JP2012127118A - Method and structure for earthquake strengthening - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a structure for earthquake strengthening in which restraining a construction cost, shortening a construction period and improving aseismic capacity of a structure supported by the ground are possible.SOLUTION: In a method for earthquake strengthening an anchor 20 is fixed to both a new foundation 12 constructed in the ground 2 and a bearing layer 5 which is an anchor ground of the anchor 20. The anchor 20 is fixed to the new foundation 12 as well as the bearing layer 5 with its PC steel strand wires tightened by tensioning force T1 which is enough to keep the PC steel strand wires from going slack and smaller than design tensioning force T0 at a time of an earthquake.

Description

  The present invention relates to a seismic reinforcement method and structure.

  As a seismic reinforcement method for an existing building, a method is known in which an anchor is placed so that one end is fixed to the anchoring ground of the anchor and the other end is fixed to the foundation of the existing building (for example, see Patent Document 1). ). In this seismic reinforcement method for existing buildings, anchors are fixed to the fixing ground and the foundation in a state where tension is applied in advance, or are fixed to the fixing ground and the foundation in a state where tension is not applied.

JP 2008-223430 A

  In the above-mentioned seismic reinforcement method for existing buildings, when tension is given to the anchor in advance, the ground between the foundation and the fixed ground is required to have sufficient strength against vertical loads. For this reason, when the said ground is soft ground, the ground improvement is required, construction cost increased, and the construction period was prolonged. In addition, when initial tension is not applied to the anchor, the amount of extension of the anchor at the time of the occurrence of an earthquake becomes long, and the seismic performance decreases.

  The present invention has been made in view of the above circumstances, and provides a seismic reinforcement method and structure capable of suppressing construction costs, shortening the construction period, and improving the seismic performance of a structure built on the ground. It is an object to do.

  In order to solve the above-mentioned problem, the seismic reinforcement method according to the present invention is a seismic reinforcement method performed by fixing an anchor on a structure built on the ground and the anchoring ground of the anchor, The anchor is fixed to the structure body and the anchor in a state in which the tension material has a tension force that is large enough to prevent the tension material from loosening and is smaller than the design tension force when an earthquake occurs. It is characterized by being fixed to the ground.

  In the seismic reinforcement method, the portion of the tension member in the structure is configured to be stretchable, and the portion of the tension material on the fixing ground side with respect to the structure is configured so that expansion and contraction is restricted. Also good.

  In the seismic reinforcement method, the structure may be a foundation that supports a structure on the ground or a foundation that supports a seismic frame connected to the structure on the ground.

  In order to solve the above problems, the seismic reinforcement structure according to the present invention is an earthquake resistance reinforcement structure in which an anchor is fixed to a structure constructed on the ground and the anchoring ground of the anchor, and the tension of the anchor The anchor is attached to the structure and the fixing ground in a state in which a tension force of a magnitude that does not cause the tension material to loosen and a tension force smaller than a design tension force at the time of occurrence of an earthquake is applied to the anchor. It is characterized by being fixed to.

  In the seismic reinforcement structure, a portion of the tension member in the structure is configured to be stretchable and a portion of the tension material closer to the fixing ground than the structure is configured so that expansion and contraction is restricted. Also good.

  In the seismic reinforcement structure, the structure may be a foundation that supports a structure on the ground or a foundation that supports an earthquake-resistant frame connected to the structure on the ground.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to suppress construction cost and to shorten a construction period, the seismic performance of the structure built in the ground can be improved.

It is an elevational sectional view showing the earthquake-proof reinforcement structure of the existing building concerning one embodiment. It is an elevational sectional view showing an anchor. It is a figure for demonstrating the earthquake-proof reinforcement method of the existing building. It is a figure for demonstrating the earthquake-proof reinforcement method of the existing building. (A), (B) is a figure for demonstrating the earthquake-proof reinforcement method of the existing building. It is a figure for demonstrating the earthquake-proof reinforcement method of the existing building. (A), (B) is elevation sectional drawing for demonstrating the effect | action of the earthquake-proof reinforcement structure of the existing building. It is an elevational sectional view showing a seismic reinforcement structure of an existing building according to another embodiment. It is a perspective view which shows an earthquake-resistant frame. It is an elevational sectional view showing a seismic reinforcement structure of an existing building according to another embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an elevational sectional view showing a seismic reinforcement structure 10 of an existing building 1 according to an embodiment. As shown in the figure, an existing foundation 3 exists on the ground 2, and an existing building 1 to be subjected to seismic reinforcement is present on the existing foundation 3. In addition, a soft ground 4 exists in the upper layer of the ground 2, and a support layer (fixed ground) 5 exists in the lower layer of the soft ground 4.

  The seismic reinforcement structure 10 includes a new foundation 12 integrated with the existing foundation 3 and an anchor 20 having one end fixed to the support layer 5 and the other end fixed to the new foundation 12. Here, between the existing foundation 3 and the newly established foundation 12 and the support layer 5, ground-improved layers, piles, and the like are not provided, and reinforcement work for the soft ground 4 is not performed.

  FIG. 2 is an elevational sectional view showing the anchor 20. As shown in this figure, the anchor 20 includes a synthetic resin sheath tube 22, a plurality of PC steel strands 24 inserted through the sheath tube 22, and injection pipes 26 and 27 inserted through the sheath tube 22. A fixing mechanism 40 provided at the upper end of the anchor 20. The ground 2 is formed with a hole 14 that penetrates the new foundation 12 and the soft ground 4 and extends to the support layer 5, and the sheath tube 22 is inserted into the hole 14 and extends from the new foundation 12 to the support layer 5. It extends.

  A protective cap 28 is attached to the fixing mechanism 40. In addition, a plurality of spacers 32 are provided in the intermediate portion of the sheath tube 22, and the plurality of PC steel strands 24 and the injection pipes 26 and 27 are positioned by the spacers 32.

  The PC steel strand 24 extends from the support layer 5 to the upper side of the new foundation 12. In addition, a waterproof material 34 is packed in the lower portion of the sheath tube 22, the injection pipe 26 extends from the upper portion of the sheath tube 22 to the upper side of the waterproof material 34, and the injection pipe 27 extends from the upper portion of the sheath tube 22. It extends to the lower side of the water stop material 34.

  An inner grout 16 is filled between the water stop material 34 in the sheath tube 22 and the boundary portion between the soft ground 4 and the new foundation 12, and the PC steel strand 24 is connected to the sheath tube by the inner grout 16. 22 is fixed. An outer grout 18 is filled between the sheath tube 22 and the hole 14, and the sheath tube 22 is fixed to the inner wall of the hole 14 with the outer grout 18. Here, the water stop material 34 is disposed in the support layer 5, and the inner grout 16 is filled up to the support layer 5, and therefore, the lower end of the PC steel strand 24 is fixed to the support layer 5. ing. Further, the PC steel stranded wire 24 is integrated with the soft ground 4 and is restrained from expansion and contraction and deformation from the soft ground 4.

  Here, the wire 24 is exposed from the PC steel below the boundary between the soft ground 4 and the new foundation 12, whereas the PC steel is exposed above the boundary between the soft ground 4 and the new foundation 12. The stranded wire 24 is covered with a covering material 36. Further, a lubricant such as grease is filled between the PC steel stranded wire 24 and the covering material 36. For this reason, the PC steel strand 24 is fixed to the sheath tube 22 by the inner grout 16 below the boundary between the soft ground 4 and the new foundation 12, whereas the soft ground 4 and the new foundation 12 Above the boundary, the PC steel strand 24 is not fixed to the sheath tube 22 and can be expanded and contracted.

  The fixing mechanism 40 is an anchor having a support plate 42 formed with a hole through which the wire 24 is inserted from the PC steel, and a plurality of holes 44A placed on the support plate 42 and through which the wire 24 is inserted from each PC steel. A head 44 and a gripper 46 provided corresponding to each hole 44A are provided. Each hole 44A of the anchor head 44 is a tapered hole having a diameter reduced from the upper side to the lower side, and the gripper 46 is a wedge member inserted into the hole 44A.

  The upper end of the stranded wire 24 of the PC steel is exposed without being covered with the covering material 36, and the upper end of the stranded wire 24 of the PC steel is inserted into the hole 44A of the anchor head 44, and the hole 44A and the gripper are moved by the wedge action. 46 is in frictional engagement. Thereby, the upper end of the stranded wire 24 is fixed to the anchor head 44.

  Here, by adjusting the fixing position of the PC steel strand 24 to the anchor head 44, the tension force of the PC steel strand 24 can be adjusted. In this embodiment, the tension force is a predetermined value T1 (for example, 0). <T <100 kN). Here, the predetermined value T1 is much smaller than the design tension (hereinafter referred to as the maximum value) T0 when the anchor 20 is quake (for example, the maximum value T0 is 1000 kN and the predetermined value T1 is T0). (Less than 10%), which is large enough to remove the slack of the wire 24 from the PC steel.

  3-6 is a figure for demonstrating the earthquake-proof reinforcement method of the existing building 1. FIG. As shown in FIG. 3, first, the process of constructing the new foundation 12 is performed, and then the drilling process is performed. The new foundation 12 is constructed adjacent to the existing foundation 14 and integrated with the existing foundation 14. In the excavation process, the hole 14 is excavated from the new foundation 12 to the support layer 5 while using the casing 19.

  Next, as shown in FIG. 4, an anchor insertion step is performed. In this step, the anchor 40 assembled in advance reaches the support layer 5 at the distal end of the sheath tube 22 and the PC steel strand 24, and the rear end of the PC steel strand 24 protrudes upward from the new foundation 12. As shown in FIG.

  Next, as shown in FIG. 5A, an inner grout injection step is performed, and then an outer grout injection step is performed as shown in FIG. 5B. In the inner grout injection process, the inner grout 16 is injected into the sheath tube 22 through the injection pipe 26. Since the lower end of the injection pipe 26 is disposed on the upper side of the water blocking material 34, the inner grout 16 is blocked by the water blocking material 34 and accumulated in the sheath tube 22. In the outer grout injection process, the outer grout 18 is injected through the injection pipe 27. Since the lower end of the injection pipe 27 is disposed below the water blocking material 34, it flows out from the sheath tube 22, is blocked at the bottom of the hole 14, and accumulates in the hole 14. Next, a casing drawing process is performed. In this step, the casing 19 is pulled out from the hole 14 while a grout material is injected into the hole 14 under pressure.

  Next, as shown in FIG. 6, a tension / head treatment process is performed. In this process, after the inner grout 16 and the outer grout 18 are cured, the PC steel strand 24 is fixed to the anchor head 44 using a hydraulic jack, and the protective cap 28 is attached to the fixing mechanism 40. At this time, the fixing position of the PC steel strand 24 to the anchor head 44 is adjusted so that the tension force of the predetermined value T1 is applied to the PC steel strand 24.

  7A and 7B are elevational cross-sectional views for explaining the operation of the seismic reinforcement structure 10. As shown in FIG. 7 (A), the PC steel stranded wire 24 of the anchor 20 is always given a tension of a predetermined value T1 that is much smaller than the maximum value T0, and is intended to remove slack. As being nervous. Here, the load in the vertical direction acting on the soft ground 4 between the new foundation 12 and the support layer 5 is a predetermined value T1 that is significantly smaller than the maximum value T0.

  As shown in FIG. 7B, when a large earthquake occurs and a horizontal force P acts on the existing building 1, a pushing force is generated on the ground 2 on one side of the existing building 1 (left side in the figure). On the opposite side (the right side in the figure), when a pulling force is generated in the ground 2, the PC steel strand 24 of the anchor 20 on the side where the pulling force is generated generates a tension force having a maximum value T0, and the pulling resistance Demonstrate force T0. Thereby, when a large earthquake occurs, the settlement of the ground 2 on one side of the existing building 1 and the rising of the ground 2 on the opposite side are suppressed.

  The maximum value T0 may be set on the assumption that a middle earthquake occurs and a horizontal force acts on the existing building 1. Here, a major earthquake is an earthquake that has a possibility of occurring once during its useful life, and its seismic force is about 6 to 7 in the JMA seismic intensity class and about 300 to 400 gal in the maximum acceleration of ground motion. It is. Medium earthquakes are earthquakes that occur several times during the useful life of a building. The seismic force is about 5 or more in the Japan Meteorological Agency seismic intensity class, and about 80 to 100 gal at the maximum acceleration of ground motion. Yes (see Structure Regulations of Buildings, Japan Architecture Center (1997), pages 16-19).

  As described above, in the seismic reinforcement structure 10 and the seismic strengthening method according to the present embodiment, the anchor 20 has the predetermined value so that the pullout resistance of the maximum value T0 can be exhibited at the time of the earthquake in a normal time until the earthquake occurs. It is a standby anchor that waits in a state where the tension of T1 is applied. As a result, during normal times before an earthquake occurs, the vertical load acting on the soft ground 4 between the new foundation 12 and the support layer 5 is suppressed to a predetermined value T1 that is significantly smaller than the maximum value T0. It is possible to reduce the yield strength against the vertical load required for the soft ground 4. Accordingly, it is possible to eliminate or reduce the reinforcement work by improving the ground between the new foundation 12 and the support layer 5 and placing the piles, reducing the construction cost and shortening the construction period.

  Further, by giving a predetermined value T1 for the purpose of removing slack from the PC steel wire 24 at a normal time before the occurrence of the earthquake, the elongation amount of the PC steel wire 24 at the time of the earthquake occurrence is reduced. The vibration of the existing building 1 when an earthquake occurs can be effectively suppressed.

  Further, in the seismic reinforcing structure 10 and the seismic reinforcing method according to the present embodiment, the PC steel stranded wire 24 is insulated from the inner grout 16 by the covering material 36 in the new foundation 12 so that it can freely expand and contract. On the other hand, in the soft ground 4 and the support layer 5, the PC steel strand 24 is fixed to the inner grout 16, so that the expansion and contraction is restricted. That is, the free length portion of the PC steel wire 24 that can be freely expanded and contracted is limited to the portion in the new foundation 12, and the portion in the support layer 5 of the PC steel strand 24 is a non-free state whose expansion and contraction is completely restricted The long portion, the portion in the soft ground 4 of the PC steel strand 24, is a semi-free length portion with a weaker binding force than the non-free length portion. Therefore, the extension amount of the wire 24 can be shortened from the PC steel at the time of the earthquake occurrence, and the vibration of the existing building 1 at the time of the earthquake occurrence can be more effectively suppressed.

  FIG. 8 is an elevational sectional view showing the seismic reinforcement structure 100 of the existing building 1 according to another embodiment. As shown in this figure, the seismic reinforcement structure 100 includes a new foundation 102, a seismic frame 110 constructed on the new foundation 102, and an anchor having one end fixed to the support layer 5 and the other end fixed to the new foundation 12. 20. The new foundation 102 may be constructed integrally with the existing foundation 3 or may be constructed separately from the existing foundation 3. Here, between the existing foundation 3 and the newly-founded foundation 12 and the support layer 5, no ground-improved layer or pile is provided.

  FIG. 9 is a perspective view showing the earthquake-resistant frame 110. As shown in this figure, the seismic frame 110 includes columns 112, beams 114, braces 116 parallel to the outer wall surface of the existing building 1, beams 118, braces 119, etc. perpendicular to the outer wall surface of the existing building 1. It is a column beam frame composed of A structure including the pillar 112, the beam 114, and the brace 116 is connected to the outer wall surface of the existing building 1 by the beam 118 and the brace 119.

  In the seismic reinforcing structure 100 having such a configuration, the seismic frame 110 bears a horizontal force when an earthquake occurs. Thereby, the pulling-out force which acts on the ground 2 at the time of the occurrence of an earthquake can be suppressed, and coupled with the fact that the anchor 20 exhibits the pulling-out resistance, the seismic performance can be improved more effectively.

  In addition, the above-mentioned embodiment is for making an understanding of this invention easy, and does not limit this invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof. For example, in each of the above-described embodiments, the anchor 20 is fixed to the new foundations 12 and 102, but may be fixed to the existing foundation 3 as shown in FIG. Moreover, it is not essential to provide the anchor 20 vertically, and the anchor 20 may be provided to be inclined.

  Further, although the present invention has been described by taking the seismic reinforcement of an existing building as an example, the present invention may be applied to the seismic reinforcement of a new building. Furthermore, although the present invention has been described by taking the seismic reinforcement of the ground structure as an example, the present invention may be applied to the seismic reinforcement of the underground structure.

1 existing building (structure), 2 ground, 3 existing foundation (structure), 4 soft ground, 5 support layer (fixed ground), 10 seismic reinforcement structure, 12 newly installed foundation (structure), 14 holes, 16 inner grout , 18 Outer grout, 20 Anchor, 22 Sheath tube, 24 PC steel stranded wire (tension material), 26, 27 Injection pipe, 28 Protective cap, 32 Spacer, 34 Water stop material, 36 Coating material, 40 Fixing mechanism, 42 Support Platen, 44 Anchor head, 44A hole, 46 Gripper, 100 Seismic reinforcement structure, 102 New foundation (structure), 110 Seismic frame, 112 columns, 114 beams, 116 braces, 118 beams, 119 braces

Claims (6)

A method for seismic reinforcement performed by anchoring an anchor to a structure built on the ground and the anchoring ground of the anchor,
The anchor is attached to the structure in a state in which the tension of the anchor is such that the tension does not loosen and is smaller than the designed tension when an earthquake occurs. And a seismic reinforcement method comprising fixing to the fixing ground.   The portion of the tendon in the structure is configured to be stretchable, and the portion of the tendon that is closer to the fixing ground than the structure is configured to be constrained to stretch. The earthquake-proof reinforcement method according to 1.   The earthquake-resistant structure according to claim 1 or 2, wherein the structure is a foundation that supports a structure on the ground or a foundation that supports an earthquake-resistant frame connected to the structure on the ground. Construction method. A seismic reinforcement structure in which the anchor is fixed to the structure built on the ground and the anchoring ground of the anchor,
In the state in which the tension material of the anchor is applied with a tension force that is large enough to prevent the tension material from loosening and smaller than the designed tension force at the time of the occurrence of an earthquake, the anchor And an earthquake-resistant structure characterized by being fixed to the fixing ground.   A portion of the tendon in the structure is configured to be stretchable and a portion of the tendon that is closer to the fixing ground than the structure is configured so that expansion and contraction is restricted. The earthquake-resistant structure according to claim 4.   The earthquake-resistant structure according to claim 4 or 5, wherein the structure is a foundation that supports a structure on the ground or a foundation that supports an earthquake-resistant frame connected to the structure on the ground. Construction.

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