JP2017186760A - Pile foundation structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly practicable pile foundation structure capable of significantly reducing drawing force exerted on the pile at a time of earthquake, and efficiently reducing the drawing force at the time of earthquake while preventing enlarging of shear force exerted on the pile at the time of earthquake.SOLUTION: A pile foundation structure includes an existing building frame 1 remaining underground at a construction ground G, a new pile 2 installed underground at the construction ground G, and a new building frame 3 connected on top of the new pile 2. The new building frame 3 is connected to the existing building frame 1 such that weight of the existing building frame 1 functions to resist drawing force at a time of earthquake.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pile foundation structure including a new pile built in the ground of a construction site.

  As such a pile foundation structure, various structures are adopted according to the circumstances of the construction site and the construction plan. For example, Patent Literatures 1 to 5 describe a pile foundation structure including existing piles and new piles left in the ground of a construction site. In these pile foundation structures, the existing pile is burdened with a part of the vertical load of the building, thereby reducing the removal work of the existing pile and reducing the construction cost of the new pile.

By the way, in such a pile foundation structure, when the load balance of a building collapses due to shaking at the time of an earthquake, a pulling force (hereinafter abbreviated as an earthquake pulling force) acts on the pile.
Therefore, the pile head joint is assumed to be pulled out in the event of an earthquake so that the joint between the pile head and the foundation that is the building frame (hereinafter abbreviated as a pile head joint) is not destroyed by this pull-out force during an earthquake. The basic structure is to meet the requirements. On the other hand, there is a case where simplification of the structure of the pile head joint is required, or there is a case where further safety against the pullout force during an earthquake is required with the structure of the pile head joint being left as it is.

  Therefore, conventionally, in order to cope with such a case, the building frame type has been changed to a frame type in which the pulling force during the earthquake does not act on the pile, and a weight that offsets the pulling force during the earthquake has been added to the building. It is done.

JP 2000-154549 A Japanese Patent No. 3656493 Japanese Patent No. 5181288 Japanese Patent No. 568787 JP 2003-96794 A

However, the former has a disadvantage that the amount of reduction in the pullout force during an earthquake is small only by changing the frame type of the building, and it cannot be appropriately handled when it is desired to greatly reduce the pullout force during an earthquake.
The latter is not disadvantageous as described above, but the weight of the building becomes heavy with an additional weight, so the shear force acting on the pile during an earthquake (hereinafter abbreviated as the shear force during an earthquake) increases. There is.

  In view of this situation, the main problem of the present invention is that it is possible to greatly reduce the earthquake pulling force acting on the pile, and to prevent the earthquake pulling force while avoiding an increase in the earthquake shearing force acting on the pile. It is in the point which provides the excellent pile foundation structure with high practicality which can be reduced efficiently.

The first characteristic configuration of the present invention relates to a pile foundation structure,
The existing structure left in the basement of the construction site,
A new pile built in the ground of the construction site,
A new structure joined on the new pile,
The new chassis is connected to the existing chassis in a state where the weight of the existing chassis becomes a resistance element against the pulling force during an earthquake.

According to the above configuration, the weight of the existing chassis connected to the new chassis is a resistance element to the pullout force during an earthquake (in other words, a weight that cancels the pullout force during an earthquake), so the existing chassis is used effectively. As a result, it is possible to efficiently reduce the pulling force during the earthquake that acts on the new pile.
In addition, by effectively using the existing frame in this way, it becomes possible to save labor for dismantling / removing the existing frame and for building a new mountain retaining wall.
Furthermore, since the weight of the existing frame itself is large in the first place and the weight can be further increased by a simple method such as expanding the range to be left in the construction site, it becomes possible to greatly reduce the pulling force at the time of earthquake acting on the pile. .
Moreover, since the existing frame that is left underground is supported from below by its own foundation structure, even if the new frame and the existing frame are connected in this way, the weight of the new frame will not increase. . Therefore, it is also possible to avoid an increase in the shear force at the time of the earthquake that acts on the new pile by adding the weight of the existing case to the new structure.
From these things, it is possible to greatly reduce the pull-out force during earthquake that acts on the new pile, and efficiently reduce the pull-out force during earthquake while avoiding an increase in the shear force during the earthquake acting on the new pile. It is possible to realize an excellent pile foundation structure with high practicality.

  The 2nd characteristic structure of this invention exists in the point by which the said new pile is comprised so that the vertical load received from the said new frame and a horizontal load can be borne separately.

According to the above configuration, since the vertical load and horizontal load received from the new frame can be borne by the new pile, for example, the state of an existing pile or the like where it is difficult to determine the actual yield strength due to circumstances such as aging of the structure Regardless of the vertical load and the horizontal load received from the new frame can be appropriately handled by the new pile.
Nevertheless, the pulling force during an earthquake can be efficiently reduced by utilizing the weight of the existing housing that is easier to determine than the proof stress.

  The 3rd characteristic structure of this invention exists in the point which the connection area | region with the said new housing in the said existing housing is set to the area | region which has the weight according to the setting pulling-out resistance force to be expressed at the time of an earthquake.

In other words, the connection area of the existing chassis with the new chassis is highly integrated with the new chassis, so even if the existing chassis is broken by the pulling force during an earthquake, the dividing line is the boundary between the connected area and the non-connected area. The state where the connection area is connected to the newly installed frame is easily maintained by being located in the vicinity.
Therefore, according to the above configuration in which the connection region is set in a region having a weight corresponding to the set pulling resistance force to be generated at the time of an earthquake, at least the set pulling resistance force can be applied with a high probability. Safety against pulling force can be further enhanced.

  The 4th characteristic structure of this invention exists in the point by which the connection of the said new housing and the said existing housing is performed between mutual underground outer walls.

  According to the above configuration, the underground outer walls of the new structure and the existing structure are in a posture along the vertical direction (longitudinal direction), which is the direction of action of the pulling force during the earthquake of the new pile. Not only a highly versatile connection structure, but also a connection structure in which an engaging part that restricts the relative movement of the concave and convex parts between the opposing surfaces of both underground walls is provided, and friction between the two underground walls It is also possible to employ a connection structure such as a connection structure that increases the resistance and suppresses the relative movement between the two. Therefore, it is possible to employ an appropriate connection structure according to the state of the existing housing, the building plan, and the like.

  And when adopting a highly versatile connection structure that spans connecting members such as anchors and reinforcing bars, it is possible to suppress the occurrence of groundwater problems compared to connecting the foundations of the new frame and the existing frame. However, it is possible to accurately realize the pulling resistance force using the weight of the existing frame in the form of appropriately transmitting with the shear strength of the connecting member, and to effectively reduce the pulling force at the time of earthquake acting on the newly installed pile.

Longitudinal section of pile foundation structure Longitudinal sectional view of the main part showing another embodiment of the pile foundation structure

An embodiment of a pile foundation structure according to the present invention will be described based on the drawings.
As shown in FIG. 1, this pile foundation structure is joined to the existing frame 1 left under the construction site G, the new pile 2 built in the ground of the construction site G, and the new pile 2. The newly constructed housing 3 is provided as a main component, and can be suitably used when rebuilding from an existing building to a new building at the construction site G. And the said pile foundation structure bears the vertical load and horizontal load which are received from the new frame 3 in the new pile 2, and reduces the pulling-out force at the time of the earthquake which acts on the new pile 2 using the weight of the existing frame 1 It is configured as follows.

  The said existing frame 1 is left in the basement of the construction site G without deliberately demolition at the time of demolition work of an existing building. The existing housing 1 may be any structure such as RC structure (steel reinforced concrete structure), SRC structure (steel reinforced concrete structure), S structure (steel structure), or a composite structure thereof. It consists of an existing foundation 11 and an existing underground outer wall 12.

  Moreover, in this pile foundation structure, since it is sufficient if only the weight of the existing frame 1 can be used, the support structure of the existing frame 1 may be any structure, but in the illustrated example, it is built under the existing foundation 11. It is the structure which supports the existing frame 1 with the existing pile 4 embedded. The existing pile 4 is composed of, for example, a plurality of on-site casts or existing concrete piles that are dispersedly arranged in a region below the bottom surface of the existing foundation 11.

  The new frame 3 is newly constructed in the construction site G after the dismantling work. In the example shown in the figure, an RC new foundation 31 and a new underground outer wall 32, a steel column 33 and a beam 34, an RC structure The column base part 35 is comprised. The new housing 3 can also be configured by various structures such as RC structure, SRC structure, S structure, and a composite structure thereof. Further, in the illustrated example, the steel pillar 33 is inclined in order to position the column base of the pillar 33 directly above the new pile 2, but the new foundation 31, the pillar 33 and the like are required. Thus, the present invention can be suitably implemented even when the pillar 33 is vertical.

  A backfill material 5 for adjusting the installation height of the new foundation 31 to the design height is filled between the existing chassis 1 and the newly installed chassis 3 and mainly between the existing foundation 11 and the new foundation 31. . As the backfill material 5, various materials such as fluidized soil, excavated soil, dismantled glass, gravel, and crushed stone can be used as appropriate according to the construction plan and the like.

The new pile 2 is newly built in the ground of the construction site G after the dismantling work. For example, a plurality of on-site or existing concrete piles distributed in the area below the bottom surface of the new foundation 31 Etc.
The new pile 2 is configured to be able to bear a single load without causing the existing pile 4 to bear the vertical load and the horizontal load received from the new frame 3. Specifically, specifications such as a pile diameter, a pile length, and the number of the new pile 2 are set so that the vertical load and the horizontal load received from the new frame 3 can be borne separately.

The pile head joint 6, which is a joint between the pile head 21 of the new pile 2 and the new foundation 31, has various joint structures such as a rigid joint structure and a semi-rigid joint structure in which the degree of rotational restraint is relaxed. Can be adopted.
In this respect, this pile foundation structure uses the weight of the existing frame 1 to reduce the pullout force during an earthquake, so a semi-rigid joint structure is sufficient as a proof against the pullout force during an earthquake, but in this embodiment A rigid joint structure reinforced with pile head reinforcement bars (not shown) is employed to increase the safety of the pile head joint 6 against an earthquake pull-out force.

  And in this pile foundation structure, the new structure 3 is connected to the existing structure 1 by the connection part 7 in the state by which the weight of the existing structure 1 becomes a resistance element to the pulling-out force at the time of an earthquake. By connecting the new frame 3 and the existing frame 1 at the connection portion 7 in this manner, it is possible to reduce the earthquake pull-out force acting on the new pile 2 by using the weight of the existing frame 1 as a resistance element in the event of an earthquake. it can.

  The connecting portion 7 between the new housing 3 and the existing housing 1 has various structures in which the weight of the existing housing 1 is added to the new housing 3 as a movement resistance force at least when the new housing 3 is to move upward. Can be adopted.

  In the present embodiment, the connecting portion 7 includes an anchor, a reinforcing bar and the like that extend in the lateral direction to the newly installed underground outer wall 32 along the vertical direction (vertical direction) of the newly installed housing 3 and the existing underground outer wall 12 along the vertical direction of the existing housing 1. The connecting member 71 is interposed. The newly installed housing 3 and the existing housing 1 are connected via the connecting member 71 so as not to be relatively movable.

  In this way, when the newly installed chassis 3 is to move upward by connecting the newly installed underground outer wall 32 of the newly installed chassis 3 and the existing underground outer wall 12 of the existing chassis 1 via the connecting member 71, the connecting member 71. Thus, the weight of the existing housing 1 is appropriately added as a movement resistance force by the shear strength of the connection member 71, and as a result, the pulling force at the time of earthquake acting on the new pile 2 can be suitably reduced.

The connection area A (the gray display portion in the figure) of the existing chassis 1 with the newly installed chassis 3 is set pullout resistance force that is developed during an earthquake in consideration of the possibility of the existing chassis 1 being broken by the pullout force during an earthquake. It is set to the area | region which has the weight according to.
Here, the connection region A of the existing housing 1 is a region directly connected to the new housing 3 by a large number of connection members 71. In the present embodiment, the weight corresponding to the set pulling resistance force (that is, the weight that expresses the set pulling resistance force at the time of an earthquake) is the weight of the upper half side of the existing underground outer wall 12, so A region on the upper half side of the existing underground outer wall 12 is a connection region A as a region having a weight.

  Since the connection region A directly connected to the new housing 3 in this way is highly integrated with the new housing 3, even if the existing housing 1 is parted and broken by the pulling force during an earthquake, the parting line is connected to the connection region A. It is easy to maintain the state where the connection area A is connected to the new housing 3 by being positioned near the boundary between A and the non-connection area. That is, the weight of the connection region A of the existing housing 1 is highly reliable and is maintained with a high probability as a resistance element against the pulling force during an earthquake. Therefore, at the time of an earthquake, this pile foundation structure can be made to act with a high probability of at least the set pulling resistance.

  The connection area A of the existing housing 1 can be set as appropriate depending on the set pulling resistance force to be developed during an earthquake. For example, when the set pulling resistance is set to a magnitude that does not cause any earthquake pulling force to the new pile 2, the connection region A may be a region having a weight that can completely cancel the earthquake pulling force, When the set pull-out resistance force is further reduced, the connection area A may be an area having a smaller weight.

  In order to avoid the destruction of the pile head joint 6, it is sufficient that the necessary weight is allocated to the necessary part. Therefore, the part facing the entire circumference of the newly installed chassis 3 in the existing chassis 1 is not necessarily the connection area A. For example, the connection region A is a flat surface, such as a region facing the specific region where the pull-out force of the new housing 3 is likely to be generated in the existing housing 1 or a portion facing the four corners of the new housing 3 as the connection region A. The arrangement can also be set appropriately.

The pile foundation structure configured as described above can be constructed by, for example, the following construction method.
First, the existing foundation 11 and the existing underground outer wall 12 of the existing building 1 are left in the basement of the construction site G, and the existing building is dismantled and removed. In addition, the existing frame 1 left in the basement of the construction site G is configured as a resistance element of the pullout force during earthquake in the pile foundation structure, but at the construction stage, a new earth retaining wall is not required and labor work is reduced. It is also effective in suppressing the discharge of groundwater.

Thereafter, the new pile 2 is built in a state of penetrating the existing foundation 11 with respect to the ground area below the bottom surface of the new foundation 31 of the new structure 3, and the upper surface of the existing structure 1 is set to the installation level of the new foundation 31. The backfill material 5 is filled on the existing foundation 11.
Then, a new foundation 31 of the new housing 3 is constructed on the backfill material 5. At this time, the pile head 21 is appropriately reinforced so that the pile head joint portion 6 has a desired joint structure.

Next, the pillar 33 and the beam 34 of the new frame 3 are assembled on the new foundation 31 of the new frame 3, and a large number of connection members 71 are arranged at substantially equal intervals with respect to the connection area A in the existing underground outer wall 12 of the existing frame 1. Embed and fix with.
Then, concrete is cast around the pillar 33 of the new housing 3 and the outer periphery of the new housing 3 to construct the column base 35 and the new underground outer wall 32. At this time, the part 36 between the column base part 35 and the connection area A places concrete integrally with the column base part 35 as a concrete beating part constituting the newly installed underground outer wall 32. By doing in this way, the new underground outer wall 32 and the column base part 35 can be constructed integrally while appropriately connecting the connection area A of the existing housing 1 and the new underground outer wall 32 via the connection member 71. .
The pile foundation structure according to the present invention can be constructed by the above steps.

[Another embodiment]
(1) In the above-described embodiment, the connecting portion 7 between the new housing 3 and the existing housing 1 has the connecting member 71 extending laterally between the new underground outer wall 32 of the new housing 3 and the existing underground outer wall 12 of the existing housing 1. Although the case where it is made to extend is shown as an example, it is not limited to this.

For example, as shown in FIG. 2A, the connecting portion 7 between the new housing 3 and the existing housing 1 has one or a plurality of concave portions 72 such as square grooves along the lateral direction on the existing underground outer wall 12 of the existing housing 1. The one or more convex part 73 which forms and enters the said recessed part 72 in the newly installed underground outer wall 32 of the newly installed housing 3 can be comprised.
In this way, when the new housing 3 is about to move upward, the weight of the existing housing 1 is moved by the convex portion 73 on the new housing 3 side and the concave portion 72 on the existing housing 22 side in the engaged state. As a result, it is appropriately added as a resistance force, and as a result, the pulling-out force at the time of earthquake acting on the new pile 2 can be suitably reduced. The connecting portion 7 is a convex portion that enters the recess 72 by constructing a new underground outer wall 32 by placing concrete with the existing underground outer wall 12 as a formwork in a state where the recess 72 is formed in the existing underground outer wall 12. Since the new underground outer wall 32 provided with the part 73 can be constructed, it can be constructed easily.

  In addition, the connecting portion 7 between the new housing 3 and the existing housing 1 is, for example, the inner surface of the existing underground outer wall 12 of the existing housing 1 is a rough surface having a high frictional force, and the outer surface of the new underground outer wall 32 of the new housing 3 The weight of the existing housing 1 is appropriately added as a movement resistance force by the frictional resistance between the outer surface on the new housing 3 side in contact with the inner surface on the existing housing 22 side. May be. This connecting portion 7 is also easily constructed by constructing a new underground outer wall 32 by placing concrete with the existing underground outer wall 12 as a formwork in a state where the inner surface of the existing underground outer wall 12 is roughened. can do.

  (2) In the above-described embodiment, a case where the connection area A (the gray display portion in the figure) of the existing chassis 1 with the newly installed chassis 3 is set in the upper half area of the existing underground outer wall 12 is taken as an example. Although shown, for example, as shown in FIG. 2 (b), the connection region A (gray display portion in the drawing) is added to the entire region of the existing foundation 11 and the existing underground outer wall 12 by adding a connection member 71 or the like. It may be set, and the connection area A can be appropriately set according to the set pulling resistance force to be developed at the time of an earthquake.

  (3) In the above-described embodiment, the case where the pile head joint portion 6 is configured with a rigid joint structure has been described as an example.

  (4) In the above-described embodiment, when the pulling-out resistance against the pull-out force at the time of earthquake is insufficient, the frame type of the new frame 3 is further changed to a frame type at which the pull-out force at the time of earthquake hardly acts on the new pile 2. A weight that resists the pulling force during an earthquake may be added to the new housing 3.

  (5) In the above-described embodiment, the case where the backfill material 5 is filled between the existing foundation 11 and the new foundation 31 is shown as an example, but the existing foundation 11 and the new foundation 31 are omitted by omitting the backfill material 5. You may comprise so that may touch.

  (6) In the above-described embodiment, the case where the foundation structure of the existing building is a pile foundation structure including the existing pile 4 is shown as an example, but a direct foundation structure not including the existing pile 4 may be used.

  (7) The connection part 7 between the newly established chassis 3 and the existing chassis 1 is the first connection method (see FIG. 1) for interposing the connection member 71 described above, and the second connection for forming the recess 72 and the projection 73 described above. The method (see FIG. 2 (a)) and the above-described connection method such as the third connection method in which the inner surface of the existing underground outer wall 12 of the existing housing 1 is a rough surface having a high frictional force can be suitably implemented. . For example, the first, second connection method, or the first to third connection methods may be combined, or when the first connection method or the second connection method is used, a simple third connection method is used. You may combine additionally. Various connection methods other than the first to third connection methods may be appropriately combined.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in a various aspect.

1 Existing frame 2 New pile 3 New frame 12 Existing underground outer wall 32 New underground outer wall A Connection area

Claims (4)

The existing structure left in the basement of the construction site,
A new pile built in the ground of the construction site,
A new structure joined on the new pile,
A pile foundation structure in which the new structure is connected to the existing structure in a state where the weight of the existing structure becomes a resistance element against the pulling force during an earthquake.   The pile foundation structure according to claim 1, wherein the new pile is configured to be capable of separately bearing a vertical load and a horizontal load received from the new frame.   The pile foundation structure according to claim 1 or 2, wherein a region of connection between the existing frame and the newly installed frame is set to a region having a weight corresponding to a set pulling resistance force to be developed during an earthquake.   The pile foundation structure according to any one of claims 1 to 3, wherein the connection between the new structure and the existing structure is performed between the outer walls of each other.

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