JP4224607B2 - Pile hinge-induced structure - Google Patents

Description

  The present invention relates to a structure for inducing a hinge of a pile in which a hinge is positively formed at the position of an intermediate portion in the axial direction of the pile embedded or constructed in the ground.

Support piles that support superstructures such as buildings are often rigidly joined to the foundations (footings) of the superstructure in order to reliably transmit bending moments from the superstructure to the ground. Since the acting bending moment becomes excessive, it is necessary to increase the cross section of the foundation and the pile head to resist the bending moment.
However, as the cross-section increases, the stress generated in the foundation and pile head also increases, and the design of the joint itself becomes impossible or unreasonable. In addition, the joint between the foundation and the pile head is hinged (pin) joined, and the pile head is allowed to rotate (see Patent Documents 1 to 3).

In addition, by connecting a plurality of pile elements separated in the axial direction of the pile to form a pile, the pile itself can be freely deformed in units of pile elements by the horizontal force at the time of the earthquake. There is a method for preventing horizontal force from the ground from being transmitted to the superstructure (see Patent Document 4).

JP-A-11-117326 (Claim 1, FIG. 1 and FIG. 2) Japanese Patent Laying-Open No. 2004-44312 (Claim 1, FIG. 1) JP 2004-257187 A (Claim 1, FIG. 1) JP-A-9-59997 (Claim 1, FIG. 1, FIG. 3)

In the methods of Patent Documents 1 to 3, the hinge (pin) is formed at the head portion of the pile where the bending moment when it is fixed to the foundation is the largest, so the stress of the foundation beam connected to the pile can be reduced. However, since the hinge (pin) is formed only at the pile head portion, the bending moment in the section below the pile head portion may be rather increased.

If hinges (pins) having no resistance moment are used at both ends of the pile element as in Patent Document 4, there is an effect of changing a bending moment distribution generated in the pile. On the other hand, as shown in FIG. 8- (a), no resistance moment is generated at both ends of the pile element. Therefore, rather than not providing a hinge (pin) as shown in (b), the hinge (pin) of the pile. There is a possibility that a large bending moment is applied to other sections. It can be seen that a large bending moment may also occur in the section below the pin due to the shearing force Qm acting on the lower end (pile middle part) of the pile element shown in (a).

In Patent Document 4, the effect of seismic isolation is achieved by providing hinges (pins) that have almost no resistance to bending moment at the top and bottom of the pile, but this structure is actually established as a seismic isolation structure. This is a combination of a device for reducing horizontal reaction force between the two hinges (pins) and a device for taking the horizontal reaction force and a damper for damping, as is apparent from the base isolation structure using the base isolation rubber. It is necessary to

The present invention proposes a hinge-inducing structure for a pile that can reduce the bending moment of the pile, absorb energy, and provide a seismic isolation or damping effect.

In the present invention, a pile formation planned position where resistance to bending moment is relatively lowered is formed in the axial intermediate portion of the pile, and a cross section of the pile is designed so that the hinge is not formed other than the hinge formation planned position. To reduce the bending moment of the pile and absorb energy.

Energy absorption by hysteretic absorption energy during elastic-plastic deformation at the hinge formation position at the hinge formation position where the resistance to bending moment is relatively reduced in the axial middle part of the pile Ability is demonstrated. The hinge formation planned position is formed at one place in the axial direction of the pile, or at a plurality of places including the intermediate part.

In addition, as shown in FIG. 1, the bending moment distribution when the hinge is not formed at the intermediate portion of the pile 1 in which the head 1a is fixed to the foundation (footing) 6 is the maximum value at the head 1a and the intermediate portion as shown by the broken line. In contrast, the bending moment distribution when the hinge is formed in the middle part excluding the head 1a of the pile 1 is shown by the hinge in the middle part of the pile as shown by the solid line, especially in the section below the hinge. Bending moment is reduced. As a result, the cross section of the pile can be reduced, and the cost required for manufacturing or constructing the pile can be reduced.

In particular, by forming a hinge formation planned position where resistance to bending moment is relatively reduced at the head and axial center of the pile, the bending moment of the pile is reduced, and the energy absorption capacity at the time of earthquake is also increased. Make it work. Furthermore, the effect of seismic isolation or vibration control is exhibited by appropriately setting the resistance moment of the pile head, the hinge formation planned position and the resistance moment of the middle part of the pile. The hinge formation planned position in the axial middle part is formed in one place or a plurality of places in the axial direction of the pile.

In this case, in addition to the intermediate portion of the pile, the hinge formation planned position where the resistance to the bending moment suddenly changes (rapidly decreases) is also formed in the head portion of the pile. The energy absorption performance at the time of earthquake due to the history absorbed energy is improved compared to the case where it is formed only in
Moreover, since the bending moment generated in the pile can be adjusted over the entire length of the pile by forming a hinge on the head 1a of the pile 1, the pile is rationally designed (pile cross section is reduced). Is possible.

When an inertial force due to an earthquake acts on an upper structure 7 such as a building on the foundation 6, a pile is formed on the head 1a and an intermediate portion of the pile 1 so that the pile 1 has a head 1a as shown in FIG. Since the ground between the middle part and the middle part, that is, between the hinges can be plastically deformed almost uniformly, in addition to the energy absorption by the pile 1, the energy absorption effect by the plastic deformation of the ground larger than when the hinge is not formed in the middle part of the pile Can be expected. As a result, the seismic force (inertial force) input to the superstructure 7 on the foundation 6 is reduced, and the stress acting on the pile 1 is also reduced.
In addition, since the deformability of the pile itself is increased, it is possible to follow the deformation without breaking the pile even when the ground is largely deformed.

In the present invention , unlike the above-mentioned Patent Document 4, as shown in FIG. 9- (a), the resistance moment Mm against the ground reaction force acts on the hinge formation planned position, and the resistance moment Mh also acts on the pile head. Therefore, if the position of the hinge formation planned position in Mm and the intermediate part (where the hinge formation planned position is arranged in the pile intermediate part) is appropriately set according to Mh, the hinge formation planned position in the pile intermediate part is set. The working shear force Qm can be reduced, and as a result, the bending moment in the section below the hinge formation planned position can be reduced as shown in FIG. 9- (b). In other words, by providing a certain resistance moment Mh, Mm to the hinge between the pile head and the middle part of the pile, the position of the hinge formation planned position and the resistance moment in the middle part of the pile according to the resistance moment Mh at the pile head By appropriately planning Mm, the bending moment generated in the pile can be adjusted over the entire length of the pile, so that it is possible to rationally design the pile (reducing the pile section).
On the other hand, in Patent Document 4, since the resistance moment does not occur at both ends of the pile element, the pile is rationally designed such that a greater bending moment may be generated in the pile than when no hinge (pin) is provided. There are limits to doing it.

Also, unlike the above-mentioned Patent Document 4, the head moment of resistance Mh, the position of the expected hinge formation position and the moment of resistance Mm are adjusted by forming a hinge on the head in addition to the middle portion of the pile. since it is possible to, Mh, by appropriately setting the Mm, that the shearing force Qm acting on the hinge to be formed position of the pile intermediate portion is reduced to reduce the bending moment under the section from the hinge to be formed position Is possible. That is, the pile head can have a resistance moment Mh and the hinge in the middle of the pile can have a certain resistance moment Mm, so that the positions of these resistance moments Mh and Mm and the hinge formation planned positions in the middle are appropriately planned. As a result, the bending moment generated in the pile can be adjusted over the entire length of the pile, so that the pile can be rationally designed (the pile cross section can be reduced).

Also, the street, after reducing the ground reaction force between the pins to substantially seismic isolation structure the pile in the patent literature 4, it is necessary to add the horizontal reaction force device and the damper, the In the present invention, it is possible to give a constant resistance moment to at least one of the upper and lower hinges, and if the magnitude of the resistance moment and the position of the hinge formation position are appropriately set according to the ground, the seismic isolation and damping effect Since it is possible for the pile itself to exhibit the restoring force and energy absorption capability necessary to have the sword, it is not necessary to use a horizontal reaction force device and a damper together. In other words, according to the present invention , hinges are provided at two or more places including the pile head and the pile middle part, or the pile middle part, the resistance moment in the pile head, the position of the hinge formation planned position of the pile middle part, and By appropriately planning the resistance moment, it is possible to cause the pile to exhibit seismic isolation or vibration control.

In the invention according to claim 4 , the auxiliary main bar is arranged in the axial direction of the pile in the cross section of the concrete that constitutes the pile, and the auxiliary main bar is separated in the axial direction of the pile at the position where the hinge is to be formed. The position where the hinge is to be formed is formed in which the resistance to the relative resistance is relatively reduced.
Separating the auxiliary main bars in the axial direction of the pile is a specific means for forming the hinge formation scheduled position when the pile is a concrete pile or a steel pipe concrete pile in claims 1 to 3 .

As shown in FIG. 3, the auxiliary main reinforcement 3 arranged in the concrete of the pile 1 is separated in the axial direction of the pile at the hinge formation scheduled position 2 indicated by a broken line, so that at the end position of the separated auxiliary main reinforcement 3, On the cross section perpendicular to the axis of the pile 1, the resistance force against the tensile force acting on the position of the auxiliary main bar 3 changes suddenly (abruptly decreases). It is formed at the end position. Since the hinge appears intensively at the position (cross section) where the resistance to the tensile force changes suddenly in the entire length of the pile 1, damage to the concrete constituting the pile 1 is dispersed around the hinge when the hinge is formed. There is almost no damage to the concrete on both sides of the hinge.

According to the fifth aspect of the present invention, the steel pipe constituting the pile is separated in the axial direction of the pile at the position where the hinge is to be formed, thereby forming the position where the hinge is to be formed with a relatively low resistance to bending moment.
Separating the steel pipe in the axial direction is a specific means for forming the hinge formation scheduled position when the pile is a steel pipe or a steel pipe concrete pile in the inventions of claims 1 to 4 .

Also in this case, as shown in FIG. 4, when the steel pipes 5 are separated from each other at the hinge formation scheduled position 2 indicated by a broken line, the resistance force to the tensile force acting on the steel pipe 5 at the separation position is suddenly changed (rapidly reduced). Therefore, the hinge accompanying the bending moment is formed at the end position of the steel pipe 5 which is the hinge formation planned position 2. Since the hinge appears intensively at the position (cross section) where the resistance to tensile force changes suddenly, if the pile is a steel pipe concrete pile, the concrete damage will not be distributed around the hinge, and both sides of the hinge Little damage to concrete occurs.

In the present invention , the main bar is arranged in the axial direction of the pile in the cross section of the concrete constituting the pile, and the main bar is cut off from the concrete in a part of the vicinity of the position where the hinge is to be formed. The damage of concrete near the planned position of hinge formation is reduced.

In this case, the section of the main reinforcement that is not attached to the concrete (not attached) expands and contracts without being restricted by the concrete when the attached (attached) section tries to follow the deformation of the concrete. Therefore, in addition to the concrete on both sides sandwiching the hinge as described above, damage to the concrete around the section without adhesion is also reduced.
The main bar 4 on the tension side bears an axial tensile force due to a bending moment as shown in FIG. 5- (a), and follows the deformation of the pile 1 in the attached section, but the hinge formation planned position 2 indicated by the broken line In the vicinity of the non-attached section, it is separated from the concrete, so that it deforms and eventually yields.

As shown in FIG. 5- (b), the main muscle 4 is located on the tension side from the planned position 2 to the head 1a side and moves to the section with adhesion. Resists force and resists compressive force on the compression side. This tensile resistance force and compression resistance force form a bending return moment that is a couple that resists the bending moment when paired in the direction in which the pile 1 is formed.
With this bending return moment, the bending moment of the portion excluding the non-attached main bar 4 in the section where the main bar 4 is not attached is reduced as shown in FIG. Also from the bending moment reduction effect due to this bending back moment, it can be seen that damage such as cracking or crushing of the concrete other than the portion where the main reinforcement 4 is not attached is suppressed.

FIG. 6 shows a case where a plurality of main bars 4 are arranged on one side of the center of the pile 1 and the length of the section where the main bars 4 are cut off is made different for each main bar 4. FIG. 6 shows a bending moment distribution of a portion excluding the main muscle 4 without adhesion in a section where the main muscle 4 does not adhere. As shown here, when the lengths of the sections where the plurality of main bars 4 are not attached are made different, the bending moment of the portion excluding the main bars 4 where the main bars 4 are not attached is reduced stepwise. It can be seen that the maximum value of the bending moment is also reduced.

As described above, in the present invention, the hinge formation planned position in which the resistance to the bending moment is relatively reduced is formed in the axial intermediate portion of the pile, so that the hinge at the hinge formation position is plasticized while resisting the bending moment. Therefore, the energy absorption ability by the history absorption energy can be effectively exhibited.
Moreover, since the maximum value of the bending moment of a pile intermediate part is reduced rather than the case where a hinge is not formed, the cross section of a pile can be reduced and the cost required for manufacture or construction of a pile can be reduced.

According to invention of Claim 5 , since a hinge is formed in the hinge formation scheduled position of the head part of a pile and an intermediate part, energy absorption capability can be exhibited also in the head part of a pile.
In addition, since the ground between the head and the middle where the hinge is formed can be plastically deformed almost uniformly, the energy absorption effect due to the plastic deformation of the ground can be expected, and the seismic force input to the superstructure And the stress acting on the pile can be reduced.

Furthermore, by forming hinges on the head in addition to the middle part of the pile, it is possible to adjust the magnitude of the resistance moments that occur, so set the magnitude and position of these resistance moments appropriately. Thus, the bending moment of the pile can be made smaller than in the case of claim 1, and the pile can be rationally designed (the pile cross section can be reduced).

Moreover, by appropriately setting the resistance moment of the pile head, the hinge formation planned position and the resistance moment of the middle portion of the pile, it becomes possible to exert the seismic isolation or vibration control effect on the pile.

In the present invention, the main bars arranged in the cross section of the concrete are cut off from adhering to the concrete in a part of the vicinity of the position where the hinge is to be formed. Since the resistance force is exerted, the bending moment of the portion excluding the main bar without adhesion in the section where the main bar does not adhere can be reduced, and the concrete damage in the section can be reduced.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

FIG. 1 shows an outline of a hinge induction structure for a pile according to claim 1, wherein a hinge formation planned position 2 in which a resistance force to a bending moment is relatively lowered is formed in an intermediate portion in the axial direction of the pile 1.
FIG. 2 shows a hinge inducing structure for a pile according to claim 3, wherein a hinge formation planned position 2 in which resistance to bending moment is relatively lowered is formed in a head portion 1a of the pile 1 and an axial intermediate portion of the pile 1. An overview is shown. In FIG. 1, the head 1 a of the pile 1 is fixed (rigidly joined) to a foundation (footing) 6, but a hinge is formed in FIG. 2.

  Pile 1 includes steel pipe piles, steel piles or other metal piles, concrete piles, reinforced concrete piles, steel pipe concrete piles, soil cement mixed with solidified material (consolidated material) and excavated ground, or soil cement and steel pipe. A composite pile or the like is used, and a steel core material may enter the reinforced concrete pile, and the concrete pile may be hollow or solid. The method of burying the pile 1 in the ground or the construction method in the ground is not questioned. Further, the hinge formation planned position 2 or the structure of the section sandwiching the hinge formation position 2 is not limited, and may be reinforced concrete, steel frame or other metal.

FIG. 3 shows the auxiliary main reinforcement 3 in the cross section of the concrete constituting the pile 1 when the hinge formation planned position 2 is formed in the axial intermediate portion of the pile 1 or in the axial intermediate portion of the pile 1 and the head 1a. The pile hinge according to claim 4 , wherein the hinge forming planned position 2 is formed by arranging the auxiliary main bars 3 in the axial direction of the pile 1 at the hinge forming planned position 2. A specific example of the trigger structure is shown.

FIG. 3 also shows that the main reinforcement 4 is arranged in the axial direction of the pile 1 in the cross section of the concrete constituting the pile 1, and the main reinforcement 4 is not attached to the concrete in a part of the vicinity of the hinge formation planned position 2. It is also an embodiment of the hinge-induced structure of the pile that.
The auxiliary main bars 3 are arranged along the main bars 4. The section where the adhesion of the main reinforcement 4 to the concrete is cut is formed at least on one side of the hinge formation planned position 2 and is formed across the hinge formation planned position 2 as shown in FIG. The auxiliary main bars 3 and 3 on the same line are separated from each other at the hinge formation planned position 2.

FIG. 4 shows that the steel pipe 5 constituting the pile 1 is the hinge formation planned position 2 when the hinge formation planned position 2 is formed at the axial intermediate portion of the pile 1 or at the axial intermediate portion of the pile 1 and the head 1a. The specific example of the hinge induction | guidance | derivation structure of the pile of Claim 5 in which the hinge formation planned position 2 was formed by isolate | separating in the axial direction of the pile 1 is shown.

FIG. 4 also shows that the main reinforcement 4 is arranged in the axial direction of the pile 1 in the cross section of the concrete constituting the pile 1, and the main reinforcement 4 is not attached to the concrete in a part of the vicinity of the hinge formation planned position 2. It is also an embodiment of the hinge-induced structure of the pile that.
The auxiliary main bars 3 are arranged along the main bars 4. The section where the adhesion of the main reinforcement 4 to the concrete is cut is formed at least on one side of the hinge formation planned position 2 and is formed across the hinge formation planned position 2 as shown in FIG.

FIG. 6 shows a case where a plurality of main bars 4 are arranged on one side of the pile 1 in the direction of formation, and the lengths of sections where the main bars 4 are cut off are made different. Here, as described above, a section where the adhesion of the main reinforcement 4 to the concrete is cut is formed so as to straddle the hinge formation planned position 2, but it may be formed only on one side of the hinge formation planned position 2. In addition, a plurality of main reinforcing bars 4 and one auxiliary main reinforcing bar 3 are arranged on one side of the center of the pile 1 in the direction of composition, but a plurality of auxiliary main reinforcing bars 3 may be arranged.

It is the elevation which showed the mode of the bending moment which arises in the pile in which the hinge formation planned position was formed in the axial direction middle part, and a pile. It is the elevation view which showed the mode of the deformation | transformation at the time of the earthquake of the pile in which the hinge was formed in the hinge formation planned position of a head part and an axial direction intermediate part. Auxiliary main reinforcement is arranged in the cross section of the concrete that constitutes the pile, and the auxiliary main reinforcement is separated from each other at the position where the hinge is to be formed. It is the longitudinal cross-sectional view shown. It is the longitudinal cross-sectional view which showed the case where the steel pipe which comprises a pile was isolate | separated from each other in the hinge formation planned position vicinity, and the adhesion | attachment with the main reinforcement concrete was cut in the partial area of the hinge formation planned position vicinity. (A) is a longitudinal sectional view showing a pile in which main bars are arranged, (b) is a longitudinal sectional view showing a reaction force in the vicinity of a planned hinge formation position of the pile at the time of an earthquake, and (c) is an adhesion of piles. It is the distribution map which showed the bending moment which arises in the part except the main bar which is not. It is a longitudinal cross-sectional view showing a case where a plurality of main bars are arranged on one side of the center of the pile in the direction of formation. It is the distribution map which showed the bending moment in the case of FIG. (A) is a diagram showing the state of the horizontal force and ground reaction force acting on the pile when no resistance moment is generated at the pile head and the middle part of the pile, and (b) is the bending moment at (a). FIG. (A) is a diagram showing the state of horizontal force and ground reaction force acting on the pile when a resistance moment is generated at the pile head and the middle part of the pile, and (b) is the bending moment at (a). It is the distribution map shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pile 1a head 2 Hinge formation planned position 3 Auxiliary main reinforcement 4 Main reinforcement 5 Steel pipe 6 Foundation 7 Superstructure

Claims (5)

In the pile in which the hinge formation planned position where resistance to tensile force due to bending moment is relatively lowered is formed in the middle in the axial direction,
During the cross section of the concrete that constitutes the pile, the main reinforcement that has broken the bond with the concrete in a partial section near the hinge formation planned position is arranged in the axial direction of the pile,
One end of the section where the main reinforcement adheres to the concrete, which is a partial section near the position where the hinge is to be formed, coincides with the position where the hinge is to be formed, and the other end is one side of the position where the hinge is to be formed. The pile-inducing structure for a pile, which is located at a position separated from the position by a distance that allows the main muscle to be deformed by extension . In the pile in which the hinge formation planned position where resistance to tensile force due to bending moment is relatively lowered is formed in the middle in the axial direction,
During the cross section of the concrete that constitutes the pile, the main reinforcement that has broken the bond with the concrete in a partial section near the hinge formation planned position is arranged in the axial direction of the pile,
The pile inducing structure according to claim 1, wherein a section of the main reinforcement, which is a partial section in the vicinity of the hinge formation planned position, is continuously formed across the hinge formation planned position. The head of the said pile is joined to the foundation, and the hinge formation scheduled position is formed in the head of a pile in addition to the axial direction intermediate part of a pile, The claim 1 characterized by the above-mentioned. Pile hinge-induced structure.   Auxiliary main bars are arranged in the axial direction of the pile in the cross section of the concrete constituting the pile, and the hinge formation planned position is formed by separating the auxiliary main bars in the axial direction of the pile at the hinge formation planned position. The hinge induction structure for a pile according to any one of claims 1 to 3, wherein the structure is a hinge induction structure for a pile.   The pile according to any one of claims 1 to 4, wherein the hinge formation scheduled position is formed by separating a steel pipe constituting the pile in the axial direction of the pile at the hinge formation scheduled position. Hinge-induced structure.

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