Earthquake-resistant design system for composite soil pile foundations

Abstract

To provide an earthquake-resistant design system for a composite soil pile foundation that can reduce the period required for designing piles and soil improvement bodies when the soil improvement bodies are provided around the piles.SOLUTION: An earthquake-resistant design system 10 for a composite soil pile foundation comprises specification setting means 11 for setting specifications of a soil improvement body and a pile, soil response analysis means 12 that dynamically analyzes a one-dimensional model of only the soil and estimates the soil response, soil displacement estimating means 13 for estimating soil displacement at a position corresponding to the pile by applying the estimated soil response to a finite element model in which only the soil improvement body is provided in the soil and statically analyzing it, pile stress estimating means 14 that estimates the stress of the pile at the time of an earthquake by applying the horizontal force acting on a pile cap and the estimated soil displacement to a beam spring model whose analysis target is the pile, and design verification means 15 to verify whether the estimated pile stress is below a threshold value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a seismic design system for a composite soil pile foundation including piles and soil improvement bodies provided around the piles. [Background technology]

[0002] When constructing a building, it is often supported by piles. In particular, when constructing a building on soft ground, ground improvement bodies that improve the ground may be installed around the piles to ensure the piles' earthquake resistance. For example, Patent Document 1 discloses an earthquake-resistant reinforcement structure for an existing structure foundation, which includes a first solidified improved body constructed by ground improvement in an area extending vertically from a predetermined depth in the ground to the bottom surface of the upper foundation and in a predetermined horizontal range around the existing structure foundation, and a second solidified improved body constructed by ground improvement in an area extending vertically from the bottom surface of the upper foundation to the ground surface and in a predetermined horizontal range around the existing structure foundation. In the earthquake-resistant reinforcement structure of Patent Document 1, the peripheries of the predetermined horizontal ranges of the first solidified improved body and the second solidified improved body are located at least outside the periphery of the upper foundation in a plan view. Patent Document 2 discloses a ground improvement pile having a solidified improved body installed in a borehole oriented perpendicular to the ground and a core material embedded in the solidified improved body. The core material includes a section steel extending along the axis of the solidified improved body, a plurality of first reinforcing bars wrapped around the section steel so as to protrude in one direction intersecting the extension direction of the section steel and welded to parts of the circumferential surface of the section steel at points where they make line contact with the section steel, and a plurality of second reinforcing bars wrapped around the section steel so as to protrude in another direction intersecting the extension direction of the section steel and intersecting the one direction, and welded to at least parts of the circumferential surface of the section steel. The first reinforcing bars and the second reinforcing bars are arranged alternately in the extension direction of the section steel.

[0003] When installing the piles and ground improvement bodies described above, it is necessary to appropriately design the piles and ground improvement bodies. In response to this, Patent Document 3 discloses a configuration for appropriately setting the distance from the center of a pile to the outer edge of a ground improvement body provided around it or to a polygon circumscribing the ground improvement body. However, Patent Document 3 only considers the case where a horizontal force acts on the pile head, and does not consider ground displacement, which is the displacement of the ground itself in the ground where the pile is installed.

[0004] In a configuration with ground improvement bodies around piles, methods for taking ground displacement into account include methods using elastic support beam theory, response displacement methods using beam-spring models, and analysis using two-dimensional or three-dimensional finite element models. The method using elastic bearing beam theory calculates deformation by replacing the ground with uniform elastic bearings and modeling the piles as beams with bending rigidity. However, this method requires that the ground around the piles be considered to be approximately uniform. Therefore, if ground improvement bodies are installed around the piles, they cannot be taken into account. Furthermore, it is not possible to consider ground displacement. In the response displacement method using a beam-spring model, piles are modeled as wire rods and the ground as horizontal springs, and the inertial force from the structure is applied to the pile head, and the horizontal displacement that occurs in the ground is given as a forced displacement via the ground spring. This method can take into account the effects of ground displacement, but when calculating the input ground displacement, the target is basically the horizontally stratified ground, so in cases where ground improvement bodies are installed only partially, for example, on the top of the pile rather than on the entire pile, it is not possible to calculate displacement that takes into account the effects of partial ground improvement, making it difficult to apply.

[0005] In contrast, analysis using 2D or 3D finite element models allows for continuous modeling of the ground, making it possible to evaluate the interaction between elements in a manner that is close to reality. It is also possible to model irregular ground, pile foundations with different pile diameters and lengths, group piles, and heterogeneous foundations, making it suitable for accurately evaluating the interactions between these elements. Therefore, it is possible to calculate pile stress taking into account the ground improvement body. However, in order to consider the effects of ground displacement, earthquake response analysis is usually required. In earthquake response analysis, dynamic analysis is repeated with changes to the specifications of the ground improvement body and piles until the stress in the ground improvement body and piles falls within the allowable values. Because performing such dynamic analysis requires a large amount of calculation, it takes a huge amount of time to complete the calculations before the specifications are finalized. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-177741 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-6264 [Patent Document 3] Japanese Patent Publication No. 2020-51064 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem that the present invention aims to solve is to provide an earthquake-resistant design system for composite ground pile foundations that can reduce the time required to design piles and ground improvement bodies when the ground improvement body is installed around the piles. [Means for solving the problem]

[0008] The inventors have developed an earthquake-resistant design system for composite ground pile foundations, including piles and ground improvement bodies, not by faithfully modeling the ground, piles, and ground improvement bodies as a single unit and performing three-dimensional dynamic FEM analysis, but by first estimating the ground response during an earthquake using dynamic analysis, and then analyzing the pile stress using static analysis using the inertial force and ground displacement (of the ground improvement body) calculated in the dynamic analysis as boundary conditions, thereby shortening the analysis time required to estimate the pile stress and making it possible to design the piles and ground improvement bodies based on the pile stress during an earthquake. In order to solve the above problems, the present invention employs the following means. In other words, the earthquake-resistant design system for composite ground pile foundations of the present invention is an earthquake-resistant design system for composite ground pile foundations including piles and soil improvement bodies provided around the piles, and is characterized by comprising: a specification setting means for setting the specifications of the soil improvement bodies and the piles; a ground response analysis means for performing dynamic analysis on a one-dimensional model of only the ground realized as free ground as the analysis object to estimate the ground response when an earthquake occurs; a ground displacement estimation means for estimating the ground displacement at a position corresponding to the pile when an earthquake occurs by applying the estimated ground response to a two-dimensional or three-dimensional finite element model in which only the soil improvement body is provided in the ground and performing static analysis; a pile stress estimation means for applying the horizontal force acting on the pile head and the estimated ground displacement to a beam-spring model of the pile as the analysis object to estimate the stress of the pile when an earthquake occurs; and a design verification means for comparing the estimated pile stress with a threshold value and verifying whether the stress of the pile is below the threshold value. According to this configuration, a one-dimensional model of only the ground realized as free ground is used as the analysis object, and dynamic analysis is performed to estimate the ground response during an earthquake. This estimated ground response is applied to a two-dimensional or three-dimensional finite element model in which only ground improvement bodies are installed in the ground, and static analysis is performed to estimate ground displacement at the position corresponding to the pile during an earthquake. The horizontal force acting on the pile head and the estimated ground displacement are applied to a beam-spring model in which the pile (a single pile or multiple piles) is the analysis object, and the pile stress during an earthquake is estimated. In this configuration, the ground displacement applied to the beam-spring model when estimating pile stress is estimated by static analysis of the finite element model. This finite element model is configured so that ground improvement bodies are installed in the ground. Therefore, pile stress can be accurately estimated taking into account the influence of ground displacement at the pile position when ground improvement bodies are installed in the ground. Here, the one-dimensional model that is the analysis target in dynamic analysis is realized by the ground only, and does not include the ground improvement body and piles. Therefore, even if the specifications of the ground improvement body and piles change, the dynamic analysis does not need to be performed again. In other words, the motion analysis, which requires a lot of calculation time, only needs to be performed once, using the one-dimensional model of the ground as the analysis target. Therefore, the number of times that dynamic analysis, which requires a lot of calculation time, is performed can be reduced. Furthermore, since the finite element model used for static analysis is configured with only the ground improvement body installed in the ground, if the pile specifications are changed and the pile stress is to be re-estimated, as long as the specifications of the ground improvement body are fixed, there is no need to reconstruct the finite element model and re-run the static analysis using the finite element model. This reduces the number of times static analysis is performed. Furthermore, since the finite element model only includes the ground improvement body, i.e., no piles, the element division of the finite element model can be realized in a rough state without taking piles into consideration, thereby reducing the time required for one analysis. The combined effects of the above will make it possible to reduce the time required to design piles and ground improvement bodies. As a result, it is possible to provide an earthquake-resistant design system for composite ground pile foundations that can reduce the time required to design piles and ground improvement bodies when ground improvement bodies are installed around the piles.

[0009] The earthquake-resistant design system for composite ground pile foundations of the present invention is an earthquake-resistant design system for composite ground pile foundations including piles and soil improvement bodies arranged around the piles, and is characterized by comprising: a specification setting means for setting the specifications of the soil improvement bodies and the piles; a ground displacement estimation means for estimating ground displacement at a position corresponding to the piles when an earthquake occurs by performing dynamic analysis using a two-dimensional or three-dimensional finite element model in which only the soil improvement body is arranged in the ground; a pile stress estimation means for applying the horizontal force acting on the pile head and the estimated ground displacement to a beam-spring model in which the pile is the analysis object, and estimating the stress of the piles when an earthquake occurs; and a design verification means for comparing the estimated pile stress with a threshold value and verifying whether the stress of the piles is below the threshold value. According to this configuration, ground displacement at a position corresponding to a pile during an earthquake is estimated by dynamic analysis using a two-dimensional or three-dimensional finite element model in which only a ground improvement body is installed in the ground. Furthermore, the horizontal force acting on the pile head and the estimated ground displacement are applied to a beam-spring model in which the pile (a single pile or multiple piles) is the analysis object, and the stress in the pile during an earthquake is estimated. In this configuration, the ground displacement applied to the beam-spring model when estimating the pile stress is estimated by dynamic analysis of the finite element model. This finite element model is configured so that a ground improvement body is installed in the ground. Therefore, it is possible to accurately estimate the stress in the pile taking into account the influence of ground displacement at the pile location when a ground improvement body is installed in the ground. In the finite element model used for dynamic analysis, only the ground improvement body is installed in the ground, so if the pile specifications are changed and the pile stress is to be re-estimated, as long as the specifications of the ground improvement body are fixed, there is no need to reconstruct the finite element model and re-run the dynamic analysis using the finite element model. This reduces the number of times dynamic analysis, which requires a very long calculation time, is performed. Furthermore, since the finite element model only includes the ground improvement body, i.e., no piles, the element division of the finite element model can be realized in a rough state without taking piles into consideration, thereby reducing the time required for one analysis. The combined effects of the above will make it possible to reduce the time required to design piles and ground improvement bodies. As a result, it is possible to provide an earthquake-resistant design system for composite ground pile foundations that can reduce the time required to design piles and ground improvement bodies when ground improvement bodies are installed around the piles.

[0010] The earthquake-resistant design system for composite ground pile foundations of the present invention is an earthquake-resistant design system for composite ground pile foundations including piles and soil improvement bodies arranged around the piles, and is characterized by comprising: a specification setting means for setting the specifications of the soil improvement bodies and the piles; a ground response analysis means for performing dynamic analysis on a one-dimensional model of only the ground realized as free ground as the analysis object to estimate the ground response when an earthquake occurs; a pile stress estimation means for estimating the stress of the piles when an earthquake occurs by applying the horizontal force acting on the pile head and the estimated ground response to a two-dimensional or three-dimensional finite element model including the ground, the piles, and the soil improvement bodies and performing static analysis; and a design verification means for comparing the estimated pile stress with a threshold value and verifying whether the pile stress is below the threshold value. With this configuration, a one-dimensional model of only the ground realized as free ground is used as the analysis object, and dynamic analysis is performed to estimate the ground response during an earthquake. Furthermore, the horizontal force acting on the pile head and the estimated ground response are applied to a two-dimensional or three-dimensional finite element model including the ground, piles, and ground improvement body, and static analysis is performed to estimate the pile stress during an earthquake. In this configuration, the pile stress is estimated by static analysis of the finite element model. This finite element model is configured with the pile and ground improvement body installed in the ground. This makes it possible to accurately estimate the pile stress taking into account the effect of ground displacement at the pile installation location when a ground improvement body is installed in the ground. Here, the one-dimensional model that is the analysis target in dynamic analysis is realized by the ground only, and does not include the ground improvement body and piles. Therefore, even if the specifications of the ground improvement body and piles change, the dynamic analysis does not need to be performed again. In other words, the motion analysis, which requires a lot of calculation time, only needs to be performed once, using the one-dimensional model of the ground as the analysis target. Therefore, the number of times that dynamic analysis, which requires a lot of calculation time, is performed can be reduced. This makes it possible to shorten the time required to design the piles and ground improvement body. As a result, it is possible to provide an earthquake-resistant design system for composite ground pile foundations that can reduce the time required to design piles and ground improvement bodies when ground improvement bodies are installed around the piles. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an earthquake-resistant design system for composite ground pile foundations that can reduce the time required to design piles and ground improvement bodies when the ground improvement body is installed around the piles. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view schematically showing an example of a composite ground pile foundation designed using the earthquake-resistant design system for a composite ground pile foundation according to each embodiment of the present invention. [Figure 2] 1 is a block diagram showing the functional configuration of a seismic design system for a composite soil pile foundation according to a first embodiment of the present invention. [Figure 3] FIG. 1 is a diagram showing an example of a finite element model in which only a ground improvement body is provided in the ground, used for estimating ground displacement at a position corresponding to a pile by static analysis in the first embodiment of the present invention. [Figure 4] 1 is a flowchart showing the flow of an earthquake-resistant design method for a composite ground pile foundation using the earthquake-resistant design system for a composite ground pile foundation in the first embodiment of the present invention. [Figure 5] FIG. 10 is a block diagram showing the functional configuration of the earthquake-resistant design system for a composite soil pile foundation according to a second embodiment of the present invention. [Figure 6]FIG. 10 is a diagram showing an example of a finite element model in which only a ground improvement body is provided in the ground, used for estimating ground displacement at a position corresponding to a pile by dynamic analysis in the second embodiment of the present invention. [Figure 7] 10 is a flowchart showing the flow of an earthquake-resistant design method for a composite ground pile foundation using the earthquake-resistant design system for a composite ground pile foundation in the second embodiment of the present invention. [Figure 8] FIG. 10 is a block diagram showing the functional configuration of the earthquake-resistant design system for a composite soil pile foundation according to a third embodiment of the present invention. [Figure 9] FIG. 11 is a diagram showing an example of a finite element model including ground, piles, and soil improvement bodies, used for estimating stress in piles by static analysis in the third embodiment of the present invention. [Figure 10] 10 is a flowchart showing the flow of an earthquake-resistant design method for a composite ground pile foundation using the earthquake-resistant design system for a composite ground pile foundation in the third embodiment of the present invention. [Figure 11] FIG. 10 is a diagram showing the depth distribution of the bending moment of the piles in the examples and comparative examples in the study example of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] This invention is an earthquake-resistant design system that shows an earthquake-resistant design method for composite soil pile foundations including piles and soil improvement bodies. Specifically, this invention does not perform dynamic FEM analysis of the ground, piles, and soil improvement bodies as a whole, but performs dynamic FEM analysis of only the ground and soil improvement bodies as a whole, excluding the piles, or performs earthquake response analysis of the free ground excluding the piles and soil improvement bodies, estimates the inertial force acting on the pile head and ground displacement, compares and verifies the pile stress during an earthquake with a threshold value, and keeps the pile stress below the threshold value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment for carrying out the earthquake-resistant design system for a composite soil pile foundation according to the present invention will be described with reference to the accompanying drawings. (First embodiment) Fig. 1 is a cross-sectional view showing a schematic example of a composite ground pile foundation designed using the earthquake-resistant design system for a composite ground pile foundation according to each embodiment of the present invention. Fig. 2 is a block diagram showing the functional configuration of the earthquake-resistant design system for a composite ground pile foundation according to the first embodiment of the present invention. As shown in FIG. 1 , a composite soil pile foundation 1 designed using the earthquake-resistant design system for composite soil pile foundations according to each embodiment of the present invention includes a pile 2 constructed in the ground G and a soil improvement body 3 provided around the pile 2. The ground G may include a bearing layer B. The pile 2 is provided, for example, so as to extend vertically in the ground G with its lower end reaching the bearing layer B in the ground G. In this embodiment, the soil improvement body 3 is provided only on the upper part of the pile 2. The soil improvement body 3 may be formed so as to surround the pile 2 over the entire length of the pile 2. As shown in Fig. 2, the seismic design system 10 for composite soil pile foundations includes a specification setting means 11, a ground response analysis means 12, a ground displacement estimation means 13, a pile stress estimation means 14, and a design verification means 15. This seismic design system 10 for composite soil pile foundations is used when designing a composite soil pile foundation 1 so that it has the required seismic resistance. The seismic design system 10 for composite soil pile foundations is realized by the cooperation of a computer device as hardware including a processor, memory, storage device, etc., and a computer program as pre-stored software.

[0014] The specification setting means 11 sets the specifications of the ground improvement body 3 and the piles 2 through external input operations by the designer. The designer (provisionally) sets specifications for the composite ground pile foundation 1 to be formed in the ground G, such as the arrangement, number, structure, and material of the piles 2, and the formation method, dimensions, and material of the ground improvement body 3 to be formed around each pile 2. The ground response analysis means 12 estimates the ground response when an earthquake occurs. In this embodiment, the ground response analysis means 12 performs dynamic analysis on a one-dimensional model of only the ground G as an analysis target to estimate the earthquake response. For the dynamic analysis of the one-dimensional model of the ground G, appropriate analysis means can be used, such as multiple reflection theory or earthquake response analysis that takes into account ground nonlinearity. The one-dimensional model of the ground G to be analyzed is realized as free ground in a state before construction of the composite ground pile foundation 1, where piles 2, soil improvement bodies 3, etc. are not installed. The ground response analysis means 12 estimates the ground response when an earthquake occurs by dynamically analyzing the one-dimensional model of only the ground G realized as free ground. The estimated ground response may be evaluated by seismic intensity from the acceleration when the earthquake occurs, or by evaluating the ground stress acting when the earthquake occurs.

[0015] FIG. 3 is a diagram showing an example of a finite element model in which only a ground improvement body is provided in the ground, used for estimating ground displacement at a position corresponding to a pile by static analysis in the first embodiment of the present invention. The ground displacement estimation means 13 estimates the ground displacement at the position corresponding to the pile 2 when an earthquake occurs, based on the ground response estimated by the ground response analysis means 12. As shown in FIG. 3, the ground displacement estimation means 13 constructs a two-dimensional or three-dimensional finite element model M1 in which only the ground improvement body 3 is provided in the ground G, and performs static analysis by applying the estimated ground response to the finite element model M1. The finite element model M1 is configured so that no pile 2 is provided. The static analysis here is performed by applying the seismic intensity S1 to all nodes of the two-dimensional or three-dimensional finite element model M1 in which only the ground improvement body 3 is provided in the ground G, if the seismic intensity at the time of the earthquake is estimated as the ground response, or by applying the nodal force S1 evaluated from the ground stress if the ground stress is estimated, to all nodes of the finite element model M1. This allows for estimation of ground displacement at the position P1 corresponding to the pile 2 at the time of ground generation, that is, at the position P1 where the pile 2 would be installed if the finite element model M1 were constructed so that the pile 2 would be installed. When multiple piles 2 are installed, the finite element model M1 is constructed to include the ground improvement bodies 3 corresponding to all of these piles 2, so static analysis using the finite element model M1 does not need to be performed for each pile 2.

[0016] The pile stress estimation means 14 estimates the stress of the pile 2 when an earthquake occurs. The pile stress estimation means 14 applies the horizontal force Fh acting on the pile head 2t and the ground displacement estimated by the ground displacement estimation means 13 to a beam-spring model M1s, which analyzes the pile 2 alone, to estimate the stress of the pile 2 when an earthquake occurs. Specifically, the inertial force of the structure constructed on the composite soil pile foundation 1 is applied as a horizontal force Fh acting on the pile head 2h to the beam-spring model M1s, which simulates the pile 2 and the ground G. In addition, the ground displacement estimated by the ground displacement estimation means 13 is applied as a forced displacement to the beam-spring model M1s via the ground spring Sg. Then, the stress acting on the pile 2 is calculated. Here, the ground spring Sg must be set taking into account the resistance of the ground improvement body 3. If the spring value of the ground spring Sg is known, it can be used. If the spring value of the ground spring Sg is unknown, for example, the ground G, ground improvement body 3, and pile 2 can be modeled as a three-dimensional finite element model, and an analysis can be performed in which a horizontal force Fh acts on the pile head 2t, and the ground spring Sg can be set from the ground reaction force received by the pile 2. This method enables highly accurate evaluation by dividing the elements of the finite element model into smaller pieces to some extent and taking into account the strain of the ground G and ground improvement body 3, and the rigidity and strength against confining pressure nonlinearity. The design verification means 15 compares the stress acting on the pile 2 when an earthquake occurs, estimated by the pile stress estimation means 14, with a preset threshold value, and verifies whether the stress acting on the pile 2 is below the threshold value. When there are a plurality of piles 2, the pile stress estimation means 14 and the design verification means 15 execute their respective processes for each pile 2.

[0017] FIG. 4 is a flowchart showing the flow of the earthquake-resistant design method for a composite soil pile foundation using the earthquake-resistant design system for a composite soil pile foundation in the first embodiment of the present invention. 4, in order to perform the seismic design of the composite soil pile foundation 1, first, the ground response analysis means 12 performs a dynamic analysis on a one-dimensional model of only the ground G as free ground to estimate the earthquake response. The ground response analysis means 12 estimates the ground response at the time of earthquake occurrence as seismic intensity or ground stress by performing a dynamic analysis on the one-dimensional model of only the ground G realized as free ground (step S11). Next, the specifications of the soil improvement body 3 and the piles 2 are set by the specification setting means 11 through an external input operation by the designer (step S12). Next, the ground displacement estimation means 13 estimates the ground displacement at position P1 (see FIG. 3) corresponding to the pile 2 at the time of the earthquake based on the ground response estimated by the ground response analysis means 12. The ground displacement estimation means 13 constructs a two-dimensional or three-dimensional finite element model M1 in which only the ground improvement body 3 is provided in the ground G, and performs a static analysis by applying the ground response estimated in step S11 to the finite element model M1. The static analysis is performed by applying a seismic intensity S1 to all nodes of the two-dimensional or three-dimensional finite element model M1 in which only the ground improvement body 3 is provided in the ground G, if the seismic intensity at the time of the earthquake is estimated as the ground response, or a nodal force S1 evaluated from the ground stress if the ground stress is estimated, to all nodes of the finite element model M1. This allows the ground displacement at position P1 corresponding to the pile 2 at the time of the ground displacement to be estimated (step S13).

[0018] Next, the pile stress estimation means 14 estimates the stress of the pile 2 when an earthquake occurs. The pile stress estimation means 14 applies the horizontal force Fh acting on the pile head 2t and the ground displacement estimated by the ground displacement estimation means 13 to a beam-spring model M1s that analyzes the pile 2 alone, and estimates the stress of the pile 2 when an earthquake occurs (step S14). Next, the design verification means 15 compares the stress acting on the pile 2 when an earthquake occurs, estimated in step S14, with a preset threshold value, and verifies whether the stress acting on the pile 2 is equal to or less than the threshold value (step S15). As a result, if the stress acting on the pile 2 is equal to or less than the threshold value (Yes in step S15), the specifications of the pile 2 and the soil improvement body 3 set in step S12 are appropriate, and the processing ends. On the other hand, if the stress acting on the pile 2 is not equal to or less than the threshold value (No in step S15), first, for example, by determining whether the stress of the pile in the part where the ground improvement body 3 is installed is appropriate, it is confirmed whether it is appropriate to determine that the specifications of the ground improvement body 3 have been finalized (step S16). As a result, if it cannot be determined that the specifications of the ground improvement body 3 have been finalized (No in step S16), the process returns to step S12, and the specifications of the ground improvement body 3 and the pile 2 are changed and set. Thereafter, in step S13, a static analysis is performed using a two-dimensional or three-dimensional finite element model M1 in which only the ground improvement body 3 with changed specifications is installed. Furthermore, if it is determined in step S16 that the specifications of the ground improvement body 3 have been finalized (Yes in step S16), the specifications of only the pile 2 are changed (step S17). In this case, the specifications of the ground improvement body 3 are not changed, so there is no need to construct a finite element model M1 in which only the ground improvement body 3 is provided, and to perform static analysis using the finite element model M1 in step S13. Therefore, the process returns to step S14, and the stress of the pile 2 in the event of an earthquake is estimated for the pile 2 after the specifications have been changed. In this way, in step S15, the specifications of the soil improvement body 3 and the pile 2 are repeatedly changed as necessary until the stress acting on the pile 2 becomes equal to or less than the threshold value.

[0019] According to the above-described earthquake-resistant design system 10 for a composite ground pile foundation, the earthquake-resistant design system 10 for a composite ground pile foundation 1 including a pile 2 and a soil improvement body 3 provided around the pile 2 includes a specification setting means 11 for setting the specifications of each of the soil improvement body 3 and the pile 2, a ground response analysis means 12 for performing dynamic analysis on a one-dimensional model of only the ground G realized as free ground as an analysis object to estimate the ground response when an earthquake occurs, and a ground response analysis means 13 for performing dynamic analysis on a one-dimensional model of only the ground G realized as free ground to estimate the ground response when an earthquake occurs. The system is equipped with a ground displacement estimation means 13 that estimates ground displacement at a position corresponding to pile 2 when an earthquake occurs by applying the horizontal force Fh acting on the pile head 2t and the estimated ground displacement to a beam-spring model M1s that analyzes pile 2, and a pile stress estimation means 14 that estimates the stress of pile 2 when an earthquake occurs by applying the horizontal force Fh acting on pile head 2t and the estimated ground displacement to a beam-spring model M1s that analyzes pile 2, and a design verification means 15 that compares the estimated stress of pile 2 with a threshold value and verifies whether the stress of pile 2 is below the threshold value. According to this configuration, dynamic analysis is performed on a one-dimensional model of only the ground G realized as free ground to estimate the ground response during an earthquake. This estimated ground response is applied to a two-dimensional or three-dimensional finite element model M1, in which only the ground improvement body 3 is installed in the ground G, and static analysis is performed to estimate ground displacement at a position corresponding to the pile 2 during an earthquake. The horizontal force Fh acting on the pile head 2t and the estimated ground displacement are applied to a beam-spring model M1s, in which the pile 2 is the analysis object, to estimate the stress in the pile 2 during an earthquake. In this configuration, the ground displacement applied to the beam-spring model M1s when estimating the stress in the pile 2 is estimated by static analysis of the finite element model M1. This finite element model M1 is configured so that the ground improvement body 3 is installed in the ground G. This allows for accurate estimation of the stress in the pile 2, taking into account the influence of ground displacement at the position where the pile 2 is installed when the ground improvement body 3 is installed in the ground G. Here, the one-dimensional model that is the analysis target in the dynamic analysis is realized only with the ground G, and does not include the ground improvement body 3 and the piles 2. Therefore, even if the specifications of the ground improvement body 3 and the piles 2 change, the dynamic analysis does not need to be performed again. In other words, the motion analysis, which requires a lot of calculation time, only needs to be performed once, with the one-dimensional model of only the ground G as the analysis target. Therefore, the number of times that dynamic analysis, which requires a lot of calculation time, is performed can be reduced. Furthermore, since the finite element model M1 that is the subject of static analysis has a configuration in which only the ground improvement body 3 is provided in the ground G, if the specifications of the pile 2 are changed and the stress of the pile 2 is to be re-estimated, there is no need to reconstruct the finite element model M1 and re-run static analysis using the finite element model M1 as long as the specifications of the ground improvement body 3 have been finalized. Therefore, the number of times static analysis is performed can be reduced. Furthermore, since the finite element model M1 is provided with only the ground improvement body 3, in other words, without the piles 2, the element division of the finite element model M1 can be realized in a rough state without considering the piles 2. Therefore, the time required for one analysis is reduced. The above effects are combined to reduce the time required to design the piles 2 and the soil improvement body 3. As a result, it is possible to provide an earthquake-resistant design system 10 for a composite ground pile foundation 1 that can reduce the time required to design the pile 2 and the ground improvement body 3 when the ground improvement body 3 is installed around the pile 2.

[0020] As described above, by reducing the time required to design the piles 2 and the soil improvement body 3, it is possible to perform a more detailed analysis and to carry out a more accurate design. Furthermore, when constructing the finite element model M1, if the pile 2 is installed in the finite element model M1, the ground improvement body 3 and ground G in contact with the pile 2 become largely nonlinear locally, and therefore accurate analysis cannot be performed unless the element division is finely divided. Here, in a static analysis using the finite element model M1 in which only the ground improvement body 3 is installed in the ground G, the finite element model M1 is constructed so as not to include the pile 2, and therefore the element division can be made coarse to a certain extent. This enables the analysis to be performed more quickly. Furthermore, in conventional methods, when modeling the piles, ground improvement body, and surrounding ground as a single unit and performing dynamic FEM analysis, it was difficult to finely divide the elements of the improvement body and ground around the piles due to the calculation load.However, in this embodiment, even if the elements are finely divided, the calculation time is not an issue, making it possible to evaluate the ground springs with high accuracy. In addition, the ground spring Sg set by the pile stress estimation means 14 can be a ground spring that takes into account the improved body obtained through experiments, etc., or a ground spring indicated by a guideline, etc.

[0021] (Second embodiment) FIG. 5 is a block diagram showing the functional configuration of the earthquake-resistant design system for a composite soil pile foundation according to the second embodiment of the present invention. As shown in FIG. 5, the earthquake-resistant design system 20 for composite soil pile foundations includes a specification setting means 21, a ground displacement estimating means 22, a pile stress estimating means 23, and a design verification means 24.

[0022] The specification setting means 21 sets the specifications of the ground improvement body 3 and the piles 2 through external input operations by the designer. The designer (provisionally) sets specifications for the composite ground pile foundation 1 to be formed in the ground G, such as the arrangement, number, structure, and material of the piles 2, and the formation method, dimensions, and material of the ground improvement body 3 to be formed around each pile 2.

[0023] FIG. 6 is a diagram showing an example of a finite element model in which only soil improvement bodies are provided in the ground, used for estimating ground displacement at positions corresponding to piles by dynamic analysis in the second embodiment of the present invention. As shown in Fig. 6, the ground displacement estimation means 22 constructs a two-dimensional or three-dimensional finite element model M2 in which only the soil improvement body 3 is provided in the ground G, and estimates ground displacement at position P2 corresponding to the pile 2 when an earthquake occurs by performing dynamic analysis using the finite element model M2. The finite element model M2 is configured so that the pile 2 is not provided. Therefore, dynamic analysis estimates ground displacement at position P2 corresponding to the pile 2, i.e., position P2 where the pile 2 would be provided if the finite element model M2 were constructed so that the pile 2 would be provided.

[0024] The pile stress estimation means 23 estimates the stress of the pile 2 when an earthquake occurs. The pile stress estimation means 23 applies the horizontal force Fh acting on the pile head 2t and the ground displacement estimated by the ground displacement estimation means 22 to a beam-spring model M2s, which analyzes the pile 2 alone, to estimate the stress of the pile 2 when an earthquake occurs. Specifically, the inertial force of the structure constructed on the composite soil pile foundation 1 is applied as a horizontal force Fh acting on the pile head 2h to the beam-spring model M2s, which simulates the pile 2 and the ground G. In addition, the ground displacement estimated by the ground displacement estimation means 22 is applied as a forced displacement to the beam-spring model M2s via the ground spring Sg. Then, the stress acting on the pile 2 is calculated. The design verification means 24 compares the stress acting on the pile 2 during an earthquake, estimated by the pile stress estimation means 23, with a preset threshold value, and verifies whether the stress acting on the pile 2 is below the threshold value.

[0025] FIG. 7 is a flowchart showing the flow of the earthquake-resistant design method for a composite soil pile foundation using the earthquake-resistant design system for a composite soil pile foundation according to the second embodiment of the present invention. As shown in Figure 7, to perform seismic design of a composite ground pile foundation 1, first, the designer sets the specifications of the ground improvement body 3 and the pile 2 using external input operations in the specification setting means 21 (step S21). Next, the ground displacement estimation means 22 evaluates the ground displacement at the position P2 corresponding to the pile 2 when an earthquake occurs (step S22). The ground displacement estimation means 22 constructs a two-dimensional or three-dimensional finite element model M2 in which only the ground improvement body 3 is provided in the ground G, and estimates the ground displacement at the position P2 corresponding to the pile 2 when an earthquake occurs by performing dynamic analysis using the finite element model M2. Next, the pile stress estimation means 23 estimates the stress of the pile 2 when an earthquake occurs. The pile stress estimation means 23 applies the horizontal force Fh acting on the pile head 2t and the ground displacement estimated by the ground displacement estimation means 22 to a beam-spring model M2s that analyzes the pile 2 alone, and estimates the stress of the pile 2 when an earthquake occurs (step S23).

[0026] Next, the design verification means 24 compares the stress acting on the pile 2 in the event of an earthquake, estimated in step S23, with a preset threshold value, and verifies whether the stress acting on the pile 2 is equal to or less than the threshold value (step S24). As a result, if the stress acting on the pile 2 is equal to or less than the threshold value (Yes in step S24), it is confirmed that the specifications of the pile 2 and the soil improvement body 3 set in step S21 are appropriate, and the process ends. On the other hand, if the stress acting on the pile 2 is not equal to or less than the threshold value (No in step S24), first, for example, by determining whether the stress of the pile in the part where the soil improvement body 3 is installed is appropriate, it is confirmed whether it is acceptable to determine that the specifications of the soil improvement body 3 have been finalized (step S25). As a result, if it cannot be determined that the specifications of the soil improvement body 3 have been finalized (No in step S25), the process returns to step S21, and the specifications of the soil improvement body 3 and the pile 2 are changed and set. Thereafter, in step S22, a dynamic analysis is performed using a two-dimensional or three-dimensional finite element model M2 in which only the soil improvement body 3 with changed specifications is installed. Furthermore, if it is determined in step S25 that the specifications of the ground improvement body 3 have been finalized (Yes in step S25), the specifications of only the pile 2 are changed (step S26). In this case, the specifications of the ground improvement body 3 are not changed, so there is no need to construct a finite element model M2 in which only the ground improvement body 3 is provided, and to perform dynamic analysis using the finite element model M2 in step S22. Therefore, the process returns to step S23, and the stress of the pile 2 when an earthquake occurs is estimated for the pile 2 after the specifications have been changed. In this way, in step S24, the specifications of the soil improvement body 3 and the pile 2 are repeatedly changed as necessary until the stress acting on the pile 2 becomes equal to or less than the threshold value.

[0027] According to the earthquake-resistant design system 20 for composite ground pile foundations as described above, the earthquake-resistant design system 20 for a composite ground pile foundation 1 including a pile 2 and a ground improvement body 3 provided around the pile 2 includes: a specification setting means 21 for setting the specifications of the ground improvement body 3 and the pile 2; a ground displacement estimation means 22 for estimating ground displacement at a position corresponding to the pile 2 when an earthquake occurs by performing dynamic analysis using a two-dimensional or three-dimensional finite element model M2 in which only the ground improvement body 3 is provided in the ground G; a pile stress estimation means 23 for applying the horizontal force Fh acting on the pile head 2t and the estimated ground displacement to a beam-spring model M2s for analyzing the pile 2 to estimate the stress of the pile 2 when an earthquake occurs; and a design verification means 24 for comparing the estimated stress of the pile 2 with a threshold value and verifying whether the stress of the pile 2 is below the threshold value. According to this configuration, dynamic analysis is performed using a two-dimensional or three-dimensional finite element model M2 in which only the ground improvement body 3 is installed in the ground G to estimate ground displacement at position P2 corresponding to the pile 2 during an earthquake. Furthermore, the horizontal force Fh acting on the pile head 2t and the estimated ground displacement are applied to a beam-spring model M2s in which the pile 2 is the analysis target, to estimate the stress in the pile 2 during an earthquake. In this configuration, the ground displacement applied to the beam-spring model M2s when estimating the stress in the pile 2 is estimated by dynamic analysis of the finite element model M2. This finite element model M2 is configured so that the ground improvement body 3 is installed in the ground G. Therefore, when the ground improvement body 3 is installed in the ground G, the stress in the pile 2 can be accurately estimated taking into account the influence of ground displacement at position P2 where the pile 2 is installed. Here, the finite element model M2 to be subjected to dynamic analysis has a configuration in which only the ground improvement body 3 is provided in the ground G. Therefore, when the specifications of the pile 2 are changed and the stress of the pile 2 is to be re-estimated, as long as the specifications of the ground improvement body 3 are fixed, there is no need to reconstruct the finite element model M2 and re-run the dynamic analysis using the finite element model M2. Therefore, it is possible to reduce the number of times dynamic analysis, which requires a very long calculation time, is performed. Furthermore, since the finite element model M2 is provided with only the ground improvement body 3, in other words, without the piles 2, the element division of the finite element model M2 can be realized in a rough state without considering the piles 2. Therefore, the time required for one analysis is reduced. The above effects are combined to reduce the time required to design the piles 2 and the soil improvement body 3. As a result, it is possible to provide an earthquake-resistant design system 20 for a composite ground pile foundation 1 that can reduce the time required to design the pile 2 and the ground improvement body 3 when the ground improvement body 3 is installed around the pile 2.

[0028] As described above, by reducing the time required to design the piles 2 and the soil improvement body 3, it is possible to perform a more detailed analysis and to carry out a more accurate design. Furthermore, when constructing the finite element model M2, if the pile 2 is installed in the finite element model M2, the ground improvement body 3 and ground G in contact with the pile 2 become largely nonlinear locally, and therefore accurate analysis cannot be performed unless the element division is finely divided. Here, in a static analysis using the finite element model M2 in which only the ground improvement body 3 is installed in the ground G, the finite element model M2 is constructed so as not to include the pile 2, and therefore the element division can be made coarse to a certain extent. This enables the analysis to be performed more quickly.

[0029] (Third embodiment) FIG. 8 is a block diagram showing the functional configuration of the earthquake-resistant design system for a composite soil pile foundation according to the third embodiment of the present invention. As shown in Figure 8, the earthquake-resistant design system 30 for a composite soil pile foundation according to this embodiment includes a specification setting means 31, a ground response analysis means 32, a pile stress estimation means 33, and a design verification means 34. The specification setting means 31 sets the specifications of the ground improvement body 3 and the piles 2 through external input operations by the designer. The designer (provisionally) sets specifications for the composite ground pile foundation 1 to be formed in the ground G, such as the arrangement, number, structure, and material of the piles 2, and the formation method, dimensions, and material of the ground improvement body 3 to be formed around each pile 2. The ground response analysis means 32 estimates the ground response when an earthquake occurs. In this embodiment, the ground response analysis means 32 performs dynamic analysis on a one-dimensional model of only the ground G as an analysis target to estimate the earthquake response. The ground response analysis means 32 evaluates the ground response when an earthquake occurs as seismic intensity or ground stress by performing dynamic analysis on the one-dimensional model of only the ground G realized as free ground.

[0030] FIG. 9 is a diagram showing an example of a finite element model including ground, piles, and soil improvement bodies, used for estimating stress in piles by static analysis in the third embodiment of the present invention. The pile stress estimation means 33 estimates the stress of the pile 2 when an earthquake occurs. As shown in Figure 9, the pile stress estimation means 33 constructs a two-dimensional or three-dimensional finite element model M3 including the ground G, the pile 2, and the soil improvement body 3, and performs a static analysis by applying the horizontal force Fh acting on the pile head 2t and the ground response estimated by the ground response analysis means 32 to the finite element model M3. To do this, if the seismic intensity at the time of an earthquake is estimated as the ground response, the seismic intensity is applied to all nodes of the two-dimensional or three-dimensional finite element model M3 including the ground G, the pile 2, and the soil improvement body 3. If the ground stress is estimated, the nodal force evaluated from the ground stress is applied to all nodes of the finite element model M3. This allows the stress acting on the pile 2 when an earthquake occurs to be calculated. The design verification means 34 compares the stress acting on the pile 2 during an earthquake, estimated by the pile stress estimation means 33, with a predetermined threshold value, and verifies whether the stress acting on the pile 2 is below the threshold value.

[0031] FIG. 10 is a flowchart showing the flow of the earthquake-resistant design method for a composite soil pile foundation using the earthquake-resistant design system for a composite soil pile foundation according to the third embodiment of the present invention. 10, in order to perform the seismic design of the composite soil pile foundation 1, first, the ground response analysis means 32 performs a dynamic analysis on a one-dimensional model of only the ground G as free ground to estimate the earthquake response. The ground response analysis means 32 estimates the ground response at the time of an earthquake occurrence as seismic intensity or ground stress by performing a dynamic analysis on the one-dimensional model of only the ground G realized as free ground (step S31). Next, the specifications of the soil improvement body 3 and the piles 2 are set by the specification setting means 31 through an external input operation by the designer (step S32). Next, the pile stress estimation means 33 estimates the stress of the pile 2 when an earthquake occurs (step S33). The pile stress estimation means 33 applies the horizontal force Fh acting on the pile head 2t and the ground response estimated by the ground response analysis means 32 to a two-dimensional or three-dimensional finite element model M3 including the ground G, the pile 2, and the ground improvement body 3, and performs a static analysis. Thereafter, the design verification means 34 compares the stress acting on the pile 2 in the event of an earthquake, estimated in step S33, with a preset threshold value, and verifies whether the stress acting on the pile 2 is equal to or less than the threshold value (step S34). As a result, if the stress acting on the pile 2 is equal to or less than the threshold value (Yes in step S34), the specifications of the pile 2 and the soil improvement body 3 set in step S32 are appropriate, and the processing ends. On the other hand, if the stress acting on the pile 2 is not equal to or less than the threshold value (No in step S34), the process returns to step S32, and the specifications of the ground improvement body 3 and the pile 2 are changed and set. Then, in step S33, static analysis is performed using the pile 2 with the changed specifications and a two-dimensional or three-dimensional finite element model M3 in which the ground improvement body 3 is installed. In this way, in step S34, changes to the specifications of the ground improvement body 3 and the pile 2 are repeated as necessary until the stress acting on the pile 2 becomes equal to or less than the threshold value.

[0032] According to the above-mentioned earthquake-resistant design system 30 for composite ground pile foundations, the earthquake-resistant design system 30 for a composite ground pile foundation 1 including a pile 2 and a ground improvement body 3 provided around the pile 2 includes: a specification setting means 31 for setting the specifications of the ground improvement body 3 and the pile 2; a ground response analysis means 32 for performing dynamic analysis of a one-dimensional model of only the ground G realized as free ground as the analysis object to estimate the ground response when an earthquake occurs; a pile stress estimation means 33 for estimating the stress of the pile 2 when an earthquake occurs by applying the horizontal force Fh acting on the pile head 2t and the estimated ground response to a two-dimensional or three-dimensional finite element model M3 including the ground G, the pile 2, and the ground improvement body 3 and performing static analysis; and a design verification means 34 for comparing the estimated stress of the pile 2 with a threshold value and verifying whether the stress of the pile 2 is below the threshold value. With this configuration, a one-dimensional model of only the ground G realized as free ground is used as the analysis object, and dynamic analysis is performed to estimate the ground response during an earthquake. Furthermore, the horizontal force Fh acting on the pile head 2t and the estimated ground response are applied to a two-dimensional or three-dimensional finite element model M3 including the ground G, the pile 2, and the ground improvement body 3, and static analysis is performed to estimate the stress in the pile 2 during an earthquake. In this configuration, the stress in the pile 2 is estimated by static analysis of the finite element model M3. This finite element model M3 is configured such that the ground improvement body 3 is installed in the ground G. Therefore, when the ground improvement body 3 is installed in the ground G, the stress in the pile 2 can be accurately estimated, taking into account the effect of ground displacement at the location where the pile 2 is installed. Here, the one-dimensional model that is the analysis target in the dynamic analysis is realized only by the ground G, and does not include the ground improvement body 3 and the piles 2. Therefore, even if the specifications of the ground improvement body 3 and the piles 2 change, the dynamic analysis does not need to be performed again. In other words, the motion analysis, which requires a lot of calculation time, only needs to be performed once, using the one-dimensional model of the ground G as the analysis target. Therefore, the number of times that dynamic analysis, which requires a lot of calculation time, is performed can be reduced. This makes it possible to reduce the time required to design the piles 2 and the ground improvement body 3. As a result, it is possible to provide an earthquake-resistant design system 30 for a composite ground pile foundation 1 that can reduce the time required to design the pile 2 and the ground improvement body 3 when the ground improvement body 3 is installed around the pile 2.

[0033] In this embodiment, the finite element model M3 to be subjected to static analysis is a detailed one constructed to include not only the ground G and the ground improvement body 3 but also the pile 2. Therefore, in the static analysis, the stress of the pile 2 is estimated, and the stress acting on the ground improvement body 3 is also estimated at the same time, and the stress acting on the ground improvement body 3 can be used to examine the composite ground pile foundation 1.

[0034] <Example of consideration> The accuracy of pile stress evaluation for composite ground pile foundations using the above-described earthquake-resistant design system for composite ground pile foundations was examined, and the results are presented below. The study was conducted on a single pile 2 equipped with a ground improvement body 3, as shown in Figure 1. (Example) For the configuration shown in the first embodiment, first, the ground G before improvement was modeled one-dimensionally, and an earthquake response analysis was performed to determine the shear stress of the ground G. Next, nodal forces were evaluated from the determined shear stress, and a static analysis was performed in which the nodal forces were applied to a three-dimensional finite element model M1 consisting only of the ground G and the ground improvement body 3, to evaluate the ground displacement at position P1 corresponding to the pile 2. After that, the ground displacement was applied as a forced displacement to a beam-spring model M1s via a ground spring Sg, and was applied simultaneously with a horizontal force Fh at the pile head 2t, to evaluate the stress of the pile 2. (Comparative Example) For comparison, ground G, ground improvement body 3, and pile 2 were made into a three-dimensional finite element model, with a mass point simulating the weight of the structure installed at the pile head. The rotational degree of freedom of the head of pile 2 was fixed so that it was rigidly connected to the footing. Earthquake motion was input into this three-dimensional finite element model, and the stress (bending moment) acting on pile 2 was evaluated by performing an earthquake response analysis.

[0035] FIG. 11 is a diagram showing the depth distribution of bending moments of piles in the examples and comparative examples in the study example of this embodiment. As shown in Figure 11, the results of the example and comparative example are generally consistent at the pile head, where the bending moment is greatest, and it can be seen that the method of this embodiment can obtain results equivalent to those of the conventional method. Furthermore, in the example, it took several seconds to analyze the finite element model M1, whereas in the comparative example, it took several hours to process the earthquake response analysis of the three-dimensional finite element model of the ground G, ground improvement body 3, and pile 2. Furthermore, as shown in Figure 11, even with the method using partial static analysis according to this embodiment, it was found that it was possible to confirm the bending moment distribution of the pile along the depth direction of the pile, similar to the analysis results of the comparative example in which the pile, ground improvement body, and surrounding ground were modeled as a whole and dynamic FEM analysis was performed, and that it was possible to evaluate the improvement effect of the ground improvement body at the pile head.

[0036] (Modification of the embodiment) The earthquake-resistant design system for composite soil pile foundations of the present invention is not limited to the above-mentioned embodiments explained with reference to the drawings, and various other modifications are possible within the technical scope. For example, in the first and second embodiments described above, the pile stress estimation means 14, 23 estimated the stress of a pile by analyzing a single pile, but the pile stress may also be estimated by analyzing a group of piles in which multiple piles are driven into the ground. In addition to this, it is possible to select and discard the configurations given in the above embodiments, or to change them to other configurations as appropriate, without departing from the spirit of the present invention. [Explanation of symbols]

[0037] 1 Composite soil pile foundation 12, 32 Ground response analysis method 2 Pile 13, 22 Ground displacement estimation method 2t pile cap 14, 23, 33 Pile stress estimation method 3 Ground improvement body 15, 24, 34 Design verification method 10, 20, 30 Seismic Design Systems M1, M2, M3 Finite Element Models 11, 21, 31 Specification setting means M1s, M2s Beam spring model

Claims

1. A seismic design system for a composite ground pile foundation including a pile and a soil improvement body provided around the pile, A specification setting means for setting the specifications of the ground improvement body and the piles; a ground response analysis means for performing dynamic analysis on a one-dimensional model of only the ground realized as a free ground to estimate the ground response when an earthquake occurs; a ground displacement estimation means for estimating ground displacement at a position corresponding to the pile when an earthquake occurs by applying the estimated ground response to a two-dimensional or three-dimensional finite element model in which only the ground improvement body is provided in the ground and performing static analysis; a pile stress estimation means for estimating the stress of the pile when an earthquake occurs by applying the horizontal force acting on the pile head and the estimated ground displacement to a beam-spring model that analyzes the pile; a design verification means for comparing the estimated stress of the pile with a threshold value and verifying whether the stress of the pile is equal to or less than the threshold value; A composite ground pile foundation earthquake-resistant design system comprising:

2. A seismic design system for a composite ground pile foundation including a pile and a soil improvement body provided around the pile, A specification setting means for setting the specifications of the ground improvement body and the piles; a ground displacement estimation means for estimating ground displacement at a position corresponding to the pile when an earthquake occurs by performing dynamic analysis using a two-dimensional or three-dimensional finite element model in which only the ground improvement body is provided in the ground; a pile stress estimation means for estimating the stress of the pile when an earthquake occurs by applying the horizontal force acting on the pile head and the estimated ground displacement to a beam-spring model that analyzes the pile; a design verification means for comparing the estimated stress of the pile with a threshold value and verifying whether the stress of the pile is equal to or less than the threshold value; A composite ground pile foundation earthquake-resistant design system comprising:

3. A seismic design system for a composite ground pile foundation including a pile and a soil improvement body provided around the pile, A specification setting means for setting the specifications of the ground improvement body and the piles; a ground response analysis means for performing dynamic analysis on a one-dimensional model of only the ground realized as a free ground to estimate the ground response when an earthquake occurs; a pile stress estimation means for estimating the stress of the pile when an earthquake occurs by applying the horizontal force acting on the pile head and the estimated ground response to a two-dimensional or three-dimensional finite element model including the ground, the pile, and the ground improvement body and performing static analysis; a design verification means for comparing the estimated stress of the pile with a threshold value and verifying whether the stress of the pile is equal to or less than the threshold value; A composite ground pile foundation earthquake-resistant design system comprising:

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