Seismic isolation methods for existing buildings

Abstract

To provide a base-isolation method of an existing building which can prevent the settlement and shaking of the existing building, when removing part of an existing foundation and installing a base-isolation device.SOLUTION: A base-isolation method of an existing building includes: steps S1-S4 of installing a hydraulic jack 77 on a lower surface of a foundation beam 21 of an existing building 1, taking a reaction force to the foundation beam 21 by the hydraulic jack 77, and press-fitting a steel pipe pile 70 in the ground 2 immediately under the foundation beam 21; a step S5 of supporting the foundation beam 21 of the existing building 1 by the steel pipe pile 70, and connecting the steel pipe pile 70 and the foundation beam 21 with a connection material 73; steps S6-S8 of removing a footing 20 and constructing a lower part base-isolation foundation 40, and installing a base-isolation device 30 on the lower part base-isolation foundation 40; and steps S9, S10 of constructing an upper part base-isolation foundation 50 between the base-isolation device 30 and the foundation beam 21 of the existing building 1, and removing the connection material 73.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for seismically isolating an existing building by installing a new seismic isolation device directly under the foundation of the existing building. [Background technology]

[0002] Conventionally, methods have been proposed for seismically isolating existing buildings directly below their foundations (see Patent Documents 1 to 3). Patent Document 1 discloses a method for renovating pile foundations, which includes a pile driving process in which multiple temporary piles are arranged around the existing piles, an excavation process in which excavation is performed around the heads of the existing piles to form a work pit, a pile cutting process in which the weight of the superstructure is transferred to the temporary piles and the heads of the existing piles are cut off, and a seismic isolation process in which a seismic isolation device is inserted between the foundation slab and the existing pile and a newly installed pile head, the diameter of which decreases as it approaches the top, is formed directly below the seismic isolation device.

[0003] Patent Document 2 discloses a horizontal movement restraint method for restraining horizontal movement of an existing building when seismically isolating the existing building. This horizontal movement restraint method includes the steps of forming an excavation space, constructing a mat slab on the bottom surface of the excavation space, and providing temporary support columns on the mat slab and horizontal movement restraint members between the mat slab and the existing building to restrain the relative movement of the existing building with respect to the mat slab. Patent Document 3 shows a method of seismic isolation for existing buildings, in which excavation is performed beneath an existing building to expose the existing piles supporting the existing building, the existing piles are then buried inward to form a new foundation, and of the existing piles exposed between the top of the new foundation and the underside of the existing building, those that would be an obstacle to the installation of a seismic isolation device are cut and the device is attached, and then the remaining existing piles are cut. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-181322 A [Patent Document 2] JP 2016-11520 A [Patent Document 3] Japanese Patent Application Publication No. 9-125705 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for seismic isolation of an existing building that can prevent the existing building from sinking or shaking when part of the existing foundation is removed to install a seismic isolation device. [Means for solving the problem]

[0006] The inventors discovered that a method of seismic isolation for existing buildings can be achieved by pressing steel pipe piles into the ground directly below the existing foundation, and having the steel pipe piles support the vertical load of the existing building via a tensioning jig installed on the top of the steel pipe pile, while having the steel pipe piles support the horizontal load acting on the existing building via connecting materials (diagonal temporary materials) installed between the steel pipe piles and the existing foundation, thereby preventing the existing building from sinking or shaking, and thus arrived at the present invention. The method for seismic isolation of an existing building according to the first invention is a method for seismic isolation of an existing building by attaching a new seismic isolation device (e.g., seismic isolation device 30 described later) directly under the foundation (e.g., foundation beam 21 described later) of the existing building (e.g., existing building 1 described later), and includes a first step (e.g., steps S4, S11 to S14 described later) of placing a jack (e.g., hydraulic jack 77 described later) on the underside of the foundation of the existing building, applying a reaction force to the foundation with the jack, and pressing a steel pipe pile (e.g., steel pipe pile 70 described later) into the ground (e.g., ground 2 described later) directly under the foundation, and a second step (e.g., steps S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16, S17, S18, S19, S20, S21, S22, S23, S24, S25, S26, S27, S28, S29, S30, S31, S32, S33, S34, S35, S36, S37, S38, S39, S40, S41, S42, S43, S44, S45, S46, S47, S48, S49, S50, S51, S52, S53, S54, S55, S56, S57, S58, S59, S60, S61, S62, S63, S64, S65, S66, S67, S68, S69, S70, S71, S72, S73, S74, S75, S76, S77, S78, S80, S81, S The method includes a second step (e.g., steps S4 and S15 described below) of supporting the foundation and connecting the steel pipe pile and the foundation with connecting materials, a third step (e.g., steps S5 to S7 described below) of removing a part of the foundation (e.g., footing 20 described below) to construct a lower seismic isolation foundation (e.g., lower seismic isolation foundation 40 described below) and installing the seismic isolation device on the lower seismic isolation foundation, and a fourth step (e.g., steps S8 and S9 described below) of constructing an upper seismic isolation foundation (e.g., upper seismic isolation foundation 50 described below) between the seismic isolation device and the foundation of the existing building and removing the connecting materials.

[0007] According to this invention, a steel pipe pile is driven into the ground directly below the existing foundation by a jack while applying a reaction force to the existing foundation, and then a connecting material is installed between the steel pipe pile and the existing foundation to restrain the subsidence and horizontal movement of the existing foundation. Therefore, when removing a part of the existing foundation to install a seismic isolation device, the existing building is supported from below by the steel pipe pile, while the horizontal movement of the existing building is restrained by the connecting material and the steel pipe pile, so that the subsidence and shaking of the existing building can be prevented, and the seismic isolation device can be smoothly installed on the existing building. In addition, since the steel pipe pile is driven into the ground by a jack while applying a reaction force to the existing foundation, the steel pipe pile can be installed in a narrow working space.

[0008] The second invention is a method for seismic isolation of an existing building, characterized in that in the first step, a steel pipe pile is constructed by connecting a plurality of steel pipes (e.g., steel pipe 71 described below), and the steel pipe pile is pressed into place with the jack while adding more steel pipes.

[0009] According to this invention, the steel pipe pile is constructed by connecting multiple steel pipes, so when the steel pipe pile is pressed into the ground, if there is a space directly below the existing foundation in which one steel pipe can be placed vertically, the steel pipe can be pressed into the ground to construct the steel pipe pile. Therefore, since it is only necessary to partially excavate the ground at the installation location of the steel pipe pile in a tsubo digging style, the excavation process can be shortened and the excavation construction costs can be reduced.

[0010] The seismic isolation method for an existing building of the third invention is characterized in that in the first step, an opening (e.g., opening 63 described below) is provided in a floor slab (e.g., floor slab 62 described below) of the lowest floor of the existing building, and in the fourth step, the opening is sealed.

[0011] According to this invention, an opening is provided in the floor slab on the lowest floor of an existing building, so that when pressing in steel pipe piles, attaching connecting materials, constructing the seismic isolation foundation, and installing the seismic isolation device, construction materials can be brought in and taken out through the opening, and sufficient ventilation can be ensured through the opening, allowing the seismic isolation device to be installed safely and smoothly. Effect of the Invention

[0012] According to the present invention, a method for seismic isolation of an existing building can be provided, which can prevent the existing building from sinking or shaking when part of the existing foundation is removed to install a seismic isolation device. [Brief description of the drawings]

[0013] [Figure 1] 1 is a vertical cross-sectional view of an existing building to which a seismic isolation method for an existing building according to one embodiment of the present invention is applied. [Diagram 2] A vertical cross-sectional view of a seismic isolation device installed in an existing building. [Diagram 3] 1 is a flowchart of the procedure for seismically isolating an existing building. [Figure 4] This is an explanatory diagram of the procedure for seismically isolating an existing building (Part 1, after the floor slab and retaining wall have been demolished). [Diagram 5] This is an explanatory diagram of the procedure for seismically isolating an existing building (part 2, after the existing foundation beams have been reinforced). [Figure 6] This is an explanatory diagram of the procedure for seismically isolating an existing building (Part 3, with the foundation beams of the existing building supported by steel pipe piles). [Figure 7] FIG. 7 is a vertical cross-sectional view of a portion surrounded by dashed line A in FIG. 6 (the upper part of the steel pipe pile). [Figure 8] FIG. 8 is a cross-sectional view of FIG. 7 in accordance with II. [Figure 9] 1 is a flowchart of a procedure for installing a steel pipe pile. [Figure 10] FIG. 1 is an explanatory diagram of the procedure for installing a steel pipe pile (procedure for pressing in a steel pipe pile). [Figure 11] This is an explanatory diagram of the procedure for seismically isolating an existing building (part 4, after the footing has been removed and secondary excavation has been carried out). [Figure 12] This is an explanatory diagram of the procedure for seismically isolating an existing building (part 5, after the mat slab and lower seismic isolation foundation have been constructed and the seismic isolation device has been installed). [Figure 13] This is an explanatory diagram of the procedure for seismically isolating an existing building (part 6, after the upper seismic isolation foundation has been constructed). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention is a method for seismic isolation of an existing building by installing a new seismic isolation device directly under the foundation of the existing building. Specifically, in order to remove a part of the existing foundation and install the seismic isolation device, steel pipe piles are pressed into the ground directly under the existing foundation, and while the existing building is supported from below by the steel pipe piles, connecting materials extending diagonally to the horizontal are installed between the existing foundation and the steel pipe piles to suppress horizontal movement of the existing building. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a vertical cross-sectional view of an existing building 1 to which a seismic isolation method for an existing building according to one embodiment of the present invention is applied. The existing building 1 comprises a foundation 10 constructed on the ground 2, a first basement floor portion 11 constructed on the foundation 10, a retaining wall portion 12 provided along the periphery of the first basement floor portion 11, and a ground floor 13 constructed on the first basement floor portion 11. Before being seismically isolated, the foundation 10 of the existing building 1 includes footings 20 provided at predetermined intervals, foundation beams 21 that are lattice-shaped in plan view and connect the footings 20, and a dirt floor slab (foundation slab) 22 provided between the foundation beams 21. Columns 14 for the first basement floor are placed on the footings 20.

[0015] In this embodiment, a seismic isolation device 30 is installed directly under the foundation 10 of the above-mentioned existing building 1 to seismically isolate the existing building 1 (see FIG. 13). 2 is a vertical cross-sectional view of the seismic isolation device 30 installed in the existing building 1. A lower seismic isolation foundation 40 is constructed below the seismic isolation device 30, and an upper seismic isolation foundation 50 is constructed above the seismic isolation device 30. A lower base plate 41 is driven into the upper surface of the lower seismic isolation base 40. The lower base plate 41 has a plurality of female threads 42 arranged in an annular shape. An upper base plate 51 is driven into the lower surface of the upper seismic isolation base 50. The upper base plate 51 has a plurality of female threads 52 arranged in an annular shape.

[0016] The seismic isolation device 30 comprises a lower flange 31, a laminated rubber 32 provided on the lower flange 31, and an upper flange 33 provided on the laminated rubber 32. The laminated rubber 32 is made by alternately laminating rubber and steel plates, and is elastically deformable. The lower flange 31 is fixed to a female thread portion 42 of a lower base plate 41 of the lower seismic isolation foundation 40 with a bolt 34. The upper flange 33 is fixed to a female thread portion 52 of an upper base plate 51 of the upper seismic isolation foundation 50 with a bolt 35.

[0017] The procedure for seismically isolating the existing building 1 will be described below with reference to the flow chart of FIG. In step S1, as shown in Fig. 4, an earth retaining wall 60 is constructed on the outside of the retaining wall portion 12 of the existing building 1. Also, the interior of the first basement floor portion 11 is demolished. In step S2, as shown in Fig. 4, the floor slab 22 and the retaining wall portion 12 are demolished, and primary excavation is carried out. The floor level of this primary excavation is the beam bottom level of the foundation beams 21. In step S3, as shown in Fig. 5, the existing foundation beams 21 are reinforced with a reinforcing body 61, and a new floor slab 62 is constructed between the reinforced foundation beams 21. Specifically, the existing foundation beams 21 are reinforced by constructing the reinforcing body 61 on the side of the existing foundation beams 21. Also, an opening 63 is provided in the new floor slab 62 for carrying in and out construction materials and for ventilation. Around this opening 63, safety protection 64 is provided using single pipes, life ropes, etc.

[0018] In step S4, as shown in FIG. 6, the steel pipe pile 70 is press-fitted into the ground 2. The detailed structure of the steel pipe pile 70 will be described below. Fig. 7 is a vertical cross-sectional view of the portion (the upper part of the steel pipe pile 70) surrounded by the dashed line A in Fig. 6. Fig. 8 is a cross-sectional view taken along line II in Fig. 7. The steel pipe pile 70 is installed at approximately the center between the column spans in a plan view and directly below the foundation beam 21. The steel pipe pile 70 is configured by connecting a plurality of steel pipes 71 in the length direction. A tensioning jig 72 with an adjustable height h is interposed between the upper end surface of the steel pipe pile 70 and the foundation beam 21. The vertical load of the existing building 1 is supported by the steel pipe pile 70 via this tensioning jig 72. Furthermore, four connecting members 73 extending obliquely relative to the horizontal are provided between the upper end side of the steel pipe pile 70 and the foundation beam 21. The four connecting members 73 extend in all four directions from the steel pipe pile 70 in a plan view. Post-installed anchors 74 are driven into the underside of the foundation beams 21, and mounting jigs 75 are bolted to the post-installed anchors 74. Meanwhile, a connecting plate 76 is provided on the upper end side of the steel pipe pile 70. The connecting member 73 is a pair of channel steels arranged back-to-back, and both ends of the connecting member 73 are bolted to the mounting jigs 75 attached to the underside of the foundation beams 21 and to the connecting plate 76 of the steel pipe pile 70. Through these connecting members 73, mounting jigs 75, and joint plates 76, the horizontal force acting on the existing building 1 during an earthquake is transmitted to the steel pipe pile 70.

[0019] The specific procedure of step S4 will be described below with reference to the flowchart of FIG. 10(a), in step S41, a pit is excavated at the installation location of the steel pipe pile 70, a first steel pipe 71A is placed on the ground 2, and a hydraulic jack 77 is placed between this first steel pipe 71A and the underside of the foundation beam 21 of the existing building 1. Note that the depth D from the underside of the foundation beam 21 to the ground surface by the pit excavation may be deep enough to place the steel pipe 71A vertically directly below the hydraulic jack 77. In step S42, as shown in FIG. 10(a), a hydraulic jack 77 applies a reaction force to the foundation beam 21, and the steel pipe 71A is pressed into the ground 2 of the foundation beam 21. In step S43, as shown in FIG. 10(b), a second steel pipe 71B is joined on top of the first steel pipe 71A pressed into the ground 2, and then the second steel pipe 71B is pressed into the ground 2 together with the first steel pipe 71A using a hydraulic jack 77. In step S44, the operation of step S43 is repeated.

[0020] Returning to the flowchart of FIG. 3, in step S5, as shown in FIG. 6, a tensioning jig 72 is installed between the foundation beam 21 of the existing building 1 and the steel pipe pile 70, and the existing building 1 is supported by the steel pipe pile 70. In addition, a connecting member 73 is installed between the foundation beam 21 of the existing building 1 and the steel pipe pile 70, and the horizontal movement of the existing building 1 is suppressed by the steel pipe pile 70. Specifically, the hydraulic jack 77 is removed and removed, and the tensioning jig 72 is interposed between the upper end surface of the steel pipe pile 70 and the foundation beam 21. After that, the height h of the tensioning jig 72 is adjusted to tension the tensioning jig 72 between the upper end surface of the steel pipe pile 70 and the foundation beam 21. In addition, a post-installed anchor 74 is installed on the lower surface of the foundation beam 21, and a mounting jig 75 is bolted to the post-installed anchor 74, and the joining plate 76 of the steel pipe pile 70 and the mounting jig 75 of the foundation beam 21 are connected by the connecting member 73.

[0021] In step S6, as shown in Fig. 11, the footing 20 is removed and secondary excavation is carried out. The floor level of this secondary excavation is the bottom level of a newly constructed mat slab 80 (see Fig. 12). 11 and 12, in step S7, a mat slab 80 and a seismic isolation retaining wall portion 81 are constructed, and the lower seismic isolation foundation 40 is constructed on the mat slab 80. Specifically, the lower seismic isolation foundation 40 is constructed at the position where the footing 20 of the existing building 1 is provided. As a result, the post-seismic isolation foundation 10 is configured to include the reinforced foundation beams 21, the new earthen floor slab 62, and the mat slab 80.

[0022] In step S8, as shown in Figure 12, the seismic isolation device 30 is installed on the lower seismic isolation foundation 40, and a beam column 82 is interposed between the upper surface of the seismic isolation device 30 and the foundation of the existing building 1 (the intersection of the foundation beams 21 directly below the column) to introduce a preload to the seismic isolation device 30. In step S9, as shown in Fig. 13, an upper seismic isolation foundation 50 is constructed between the top surface of the seismic isolation device 30 and the foundation 10 of the existing building 1. The beam columns 82 are embedded in this upper seismic isolation foundation 50. In addition, the openings 63 provided in the earthen floor slab 62 are closed. In step S10, seismic isolation release (operating the seismic isolation device 30) is performed. Specifically, the tensioning jigs 72 and the connecting materials 73 are detached and removed, and the portions of the steel pipe piles 70 that protrude beyond the mat slab 80 are cut and removed.

[0023] To summarize the seismic isolation method for the existing building 1 described above, steps S1 to S4 correspond to the first step described in the claims, which involves placing a jack on the underside of the foundation of the existing building, using the jack to generate a reaction force against the foundation, and pressing a steel pipe pile into the ground directly below the foundation. Step S5 corresponds to the second step described in the claims, in which the second step supports the foundation of the existing building with steel pipe piles and connects the steel pipe piles and the foundation with connecting materials. Steps S6 to S8 correspond to a third step described in the claims, in which a part of the existing foundation is removed to construct a lower seismic isolation foundation, and a seismic isolation device is installed on the lower seismic isolation foundation. Steps S9 and S10 correspond to the fourth step described in the claims, which involves constructing an upper seismic isolation foundation between the seismic isolation device and the foundation of the existing building and removing the connecting material.

[0024] According to this embodiment, the following effects are obtained. (1) A hydraulic jack 77 is used to press a steel pipe pile 70 into the ground 2 directly below the existing foundation beam 21, applying a reaction force to the foundation beam 21, and then a connecting member 73 is installed between the steel pipe pile 70 and the foundation beam 21 to restrain settlement and horizontal movement of the existing foundation 10. Therefore, when part of the foundation 10 is removed to install the seismic isolation device 30, the existing building 1 is supported from below by the steel pipe pile 70, while the horizontal movement of the existing building 1 is restricted by the steel pipe pile 70 and the connecting member 73, thereby preventing settlement and shaking of the foundation 10, and the seismic isolation device 30 can be smoothly installed on the existing building 1. In addition, since the steel pipe pile 70 is pressed in by the hydraulic jack 77 while taking the reaction force from the existing foundation beam 21, the steel pipe pile 70 can be installed in a narrow working space.

[0025] (2) Since the steel pipe pile 70 is constructed by connecting a plurality of steel pipes 71, when the steel pipe pile 70 is pressed into the ground 2, all that is required is space for one steel pipe 71 to be arranged vertically directly below the foundation beam 21. Therefore, it is necessary to partially excavate only the ground at the installation location of the steel pipe pile 70 in a tsubo digging format. This shortens the excavation process and reduces the cost of excavation work. (3) Since an opening 63 is provided in the dirt floor slab 62, which is the floor slab of the lowest floor of the existing building 1, sufficient ventilation can be ensured through the opening 63 when pressing in the steel pipe piles 70, attaching the connecting materials 73, constructing the seismic isolation foundations 40, 50, and installing the seismic isolation device 30, so that the seismic isolation device 30 can be installed safely and smoothly.

[0026] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention. [Explanation of symbols]

[0027] 1... Existing building 2... Ground 10... Foundation 11... 1st basement floor 12... Retaining wall 13... Ground floor 14... Columns on each floor 20... Footing 21... Foundation beam 22... Earth floor slab 30... Seismic isolation device 31... Lower flange 32... Laminated rubber 33... Upper flange 34, 35…Volts 40...Lower seismic isolation foundation 41...Lower base plate 42...Female thread 50...Upper seismic isolation base 51...Upper base plate 52...Female thread 60... Retaining wall 61... Reinforcement structure 62... Earth floor slab 63... Opening 64... Safety curing 70... Steel pipe pile 71, 71A, 71B... Steel pipe 72... Tension jig 73... Connecting material 74... Post-installed anchor 75... Installation jig 76... Joint plate 77... Hydraulic jack 80...Mat slab 81...Seismic isolation retaining wall section 82...Column

Claims

1. A method for seismic isolation of an existing building by installing a new seismic isolation device directly under the foundation of the existing building, A first step of installing a jack on the underside of the foundation of the existing building, applying a reaction force to the foundation with the jack, and pressing a steel pipe pile into the ground directly below the foundation; A second step of supporting the foundation of the existing building with the steel pipe pile and connecting the steel pipe pile and the foundation with a connecting material; a third step of removing a portion of the foundation to construct a lower seismic isolation foundation and installing the seismic isolation device on the lower seismic isolation foundation; A method for seismic isolation of an existing building, comprising a fourth step of constructing an upper seismic isolation foundation between the seismic isolation device and the foundation of the existing building, and removing the connecting material.

2. The method for seismic isolation of an existing building as described in claim 1, characterized in that in the first step, a steel pipe pile is formed by connecting a plurality of steel pipes, and the steel pipe pile is pressed into the pile by the jack while adding more steel pipes.

3. In the first step, an opening is provided in a floor slab of the lowest floor of the existing building; 3. The method for seismic isolation of an existing building according to claim 1 or 2, wherein in the fourth step, the opening is blocked.

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