JP5002403B2 - Foundation structure using existing and new piles - Google Patents

Description

  The present invention relates to a foundation structure using an existing pile and a new pile for constructing a new structure using a remaining existing pile when rebuilding the structure.

  When demolishing an old building and rebuilding it into a new building, if the pile of the existing building that remains in the ground is reused as a pile of a new building along with a new pile that is added at a specified location, It is economical because it can save a great deal of time required for removal and backfilling, and can also prevent the generation of a large amount of waste, which is preferable from the viewpoint of reducing the burden on the environment.

  However, according to the current standards, the above piles are obligated to prevent damage against earthquakes (hereinafter referred to as assumed earthquakes) that are likely to be encountered once during the lifetime of the new building. Pile is generally designed according to the old standard at the time of construction, which was not established, so it has the desired vertical support capacity, but lacks the horizontal resistance capacity against the above-mentioned assumed earthquake. Results In many cases, the piles cannot be reused under the same load conditions as the new piles.

  For this reason, for example, in the following Patent Document 1, an existing pile is used in combination with an existing pile, in which only the vertical load is borne and the new pile is loaded with both a vertical load and a horizontal load. The basic structure of a new building has been proposed.

  On the other hand, in the following Patent Document 2, in constructing the upper structure, the bottom surface of the upper structure and the upper end of the existing pile are separated vertically, and a cushioning material is interposed between them. By providing a shear key consisting of a round bar or the like that can support the load of the superstructure only on the newly built pile and transfer the horizontal force between the upper end of the existing pile and the superstructure. A method of rebuilding a building has been proposed in which the horizontal force of the superstructure is borne in the event of an earthquake.

  However, in the conventional foundation structure described in Patent Document 1, it is a structure that does not bear a horizontal load at all on the existing pile. On the other hand, in the building rebuilding method described in Patent Document 2, the existing pile is vertically Since these structures do not bear a load, the pile diameter and number of new piles to be placed in the construction of a new building will increase, and there are various problems in terms of workability and economy. It was.

In addition, in the rebuilding method described in Patent Document 2 in which a horizontal load is borne on the existing pile, the shear key is surrounded by the compressed cushioning material, so that the horizontal direction between the superstructure and the existing pile at the time of the earthquake is When relative displacement occurs, there is a problem that a large deformation performance cannot be obtained, and therefore the horizontal force cannot be borne by breaking before the desired shear strain is generated.
Japanese Patent Laid-Open No. 09-060007 JP 2002-256571 A

  The present invention has been made in view of such circumstances, and by allowing the existing pile to bear the corresponding vertical load and horizontal load, it can be reused by fully utilizing the performance of the existing pile. It is an object of the present invention to provide a foundation structure using an existing pile and a new pile that can reduce resources, construction period, or cost required for constructing a new pile.

In order to solve the above-mentioned problem, the invention described in claim 1 is to strike an existing pile or existing foundation remaining in the ground by removing an existing structure and a predetermined position separated from the existing pile or existing foundation. In the foundation structure using the existing pile and the new pile constructed on the existing pile or the new foundation constructed on the existing pile, the contact between the existing pile or the existing foundation and the new foundation At least one of the surfaces is formed with a recess having a constant depth that forms a gap between the two, and one end is fixed to the existing pile or existing foundation in the recess and the other end is the above The shear force transmission member fixed to a new foundation and yielding before the horizontal force borne by the existing pile reaches the proof stress of the existing pile is arranged.

Here, as the shearing force transmission member, a rod-shaped member using extremely low yield point steel is suitable, but depending on the depth of the concave portion or the like, a rod-shaped member made of steel such as ordinary steel or a large-diameter rebar Can also be used.
In addition, specifications such as the number, material, cross-section, length, etc. of the shear force transmitting members arranged in the recess may be selected so that the horizontal force borne by the existing piles will yield before reaching its proof strength. preferable.

  The invention according to claim 2 is the invention according to claim 1, wherein the concave portion is formed in a central portion of at least one of the contact surfaces of the existing pile or the existing foundation and the new foundation. It is characterized by.

  Furthermore, the invention according to claim 3 is the invention according to claim 1 or 2, wherein one end portion is inside the recess and on the outer peripheral side of the position where the shear force transmission member is disposed. The stopper is fixed to the existing pile or the existing foundation or the newly established foundation, and the other end portion is provided in the recess so as to protrude from the level of the contact surface.

  By the way, the distance between the other end of the stopper and the existing pile (or existing foundation) or the newly installed foundation that is displaced relative to the stopper is larger than the assumed earthquake according to the current standard described above. When the relative displacement occurs between the existing pile (or existing foundation) and the new foundation, the stopper may be set to a dimension that prevents the horizontal displacement by contacting the existing pile or the new foundation where the stopper is relatively displaced. preferable.

  Further, the invention according to claim 4 is the friction reduction for reducing friction between the existing pile or the existing foundation and the new foundation in the invention according to any one of claims 1 to 3. A member is interposed.

  According to the invention according to any one of claims 1 to 4, at least one of the contact surfaces of the existing pile (or existing foundation) and the new foundation is formed with a recess that forms a gap between them, Since the shear force transmitting member whose end is fixed to the existing pile (or existing foundation) and the new foundation is arranged in the recess, the contact surface between the two where the recess is not formed is arranged. Therefore, the existing pile can bear the vertical load from the new foundation.

  Further, when a horizontal force is applied during an earthquake, the shear force can be transmitted from the new foundation to the existing pile (or existing foundation) by the shear force transmitting member. At this time, since the shearing force transmitting member is disposed in the gap formed in the recess, a large deformation performance can be ensured. For this reason, it is possible to prevent early breakage by suppressing shear strain, and when large relative displacement occurs between the new foundation and existing piles by adjusting the strength of the shear force transmission member In addition, it is possible to improve the safety at the time of earthquake of the entire new structure constructed on the new foundation by yielding the shear force transmission member and absorbing the hysteresis energy.

  As a result, the existing pile can be loaded with appropriate vertical and horizontal loads, and the existing pile can be prevented from being damaged by the above-mentioned assumed earthquakes required by the current standards. It can be reused fully. This also reduces the vertical load and horizontal force that must be borne by the new pile, so that the cross section and the amount of reinforcing bars can be reduced, thereby reducing the resources, construction period, and cost required for construction. be able to.

  Here, as in the invention described in claim 2, if the concave portion is formed at the center of at least one of the contact surfaces of the existing pile (or the existing foundation) and the new foundation, the vertical load from the new foundation can be increased. It is suitable because it can be transmitted to an existing pile (or existing foundation) evenly over a large area.

  In the invention described in claim 3, since the stopper is provided inside the recess and on the outer peripheral side from the position where the shearing force transmitting member is disposed, it is larger than the assumed earthquake described above. Even in the event of an earthquake, the stopper restrains the horizontal displacement of the existing pile or the new foundation that is relatively displaced, thereby preventing the shear force transmission member from being excessively deformed and broken. it can.

  Furthermore, for existing piles where high axial force acts, such as existing piles directly under the pillar, the frictional force at the contact surface increases, resulting in shear force transmission by the shear force transmission member and its yield. There is a possibility that the history energy absorption is not smoothly performed. For such a part, as in the invention described in claim 4, if a friction reducing member is interposed between the contact surfaces, the frictional force is reduced and the shearing force transmitting member has a desired value. The function can be demonstrated.

(First embodiment)
1 to 5 show a first embodiment of a foundation structure using an existing pile and a new pile according to the present invention.
For example, as shown in Fig. 1, this foundation structure was applied when the existing building (structure) 1 with 6 stories above the ground was removed and replaced with a building 9 with 9 stories above the ground. An existing pile 3, a new pile 2 a placed at a predetermined position away from the existing pile 3, and a new foundation 5 constructed on the existing pile 3 are provided.

Here, as for the existing pile 3, the pile head part is beaten to the predetermined depth, the main reinforcement and the band reinforcement are removed, and the said new foundation 5 is constructed | assembled on it.
Furthermore, the hole 4 of the planar view shape which has a predetermined depth dimension is formed in the center of the contact surface 3a by the side of the existing pile 3 among the contact surfaces of the existing pile 3 and the newly installed foundation 5. ing. On the other hand, the contact surface 5a on the new foundation 5 side is also formed with a recess 6 having a slightly larger planar dimension than the hole 4 described above.

  In the recess 6 of the new foundation 5, a plurality of (3 × 4 = 12 in the figure) dowel steel materials (shearing force transmission members) 7 whose upper ends are embedded and fixed in the new foundation 5 are arranged. ing. Here, each dowel steel material 7 is a rod-shaped member having a square cross section made of extremely low yield point steel, and is formed to have a length that reaches the vicinity of the bottom of the hole 4 of the existing pile 3.

  Furthermore, a stopper 8 is provided on the outer peripheral side of the four sides in the hole 4 of the existing pile 3 and on the outer peripheral side of the dowel steel material 7. These stoppers 8 are made of rectangular steel plates, reinforcing bars, concrete, or the like, and are arranged at positions spaced apart from the side walls with the plate surfaces parallel to the side walls of the holes 4. Moreover, each stopper 8 is formed in the dimension which the height protrudes in the recessed part 6 of the new foundation 5. And the lower part of these dowel steel materials 7 and the stopper 8 is being fixed to the existing pile 3 with the grout 9 which is filled and solidified in the hole part 4 and block | closes the said hole part 4. FIG.

Here, the cross-sectional dimension of the dowel steel material 7 and the depth dimension of the concave portion 6 are set so that the horizontal force borne by the existing pile 3 when the assumed earthquake occurs is yielded before reaching the proof stress of the existing pile 3. Is set.
Moreover, the space | interval of the upper end part (other end part) of the stopper 8 which protrudes from the contact surfaces 3a and 5a to the recessed part 6 side and the side wall 6a of the recessed part 6 of the new foundation 5 should contact at the time of the said assumed earthquake. When the earthquake is larger than the assumed earthquake and a relative displacement occurs between the existing pile 3 and the new foundation 5, the stopper 8 contacts the side surface 6a of the new foundation 5 where the relative displacement occurs. The dimensions are set so as to contact and prevent the horizontal displacement.

  In order to construct the foundation structure having the above configuration, first the existing building 1 is dismantled, then the pile head of the existing pile 3 is rolled to a predetermined depth, the main bar is cut and the band is removed, and the existing pile is also removed. 3 is formed in the center of the upper surface of the hole 3. Next, after the dowel steel material 7 and the stopper 8 are installed at predetermined positions and levels in the holes 4, the grout 9 is filled to the level of the contact surface 3a and solidified. Instead of the grout 9, concrete or mortar may be filled.

  Next, the spacer shown by the code | symbol 10 in FIG. 3 is put on the upper surface of the existing pile 3 with which the hole part 4 was block | closed by this grout 9. FIG. The spacer 10 is for forming the concave portion 6 as a gap portion, and is a rectangular cylinder having a top plate. At this time, instead of the spacer 10, a foam material such as styrene or styrofoam may be used. And after installing this spacer 10 and arranging the new foundation 5, concrete is cast to construct the new foundation 5. As a result, a recess 6 is formed on the lower surface of the new foundation 5 to be a gap defined by the spacer 10.

  According to the foundation structure using the existing pile and the new pile having the above-described configuration, the contact surface 5a on the new foundation 5 side of the contact surfaces 3a and 5a of the existing pile 3 and the new foundation 5 is both A plurality of recesses 6 are formed in the gap 6 between which the upper end is fixed to the new foundation 5 and the lower end is fixed in the grout 9 that closes the hole 4 of the existing pile 3. Since the dowel steel material 7 is disposed, the existing pile 3 can bear a vertical load from the new foundation 5 through the contact surfaces 3a and 5a of the portion where the recess is not formed.

  As shown in FIG. 5, when a horizontal force acts during an earthquake, a shear force can be transmitted from the newly established foundation 5 to the existing pile 3 via the dowel steel material 7. At this time, since the dowel steel material 7 is disposed in the recess 6 serving as a gap, a large deformation performance can be ensured. For this reason, it is possible to suppress shear strain and prevent early breakage, and even when a large relative displacement occurs between the new foundation 5 and the existing pile 3, these dowel steel materials 7 are yielded. And the safety at the time of earthquake of the whole building 2 constructed | assembled on the new foundation 5 can also be improved by the hysteresis energy absorption.

  In addition, since the stopper 8 is provided on the outer peripheral side in the recess 5a and on the outer peripheral side from the arrangement position of the dowel steel material 7, even when an earthquake larger than the assumed earthquake described above occurs, By restraining the horizontal displacement by contacting the side surface 6a of the concave portion 6 of the new foundation 5 where the stopper 8 is relatively displaced, it is possible to prevent the dowel steel material 7 from being excessively deformed and broken.

  As a result, the existing pile 3 can be loaded with corresponding vertical and horizontal loads, and the existing pile 3 can be prevented from being damaged by the above-mentioned earthquake, and its performance can be fully utilized. Can be used. Thereby, since the vertical load and horizontal force which should be borne by the newly installed pile 2a can be reduced, the cross section and the amount of reinforcing bars can be reduced, thereby reducing the resources, construction period or cost required for construction. be able to.

(Second Embodiment)
6 and 7 show a second embodiment of the present invention. The same components as those shown in FIGS. 1 to 5 are denoted by the same reference numerals, and the description thereof is simplified.
This foundation structure shows an example applied when the vertical load (axial force) acting on the existing pile 3 is large, such as when the existing pile directly under the pillar or the building 2 to be rebuilt is a high-rise building. .

  That is, in this foundation structure, the outer peripheral portion of the existing pile 3 is formed by an annular inclined surface 3b that is gradually inclined downward toward the outside. The flat sliding member 11 made of Teflon (registered trademark) or the like is fixed to a flat portion surrounded by the inclined surface 3b, so that the surface of the sliding member 11 comes into contact with the contact surface 11a. It is said that.

  On the other hand, a sliding plate 12 having a size larger than that of the sliding material 11 and made of stainless steel plate or the like is fixed to the lower surface of the new foundation 5 facing the sliding material 11. It is set as the contact surface 12a. The sliding material 11 and the sliding plate 12 constitute a friction reducing member that reduces the friction between the existing pile 3 and the new foundation 5.

  It should be noted that between the sliding plate 12 and the lower surface of the new foundation 5 and / or slipping, for the purpose of adjusting the unevenness, so that the contact surfaces 11a, 12a of the sliding material 11 and the sliding plate 12 are almost in contact with each other. A plate-like member made of an elastic body such as rubber may be interposed between the material 11 and the upper surface of the existing pile 3. Further, the sliding material 11 may be provided on the lower surface of the new foundation 5 and the sliding plate 12 may be provided on the upper surface of the existing pile 3, and the inclined surface 3b is turned upside down to form a reverse taper on the new foundation 5 side. Also good. Further, the friction reducing member is not limited to the combination of the sliding material 11 and the sliding plate 12.

  According to the foundation structure having the above configuration, in addition to obtaining the same operational effects as those shown in the first embodiment, the new foundation 5 is also provided at a place where a large vertical load acts on the existing pile 3. By reducing the frictional force between the contact surfaces 3a and 5a, the dowel steel material 7 can exhibit the desired shear force transmission function and the energy absorption effect due to its yield. Moreover, since the pile head is made into a frustum shape by forming the annular inclined surface 3b on the outer peripheral portion of the existing pile 3, and the sliding material 11 is provided only in the central portion, the sliding material 11 is installed. Material costs can also be minimized.

(Other embodiments)
In addition, in the said 1st and 2nd embodiment, although all demonstrated only the case where the existing pile 3 was a solid pile, it is not restricted to this, For example, as shown in FIG. When 15 is a pile having a hollow cross section, the inside of the pile head is filled with filling concrete 16 and the hole 4 is formed on the top surface of the filling concrete 16 to place the dowel steel material 7 and the stopper 8. You can also

  Further, the present invention is not limited to the case where the new foundation 5 is constructed directly on the upper surface of the existing pile 3 and the above-mentioned foundation structure is applied between the two, but the existing building 1 is placed on the existing pile 3 as shown in FIG. In this case, it is possible to construct the new foundation 5 on the upper surface of the existing pile 17 with the existing pile 17 remaining. In this case, it is only necessary to form the hole 4 on the upper surface of the existing foundation 17 and arrange the dowel steel material 7 and the stopper 8.

  Further, the concave portion 6 is not necessarily limited to the case where it is provided on the new foundation 5 side, and may be formed on the upper surface of the existing pile 3 or the existing foundation 17, or the existing pile 3 (or the existing foundation 17). A recess that communicates with each other can be formed on both the foundation 5 and the new foundation 5. Moreover, in the foundation structure which concerns on this invention, although the dowel steel material 7 which transmits a horizontal force is provided between the existing pile 3 or the existing foundation 17 mentioned above, and the newly established foundation 5, the newly established pile 2a and newly established It is also possible to provide the dowel steel material 7 between the foundations as well.

  Moreover, the said structure of this invention can be diverted as a structure between the new pile and new foundation which wants to prevent the damage especially at the time of an earthquake in the foundation structure comprised only by a new pile.

It is a longitudinal cross-sectional view which shows the rebuilding of the existing building with which embodiment of this invention is applied, and arrangement | positioning of the existing pile and a new pile. It is a top view which shows arrangement | positioning with the existing pile and new pile in the new building by the rebuilding of FIG. It is a longitudinal cross-sectional view which shows the 1st Embodiment of this invention. It is the IV-IV sectional view taken on the line of FIG. It is a longitudinal cross-sectional view which shows the behavior at the time of the earthquake occurrence of the foundation structure of FIG. It is a longitudinal cross-sectional view which shows the 2nd Embodiment of this invention. It is a VII-VII line sectional view of Drawing 6. It is a longitudinal cross-sectional view which shows other embodiment of this invention. It is a longitudinal cross-sectional view which shows other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Existing building 2 New building 2a New pile 3, 15 Existing pile 3a, 5a, 11a, 12a Contact surface 5 New foundation 6 Concave part 7 Dowel steel material 8 Stopper 9 Grout 11 Sliding material (friction reduction member)
12 Sliding plate (friction reduction member)
17 Existing basics

Claims (4)

The existing pile or existing foundation left in the ground by removing the existing structure, the new pile placed at a predetermined position away from the existing pile or existing foundation, and the existing pile or existing foundation In the foundation structure using existing piles with new foundations and new piles,
At least one of the contact surfaces of the existing pile or the existing foundation and the new foundation is formed with a recess having a constant depth dimension that forms a gap between them, and one end of the existing pile is in the recess. Or, the other end is fixed to the existing foundation while being fixed to the existing foundation, and the shear force transmitting member that yields before the horizontal force borne by the existing pile reaches the proof stress of the existing pile is arranged. Basic structure using existing piles and new piles.   The foundation using the existing pile and the new pile according to claim 1, wherein the concave portion is formed in a central portion of at least one of the contact surfaces of the existing pile or the existing foundation and the new foundation. Construction.   One end is fixed to the existing pile, the existing foundation, or the new foundation inside the recess and on the outer peripheral side of the position where the shear force transmission member is disposed, and the other end is the recess. The foundation structure using the existing pile and new pile according to claim 1 or 2, wherein a stopper protruding from the level of the contact surface is provided.   The existing pile according to any one of claims 1 to 3, wherein a friction reducing member for reducing friction between the existing pile or the existing foundation and the new foundation is interposed. And foundation structure using new piles.

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