JP4279305B2 - Seismic reinforcement method for unreinforced concrete structures - Google Patents

Description

  The present invention relates to a seismic reinforcement method for reinforcing a columnar unreinforced concrete structure.

  Concrete has the property of high strength against compression but low strength against tension. For this reason, a reinforced concrete structure in which a steel material such as a reinforcing bar is combined with concrete is often used for a structure such as a member subjected to bending to which a tensile force acts. In contrast, unreinforced concrete structures are mostly used in places where compressive forces are applied, but there are many unreinforced concrete piers in old age bridges. There is a need for seismic reinforcement to prevent collapse of such unreinforced concrete columns during an earthquake.

Conventionally, as a technique for seismic reinforcement of a columnar structure, for example, methods described in Patent Documents 1 and 2 below are known. Patent Document 1 discloses a method for providing seismic reinforcement of a column by disposing a plurality of reinforcing steel plates on the surface of a reinforced concrete column and covering the column. Further, Patent Document 2 discloses a method of restraining this column with an L-shaped support material arranged at the four corners of a reinforced concrete column and a connecting material for connecting the support material, thereby achieving seismic reinforcement. In addition to these, many methods for seismic reinforcement of reinforced concrete columns are known.
Japanese Patent Laid-Open No. 9-41565 JP 2000-120023 A

  However, the columnar structure made of reinforced concrete and the columnar structure made of reinforced concrete differ greatly in the form of destruction during an earthquake. Therefore, even if the seismic reinforcement method for a reinforced concrete column as described above is applied to an unreinforced concrete structure as it is, it cannot always be properly reinforced.

  Therefore, an object of the present invention is to provide a seismic reinforcement method for appropriately reinforcing a columnar unreinforced concrete structure.

The seismic reinforcement method for an unreinforced concrete structure according to the present invention is a seismic reinforcement method for reinforcing a columnar unreinforced concrete structure. The movement restriction means that connects the parts and restricts relative movement is installed at the weak part, and when the weak part is damaged, the unreinforced concrete structure is divided into an upper part and a lower part with the horizontal plane as a boundary. The upper and lower parts are separated from each other, and the movement restricting means is installed before the upper part and the lower part are separated. The movement restricting means is separated after the upper part and the lower part are separated. A method for seismic reinforcement of an unreinforced concrete structure , wherein the relative movement of the upper part and the lower part in the horizontal direction is restricted .

  When this type of column-shaped unreinforced concrete structure is subjected to an earthquake force, a weak point with weak strength will crack, and the crack will grow in the horizontal direction, causing a boundary between the horizontal plane including the weak point. Thus, it is known that the structure is separated vertically. The upper part and the lower part above the weak point part slide with a horizontal contact surface generated by the separation, and the energy of the earthquake is absorbed by the friction between the upper part and the lower part. At this time, in the structure subjected to the seismic reinforcement by the above method, the movement restriction means connects the upper part and the lower part of the weak point part and restricts the relative movement. The seismic energy is further absorbed by the resistance force. Further, in this seismic reinforcement method, since the movement restricting means only needs to be installed at a position corresponding to the weak point portion, it is possible to save members and to provide efficient seismic resistance compared to the case where the entire structure is reinforced. Reinforcement can be achieved.

  The movement restricting means preferably includes an energy absorbing member that absorbs energy by deformation. According to this configuration, when the relative movement between the upper part and the lower part of the structure occurs during the earthquake, the energy of the earthquake is absorbed by the deformation of the energy absorbing member accompanying the movement.

  Moreover, as a suitable structure of such an energy absorption member, the structure which has a strip | belt-shaped member wound by the circumference | surroundings of an unreinforced concrete structure with the width | variety over the weak point part is mentioned.

  The weak point portion may be a concrete joint in an unreinforced concrete structure. When this kind of columnar unreinforced concrete structure is subjected to an earthquake force, there is a high possibility that cracks will occur at the joints of concrete with low strength. Therefore, the above-mentioned operation can be achieved by installing the movement restricting means at the position of the seam as the weak point.

  Moreover, you may further provide the process of providing a weak part in an unreinforced concrete structure previously as said weak point part. According to this configuration, the above-described effect can be achieved by intentionally setting a desired position as the weak point portion by providing the weak portion in advance and installing the movement restricting means at that position.

  According to the seismic reinforcement method of the present invention, a columnar unreinforced concrete structure can be appropriately reinforced.

  Hereinafter, preferred embodiments of the seismic reinforcement method according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
A bridge 100 shown in FIG. 1 includes a plurality of unreinforced concrete piers (columnar unreinforced concrete structures) 1 and bridge girders 3 that are supported by the piers 1 and extend in the horizontal direction. The bridge pier 1 includes a footing 7 provided at the lower part and fixed to the ground 5, and a support part 11 provided at the upper part and supporting the bridge girder 3.

  The form of destruction of such an reinforced concrete pier 1 during an earthquake is as follows. During an earthquake, the pier 1 receives a bending moment due to a horizontal force from the bridge girder 3 and a crack is generated in a part of the side surface of the pier 1 that is weak against tensile force. The generated crack grows in the horizontal direction, and thereafter, the upper portion 1a and the lower portion 1b of the pier 1 are separated from each other with the horizontal plane at the position where the crack is generated. After that, the pier upper part 1a slides in the horizontal direction while making contact with the pier lower part 1b on the horizontal plane generated by the separation, and the energy of the earthquake is absorbed by the friction during the sliding. The horizontal plane on which the pier upper part 1a and the pier lower part 1b slide in this manner is hereinafter referred to as a “sliding surface”. Here, considering the structure of the pier 1, when concrete is handed over during construction of the pier 1, a joint seam (weak point portion) A that forms a horizontal plane is formed on the pier 1. Since this joint A is a portion that is particularly susceptible to tensile force, there is a high possibility that a crack will first occur when an earthquake occurs. Therefore, there is a high possibility that the sliding surface matches the joint A.

  Based on the above knowledge, in the seismic reinforcement method for the pier 1, the band-shaped member (energy absorption) is provided so as to cover the joint A on the side surface of the pier 1 before separation and to connect the upper pier 1 a and the lower pier 1 b. Member) 13 is attached. The belt-like member 13 has an annular shape extending horizontally, is wound around the entire circumference of the pier 1 at a position extending up and down the joint A, and is fixed to the side surface of the pier 1. For fixing the belt-like member 13 to the side surface of the pier 1, fixing means such as bolting, bonding with an adhesive, or a combination of bolting and an adhesive is used. In this type of pier, the seam A can often be discriminated by the appearance of the side surface of the pier 1 even before separation as described above. In that case, by visually observing the side surface of the pier 1, What is necessary is just to pinpoint the position of the joint A which should install the strip | belt-shaped member 13. FIG.

  When the pier 1 is separated vertically with the joint A as the boundary as described above, the belt-like member 13 functions as a movement restricting means for restricting the horizontal movement of the pier upper part 1a with respect to the pier lower part 1b. . Examples of suitable materials for the belt-like member 13 include carbon fiber sheets, aramid fiber sheets, glass fiber sheets, nylon sheets, polyester, which are elastic materials, and steel plates which are elastic-plastic materials.

  When this pier 1 receives a large amount of energy from an earthquake, there is a high possibility that a crack will occur on the side surface of the joint A as described above. After that, when the crack grows and the pier 1 is separated from the upper and lower sides with the joint A as a boundary, as shown in FIG. 3, the pier upper part 1a becomes the pier lower part 1b with the joint A serving as a sliding surface as a boundary. Slides horizontally against. The earthquake energy is absorbed by the friction caused by this sliding. At this time, the belt-like member 13 repeats elastic expansion and contraction in response to the movement of the pier upper part 1a. Further, when the belt-like member 13 made of an elastoplastic material is used, the belt-like member 13 may be further plastically deformed by receiving energy. Due to such deformation of the belt-like member 13, the energy of the earthquake is further absorbed.

  Therefore, this pier 1 can absorb the large energy of the earthquake by the friction between the pier upper part 1a and the pier lower part 1b on the sliding surface and the deformation of the strip member 13, and suppress the collapse of the pier 1 at the time of the earthquake. Can do. Moreover, since the moving amount | distance with respect to the pier lower part 1b of the pier upper part 1a is restrict | limited by the strip | belt-shaped member 13, it can suppress that the pier upper part 1a shifts | deviates extremely from the pier lower part 1b, and the pier 1 collapses. Further, since the belt-like member 13 is wound around the entire circumference of the pier 1, even when the pier upper part 1 a moves in any horizontal direction, the deformation of the belt-like member 13 follows and the energy absorption of the earthquake is performed. Is called.

  In addition, if the rigidity of the belt-shaped member 13 is too high, the absorption of the earthquake energy due to the expansion and contraction of the belt-shaped member 13 as described above is not sufficiently performed. It is preferable to moderately suppress the rigidity of the belt-like member 13 so that the maximum deformation is 0.2% or more. For this reason, the material and dimension of the strip-shaped member 13 are adjusted based on the pier 1 and the energy of the assumed earthquake. Further, if the rigidity of the belt-like member 13 is too low, the displacement of the pier upper part 1a at the time of the earthquake becomes large and the possibility of the pier 1 collapsing increases, so the belt-like shape when the pier 1 receives a horizontal force due to the earthquake. It is preferable to ensure the rigidity of the belt-like member 13 so that the maximum deformation of the member 13 is 50% or less.

  Further, in this seismic reinforcement method, since the band-like member 13 is installed in advance only around the joint A where the sliding surface is most likely to occur, the reinforcement is more effective than the case where the entire side surface of the pier 1 is reinforced. Therefore, it is possible to save a large number of members and to achieve effective seismic reinforcement.

(Second Embodiment)
As shown in FIG. 4, in the seismic reinforcement method for the pier 1 according to the present embodiment, a connecting steel (energy absorbing member) 23 for connecting the pier upper portion 1a and the pier lower portion 1b in advance with the joint A as a boundary is attached. It is done. The connecting steel 23 has a bowl shape, and both ends of the connecting steel 13 are inserted into holes formed in the respective sides of the pier upper part 1a and the pier lower part 1b in advance, and the pier upper part by mortar filled in the hole. 1a, fixed to the pier lower part 1b. Such a connecting steel 23 is connected vertically to the pier upper part 1a and the pier lower part 1b while intersecting in an X shape with a pair of two on both side surfaces of the pier 1. Note that a pair of two connecting steels 23 are similarly attached to the other side of the pier 1 in FIG. These connecting steels 23 function as a movement restricting means for restricting the horizontal movement of the pier upper part 1a with respect to the pier lower part 1b when the pier 1 is separated up and down at the joint A as described above. . As the connecting steel 23, an elastic-plastic member such as a reinforcing bar, a PC steel bar, a steel material, a PC steel wire, or the like can be suitably used.

  In this case, when the pier 1 receives large energy due to the earthquake and the pier 1 is separated vertically with the joint A as a boundary, as shown in FIG. 5, with the joint A as a sliding surface as a boundary, The pier upper part 1a slides horizontally with respect to the pier lower part 1b. Seismic energy is absorbed by the friction caused by this sliding. At this time, the connecting steel 23 repeats elastic expansion and contraction in response to the movement of the pier upper part 1a. Further, the connecting steel 23 may be further plastically deformed by receiving energy. Due to the deformation of the connecting steel 23, the energy of the earthquake is further absorbed. Therefore, this pier 1 can absorb the large energy of the earthquake by the friction between the pier upper part 1a and the pier lower part 1b on the sliding surface and the deformation of the connecting steel 23, and suppress the collapse of the pier 1 at the time of the earthquake. Can do. Moreover, since the moving amount with respect to the pier lower part 1b of the pier upper part 1a is restrict | limited by the connection steel 23, it can suppress that the pier upper part 1a shifts | deviates extremely from the pier lower part 1b, and the pier 1 collapses.

  Thus, also by this seismic reinforcement method, the same effect as the seismic reinforcement method in 1st Embodiment mentioned above is show | played. Further, since the two pairs of connecting steels 23 are crossed in an X shape on both side surfaces of the pier 1, when the pier upper part 1 a moves horizontally in the wide width direction of the pier 1, the connecting steel 23 Will expand and contract substantially in the axial direction, and the connecting steel 23 is not easily destroyed. In addition, in the seismic reinforcement method of this embodiment, about the structure same or equivalent to the said 1st Embodiment, the same code | symbol is attached | subjected to drawing and the description is abbreviate | omitted.

(Third embodiment)
As shown in FIG. 6, in the seismic reinforcement method for the pier 1 according to this embodiment, a connecting steel (energy absorbing member) 33 for connecting the pier upper part 1a and the pier lower part 1b in advance with the joint A as a boundary is attached. It is done. This connecting steel 33 has a bowl shape, and both ends of the connecting steel 13 are inserted into holes formed in advance on the respective sides of the pier upper part 1a and the pier lower part 1b, and the pier upper part is formed by mortar filled in the hole. 1a, fixed to the pier lower part 1b. A large number of such connecting steels 33 are arranged on the entire circumference of the side surface of the pier 1 so that the pier upper part 1a and the pier lower part 1b are connected in advance vertically over the entire circumference. And these connection steels 33 as movement restriction means for restricting the horizontal movement of the pier upper part 1a with respect to the pier lower part 1b when the pier 1 is separated vertically with the joint A as the boundary as described above. Function. As the connecting steel 33, an elastic-plastic member such as a reinforcing bar, a PC steel bar, a steel material, a PC steel wire, or the like can be suitably used.

  According to such a seismic strengthening method, as in the first embodiment, the energy of the earthquake is absorbed by friction caused by sliding between the pier upper part 1 c and the pier lower part 1 d and the deformation of the connecting steel 33, and the pier by the connecting steel 33 is used. The pier 1 is prevented from collapsing due to the movement amount limitation of the upper part 1c. Further, since the connecting steel 33 is arranged around the joint A in the entire circumference of the pier 1, even if the pier upper portion 1 a moves in any horizontal direction, the energy of the earthquake is caused by the deformation of the connecting steel 33. Absorption takes place. In addition, in the seismic reinforcement method of this embodiment, about the structure same or equivalent to said each embodiment, the same code | symbol is attached | subjected to drawing and the description is abbreviate | omitted.

(Fourth embodiment)
As shown in FIG. 7, in the seismic reinforcement method for the pier 1 according to the present embodiment, a connecting portion (energy absorbing member) 35 for connecting the pier upper portion 1a and the pier lower portion 1b in advance with the joint A as a boundary is attached. It is done. The connecting portion 35 has a strip shape, and both ends of the connecting steel 13 are fixed to the pier upper portion 1a and the pier by using fixing means such as bolting, bonding with an adhesive, or a combination of bolting and an adhesive. It is fixed to each side surface of the lower part 1b. A large number of such connecting portions 35 are arranged on the entire circumference of the side surface of the pier 1 so that the pier upper portion 1a and the pier lower portion 1b are connected in advance vertically over the entire circumference. And when these bridge | bridging parts 35 restrict | limit the bridge pier 1 to the pier lower part 1b with respect to the bridge pier lower part 1b when the pier 1 is separated into the upper and lower sides by the joint line A as mentioned above as a movement limitation means. Function. Examples of suitable materials for the connecting portion 35 include carbon fiber sheets that are elastic materials, aramid fiber sheets, glass fiber sheets, nylon sheets, polyester, and steel plates that are elastic-plastic materials.

  Even in such a seismic reinforcement method, as in the first embodiment, the energy of the earthquake is absorbed by the friction caused by the sliding between the pier upper part 1c and the pier lower part 1d and the deformation of the connecting part 35. The pier 1 is prevented from collapsing due to the movement amount limitation of the upper part 1c. Moreover, since the connection part 35 is arrange | positioned in the circumference | surroundings of the joint seam A around the pier 1, even if the pier upper part 1a moves in any horizontal direction, the energy of the earthquake is generated by the deformation of the connection part 35. Absorption takes place. In addition, in the seismic reinforcement method of this embodiment, about the structure same or equivalent to said each embodiment, the same code | symbol is attached | subjected to drawing and the description is abbreviate | omitted.

(Fifth embodiment)
As shown in FIG. 8, in the seismic reinforcement method for a pier 1 according to this embodiment, first, a cross-sectional defect (fragile portion) 41 is formed in advance on the side surface of the pier 1 so that a crack at the time of an earthquake occurs in that portion. It is easy to generate. The cross-sectional defect 41 is formed as a V groove extending horizontally over the entire circumference. Next, as shown in FIG. 9, the belt-like member 13 is attached at a position covering the cross-sectional defect portion 41 and extending above and below the cross-sectional defect portion 41. In addition, the structure of the strip | belt-shaped member 13 and the method of installation are as having demonstrated the said 1st Embodiment.

  In this case, when the pier 1 receives a large amount of energy due to the earthquake, a crack is generated in the weakest cross-sectional defect portion 41 and the crack grows in the horizontal direction, so that the horizontal plane including the cross-sectional defect portion 41 is a boundary. The pier upper part 1c and the pier lower part 1d are separated vertically. Thus, by providing the cross-sectional defect | deletion part 41 in advance on the pier 1 side surface, the said isolation | separation can be induced in the desired position in which the strip | belt-shaped member 13 was previously provided. Thereafter, as in the first embodiment, the energy of the earthquake is absorbed by friction caused by sliding between the pier upper part 1c and the pier lower part 1d and the deformation of the strip member 13, and the movement amount limitation of the pier upper part 1c by the strip member 13 is limited. This suppresses the pier 1 from collapsing.

  Moreover, in this seismic reinforcement method, since the band-shaped member 13 is installed in advance only around the cross-sectional defect part 41 where the sliding surface is induced, the reinforcing member is more than the case where the entire side surface of the pier 1 is reinforced. Can be saved, and effective seismic reinforcement can be achieved.

  In this case, instead of the belt-like member 13, as shown in FIG. 10, a connecting steel 23 for connecting the pier upper part 1 c and the pier lower part 1 d in advance with the cross-sectional defect part 41 as a boundary may be attached. Alternatively, instead of the belt-like member 13, as shown in FIG. 11, a connecting steel 33 that connects the pier upper part 1c and the pier lower part 1d in advance may be attached. Alternatively, instead of the belt-like member 13, as shown in FIG. 12, a connecting portion 35 that connects the pier upper portion 1c and the pier lower portion 1d in advance may be attached. In this case, the structure of the connection steel 23, the connection steel 33, and the connection part 35 and the way of installation are as having demonstrated in the said 2nd-4th embodiment, respectively. The same effect as described above can be obtained by such a seismic reinforcement method. In addition, in the seismic reinforcement method of this embodiment, about the structure same or equivalent to said each embodiment, the same code | symbol is attached | subjected to drawing and the description is abbreviate | omitted.

It is a figure which shows an example of the bridge in which the bridge pier to which the seismic reinforcement method concerning this invention is applied is used. It is a perspective view of the pier which shows 1st Embodiment of the earthquake-proof reinforcement method which concerns on this invention. It is a side view which shows the motion at the time of the earthquake of the pier of FIG. It is a perspective view of the pier which shows 2nd Embodiment of the earthquake-proof reinforcement method which concerns on this invention. It is a side view which shows the motion at the time of the earthquake of the pier of FIG. It is a perspective view of the pier which shows 3rd Embodiment of the earthquake-proof reinforcement method which concerns on this invention. It is a perspective view of the pier which shows 4th Embodiment of the earthquake-proof reinforcement method which concerns on this invention. It is a perspective view of the pier which shows 5th Embodiment of the earthquake-proof reinforcement method which concerns on this invention. It is a perspective view of the pier which shows 5th Embodiment of the earthquake-proof reinforcement method which concerns on this invention. It is a perspective view of the pier which shows the modification of 5th Embodiment. It is a perspective view of the pier which shows the other modification of 5th Embodiment. It is a perspective view of the pier which shows the other modification of 5th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pier (unreinforced concrete structure), 1a ... Upper part of pier (above the weak part), 1b ... Lower part of the pier (part below the weak part), 1c ... Upper part of the pier (above the weak part) Part), 1d ... lower part of the pier (the part below the weak point part), 13 ... belt-like member (movement restricting means, energy absorbing member), 23 ... connecting steel (movement restricting means, energy absorbing member), 33 ... connecting steel ( Movement restricting means, energy absorbing member), 35... Connecting part (movement restricting means, energy absorbing member), 41. Cross-sectional defect (weak point, weak part), A ... concrete joint (weak point).

Claims (5)

A seismic reinforcement method for reinforcing columnar unreinforced concrete structures,
In the unreinforced concrete structure, a movement limiting means for connecting the upper part and the lower part of the weak point part having weak strength and restricting relative movement is installed in the weak point part,
The weak point is
When damaged, the unreinforced concrete structure is a part that separates up and down into the upper part and the lower part across a horizontal plane,
Installation of the movement restricting means on the weak spot is performed before separation of the upper part and the lower part,
The movement restriction means includes
An unreinforced concrete structure that restricts relative movement in the horizontal direction between the upper part and the lower part after separation of the upper part and the lower part. Seismic reinforcement method for objects. The movement restriction means includes
The method for seismic reinforcement of an unreinforced concrete structure according to claim 1, further comprising an energy absorbing member that absorbs energy by deformation. The energy absorbing member is
The method for seismic reinforcement of an unreinforced concrete structure according to claim 2, further comprising a belt-like member wound around the unreinforced concrete structure with a width extending up and down the weak point.   The method for seismic reinforcement of an unreinforced concrete structure according to any one of claims 1 to 3, wherein the weak point portion is a joint of concrete in the unreinforced concrete structure. The method for seismic reinforcement of an unreinforced concrete structure according to any one of claims 1 to 3, further comprising a step of providing a weakened portion in the unreinforced concrete structure in advance as the weak point portion.

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