the outer peripheral portion 40a.
The upper protruding portion 40b is formed with an uneven portion in the shape of an internal gear in plan view, and a through hole (not shown) is formed in the protruding portion. The upper protrusion 40b is locked to the ring plate 30, and the lower end of the first main reinforcing bar S1 is inserted through the through hole. A pair of washers 11 and nuts are formed from both sides of the ring plate 30. 12 is fixed.
[0039]
The waterstop rubber ring 40 is rich in elasticity and is formed to be extendable and contractible in the axial direction of the earthquake-proof pile. Therefore, when the tensile force is applied, the water-stopping rubber ring 40 is expanded, and when the compression force is applied, the water-stopping rubber ring 40 is contracted. Can follow.
In addition, the axial length of the water stop rubber ring 40 can be appropriately determined according to the crack width and the like expected for the concrete C of the pile body K.
[0040]
Since it comprised in this way, even if it is a case where the crack C1 has arisen in the concrete C of the lower position of the earthquake-resistant joint part J by a large earthquake, the ring plate 30 and main reinforcement S1 are carried out by the water stop rubber ring 40. , S2 is secured, so even if water or the like enters from the crack C1, the ring plate 30 and the main reinforcing bars S1, S2 do not corrode.
Further, even when a major earthquake occurs again after a major earthquake, the water-stopping rubber ring 40 has a large deformability and can block water between the crack C1 and the ring plate 30. is there.
[0041]
Third Embodiment Similar to the second embodiment, the third embodiment is a seismic pile that can prevent corrosion of the main reinforcing bars S1 and S2 and the ring plate 30 ′.
[0042]
As shown in FIG. 9, the seismic pile according to the present embodiment is formed by forming the ring plate 30 ′ from high-strength fiber concrete (compressive strength: 200 MPa) as a rust-proof material and main reinforcing bars S1, S2 near the earthquake-resistant joint J ′. Is coated with an epoxy resin 41, which is a rust preventive paint, and the other components are the same as in the first embodiment.
[0043]
With this configuration, even if a crack C1 occurs in the concrete C at the lower position of the earthquake-resistant joint portion J ′ due to a large earthquake, the ring plate 30 ′ is not made of steel, and the main rebar S1, Since S2 is also not directly exposed to water, the ring plate 30 'and the main reinforcing bars S1 and S2 are not corroded even if the water is immersed in the crack C1.
[0044]
As mentioned above, although an example about suitable embodiment was explained about the present invention, the present invention is not restricted to the embodiment concerned, and design change is possible for each component in the range which does not deviate from the meaning of the present invention. is there. Therefore, it can be used for various piles such as ready-made piles as well as cast-in-place piles. Moreover, there is no restriction | limiting in particular regarding the material and shape of a connection material, the number of main reinforcing bars, etc. Also about an antirust material and an antirust coating, it is not restricted to the above-mentioned thing.
Furthermore, in the said embodiment, the case where the earthquake-resistant joint part was provided in the intermediate part of the pile main body was demonstrated. However, it goes without saying that the position of the earthquake-resistant joint portion is not limited to the portion, and may be provided on a pile head or the like.
[0045]
【The invention's effect】
As described above, the seismic pile according to the present invention can reduce the cross-sectional force acting on the pile main body by rotating and deforming the cross-sectional force acting on the pile according to the deformation of the ground around the connecting portion. At the same time, the cross-sectional force acting on the footing of the pile head can also be reduced. Therefore, since the seismic pile of the present invention does not resist the rigidity and force of the pile unlike the conventional pile, the cross section of the entire seismic pile and footing can be reduced, thus reducing the construction price of the entire structure And the seismic performance can be improved.
[0046]
In addition, according to the seismic pile of the present invention, it can sufficiently withstand a large earthquake of level 2 class, has excellent durability, and has waterproof properties. Can also be used continuously.
[Brief description of the drawings]
FIG. 1 is an enlarged perspective view of a main part of a seismic pile according to the present invention.
FIG. 2 is a side sectional view showing a second main reinforcing bar mounting portion of the seismic pile according to the present invention, (a) is a diagram showing a normal time, and (b) is a diagram showing a case where a tensile force is applied. .
FIGS. 3A and 3B are side cross-sectional views showing another embodiment of the second main reinforcing bar mounting portion of the earthquake-proof pile according to the present invention.
FIG. 4 is a side sectional view showing a first main reinforcing bar fixing portion of the earthquake-resistant pile according to the present invention.
FIG. 5 is a side sectional view showing an external force acting on the seismic pile according to the present invention and a mode of deformation.
FIG. 6 is a diagram showing a relationship between a bending moment and a rotation angle acting on the earthquake-resistant joint portion of the earthquake-resistant pile according to the present invention, and a bending moment and a rotation angle acting on a general portion.
FIGS. 7A and 7B are diagrams showing a distribution of bending moment acting on a pile and a foundation beam. FIG. 7A shows a case where a conventional pile is used, and FIG. 7B shows a case where a seismic pile according to the present invention is used. .
FIG. 8 is an enlarged perspective view showing a main part of a second embodiment of the seismic pile according to the present invention.
FIG. 9 is an enlarged perspective view showing a main part of a third embodiment of the earthquake-proof pile according to the present invention.
FIG. 10 is a side sectional view showing a method for constructing a seismic pile according to the present invention.
[Explanation of symbols]
K pile body J earthquake resistant joint part C concrete S1 first main reinforcing bar S2 second main reinforcing bar 10 first main reinforcing bar fixing part 20 second main reinforcing bar attaching part 30, 30 'ring plate 35 hard rubber 40 waterstop rubber ring 41 epoxy resin

Claims (5)

A pile body composed of a plurality of main reinforcing bars and concrete arranged in the axial direction;
An end portion of a first main reinforcing bar which is provided with a connecting member for connecting the main reinforcing bar at an arbitrary position orthogonal to the axial direction of the pile main body and is arranged in one direction with the connecting member as a boundary. Is fixed to the connecting material,
The end of the second main reinforcing bar arranged on the side opposite to the first main reinforcing bar is attached to the connecting member via an elastic member so as to be expandable and contractable in the axial direction .
The earthquake-resistant pile , wherein the elastic member is inserted into a guide pipe provided in the connecting member . The seismic pile according to claim 1, wherein the connecting material is a connecting plate having an opening at the center. The surrounding the outer periphery of the connecting member, seismic pile according to claim 1 or claim 2, characterized in that are provided freely waterproof member expands and contracts in the axial direction. The earthquake-resistant pile according to any one of claims 1 to 3 , wherein the connecting material and the main reinforcing bar are formed or covered with a rust-proof material. The earthquake-resistant pile according to any one of claims 1 to 4 , wherein a shear reinforcing bar is arranged around the connecting material.

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