Design method of foundation structure, and foundation structure

Abstract

To provide a design method of a foundation structure in which a pile head is embedded in a pile cap, which can avoid over-dense reinforcement while also being able to handle larger bending moments than in conventional methods, and a foundation structure.SOLUTION: A design method of a foundation structure in which a pile cap is configured to include an embedded portion surrounding a pile head, comprises: calculating bending strength at an upper end surface of the pile head as a pile head joint surface allowable bending moment; calculating bending strength of the embedded portion flush with the upper end surface of the pile head as an embedded portion allowable bending moment; calculating the sum of the pile head joint surface allowable bending moment and the embedded portion allowable bending moment as a pile head joint allowable bending moment; and determining specifications of the pile cap so that, when a predetermined horizontal force acts on the pile cap in a state where a predetermined axial force acts on the pile head, bending moment generated at the center of the upper end surface of the pile head is less than the pile head joint allowable bending moment.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a design method for a foundation structure and the foundation structure. [Background technology]

[0002] Patent Document 1 discloses a pile head reinforcement unit applied to a pile head joint structure (foundation structure) in which the pile head is embedded in the footing. The pile head reinforcement unit is formed by pre-assembling ring reinforcement surrounding the pile head, a square mouthpiece, stirrups connecting the ring reinforcement and the mouthpiece, and footing reinforcement protruding upward. The pile head reinforcement unit is said to be able to reinforce the periphery of the pile head with pile head reinforcement while eliminating the need for on-site work to reinforce the pile head in the footing.

[0003] The pile cap reinforcement unit in Patent Document 1 is intended to reinforce the lower part of the footing (pile cap). Generally, base reinforcement is placed on the top of the pile cap. The base reinforcement corresponds to the reinforcement in Figures 3(a) and (b) of Patent Document 1, and is placed in a grid pattern along the horizontal plane near the top of the pile head. In addition to the base reinforcement, pile cap anchorage reinforcement, main reinforcement of the beam, or main reinforcement of the column may also be placed on the top of the pile cap, as needed.

[0004] On the other hand, in conventional design methods for pile head joint structures, as disclosed in Patent Document 2, for example, the specifications of the pile head joint structure are determined so that when a predetermined axial force acts on the pile head and a predetermined horizontal force acts on the pile cap, the bending moment generated at the center of the upper end face of the pile head is less than a predetermined allowable bending moment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-273161 [Patent Document 2] Japanese Patent Application Publication No. 2018-31204 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional pile head joint structure design methods, including the one disclosed in Patent Document 2, are designed to primarily distribute the generated bending moment on the top surface of the pile head and the pile head anchorage reinforcement (e.g., Mechanism I in Patent Document 2). Therefore, the increase in the bending moment expected during an earthquake is primarily addressed by increasing the bending strength of the pile head and the number and diameter of the pile head anchorage reinforcement. However, there are technical and cost limitations to addressing this issue with conventional pile head joint structure design methods. In particular, as mentioned above, since a large number of various rebars are placed at the top and bottom of the pile cap, the top of the pile cap is prone to over-dense reinforcement, and it is therefore desirable to avoid increasing the number and diameter of the pile head anchorage reinforcement as much as possible.

[0007] In view of the above circumstances, an object of the present invention is to provide a design method for a foundation structure in which the pile head is embedded in a pile cap, which can avoid over-dense reinforcement while also being able to handle larger bending moments than conventional methods, and a foundation structure manufactured using this design method. [Means for solving the problem]

[0008] (1) A method for designing a foundation structure according to at least one embodiment of the present invention includes: a pile cap surrounding the pile head of the pile, In a design method for a foundation structure, the pile cap is made of concrete and a plurality of reinforcing bars, and is configured to include a main body portion located above the pile head and an embedded portion surrounding the pile head, The bending strength at the top end surface of the pile head is calculated as the allowable bending moment at the pile head joint surface, The bending strength of the embedded portion when flush with the top end surface of the pile head is calculated as the allowable bending moment of the embedded portion, The sum of the pile head joint surface allowable bending moment and the embedded portion allowable bending moment is calculated as the pile head joint allowable bending moment, The specifications of the pile cap are determined so that when a predetermined horizontal force acts on the pile cap while a predetermined axial force acts on the pile head, the bending moment generated at the center of the upper end face of the pile head is equal to or less than the allowable bending moment of the pile head joint. A method for designing a foundation structure.

[0009] According to the above configuration (1), by adding the allowable bending moment of the embedded portion to the allowable bending moment at the pile head joint surface, it is possible to increase the allowable bending moment at the pile head joint without increasing the bending strength of the pile head or the number and diameter of the pile head anchorage rebars, making it possible to accommodate larger generated bending moments. Alternatively, according to the above configuration (1), by adding the allowable bending moment of the embedded portion, it is possible to reduce the allowable bending moment at the pile head joint surface while maintaining the allowable bending moment at the pile head joint. This makes it possible to reduce the bending strength of the pile head, or to reduce the number and diameter of the pile head anchorage rebars and avoid over-dense reinforcement. Note that pile head anchorage rebars are not required, and if they are attached to the pile head, the bending strength at the top surface of the pile head is calculated including the pile head anchorage rebars.

[0010] (2) In some embodiments, in the above configuration (1), a compression region where a compression force is generated, a tension region where a tension force is generated, and a shear region where a shear force is generated in the embedded portion when the generated bending moment is generated; The specifications of the pile cap are determined so that the compressive strength of the compression portion is greater than or equal to the compressive force, the tensile strength of the tension portion is greater than or equal to the tensile force, and the shear strength of the shear portion is greater than or equal to the shear force.

[0011] According to the above configuration (2), damage to the embedded part can be prevented when a bending moment is generated, and a predetermined allowable bending moment of the pile head joint can be reliably achieved.

[0012] (3) In some embodiments, in the above configuration (1) or (2), The allowable bending moment of the embedded portion is calculated taking into consideration one or both of the shortest distance from the surface of the pile cap to the plurality of reinforcing bars in the horizontal direction and the eccentricity of the pile relative to the pile cap in the horizontal direction.

[0013] According to the above configuration (3), by calculating the allowable bending moment of the embedded portion by taking into consideration one or both of the shortest distance from the surface of the pile cap to the multiple reinforcing bars in the horizontal direction and the eccentricity of the pile relative to the pile cap in the horizontal direction, it is possible to reliably prevent damage to the embedded portion when a bending moment is generated, and to reliably achieve a specified allowable bending moment of the pile head joint.

[0014] (4) In some embodiments, in the above configuration (1) or (2), The specifications of the pile cap are determined so that the allowable bending moment of the embedded portion is 5% or more of the maximum allowable bending moment of the pile head joint surface.

[0015] According to the above configuration (4), the specifications of the pile cap are determined so that the allowable bending moment of the embedded part is 5% or more of the maximum allowable bending moment of the pile head joint surface, so that it can reliably cope with larger generated bending moments or the amount of reinforcing bars can be reliably reduced.

[0016] (5) In some embodiments, in the above configuration (1) or (2), As at least a part of the plurality of reinforcing bars, a plurality of standing reinforcements having standing portions extending along the vertical direction near the side of the pile head are arranged, The upper ends of the rising portions of the plurality of rising reinforcements are positioned above the pile head.

[0017] According to the above configuration (5), the rising portions of the multiple rising reinforcements can increase the bending strength of the embedded portion that is flush with the upper end surface of the pile head, and the allowable bending moment of the embedded portion can be increased.

[0018] (6) In some embodiments, in the above configuration (5), The foundation structure further includes a beam connected to the pile cap, the beam extends in at least one horizontal direction; In at least one group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction.

[0019] According to the above configuration (6), since the rising portions of the multiple rising reinforcements are arranged in another horizontal direction, the allowable bending moment of the embedded portion when a horizontal force acts on the pile cap in one horizontal direction can be easily and accurately calculated.

[0020] (7) In some embodiments, in the above configuration (5), The foundation structure further includes a beam connected to the pile cap, the beam extends in at least one horizontal direction; In one group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in the one horizontal direction, In another group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction.

[0021] According to the above configuration (7), the rising portions of the multiple rising reinforcements are arranged in one horizontal direction and another horizontal direction, so that the allowable bending moment of the embedded portion when a horizontal force acts on the pile cap in one horizontal direction can be easily and accurately calculated.

[0022] (8) In some embodiments, in the above configuration (5), At least a portion of the plurality of reinforcing bars is not a plurality of base bars arranged in a grid pattern with a pitch of 300 mm or less along the horizontal plane in the vicinity above the pile head.

[0023] According to the above configuration (8), since multiple base reinforcements are not arranged in a grid pattern with a pitch of 300 mm or less, it is possible to avoid overcrowded reinforcement and to facilitate reinforcement work.

[0024] (9) A basic structure according to at least one embodiment of the present invention includes: Stakes and a pile cap surrounding the pile head of the pile, The pile cap is made of concrete and a plurality of reinforcing bars, and the foundation structure includes a main body portion located above the pile head and an embedded portion surrounding the pile head, The bending strength at the upper end surface of the pile head is calculated as the allowable bending moment at the pile head joint surface, The bending strength of the embedded portion at the same plane as the upper end surface of the pile head is calculated as the allowable bending moment of the embedded portion, The sum of the pile head joint surface allowable bending moment and the embedded portion allowable bending moment is calculated as the pile head joint allowable bending moment, The specifications of the pile cap are determined so that when a predetermined horizontal force acts on the pile cap while a predetermined axial force acts on the pile head, the bending moment generated at the center of the upper end face of the pile head is less than the allowable bending moment of the pile head joint.

[0025] According to the above configuration (9), by adding the allowable bending moment of the embedded portion to the allowable bending moment at the pile head joint surface, it is possible to increase the allowable bending moment at the pile head joint without increasing the bending strength of the pile head or the number and diameter of the pile head anchorage rebars, making it possible to accommodate larger generated bending moments. Alternatively, according to the above configuration (9), by adding the allowable bending moment of the embedded portion, it is possible to reduce the allowable bending moment at the pile head joint surface while maintaining the allowable bending moment at the pile head joint. This makes it possible to reduce the bending strength of the pile head, or to reduce the number and diameter of the pile head anchorage rebars and avoid over-dense reinforcement. Note that pile head anchorage rebars are not required, and if they are attached to the pile head, the bending strength at the top surface of the pile head is calculated including the pile head anchorage rebars.

[0026] (10) In some embodiments, in the above configuration (9), A tensile region where a tensile force is generated and a shear region where a shear force is generated are respectively set in the embedded portion in a state where the generated bending moment is generated, The specifications of the pile cap are determined so that the tensile strength of the tension portion is equal to or greater than the tensile force, and the shear strength of the shear portion is equal to or greater than the shear force.

[0027] According to the above configuration (10), damage to the embedded part when a bending moment is generated can be prevented, and a predetermined allowable bending moment of the pile head joint can be reliably achieved.

[0028] (11) In some embodiments, in the above configuration (9) or (10), The allowable bending moment of the embedded portion is calculated by taking into consideration one or both of the shortest distance from the surface of the pile cap to the plurality of reinforcing bars in the horizontal direction and the eccentricity of the pile relative to the pile cap in the horizontal direction.

[0029] According to the above configuration (11), by calculating the allowable bending moment of the embedded portion by taking into consideration one or both of the shortest distance from the surface of the pile cap to the multiple reinforcing bars in the horizontal direction and the eccentricity of the pile relative to the pile cap in the horizontal direction, it is possible to reliably prevent damage to the embedded portion when a bending moment is generated, and to reliably achieve a specified allowable bending moment of the pile head joint.

[0030] (12) In some embodiments, in the above configuration (9) or (10), The specifications of the pile cap are determined so that the allowable bending moment of the embedded portion is 5% or more of the maximum allowable bending moment of the pile head joint surface.

[0031] According to the above configuration (12), the specifications of the pile cap are determined so that the allowable bending moment of the embedded part is 5% or more of the maximum allowable bending moment of the pile head joint surface, so that it can reliably cope with larger generated bending moments or the amount of reinforcing bars can be reliably reduced.

[0032] (13) In some embodiments, in the above configuration (9) or (10), As at least a part of the plurality of reinforcing bars, a plurality of standing reinforcements having standing portions extending along the vertical direction near the side of the pile head are arranged, The upper ends of the rising portions of the plurality of rising reinforcements are positioned above the pile head.

[0033] According to the above configuration (13), the rising portions of the multiple rising reinforcements can increase the bending strength of the embedded portion that is flush with the upper end surface of the pile head, and the allowable bending moment of the embedded portion can be increased.

[0034] (14) In some embodiments, in the above configuration (13), Further provided is a beam connected to the pile cap, the beam extends in at least one horizontal direction; In at least one group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction.

[0035] According to the above configuration (14), the rising portions of the multiple rising reinforcements are arranged in one horizontal direction and another horizontal direction, so that the allowable bending moment of the embedded portion when a horizontal force acts on the pile cap in one horizontal direction can be easily and accurately calculated.

[0036] (15) In some embodiments, in the above configuration (13), Further provided is a beam connected to the pile cap, the beam extends in at least one horizontal direction; In one group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in the one horizontal direction, In another group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction.

[0037] According to the above configuration (15), the rising portions of the multiple rising reinforcements are arranged in one horizontal direction and another horizontal direction, so that the allowable bending moment of the embedded portion when a horizontal force acts on the pile cap in one horizontal direction can be easily and accurately calculated.

[0038] (16) In some embodiments, in the above configuration (13), At least some of the plurality of reinforcing bars do not include a plurality of base bars arranged in a grid pattern at a pitch of 300 mm or less along a horizontal plane in the vicinity above the pile head.

[0039] According to the above configuration (16), since it does not include a plurality of base reinforcements arranged in a grid pattern at a pitch of 300 mm or less, it is possible to avoid overcrowded reinforcement arrangement and to facilitate reinforcement arrangement work. [Effects of the Invention]

[0040] According to the present invention, there is provided a design method for a foundation structure in which the pile head is embedded in a pile cap, which can avoid over-dense reinforcement while also being able to handle larger bending moments than conventional methods, and a foundation structure manufactured using this design method. [Brief explanation of the drawings]

[0041] [Figure 1] 1A and 1B are schematic diagrams illustrating the external shape and reinforcement of a foundation structure according to at least one embodiment of the present invention, in which (a) is a side view and (b) is a top view. [Figure 2] This is an oblique view showing, out of the multiple reinforcing bars, the pile cap upper bars and outer horizontal bars that are arranged in the main body portion. [Figure 3] FIG. 1 is a perspective view showing a schematic state in which multiple pile cap upper reinforcements and multiple outer transverse reinforcements are assembled. [Figure 4] FIG. 2 is a perspective view schematically showing pile cap lower reinforcement, rising reinforcement, and inner horizontal reinforcement that are placed in the embedded portion among a plurality of reinforcing bars. [Figure 5] FIG. 1 is a perspective view showing a schematic state in which multiple pile cap lower reinforcements and multiple outer transverse reinforcements are assembled. [Figure 6] This is a top view showing the assembled state of multiple rising reinforcements and internal transverse reinforcements, along with the pile head and pile head anchorage reinforcements. [Figure 7] FIG. 2 is a schematic longitudinal cross-sectional view of a foundation structure. [Figure 8] 1 is a flowchart illustrating a general procedure of a method for designing a foundation structure according to at least one embodiment of the present invention. [Figure 9] FIG. 10 is a diagram for explaining the allowable bending moment of the pile head joint. [Figure 10] FIG. 1 is a diagram for explaining a fiber model. [Figure 11] FIG. 1 is a diagram for explaining a fiber model. [Figure 12] FIG. 10 is a diagram for explaining the bending strength of the embedded portion. [Figure 13] FIG. 10 is a diagram for explaining the bending strength of the embedded portion. [Figure 14] FIG. 10 is a diagram for explaining the compressive strength of the embedded portion. [Figure 15] FIG. 10 is a diagram for explaining the compressive strength of the embedded portion. [Figure 16] FIG. 10 is a diagram for explaining the shear strength of an embedded portion. [Figure 17] FIG. 10 is a diagram illustrating the tensile strength of the embedded portion. [Figure 18] FIG. 10 is a diagram illustrating the tensile strength of the embedded portion. [Figure 19] 10A and 10B are diagrams for explaining shear failure and tensile failure of an embedded portion. [Figure 20] 10A and 10B are diagrams for explaining shear failure and tensile failure of an embedded portion. [Figure 21] FIG. 10 is a diagram for explaining a concentrated load on an embedded portion. [Figure 22] FIG. 10 is a diagram for explaining a concentrated load on an embedded portion. [Figure 23] FIG. 10 is a diagram for explaining the allowable bending moment of the pile head joint. [Figure 24] FIG. 10 is a diagram for explaining the upper end position of the rising portion of the rising bar. [Figure 25] FIG. 10 is a schematic diagram illustrating a foundation structure according to another embodiment of the present invention. [Figure 26] 1 is a schematic diagram illustrating a civil engineering and construction structure according to at least one embodiment of the present invention; [Figure 27] 1 is a table for explaining the specifications of the test specimen and the test conditions for the load test. [Figure 28] FIG. 2 is a schematic diagram for explaining a load test device. [Figure 29] 1 is a graph illustrating a loading cycle. [Figure 30] 10 is a graph showing the results of a load test. [Figure 31] 10 is a graph showing the results of a load test. [Figure 32] 10 is a graph showing the results of a load test. [Figure 33] 10 is a graph showing the results of a load test. [Figure 34] 10 is a graph showing the results of a load test. [Figure 35] 10 is a table showing the results of a load test. [Figure 36] 10 is a graph showing the results of a load test. [Figure 37] 10 is a graph showing the results of a load test. [Figure 38] 10 is a graph showing the results of a load test. [Figure 39] This is a diagram for explaining the shortest distance (cover thickness t) from the surface of the pile cap to the outer transverse reinforcement in the horizontal direction. [Figure 40] FIG. 10 is a diagram for explaining bearing strength taking into account the cover thickness t. [Figure 41] This is a diagram to explain the case where the distance from the side of the pile head to the rising part of the rising reinforcement in the horizontal direction is longer than the cover thickness t. [Figure 42] FIG. 10 is a diagram illustrating a case where the pile head is eccentric relative to the pile cap in the horizontal direction. [Figure 43] FIG. 10 is a diagram for explaining bearing strength taking into account cover thickness t and eccentricity e. [Figure 44] FIG. 10 is a diagram illustrating another case where the pile head is eccentric relative to the pile cap in the horizontal direction. DETAILED DESCRIPTION OF THE INVENTION

[0042] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, formulas, numerical values ​​in the formulas, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative or preferred examples. For example, expressions expressing shapes such as a square or a cylindrical shape not only represent shapes such as a square or a cylindrical shape in the strict geometric sense, but also represent shapes including concave and convex portions, chamfered portions, etc., as long as the same effect is obtained. Similarly, expressions for mathematical expressions may be expressed slightly differently as long as the same effect is obtained, and numerical values ​​may have a range within the range in which the same effect is obtained.

[0043] 1A and 1B are schematic diagrams illustrating the external shape and reinforcement of a foundation structure according to at least one embodiment of the present invention, with (a) being a side view and (b) being a top view. The foundation structure in FIG. 1 is a suitable example of a foundation structure manufactured using a foundation structure design method according to at least one embodiment of the present invention, which will be described later.

[0044] As shown in FIG. 1, a foundation structure according to at least one embodiment of the present invention includes a pile 2 and a pile cap 4 surrounding a pile head 2 a of the pile 2 . The pile 2 is a prefabricated pile having a hollow cylindrical shape, such as a steel pipe pile, a concrete pile with a shell steel pipe (hereinafter also referred to as an SC pile), a reinforced concrete pile (hereinafter also referred to as an RC pile), a prestressed concrete pile (hereinafter also referred to as a PC pile), or a prestressed high-strength concrete pile (hereinafter also referred to as a PHC pile). The outer diameter of the pile 2 is, for example, 300 mm or more and 1500 mm or less, and if the pile 2 is a single pile, the length of the pile 2 is, for example, 3 m or more and 15 m or less. If the pile 2 is a joint pile made up of multiple piles connected together, the length of the pile 2 is, for example, 10 m or more and 50 m or less.

[0045] In this embodiment, as a preferred aspect, a plurality of pile head anchoring bars 6 are attached to the pile head 2a. The plurality of pile head anchoring bars 6 are arranged spaced apart from one another in the circumferential direction of the pile head 2a, and each extends vertically upward from the pile head 2a. In this embodiment, the pile head anchoring bars 6 are attached to the outer peripheral surface of the pile head 2a, but they may also be attached to the end face of the pile head 2a.

[0046] The pile cap 4 is made of concrete and multiple reinforcing bars. More specifically, the pile cap 4 has an embedded portion 4a that surrounds the pile head 2a and a main body portion 4b above the embedded portion 4a. The embedded portion 4a contacts the outer peripheral surface and upper end surface of the pile head 2a, and the area of ​​the pile cap 4 that is flush with the tip surface of the pile head 2a is formed by the embedded portion 4a. The external shape of the pile cap 4 is, for example, a rectangular parallelepiped or cubic shape, and the embedded portion 4a and the main body portion 4b each have a rectangular parallelepiped or cubic external shape. The height of the pile head 2a within the embedded portion 4a (hereinafter also referred to as the embedded length h) is, for example, 0.5D to 1.5D, and preferably 0.5D to 1.0D (where D is the outer diameter of the pile 2).

[0047] To provide the embedded portion 4a, the opening of the pile hole is generally enlarged, and the pile head portion 2a is positioned so as to protrude into the enlarged opening. The area of ​​the embedded portion 4a in top view is usually the same as or smaller than that of the main body portion 4b. The diameter d of the embedded portion 4a in top view (the length of the short side or one side when the shape of the embedded portion 4a in top view is rectangular or square, etc.) is, for example, 2.0D or more and 4.0D or less, and preferably 2.5D or more and 3.5D or less.

[0048] The multiple reinforcing bars are each made of, for example, deformed reinforcing bars and are arranged inside the embedded portion 4a and the main body portion 4b. Fig. 2 is a perspective view that schematically shows, of the multiple reinforcing bars, the reinforcing bars (hereinafter also referred to as pile cap upper reinforcements) 8 and the outer cross reinforcements 10 that are arranged in the main body portion 4b. Fig. 3 is a perspective view that schematically shows the state in which the multiple pile cap upper reinforcements 8 and the multiple outer cross reinforcements 10 are assembled. 2, each pile cap upper reinforcement 8 has a U-shape and includes a horizontal portion 8a extending along the upper surface of the main body 4b and hanging portions 8b extending downward from both ends of the horizontal portion 8a and along the side surfaces of the main body 4b. The horizontal portion 8a has a length approximately equal to that of one side of the main body 4b.

[0049] In one group of the multiple pile cap upper reinforcements 8, the pile cap upper reinforcements 8 are spaced apart from each other in one horizontal direction (hereinafter also referred to as the X direction), and each horizontal portion 8a is arranged along another horizontal direction (hereinafter also referred to as the Y direction) perpendicular to the first horizontal direction. In another group of the multiple pile cap upper reinforcements 8, the pile cap upper reinforcements 8 are spaced apart from each other in the Y direction, and each horizontal portion 8a is arranged along the X direction. Therefore, the horizontal portions 8a of the multiple pile cap upper reinforcements 8 are arranged in a lattice pattern near the top surface of the main body 4b so as to cover almost the entire top surface of the main body 4b, and exist throughout almost the entire top surface. Note that "near the top surface" refers to a position approximately the cover thickness away from the top surface.

[0050] The outer horizontal reinforcement 10 has a substantially rectangular shape and four sides 10a extending along the four side surfaces of the pile cap 4. The outer horizontal reinforcement 10 is spaced apart from one another in the vertical direction, and each outer horizontal reinforcement 10 is arranged to surround the pile cap upper reinforcement 8. Each side 10a of each outer horizontal reinforcement 10 is connected to the hanging parts 8b of the multiple pile cap upper reinforcement 8. Each external cross reinforcement 10 only needs to extend in the horizontal plane adjacent to the hanging parts 8b of the multiple pile cap upper reinforcements 8, and may be arranged inside the pile cap upper reinforcements 8 so as to be surrounded by the pile cap upper reinforcements 8. Also, in Figure 2, the external cross reinforcement 10 is of a welded closed type (endless shape), but it may also be formed by bending wire material into a substantially rectangular shape, or by combining L-shaped or U-shaped reinforcing bars.

[0051] Fig. 4 is a perspective view that schematically shows, among the multiple reinforcing bars, reinforcing bars (hereinafter also referred to as pile cap lower reinforcing bars) 12, rising reinforcing bars 14, and inner transverse reinforcing bars 16 that are arranged in the embedded portion 4a. Note that multiple outer transverse reinforcing bars 10 are also arranged in the embedded portion 4a. Fig. 5 is a perspective view that schematically shows the state in which the multiple pile cap lower reinforcing bars 12 and multiple outer transverse reinforcing bars 10 are assembled. Fig. 6 is a top view that schematically shows the state in which the multiple rising reinforcing bars 14 and inner transverse reinforcing bars 16 are assembled together with the pile head portion 2a.

[0052] As shown in Figure 4, the pile cap lower reinforcement 12 has a U-shape and includes a horizontal portion 12a that extends along the underside of the embedded portion 4a, and upright portions 12b that extend upward from both ends of the horizontal portion 12a and along the side of the embedded portion 4a. The horizontal portion 12a of the pile cap lower reinforcement 12 has a length approximately equal to that of one side of the embedded portion 4a.

[0053] Similar to the pile cap upper reinforcement 8, the pile cap lower reinforcement 12 is arranged so that its horizontal portion 12a extends along the X or Y direction. However, since the pile head portion 2a is present inside the embedded portion 4a, the pile cap lower reinforcement 12 is arranged so as to avoid the pile head portion 2a in the center of the embedded portion 4a. Therefore, the horizontal portions 12a of the pile cap lower reinforcement 12 are arranged in a grid pattern near the underside of the embedded portion 4a in the four corner areas of the underside of the embedded portion 4a, and in a blind pattern in the areas between the four corners. On the other hand, the rising portion 12b of the pile cap lower reinforcement 12 extends to the main body portion 4b, and the upper end of the rising portion 12b is overlapped with the lower end of the hanging portion 8b of the pile cap upper reinforcement 8. As a result, one corresponding pile cap upper reinforcement 8 and one corresponding pile cap lower reinforcement 12 form a rectangular or square shape as a whole that is parallel to a plane including the X direction and the vertical direction or a plane including the Y direction and the vertical direction.

[0054] 4, each of the upright reinforcements 14 has a U-shape and includes a horizontal portion 14a extending horizontally and upright portions 14b, 14c extending upward from both ends of the horizontal portion 14a. In this embodiment, the length of the upright portions 14b, 14c is the same as the length of the upright portion 12b of the pile cap lower reinforcement 12. The rising reinforcements 14 are arranged in the area where the pile cap lower reinforcements 12 are spaced apart by avoiding the pile head 2a. In other words, the rising reinforcements 14 are arranged in the area where the horizontal portions 12a of the pile cap lower reinforcements 12 are arranged in a blind-like pattern. The horizontal portions 14a of the rising reinforcements 14 are arranged perpendicular to the horizontal portions 12a of the pile cap lower reinforcements 12. As a result, as shown in Figure 6, the multiple rising reinforcements 14 are arranged in four groups around the pile head 2a. In each group, the rising portions 14a, 14b of the multiple rising reinforcements 14 are aligned and spaced apart from each other in the X or Y direction.

[0055] In top view, of the rising portions 14b, 14c of each rising reinforcement 14, the rising portion 14b on the inner side (pile head 2a side) in the X or Y direction is arranged along a rectangle surrounding the pile head 2a. The pitch (center-to-center distance) of the rising portions 14b, 14c in each of the X and Y directions is, for example, 50 mm to 300 mm, and preferably 100 mm to 200 mm. Each rising portion 14b extends vertically near the side of the pile head 2a, extending along the four side surfaces of a rectangular parallelepiped or cube coaxially surrounding the pile head 2a. Note that "near the side" means that the nearest position is approximately 1.5 times the maximum dimension of the coarse aggregate, preferably approximately the cover thickness.

[0056] On the other hand, of the rising portions 14b, 14c of each rising reinforcing bar 14, the outer rising portion 14c is arranged in a row with the rising portion 12b of the pile cap lower reinforcing bar 12 in a top view. A plurality of outer horizontal reinforcing bars 10 are arranged spaced apart from each other in the vertical direction so as to surround the rising portion 12b of the pile cap lower reinforcing bar 12 and the rising portion 14b of the rising reinforcing bar 14, and the side portions 10a of each outer horizontal reinforcing bar 10 are connected to the rising portions 12b, 14c. Note that the upper end of the outer rising portion 14c is overlapped with the hanging portion 8b of the corresponding pile cap upper reinforcing bar 8, just like the rising portion 12b of the pile cap lower reinforcing bar 12. As a result, one corresponding pile cap upper reinforcing bar 8 and one corresponding rising reinforcing bar 14 form an inverted concave shape as a whole that is parallel to a plane including the X direction and the vertical direction or a plane including the Y direction and the vertical direction. However, among the sides of the inverted concave shape, the side facing the upper end surface of the pile head 2a is missing.

[0057] The multiple internal transverse reinforcing bars 16 are each approximately rectangular and are spaced apart from one another in the vertical direction. Each internal transverse reinforcing bar 16 has four horizontally extending sides 16a. Each of the four sides 16a also extends horizontally. Each internal transverse reinforcing bar 16 surrounds the rising portions 14b of the multiple rising reinforcing bars 14, and the sides 16a of the internal transverse reinforcing bars 16 are connected to the rising portions 14b of the rising reinforcing bars 14. Each inner transverse reinforcement 16 only needs to extend in a horizontal plane adjacent to the rising portions 14b of the multiple rising reinforcements 14, and may be arranged inside the rising reinforcements 14 so as to be surrounded by the rising reinforcements 14. Also, in Figures 4 and 6, the inner transverse reinforcement 16 is of a welded closed type (endless shape), but it may also be formed by bending a wire rod into a substantially rectangular shape, or by combining L-shaped or U-shaped reinforcing bars.

[0058] Figure 7 is a schematic vertical cross-sectional view of the foundation structure of this embodiment. As shown in Figure 7, the horizontal portion 14a of the rising reinforcement 14 is positioned above the underside of the embedded portion 4a by approximately the cover thickness, and the rising portion 14b extends upward from near the underside of the embedded portion 4a. In this embodiment, the upper ends of the rising portions 14b of the rising reinforcement 14 arranged around the pile head 2a are located within the main body 4b of the pile cap 4, but it is sufficient that they are located at least above the pile head 2a. In this embodiment, the multiple reinforcing bars arranged within the pile cap 4 do not include multiple base reinforcement bars arranged in a grid pattern with a pitch (center-to-center distance of the reinforcing bars) of 300 mm or less along the horizontal plane above the pile head 2a, or if they do, the pitch is greater than 300 mm. The "near the top of the pile head 2a" refers to a position above the pile head 2a by approximately the cover thickness. Note that the pile head anchorage bars 6 are not shown in Figure 7.

[0059] Fig. 8 is a flowchart showing the outline of the steps of a design method for a foundation structure according to one embodiment of the present invention. The design method for a foundation structure shown in Fig. 8 (hereinafter simply referred to as the design method) is applicable to the manufacture of the foundation structures of the above-mentioned embodiments, and includes a specification selection step S1, a pile head joint surface allowable bending moment calculation step S2, an embedded portion allowable bending moment calculation step S4, a pile head joint portion allowable bending moment calculation step S6, and a specification determination step S8.

[0060] In the specification selection process S1, the specifications of the foundation structure are set. In the first specification selection process S1, the initial specifications of the foundation structure are empirically selected and set, for example, based on the specifications of the superstructure, ground information, and past cases. Then, in the specification setting process S1 from the second time onwards, the specifications of the foundation structure are selected and set while taking into account the specifications of the previous foundation structure so that the specification determination process S8, which will be described later, can be passed. Note that in the specification selection process S1, not only the specifications of the pile cap 4 but also the specifications of the pile head 2a and the pile head anchorage reinforcement 6 are selected and set. The specifications of the pile cap 4 include, for example, the dimensions and shape of the pile cap 4, the embedment length h, the concrete strength, and the arrangement, outer diameter, material, number, and length of the reinforcing bars. The specifications of the pile head 2a include, for example, the outer diameter, axial compressive strength, radial compressive strength, and radial shear strength. In the case of a hollow precast concrete pile, the specifications include the outer diameter, inner diameter, concrete strength, and the arrangement, outer diameter, material, number, and length of the reinforcing bars. The specifications of the pile head anchoring reinforcement 6 include, for example, the arrangement of the reinforcing bars, the outer diameter, the material, the number and length of the bars, etc. In the pile head joint surface allowable bending moment calculation process S2, the bending strength at the upper end surface of the pile head 2a is calculated as the pile head joint surface allowable bending moment for the foundation structure whose specifications have been selected and set in the specification selection process S1.

[0061] In the embedded portion allowable bending moment calculation step S4, the bending strength of the embedded portion 4a when it is flush with the upper end face of the pile head 2a is calculated as the embedded portion allowable bending moment. In the pile head joint allowable bending moment calculation step S6, the sum of the pile head joint surface allowable bending moment Mα and the embedded portion allowable bending moment Mβ′ is calculated as the pile head joint allowable bending moment. In the specification determination step S8, when a predetermined axial force is applied to the pile head 2a and a predetermined horizontal force is applied to the pile cap 4, it is determined whether the bending moment M generated at the center of the upper end face of the pile head 2a is equal to or less than the allowable bending moment of the pile head joint. If the determination result is positive, the specifications of the foundation structure selected and set in the specification selection step S1 are determined as the final specifications of the foundation structure. On the other hand, if the determination result is negative, the process returns to the specification selection step S1.

[0062] According to the design method configured as above, by adding the allowable bending moment at the embedded portion to the allowable bending moment at the pile head joint surface, it is possible to increase the allowable bending moment at the pile head joint without increasing the bending strength of the pile head 2a or the number and diameter of the pile head anchorage rebars 6, and it is possible to accommodate larger generated bending moments. Alternatively, according to the configuration configured as above, by adding the allowable bending moment at the embedded portion, it is possible to reduce the allowable bending moment at the pile head joint surface while maintaining the allowable bending moment at the pile head joint. This makes it possible to reduce the bending strength of the pile head 2a, or to reduce the number and diameter of the pile head anchorage rebars 6 and avoid over-dense reinforcement. Avoiding over-dense reinforcement makes it easier to arrange the reinforcement in the pile cap 4, improving the constructability of the foundation structure. In addition, the pile head anchorage reinforcement 6 is not required, and if the pile head anchorage reinforcement 6 is attached to the pile head 2a, the bending strength at the upper end surface of the pile head 2a is calculated including the pile head anchorage reinforcement 6.

[0063] Figure 9 is a diagram for explaining the allowable bending moment of the pile head joint in the design method of the above configuration. In accordance with the loading test described later, the horizontal force Q acting on the pile cap 4 is assumed to act on the pile 2 at a position a distance L away from the underside of the embedded part 4a.

[0064] In the design method configured as described above, when a horizontal force Q acts on the pile cap 4 while a predetermined axial force is acting on the pile head 2a, the bending moment (generated bending moment) M that occurs on the pile cap 4 is expressed as the sum of the bending moment M1 at the pile head joint surface (the upper end surface of the pile head 2a) and the bending moment M2 at the embedded portion 2a, as shown in Figure 9 and the following equations 1 to 10. The horizontal force Q acting on the pile cap 4 is expressed as the sum of the horizontal force Qh acting on the pile head joint surface and the horizontal force Qt acting on the embedded portion 4a.

[0065] In the design method of the above configuration, the bending moment M2 at the embedded portion 4a is converted into a bending moment M2' flush with the upper end surface of the pile head portion 2a as shown in Equation 9, and the bending moment M is expressed as the sum of bending moment M1 and bending moment M2' as shown in Equation 10. In Figure 9, Mα is the bending strength (allowable bending moment at pile head joint surface) of the top surface (pile head joint surface) of the pile head 2a, and Qα is the sum of the frictional force at the pile head joint surface and the shear strength of the pile head anchorage reinforcement 6. Furthermore, Mβ' is the bending strength (allowable bending moment at embedded portion) of the embedded portion 4a when it is flush with the top surface of the pile head 2a, and Qβ is the shear strength of the embedded portion 4a. As is clear from a comparison of Equation 1 and Equation 6, the allowable bending moment at embedded portion Mβ' does not include the effect of the axial force N from the superstructure.

[0066]

number

[0067]

number

[0068] Below, the allowable bending moment Mα at the pile head joint surface and the allowable bending moment (bending strength) Mβ' at the embedded portion will be described in detail using the foundation structure configured as above as an example. <Allowable bending moment at pile head joint> The allowable bending moment at the pile head joint surface can be calculated using a known fiber model. As shown in Figures 10 and 11, the fiber model assumes that the cross section of the pile head 2a remains flat (the strain distribution is linear), and that the conversion from strain to stress follows the stress-strain curve of each material.The strain distribution in the cross section is then changed from full tension to full compression, and the force generated in the infinitesimal cross section Ai at each strain distribution is found.The axial force Nα at the top surface of the pile head 2a and the allowable bending moment Mα at the pile head joint surface can then be obtained using the following equations 11 and 12, respectively.

[0069]

number

[0070] <Ultimate bending strength of the entire embedded section (reinforcement bars arranged in the direction of the applied force) (Mu1)> The ultimate bending strength Mu1 of the pile cap lower reinforcement 12 and the rising reinforcement 14 arranged in the embedded portion 4, with the horizontal portions 12a, 14a arranged along the load application direction, can be calculated using Figure 12 and Equation 13. In Equation 13, fv is the tensile strength of the rising portions 14b, 14c of the rising reinforcement 14, and fm is the tensile strength of the rising portion 12b of the pile cap lower reinforcement 12. Also, av1 is the cross-sectional area of ​​the rising portion 14b of the rising reinforcement 14 located on the positive side of the load application direction, in a region flush with the tip surface of the pile head 2a; av2 and av3 are the cross-sectional areas of the rising portions 14b, 14c of the rising reinforcement 14 located on the negative side of the load application direction, respectively, in a region flush with the tip surface of the pile head 2a; and am is the cross-sectional area of ​​the rising portion 12b of the pile cap lower reinforcement 12 located on the negative side of the load application direction, in a region flush with the tip surface of the pile head 2a. The cross-sectional areas av1 to av3 and avm in Equation 13 are the total cross-sectional areas of the rising portions 14b, 14c, and 12b in the regions surrounded by the dashed lines in FIG.

[0071] Furthermore, dm is the effective distance of the embedded part 4a of the pile cap 4 in the force application direction, and dv1, dv2, and dv3 are the distance from the side of the embedded part 4a on the positive side of the force application direction to the rising part 14b of the rising reinforcement 14 located on the positive side of the force application direction, and the distance to the rising parts 14b and 14c of the rising reinforcement 14 located on the negative side of the force application direction, respectively. As shown in Equation 13, the ultimate bending strength Mu1 can be considered to include the contribution Mv1 of the rising portion 14b of the rising reinforcement 14 located on the positive side of the force application direction, the contributions Mv2 and Mv3 of the rising portions 14b and 14c of the rising reinforcement 14 located on the negative side of the force application direction, and the contribution Mm of the rising portion 12b of the pile cap lower reinforcement 12 located on the negative side of the force application direction, and three cases can be considered as combinations of these contributions Mv1, Mv2, Mv3, and Mm. Since the contribution Mv1 of the rising reinforcement 14 on the positive side of the force application direction is estimated to be small, Case 2 will be selected in this explanation.

[0072]

number

[0073] <Ultimate bending strength of the entire embedded section (reinforcing bars arranged perpendicular to the applied force) (Mu2)> The ultimate bending strength Mu2 of the pile cap lower reinforcement 12 and the rising reinforcement 14 arranged in the embedded portion 4, whose horizontal portions 12a, 14a are arranged perpendicular to the load application direction, can be calculated using Figure 13 and formula 14. In formula 14, fv is the tensile strength of the rising portions 14b, 14c of the rising reinforcement 14, and fm is the tensile strength of the rising portion 12b of the pile cap lower reinforcement 12. Also, av1 to avn are the cross-sectional areas of the rising portions 14b, 14c of the rising reinforcement 14, respectively, in the region flush with the tip surface of the pile head 2a, and am1 to amm are the cross-sectional areas of the rising portion 12b of the pile cap lower reinforcement 12, respectively, located on the negative side of the load application direction, in the region flush with the tip surface of the pile head 2a. The cross-sectional areas av1 to avn and am1 to amm in Equation 14 are the total cross-sectional areas of the raised portions 14b, 14c, and 12b in each region (each row) surrounded by the dashed dotted line in FIG. Furthermore, dm is the effective distance of the embedded part 4a of the pile cap 4 in the force application direction, dv1 to dvn are respectively the distance from the side of the embedded part 4a on the positive side of the force application direction to the rising part 14b of the rising reinforcement 14, and dm1 to dmm are respectively the distance from the side of the embedded part 4a on the positive side of the force application direction to the rising part 12b of the pile cap lower reinforcement 12 on the negative side of the force application direction. As shown in Equation 14, the ultimate bending strength Mu2 can be considered to include the contribution (Mv) of the rising portion 14b of the rising reinforcement 14 located on the positive side of the force application direction and the contribution (Mm) of the rising portion 12b of the pile cap lower reinforcement 12 located on the negative side of the force application direction, and three cases can be considered as combinations of these contributions Mv and Mm. Since the contribution Mv of the rising reinforcement 14 is estimated to be small, Case 1 will be selected in this explanation.

[0074] <Ultimate bending strength of the entire embedded section (Mu)> The ultimate bending strength Mu of the entire embedded portion is expressed by the following equation 15. From equation 15, when the bending moment M2' reaches the ultimate bending strength Mu of the entire embedded portion 4a, bending failure occurs in the entire embedded portion 4a. This collapse mode is hereinafter also referred to as collapse mode i.

[0075] [Number]

[0076] In some embodiments, in the design method of the above structure, in the embedded portion 4a in a state where a bending moment is generated, a compression portion where a compressive force is generated, a tension portion where a tensile force is generated, and a shear portion where a shear force is generated are respectively set, and the compressive strength of the compression portion is set to be not less than the compressive force, the tensile strength of the tension portion is set to be not less than the tensile force, and the shear strength of the shear portion is set to be not less than the shear force, and the specifications of the pile cap 4 are determined.

[0077] According to the above structure, it is possible to prevent damage to the embedded portion 4a in a state where a bending moment is generated, and it is possible to reliably realize a predetermined allowable bending moment of the pile head joint portion.

[0078] Hereinafter, the compressive force, shear force, and tensile force generated in the pile cap 4 will be described in detail by taking the basic structure of FIG. 1 as an example. [Direct response strength of the concrete of the embedded part] The direct response strength (horizontal stress on the side surface of the pile) of the embedded portion 4a can be expressed by FIGS. 14, 15, and the following equations (16) to (20). In this case, the stress is assumed to be a triangular distribution with a constant slope, and the effective width is the pile diameter D. The horizontal bearing strength Fb of the concrete can be expressed by Equation (20), and the increase coefficient γ of the bearing strength Fb can be obtained from experimental results. Then, from Equation (16), when the sum of the stress σs and the stress σm reaches the bearing strength Fb, compressive failure of the concrete (the concrete of the embedded portion 4a) occurs at the portion adjacent to the side surface of the pile head 2a on the positive side of the loading direction. Such a failure mode will hereinafter also be referred to as failure mode g.

[0079] [Number]

[0080] [Ultimate shear strength QuA of part A] <00The ultimate shear strength QuA of part A located on the positive side of the loading direction with respect to the pile head 2a in the embedded part 4a of the pile cap 4 can be expressed by Fig. 16 and the following formula 21. In the following, the region located on the negative side of the loading direction is referred to as part B, and the boundary surface between part A and part B is referred to as part T. Therefore, part T extends in a direction orthogonal to the loading direction from the pile head 2a. And, among part A, the fan-shaped region that expands in the direction of ±45 degrees with respect to the loading direction from the pile head 2a is referred to as part A1. In formula 21, AcA is the cross-sectional area of part A1, and Fc is the strength of the concrete. fv and av are the tensile strength and cross-sectional area of the rising parts 14b and 14c of the rising bars 14 in the region flush with the tip surface of the pile head 2a (regions i and ii surrounded by the dashed line in the a-a cross-sectional view of Fig. 16), respectively. fm and am are the tensile strength and cross-sectional area of the rising part 12b of the pile cap bottom bar 12 in the region flush with the tip surface of the pile head 2a (region iii surrounded by the dashed line in the b-b cross-sectional view of Fig. 16), respectively. The cross-sectional area av in formula 21 is the total cross-sectional area of the rising parts 14b and 14c within part A1, and the cross-sectional area am is the total cross-sectional area of the rising part 12b within part A1. In Fig. 16, the wavy line represents the cracks that will occur.

[0081] <Ultimate tensile strength Tu of part T> The ultimate tensile strength Tu of part T located in the direction orthogonal to the loading direction from the pile head 2a in the embedded part 4a of the pile cap 4 can be expressed by Fig. 17, Fig. 18 and the following formula 22. In formula 22, fm and am represent the tensile strength and cross-sectional area of the horizontal part 12a of the pile cap bottom bar 12 in part T surrounded by the dashed line in Fig. 17, respectively, fhi and ahi represent the tensile strength and cross-sectional area of the side part 16a of the inner transverse bar 16 in part T surrounded by the dashed line in Fig. 18, respectively, and fho and aho represent the tensile strength and cross-sectional area of the side part 10a of the outer transverse bar 10 in part T surrounded by the dashed line in Fig. 18, respectively. The cross-sectional areas am, ahi, and aho in formula 22 are the total cross-sectional areas within the respective regions surrounded by the dashed line in Figs. 17 and 18, respectively. In Figs. 17 and 18, the wavy line represents the cracks that will occur.

[0082]

Number

[0083] <Shear failure of part A + Tensile failure of part T> As shown in Fig. 19 and Eqs. 23 and 24, the shear failure of part A and the tensile failure of part T occur when the concentrated load C1 described later reaches the sum of the ultimate shear strength QuA of part A and the ultimate tensile strength Tu of part T. Such a failure mode is also referred to as failure mode bd hereinafter. In Fig. 19, the wavy line represents the cracks that will occur.

[0084]

Number

[0085] <Shear failure of part A + Shear failure of part B + Tensile failure of part T> As shown in Fig. 20 and Eqs. 25 and 26, the shear failure of part A, the shear failure of part B, and the tensile failure of part T occur when the sum of the concentrated load C1 and the concentrated load C2 described later reaches the sum of the ultimate shear strength QuA of part A, the ultimate shear strength QuB of part B, and the ultimate tensile strength Tu of part T. Such a failure mode is also referred to as failure mode bed hereinafter. In part B, the fan-shaped region that expands in the direction of ±45 degrees with respect to the loading direction from the pile head 2a is referred to as part B1.

[0086]

Number

[0087] Hereinafter, the shear force acting on the pile head 2a will be described in detail taking the basic structure of Fig. 1 as an example. <Conversion to concentrated loads C1, C2> The stress σs and the stress σm can be converted into the concentrated loads C1 and C2 as shown in Figs. 21, 22, and the following Eqs. 27 to 32. From this, it can be seen that a shear force C2 (5 to 10 times) significantly larger than the horizontal force Qt acts on the pile head 2a in the embedded part 4a. Therefore, the specifications of the pile 2 are determined so that the shear force resistance of the pile head 2a is sufficient.

[0088]

number

[0089] Figure 23 is a graph that shows the relationship between the allowable bending moment Mα at the pile head joint surface, the allowable bending moment Mβ' at the embedded part, and the allowable bending moment at the pile head joint. As shown in Figure 23, the allowable bending moment at the pile head joint is expressed as the sum of the allowable bending moment Mα at the pile head joint surface and the allowable bending moment Mβ' at the embedded part. As mentioned above, in the foundation structure of Fig. 1, there are four possible collapse types for the embedded part 4a: collapse type g, collapse type bd, collapse type bed, and collapse type i. Of the ultimate bending strengths M2' calculated from equations 9, 15, 24, and 26 corresponding to these four collapse types, the minimum value is the ultimate bending strength (allowable moment of the embedded part) Mβ'. As shown in Fig. 23, the yield strength and short-term strength of the embedded part 4a are each 2 / 3 of the ultimate bending strength Mβ'.

[0090] In some embodiments, in the design method of the above configuration, a plurality of rising reinforcements 14 having rising portions 14b extending in the vertical direction near the sides of the pile head 2a are arranged as at least a portion of the plurality of reinforcing bars, and the upper ends of the rising portions 14b of the plurality of rising reinforcements 14 are arranged above the pile head 2a. According to the above configuration, the rising portions 14b of the multiple rising reinforcements 14 can increase the bending strength of the embedded portion 4a flush with the upper end surface of the pile head 2a, and can increase the allowable bending moment Mβ' of the embedded portion.

[0091] FIG. 24 is a diagram for explaining the upper end position of the rising portion 14b of the rising bar 14. In some embodiments, as shown in FIG. 8, when the vertical distance between the upper ends of the rising portions 14b of the plurality of rising reinforcements 14 and the pile head portion 2a is L2, the following equation is satisfied: L1≦L2 When L1 = L2, the upper end of the rising portion 14b of the rising reinforcement 14 is located at an angle of 45 degrees above the upper edge of the pile head 2a.

[0092] According to the above configuration, since the distance L2 is longer than the distance L1, cracks propagating diagonally upward at 45 degrees from the upper edge of the pile head 2a can be suppressed by the rising portion 14b of the rising reinforcement 14. As a result, according to the above configuration, the allowable bending moment Mβ' of the embedded portion can be reliably increased.

[0093] In some embodiments, in the design method of the above configuration, as shown in FIG. 1, the foundation structure further includes a beam 18 connected to the pile cap 4, and as shown in FIG. 24, the upper ends of the rising portions 14b of the multiple rising reinforcements 14 are located higher than the lower ends of the beam 18. The beam 18 extends along the X direction, but may also extend along the Y direction. Note that in FIG. 1, the upper surface of the pile cap 4 and the upper surface of the beam 18 are flush with each other. However, if the height of the beam 18 is high, the upper surface of the beam 18 may be located higher than the upper surface of the pile cap 4. Conversely, if the height of the beam 18 is low, the upper surface of the beam 18 may be located lower than the upper surface of the pile cap 4. In other words, the upper surfaces of the pile cap 4 and the beam 18 may not be flush with each other. According to the above configuration, the upper ends of the rising portions 14b of the plurality of rising bars 14 are positioned above the lower surface of the beam 18, so that the embedded portion allowable bending moment Mβ' can be reliably increased.

[0094] In some embodiments, in the design method of the above configuration, the foundation structure further includes beams 18 connected to the pile caps 4, the beams 18 extending in at least one horizontal direction (X direction), and in at least one group of the multiple rising reinforcements 14, the rising portions 14b of the multiple rising reinforcements 14 are aligned and spaced apart from each other in another horizontal direction (Y direction) perpendicular to the one horizontal direction.

[0095] According to the above configuration, the rising portions 14b of the multiple rising reinforcements 14 are arranged in another horizontal direction (Y direction), so that the allowable bending moment of the embedded portion when a horizontal force acts on the pile cap 4 in one horizontal direction (X direction) can be easily and accurately calculated.

[0096] In some embodiments, in the design method of the above configuration, the foundation structure further includes beams 18 connected to the pile caps 4, and the beams 18 extend in at least one horizontal direction (X direction), and in one group of the plurality of rising reinforcements 14, the rising portions 14b of the plurality of rising reinforcements 14 are aligned and spaced apart from each other in the one horizontal direction (X direction), and in another group of the plurality of rising reinforcements 14, the rising portions 14b of the plurality of rising reinforcements 14 are aligned and spaced apart from each other in another horizontal direction (Y direction) perpendicular to the one horizontal direction (X direction).

[0097] According to the above configuration, the rising portions 14b of the multiple rising reinforcements 14 are arranged in one horizontal direction and another horizontal direction, so that the allowable bending moment of the embedded portion when a horizontal force acts on the pile cap 4 in one horizontal direction can be easily and accurately calculated.

[0098] In some embodiments, in the design method of the above configuration, as shown in Fig. 1, the beam 18 is made of concrete and a plurality of beam main reinforcements, and the plurality of beam main reinforcements include a plurality of beam bottom reinforcements 20 each extending horizontally in the lower part of the beam 18 and a plurality of beam top reinforcements 21 each extending horizontally in the upper part of the beam 18. Then, as shown in Fig. 24, the upper ends of the rising portions 14b of the plurality of rising reinforcements 14 are located above the beam bottom reinforcements 20. According to the above configuration, the upper ends of the rising portions 14b of the plurality of rising reinforcements 14 are positioned above the beam bottom end reinforcements 20, so that the embedded portion allowable bending moment Mβ' can be reliably increased.

[0099] In some embodiments, in the design method for the above configuration, the upper ends of the rising portions 14b of the plurality of rising reinforcements 14 are located above a position equivalent to ½ of the height of the beam 18. According to the above configuration, the upper ends of the rising portions 14b of the multiple rising reinforcements 14 are located above a point corresponding to 1 / 2 of the height of the beam 18, so that the rising portions 14b can reliably improve the allowable bending moment of the embedded portion. Furthermore, with the above configuration, when a compressive force is generated in the lower half of the beam depth, a compression strut is formed and the rising reinforcement 14 is firmly fixed.

[0100] Preferably, the upper ends of the rising portions 14b of the plurality of rising reinforcements 14 are located above a position corresponding to 2 / 3 or even 3 / 4 of the height of the beam 18. From the viewpoint of avoiding over-dense reinforcement arrangement, it is preferable that the rising portions 14b of the multiple rising reinforcements 14 are as short as possible within the range in which the desired allowable bending moment of the pile head joint can be obtained, and for example, as shown in Figure 24, it is preferable that the upper ends of the rising portions 14b of the multiple rising reinforcements 14 are located below the upper beam reinforcement 21 that constitutes the beam 18, or at a position equivalent to 1 / 2 or less of the beam depth. Therefore, for example, it is preferable that the upper ends of the rising portions 14b of the multiple rising reinforcements 14 are located at a position that is a distance L1 or more above the upper end of the pile head 2a and equivalent to 1 / 2 or less of the beam depth.

[0101] In some embodiments, in the design method of the above configuration, at least a portion of the multiple reinforcing bars are not arranged in a grid pattern with a pitch of 300 mm or less along a horizontal plane near the top of the pile head 2a. According to the above configuration, multiple base reinforcements are not arranged in a grid pattern with a pitch of 300 mm or less, so that overcrowded reinforcement can be avoided and reinforcement work can be made easier. In addition, when the multiple reinforcing bars include multiple base bars arranged in a lattice pattern with a pitch of more than 300 mm, the multiple base bars extend, for example, in the X direction and the Y direction.

[0102] In some embodiments, in the design method configured as described above, the embedment depth h of the pile head 2a into the pile cap 4, the concrete strength, and the quantity and arrangement of reinforcing bars of the multiple rising reinforcements 14 are determined so that the embedded portion allowable bending moment Mβ' is 5% or more, preferably 10% or more, and more preferably 20% or more of the maximum value of the pile head joint surface allowable bending moment Mα at the top end surface of the pile head 2a (hereinafter also referred to as the pile head joint surface maximum allowable bending moment Mmax). Note that the quantity of reinforcing bars refers to the name (diameter and cross-sectional area), material (steel type and composition), and number (including pitch) of the reinforcing bars. Furthermore, when determining the quantity and arrangement of reinforcing bars of the rising reinforcements 14, the quantity and arrangement of reinforcing bars of the rising reinforcements 14 are preferably determined.

[0103] According to the above configuration, by determining the embedding depth h of the pile head 2a into the pile cap 4, the concrete strength, and the amount and arrangement of reinforcing bars of the multiple rising reinforcements 14 so that the embedded portion allowable bending moment Mβ' is 5% or more of the maximum allowable bending moment Mmax at the pile head joint surface, it is possible to reliably cope with larger generated bending moments or to reliably reduce the amount of reinforcing bars.

[0104] In some embodiments, in the design method of the above configuration, as shown in Figures 6 and 7, the multiple reinforcing bars include one or more internal cross bars 16 extending in a horizontal plane adjacent to the rising portions 14b of the multiple rising bars 14. According to the above configuration, since the multiple reinforcing bars include the inner horizontal bars 16, the tensile strength of the tension portion of the pile cap 4 can be reliably increased.

[0105] Preferably, the plurality of reinforcing bars include two or more, more preferably five or more, and even more preferably eleven or more inner transverse bars 16 spaced apart in the vertical direction. Preferably, the uppermost inner transverse bar 16 is at the same height as the upper end of the pile head 2a, or, when the vertical distance between the inner transverse bar 16 and the pile head 2a is L3, the following formula is satisfied: L1≦L3 When L1 = L3, the inner horizontal reinforcement 16 is positioned diagonally upward at 45 degrees from the upper edge of the pile head 2a.

[0106] 7 and 24, in some embodiments, the upper ends of the rising portions 14c of the rising reinforcements 14 near the outer periphery of the pile cap 4 are located higher than the lower beam reinforcement 20, preferably at a height of at least half the beam depth, but lower than the upper beam reinforcement 21, and the upper portions of the rising portions 14c of the rising reinforcements 14 are connected with the hanging portions 8b of the pile cap upper reinforcement 8 by lap joints above the lower beam reinforcement 20. Therefore, preferably, the rising reinforcements 14 have a J-shape as a whole.

[0107] Conventionally, the rising portion of the base reinforcement is connected to the brace reinforcement (the hanging portion of the pile cap upper reinforcement) with a lap joint near the bottom end reinforcement of the beam, and the rising portion of the rising reinforcement also enters here, resulting in an overcrowded state. In contrast, with the above configuration, the upper part of the rising portion 14c of the rising reinforcement 14 is connected to the hanging portion 8b of the pile cap upper reinforcement 8 with a lap joint above the bottom end reinforcement of the beam 20, thereby avoiding overcrowded reinforcement arrangement. The vicinity of the outer periphery of the pile cap 4 refers to a position approximately the covering thickness from the side of the pile cap 4.

[0108] FIG. 25 is a schematic diagram for explaining a basic structure according to another embodiment of the present invention. As shown in Figure 25, the concrete that makes up the pile cap 4 includes a cast-in-place section 22 that is cast directly around the pile head 2a and a precast section 24 that is cast at a location separate from the pile head 2a, and some of the multiple rising reinforcements 14 are embedded in the precast section 24. In other words, the multiple rising reinforcements 14 and the precast section 22 may be integrally formed to form a precast product for foundation structure.

[0109] According to the above configuration, the concrete precast section 24 that constitutes the pile cap 4 is cast in advance, and some of the plurality of rising reinforcements 14 are embedded in the precast section 24. Therefore, once the worker installs the precast section 24 around the pile head 2a, there is no need for the worker to individually arrange the plurality of rising reinforcements 14 around the pile head 2a. Therefore, according to the above configuration, the workability of the pile cap 4 is further improved. In addition, the precast section 24 may be provided with connecting members for connecting the reinforcing bars of the beams and the reinforcing bars of the columns, as well as sheaths for passing these through, as necessary.

[0110] Figure 26 is a schematic diagram illustrating a civil engineering and architectural structure according to at least one embodiment of the present invention. The civil engineering and architectural structure includes a column 26 connected to a pile cap 4. For example, the column 26 is a concrete column composed of concrete and column main reinforcement 28, but it may also be made of steel. Furthermore, the lower part of the column main reinforcement 28 extending into the pile cap 4 may be straight or bent in an L-shape.

[0111] According to the above configuration, the allowable bending moment of the pile head joint of the foundation structure is sufficiently secured or improved, so that the column 26 is stably supported by the foundation structure, and the safety of the entire civil engineering and architectural structure is ensured. Meanwhile, since the workability of the foundation structure is improved, the workability of the entire civil engineering and architectural structure is also improved.

[0112] <Load test> Below, the results of the load test will be described as an example. Fig. 27 is a table explaining the specifications of the specimen and the test conditions for the load test, Fig. 28 is a schematic diagram explaining the load test device, Fig. 29 is a graph explaining the loading cycle, and Figs. 30 to 38 are graphs or tables showing the results of the load test.

[0113] More specifically, for specimens A-1, A-2, A-3, A-4, B-1, B-2, and C-1, the pile heads 2a are not embedded in the pile cap 4, and the base reinforcement and pile cap upper reinforcement 8 are arranged in a square shape parallel to a plane including the X and vertical directions or a plane including the Y and vertical directions, respectively, above the top surface of the pile head 2a, and are arranged in multiple rows in the Y and X directions, respectively, to form a box shape overall. In other words, in these specimens, multiple base reinforcement bars are provided in a grid pattern near the top of the pile head 2a. For the other specimens, as shown in Figures 1 to 7, the pile heads 2a are embedded in the pile cap 4, and the rising portions 14b of the rising reinforcement 14 are arranged along the four side surfaces of a rectangular parallelepiped or cube coaxial with the pile head 2a. In this case, multiple pile cap upper reinforcements 8 and rising reinforcements 14 are arranged in an inverted concave shape parallel to a plane including the X direction and the vertical direction or a plane including the Y direction and the vertical direction, and are arranged at intervals in the Y direction or the X direction.

[0114] Figures 30 to 33 show the relationship between the calculated embedded strength values ​​(positive and negative loading directions) obtained using equations 15, 19, 24, and 26, which correspond to the collapse modes i, g, bd, and bed, respectively, and the load test results. Note that the test values ​​for each material are substituted for the material properties in the calculated values. The scales of the vertical and horizontal axes are standardized, and the 45-degree line in the graph indicates when the calculated value and the load test result are equal. Therefore, if the plot is above the line in the graph, it indicates that the experimental value exceeds the calculated value.

[0115] Figure 34 shows the relationship between the minimum value of the embedded part strength calculated using Equations 15, 19, 24, and 26 and the results of the loading test. Figure 35 shows the collapse patterns actually observed in the specimens after the loading test.

[0116] Figure 36 shows the relationship between the calculated values ​​of pile head joint surface strength obtained using Equations 11 and 12 and the load test results. Note that the test values ​​of each material are substituted for the material properties in the calculated values. The scales of the vertical and horizontal axes are standardized, and the 45-degree line in the graph indicates when the calculated value and the load test result are equal. Therefore, if the plot is above the line in the graph, it indicates that the experimental value exceeds the calculated value.

[0117] Figure 37 shows the relationship between the sum of the calculated embedded section strength and the calculated pile head joint surface strength (i.e., the calculated pile head joint strength) and the load test results. Figure 38 is a graph used to compare the results when calculating the test values ​​as material property values ​​with the results when standard values ​​(nominal values) are used instead of the test values. be.

[0118] 34 and 35 show that there is a high correlation between the calculated embedded part strength and the load test results, confirming the validity of Equations 15, 19, 24, and 26. Furthermore, Figure 36 shows that there is a high correlation between the calculated pile head joint surface strength and the load test results, confirming the validity of the fiber model (Equations 11 and 12). Furthermore, Figure 37 shows that there is a high correlation between the calculated value of the pile head joint strength and the test results of the load test, confirming the validity of calculating the pile head joint strength by adding the embedded part strength to the pile head joint surface strength. Furthermore, Figure 38 shows that using test values ​​rather than standard values ​​as the material properties will result in more accurate calculation values ​​for yield strength.

[0119] Finally, the present invention is not limited to the above-described embodiments, but includes modifications to the above-described embodiments and combinations thereof. For example, in the above-described embodiment, the pile head 2a and the pile cap 4 were rigidly connected, but if necessary, the adhesion force between the concrete and the rising portion 14a of the rising reinforcement 14 can be reduced to form a semi-rigid connection or a pin connection. In addition, an anchoring member may be attached to the upper end of the rising portion 14b of the rising reinforcing bar 14 in order to increase the adhesion between the concrete and the rising portion 14b of the rising reinforcing bar 14 or to shorten the rising portion 14b of the rising reinforcing bar 14.

[0120] Furthermore, although the rising reinforcement 14 is made up of one U-shaped reinforcing bar, the rising reinforcement may be made up of two L-shaped reinforcing bars bound together. Furthermore, in addition to adopting the above-described embodiment, the number of base reinforcements arranged in a grid pattern may be reduced compared to conventional methods to alleviate overcrowded reinforcement arrangement. In other words, the above-described foundation structure may include grid-like base reinforcements as long as the pitch is greater than 300 mm.

[0121] Furthermore, in general, the reinforcing bars in the pile cap 4, for example, the outer horizontal bars 10, are covered with concrete to a predetermined cover depth t (the shortest distance from the surface of the reinforcing bars to the surface of the pile cap 4 in the horizontal direction), as shown in Figure 39. In the above-mentioned embodiment, the bearing strength Fb was calculated using equation (20), but it may also be calculated using the following equation (33), which takes the cover depth t into consideration. The cover depth t is, for example, 60 mm or more and 80 mm or less. In this way, by calculating the allowable bending moment of the embedded part by taking into account the shortest distance from the surface of the pile cap 4 to the multiple reinforcing bars in the horizontal direction, it is possible to reliably prevent damage to the embedded part 4a when a bending moment is occurring, and to reliably achieve the specified allowable bending moment of the pile head joint.

[0122]

number

[0123] Furthermore, in the above-described embodiment, the distance from the rising portion 14b of the rising reinforcement 14 in the horizontal direction to the outer peripheral surface of the pile head 2a was short, at the shortest, approximately 1.5 times the maximum dimension of the coarse aggregate, and preferably approximately the cover thickness. However, as shown in Figure 41, the distance from the rising portion 14b of the rising reinforcement 14 in the horizontal direction to the outer peripheral surface of the pile head 2a may be longer, for example, to 100 mm or more.

[0124] In this way, if the distance from the rising portion 14b of the rising reinforcement 14 to the outer peripheral surface of the pile head 2a is increased, the pile head 2a may become eccentric, for example, in the X direction, as shown in Figure 42. If the amount of eccentricity in this case is e, the bearing strength Fb may be calculated using the following equation (34), which takes into account the amount of eccentricity e in addition to the cover thickness t. In this way, by calculating the allowable bending moment of the embedded part taking into account the eccentricity e and the cover thickness t, it is possible to reliably prevent damage to the embedded part 4a when a bending moment is generated, and to reliably achieve the specified allowable bending moment of the pile head joint. As shown in equation (35), the bearing strength Fb may be calculated by taking into account only the eccentricity e.

[0125] Furthermore, cases in which the pile head 2a is eccentric relative to the pile cap 4 in the horizontal direction include when the distance from the pile head 2a to the rising portion 14b of the rising reinforcement 14 is long, as shown in Figure 42, and also when the length of the horizontal portion 14a of the rising reinforcement 14 is different on both sides of the pile head 2a, as shown in Figure 44. In the case of Figure 44, the eccentricity of the pile head 2a was planned from the design stage, but in the case of Figure 42, the eccentricity of the pile head 2a was not planned at the design stage, but it is possible that the pile head 2a became eccentric during construction.

[0126]

number

[0127] 2 stakes 2a Pile head 4. Pile Cap 4a Embedded part 4b Main body 6 Pile head anchorage 8 Pile cap upper reinforcement 8a Horizontal section 8b Hanging part 10 Transverse muscle 10a Edge 12 Pile cap underbar 12a Horizontal section 12b Rising section 14 Erector muscles 14a Horizontal section 14b, 14c Rising section 16 Transverse muscle 16a Edge 18 Beam 20 Beam bottom reinforcement 21 Beam top reinforcement 22 Cast-in-place section 24 Precast Section 26 pillars 28 Column main reinforcement Mα Allowable bending moment at pile head joint Mβ' Allowable bending moment of embedded part

Claims

1. Stakes and a pile cap surrounding the pile head of the pile, In a design method for a foundation structure, the pile cap is made of concrete and a plurality of reinforcing bars, and is configured to include a main body portion located above the pile head and an embedded portion surrounding the pile head, The bending strength at the top end surface of the pile head is calculated as the allowable bending moment at the pile head joint surface, The bending strength of the embedded portion at the same plane as the upper end surface of the pile head is calculated as the allowable bending moment of the embedded portion, The sum of the pile head joint surface allowable bending moment and the embedded portion allowable bending moment is calculated as the pile head joint allowable bending moment, The specifications of the pile cap are determined so that when a predetermined horizontal force acts on the pile cap while a predetermined axial force acts on the pile head, the bending moment generated at the center of the upper end face of the pile head is equal to or less than the allowable bending moment of the pile head joint. A method for designing a foundation structure.

2. Identifying a compression region where a compression force occurs, a tension region where a tensile force occurs, and a shear region where a shear force occurs in the embedded portion when the generated bending moment is generated; The specifications of the pile cap are determined so that the compressive strength of the compression portion is equal to or greater than the compressive force, the tensile strength of the tension portion is equal to or greater than the tensile force, and the shear strength of the shear portion is equal to or greater than the shear force.

2. The method for designing a foundation structure according to claim 1.

3. The allowable bending moment of the embedded portion is calculated by taking into consideration one or both of the shortest distance from the surface of the pile cap to the plurality of reinforcing bars in the horizontal direction and the eccentricity of the pile with respect to the pile cap in the horizontal direction.

3. The method for designing a foundation structure according to claim 1 or 2.

4. The specifications of the pile cap are determined so that the allowable bending moment of the embedded part is 5% or more of the maximum allowable bending moment of the pile head joint surface.

3. The method for designing a foundation structure according to claim 1 or 2.

5. As at least a part of the plurality of reinforcing bars, a plurality of standing reinforcements having standing portions extending along the vertical direction near the side of the pile head are arranged, The upper ends of the rising portions of the plurality of rising reinforcements are arranged above the pile head.

3. The method for designing a foundation structure according to claim 1 or 2.

6. The foundation structure further includes a beam connected to the pile cap, the beam extends in at least one horizontal direction; In at least one group of the plurality of rising reinforcements, the rising portions of the plurality of rising reinforcements are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction. The method for designing a foundation structure according to claim 5.

7. The foundation structure further includes a beam connected to the pile cap, the beam extends in at least one horizontal direction; In one group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in the one horizontal direction, In another group of the plurality of rising reinforcements, the rising portions of the plurality of rising reinforcements are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction. The method for designing a foundation structure according to claim 5.

8. As at least a part of the plurality of reinforcing bars, a plurality of base bars arranged in a grid pattern with a pitch of 300 mm or less along the horizontal plane in the vicinity above the pile head are not arranged. The method for designing a foundation structure according to claim 5.

9. Stakes and a pile cap surrounding the pile head of the pile, The pile cap is made of concrete and a plurality of reinforcing bars, and the foundation structure includes a main body portion located above the pile head and an embedded portion surrounding the pile head, The bending strength at the upper end surface of the pile head is calculated as the allowable bending moment at the pile head joint surface, The bending strength of the embedded portion at the same plane as the upper end surface of the pile head is calculated as the allowable bending moment of the embedded portion, The sum of the pile head joint surface allowable bending moment and the embedded portion allowable bending moment is calculated as the pile head joint allowable bending moment, The specifications of the pile cap are determined so that when a predetermined horizontal force acts on the pile cap while a predetermined axial force acts on the pile head, the bending moment generated at the center of the upper end face of the pile head is equal to or less than the allowable bending moment of the pile head joint. A foundation structure characterized by:

10. Identifying a compression region where a compression force occurs, a tension region where a tensile force occurs, and a shear region where a shear force occurs in the embedded portion when the generated bending moment is generated; The specifications of the pile cap are determined so that the compressive strength of the compression portion is equal to or greater than the compressive force, the tensile strength of the tension portion is equal to or greater than the tensile force, and the shear strength of the shear portion is equal to or greater than the shear force.

10. The base structure of claim 9.

11. The allowable bending moment of the embedded portion is calculated taking into consideration one or both of the shortest distance from the surface of the pile cap to the plurality of reinforcing bars in the horizontal direction and the eccentricity of the pile with respect to the pile cap in the horizontal direction.

11. The base structure according to claim 9 or 10.

12. The specifications of the pile cap are determined so that the allowable bending moment of the embedded portion is 5% or more of the maximum allowable bending moment of the pile head joint surface.

11. The base structure according to claim 9 or 10.

13. As at least a part of the plurality of reinforcing bars, a plurality of standing reinforcements having standing portions extending along the vertical direction near the side of the pile head are arranged, The upper ends of the rising portions of the plurality of rising reinforcements are arranged above the pile head.

11. The base structure according to claim 9 or 10.

14. The foundation structure further includes a beam connected to the pile cap, the beam extends in at least one horizontal direction; In at least one group of the plurality of rising reinforcements, the rising portions of the plurality of rising reinforcements are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction.

14. The base structure of claim 13.

15. Further provided is a beam connected to the pile cap, the beam extends in at least one horizontal direction; In one group of the plurality of rising streaks, the rising portions of the plurality of rising streaks are aligned and spaced apart from one another in the one horizontal direction, In another group of the plurality of rising reinforcements, the rising portions of the plurality of rising reinforcements are aligned and spaced apart from one another in another horizontal direction perpendicular to the one horizontal direction.

14. The base structure of claim 13.

16. At least a portion of the plurality of reinforcing bars does not include a plurality of base bars arranged in a grid pattern with a pitch of 300 mm or less along the horizontal plane in the vicinity above the pile head.

14. The base structure of claim 13.

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