Damage degree estimation system of foundation pile

Abstract

To easily and simply estimate damage degree of concrete foundation piles in the event of an earthquake.SOLUTION: A damage degree estimation system 1 for estimating damage degree of concrete foundation piles that support an upper structure of a structure 10 comprises: a sensor 17 installed in the upper structure to acquire vertical earthquake information of the upper structure; a vertical displacement calculation unit 22 that calculates vertical displacement of the upper structure from the vertical earthquake information; and a damage degree estimation unit 23 that estimates damage degree of the foundation piles based on the vertical displacement of the upper structure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a foundation pile damage degree estimation system for estimating the degree of damage to a concrete foundation pile that supports the superstructure of a structure.

Background Art

[0002] After an earthquake, various technologies have been proposed that can grasp the degree of damage to structures. In particular, in the case of concrete foundation piles, if damage occurs in the concrete part during an earthquake, residual settlement and residual inclination may occur in the structure. Therefore, it is desired not only to grasp the degree of damage to the structure but also to easily confirm the presence or absence of damage to the foundation pile and the degree of damage.

[0003] For example, Patent Document 1 discloses a pile inspection method for inspecting a pile body buried in the ground under a bearing plate. This pile inspection method includes a step of forming a hole in the bearing plate, a step of excavating the ground in the vertical direction using a rod passed through the hole, a step of excavating the ground between the rod and the pile body in the horizontal direction using the rod inserted into the ground from the hole, a step of discharging the excavated ground to form an inspection space for the pile body, and a step of inspecting the pile body using an inspection device attached to the rod inserted into the inspection space from the hole. In the configuration of Patent Document 1, since it is necessary to form a hole in the bearing plate and excavate the ground, a lot of cost and time are required to determine the presence or absence of damage to the pile body and the degree of damage.

[0004] Further, Patent Document 2 discloses a configuration in which, by using earthquake information acquired by a wireless accelerometer or a wireless strain gauge installed in a first layer corresponding to the position of the equivalent height in a one-degree-of-freedom vibration model simulating a structure (building), a first inter-story drift angle, which is the relative displacement amount with respect to ground motion in the first layer, is calculated, the seismic intensity at the building location is calculated based on the earthquake information, and the degree of damage to the structure after the earthquake is estimated by comparing the first inter-story drift angle with respect to ground motion and a predetermined threshold value. The configuration disclosed in Patent Document 2 estimates the degree of disaster of the superstructure (superstructure) supported by the foundation part in the ground in a structure, and is not for determining the presence or absence of damage to the foundation piles that make up the foundation part. Even if a wireless accelerometer or a wireless strain gauge is attached to an existing foundation pile in an attempt to apply the configuration of Patent Document 2 to the foundation pile, the behavior of the ground during an earthquake is complex, and the behavior of the foundation pile in contact with the ground is more complex than the behavior of the superstructure. Therefore, a more complex implementation corresponding to this is required. Therefore, it is difficult to determine the presence or absence of damage to the foundation pile using this configuration.

[0005] In addition to the configurations disclosed in Patent Documents 1 and 2 as described above, tapping the pile head lightly with a hammer or the like to generate elastic waves and measuring the reflected waveform obtained from an accelerometer installed at the pile head are also performed to confirm the presence or absence of damage such as cracks. However, since it is necessary to expose the vicinity of the pile head for this purpose, it is difficult to implement in a state where a structure is built on the foundation pile.

[0006] On the other hand, Patent Document 3 discloses a damage determination system for determining the presence or absence of damage to a concrete foundation pile that supports the superstructure of a structure. This damage determination system includes a plurality of sensors installed in the superstructure to acquire horizontal earthquake information and vertical earthquake information of the superstructure, and from the horizontal earthquake information and the vertical earthquake information, calculates the vibration frequency of the horizontal acceleration and the vibration frequency of the vertical acceleration, and a vibration frequency ratio calculation unit that calculates a vibration frequency ratio represented by the ratio of the vibration frequency of the vertical acceleration to the vibration frequency of the horizontal acceleration, and a damage determination unit that determines that there is damage to the foundation pile when the vibration frequency ratio is 1.8 or more and 2.2 or less. In the configuration of Patent Document 3, the presence or absence of damage to the foundation pile can be determined easily and simply, but when it is determined that there is damage, the degree of damage to the foundation pile cannot be estimated.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem to be solved by the present invention is to provide a foundation pile damage degree estimation system that can easily and simply estimate the degree of damage to a concrete foundation pile when an earthquake occurs.

Means for Solving the Problems

[0009] The inventor of the present invention has set a sensor in the superstructure connected to the foundation pile as a foundation pile damage degree estimation system, calculated the vertical displacement amount from the earthquake information obtained by the sensor, and compared the vertical displacement amount with the vertical displacement amount of the foundation pile calculated from the curvature of the foundation pile head with respect to the ultimate limit, so as to estimate the degree of damage to the foundation pile without excavating the ground around the foundation pile and visually checking the foundation pile. Based on this, the present invention has been achieved. In order to solve the above problems, the present invention adopts the following means. That is, the present invention is a damage degree estimation system for estimating the degree of damage to a concrete foundation pile that supports the superstructure of a structure, and includes a sensor installed in the superstructure to acquire earthquake information in the vertical direction of the superstructure, a vertical displacement amount calculation unit that calculates the vertical displacement amount of the superstructure from the earthquake information in the vertical direction, and a damage degree estimation unit that estimates the degree of damage to the foundation pile based on the vertical displacement amount of the superstructure. A foundation pile damage degree estimation system is provided, which is characterized by the above. When an earthquake occurs, especially in structures with a high aspect ratio of the superstructure (the ratio of the height of the structure to the width of the structure, tower ratio), due to the overturning moment caused by the inertial force of the superstructure, a rocking vibration occurs where the upper part swings left and right around the part near the ground, tilts, and rotates. To resist this rocking vibration, a compressive axial force acts on the foundation piles supporting the superstructure, which are located on the side where the superstructure tilts, that is, in the direction of the progress of the sway, so as to push the foundation piles in. Also, a tensile axial force acts on the foundation piles located on the opposite side so as to pull out the foundation piles. Here, in the case of concrete foundation piles, when the concrete of the foundation piles is damaged due to cracks, cross-sectional defects, etc., if the tensile axial force acting on the foundation piles caused by the rocking vibration exceeds the axial force of the self-weight of the structure that always acts on the foundation piles, or when a horizontal force acts on the foundation piles and the pile head bends and deforms, resulting in a large strain of the foundation piles, etc., the superstructure temporarily lifts up with respect to the foundation piles. As a result, in conjunction with the rocking vibration, a vertical displacement occurs in the superstructure. It is considered that the more severe the damage such as cracks and cross-sectional defects in the concrete of the foundation piles, the less able the concrete can resist the tensile axial force, and as a result, the amount of vertical displacement becomes larger. On the other hand, in the configuration as described above, from the vertical earthquake information of the superstructure obtained by the sensors installed on the superstructure, the vertical displacement amount, which is the vertical displacement amount of the superstructure, is calculated, and based on this, the degree of damage to the foundation piles is estimated. In this way, since the degree of damage to the foundation piles is estimated based on the vertical displacement amount, which is considered to increase as the damage to the foundation piles becomes more severe, the degree of damage is appropriately estimated. In such a system for estimating the degree of damage to foundation piles, basically, it is possible to be realized only by installing sensors on the superstructure. Therefore, the installation is easy. Also, the degree of damage to the foundation piles can be estimated only by performing a certain calculation on the earthquake information obtained by the sensors. Therefore, the degree of damage to the foundation piles can be estimated easily and simply. In this way, it becomes possible to provide a foundation pile damage degree estimation system that can easily and simply estimate the degree of damage to a concrete foundation pile when an earthquake occurs.

[0010] In one aspect of the present invention, the foundation pile includes reinforcing bars extending in the vertical direction and concrete embedding the reinforcing bars. When the curvature of the pile head of the foundation pile when an earthquake occurs matches the curvature of the pile head of the foundation pile when the ultimate limit is reached, the vertical displacement amount of the superstructure corresponding thereto is set as a first threshold value. When the vertical displacement amount of the superstructure is equal to or greater than the first threshold value, the damage degree estimation unit estimates that the foundation pile has reached the ultimate limit and is in a state of severe damage. When the vertical displacement amount of the superstructure is equal to or greater than a second threshold value and smaller than the first threshold value, it is estimated that there may be minor damage to the foundation pile. As described above, it has been found that during the process in which an earthquake occurs and the superstructure sways left and right, tilts, rotates due to the overturning moment, and damage occurs to the pile head of the foundation pile, there is a relationship between the degree of damage and the curvature of the pile head. Specifically, the curvature of the pile head is small until the ground motion reaches a certain magnitude, but when the ground motion increases and the reinforcing bars in the foundation pile where the tensile axial force acts yield, it increases rapidly. When a larger ground motion acts, the concrete part of the foundation pile where the compressive axial force acts reaches the ultimate limit, and the curvature of the pile head increases more significantly. According to the above configuration, by associating the curvature of the pile head with the vertical displacement amount of the superstructure, when the curvature of the pile head of the foundation pile when an earthquake occurs matches the curvature of the pile head of the foundation pile when the concrete reaches the ultimate limit, the vertical displacement amount of the superstructure corresponding thereto is set as the first threshold value. Thereby, when the vertical displacement amount of the superstructure is equal to or greater than the first threshold value, it is possible to estimate that the concrete has reached the ultimate limit, the curvature of the pile head has increased more significantly, and the foundation pile is in a state of severe damage. Further, the second threshold value is appropriately set to be smaller than the first threshold value, and when the vertical displacement amount of the superstructure is equal to or greater than the second threshold value and smaller than the first threshold value, it is possible to estimate that there may be slight damage to the foundation pile. By doing so, the degree of damage to the foundation pile can be estimated in more detail.

[0011] In another aspect of the present invention, the apparatus further includes a foundation pile sensor that acquires vertical earthquake information on the lower side of the foundation pile, and the vertical displacement amount calculation unit calculates the vertical displacement amount on the lower side of the foundation pile as the foundation pile vertical displacement amount based on the vertical earthquake information on the lower side of the foundation pile, calculates a provisional vertical displacement amount that is the provisional vertical displacement amount of the superstructure based on the vertical earthquake information of the superstructure, and subtracts the foundation pile vertical displacement amount from the provisional vertical displacement amount to calculate the vertical displacement amount of the superstructure. In an actual earthquake, not only horizontal shaking but also vertical shaking can occur simultaneously. In such a case, among the vertical displacement amounts calculated from the vertical earthquake information of the superstructure acquired by the sensor, the vertical displacement amount of the superstructure caused by the earthquake shaking itself is also mixed, and as a result, the vertical displacement amount of the superstructure caused by the damage to the foundation pile cannot be accurately extracted, and there is a possibility that an error may occur in estimating the degree of damage to the foundation pile. On the other hand, according to the above configuration, the foundation pile sensor acquires the vertical earthquake information on the lower side of the foundation pile, and based on the earthquake information, calculates the vertical displacement amount on the lower side of the foundation pile as the foundation pile vertical displacement amount. This foundation pile vertical displacement amount can be regarded as the vertical displacement amount of the superstructure caused by the earthquake shaking itself. Then, based on the vertical earthquake information of the superstructure, a provisional vertical displacement amount that is the provisional vertical displacement amount of the superstructure is calculated, and by subtracting the foundation pile vertical displacement amount as described above from the provisional vertical displacement amount, the vertical displacement amount of the superstructure caused by the earthquake shaking itself is excluded, and the vertical displacement amount of the superstructure caused by the damage to the foundation pile can be accurately calculated. Therefore, the degree of damage to the concrete foundation pile when an earthquake occurs can be determined with higher accuracy.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a system for estimating the degree of damage to a concrete foundation pile when an earthquake occurs, which can easily and simply estimate the degree of damage to the foundation pile.

Brief Description of the Drawings

[0013]

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Mode for Carrying Out the Invention

[0014] The present invention is a system for estimating the degree of damage to a concrete foundation pile from seismic information acquired by sensors installed in a structure. Specifically, in the system for estimating the degree of damage to a foundation pile, the vertical displacement amount of the superstructure is calculated from the vertical seismic information acquired by sensors installed in the superstructure, and the vertical displacement amount calculated from the curvature of the pile head of the foundation pile when the vertical displacement amount reaches the ultimate limit is set as a first threshold value. When the vertical displacement amount is equal to or greater than the first threshold value, it is estimated that the foundation pile has severe damage. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The schematic configuration of the system for estimating the degree of damage to a foundation pile in this embodiment is shown in FIG. 1. FIG. 2 is a diagram showing the schematic configuration of the structure provided with the system for estimating the degree of damage to the foundation pile of FIG. 1. As shown in FIG. 1, the system 1 for estimating the degree of damage to a foundation pile mainly includes an upper sensor 16, a sensor 17, an output unit 18, and a system main body 20 provided in the structure 10. The system 1 for estimating the degree of damage to a foundation pile estimates the degree of damage to the foundation pile 13 of the structure 10 after an earthquake occurs. As shown in FIG. 2, the structure 10 includes a foundation part 11 constructed in the ground G and a superstructure 12 supported on the foundation part 11. The foundation part 11 includes a plurality of foundation piles 13. Each foundation pile 13 extends vertically in the ground G. The foundation pile 13 supports the superstructure 12 of the structure 10. The foundation pile 13 is made of concrete, specifically, for example, reinforced concrete, and has concrete 13c and reinforcing bars 13s extending vertically and embedded in the concrete 13c. Therefore, the foundation pile 13 is a precast concrete pile including an RC pile, a PC pile, and a PHC pile constructed of concrete, or a cast-in-place concrete pile. The system 1 for estimating the degree of damage to a foundation pile estimates the degree of damage to such a concrete foundation pile 13.

[0015] The superstructure 12 has, for example, a plurality of layers in the vertical direction. The superstructure 12 is not limited by the number of layers or the structure (such as reinforced concrete structure, steel structure, steel-reinforced concrete structure, etc.). Also, it is not limited by the structural form, number of stories, or shape of the structure. However, the aspect ratio of the superstructure 12 (the ratio of the structure height to the structure width, the tower ratio) is effective because, for example, the larger it is, such as 4 or more, the more prominently the rocking vibration as described later occurs. Examples of such superstructures 12 with a relatively large aspect ratio include high-rise buildings, road bridges, iron towers, chimneys, wind turbines, etc.

[0016] The upper sensor 16 and the sensor 17 are provided on the superstructure 12 of the structure 10. The upper sensor 16 and the sensor 17 are, for example, accelerometers. The upper sensor 16 detects the horizontal acceleration generated in the superstructure 12 during an earthquake as horizontal earthquake information. The upper sensor 16 is, for example, arranged at the topmost part of the superstructure 12. The sensor 17 detects the vertical acceleration generated in the superstructure 12 as the vertical earthquake information of the superstructure 12. By arranging this sensor 17 at the lowermost part of the superstructure 12 (for example, the bottom surface of the foundation or near the bottom surface), the vertical acceleration generated in the foundation part 11 is detected. FIG. 3 is a plan view showing an example of the arrangement of sensors for detecting vertical acceleration in the superstructure shown in FIG. 2. FIG. 4 is a plan view showing another example of the arrangement of sensors for detecting vertical acceleration in the superstructure shown in FIG. 2.

[0017] As shown in FIG. 3, it is economically desirable to provide only one sensor 17 at the lowermost center position C in the plan view of the upper structure 12. As will be described later, when an earthquake occurs, rocking vibrations occur in the upper structure 12. Depending on the cross-sectional shape of the upper structure 12 and the like, this rocking vibration may occur so as to rotate about a position different from the center position C in the plan view. In such a case, for example, in advance, when a small-scale earthquake occurs, in a state where the foundation piles 13 are sound and undamaged, the position of the rotation center of the rocking vibration is investigated, and it is more preferable to provide the sensor 17 at the position of this rotation center. Hereinafter, when referring to the center position C, it shall indicate the position of the rotation center of the rocking vibration when there is no damage to the foundation piles 13. Alternatively, for example, when it is difficult to provide the sensor 17 at the center position C at the lowermost part of the upper structure 12, a plurality of sensors 17 may be arranged at the lowermost part of the upper structure 12 so as to surround the center position C as shown in FIG. 4, for example. In any case, the sensor 17 detects the vertical acceleration at the center position C. The output unit 18 outputs the detected horizontal detection data and the detected vertical acceleration data detected by the upper sensor 16 and the sensor 17 as horizontal earthquake information and vertical earthquake information.

[0018] The system main body 20 shown in FIG. 1 may be arranged inside the structure 10 or at a remote location outside the structure 10. The system main body 20 is connected to the output unit 18 via various communication cables and various wireless or wired networks. The system main body 20 estimates the degree of damage to the foundation piles 13 of the structure 10 based on the earthquake information transmitted from the structure 10. The system main body 20 includes an input unit 21, a vertical displacement amount calculation unit 22, a damage degree estimation unit 23, and an estimation result output unit 24. The input unit 21 receives the reception input of the vertical earthquake information output from the output unit 18 of the structure 10.

[0019] The vertical displacement calculation unit 22 calculates the vertical displacement of the superstructure 12 based on the vertical seismic information received by the input unit 21. Specifically, the vertical displacement calculation unit 22 calculates the vertical displacement of the superstructure 12 by double integrating the vertical seismic information. When a plurality of sensors 17 are provided as described with reference to FIG. 4, the vertical displacement calculation unit 22 calculates the vertical displacement at the position where each sensor 17 is provided for each of the vertical seismic information (vertical acceleration) detected by the plurality of sensors 17. Then, the vertical displacement calculation unit 22 calculates the weighted average based on the weights set based on the distances from the center position C of the corresponding sensor 17 with respect to the vertical displacements at the positions where each of the plurality of sensors 17 is provided, thereby calculating the vertical displacement of the superstructure 12.

[0020] The damage degree estimation unit 23 estimates the degree of damage to the foundation pile 13 based on the vertical displacement of the superstructure 12 calculated as described above. The processing of the damage degree estimation unit 23 will be described in detail later. The estimation result output unit 24 outputs to the outside the estimation result in the damage degree estimation unit 23, that is, information indicating the degree of damage to the foundation pile 13. The estimation result output unit 24 may cause information indicating the estimation result to be displayed, for example, on a monitor (not shown) provided in the system main body 20. The estimation result output unit 24 may transmit information indicating the estimation result to the user's terminal via an external wired or wireless network.

[0021] FIG. 5 is a schematic diagram showing a state in which rocking vibration occurs in the superstructure. In this embodiment, the aspect ratio of the superstructure 12 is large. Therefore, as shown in FIG. 5, in the superstructure 12, when an earthquake occurs, a rocking vibration occurs in which the upper part swings left and right and tilts and rotates about the vicinity of the lowermost part of the superstructure 12 near the ground G. In FIG. 5, a state is shown in which the superstructure 12 rotates clockwise and tilts toward the right side. In this state, a compressive axial force Fp acts on the foundation pile 13 on the right side of the drawing located in the forward rotation direction Rf of the rocking vibration R so as to push the foundation pile, and a tensile axial force Fq acts on the foundation pile on the left side of the drawing located in the backward rotation direction Rb so as to pull out the foundation pile. As shown in FIG. 5, for example, the superstructure 12 rotates clockwise, tilts toward the right side, then rotates counterclockwise and tilts toward the left side, and then rotates clockwise again to return to the current position. The superstructure 12 repeats the rocking vibration with this as one cycle (one round trip). In the following, the state of tilting toward the right side as shown in FIG. 5 will be described. However, in the state of tilting toward the left side, only the left and right are reversed compared to the state of tilting toward the right side, and the same explanation is possible. That is, in this case, a tensile axial force Fq acts on the foundation pile 13 on the right side of the drawing, and a compressive axial force Fp acts on the foundation pile on the left side of the drawing. In the state of tilting toward the right side as shown in FIG. 5, if there is no damage to the foundation pile 13 and the tensile axial force Fq does not exceed the frictional force generated between the outer peripheral surface of the foundation pile 13 and the ground G, it is considered that the difference in the resistance force generated between the foundation pile 13 on which the compressive axial force Fp acts and the foundation pile 13 on which the tensile axial force Fq acts is small. Therefore, when there is no damage to the foundation pile 13, the center of the rocking vibration is the center position C, that is, near the center of the lowermost part (bottom surface) of the superstructure 12.

[0022] FIG. 6 is a schematic diagram showing a state in which a rocking vibration occurs in the superstructure with damage to the foundation pile. FIG. 7 is a schematic diagram showing a state in which a compressive axial force acts on the damaged foundation pile. FIG. 8 is a schematic diagram showing a state in which a tensile axial force acts on the damaged foundation pile. As shown in FIG. 6, when the foundation pile 13 is damaged during an earthquake, a compressive axial force Fp acts on the foundation pile 13 in the forward rotation direction Rf of the rocking vibration R. Then, even if the foundation pile 13 is damaged, as shown in FIG. 7, at the damaged part 13k, both the concrete 13c and the reinforcing bars 13s resist the compressive axial force Fp. On the other hand, as shown in FIG. 6, a tensile axial force Fq acts on the damaged foundation pile 13 in the backward rotation direction Rb of the rocking vibration. Then, as shown in FIG. 8, at the damaged part 13k, only the reinforcing bars 13s can resist the tensile axial force Fq, and the reinforcing bars 13s elongate. For this reason, between the foundation pile 13 on which the compressive axial force Fp acts in the forward rotation direction Rf of the rocking vibration R and the foundation pile 13 on which the tensile axial force Fq acts in the backward rotation direction Rb of the rocking vibration R, the axial rigidity of the foundation pile 13 on which the tensile axial force Fq acts is smaller. Thereby, in the foundation pile 13 on which the tensile axial force Fq acts, it becomes easier to deform so as to elongate.

[0023] In this way, when the rocking vibration R occurs in a state where the foundation pile 13 is damaged, the foundation pile 13 on which the tensile axial force Fq acts elongates, causing the superstructure 12 to temporarily rise. The upward movement of the superstructure 12 occurs in conjunction with the rocking vibration R, resulting in the generation of vertical acceleration in the superstructure 12. Here, since the foundation pile 13 on which the tensile axial force Fq acts cannot sufficiently resist the tensile axial force Fq and elongates, as shown in FIG. 6, the rotation center Cr of the rocking vibration R in a state where the foundation pile 13 is damaged is a position closer to the foundation pile 13 on which the compressive axial force Fp acts in the forward rotation direction Rf of the rocking vibration R than the center position C.

[0024] Thus, when damage occurs to the foundation pile 13, the position of the rotation center Cr of the rocking vibration R is shifted from the rotation center, i.e., the center position C, when there is no damage to the foundation pile 13, to the side of the foundation pile 13 where the compressive axial force Fp acts. In the rocking vibration R, since the superstructure 12 swings left and right on the plane of the paper in FIG. 6, the position of the rotation center Cr of the rocking vibration R is shifted to the right when the superstructure 12 tilts to the right and to the left when the superstructure 12 tilts to the left from the center position C. Therefore, every time the superstructure 12 tilts left and right, the position of the center position C moves in the vertical direction. In this way, dynamic vertical displacement occurs in the superstructure 12.

[0025] FIG. 9 is a schematic diagram showing a state in which an inertial force acts on the superstructure. In a situation where horizontal vibration due to an earthquake as described above occurs, due to the inertial force IF of the superstructure 12, the superstructure 12 swings left and right, and thus the pile head 13t is in a state of being bent and deformed. Therefore, in a structure where rocking vibration occurs due to an earthquake, horizontal vibration also occurs simultaneously, and damage due to bending deformation occurs to the pile head 13t. FIG. 10 is a diagram showing a state in which a damaged foundation pile is bent and deformed. As shown in FIG. 9, when an inertial force occurs, bending deformation occurs in the pile head 13t of the foundation pile 13. For example, in some of the foundation piles 13, as shown in FIG. 10, on one surface 13g side in the horizontal direction of the foundation pile 13, the tensile strain becomes extremely larger than that on the other surface 13f side, and tensile deformation can occur in the material axis direction of the foundation pile 13 with respect to the bending deformation. Even in such a case, vertical displacement of the superstructure 12 can occur. The sensor 17 provided to detect the vertical acceleration of the center position C detects the vertical acceleration in order to observe the vertical displacement amount, which is the above-described vertical displacement.

[0026] Thus, the damage to the foundation pile 13 is related to the bending deformation in the pile head 13t of the foundation pile 13. Therefore, attention is paid to the pile head curvature, which is the curvature of the pile head 13t of the foundation pile 13. FIG. 11 is an explanatory diagram regarding the pile head curvature. When the foundation pile 13 undergoes bending deformation, when the foundation pile 13 is viewed in cross-section, tensile force is generated on one surface 13g of the concrete 13c of the foundation pile 13, and compressive force is generated on the other surface 13f. In the cross-section of the foundation pile 13, the strain distribution is as shown on the right side of Fig. 11. In this case, the pile head curvature is expressed by the following formula. Pile head curvature = (compressive edge strain - tensile edge strain) / diameter In the above formula, the pile head curvature is expressed based on the strains on the surfaces 13f and 13g of the foundation pile 13. However, based on the strains at the respective positions of the reinforcing bar 13s1 on the side where the tensile force acts and the reinforcing bar 13s2 on the side where the compressive force acts, the pile head curvature may also be expressed as follows. Pile head curvature = (compressive reinforcement strain - tensile reinforcement strain) / distance between main reinforcements

[0027] Fig. 12 is a diagram showing an example of ground motion, the overturning moment at the bottom of the foundation when the ground motion acts on the structure, the pile head curvature of the foundation pile, and the vertical displacement at the center position of the bottom of the foundation. As shown in Fig. 12, the ground motion gradually increases from the start of shaking, and accordingly, the overturning moment also gradually increases. In contrast, the pile head curvature remains small until the ground motion reaches a certain magnitude. When the ground motion becomes larger than a certain level, the reinforcing bar 13s yields, and it increases rapidly. After that, when the ground motion becomes even larger, the pile head curvature further increases significantly, and the foundation pile 13 has reached the ultimate limit. Regarding the vertical displacement, as the seismic motion increases, due to the damage of the foundation pile 13, the superstructure 12 tends to gradually sink. At the timing when the curvature of the pile head increases, upward displacement occurs. The amount of displacement in this upward displacement is linked to the increase in the curvature of the pile head. When there is a significant increase in the curvature of the pile head, the vertical displacement also increases significantly. With respect to the increase in the overturning moment, since the curvature of the pile head and the vertical displacement increase rapidly after the damage of the foundation pile 13, if the vertical displacement does not increase as the overturning moment increases, it can be determined that there is no damage to the foundation pile 13. If the vertical displacement increases as the overturning moment increases, it can be determined that there is damage to the foundation pile 13. Also, by observing the magnitude of the vertical displacement, the curvature of the pile head can be indirectly evaluated, and the degree of damage to the pile head portion 13t of the foundation pile 13 can be estimated.

[0028] To confirm the above considerations, experiments and analyses were conducted. Fig. 13 is an explanatory diagram of the experimental model used in the experiment. Fig. 14 is a diagram showing the input seismic motion in the experiment and the analysis. As the experimental model, a model was prepared in which sand was placed in a shear soil tank and a reinforced concrete pile model and a steel pipe pile model were respectively installed. This was vibrated with the seismic motion shown in Fig. 14. Furthermore, based on the above model, a simulation analysis using the three-dimensional finite element method was carried out under seismic motion. As a result of the vibration, damage occurred to the reinforced concrete pile model, but the steel pipe pile model maintained the elastic range and remained in a sound state.

[0029] Fig. 15 is a diagram showing the overturning moment at the bottom (bottom surface) of the structure model obtained by the above experiment and analysis. Fig. 16 is a diagram showing the vertical displacement at the bottom (bottom surface) of the structure model obtained by the above experiment and analysis. In Figs. 15 and 16, the results from the experiment and the analysis are extracted for the time period from 10 to 25 seconds. In Figs. 15 and 16, the experimental results are shown by dashed lines and the analysis results are shown by solid lines. In Fig. 16, the results of the analysis under the condition that no damage occurs to the foundation pile are also shown. First, in terms of the overturning moment, it can be confirmed that the results from experiments and analysis are generally in agreement. Also, regarding the vertical displacement, in both the experiment and the analysis considering the damage of the piles, the structural model shows a tendency to gradually sink, and dynamic upward displacement occurs in conjunction with the occurrence of the overturning moment.

[0030] Figure 17 is a graph showing the relationship between the peak value of the absolute value of the overturning moment and the vertical displacement obtained from the above experiment. Figure 18 is a graph showing the relationship between the peak value of the absolute value of the overturning moment and the vertical displacement obtained from the above analysis. In Figures 17 and 18, the results at 12.75 seconds when the steel bars 13s of the foundation pile 13 first yielded and at 13.67 seconds when the foundation pile 13 first reached the ultimate limit are indicated by squares. Also, the results from 10 seconds to 12.5 seconds are indicated by black circles, and the results after 12.5 seconds are indicated by white circles. Before the steel bars 13s yield and damage occurs to the foundation pile 13, that is, between 10 seconds and 12.5 seconds, even when the overturning moment increases, the vertical displacement is maintained at an equivalent value. On the other hand, after the steel bars 13s yield and damage occurs to the foundation pile 13, when the overturning moment increases, the vertical displacement also increases accordingly. From the above, it can be seen that by observing the tendency of the increase in vertical displacement accompanying the increase in the overturning moment, it is possible to determine whether damage has occurred to the foundation pile 13. Also, it can be seen that by observing the vertical displacement, it is possible to estimate the degree of damage to the foundation pile 13.

[0031] Next, the threshold value of the vertical displacement amount for estimating the degree of damage to the foundation pile 13 will be described. Here, first, the threshold value for estimating that the foundation pile 13 has reached the ultimate limit will be examined. FIG. 19 is a graph showing the relationship between the vertical displacement amount and the value obtained by dividing the head curvature by the head curvature at the time when the (compression edge of the concrete 13c of the) foundation pile reached the ultimate limit in the above experiment. In FIG. 19, the results of the round marks shown as pile 1 correspond to the case where the foundation pile shown as pile 1 in FIG. 13 was subjected to pulling out, and the results of the diamond marks shown as pile 5 correspond to the case where the foundation pile shown as pile 5 in FIG. 13 was subjected to pulling out. As shown in FIG. 19, it can be seen that there is a strong positive correlation between the value φ / φu obtained by dividing the head curvature φ by the ultimate curvature φu which is the head curvature when the foundation pile 13 reaches the ultimate limit, and the vertical displacement amount. For example, when this value φ / φu becomes 1, since it corresponds to the case where the curvature of the head portion 13t of the foundation pile 13 coincides with the curvature of the head portion 13t of the foundation pile 13 when the compression edge of the concrete 13c reaches the ultimate limit, it can be considered that the foundation pile 13 has reached the ultimate limit. Therefore, the vertical displacement amount of the superstructure 12 corresponding to the case where the curvature of the head portion 13t of the foundation pile 13 at the time of an earthquake coincides with the curvature of the head portion 13t of the foundation pile 13 when the ultimate limit is reached (that is, when the value φ / φu becomes 1) is set as the first threshold value, and when the vertical displacement amount becomes equal to or greater than the first threshold value, it can be estimated that the compression edge of the concrete 13c has reached the ultimate limit and the foundation pile 13 is in a state of severe damage. For example, in the case of FIG. 19, the first threshold value can be, for example, 0.5 mm.

[0032] Next, the threshold for estimating that the reinforcing bars 13s of the foundation pile 13 have yielded will be considered. FIG. 20 is a graph showing the relationship between the vertical displacement amount and the value obtained by dividing the pile head curvature by the pile head curvature at the time when the reinforcing bars of the foundation pile yielded in the above experiment. Also in FIG. 20, as in FIG. 19, the results of the round marks shown as pile 1 correspond to the case where the foundation pile shown as pile 1 in FIG. 13 is subjected to pull-out, and the results of the diamond marks shown as pile 5 correspond to the case where the foundation pile shown as pile 5 in FIG. 13 is subjected to pull-out. As shown in FIG. 20, it can be seen that there is a strong positive correlation between the value φ / φy obtained by dividing the pile head curvature φ by the ultimate curvature φy which is the pile head curvature when the reinforcing bars 13s of the foundation pile 13 yield, and the vertical displacement amount. For example, when this value φ / φy becomes 1, since the curvature of the pile head portion 13t of the foundation pile 13 corresponds to the case where it coincides with the curvature of the pile head portion 13t of the foundation pile 13 when the reinforcing bars 13s yield, it can be considered that the reinforcing bars 13s of the foundation pile 13 have yielded. Therefore, the vertical displacement amount of the superstructure 12 corresponding to the case where the curvature of the pile head portion 13t of the foundation pile 13 at the time of an earthquake coincides with the curvature of the pile head portion 13t of the foundation pile 13 when the reinforcing bars 13s yield (that is, when the value φ / φy becomes 1) is set as the second threshold value, and when the vertical displacement amount becomes equal to or greater than the second threshold value, it can be estimated that the reinforcing bars 13s have yielded and the foundation pile 13 is in a state with minor damage. The reinforcing bars 13s basically yield before the foundation pile 13 reaches the ultimate limit. Therefore, the second threshold value can be smaller than the first threshold value. For example, in the case of FIG. 20, the second threshold value can be set to 0.1 mm, for example.

[0033] In this way, the vertical displacement amount of the superstructure 12 corresponding to the case where the curvature of the pile head portion 13t of the foundation pile 13 at the time of an earthquake coincides with the curvature of the pile head portion 13t of the foundation pile 13 when it reaches the ultimate limit is set as the first threshold value. Also, the vertical displacement amount of the superstructure 12 corresponding to the case where the curvature of the pile head portion 13t of the foundation pile 13 coincides with the curvature of the pile head portion 13t of the foundation pile 13 when the reinforcing bars 13s yield is set as the second threshold value. Then, when the vertical displacement amount of the superstructure 12 is equal to or greater than the first threshold value, the damage degree estimation unit 23 estimates that the ultimate limit has been reached and the foundation pile 13 is in a state of severe damage. When the vertical displacement amount of the superstructure 12 is equal to or greater than the second threshold value and smaller than the first threshold value, the damage degree estimation unit 23 estimates that there may be minor damage to the foundation pile 13. Note that, as shown in FIGS. 19 and 20, the relationships among the vertical displacement amount, the value φ / φu, and the value φ / φy vary depending on the specifications of the foundation pile 13 and the scale of the structure 10. Therefore, it is desirable to obtain these relationships in advance through analysis or the like and derive the first threshold value and the second threshold value in advance.

[0034] Next, with reference to FIGS. 1 to 20 and FIG. 21, a method for estimating the degree of damage using the above-described foundation pile damage degree estimation system 1 will be described. FIG. 21 is a flowchart of the method for estimating the degree of damage. The method for estimating the degree of damage includes a step S1 of detecting vertical acceleration, a step S2 of receiving seismic information detected by a sensor, a step S3 of calculating the vertical displacement amount of the superstructure, a step S4 of estimating the presence or absence of damage to the foundation pile, and a step S5 of estimating the degree of damage to the foundation pile. First, at the time of an earthquake, the upper sensors 16 and 17 detect the horizontal acceleration and vertical acceleration generated in the superstructure 12 as seismic information (step S1). The horizontal acceleration and vertical acceleration detected by the upper sensors 16 and 17 are output to the system main body 20 by the output unit 18. The seismic information (horizontal acceleration, vertical acceleration) detected by the upper sensors 16 and 17 and output from the output unit 18 is received by the input unit 21 of the system main body 20 (step S2).

[0035] Based on the vertical seismic information received by the input unit 21, the vertical displacement amount calculation unit 22 calculates the vertical displacement amount of the superstructure 12 (step S3). Specifically, the vertical displacement amount calculation unit 22 calculates the vertical displacement amount of the superstructure 12 by double-integrating the vertical seismic information.

[0036] Next, the damage degree estimation unit 23 determines the presence or absence of damage to the foundation pile 13 (step S4). For this purpose, the damage degree estimation unit 23 first calculates the overturning moment by multiplying the horizontal inertial force based on the horizontal acceleration detected by the upper sensor 16 by the distance from the lowermost part (bottom surface) of the foundation to the upper sensor 16. When the calculated overturning moment is equal to or greater than a certain magnitude, the damage degree estimation unit 23 compares the vertical displacement amount with a preset lower limit value and upper limit value. When the vertical displacement amount is equal to or greater than the lower limit value and equal to or less than the upper limit value, it is determined that there is no damage to the foundation pile 13. When the vertical displacement amount is smaller than the lower limit value or larger than the upper limit value, it is determined that there is damage to the foundation pile 13.

[0037] When it is determined that there is damage to the foundation pile 13, the damage degree estimation unit 23 estimates the degree of damage to the foundation pile 13 (step S5). Specifically, the vertical displacement amount of the superstructure 12 corresponding to the case where the curvature of the pile head 13t of the foundation pile 13 at the time of an earthquake reaches the ultimate limit is set in advance as the first threshold value. Also, the vertical displacement amount of the superstructure 12 corresponding to the case where the curvature of the pile head 13t of the foundation pile 13 when the reinforcing bar 13s yields is set in advance as the second threshold value. Furthermore, when the vertical displacement amount of the superstructure 12 is equal to or greater than the first threshold value, the damage degree estimation unit 23 estimates that the foundation pile 13 has reached the ultimate limit and is in a state of severe damage. When the vertical displacement amount of the superstructure 12 is equal to or greater than the second threshold value and smaller than the first threshold value, the damage degree estimation unit 23 estimates that there may be minor damage to the foundation pile 13. The estimation result output unit 24 outputs to the outside the estimation result in the damage degree estimation unit 23, that is, information indicating the degree of damage to the foundation pile 13.

[0038] The foundation pile damage degree estimation system 1 as described above is a damage degree estimation system 1 for estimating the degree of damage to the concrete foundation piles 13 that support the superstructure 12 of the structure 10. The system includes a sensor 17 installed in the superstructure 12 to acquire vertical seismic information of the superstructure 12, a vertical displacement calculation unit 22 that calculates the vertical displacement amount of the superstructure 12 from the vertical seismic information, and a damage degree estimation unit 23 that estimates the degree of damage to the foundation piles 13 based on the vertical displacement amount of the superstructure 12. When an earthquake occurs, especially in a structure 10 with a high aspect ratio of the superstructure 12 (the ratio of the structure height to the structure width, tower ratio), a rocking vibration occurs in which the upper part swings left and right, tilts, and rotates around the part near the ground due to the overturning moment caused by the inertial force of the superstructure 12. To resist this rocking vibration, a compressive axial force acts on the foundation pile 13 that supports the superstructure 12 and is located on the side where the superstructure 12 tilts, that is, in the direction of the progress of the sway. Also, a tensile axial force acts on the foundation pile 13 located on the opposite side to pull out the foundation pile 13. Here, in the concrete foundation pile 13, when the concrete 13c of the foundation pile 13 is damaged due to cracks, cross-sectional defects, etc., if the tensile axial force acting on the foundation pile 13 caused by the rocking vibration exceeds the axial force of the self-weight of the structure 10 that constantly acts on the foundation pile 13, or when a horizontal force acts on the foundation pile 13 and the pile head bends and deforms, resulting in a large strain of the foundation pile 13, the superstructure 12 temporarily lifts up with respect to the foundation pile 13. As a result, a vertical displacement occurs in the superstructure 12 in conjunction with the rocking vibration. The more severe the damage such as cracks and cross-sectional defects in the concrete 13c of the foundation pile 13, the less able the concrete 13c can resist the tensile axial force, and as a result, it is considered that the vertical displacement amount becomes larger. In contrast, in the configuration as described above, the vertical displacement amount of the superstructure 12, which is the vertical seismic information of the superstructure 12 acquired by the sensor 17 installed in the superstructure 12, is calculated, and based on this, the degree of damage to the foundation pile 13 is estimated. In this way, since the degree of damage to the foundation pile 13 is estimated based on the vertical displacement amount that is considered to increase as the damage to the foundation pile 13 becomes more severe, the degree of damage is appropriately estimated. In such a system for estimating the degree of damage to a foundation pile, basically, it is possible to achieve simply by installing the sensor 17 in the superstructure 12. Therefore, the installation is easy. Also, the degree of damage to the foundation pile 13 can be estimated by merely performing a certain calculation on the seismic information acquired by the sensor 17. Therefore, the degree of damage to the foundation pile 13 can be estimated easily and simply. In this way, it becomes possible to provide a system 1 for estimating the degree of damage to a foundation pile that can easily and simply estimate the degree of damage to the concrete foundation pile 13 when an earthquake occurs.

[0039] Further, the foundation pile 13 includes reinforcing bars 13s extending in the vertical direction and concrete 13c embedding the reinforcing bars 13s. When the curvature of the pile head 13t of the foundation pile 13 when an earthquake occurs coincides with the curvature of the pile head 13t of the foundation pile 13 when the ultimate limit is reached, the vertical displacement amount of the superstructure 12 corresponding thereto is set as the first threshold value. The damage degree estimation unit 23 estimates that when the vertical displacement amount of the superstructure 12 is equal to or greater than the first threshold value, the foundation pile 13 has reached the ultimate limit and is in a state of severe damage. When the vertical displacement amount of the superstructure 12 is equal to or greater than the second threshold value and less than the first threshold value, it is estimated that there may be minor damage to the foundation pile 13. As described above, in the process where an earthquake occurs and the superstructure 12 sways left and right, tilts, and rotates due to the overturning moment, causing damage to the pile head 13t of the foundation pile 13, it was found that there is a relationship between the degree of damage and the curvature of the pile head 13t. Specifically, the curvature of the pile head 13t is small until the ground motion reaches a certain magnitude. However, when the ground motion increases and the steel bar 13s, on which the tensile axial force of the foundation pile 13 acts, yields, the curvature increases rapidly. When an even larger ground motion acts, the portion of the concrete 13c, on which the compressive axial force of the foundation pile 13 acts, reaches the ultimate limit, and the curvature of the pile head 13t increases more significantly. According to the above configuration, by associating the curvature of the pile head 13t with the vertical displacement of the superstructure 12, the vertical displacement of the superstructure 12 corresponding to the case where the curvature of the pile head 13t of the foundation pile 13 at the time of an earthquake coincides with the curvature of the pile head 13t of the foundation pile 13 when the concrete 13c (compressive edge) reaches the ultimate limit is set as the first threshold value. Thereby, when the vertical displacement of the superstructure 12 is equal to or greater than the first threshold value, it can be estimated that the curvature of the pile head 13t has increased more significantly when the concrete 13c (compressive edge) has reached the ultimate limit, and the foundation pile 13 is in a state of severe damage. Also, the second threshold value is appropriately set to be smaller than the first threshold value, and it is also possible to estimate that there may be minor damage to the foundation pile 13 when the vertical displacement of the superstructure 12 is equal to or greater than the second threshold value and smaller than the first threshold value. By doing so, the degree of damage to the foundation pile 13 can be estimated in more detail.

[0040] In the above, the vertical displacement of the superstructure 12 was observed and related to the curvature of the pile head 13t of the foundation pile 13 to estimate the degree of damage to the foundation pile 13. Instead, it is also conceivable to estimate the degree of damage to the foundation pile 13 by directly measuring the curvature of the pile head 13t of the foundation pile 13 without observing the vertical displacement of the superstructure 12. However, in this case, it is necessary to directly attach measuring tools such as strain gauges and optical fibers to the surfaces 13f, 13g of the foundation pile 13 and the reinforcing bars 13s, which is actually difficult to achieve. On the other hand, in the foundation pile damage degree estimation system 1 as described above, it is not necessary to provide measuring tools on the surfaces 13f, 13g of the foundation pile 13 and the reinforcing bars 13s, so it is easy to implement.

[0041] (First Modification Example of the Embodiment) Note that the foundation pile damage degree estimation system 1 of the present invention is not limited to the above-described embodiment described with reference to the drawings, and various other modification examples can be considered within its technical scope. FIG. 22 is a diagram showing a schematic configuration of a structure provided with a foundation pile damage degree estimation system according to a modification example of the above embodiment. In this modification example, in addition to the configuration of the above embodiment, a foundation pile sensor 19 is provided. In an actual earthquake, not only horizontal shaking but also vertical shaking can occur simultaneously. In such a case, among the vertical displacements calculated from the vertical earthquake information of the superstructure 12 acquired by the sensor 17, the vertical displacement of the superstructure 12 caused by the earthquake shaking itself is also mixed. As a result, the vertical displacement of the superstructure 12 caused by the damage to the foundation pile 13 cannot be accurately extracted, and there is a possibility of an error in estimating the degree of damage to the foundation pile 13.

[0042] Regarding this, in this modification example, the vertical displacement of the superstructure 12 caused by the earthquake shaking itself is observed by the foundation pile sensor 19, and based on this, only the vertical displacement of the superstructure 12 caused by the damage to the foundation pile 13 is extracted from the vertical displacement of the superstructure 12 acquired by the sensor 17. As described in the above embodiment, damage to the foundation pile 13 can be mainly assumed to occur in the pile head portion 13t by bending deformation. Therefore, it is particularly desirable that the foundation pile sensor 19 be provided at a position below the pile head portion 13t so as to acquire vertical seismic information at a position below the possible damage on the lower side of the foundation pile 13. In this modified example, the foundation pile sensor 19 is provided, for example, at the lower end 13b of the foundation pile 13. The foundation pile sensor 19 may be provided at any position as long as it can acquire the vertical seismic information at the position below the foundation pile 13 when damage occurs in the pile head portion 13t. For example, the foundation pile sensor 19 may be provided at an intermediate portion in the vertical direction of the foundation pile 13 (for example, a position deeper than five times the pile diameter from the upper end of the foundation pile 13), and the vertical seismic information at the intermediate portion of the foundation pile 13 may be regarded as the vertical seismic information at the position below the foundation pile 13 and acquired.

[0043] In this case, based on the vertical seismic information on the lower side of the foundation pile 13, the vertical displacement amount calculation unit 22 calculates the vertical displacement amount on the lower side of the foundation pile 13 as the foundation pile vertical displacement amount, and based on the vertical seismic information of the superstructure 12, calculates the tentative vertical displacement amount, which is the tentative vertical displacement amount of the superstructure 12, and subtracts the foundation pile vertical displacement amount from the tentative vertical displacement amount to calculate the vertical displacement amount of the superstructure 12. In this case, specifically, the vertical displacement amount calculation unit 22 double-integrates the vertical acceleration detected by the sensor 17 to calculate the tentative vertical displacement amount (tentative vertical displacement amount) at the center position C of the foundation. Also, the vertical displacement amount calculation unit 22 double-integrates the vertical acceleration detected by the foundation pile sensor 19 to calculate the vertical displacement amount (foundation pile vertical displacement amount) on the lower side of the foundation pile 13. Then, the vertical displacement amount calculation unit 22 subtracts the foundation pile vertical displacement amount from the tentative vertical displacement amount to calculate the vertical displacement amount of the superstructure 12.

[0044] That is, the damage degree estimation system of this modified example further includes a foundation pile sensor 19 that acquires vertical earthquake information below the foundation pile 13. The vertical displacement calculation unit 22 calculates the vertical displacement amount below the foundation pile 13 as the foundation pile vertical displacement amount based on the vertical earthquake information below the foundation pile 13, calculates a tentative vertical displacement amount that is the vertical displacement amount of the superstructure 12 tentatively based on the vertical earthquake information of the superstructure 12, and subtracts the foundation pile vertical displacement amount from the tentative vertical displacement amount to calculate the vertical displacement amount of the superstructure 12. In an actual earthquake, not only horizontal shaking but also vertical shaking can occur simultaneously. In such a case, among the vertical displacement amounts calculated from the vertical earthquake information of the superstructure 12 acquired by the sensor 17, the vertical displacement amount of the superstructure 12 caused by the earthquake shaking itself is also mixed. As a result, the vertical displacement amount of the superstructure 12 caused by the damage of the foundation pile 13 cannot be accurately extracted, and there is a possibility that an error may occur in the estimation of the damage degree of the foundation pile 13. On the other hand, according to the above configuration, the foundation pile sensor 19 acquires the vertical earthquake information on the side of the foundation pile 13, and based on the earthquake information, calculates the vertical displacement amount below the foundation pile 13 as the foundation pile vertical displacement amount. This foundation pile vertical displacement amount can be regarded as the vertical displacement amount of the superstructure 12 caused by the earthquake shaking itself. Then, based on the vertical earthquake information of the superstructure 12, a tentative vertical displacement amount that is the vertical displacement amount of the superstructure 12 tentatively is calculated, and by subtracting the above-mentioned foundation pile vertical displacement amount from the tentative vertical displacement amount, the vertical displacement amount of the superstructure 12 caused by the earthquake shaking itself is excluded, and the vertical displacement amount of the superstructure 12 caused by the damage of the foundation pile 13 can be accurately calculated. Therefore, the degree of damage to the concrete foundation pile 13 when an earthquake occurs can be determined with higher accuracy.

[0045] (Second Modified Example of the Embodiment) In the above-described embodiment, the damage degree estimation unit 23 calculates the overturning moment, and when the overturning moment becomes equal to or greater than a certain magnitude, compares the vertical displacement amount with a previously set lower limit value and upper limit value to determine the presence or absence of damage to the foundation pile 13. When it is determined that the foundation pile 13 is damaged, the degree of damage to the foundation pile 13 is estimated. However, the present invention is not limited to this. For example, the damage degree estimation unit 23 may not execute the determination of the presence or absence of damage to the foundation pile 13. In this case, the damage degree estimation unit 23 only executes the estimation of the degree of damage to the foundation pile 13 by comparing the vertical displacement amount with a first threshold value and a second threshold value. In this case, since it is not necessary to calculate the overturning moment, it is not necessary to provide the upper sensor 16 at the uppermost part of the superstructure 12. Therefore, the foundation pile damage degree estimation system 1 can be realized more simply.

[0046] (Third Modification of the Embodiment) In the above-described embodiment, when the overturning moment becomes equal to or greater than a certain magnitude, the damage degree estimation unit 23 compares the vertical displacement amount with a previously set lower limit value and upper limit value. When the vertical displacement amount is equal to or greater than the lower limit value and equal to or less than the upper limit value, it is determined that there is no damage to the foundation pile 13. When the vertical displacement amount is smaller than the lower limit value or larger than the upper limit value, it is determined that the foundation pile 13 is damaged. However, the present invention is not limited to this. FIG. 23 is a graph showing the relationship between the overturning moment and the vertical displacement amount when an earthquake occurs in each of the state where there is no damage to the foundation pile and the state where there is damage. When seismic force acts on the foundation pile 13 in a damaged state, for example, a major earthquake occurs, causing damage to the foundation pile 13, and then aftershocks act on the damaged foundation pile 13. As shown in Fig. 23, it can be seen that when the foundation pile 13 is damaged and subjected to seismic force, the vertical displacement tends to be larger than when the foundation pile 13 is not damaged and subjected to seismic force. Therefore, when an earthquake of the same level as the aftershocks described above occurs, if the observation record is saved in advance and the vertical displacement when there is no damage is calculated, then when an earthquake occurs later, by calculating the vertical displacement and comparing it with the vertical displacement when there is no damage, it is also possible to determine whether the foundation pile 13 is damaged.

[0047] In addition to this, it is also possible to make selections from the configurations listed in the above embodiments and each modification example, or to appropriately modify them to other configurations.

Explanation of Reference Signs

[0048] 1 Damage degree estimation system for foundation pile 13t Pile head 10 Structure 17 Sensor 12 Superstructure 19 Foundation pile sensor 13 Foundation pile 22 Vertical displacement calculation unit 13c Concrete 23 Damage degree estimation unit 13s Steel bar

Claims

1. A damage degree estimation system for estimating the degree of damage to a concrete foundation pile that supports the superstructure of a structure, comprising: a sensor installed in the superstructure to obtain vertical seismic information of the superstructure; a vertical displacement amount calculation unit that calculates the vertical displacement amount of the superstructure from the vertical seismic information; a damage degree estimation unit that estimates the degree of damage to the foundation pile based on the vertical displacement amount of the superstructure; A damage degree estimation system for a foundation pile, characterized by comprising the above components.

2. The foundation pile includes reinforcing bars extending in the vertical direction and concrete for embedding the reinforcing bars. When the curvature of the pile head of the foundation pile at the time of an earthquake reaches the ultimate limit, the vertical displacement amount of the superstructure corresponding to the case where it coincides with the curvature of the pile head of the foundation pile is set as a first threshold value. The damage degree estimation unit: When the vertical displacement amount of the superstructure is equal to or greater than the first threshold value, it is estimated that the foundation pile has reached the ultimate limit and is in a state of severe damage; When the vertical displacement amount of the superstructure is equal to or greater than a second threshold value and smaller than the first threshold value, it is estimated that there may be minor damage to the foundation pile. The damage degree estimation system for a foundation pile according to Claim 1, characterized by the above.

3. The damage degree estimation system for a foundation pile according to Claim 1 or 2, further comprising a foundation pile sensor that obtains vertical seismic information on the lower side of the foundation pile. The vertical displacement amount calculation unit calculates the vertical displacement amount on the lower side of the foundation pile as the foundation pile vertical displacement amount based on the vertical seismic information on the lower side of the foundation pile, calculates a provisional vertical displacement amount that is the provisional vertical displacement amount of the superstructure based on the vertical seismic information of the superstructure, and subtracts the foundation pile vertical displacement amount from the provisional vertical displacement amount to calculate the vertical displacement amount of the superstructure. Characterized by the above. ​ ​

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