JP2005133423A - Concrete foundation support structure and pile foundation structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sufficient supporting force by a pile with a relatively simple structure for supporting a concrete foundation by a pile, to suppress a bending stress generated in a pile head and a foundation, and to reduce a cross section of the pile and the foundation; To further prevent pile head damage.
[Solution]
The bottom end 2a of the concrete foundation 2 abuts and supports the upper end of the pile 1 having an open upper end, thereby suppressing the transmission of tensile force and reducing the bending moment of the pile head. Further, a cup-shaped closing member 3 is attached to the upper end of the pile 1, and the closing member 3 is used as a substitute for a formwork so that a part of the concrete foundation 2 protrudes into the pile 1, and the protruding portion 2 b Ensure the ability to transmit external force in the horizontal direction. Furthermore, by preventing the lower part of the protruding portion 2b from coming into contact with the inner wall 1c of the pile 1, the generation of a bending moment due to a so-called lever action is suppressed.
[Selection] Figure 1

Description

  The present invention relates to a concrete foundation support structure using piles.

  As a support structure for a concrete foundation such as a concrete slab by a pile, a structure in which both are rigidly connected is widely known. In the case of this rigid joint, since the main reinforcement of the pile is generally fixed to the concrete foundation, the concrete foundation can be sufficiently supported by the pile. However, since the pile head of the pile is restrained by the concrete foundation, if a large external force is applied due to an earthquake or the like, the bending moment increases at the pile head, which may cause damage. In order to prevent such damage, reinforcement measures such as disposing more reinforcing bars on the pile head are necessary, and there are problems in terms of cost increase and construction work. In view of this, various support structures have been proposed to reduce the degree of fixation of the joint portion in order to reduce the bending moment applied to the pile head. For example, Patent Document 1 proposes a method in which a pile head of a hollow pile is abutted against the bottom surface of the foundation slab and a part of the foundation slab is inserted into the pile.

JP 2002-275915 A

  In the structure of Patent Document 1, while a relatively simple structure and a high transmission capability with respect to the shearing force from the foundation slab to the pile can be obtained and sufficient supporting force can be obtained, the bending moment generated in the pile head is the same as that of the foundation slab. It is limited to the bending bending moment caused by the pile head bearing pressure, and it is possible to prevent the tensile force from the foundation slab from being applied to the pile head, so that the pile head can be prevented from being damaged. However, even with the structure of Patent Document 1, there is room for improvement in order to further improve the shearing force transmission capability from the foundation slab to the pile and further suppress the bending moment applied to the pile head.

  An object of the present invention is to obtain a sufficient support force by a pile with a relatively simple structure, to suppress the bending stress generated in the pile head and the foundation, to reduce the cross section of the pile and the foundation, and to prevent the pile head from being damaged. It is to plan further.

  According to the present invention, in a support structure for a concrete foundation that supports the upper end of a pile having an open upper end on the bottom surface of a concrete foundation, the pile is attached to the upper end of the pile and closes the upper end. Provided with a cup-shaped closing member projecting into the interior of the pile, wherein the concrete foundation has a projecting portion defined by the closing member and projecting into the pile, and the side surface of the closing member is an inner wall of the pile. There is provided a support structure for a concrete foundation which is formed so as to be in contact with the inner wall within a predetermined range from the upper end while being separated from the lower range from the predetermined range.

  In the present invention, it is preferable that the side surface of the closing member is tapered toward the lower side so that a part in the middle of the side surface is fitted to the upper end of the inner wall.

  Moreover, in this invention, steel materials can also be arrange | positioned from the said protrusion part toward the said concrete foundation toward the upper direction rather than the bottom face of the said concrete foundation.

  Moreover, in this invention, the transmission member which transmits the tensile force from the said concrete foundation with respect to the said pile can also be provided in the said pile.

  Moreover, according to this invention, it is the pile foundation structure which mixed the 1st and 2nd support structure of the concrete foundation which collides and supports the said upper end of the pile which the upper end opened on the bottom face of a concrete foundation, The first and second support structures include a cup-shaped closing member that is attached to an upper end of the pile, closes the upper end and protrudes into the pile, and the concrete foundation is attached to the closing member. The closing member has a protruding portion that is defined and protrudes into the inside of the pile, and the side surface of the closing member is in contact with the inner wall within a predetermined range from the upper end of the inner wall of the pile. The pile foundation structure is formed so as to be separated from each other, and the second support structure is further provided with a transmission member for transmitting a tensile force from the concrete foundation to the pile. Provided by It is.

  According to the present invention, a sufficient support force by a pile is obtained with a relatively simple structure, the bending stress generated in the pile head and the foundation is suppressed, the cross section of the pile and the foundation is reduced, and the pile head is prevented from being damaged. Can be further improved.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
FIG. 1A is a structural diagram of a support structure A according to an embodiment of the present invention. The support structure A is a pile 1 that supports a concrete foundation 2 such as a footing or a concrete slab. In this embodiment, the pile 1 is a ready-made concrete pile formed in a hollow cylindrical shape, and includes a pile main body 1a and an end steel plate 1b provided at the upper end of the pile main body 1a, leaving a pile head portion. Embedded in the ground. The pile main body 1a is made of cylindrical concrete, and the end steel plate 1b is formed in a disc shape in accordance with the end face shape of the pile main body 1a. Therefore, the upper end of the pile head of the pile 1 is open and opened in a circular shape. And the concrete foundation 2 is supported by the pile 1 because the pile head upper end surface of the pile 1 and the bottom face 2a of the concrete foundation 2 collide. That is, in the support structure A of the present embodiment, the concrete foundation 2 is supported in a mounted state on the pile head of the pile 1, and the concrete foundation 2 is simply placed on the pile 1, There is no member that substantially transmits the tensile force in the direction of the pile axis between the concrete foundation 2 and the pile 1 such as reinforcing bars extending from the pile 1. In addition, in this embodiment, the cylindrical ready-made concrete pile is illustrated as the pile 1, However, Other types and piles of another shape like a steel pipe pile and a steel pipe concrete pile are also employable.

  The closing member 3 is a member for closing the upper end of the pile head of the pile 1, and is a cup-shaped member protruding inside the pile 1. The closing member 3 is preferably made of, for example, a metal such as iron or aluminum, plastic, or the like. In the present embodiment, it is assumed that the closing member 3 is made of steel. FIG. 1B is an external perspective view of the closing member 3. The closing member 3 has a bottomed cylindrical shape, and closes the edge 3a protruding sideways so as to rim the opened upper end, the cylindrical side wall 3b, and the lower end of the side wall. The bottom portion 3c is integrally formed. The closing member 3 is configured along the shape of the pile 1 in order to close the upper end of the pile head of the pile 1, and since the pile 1 of this embodiment is cylindrical, it is configured in a circular shape accordingly. Yes. The edge portion 3a has a diameter larger than the opening diameter of the upper end of the pile head, and the edge portion 3a is locked to the upper end surface of the pile head of the pile 1 as shown in FIG. The closing member 3 can be mounted on the upper end of the pile head simply by placing the closing member 3 on the upper end of the pile head so as to be inserted into the pile 1. That is, in this embodiment, fixing with respect to the pile head upper end of the closing member 3 with a volt | bolt etc. is unnecessary. The depth of the closing member 3 to the bottom 3c (distance from the bottom 2a to the bottom 3c) is set so as to exert an effect that shearing force is transmitted from the concrete foundation 2 to the pile 1 as will be described later. For example, it is preferably about 50 mm to 200 mm.

  The side wall 3b is formed in a tapered shape so that its diameter gradually decreases downward in the pile axis direction. That is, the side wall portion 3b forms a tapered cylindrical body, and as shown in FIG. 1A, the cross section thereof is inclined substantially linearly with an angle θ with respect to the vertical direction. The side wall 3b is tapered in this way because the side surface of the closing member 3 (that is, the outer peripheral surface of the side wall 3b) extends in the direction of the pile axis from the upper end of the inner wall 1c of the pile 1 (that is, the inner peripheral surface of the pile 1). This is to make contact with the inner wall 1c in a predetermined range below, while being further separated from the predetermined range in the range below the pile axis direction. Such a configuration shows the side wall 3b in the present embodiment. Thus, it can implement | achieve simply by setting it as a tapered shape. In the case of this embodiment, since the cross section of the side wall portion 3b is tapered such that the side wall 3b is linearly inclined, the side surface of the closing member 3 and the inner wall 1c of the pile 1 are substantially the same when viewed in cross section at the upper end portion of the inner wall 1c. It touches at a point (approximate line as a whole), and is separated below it. Thus, in order to contact the side surface of the closing member 3 and the inner wall 1c of the pile 1 at the upper side and to be separated at the lower side, the configuration is not limited to the configuration of the present embodiment, and various configurations can be adopted. For example, it is good also as a taper shape that the cross section of the side wall part 3b inclines in a curve.

  In the present embodiment, an edge 3 a is provided at the upper end of the closing member 3, the edge 3 a is locked to the upper end surface of the pile 1, and the closing member 3 is mounted on the upper end of the pile 1 in a mounted state. Thus, the closing member 3 does not extend toward the upper side of the bottom surface 2a of the concrete foundation 2, but a configuration in which the closing member extends can also be adopted. FIG. 4 is a configuration example employing a closing member 3 ′ configured to extend above the bottom surface 2 a of the concrete foundation 2 without providing the edge portion 3 a. In this closing member 3 ′, the side wall 3b ′ is extended upward from the bottom surface 2a of the concrete foundation 2, and the diameter of the extended portion has a diameter larger than the opening diameter of the upper end of the pile head, and It is formed so that the diameter becomes larger as it goes upward. For this reason, the closing member 3 ′ is mounted by being fitted into an open hole in the upper end of the pile head at a portion in the middle of the side wall portion 3 b ′. It is not necessary to fix the closing member 3 ′ thus configured to the upper end of the pile head with a bolt or the like, and it is sufficient to simply insert the closing member 3 ′ into the opened hole at the upper end of the pile head. Further, with such a configuration, since the closing member 3 ′ straddles the position of the bottom surface 2 a, the projecting portion 2 b is structurally reinforced, and the horizontal force from the concrete foundation 2 is transmitted from the projecting portion 2 b to the pile 1. The ability is improved, and in particular, if a steel member is used as the closing member 3 ′, the capacity is greatly improved. The distance d from the bottom surface 2a of the concrete foundation 2 to the upper end of the closing member 3 'is preferably about 50 mm to 100 mm, for example. Further, in the configuration example of FIG. 4, a configuration in which the reinforcing bar group is not provided in the protruding portion 2 b is adopted, but it goes without saying that the reinforcing bar group may be provided in the same manner as the configuration example of FIG. 1.

  Next, the concrete foundation 2 in the present embodiment is placed on the ground via the discarded concrete 5, and has a protruding portion 2b protruding into the pile 1 downward from the bottom surface 2a in the pile axial direction. The protrusion 2b is defined by the closing member 3. That is, the projecting portion 2 b is densely formed in the closing member 3 and has a shape along the inner surface of the closing member 3. The closing member 3 becomes a so-called formwork, and plays a role of forming the protruding portion 2b when the concrete foundation 2 is placed. In the case of this embodiment, the reinforcing bar group 4 which is steel materials is arrange | positioned by being embedded in the concrete foundation 2 from this protrusion part 2b toward the upper direction rather than the bottom face 2a. Since this reinforcing bar group 4 just straddles the position of the bottom surface 2a, the projecting portion 2b is structurally reinforced, and the integrity of the remaining portion of the concrete foundation 2 is improved.

  Next, the operation when an external force such as an earthquake is applied to the support structure A having such a configuration will be described. First, when a horizontal external force is applied to the concrete foundation 2, the protruding portion 2 b of the concrete foundation 2 protrudes into the pile 1, and the inner wall 1 and the closing member 3 at the upper end portion of the inner wall 1 c of the pile 1. Since this is in contact with the side surface of the slab, it is transmitted from the projecting portion 2 b to the pile 1 via the closing member 3. That is, the shear force is effectively transmitted from the concrete foundation 2 to the pile 1, and a sufficient supporting force can be obtained by the pile 1. In particular, in this embodiment, since the steel closing member 3 is used, a high shearing force transmission capability is exhibited by this and the projecting portion 2b made of concrete. Furthermore, in the case of this embodiment, since the protrusion 2b is reinforced by providing the reinforcing bar group 4, even if a strong external force acts in the horizontal direction, the damage of the protrusion 2b is suppressed, and the pile 1 is more effective. Can resist external force. On the other hand, in this embodiment, the concrete foundation 2 is supported by the pile 1 by the pile head upper end surface of the pile 1 and the bottom face 2a of the concrete foundation 2 colliding, and the concrete foundation 2 was simply placed on the pile 1. Therefore, although a load is transmitted to the pile 1 with respect to a compressive force (support pressure) in the vertical direction from the concrete foundation 2, the tensile force from the concrete foundation 2 is not substantially transmitted. Therefore, the bending stress generated at the pile head of the pile 1 is limited to the bending stress due to the bearing pressure, and the bending moment acting on the pile head is suppressed. Therefore, the pile head can be prevented from being damaged, and the cross section of the pile and the foundation can be reduced.

  Here, for example, as shown in FIG. 5, when the projecting portion 2 b is provided on the concrete foundation 2 and is simply projected into the pile 1, that is, the side surface of the projecting portion 2 b is connected to the inner wall 1 c of the pile 1. In the case of a structure that is in uniform contact, when an external force is applied to the concrete foundation 2, a so-called lever action occurs, and the protruding portion 2b presses the inner wall 1c of the pile 1 and the foundation is rotated. As a result, a frictional force acts between the protruding portion 2b and the inner wall 1c, the bending moment acting on the protruding portion 2b is increased, and cracks are generated at the root of the protruding portion 2b, thereby reducing the ability to transmit horizontal force. is there. However, in this embodiment, since the lower part of the side wall part 3b of the closing member 3 is the structure spaced apart from the inner wall 1c of the pile 1, rotation of the concrete foundation 2 with respect to the pile 1 is permitted, and it acts on the root of the protrusion part 2b. The bending moment to be suppressed can be suppressed, and the concrete surface of the projecting portion 2b is covered and reinforced by the closing member 3, so that the ability to transmit horizontal force can be maintained without causing damage to the projecting portion 2b.

  Next, the construction procedure of the support structure A will be described with reference to FIG. FIGS. 2A to 2C are diagrams illustrating a construction procedure of the support structure A. FIG. First, as shown in FIG. 2A, the pile 1 is embedded in the ground, and then the closing member 3 is attached to the upper end face of the pile 1. As described above, in the case of the present embodiment, the mounting is completed simply by placing the closing member 3 on the upper end surface of the pile head. Next, as shown in FIG. 2 (b), the reinforcing bar group 4 is arranged inside the closing member 3, and the discarded concrete 5 is placed on the ground. Next, a formwork (not shown) for placing the concrete foundation 2 is installed, and concrete is placed there. The placed concrete also flows into the closing member 3 to form a protruding portion 2b. After the concrete is hardened, the formwork is removed to complete the support structure A (FIG. 2 (c)). Thus, in the support structure A of this embodiment, it can be said that the workability is good because the other steps are the same as the construction of a general pile foundation only by installing the closing member 3. As described above, the support structure A of the present embodiment is a relatively simple structure in which the closing member 3 is substantially added to the conventional structure. In addition, the bending stress generated in the foundation can be suppressed, the pile head can be further prevented from being damaged, and the workability can be improved.

Second Embodiment
In the support structure A described above, the tensile force from the concrete foundation 2 is configured not to be transmitted to the pile head of the pile 1, but it may be better to transmit the tensile force at the application site of the pile foundation. Therefore, a transmission member that transmits the tensile force from the concrete foundation 2 to the pile 1 can also be provided. FIG. 3A is a structural diagram of a support structure B according to the second embodiment of the present invention that employs such a configuration. If only a structure different from the support structure A is demonstrated, as shown to Fig.3 (a), the several steel rod 6 is standingly arranged by the upper end of the pile 1. FIG. The lower end of the steel bar 6 is a bolt and is used to fix the steel bar 6 to the upper end face of the pile head of the pile 1. The remaining part of the steel bar 6 is embedded and fixed in the concrete foundation 2. For this reason, in the support structure B, the tensile force from the concrete foundation 2 is transmitted to the pile head of the pile 1 through the steel rod 6. The steel bar 6 may be provided in the pile 1 in advance, or may be provided before the concrete foundation 2 is placed on site. Thus, in the support structure B, the structure of the support structure A can be diverted to obtain a support structure that can transmit the tensile force from the concrete foundation 2 to the pile 1 with a structure in which the steel bar 6 is added. In the present embodiment, the steel rod 6 is used as a transmission member for transmitting the tensile force, but other members may be used as long as the tensile force can be transmitted.

<Pile foundation structure using support structures A and B>
Next, the pile foundation structure which concerns on one Embodiment of this invention is demonstrated with reference to FIG.3 (b). FIG. 3B is a layout diagram of a pile foundation structure according to an embodiment of the present invention in which support joint structures A and B are mixed. This pile foundation structure is a mixture of the joint structures A and B described above for a plurality of piles. The figure shows an example in which concrete foundations 2 that constitute a foundation for supporting a certain structure and that are supposed to be footed are arranged in 4 rows x 4 columns, and one pile 1 is assigned to each concrete foundation 2 one by one. It has been. As described above, the support structure A has a characteristic that the bending moment with respect to the pile head hardly acts and the pile head is prevented from being damaged. The support structure B is inferior to the support structure A in the prevention function of the pile head, but the concrete foundation 2 The supporting force with respect to the tensile force is strong in that the tensile force from is transmitted to the pile 1. Therefore, an ideal pile foundation structure can be obtained if the support structure B is supplementarily employed in a place where the tensile force is likely to act while the adoption of the support structure A is a keynote.

  In general, the tensile strength of the foundation of the structure is relatively large at the peripheral portion, but is relatively small at the central portion. In this embodiment, as shown in FIG. 3B, the support structure B described above is used for the four corner concrete foundation 2 where the tensile force is likely to act strongly, and the tensile force may act strongly. For the other low concrete foundation 2, the above-mentioned support structure A is adopted. By carrying out like this, the pile foundation structure which utilized each characteristic of the support structures A and B can be comprised. Moreover, since the structures of the support structures A and B are different only for the steel rod 6, the workability is not greatly deteriorated even if both are mixed. In addition, in this embodiment, although the support structure B is employ | adopted about the concrete corner 2 of four corners where possibility that a tensile force acts strongly, For example, the support structure B is employ | adopted also about the other concrete foundation 2. It is also possible to adopt various forms such as alternately providing the support structure A and the support structure B by skipping one or several.

(A) is a structural diagram of the support structure A according to an embodiment of the present invention, (b) is an external perspective view of the closing member 3. (A) thru | or (c) is a figure which shows the construction procedure of the support structure A. FIG. (A) is a structural diagram of the support structure B according to the second embodiment of the present invention, (b) is a layout diagram of a pile foundation structure according to an embodiment of the present invention in which the support structures A and B are mixed. FIG. 6 is a structural diagram showing an example in which a closing member 3 ′ is used for the support structure A. FIG. 2 is a structural diagram showing an example in which a protruding portion 2 b is provided on a concrete foundation 2 and is simply protruded into a pile 1.

Explanation of symbols

A, B Support structure 1 Pile 1a Pile body 1b End steel plate 2 Concrete foundation 3, 3 'Closure member 4 Reinforcing bar group 6 Steel bar

Claims (5)

In the support structure of a concrete foundation that abuts and supports the upper end of the pile whose upper end is open on the bottom surface of the concrete foundation,
A cup-shaped closing member that is attached to the upper end of the pile and closes the upper end and protrudes into the pile,
The concrete foundation has a protrusion defined in the closure member and protruding into the pile;
The closing member is formed so that a side surface thereof contacts the inner wall within a predetermined range from an upper end of the inner wall of the pile, and is spaced apart from the predetermined range below the predetermined range. Support structure.   2. The support structure for a concrete foundation according to claim 1, wherein the closing member has a side surface tapered toward a lower side so that a portion in the middle of the side surface is fitted to the upper end of the inner wall. .   The support structure for a concrete foundation according to claim 1 or 2, wherein a steel material is disposed on the concrete foundation from the projecting portion upward from the bottom surface of the concrete foundation.   The support structure for a concrete foundation according to any one of claims 1 to 3, wherein a transmission member for transmitting a tensile force from the concrete foundation to the pile is provided in the pile. A pile foundation structure in which the first and second support structures of a concrete foundation that abuts and supports the upper end of the pile whose upper end is open is supported on the bottom surface of the concrete foundation, the first and second Support structure is
A cup-shaped closing member that is attached to the upper end of the pile and closes the upper end and protrudes into the pile,
The concrete foundation has a protrusion defined in the closure member and protruding into the pile;
The closing member is formed so that a side surface thereof contacts the inner wall in a predetermined range from an upper end of the inner wall of the pile, while being separated in a lower range from the predetermined range,
The pile support structure, wherein the second support structure is further provided with a transmission member that transmits a tensile force from the concrete foundation to the pile.

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