Pile design method

Abstract

The objective is to provide a pile design method that allows for a reduction in the diameter and number of piles. [Solution] A method for designing piles in a building having an underground portion, characterized in that the effect of embedding the underground portion into the ground is evaluated by considering the SMW wall, which is constructed by the SMW method and integrated with the main structure of the building, as a resistance element in addition to the main structure of the building, and then setting the diameter and number of piles.

Description

Technical Field

[0001] The present invention relates to a method for designing piles in a building having a basement part.

Background Art

[0002] For example, as a building such as an office building, there is known a structure having a basement part and supported by piles provided in the ground in the basement part (see, for example, Patent Document 1).

[0003] Conventionally, when designing piles in such a building having a basement part, only the basement part of the building is evaluated as a resistance element, and the spring and bearing capacity in the effect of anchoring the basement part of the building to the ground are calculated, and the diameter and number of piles are set using the calculation result. This was generally the case.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a building having a basement part, there is known a building in which an SMW wall is constructed as a retaining wall by the SMW method, the ground inside the SMW wall is excavated, and then the basement part of the building is constructed in the excavated part.

[0006] Even in a building constructed using the SMW method, only the basement part of the building is evaluated as a resistance element to set the diameter and number of piles, but in this building, it is required to reduce the load on the piles and reduce the diameter and number of piles. There was room for improvement in the pile design method in this regard.

[0007] This invention was made in view of the above-mentioned problems, and its purpose is to provide a pile design method that can reduce the diameter and number of piles. [Means for solving the problem]

[0008] The present invention relates to a pile design method for a building having an underground portion, characterized in that the effect of embedding the underground portion into the ground is evaluated by considering the SMW wall, which is constructed by the SMW method and integrated with the main structure portion of the building, as a resistive element, in addition to the main structure portion of the building, and the diameter and number of the piles are set accordingly. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a pile design method that makes it possible to reduce the diameter and number of piles. [Brief explanation of the drawing]

[0010] [Figure 1] This is a front view cross-sectional view of a building having piles designed by a pile design method according to one embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view of the building from the side. [Figure 3] This is a cross-sectional view along line AA in Figure 1. [Figure 4] This is a magnified cross-sectional view showing the portion of the building shown in Figure 1 where the SMW wall is installed. [Figure 5] This is a cross-sectional view along line BB in Figure 4. [Figure 6] This flowchart shows an example of a procedure for designing a pile according to one embodiment of the present invention. [Modes for carrying out the invention]

[0011] The following describes in detail, with reference to the drawings, a design method for piles according to one embodiment of the present invention.

[0012] The present invention relates to a method for designing piles in a building having an underground portion, characterized in that the effect of embedding the underground portion into the ground is evaluated by considering the SMW wall, which is constructed using the SMW method and integrated with the main structure of the building, as a resistance element, in addition to the main structure of the building, and the diameter and number of piles are set accordingly.

[0013] Building 1 shown in Figures 1 to 5 is an example of a building having piles 10 to which the pile design method according to this embodiment is applied.

[0014] This building 1 can be used, for example, as an office building, and has an above-ground section 2 and an underground section 3. Note that the internal structure of building 1 is omitted in Figures 1-5.

[0015] The above-ground portion 2 is the part of building 1 constructed above the ground level 4. The structure and number of floors of the above-ground portion 2 are not particularly limited.

[0016] The underground section 3 is the part of the building 1 constructed inside the ground 4, i.e., underground. The underground section 3 has a reinforced concrete main frame section 3a, which is the main body of the building 1, and SMW walls 8, which will be described later. The main frame section 3a may be the basement floor of the building 1, or it may be just the foundation section without a basement floor. The number of floors of the main frame section 3a is not particularly limited.

[0017] The underground section 3 was constructed using the SMW method.

[0018] As shown in Figures 4 and 5, in the SMW method, before constructing the main structural frame 3a of building 1, the ground 4 is excavated to sequentially form multiple holes 5 that partially overlap each other. H-shaped steel frames 6 are then erected into each of these holes 5, and soil 7 mixed with cement slurry is filled in to construct an SMW wall 8 as a retaining wall, which surrounds the underground portion 3 and whose lower end is positioned below the lower end of the main structural frame 3a of building 1. Next, the ground 4 inside the SMW wall 8 is excavated, and the main structural frame 3a of building 1 is constructed in the excavated area.

[0019] The SMW wall 8 is integrated with the main body structure part 3a of the building 1. More specifically, the soil 7 is flattened at the part facing the side of the main body structure part 3a of the SMW wall 8, and one flange 6a of the steel frame 6 of the H-shaped steel is exposed from the soil 7. A plurality of studs 9 are fixed by welding to the outer surface of each flange 6a exposed from the soil 7. The outer wall 3b of the main body structure part 3a of the building 1 is formed so as to contact the flattened soil 7 and the outer surface of the flange 6a exposed from the soil 7, and the plurality of studs 9 are respectively embedded in the reinforced concrete forming the main body structure part 3a. Thereby, the SMW wall 8 is joined to the outer wall 3b of the main body structure part 3a of the building 1 so that the horizontal forces are transmitted to each other.

[0020] The pile 10 is constructed inside the ground 4, that is, underground, below the main body structure part 3a of the building 1. The pile 10 is joined to the bottom wall 3c of the main body structure part 3a at the pile head so that the horizontal forces are transmitted to each other.

[0021] Next, based on FIG. 6, an example of the procedure for designing the pile 10 by the pile design method according to the present embodiment will be described when planning the construction or building of the building 1 having such a configuration.

[0022] First, in step S1, consideration is given to the vertical force of the pile 10. That is, the vertical force applied to the pile 10 from the above-ground part 2 and the main body structure part 3a of the building 1 is calculated, and consideration is given to the pile 10 with respect to the vertical force.

[0023] Next, consideration is given to the horizontal force of the pile 10. In this consideration, first, in step S2, the horizontal force at the pile head position is calculated from the horizontal force of the above-ground part 2 of the building 1 and the inertial force of the underground part 3. That is, the horizontal force at the pile head position applied to the building 1 during an earthquake or the like is calculated.

[0024] Next, in step S3, the SMW wall 8 is evaluated as a resistance element in addition to the main structural frame 3a, and the spring and bearing capacity due to the embedment effect of the underground portion 3 of the building 1 into the ground 4 is calculated. That is, not only the main structural frame 3a, but also the SMW wall 8 which is integrally joined to the main structural frame 3a is evaluated as a resistance element to the horizontal force applied to the building 1, and the spring and bearing capacity due to the embedment effect of the underground portion 3 of the building 1 into the ground 4 is calculated. The main structural frame 3a and the SMW wall 8 integrally joined to the main structural frame 3a generate resistance to horizontal forces due to frontal passive earth pressure, lateral friction, bottom friction, etc.

[0025] Next, in step S4, the horizontal shear force borne by the pile 10 is calculated from the ratio of the stiffness of the resistance element and the spring stiffness of the pile 10. Specifically, in step S3, the spring stiffness due to the embedment effect of the underground portion 3 of the building 1 into the ground 4 was calculated by evaluating the SMW wall 8 as a resistance element, and from the ratio of the spring stiffness of the pile 10, the horizontal shear force borne by the pile 10 is calculated from the horizontal shear force generated at the pile head position calculated in step S1.

[0026] Next, in step S5, the diameter and number of piles 10 are determined based on the horizontal shear force borne by the piles 10 calculated in step S4.

[0027] Here, the SMW wall 8, which surrounds the entire perimeter of the main structural frame 3a, is integrally installed with the main structural frame 3a and is deeply embedded below the main structural frame 3a. Therefore, the area of ​​resistance to horizontal forces of the underground portion 3 of the building 1 is larger than when the SMW wall 8 is not integrally installed with the main structural frame 3a. Furthermore, the SMW wall 8 resists horizontal forces as friction of the surface material by contacting the ground 4 on its outer surface, and each steel frame 6 can resist horizontal forces as a pile material (steel pile). Therefore, the area of ​​resistance to horizontal forces of the underground portion 3 of the building 1 is larger from these viewpoints compared to when the SMW wall 8 is not integrally installed with the main structural frame 3a. Thus, in the underground section 3, where the SMW wall 8 is integrally provided with the main structural frame 3a, the SMW wall 8 bears a greater horizontal force than in the case where the SMW wall 8 is not integrally provided with the main structural frame 3a. As a result, the horizontal force borne by the piles 10 is relatively reduced. Therefore, the diameter and number of piles 10 determined in step 5 can be reduced by the amount by which the horizontal force borne is reduced. In other words, in the pile design method according to this embodiment, when designing the piles 10, the steel frame 6 used as the core material of the SMW wall 8 is integrated with the outer wall 3b of the main structural frame 3a of the underground section 3. This allows the SMW wall 8, which is normally treated as a temporary material and not evaluated as part of the structure of the building 1 upon completion of the building 1, to be evaluated as a structural member (steel pile) of the underground section 3, thereby reducing the horizontal force borne by the piles 10.

[0028] Thus, in the pile design method according to this embodiment, the embedment effect of the underground portion 3 of the building 1 into the ground 4 is evaluated not only by the main frame portion 3a of the building 1, but also by the SMW wall 8 constructed by the SMW method and integrated with the main frame portion 3a as a resistance element, and the diameter and number of piles 10 are set accordingly. Therefore, compared to designing the piles 10 without evaluating the SMW wall 8 as a resistance element, the diameter and number of piles 10 can be reduced. In other words, the diameter of the piles 10 can be reduced, or the number of piles 10 can be reduced, or the diameter of the piles 10 can be reduced while reducing the number of piles.

[0029] Furthermore, in the pile design method according to this embodiment, increasing the embedment depth of the SMW wall 8 increases the resistance area of ​​the underground portion 3 of the building 1, thereby increasing the proportion of horizontal force borne by it. This reduces the horizontal force borne by the piles 10, and further reduces the diameter and number of piles 10.

[0030] Furthermore, as described above, the pile design method according to this embodiment allows for a reduction in the diameter and number of piles 10, thereby reducing the man-hours and material costs associated with constructing the piles 10, and thus lowering the construction cost of building 1.

[0031] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0032] 1. Building 2 Above ground part 3 Underground part 3a Main body part 3b Exterior wall 3c bottom wall 4 Ground 5 holes 6 Steel frame 6a Flange 7 Soil 8 SMW wall 9 studs 10 stakes

Claims

[Claim 1] A method for designing piles in a building with an underground section, A pile design method characterized by evaluating the effect of embedding the underground portion into the ground by considering the SMW wall, which is constructed using the SMW method and integrated with the main structure of the building, as a resistance element in addition to the main structure of the building, and then setting the diameter and number of the piles.

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