JP2012002026A - Base-isolation foundation structure using steel pipe pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem with a conventional pile foundation structure where a support part joining a foundation and a pile head with a pin joint involves an arrangement of each element of a spherical seat on both a steel pipe pile and the foundation in addition to ordinary reinforcement around the steel pipe pile at a side of the foundation, which requires a cumbersome work for installation and positional adjustment leading to complication as well as high cost.SOLUTION: The present invention comprises: a hollow steel pipe pile embedded in a vertical state with a prescribed length exposed above a construction ground; an abutment body which abuts on top of a pile head of the steel pipe pile in a vertical direction in a manner that the abutment body is free to move in a rotational direction; and a foundation section where concrete is cast to integrate the abutment body and the pile head with a prescribed gap on a circumference of an exposed section of the pile head. In addition, an opening edge of the pile head of the steel pipe pile is provided with a shape retaining member.

Description

  The present invention relates to a pile foundation structure that supports a foundation of a building by a steel pipe pile that is embedded in the ground, and particularly relates to a seismic isolation foundation structure that uses a steel pipe pile constructed so as to exhibit a seismic isolation function.

  According to the prior art, foundation piles, particularly pile foundation structures using steel pipe piles, are widely adopted as a structure that complements the lack of supporting ground strength in buildings of small buildings and ordinary houses.

  Nowadays, in these small-scale buildings, there is an increasing demand for providing a seismic isolation function that large-scale buildings (for example, high-rise buildings and high-rise apartments) have. This seismic isolation function is a function that prevents seismic energy from being transmitted to the building, unlike an earthquake resistance function that is the strength against shaking of seismic motion and a vibration control function that absorbs seismic energy. As a pile foundation structure for a small-scale building to obtain a seismic isolation function to meet this demand, "Pile foundation structure" in Patent Document 1 and "Pile head member for seismic isolation" in Patent Document 2 have been proposed and disclosed. .

  The “pile foundation structure” of Patent Document 1 forms a ball bearing portion at the head of the pile, and forms a spherical coupling portion corresponding to the ball bearing portion at the lower portion of the foundation separated from the pile. A sliding material is interposed between the part and the spherical joint, and the pile head joint is pin-supported (a structure in which stress is released by sliding rotation).

  In addition, the “pile head member for seismic isolation” of Patent Document 2 covers a short columnar member that is placed and fixed on the upper end surface of a steel pipe pile embedded in the ground, and covers this from the top surface to the steel pipe pile. It is a concave and convex spherical surface that has a receiving hole with a large inner diameter, the upper surface part is an upper lid member integrated with the foundation of the building, and the upper end surface of the short cylindrical member and the inner bottom surface of the upper lid member accept each other. It is characterized by touching. The space between the concave and convex spherical surfaces is a sealing structure in which a caulking material is enclosed.

Japanese Patent Laid-Open No. 10-227040 (page 3, FIG. 1) Japanese Patent Laid-Open No. 2003-27502 (page 2-3, FIG. 1)

  The pile foundation structure of these patent documents is such that the pile head can be rotated with respect to the foundation when the ground changes due to an earthquake by connecting the pile head to the pin, and the pile head and the foundation can slide horizontally. As a result, the transmission of seismic energy from the pile head to the foundation is reduced, and the effect of reducing the pile head bending moment is obtained. Note that when the pile head rotates with respect to the foundation, the pile head is not fixed in any direction with respect to the support section of the foundation, and if there is a relative rotational displacement between the pile and the foundation, the pile and foundation are bent. This means that no moment is generated, and the same meaning is used in the following description.

  However, the support part used as the pin joint of the pile head and foundation of these pile foundation structures is comprised by the spherical seat by the convex spherical surface and concave spherical surface which mutually slide. For this reason, the production of these ball seats is costly.

  Also, in addition to the normal bar arrangement on the foundation side around the steel pipe pile, each element of the ball seat is placed on both the steel pipe pile and the foundation, so its installation and alignment, and also caulking material between them In the case of interposing, the sealing work is necessary and complicated. Even though these works are small-scale buildings, a large number of steel pipe piles are required, so the number of work man-hours increases dramatically, construction time increases, and construction costs increase significantly.

  Therefore, the present invention pays attention to the above-described problems and provides a seismic isolation foundation structure using a steel pipe pile that has a relatively simple structure and is simple in construction.

  The base isolation structure using the steel pipe pile of the present invention (hereinafter abbreviated as “main foundation structure”) employs the following configuration in order to solve the above-mentioned problems.

  That is, a steel pipe pile with an internal cavity that is embedded in a standing manner with an exposed portion of a certain height on the construction ground, and a vertical contact with the pile head of the steel pipe pile, with free movement in the rotational direction And a base portion that is integrated by taking in the corresponding contact body and providing a fixed void region on the outer periphery of the exposed portion of the pile head.

  A shape-retaining member is disposed at the pile head opening edge of the steel pipe pile. The shape-retaining member is selected from either an inside-packed concrete filled from the opening edge of the pile head to a predetermined depth, a metal disk fitted to the pile head opening, or a reinforcing frame for correction.

  The abutment body is a frame that covers the pile head opening and is free to move in the direction of rotation with the pile head, more specifically, whether the outer contour shape is circular or polygonal from a wire rod such as a reinforcing bar. It is formed in a framework of some form. The frame body may be formed in a net shape by arranging a plurality of reinforcing bars that cross-connect the contours. This frame is a reinforcement against the lateral pressure from the steel pipe pile to the foundation side.

  Further, the gap region is filled with a buffer material. This cushioning material is configured by placing it as a mold frame for forming a void area in a steel pipe pile and a foundation portion formed by placing concrete around the steel pipe pile, and placing it as it is after placing concrete.

  Furthermore, a concrete edge cut surface is formed on the outer peripheral surface of a predetermined width from the upper end edge of the pile head exposed portion. This surface is formed by winding an insulating tape (bond breaker) having a predetermined width around the side peripheral surface of the steel pipe pile.

  The steel pipe pile and the foundation part are not rigidly joined by the contact body, the buffer material, and the insulating tape having the above-described configuration. This is because the movement in the rotation direction is free at the pile head of the steel pipe pile and the contact portion on the foundation side, and the side peripheral surface of the steel pipe pile is not integrally coupled by the cushioning material and the insulating tape. . As a result, the steel pipe pile only supports the foundation part in the vertical direction with the pile head, and the movement of the steel pipe pile in the rotational direction is free with reference to the contact body on the foundation part side.

  Furthermore, it is characterized in that a sliding layer is formed between the bottom surface of the foundation and the construction ground. The sliding layer is formed by interposing a sheet material having a small coefficient of friction between the lower surface of the foundation portion and the construction ground.

  In this foundation structure, the foundation is supported by the pile head of the steel pipe pile closed with a shape-retaining member, but the foundation and steel pipe piles are not rigidly connected. On the other hand, it is defined as a form that restricts movement in the displacement direction.) Moreover, the sliding layer is formed between the bottom face of the foundation part, and the construction ground. For this reason, when subjected to earthquake motion, a building supported by a spring called a steel pipe pile is displaced with a long period, small amplitude, and small acceleration different from the period, amplitude, and acceleration of the earthquake motion. As a result, this foundation structure exhibits a seismic isolation effect that makes it difficult to transmit seismic energy to the foundation, and thus to the building. Furthermore, in this foundation structure, there is no shaking or displacement due to wind pressure, which is a problem in lightweight base-isolated buildings, and there is no problem of large shaking due to resonance when long-period ground motion acts on the base-isolated building.

  The pile foundation structure of the present invention has been realized by using a ball seat that slides, rotates, and moves horizontally in order to exhibit the above-mentioned seismic isolation function, but this foundation structure is a steel pipe pile that closes the pile head. In addition to not rigidly joining the surrounding base portion, the above configuration is realized with a simple structure that forms a sliding layer. For this reason, compared with the conventional invention, it is possible to significantly reduce the construction time and construction cost of the entire pile foundation structure by reducing the number of parts and the number of work steps.

  In particular, in the construction industry for general housing, which originally aimed at construction of buildings with seismic isolation function on a low budget, the effect of reducing construction costs contributed to an increase in orders received, and the spread of this basic structure The contribution of safety and security to society is also remarkable.

It is sectional drawing which shows this foundation structure. FIG. 2 is an enlarged view of part A of FIG. 1. It is an assembly perspective view of the pile head part of the steel pipe pile of this foundation structure. It is the schematic which shows the construction condition of this foundation structure.

Hereinafter, specific embodiments of the basic structure will be described in detail with reference to the drawings.
FIG. 1 shows a cross section of the foundation structure 1 and shows a joint portion of a steel pipe pile 2 and a concrete foundation portion 6 placed around the steel pile pile 2.

  Reference numeral 2 denotes a steel pipe pile. The steel pipe pile 2 is a long hollow cylindrical body having a certain strength formed from a predetermined metal material (for example, “structural carbon steel”), and a part of the pile head side is exposed at a predetermined position of the ground 8. I let it penetrate and bury it. The height of the portion where the pile head is exposed (“exposed portion”) is set by optimal calculation in consideration of the rigidity of the steel pipe pile 2, the state of the ground 8, the state related to the foundation portion 6, and the like. In this embodiment, it is set to about 30 to 50 mm. Moreover, this steel pipe pile 2 forms the flat surface 21 closed by placing in-placed concrete 21a to a predetermined depth inside the pile head opening side. The filling concrete 21a is held by a pile cap 21b suspended inside from the opening of the pile head, and is prevented from dropping downward. The flat surface 21 is formed by arranging a metal plate crowned or fitted on the pile head of the steel pipe pile 2 or a reinforcing frame for correcting the shape of the opening edge on the inside or the outer periphery of the opening. Also good.

  A buffer material 3 is arranged on the side peripheral surface of the steel pipe pile 2 on the ground side. The buffer material 3 is a foamed polystyrene material having a ring shape whose diameter is expanded downward. The buffer material 3 obstructs the adhesion of the side peripheral surface of the steel pipe pile 2 on the ground side and the foundation portion 6 in the vicinity thereof, and the steel pipe pile 2 rotates with respect to the foundation portion 6 on the basis of the flat surface 21, particularly inclined When it is bent or bent, the interference between the side peripheral surface and the base portion 6 is prevented.

  An insulating tape 4 that is a bond breaker is wound around the side peripheral surface of the steel pipe pile 2 above the cushioning material 3. This insulating tape 4 prevents adhesion between the side peripheral surface of the steel pipe pile 2 excluding the buffer material 3 and the surrounding base portion 6. The width of the bond breaker is set to about 10 to 15 mm in the present embodiment in consideration of the height of the exposed portion.

  A sliding layer 5 is formed on the ground around the steel pipe pile 2. The sliding layer 5 is configured by laying one or more resinous sheet materials 51 having a small friction coefficient on the upper surface of the ground 8 and interposing a low friction material 52 between the sheet materials 51. . In addition, the sliding layer 5 is not limited to this embodiment example. For example, the sliding layer 5 is formed by laying a material that is engineeringly insulated from the ground, such as urethane foam, on the top surface of the mortar layer constructed on the ground top surface. good.

  Concrete is cast around the steel pipe pile 2 and on the upper side of the sliding layer 5 to form a foundation 6 having a predetermined shape. An abutment body 7 is disposed at a joint portion between the base portion 6 and the flat surface 21 of the steel pipe pile 2. The abutment body 7 is integrated into the base portion 6 and is integrated, and a frame body 71 formed from reinforcing bars as wire rods so as to surround the outer peripheral edge side of the steel pipe pile 2, and a steel pipe inside the frame body 71. The reinforcing bars 72 are arranged along the flat surface 21 of the pile 2. The abutment body 7 functions as a reinforcement against the bearing pressure from the steel pipe pile 2 to the foundation side and the side pressure acting on the contact surface between the foundation part 6 and the pile head when the steel pipe pile 2 receives a horizontal force. ing.

  The frame body 71 has a circular frame shape and is located away from the upper end edge of the steel pipe pile 2. The reinforcing bars 72 are arranged in a cross shape inside the frame 71, and positioning bars 73 are arranged at approximately four positions along the outer edge shape of the steel pipe pile 2 in a hanging manner.

Next, a specific construction procedure of the basic structure 1 will be described.
First, the steel pipe pile 2 having a predetermined length and a pile diameter is embedded in a predetermined position of the ground 8 with a part of the head side exposed.

  Next, the pile cap 21b is inserted into the exposed steel pipe pile 2 and the filling concrete 21a is placed to form the flat surface 21. At the same time, the sliding layer 5 is formed on the upper surface of the ground 8 around the steel pipe pile 2. Further, the buffer material 3 is arranged around the exposed portion of the steel pipe pile 2, and the insulating tape 4 is wound around the side peripheral surface of the remaining exposed portion.

  The contact body 7 is crowned while being positioned by the positioning bars 73 on the pile heads of the steel pipe piles 2, and a predetermined bar arrangement (not shown) on the base portion side is made to construct a formwork (not shown).

  After confirming that the filling concrete 21a forming the flat surface 21 of the steel pipe pile 2 is completely cured, the concrete is placed in the formwork to form the foundation portion 6 of a predetermined shape. Is completed.

  The height position of the lower surface of the constructed base portion 6, in other words, the formation position of the sliding layer 5 may be substantially coincident with the height of the surrounding ground 8. In this case, as shown in FIG. 4, the end portion side of the base portion 6 needs to be filled 9 in consideration of freezing in winter.

  In the foundation structure 1 having the above-described configuration, the steel pipe pile 2 and the foundation portion 6 are not rigidly joined. That is, the steel pipe pile 2 only supports the load in the vertical direction of the base portion 6 by the contact body 7 to which the flat surface 21 is joined, and is rotatable with respect to the base portion 6. This is because the foundation-forming concrete is placed after the filling concrete 21a forming the flat surface 21 of the steel pipe pile 2 is hardened. Moreover, it is because the side peripheral surface of the steel pipe pile 2 and the surrounding base part 6 are not adhering by the shock absorbing material 3 and the insulating tape 4. FIG.

  Since the steel pipe pile 2 and the foundation part 6 are not rigidly joined, the steel pipe pile 2 and the foundation part 6 can be regarded as pin joints that are substantially free to move in the rotational direction. When relative displacement occurs between the building and the ground due to earthquake motion, the spring constant of the steel pipe pile 2 embedded in the ground 8 is small compared to the case where the pile head is rigidly joined because the pile head is pin-joined. The natural period of the entire building is longer. As a result, both the amplitude and acceleration are smaller than the displacement of the ground 8, the transmission of seismic energy to the foundation part is reduced, and the seismic isolation function is exhibited.

  Moreover, this foundation structure 1 does not produce a pile head moment, and a bending stress and a torsional stress also arise in the foundation part 6 by the structure, even if a rotational displacement arises in the steel pipe pile 2 at the time of the action of a horizontal load. Moreover, the pile head and the base part 6 do not interfere with the buffer material 3 arranged on the side peripheral surface of the steel pipe pile 2, and both damages are suppressed.

  The sliding layer 5 formed between the ground 8 and the lower surface of the foundation part reduces the frictional force and adhesive force to the foundation part 6 of the ground 8 to reduce the transmission of earthquake motion from the ground 8 to the foundation part 6. As a result of making the part 6 and the ground 8 difficult to vibrate in synchronization, the seismic isolation function is further enhanced. Moreover, when the lower surface height of the base part 6 is made to correspond with a peripheral ground, the passive earth pressure from the base part 6 to the ground 8 is made small by this positional relationship, and the transmission of seismic energy is reduced.

DESCRIPTION OF SYMBOLS 1 This foundation structure 2 Steel pipe pile 21 Flat surface 21a Filled concrete 3 Buffer material 6 Foundation part 7 Contact body 71 Frame body 8 Ground

  According to the prior art, foundation piles, particularly pile foundation structures using steel pipe piles, are widely adopted as a structure that complements the lack of bearing ground strength in small buildings and general residential buildings.

  Reference numeral 2 denotes a steel pipe pile. The steel pipe pile 2 is a long hollow cylindrical body having a certain strength formed from a predetermined metal material (for example, “structural carbon steel”), and a part of the pile head side is exposed at a predetermined position of the ground 8. I let it penetrate and bury it. The height of the portion where the pile head is exposed (“exposed portion”) is set by optimal calculation in consideration of the rigidity of the steel pipe pile 2, the state of the ground 8, the state related to the foundation portion 6, and the like. In this embodiment, it is set to about 30 to 50 mm. Moreover, this steel pipe pile 2 forms the flat surface 21 closed by placing in-placed concrete 21a to a predetermined depth inside the pile head opening side. The filling concrete 21a is held by a pile cap 21b suspended inside from the opening of the pile head, and is prevented from dropping downward. The flat surface 21 is formed by arranging a metal plate crowned or fitted on the pile head of the steel pipe pile 2 or a reinforcing frame for correcting the shape of the opening edge on the inside or the outer periphery of the opening. Also good.

Claims (8)

An internal hollow steel pipe pile embedded in a standing configuration with an exposed part of a certain height on the construction ground,
A contact body disposed in contact with the pile head of the steel pipe pile in the vertical direction with free movement in the rotational direction;
A foundation portion that is integrated by taking in the contact body and placing a fixed void area on the outer periphery of the exposed portion of the pile head; and
Base-isolated base structure using steel pipe piles.   The seismic isolation foundation structure using a steel pipe pile according to claim 1, wherein a shape retaining member is disposed at an opening edge of the pile head of the steel pipe pile.   3. The shape-retaining member is either an inside-packed concrete filled from the opening edge of the pile head to a predetermined depth, or a fitted metal plate, or a reinforcing frame for correction. Base-isolated foundation structure using the steel pipe pile described.   2. A base-isolated foundation structure using a steel pipe pile according to claim 1, wherein the abutment body is a frame body that covers the pile head opening and is arranged to freely move in a rotational direction with respect to the pile head. .   5. The base-isolated foundation structure using a steel pipe pile according to claim 4, wherein the frame body is formed of a wire frame and the outer contour shape is a circular shape or a polygonal shape.   The seismic isolation foundation structure using a steel pipe pile according to claim 1, wherein the gap region is filled with a buffer material.   The base-isolated foundation structure using a steel pipe pile according to claim 1, wherein a concrete edge cut surface is formed on an outer peripheral surface having a predetermined width from an upper end edge of the pile head exposed portion.   2. A base-isolated foundation structure using a steel pipe pile according to claim 1, wherein a sliding layer is formed between the bottom surface of the foundation and the construction ground.

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