Foundation reinforcement methods and foundation reinforcement structures

Abstract

The present invention provides a foundation reinforcement method and foundation reinforcement structure that can simplify the structure while reducing the bending moment applied to the footing. [Solution] A foundation reinforcement method according to one embodiment reinforces a foundation having a pier 11 extending upward from the ground G and a footing 12 provided at the lower end of the pier 11 and embedded in the ground G. The foundation reinforcement method comprises the steps of excavating the ground G to expose the upper surface 12b of the footing 12, and constructing a reinforcing portion 20 on the exposed upper surface 12b of the footing 12, which protrudes from a part of the upper surface 12b of the footing 12 and the side surface 11b of the pier 11. The reinforcing portion 20 reduces the overhang length of the footing 12 and reduces the stress acting on the footing 12 from below.

Description

Technical Field

[0001] The present disclosure relates to a foundation reinforcement method and a foundation reinforcement structure.

Background Art

[0002] Patent Document 1 describes a reinforcement structure and a reinforcement method for reinforcing an existing pier provided on a foundation slab. The reinforcement structure includes concrete, main reinforcement bars, and anchor bars. The concrete is provided on the outer peripheral portion of the pier such that the bottom of the concrete widens outward with respect to its upper portion on the foundation slab. The reinforcement bars are arranged vertically in the concrete from the bottom to the upper portion of the concrete, and the lower end portions of the reinforcement bars are fixed within the bottom of the concrete.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a foundation having a pier and a footing provided at the lower end of the pier, the footing receives a bending moment due to the overhang of the footing from the pier. For example, when the weight of the superstructure of the pier is large, a large reaction force may be applied to the footing from below, and at this time, the footing receives a large bending moment.

[0005] Therefore, it is conceivable to perform thickening reinforcement on the upper surface of the footing. However, when performing thickening reinforcement on the upper surface of the footing, it becomes difficult to implement the thickening reinforcement when there is a road above the footing or the like. Therefore, it is required to reduce the bending moment applied to the footing while simplifying the structure.

[0006] The purpose of this disclosure is to provide a foundation reinforcement method and foundation reinforcement structure that can reduce the bending moment applied to the footing while simplifying the structure. [Means for solving the problem]

[0007] (1) The foundation reinforcement method relating to this disclosure reinforces a foundation having a pier extending upward from the ground and a footing provided at the lower end of the pier and embedded in the ground. The foundation reinforcement method comprises the steps of excavating the ground to expose the upper surface of the footing and constructing a reinforcing portion on the exposed upper surface of the footing, which protrudes from a part of the upper surface of the footing and from the side of the pier. The reinforcing portion reduces the overhang length of the footing and reduces the stress acting on the footing from below.

[0008] This foundation reinforcement method reinforces a foundation having a bridge pier and a footing that extends from the lower end of the bridge pier. The method involves excavating the ground to expose the upper surface of the footing. A reinforcing section is then constructed on the exposed upper surface of the footing, protruding from the upper surface and the side of the bridge pier. This reinforcing section reduces the stress acting on the footing from below by reducing its overhang length. Therefore, by reducing the overhang length of the footing, the bending moment acting on the footing from below can be reduced. Furthermore, because the reinforcing section protrudes from a part of the upper surface of the footing and the side of the bridge pier, the reinforcing section can be constructed even when there is a road above the footing. Thus, the bending moment acting on the footing can be reduced while simplifying the structure.

[0009] (2) In (1) above, the foundation may include a plurality of piles extending downward from the footing, and in the process of constructing the reinforcement, the reinforcement may be constructed such that it approaches the piles in a plan view. When the foundation includes a plurality of piles extending downward from the footing, it is assumed that the footing will receive reaction forces from the plurality of piles. Therefore, by constructing the reinforcement that approaches the piles in a plan view, the overhang length of the footing can be reduced, thereby reducing the bending moment acting on the footing.

[0010] (3) In (1) or (2) above, the foundation may include a plurality of piles extending downward from the footing, and in the process of constructing the reinforcement section, the reinforcement section may be constructed so as to be located above the pile centers of the piles. In this case, since the reinforcement section reaches vertically above the piles, the pile reaction force against the footing can be eliminated by constructing the reinforcement section up to the pile centers of the piles.

[0011] (4) The foundation reinforcement structure relating to this disclosure comprises a pier extending upward from the ground, a footing provided at the lower end of the pier and embedded in the ground, a plurality of piles extending downward from the footing, and reinforcing parts that protrude from the upper surface of the footing and the side surface of the pier and reduce the overhang length of the footing. The reinforcing parts are located above the pile centers of the piles.

[0012] This foundation reinforcement structure reinforces a foundation comprising a bridge pier, a footing extending from the lower part of the bridge pier, and multiple piles extending downward from the footing. The upper surface of the footing is provided with reinforcing sections that protrude from the upper surface and the side surface of the bridge pier. These reinforcing sections reduce the stress acting on the footing from below by reducing the overhang length of the footing. Therefore, similar to the foundation reinforcement method described above, reducing the overhang length of the footing reduces the bending moment acting on the footing from below. Furthermore, because the reinforcing sections are located above the pile centers, the pile reaction force on the footing can be eliminated. [Effects of the Invention]

[0013] According to this disclosure, the bending moment applied to the footing can be reduced while simplifying the structure. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 shows an elevated bridge equipped with a foundation reinforcement structure according to an embodiment of this model. [Figure 2] Figure 2 is a plan view showing the bridge piers and foundation reinforcement structure of the elevated bridge shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing an elevated bridge equipped with a foundation reinforcement structure according to the embodiment. [Figure 4] Figure 4 is a cross-sectional view showing an elevated bridge equipped with a modified foundation reinforcement structure. [Figure 5] Figure 5 is a flowchart showing an example of the steps of the foundation reinforcement method according to the embodiment. [Figure 6] Figure 6 is a cross-sectional view showing a modified foundation reinforcement structure different from that shown in Figure 4. [Figure 7] Figure 7 is a cross-sectional view showing a modified foundation reinforcement structure different from those in Figures 4 and 6. [Modes for carrying out the invention]

[0015] The following describes embodiments of the foundation reinforcement method and foundation reinforcement structure according to this disclosure with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant explanations are omitted as appropriate. For the sake of ease of understanding, some parts of the drawings may be simplified or exaggerated, and the dimensional ratios, etc., are not limited to those shown in the drawings.

[0016] Figure 1 is a perspective view showing an example of a structure equipped with the foundation reinforcement structure 10 according to this embodiment, namely an elevated bridge 1. Figure 2 is a plan view showing a part of the elevated bridge 1. As shown in Figures 1 and 2, for example, the foundation reinforcement structure 10 is a structure that reinforces the foundation of the elevated bridge 1. The foundation reinforcement structure 10 has a reinforcing section 20, and the foundation reinforcement structure 10 is reinforced by the reinforcing section 20. For example, the foundation reinforcement structure 10 is made of reinforced concrete.

[0017] FIG. 3 is a cross-sectional view showing the viaduct 1. As shown in FIGS. 1, 2, and 3, the foundation reinforcement structure 10 includes a pier 11 extending upward from the ground G, a footing 12 which is a base plate provided at the lower end of the pier 11, a plurality of piles 15 extending downward from the footing 12, an upper surface 12b of the footing 12, and a reinforcing portion 20 protruding from a side surface 11b of the pier 11. For example, the foundation of the viaduct 1 is a pile foundation having the pier 11, the footing 12, and the plurality of piles 15.

[0018] For example, in plan view, the pier 11 is rectangular. As an example, the length of the pier 11 in the bridge axis direction D1 is shorter than the length of the pier 11 in the direction D2 perpendicular to the bridge axis. The reinforcing portion 20 is provided on the side in the direction D2 perpendicular to the bridge axis of the pier 11. In plan view, the pier 11 and the reinforcing portion 20 are arranged along the direction D2 perpendicular to the bridge axis.

[0019] For example, the reinforcing portion 20 is rectangular (cuboid). The reinforcing portion 20 protrudes upward from a part of the upper surface 12b of the footing 12. In plan view, the sum of the area of the reinforcing portion 20 and the area of the pier 11 is smaller than the area of the footing 12. The sum of the length of the reinforcing portion 20 in the direction D2 perpendicular to the bridge axis and the length of the pier 11 in the direction D2 perpendicular to the bridge axis is smaller than the length of the footing 12 in the direction D2 perpendicular to the bridge axis.

[0020] In plan view, the reinforcing portion 20 and the pier 11 are within the range of the footing 12. For example, the foundation reinforcement structure 10 includes a plurality of reinforcing portions 20. For example, the reinforcing portions 20 are provided on both sides of the pier 11 in the direction D2 perpendicular to the bridge axis. Thereby, the reinforcing portion 20 reinforces both sides of the pier 11 in the footing 12 in the direction D2 perpendicular to the bridge axis.

[0021] The footing 12 is embedded in the ground G. The footing 12 protrudes from the lower end of the pier 11 in the direction of the bridge axis D1 and in the direction perpendicular to the bridge axis D2. The footing 12 has thickness in the vertical direction D3. The multiple piles 15 are arranged in a plan view along the direction of the bridge axis D1 and the direction perpendicular to the bridge axis D2, respectively. In a plan view, the multiple piles 15 are arranged in a grid pattern. As an example, the shape of the piles 15 in a plan view is circular. However, the shape of the piles 15 in a plan view does not have to be circular and is not particularly limited.

[0022] For example, the reinforcing section 20 is made of reinforced concrete. The reinforcing section 20 is provided to reduce the overhang length of the footing 12. In a foundation having a pier 11 and a footing 12 provided at the lower end of the pier 11, the footing 12 is subjected to a bending moment because it overhangs from the pier 11. The magnitude of the bending moment experienced by the footing 12 is correlated with the overhang length of the footing 12.

[0023] In this embodiment, the overhang length of the footing 12 is reduced by providing a reinforcing portion 20 on the upper surface 12b of the footing 12 and on the side surface 11b of the pier 11 in a plan view. More specifically, the overhang length of the footing 12 is reduced from a first overhang length L1, which is the overhang length from the pier 11, to a second overhang length L2, which is the overhang length from the reinforcing portion 20.

[0024] The reinforcing portion 20 is provided to increase the thickness of the side surface 11b of the pier 11. This reinforces the footing 12 and reduces the stress acting on the footing 12. The reinforcing portion 20 reduces the stress acting on the footing 12 from below. In this embodiment, the overhang length of the footing 12 in the direction perpendicular to the bridge axis D2 is reduced, thereby reducing the bending moment acting on the portion of the footing 12 that overhangs in the direction perpendicular to the bridge axis D2.

[0025] The reinforcing section 20 is located above (vertically above) the pile center 15b of the pile 15. The placement of the reinforcing section 20 in this manner changes the position of the verification cross-section of the footing 12. In this embodiment, the verification cross-section is the cross-section that exhibits the greatest bending in the design calculations and is selected to determine the reinforcement of the foundation. For example, the verification cross-section of the foundation changes from a first verification cross-section M1 extending along the side surface 11b of the pier 11 to a second verification cross-section M2 extending along the outer surface 21 of the reinforcing section 20.

[0026] The bridge pier 11 has an overhang 13 at its upper end. The overhang 13 extends outwards on both sides in the direction D2 perpendicular to the bridge axis at the upper end of the bridge pier 11. For example, the superstructure of the elevated bridge 1 comprises a plurality of bridge girders 2 placed on the upper surface of the overhang 13, a deck slab 3 placed on the plurality of bridge girders 2, a pair of wall parapets 4 extending upward from both ends of the deck slab 3 in the direction D2 perpendicular to the bridge axis, asphalt 5, and lateral bracing 6.

[0027] Multiple bridge girders 2 extend in the bridge axis direction D1, and for example, multiple lateral braces 6 extend diagonally between two bridge girders 2 with respect to the bridge axis direction D1 and the direction perpendicular to the bridge axis D2. The above describes an example of the superstructure of the elevated bridge 1. However, the structure of the superstructure of the elevated bridge 1 is not limited to the above example and can be modified as appropriate.

[0028] For example, the reinforcing section 20 extends upward from a portion of the upper surface 12b of the footing 12 and reaches the cantilevered section 13 of the pier 11. In this case, reinforcement can be provided to accommodate the increased load on the superstructure of the elevated bridge 1. However, as shown in Figure 4, a reinforcing section 20A that does not reach the cantilevered section 13 may also be constructed. The reinforcing section 20A is identical to the reinforcing section 20 except for its shape.

[0029] In other words, the foundation reinforcement structure 10A of the elevated bridge 1A includes a reinforcing section 20 that extends upward from a part of the upper surface 12b of the footing 12 to a middle section of the pier 11. The reinforcing section 20A is trapezoidal in side view. For example, the width of the reinforcing section 20A decreases as it moves away from the upper surface 12b of the footing 12.

[0030] The foundation reinforcement method according to this embodiment reinforces a foundation having a bridge pier 11 and a footing 12. For example, the footing 12 may be reinforced after the foundation of the elevated bridge 1 has been constructed. Specifically, the footing 12 may be reinforced when the load on the superstructure of the elevated bridge 1 increases due to the widening of the superstructure of the elevated bridge 1.

[0031] For example, in pile foundations, a critical load may occur in the cross-section between the outermost pile 15 and the side surface 11b of the pier 11 during the design of the footing 12. The upward reaction force of the outermost pile 15 and the compressive force of the side surface 11b of the pier 11 are in opposition to each other, which can result in a large bending moment in that cross-section.

[0032] In such cases, reinforcement of the footing 12 is necessary, but since it is not possible to increase the amount of reinforcing steel in the footing 12, a method of increasing the thickness of the upper surface 12b of the footing 12 can be considered. However, this method may require increasing the thickness of the upper surface 12b of the footing 12 by several meters, which can lead to problems such as an unsightly appearance and increased weight.

[0033] In the foundation reinforcement method according to this embodiment, the footing 12 itself is not reinforced, but the stress acting on the footing 12 is reduced. This avoids the above-mentioned problems. Specifically, by constructing a reinforcing section 20 that extends upward from a part of the upper surface 12b of the footing 12, the overhang length of the footing 12 is reduced, thereby reducing the bending moment acting on the footing 12. This makes it possible to reduce the bending moment acting on the footing 12, and also reduces the tensile stress on the reinforcing bars embedded in the lower part of the foundation.

[0034] In the following, an example of a foundation reinforcement method according to this embodiment will be described with reference to Figure 5. Figure 5 is a flowchart showing an example of the steps of the foundation reinforcement method. In the following, a method for constructing a reinforcement section 20 on the foundation of the elevated bridge 1 will be described. First, the ground G is excavated to expose the upper surface 12b of the footing 12 (step S1, step of exposing the upper surface of the footing). At this time, a part of the upper surface 12b of the footing 12 is exposed. For example, only the part of the upper surface 12b that is less than or equal to a certain distance from the side surface 11b of the bridge pier 11 is exposed. The reinforcement section 20 is constructed on the exposed upper surface 12b.

[0035] Next, a reinforcing section 20 is constructed on the upper surface 12b of the exposed footing 12 (the process of constructing the reinforcing section). At this time, the reinforcing section 20 is constructed so that, in a plan view, it is close to the pile 15. More specifically, in a plan view, the reinforcing section 20 is constructed so that it is close to the pile 15 located below the overhang of the footing 12. For example, the reinforcing section 20 is constructed so that it is located above the pile center 15b of the pile 15.

[0036] At this time, a reinforcing section 20 is constructed that protrudes from a part of the upper surface 12b of the footing 12 and from the side surface 11b of the pier 11, thereby reducing the overhang length of the footing 12. For example, reinforcing bars are placed above the exposed portion of the upper surface 12b and opposite the side surface 11b of the pier 11 (reinforcing bar placement process, step S2).

[0037] Next, formwork is placed on the outside of the reinforcing bars, and concrete is poured into the formwork (concrete pouring process, step S3). After the concrete has hardened, the formwork is removed and backfilling is performed (backfilling process, step S4). After these steps are completed, the reinforced section 20 is finished, and the foundation reinforcement method is completed.

[0038] Next, the effects obtained from the foundation reinforcement method and foundation reinforcement structures 10 and 10A according to this embodiment will be described. The foundation reinforcement method according to this embodiment is a method for reinforcing a foundation having a bridge pier 11 and a footing 12 that extends from the lower part of the bridge pier 11, by excavating the ground G to expose a part of the upper surface 12b of the footing 12.

[0039] Then, a reinforcing section 20 is constructed on the exposed upper surface 12b of the footing 12, protruding from a portion of the upper surface 12b and from the side surface 11b of the pier 11. The reinforcing section 20 reduces the stress acting on the footing 12 from below by reducing the overhang length of the footing 12. Therefore, by reducing the overhang length of the footing 12, the bending moment acting on the footing 12 from below can be reduced.

[0040] Furthermore, because the reinforcing section 20 protrudes from a part of the upper surface 12b of the footing 12 and from the side surface 11b of the pier 11, the reinforcing section 20 can be constructed even when there is a road above the footing 12. Therefore, the bending moment acting on the footing 12 can be reduced while simplifying the structure.

[0041] In this embodiment, the foundation includes a plurality of piles 15 extending downward from the footing 12, and in the process of constructing the reinforcement section 20, the reinforcement section 20 is constructed so that, in a plan view, the reinforcement section 20 is close to the piles 15. When the foundation is a pile foundation including a plurality of piles 15 extending downward from the footing 12, it is assumed that the footing 12 will receive reaction forces from the plurality of piles 15. Therefore, by constructing the reinforcement section 20 that is close to the piles 15 in a plan view, the overhang length of the footing 12 is reduced, and thus the bending moment acting on the footing 12 can be reduced.

[0042] In this embodiment, in the process of constructing the reinforcing section 20, the reinforcing section 20 is constructed so that it is located above the pile center 15b of the pile 15. In this case, the reinforcing section 20 is constructed to reach the extension of the pile center 15b of the pile 15, and since the reinforcing section 20 is constructed up to the pile center of the pile 15, the pile reaction force on the footing 12 can be eliminated. The foundation reinforcement structure 10 has a reinforcing section 20, and the reinforcing section 20 reduces the stress acting on the footing 12 from below by reducing the overhang length of the footing 12. Therefore, the same effects as the foundation reinforcement method described above can be obtained from the foundation reinforcement structure 10.

[0043] Embodiments of the foundation reinforcement method and foundation reinforcement structure relating to this disclosure have been described above. However, the foundation reinforcement method and foundation reinforcement structure relating to this disclosure are not limited to the embodiments described above and may be modified within the scope of the gist described in the claims. That is, the content and sequence of steps of the foundation reinforcement method, as well as the shape, size, material, number and arrangement of each part of the foundation reinforcement structure, can be appropriately changed within the scope of the gist described above.

[0044] The following describes modified versions of the foundation reinforcement structure. The modified foundation reinforcement structure can be constructed by the same method as the foundation reinforcement method described herein. Figure 6 shows an elevated bridge 1B equipped with a foundation reinforcement structure 10B having a reinforcement section 20B according to the modified version. The reinforcement section 20B consists of a plurality of strut members extending from the upper surface 12b of the footing 12 to the side surface 11b of the pier 11.

[0045] Figure 7 shows an elevated bridge 1C equipped with a foundation reinforcement structure 10C having a reinforcing section 20C, which is a further modified example. The reinforcing section 20C is made of steel. For example, the reinforcing section 20C is an H-shaped steel and is H-shaped in plan view. By arranging multiple reinforcing sections 20C so as to surround the side surface 11b of the bridge pier 11, the same effect as the foundation reinforcement structure 10 described above can be obtained.

[0046] Furthermore, in the embodiment described above, the reinforcing portion 20 is provided on both sides of the pier 11 in the direction D2 perpendicular to the bridge axis, and an example was described in which the reinforcing portion 20 reinforces both sides of the pier 11 in the direction D2 perpendicular to the bridge axis in the footing 12. However, the reinforcing portion 20 may be provided on both sides of the pier 11 in the direction D1 in the bridge axis direction, or on only one side of the pier 11 in the direction D1 in the bridge axis direction or in the direction D2 perpendicular to the bridge axis. Moreover, the reinforcing portion 20 may be provided around the entire circumference of the pier 11 in a plan view. Thus, the direction in which the reinforcing portion 20 is provided with respect to the pier 11, and the direction in which the reinforcing portion 20 reinforces the pier 11, are not particularly limited.

[0047] In the embodiments described above, an example was described in which the reinforcing part 20 reinforces a pile foundation having a plurality of piles 15. However, the foundation to be reinforced by the reinforcing part 20 is not particularly limited and may be, for example, a raft foundation or a strip foundation.

[0048] In the embodiments described above, a foundation reinforcement structure 10 for an elevated bridge 1 was explained. However, the foundation reinforcement structure and foundation reinforcement method described herein may also be applied to the foundations of structures other than elevated bridges, and the type of structure to which the foundation reinforcement structure and foundation reinforcement method are applied is not particularly limited. [Explanation of Symbols]

[0049] 1,1A,1B,1C...elevated bridge, 2...bridge girder, 3...deck slab, 4...wall parapet, 5...asphalt, 6...lateral bracing, 10,10A,10B,10C...foundation reinforcement structure, 11...bridge pier, 11b...side view, 12...footing, 12b...top view, 13...cantilever section, 15...piles, 15b...piles center, 20,20A,20B,20C...reinforcement section, 21...outer surface, D1...bridge axis direction, D2...direction perpendicular to bridge axis, D3...vertical direction, G...ground, L1...first cantilever length, L2...second cantilever length, M1...first verification section, M2...second verification section.

Claims

1. A foundation reinforcement method for reinforcing a foundation having a bridge pier extending upward from the ground and a footing provided at the lower end of the bridge pier and embedded in the ground, The process of excavating the ground to expose the upper surface of the footing, The process involves constructing a reinforcing portion on the exposed upper surface of the footing, a portion of the upper surface of the footing, and a portion that protrudes from the side surface of the bridge pier. Equipped with, The reinforcing portion reduces the overhang length of the footing and reduces the stress acting on the footing from below. Foundation reinforcement methods.

2. The foundation includes a plurality of piles extending downward from the footing, In the process of constructing the reinforced portion, the reinforced portion is constructed such that, in a plan view, it approaches the pile. The foundation reinforcement method according to claim 1.

3. The foundation includes a plurality of piles extending downward from the footing, In the step of constructing the reinforcing portion, the reinforcing portion is constructed so that it is located above the center of the pile. The foundation reinforcement method according to claim 1 or claim 2.

4. Bridge piers extending upward from the ground, A footing provided at the lower end of the bridge pier and embedded in the ground, Multiple piles extending downward from the footing, A reinforcing portion that protrudes from the upper surface of the footing and the side surface of the bridge pier and reduces the overhang length of the footing, Equipped with, The reinforcing portion is located above the center of the pile. Foundation reinforcement structure.

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