Pile foundation structure

Abstract

To provide a pile foundation structure allowing construction to be easily carried out as suppressing skeleton volume of a basement and an excavation amount of the ground.SOLUTION: A pile foundation structure 1 including a pile 3 and a pressure-resistant slab 6 supporting a building 2 is provided with: the pile 3; a column type foundation member 4 connected on a pile head part 3t of the pile 3 and disposed in the subsurface so as to extend upward from the pile head part 3t; a column 5 disposed on an upper part of the foundation member 4; the pressure-resistant slab 6 connected on a lower part of the foundation member 4; and a horizontal resistant member 7 connected on the foundation member 4 at a position above the pressure-resistant slab 6. A column leg part 51 of the column 5 is semi-rigidly connected on an upper surface of the foundation member 4 or the column leg part 51 of the column 5 is smaller in a sectional area than the foundation member 4 and both are rigidly connected to each other.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a pile foundation structure including piles and a pressure plate that support a building. [Background technology]

[0002] BACKGROUND ART When constructing a building, it is common to drive piles into the ground and then install a pressure plate on the ground to support the load of the building structure, so as to connect to the piles. For example, Patent Document 1 describes a configuration including foundation piles buried in the ground and a foundation slab as a pressure-resistant plate joined to the heads of the foundation piles. Patent document 2 also describes a configuration that includes a footing that is placed above the head of the pile and connected to a foundation beam, and a pressure plate that is provided in an area surrounded by the foundation beams that are connected to the footing. Furthermore, Patent Document 3 describes a configuration that includes an existing pressure plate supported by existing piles, improved ground laid on the existing pressure plate, and a concrete floor laid on the improved ground.

[0003] Here, when an earthquake occurs, a bending moment acts on the pile head of the pile. In Patent Documents 1 to 3, this bending moment must be resisted basically only by the pressure plate. Therefore, the pressure plate must be constructed to be robust and thick so that it can resist the bending moment. Furthermore, constructing such a pressure plate also requires deep excavation of the ground. Therefore, construction is not easy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7028728 [Patent Document 2] Patent Publication No. 2021-147883 [Patent Document 3] Patent No. 7129290 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a pile foundation structure that has excellent structural safety and can be easily constructed by reducing the amount of basement floor structure and the amount of ground excavation required. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention employs the following means. In other words, the pile foundation structure of the present invention is a pile foundation structure including piles that support a building and a pressure plate, and is provided with the piles and the pressure plate, a horizontal resistance member arranged above the pressure plate, a foundation member that is joined to the pile head of the pile and joins the pressure plate and the horizontal resistance member in the vertical direction, and a column arranged on top of the foundation member, and the column and the foundation member are joined by a core reinforcing bar that is arranged extending in the vertical direction between the foundation member and the column. According to the above-described configuration, the pressure plate, the horizontal resistance member disposed above the pressure plate, and the foundation member are joined vertically by the foundation member to form a robust, integrated structure with a consistent overall thickness. Because the columns are disposed on top of such foundation members, even if the columns are subjected to a large load, such as the perimeter columns of a building, the load can be transferred from above to below the pressure plate and the ground below the pressure plate. In this way, even for columns subjected to a large building load, the axial rigidity of the structure supporting the columns is increased, thereby improving structural safety. In the above-described configuration, the horizontal resistance members (floor slabs and beams) are joined to the foundation members at a position above the pressure slab. Therefore, the horizontal resistance members are joined to the foundation members at a position a certain height above the pile heads. In this configuration, when an earthquake occurs and a bending moment acts on the pile heads, this moment is transmitted to the pressure slab. At the same time, a couple acts on the horizontal resistance members, which are integrally formed with the pressure slab via the foundation members, at a different position from the bending moment at the pile heads and in the opposite direction to the bending moment. This couple cancels out the bending moment at the pile heads, reducing the bending moment. In this way, the bending moment at the pile heads, which should be resisted by the pressure slab, is reduced by the foundation members and the horizontal resistance members, eliminating the need to resist the bending moment solely with the pressure slab. Therefore, compared to when a foundation member is not provided, the pressure slab can be made thinner, thereby reducing the basement floor's structural mass and the amount of ground excavation required. Furthermore, the columns and foundation members are joined by core reinforcing bars extending vertically between the foundation member and the column. This allows the column to tilt relative to the foundation member around the core reinforcing bars during an earthquake, suppressing the horizontal force transmitted from the foundation member to the base of the column. This allows the above-ground building to maintain a certain degree of flexibility while enhancing structural stability against earthquakes and vibrations. In particular, suppressing the transmission of bending moments between the base and the foundation member reduces the need to make the foundation member unnecessarily strong in order to resist bending moments between the base and the foundation member. Therefore, when constructing the foundation member, the foundation member can be constructed more compactly by, for example, reducing the cross-sectional area of ​​the foundation member or reducing the number of shear reinforcement bars. The above effects combine to provide a pile foundation structure with excellent structural safety that can be easily constructed by reducing the amount of basement floor structure and the amount of ground excavation required.

[0007] In one aspect of the present invention, the column and the foundation member are semi-rigidly connected via the core reinforcing bar. With this configuration, it is possible to improve the durability and stability of the structure against earthquakes and vibrations while ensuring a certain degree of flexibility between the pillars and the foundation members. [Effects of the Invention]

[0008] According to the present invention, it is possible to realize a pile foundation structure with excellent structural safety that can be easily constructed by reducing the amount of basement floor structure and the amount of ground excavation required. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing the configuration of a building equipped with a pile foundation structure according to an embodiment of the present invention. [Figure 2] This is a structural floor beam plan of part II of Figure 1. [Figure 3] FIG. 2 is a longitudinal cross-sectional view taken along the line II-II in FIG. [Figure 4] FIG. 3 is a vertical cross-sectional view taken along the line III-III in FIG. 2. [Figure 5] FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. [Figure 6] FIG. 5 is a cross-sectional view of the portion viewed from the arrows VV in FIG. 4. [Figure 7] FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 3. [Figure 8] FIG. 7 is a vertical cross-sectional view taken along the line VII-VII in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention is a pile foundation structure including piles and a pressure plate. As shown in Figure 1, the pile foundation structure consists of a column-shaped foundation member and pressure plate placed between the pile and the ground-floor column, the pressure plate joined to the lower side of the foundation member, and a horizontal resistance member (floor slab or beam) joined to the upper side of the foundation member. In the pile foundation structure, the base of the column on the floor immediately above is semi-rigidly connected to the top surface of the foundation member, and the base of the column on the floor immediately above has a smaller cross-sectional area than the foundation member and is rigidly connected to both, and the pressure plate is rigidly connected to the column-shaped foundation member and the horizontal resistance member. The feature of this structure is that the bending moment acting on the pile head is resisted by the pressure plate and the column-shaped foundation member and horizontal resistance member placed above it working together, and by making the thickness of the pressure plate thinner, the amount of structure on the basement floor and the amount of ground excavation required are reduced. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the pile foundation structure according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a diagram illustrating the configuration of a building equipped with a pile foundation structure according to an embodiment of the present invention. As shown in Fig. 1, the pile foundation structure 1 according to this embodiment supports a building 2. More specifically, the pile foundation structure 1 includes piles 3, foundation members 4, columns 5, pressure plates 6 (see Fig. 3), and beams 7. The pile foundation structure 1 supports the columns 5 from below with the piles 3, foundation members 4, pressure plates 6, and beams 7.

[0011] FIG. 2 is a structural floor beam plan of part II of FIG. The building 2 of this embodiment has a rectangular shape such that its outer surface 2f, when viewed in a plane, extends in both a first direction D1 in a horizontal plane and a second direction D2 perpendicular to the first direction D1 in the horizontal plane. The columns 5 form the skeleton of the building 2. As shown in FIGS. 1 and 2, in this embodiment, the columns 5 are arranged on the outer periphery of the building 2. A plurality of columns 5 are provided at intervals in the horizontal direction along the outer periphery of the building 2. Each column 5 is provided so as to be exposed on the outer periphery 2f of the building 2. In other words, each column 5 forms part of the outer periphery 2f of the building 2. As shown in Figure 1, each column 5 extends in the vertical direction H. In the column base 51 of each column 5, the side surface 51s on one side in the column width direction along the outer peripheral surface 2f extends in the vertical direction H, whereas the side surface 51t on the other side in the column width direction extends at an angle from above to below so as to approach the column width direction center of the column 5. As a result, the column base 51 is formed so that the dimension in the column width direction along the outer peripheral surface 2f of the building 2 gradually decreases from above to below. In each pillar 5, in the portion 52 above the pillar base 51, the side surface 52s on one side of the pillar width direction and the side surface 52t on the other side of the pillar width direction extend in the vertical direction H, and the dimension in the pillar width direction is constant in the vertical direction H.

[0012] Adjacent columns 5 in the horizontal direction along the outer periphery 2f of the building 2 are connected via periphery beams 22 provided on each floor of the building 2. The periphery beams 22 are, for example, made of steel and extend in the horizontal direction along the outer periphery 2f of the building 2. An exterior wall (not shown) is formed between adjacent columns 5. In the building 2, the outer perimeter beams 22M provided on the intermediate floors of the columns 5 are vibration-damping beams with vibration-damping panels 26 provided at their central positions. These outer perimeter beams 22M formed as vibration-damping beams are disconnected from the floor slabs of each floor and are configured not to support the floor slabs.

[0013] Hereinafter, the structure of the pile foundation structure 1 in the portion viewed from arrow A in Figures 1 and 2 will be explained with reference to the drawings. The same explanation can be applied to other portions of the pile foundation structure 1. Fig. 3 is a longitudinal sectional view taken along the line II-II in Fig. 2. Fig. 4 is a longitudinal sectional view taken along the line III-III in Fig. 2. Fig. 5 is a cross sectional view taken along the line IV-IV in Fig. 3. Fig. 6 is a cross sectional view taken along the line VV in Fig. 4. As shown in Fig. 3, the pile 3 is installed in the ground G vertically below the pillar 5. The pile 3 is, for example, a concrete-filled steel pipe pile, and includes a steel pipe 31 extending in the vertical direction H and concrete (not shown) filled in the steel pipe 31.

[0014] The foundation member 4 is installed underground. The foundation member 4 is installed by extending upward from the pile head 3t of the pile 3. The foundation member 4 is formed so as to have a column shape extending in the vertical direction H. As shown in Figures 3 to 5, the foundation member 4 has a concrete portion 41, a plurality of bending reinforcement bars 42 embedded in the concrete portion 41, and a plurality of shear reinforcement bars 43 embedded in the concrete portion 41. In this embodiment, the concrete portion 41 is formed as a whole in the shape of a rectangular parallelepiped extending in the vertical direction H. As shown in FIGS. 3 and 5 , the concrete portion 41 is formed so as to protrude more outward than the pile head 3t of the pile 3. In other words, the cross-sectional area of ​​the foundation member 4 is larger than the cross-sectional area of ​​the pile 3. The pile head 3t of the pile 3 is buried below the concrete portion 41. A plurality of anchor bars 35 are joined to the steel pipe 31 of the pile 3 so as to extend upward from the pile head 3t. The plurality of anchor bars 35 are embedded in the concrete portion 41 of the foundation member 4 together with the pile head 3t. This allows the foundation member 4 to be firmly joined to the pile head 3t of the pile 3. The multiple bending reinforcement bars 42 extend in the vertical direction H. The lower end of each bending reinforcement bar 42 is provided at a position where it overlaps, in the vertical direction H, the pile head portion 3t of the pile 3, the anchor bars 35, and the pressure plate 6 described below. The upper end of each bending reinforcement bar 42 is provided at a position where it overlaps, in the vertical direction H, with the beam 7 described below. The multiple shear reinforcement bars 43 are provided at intervals in the vertical direction H. Each shear reinforcement bar 43 is provided within the concrete portion 41 so as to surround multiple bending reinforcement bars 42.

[0015] As shown in Figures 3 and 4, the foundation member 4 has a column support portion 45 at its upper portion. The column support portion 45 is formed in a shape that makes the concrete portion 41 protrude upward. The column support portion 45 is provided on the concrete portion 41. The column support portion 45 has a concrete portion 46, a plurality of anchor bars 47 embedded in the concrete portion 46, and horizontal bars 48 embedded in the concrete portion 46 and arranged perpendicular to the plurality of anchor bars 47. The plurality of anchor bars 47 protrude downward from the underside of the concrete portion 46 and are embedded in the concrete portion 41.

[0016] As shown in Figures 3 and 4, the column base 51 of the column 5 is disposed on the upper part of the column support part 45 of the foundation member 4. The column base 51 of the column 5 is semi-rigidly joined to the upper surface of the foundation member 4. As shown in Figures 3, 4 and 6, the column 5 has a concrete part 56, a plurality of column main reinforcements 57, and a plurality of shear reinforcement bars 58 embedded in the concrete part 56. The concrete portion 56 is formed in a rectangular shape in a plan view. The cross-sectional area of ​​the column base 51 of the column 5 is smaller than the cross-sectional area of ​​the concrete portion 41 of the foundation member 4. In other words, the cross-sectional area of ​​the foundation member 4 is larger than the cross-sectional area of ​​the column base 51.

[0017] In the base 51 of the column 5, the lower end of the concrete portion 56 is tapered to form an inclined surface 56s that slopes downward toward the center of the column 5. The inclined surface 56s is formed around the entire circumference of the column 5. That is, the inclined surface 56s is formed on both the surface of the concrete portion 56 along the column width direction (first direction D1) and the surface along the column thickness direction (second direction D2). The lower surface 56b of the concrete portion 56 of the column 5 is provided in contact with the upper surface 45t of the column support portion 45 of the foundation member 4. Styrofoam (registered trademark) 59 is provided between the inclined surface 56s and the upper surface 45t of the column support portion 45 so as to fill the gap between the inclined surface 56s and the upper surface 45t of the column support portion 45. In this embodiment, the Styrofoam 59 is provided as part of a formwork in order to form the inclined surface 56s when pouring concrete to form the concrete portion 56. The Styrofoam 59 may be removed after the concrete portion 56 including the inclined surface 56s has been formed, or may be left as is.

[0018] A plurality of column main reinforcements 57 are embedded in the concrete portion 56 at the outer periphery of the column base 51 of the column 5. As shown in FIG. 4 , among the plurality of column main reinforcements 57, column main reinforcements 57S provided on one side in the column width direction (first direction D1) extend in the vertical direction H. Among the plurality of column main reinforcements 57, column main reinforcements 57T provided on the other side in the column width direction extend parallel to the side surface 51t, obliquely extending from above downward so as to approach the center of the column 5 in the column width direction. The lower ends of the plurality of column main reinforcements 57 terminate within the concrete portion 56. In other words, the plurality of column main reinforcements 57 do not protrude downward from the concrete portion 56, and are not embedded in the foundation member 4 below. The multiple shear reinforcement bars 58 are embedded in the concrete portion 56 at intervals in the vertical direction H. Each of the multiple shear reinforcement bars 58 is provided so as to surround multiple column main reinforcements 57. As will be explained later, the column 5 is semi-rigidly connected to the column support portion 45 so as to be able to tilt relative to the foundation member 4. When an earthquake occurs and the column 5 tilts, a large compressive force acts on the lower end of the column base 51 of the column 5, which contacts the foundation member 4. To resist this, the shear reinforcement bars 58 are provided in a concentrated manner, particularly near the lower end of the column base 51.

[0019] The pile foundation structure 1 of this embodiment further includes a plurality of core reinforcing bars 8. The plurality of core reinforcing bars 8 are provided at the joint between the foundation member 4 and the column 5. The plurality of core reinforcing bars 8 are provided in the center of the column 5 when viewed in a plan view as shown in FIG. 6. The core reinforcing bars 8 are arranged side by side in the column width direction (first direction D1) at intervals, for example, three core reinforcing bars. The core reinforcing bars 8 are arranged side by side in the column thickness direction (second direction D2) that is perpendicular to the column width direction in the horizontal plane, for example, two core reinforcing bars. As shown in FIG. 3, each core reinforcing bar 8 is arranged extending in the vertical direction H between the foundation member 4 and the column 5. The upper end 8t of each core reinforcing bar 8 protrudes upward from the foundation member 4 and is embedded in the column 5. The lower end 8b of each core reinforcing bar 8 is embedded in the foundation member 4. The lower end 8b of each core reinforcing bar 8 is located at the bottom of the foundation member 4, above the pile head portion 3t of the pile 3.

[0020] With the above-described configuration, the concrete portion 56 of the column 5 and the concrete portions 41, 46 of the foundation member 4 are not integrally formed but are separate, different concrete bodies. Therefore, the column 5 and the foundation member 4 (column support portion 45) are joined only by the core reinforcing bar 8 provided in the center of the column 5, as described above. Therefore, if an earthquake occurs and a horizontal force acts on the pile 3, displacing the foundation member 4 along with the pile 3 in the horizontal directions D1, D2, the column 5 will tend to remain in place due to inertial force. As a result, the upper surface 45t of the foundation member 4 and the lower surface 56b of the column 5 will separate from each other, with the opposite side lifting upward around a point on the outer periphery of the lower surface 56b of the column 5. In this way, the column 5 tilts and inclines relative to the foundation member 4. Here, since the lower end of the pillar 5 is tapered with the inclined surface 56s as described above, the tilting movement as described above can be carried out smoothly. In this way, the pillar 5 is semi-rigidly joined to the foundation member 4 and is provided so as to be tiltable relative to the foundation member 4.

[0021] As described above, the column 5 is semi-rigidly joined to the column support portion 45 so as to be tiltable relative to the foundation member 4, and there is no joint between the lower surface 56b of the column 5 and the upper surface 45t of the foundation member 4 (of the column support portion 45). Therefore, there is a possibility that rainwater may enter from outside the building 2 through this interface. To prevent this, when the column 5 is located particularly on the periphery of the building 2 as in this embodiment, it is preferable to seal the joint between the column base portion 51 of the column 5 and the foundation member 4 with an appropriate sealant for waterproofing. In addition, it is desirable to apply an anti-rust coating to the surface of the core reinforcing bar 8 in the vicinity of this interface in the vertical direction H, to prevent the core reinforcing bar 8 from rusting due to water that has entered the interface. Furthermore, in this embodiment, the concrete portion 46 has a step portion 45d that protrudes upward on the inside side of the building 2. This prevents rainwater from further infiltrating into the interior of the building 2 when rainwater enters the inside of the pillar 5 from the outside of the building 2 through the interface.

[0022] The pressure plate 6 is joined to the lower part of the foundation member 4. As shown in FIGS. 3 and 5 , the pressure plate 6 extends along a horizontal plane so as to cover the piles 3 and the ground around the foundation member 4. The pressure plate 6 is made of, for example, reinforced concrete and has a concrete portion 61 and pressure plate reinforcing bars 62 embedded in the concrete portion 61. The pressure plate reinforcing bars 62 are arranged, for example, in a lattice pattern when viewed from above. The pressure plate reinforcing bars 62 are provided at the top and bottom of the pressure plate 6 at intervals in the vertical direction H. Part of the pressure plate reinforcing bars 62 protrudes laterally from the pressure plate 6 and is embedded in the concrete portion 41 of the foundation member 4. This firmly joins the pressure plate 6 to the lower part of the foundation member 4.

[0023] Fig. 7 is a horizontal cross-sectional view taken along the line VI-VI in Fig. 3. Fig. 8 is a vertical cross-sectional view taken along the line VII-VII in Fig. 3. The beam 7 (horizontal resistance member) supports the floor of the lowest floor (ground floor) of the building 2. The beam 7 is provided above the pressure plate 6. The beam 7 is joined to the upper part of the foundation member 4. The beam 7 extends horizontally (second direction D2). As shown in Figures 3, 7, and 8, the beam 7 is made of, for example, reinforced concrete, and has a concrete portion 71, a plurality of beam main reinforcements 72, and beam shear reinforcement 73. As shown in Figures 3 and 7, multiple beam main reinforcements 72 are provided at intervals in the upper and lower parts of the beam 7. At each of the upper and lower parts of the beam 7, multiple beam main reinforcements 72 are provided at intervals in the beam width direction (first direction D1) perpendicular to the extension direction of the beam 7 (second direction D2). Each beam main reinforcement 72 extends in the extension direction of the beam 7. The end of each beam main reinforcement 72 protrudes from the concrete portion 71 in the extension direction of the beam 7 and is embedded in the concrete portion 41 of the foundation member 4. The end 72s of each beam main reinforcement 72 extends within the concrete portion 41 in the extension direction of the beam 7 to a position where it overlaps with the core reinforcing bar 8. The end 72s of each beam main reinforcement 72 terminates after being bent upward or downward. A plurality of beam shear reinforcements 73 are provided at intervals in the extension direction of the beam 7. Each beam shear reinforcement 73 is provided in the concrete portion 71 so as to surround a plurality of beam main reinforcements 72.

[0024] 3 and 8, a connecting reinforcement bar 75 is provided at the joint between the beam 7 and the foundation member 4. The connecting reinforcement bar 75 extends in the horizontal direction (second direction D2), with one end embedded in the concrete portion 41 of the foundation member 4 and the other end embedded in the concrete portion 71 of the beam 7. In this embodiment, a plurality of connecting reinforcement bars 75 are provided. The plurality of connecting reinforcement bars 75 are provided in two upper and lower rows in the middle of the beam 7 in the vertical direction H. In each row, the connecting reinforcement bars 75 provided in the two upper and lower rows are arranged at intervals in the beam width direction (first direction D1) perpendicular to the extension direction of the beam 7 in the horizontal plane. The end 75s of the connecting reinforcement bar 75 embedded in the foundation member 4 is bent downward and then terminates. The end 75s of the connecting reinforcement bar 75 extends in the extension direction of the beam 7 to a position beyond the area where the plurality of core reinforcing bars 8 are provided.

[0025] In the above-described configuration, when an earthquake occurs and a bending moment M acts on the pile head 3t of the pile 3, as shown in FIG. 3, a force F due to this bending moment M is transmitted to the pressure plate 6. At the same time, a force -F, i.e., a couple, of the same magnitude as force F, is generated in the beam 7, which is integrally formed with the pressure plate 6 via the column-shaped foundation member 4, at a different position from the bending moment M of the pile head 3t and in the opposite direction. This couple cancels out the bending moment M of the pile head 3t, and as shown in the stress diagram depicted as bending moment M in FIG. 3, the stress in the foundation member 4 decreases upward. In particular, at the height where the beam 7 is joined at the top end of the foundation member 4, the bending moment M is approximately zero. In this manner, in this embodiment, the beam 7 acts as a horizontal resistance member that resists the bending moment M together with the foundation member 4 and the pressure plate 6. Here, in this embodiment, the foundation horizontal reinforcing bars 40H, which are arranged in the horizontal direction D2 and include pressure-resistant plate reinforcing bars 62, main beam reinforcing bars 72, and connecting reinforcing bars 75, and the foundation vertical reinforcing bars 40V, which are arranged in the vertical direction H and include bending reinforcing bars 42 and core reinforcing bars 8, are arranged so that the vertical foundation reinforcing bar capacity, which is the cross-sectional area of ​​the foundation vertical reinforcing bar 40V multiplied by the tensile strength indicating the material properties of the foundation horizontal reinforcing bar 40H, is larger than the horizontal foundation reinforcing bar capacity, which is the cross-sectional area of ​​the foundation horizontal reinforcing bar 40H multiplied by the tensile strength indicating the material properties of the foundation horizontal reinforcing bar 40H. This improves the unity between the pressure plate 6 and the beam 7 by the foundation member 4, and increases the resistance when the bending moment M acts on the pile head 3t of the pile 3 as described above.

[0026] The pile foundation structure 1 as described above is a pile foundation structure 1 including piles 3 that support a building 2 and a pressure plate 6, and is equipped with the piles 3, a column-shaped foundation member 4 that is installed underground and is joined to the pile head 3t of the pile 3 and extends upward from the pile head 3t, a column 5 that is placed on top of the foundation member 4, the pressure plate 6 that is joined to the lower part of the foundation member 4, and a beam (horizontal resistance member) 7 that is joined to the foundation member 4 at a position above the pressure plate 6, and the column base 51 of the column 5 is semi-rigidly joined to the upper surface of the foundation member 4. According to the above-described configuration, a column-shaped foundation member 4, which is installed underground and extends upward from the pile head 3t, is joined to the pile head 3t of the pile 3. A pressure plate 6 is joined to the lower part of this column-shaped foundation member 4, and a beam (horizontal resistance member) 7 is joined to the foundation member 4 above the pressure plate 6. In this way, the pressure plate 6, the beam 7, and the foundation member 4 are formed into a robust, integrated structure with a uniform overall thickness. Because the column 5 is located above such a foundation member 4, even if the column 5 is subjected to a large load, such as a perimeter column of the building 2, the load can be transferred from above to the pressure plate 6 and the ground below the pressure plate. In this way, the axial rigidity of the structure supporting the column 5 is increased, even for columns 5 that are subjected to a large load of the building 2, thereby improving structural safety. Here, the column-shaped foundation member 4 extends upward from the pile head 3t of the pile 3, and therefore the pressure plate 6 joined to the bottom of the foundation member 4 is located near the pile head 3t. The beam 7 is joined to the foundation member 4 at a position above the pressure plate 6, and therefore the beam 7 is joined to the foundation member 4 at a position a certain height above the pile head 3t of the pile 3. In this configuration, when an earthquake occurs and a bending moment M acts on the pile head 3t of the pile 3, this is transmitted to the pressure plate 6. At the same time, a couple acts on the beam 7, which is formed integrally with the pressure plate 6 via the column-shaped foundation member 4, at a different position from the bending moment M of the pile head 3t and in the opposite direction to the bending moment M. This couple cancels out the bending moment M of the pile head 3t, reducing the bending moment M. In this way, the bending moment M of the pile head 3t, which should normally be resisted by the pressure slab 6, is reduced by the foundation member 4 and the beam 7, so there is no need to rely solely on the pressure slab 6 to resist the bending moment M. Therefore, compared to when the foundation member 4 is not provided, it is possible to make the pressure slab 6 thinner, which reduces the amount of basement floor structure and the amount of ground excavation required. Furthermore, the base 51 of the column 5 is semi-rigidly connected to the top surface 45t of the column-shaped foundation member 4. This suppresses the horizontal force transmitted from the foundation member 4 to the base 51 of the column 5 during an earthquake, thereby improving the structural stability of the above-ground portion of the building 2 against earthquakes and vibrations while maintaining a certain degree of flexibility. In particular, since the transmission of bending moment M between the base 51 and the foundation member 4 is suppressed, there is less need to make the foundation member 4 stronger than necessary in order to resist the bending moment M between the base 51 and the foundation member 4. Therefore, when constructing the foundation member 4, the foundation member 4 can be constructed compactly by, for example, reducing the cross-sectional area of ​​the foundation member 4 or reducing the number of shear reinforcement bars. The above effects are combined to provide a pile foundation structure 1 with excellent structural safety that can be easily constructed by reducing the amount of basement floor structure and the amount of ground excavation required.

[0027] In addition, the foundation member 4 is reinforced so that the foundation rebar capacity in the vertical direction H, which is obtained by multiplying the cross-sectional area of ​​the foundation vertical rebar 40V arranged in the vertical direction H by the tensile strength indicating the material properties of the foundation vertical rebar 40V, is greater than the foundation rebar capacity in the horizontal direction D2, which is obtained by multiplying the cross-sectional area of ​​the foundation horizontal rebar 40H arranged in the horizontal direction D2 by the tensile strength indicating the material properties of the foundation horizontal rebar 40H. With this configuration, the foundation steel reinforcement capacity in the vertical direction H is greater than the foundation steel reinforcement capacity in the horizontal direction D2 in the foundation member 4, so by increasing the unity between the pressure plate 6 and the beam (horizontal resistance member) 7 by the foundation member 4, it is possible to increase the resistance to bending moment M when an earthquake occurs and bending moment M acts on the pile head 3t of the pile 3.

[0028] In addition, the pile foundation structure 1 further includes a core reinforcing bar 8 extending in the vertical direction H between the foundation member 4 and the pillar 5, with the upper end 8t buried in the pillar 5 and the lower end 8b buried in the foundation member 4, and the pillar 5 has a tapered lower end to form an inclined surface 56s, and the lower surface 56b of the pillar 5 abuts against the upper surface 45t of the foundation member 4, allowing the pillar 5 to tilt relative to the foundation member 4. According to this configuration, the core reinforcing bars 8 are provided between the column 5 and the foundation member 4, extending in the vertical direction H, and the column 5 is formed so that the lower end of the column 5 is tapered to have an inclined surface 56s, thereby forming the column base 51 of the column 5 in a structure in which it is semi-rigidly joined to the upper surface 45t of the foundation member 4, and the column 5 can be provided so as to be tiltable relative to the foundation member 4. This ensures a certain degree of flexibility between the column 5 and the foundation member 4, while improving the durability and stability of the structure against earthquakes and vibrations.

[0029] Furthermore, the foundation member 4 is provided with bending reinforcement bars 42 in the vertical direction to resist couples that occur between the pressure plate 6 and the beams 7 due to horizontal forces caused by earthquakes. According to this configuration, the resistance force of the foundation member 4 against the couple can be increased, the bending moment M of the pile head 3t can be offset, and the effect of reducing the bending moment M can be enhanced.

[0030] In addition, the pile foundation structure 1 in the above embodiment further includes connecting reinforcement bars 75 extending in the horizontal direction D2 and embedded in each of the foundation members 4 and the beams 7, thereby connecting the foundation members 4 and the beams 7, and the end portions 75s of the connecting reinforcement bars 75 embedded in the foundation members 4 are bent downward and then terminate. This configuration increases the joint strength between the foundation member 4 and the beam 7, and when a bending moment M acts on the pile head 3t of the pile 3 and a couple of forces acts on the beam 7, it becomes possible to effectively resist this.

[0031] In addition, in the pile foundation structure 1 in the above embodiment, the pile 3 is a concrete-filled steel pipe pile, and an anchor bar 35 is joined to the steel pipe 31 of the pile 3 so as to extend upward from the pile head 3t, and the pile head 3t is buried in the foundation member 4 together with the anchor bar 35, thereby joining the pile 3 and the foundation member 4. According to this configuration, the pile head 3t is embedded in the foundation member 4 together with the anchor reinforcement 35, so that the pile 3 and the foundation member 4 are joined together more firmly.

[0032] In the pile foundation structure 1 in the above embodiment, the cross-sectional area of ​​the foundation member 4 is larger than the cross-sectional area of ​​the column base 51 . With this configuration, even if the column 5 is subjected to a large load, such as a perimeter column of the building 2, the load can be transmitted from above downward to the pressure slab 6 and the ground below the pressure slab. This increases the axial rigidity of the structure supporting the column 5, thereby improving structural safety and suppressing ground subsidence and deformation.

[0033] The pressure slab 6 not only supports the vertical load of the basement floor, but also allows a portion of the vertical load of the building 2 to be transmitted from the upper columns 5 to the foundation members 4 and pressure slab 6, as the lower part of the foundation members 4 is rigidly connected to the pressure slab 6. In this way, the vertical load of the building 2 is supported by the piles 3 and pressure slab 6, thereby increasing the structural safety of the building 2.

[0034] (First Modification of the Embodiment) The pile foundation structure of the present invention is not limited to the above-described embodiment explained with reference to the drawings, and various modifications are possible within the technical scope. For example, in the above embodiment, a beam 7 is provided which is joined to the foundation member 4 at a position above the pressure plate 6, but instead of the beam 7, a floor slab may be provided as a horizontal resistance member.

[0035] Such a pile foundation structure 1 is a pile foundation structure 1 including piles 3 supporting a building 2 and a pressure plate 6, and is provided with the piles 3, a column-shaped foundation member 4 installed underground that is joined to the pile head 3t of the pile 3 and extends upward from the pile head 3t, a column 5 placed on top of the foundation member 4, the pressure plate 6 joined to the lower part of the foundation member 4, and a floor slab joined to the foundation member 4 at a position above the pressure plate 6, and the column base 51 of the column 5 is semi-rigidly joined to the upper surface of the foundation member 4. In such a case, it goes without saying that the same effects as those of the above embodiment can be achieved. In particular, in such cases, it is desirable to realize the floor slab as a beam-type portion that is embedded, and to configure this beam-type portion as a beam 7 as described in the above embodiment, with one end joined to the foundation member 4.

[0036] (Second Modification of the Embodiment) In addition, in the above embodiment, the column base 51 of the column 5 is configured to be semi-rigidly joined to the upper surface of the foundation member 4, but this is not limited to this. The column base 51 of the column 5 may be formed to have a smaller cross-sectional area than the foundation member 4, and the column 5 and the foundation member 4 may both be configured to be rigidly joined.

[0037] Such a pile foundation structure 1 is a pile foundation structure 1 including piles 3 supporting a building 2 and a pressure plate 6, and is provided with the piles 3, a column-shaped foundation member 4 installed underground that is joined to the pile head 3t of the pile 3 and extends upward from the pile head 3t, a column 5 placed on top of the foundation member 4, the pressure plate 6 joined to the lower part of the foundation member 4, and a floor slab joined to the foundation member 4 at a position above the pressure plate 6, and the column base 51 of the column 5 has a smaller cross-sectional area than the foundation member 4, and both are rigidly joined. In this configuration, the cross-sectional area of ​​the base 51 of the column 5 is smaller than the cross-sectional area of ​​the column-shaped foundation member 4, and the base 51 is rigidly connected to the foundation member 4. This reduces the horizontal force transmitted from the foundation member 4 to the base 51 of the column 5 during an earthquake, thereby improving the structural stability of the above-ground building 2 against earthquakes and vibrations while maintaining a certain degree of flexibility. In particular, since the transmission of bending moment M between the base 51 and the foundation member 4 is suppressed, there is less need to make the foundation member 4 stronger than necessary in order to resist the bending moment M between the base 51 and the foundation member 4. Therefore, when constructing the foundation member 4, the foundation member 4 can be constructed compactly by, for example, reducing the cross-sectional area of ​​the foundation member 4 or reducing the number of shear reinforcement bars.

[0038] (Other variations) Furthermore, in the above embodiment, the pillar 5 is configured such that the dimension of the pillar base 51 in the pillar width direction gradually decreases from top to bottom by inclining the other 51t of the side surfaces 51s and 51t in the pillar width direction, but this is not limited to this, and the pillar 5 may have any cross-sectional shape. In the above embodiment, the dimension of the column base 51 in the column width direction gradually decreases from top to bottom in all columns 5 located on the periphery of the building 2, but this is not limited to this. Of the multiple columns 5 located on the periphery of the building 2, the dimension of the column base 51 in the column width direction may be gradually decreased from top to bottom in some columns 5. In addition, the configurations given in the above embodiments can be selected or changed as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0039] 1 Pile foundation structure 8b lower end 2 Building 8t top 3 Pile 40H Foundation horizontal rebar 3t pile head 40V foundation vertical rebar 4 Foundation member 45t Top surface of foundation member 5 Column 51 Column base 6 Pressure plate 56b Underside of column 7 Beam (horizontal resistance member) 56s Slanted surface 8 Core Reinforcement Bar

Claims

1. A pile foundation structure that includes piles and pressure plates that support a building. The pile and the pressure plate; a horizontal resistance member disposed above the pressure plate; A foundation member that is joined to the pile head of the pile and joins the pressure plate and the horizontal resistance member in the vertical direction; a pillar disposed on an upper portion of the foundation member; Equipped with A pile foundation structure characterized in that the column and the foundation member are joined by a core reinforcing bar extending in the vertical direction between the foundation member and the column.

2. The column and the foundation member are semi-rigidly connected via the core reinforcing bar. The pile foundation structure according to claim 1 .

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