JP2014227761A - Junction structure and method between new skeleton and existing skeleton - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure transmission performance for in-earthquake shearing force at a junction between a new skeleton and an existing skeleton, and to improve workability of an anchor at low cost.SOLUTION: There is provided a junction structure 10 of a new skeleton 1, having an anchor 20 embedded in a junction between the new skeleton 1 and an existing skeleton 2, and the existing skeleton 2, and the anchor 20 includes a pair of irregular-shape reinforcing bars (thin-diameter parts 22, 24) one of which is fixed to the new skeleton 1 and the other of which is fixed to the existing skeleton 2, and a thick-diameter part 26 which is a columnar steel material provided between the pair of irregular-shape reinforcing bars (thin-diameter parts 22, 24) over the new skeleton 1 and existing skeleton 2, and has a larger diameter than the pair of irregular-shape reinforcing bars (thin-diameter parts 22, 24) and also has a larger depth of embedding in the new skeleton 1 than in the existing skeleton 2.

Description

  The present invention relates to a joining structure and method for a newly installed housing and an existing housing.

  When a new frame is constructed on the surface of an existing frame for the purpose of seismic retrofit, etc., and these are joined, a rebar is applied to the joint so that the shearing force at the time of the earthquake is transmitted at the joint between the new frame and the existing frame. Embedding anchors by means such as In addition, in the joint structure of the new housing and the existing housing described in Patent Documents 1 and 2 proposed as a technique for improving this, a disk having a convex portion on the outer peripheral portion, the convex portion is embedded in the existing housing, The other part is provided so as to be embedded in the new housing, and an anchor is inserted through the hole in the center of the disk.

Japanese Patent No. 4230533 JP 2012-246641 A

  In general anchors, when a shear force acts on the interface and a displacement occurs, stress concentrates on a small area of contact between the rebar near the interface and the concrete, and this local stress supports the concrete. Destruction will occur. When this bearing failure occurs, bending deformation to the anchor easily occurs, and the yield strength of the interface decreases due to the bending yield of the anchor bar. In the techniques described in Patent Documents 1 and 2, Patent Documents 1 and 2 are proposed as techniques for preventing fracture of bearing pressure of concrete and improving the yield strength of the interface. However, in the joint structure of the newly installed case and the existing case described in Patent Documents 1 and 2, since the embedding depth of the discs in both cases is small, rotational deformation of the disc occurs due to the shearing force during the earthquake. . Therefore, an anchor for fixing the disk in order to suppress the rotational deformation of the disk is required separately from the anchor necessary for the tensile force that will be generated at the interface together with the shearing force, which causes an increase in cost. In addition, it is difficult to fix the anchor and the disk including injection of the resin to the back surface of the disk at once, and the construction procedure becomes complicated. In addition, although the method of making the whole anchor so thick that bending deformation does not occur is considered, in this method, the amount of cutting of the concrete of the existing frame increases and there is a concern about collision with the embedded object.

  The present invention has been made in view of the above circumstances, and while ensuring the transmission performance of the shearing force at the time of an earthquake at the joint between the newly installed housing and the existing housing, it is possible to improve the workability of the anchor at a low cost. It is to be an issue.

  In order to solve the above-mentioned problem, the joint structure between the new housing and the existing housing according to the present invention is a joint structure between the new housing and the existing housing in which an anchor is embedded in the joint between the new housing and the existing housing. The anchor has a pair of deformed reinforcing bars, one of which is fixed to the new casing and the other of which is fixed to the existing casing, and a columnar shape provided between the pair of deformed reinforcing bars so as to straddle the new casing and the existing casing. The steel material has a larger diameter than the pair of deformed reinforcing bars, and a large-diameter portion in which the embedding depth in the new housing is larger than the embedding depth in the existing housing.

  In the joint structure of the new housing and the existing housing, the concrete strength of the new housing is n (≧ 1) times the concrete strength of the existing housing, and the embedding depth of the large diameter portion in the new housing is However, 3 / n times or more of the embedding depth of the large diameter portion in the existing casing may be used.

  Further, the joining method of the new housing and the existing housing according to the present invention is a joining method of the new housing and the existing housing in which an anchor is embedded in the joint portion between the new housing and the existing housing, and the anchor is a pair of A deformed reinforcing bar and a columnar steel material provided between the pair of deformed reinforcing bars, each having a larger diameter portion than that of the pair of deformed reinforcing bars, the anchor, the new frame and the existing frame Then, it is embedded so that the embedding depth of the large-diameter portion into the new housing is greater than the embedding depth of the existing housing.

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring the transmission performance of the shear force at the time of an earthquake in the junction part of a newly installed frame and an existing frame, the workability of an anchor can be improved at low cost.

It is sectional drawing which shows the joining structure of the newly installed housing and existing housing which concern on one Embodiment. It is a figure for demonstrating the relationship between the embedding depth to the newly installed housing of a large diameter part, and the embedding depth to the existing housing. It is a figure for demonstrating the relationship between the embedding depth to the newly installed housing of a large diameter part, and the embedding depth to the existing housing.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a joint structure 10 between a new housing 1 and an existing housing 2 according to an embodiment. As shown in this figure, the joining structure 10 is a joining structure of an existing casing 2 which is an existing concrete structure and a new casing 1 which is a new concrete structure bonded to the surface thereof, and straddles both. The anchor 20 is embedded.

  The anchor 20 includes a narrow-diameter portion 22 embedded in the existing housing 2, a small-diameter portion 24 embedded in the new housing 1, and a large-diameter portion 26 embedded in both the new housing 1 and the existing housing 2. And. The small-diameter portions 22 and 24 are deformed reinforcing bars having a diameter of 22 mm (D22) or less, and are embedded in the existing housing 2 or the new housing 1 perpendicularly to these joint interfaces. The large-diameter portion 26 is a columnar steel material (for example, deformed reinforcing bar, bolt, or round steel) having a larger diameter than the deformed reinforcing bars 22 and 24 (for example, a diameter of 29 mm (D29) to a diameter of 51 mm (D51)). . The small-diameter portions 22 and 24 and the large-diameter portion 26 are coaxially joined by screw fixation or welding (for example, friction welding or stud welding).

  The anchor 20 is a construction anchor after the adhesive system, and the portion embedded in the existing housing 2 of the small diameter portion 22 and the large diameter portion 26 by the adhesive filled in the hole drilled in the existing housing 2 Fixed to the existing housing 2. Moreover, the part embedded in the newly installed casing 1 of the small diameter part 24 and the large diameter part 26 is being fixed to the newly installed casing 1 by the adhesive force of concrete and steel materials.

  Here, the embedding depth of the large-diameter portion 26 in the new housing 1 is larger than the embedding depth in the existing housing 2. Hereinafter, the relationship between the embedding depth of the large-diameter portion 26 in the new housing 1 and the embedding depth in the existing housing 2 will be described.

  2 and 3 are diagrams for explaining the relationship between the embedding depth of the large-diameter portion 26 in the new housing 1 and the embedding depth in the existing housing 2. As shown in these figures, the embedding depth of the large-diameter portion 26 in the new housing 1 and the embedding depth in the existing housing 2 are the concrete strength Fc1 of the new housing 1 and the concrete strength Fc2 of the existing housing 2. It is set according to the relationship.

  In FIG. 2, when the concrete strength Fc1 of the new housing 1 and the concrete strength Fc2 of the existing housing 2 are the same (Fc1 = Fc2), the embedding depth of the large diameter portion 26 in the new housing 1 and the existing housing 2 The relationship with the embedding depth is shown. As shown in this figure, when the concrete strength Fc1 of the new housing 1 and the concrete strength Fc2 of the existing housing 2 are the same, the embedding depth of the large diameter portion 26 in the new housing 1 is the same as that of the existing housing 2. The embedding depth c is set to 3 times or more.

  Under this condition, when a shearing force at the time of an earthquake acts on the joint portion between the new housing 1 and the existing housing 2 in the right direction in the figure, the anchoring stresses Qa, Qb, Qc are applied to the anchor 26 of the joint portion as shown in the figure. Occurs. The anchor 26 embedded in the existing housing 2 has a bearing stress Qc in the range from the joining interface of the existing housing 2 to the tip of the large-diameter portion 26 (the depth c from the joining interface). Acts in the same direction (rightward in the figure). In order for the anchor 26 not to rotate, in the range of depth b (<3c) from the joint interface of the new housing 1, the bearing stress Qb acting in the direction opposite to the acting direction of the shearing force (leftward in the figure), In the range from the depth b of the new housing 1 to the tip of the large-diameter portion 26 (depth b to depth b + a), there is a bearing stress Qa acting in the same direction as the direction of the shearing force (rightward in the figure). That's fine.

  Here, assuming that there is no yield of the anchor 20 and no gradient of the bearing stress level by giving a sufficiently rigid cross section to the bending stress of the steel material generated at the interface in the large diameter portion 26, the bearing stress Qa, Qb, Qc and the lengths a, b, c in the depth direction in which they act are in a relationship of Qa: Qb: Qc = a: b: c, and from the balance of forces (Qa + Qc = Qb) Here, a, b, and c have a relationship of a + c = b. From the moment balance (Qb · (c / 2 + b / 2) = Qa · (c / 2 + a / 2)) around the point of application of the bearing stress Qc (position of depth c / 2 from the joint interface), The lengths a, b, and c have a relationship of a = c and b = 2c.

  Therefore, the relationship between the lengths a, b, and c is a + b = 3c, that is, the embedding depth (a + b) of the large-diameter portion 26 in the new housing 1 is set as the embedding depth of the large-diameter portion 26 in the existing housing 2. By setting the depth c to be three times or more, the bearing stress Qc can be sufficiently exhibited, and the fixing degree of the large diameter portion 26 can be secured.

  Similarly, in FIG. 3, when the concrete strength Fc1 of the new housing 1 is n (> 1) times the concrete strength Fc2 of the existing housing 2 (Fc1 = n · Fc2), The relationship between the embedding depth and the embedding depth to the existing housing 2 is shown. As shown in this figure, when the concrete strength Fc1 of the new housing 1 is n times the concrete strength Fc2 of the existing housing 2, the embedding depth of the large diameter portion 26 in the new housing 1 is the same as that of the existing housing 2. If the embedding depth c is set to 3 / n times or more, the fixing degree of the large-diameter portion 26 can be secured.

  Under this condition, when a shearing force at the time of an earthquake acts on the joint portion between the new housing 1 and the existing housing 2 in the right direction in the figure, the anchoring stresses Qa, Qb, Qc are applied to the anchor 26 of the joint portion as shown in the figure. Occurs. The anchor 26 embedded in the existing housing 2 has a bearing stress Qc in the range from the joining interface of the existing housing 2 to the tip of the large-diameter portion 26 (the depth c from the joining interface). Acts in the same direction (rightward in the figure). In order to prevent the anchor 26 from rotating, the bearing stress Qb acting in the direction opposite to the acting direction of the shearing force (leftward in the figure) in the range of the depth b (<3 c / n) from the joint interface of the new housing 1. And the bearing stress Qa acting in the same direction as the direction of action of the shear force (rightward in the figure) in the range from the depth b of the new housing 1 to the tip of the large-diameter portion 26 (depth b to depth b + a). If there is.

  Here, assuming that there is no yield of the anchor 20 and no gradient of the bearing stress level by giving a sufficiently rigid cross section to the bending stress of the steel material generated at the interface in the large diameter portion 26, the bearing stress Qa, Qb, Qc and the lengths a, b, c in the depth direction in which they act are in a relationship of Qa: Qb: Qc = n · a: n · b: c, and force balance (Qa + Qc = Qb ), The lengths a, b, and c have a relationship of n · (a + c) = n · b. From the moment balance (Qb · (c / 2 + b / 2) = Qa · (c / 2 + a / 2)) around the point of application of the bearing stress Qc (position of depth c / 2 from the joint interface), The lengths a, b, and c have a relationship of a = c / n and b = 2c / n.

  Therefore, the relationship between the lengths a, b, and c is a + b = 3c / n, that is, the embedding depth (a + b) of the large-diameter portion 26 in the new housing 1 is set to the existing housing 2 of the large-diameter portion 26. By setting the embedding depth c to 3 / n times or more, the bearing stress Qc can be sufficiently exerted, and the fixing degree of the large diameter portion 26 can be secured.

  As described above, in the joint structure 10 of the new housing 1 and the existing housing 2 according to the present embodiment, the anchor 20 has a pair of deformed reinforcing bars (thin diameter) in which one is fixed to the new housing 1 and the other is fixed to the existing housing 2. Parts 22 and 24) and a pair of deformed reinforcing bars (thin diameter portions 22 and 24) so as to straddle the newly installed casing 1 and the existing casing 2, and a pair of deformed reinforcing bars (thin And a large-diameter portion 26 having a larger diameter than the diameter portions 22, 24) and having a depth embedded in the new housing 1 larger than a depth embedded in the existing housing 2. Here, the portion of the anchor 20 that straddles the newly installed housing 1 and the existing housing 2 is made to have a large-diameter portion 26 that is thicker than the pair of deformed reinforcing bars (small-diameter portions 22, 24), thereby increasing the bending rigidity of the portion. The bending deformation generated in the part by the shearing force at the time of the earthquake can be suppressed, and the destruction of the concrete due to the bending deformation of the part can be suppressed. Further, since the embedding depth of the large-diameter portion 26 in the new housing 1 is made larger than the embedding depth in the existing housing 2, the fixing degree of the large-diameter portion 26 due to the shearing force at the time of an earthquake can be secured. Regardless of the presence or absence of the small-diameter portion 22 on the housing 2 side, it is possible to ensure the transmission performance of the shearing force by the anchor 20. Here, since an out-of-plane stress such as a tensile force is generally applied to the interface in addition to the shearing force, the small-diameter portions 22 and 24 may be provided according to the amount, and the small-diameter portion 22 on the existing housing 2 side. The transmission performance of the shearing force by the anchor 20 can be ensured regardless of the increase in length. Moreover, since these materials including the large-diameter portion 26 are all composed of existing reinforcing bars and the like, they can be procured at a low cost even if they are all combined. The anchor is also installed with the large diameter 26 and the small diameter 22, and can be performed at once with a resin or the like.

  If the part of the anchor straddling the new housing 1 and the existing housing 2 is a disk, if the surface of the existing housing 2 is weak, it must be dug to a healthy range. In that case, the entire disk is embedded in the existing housing 2 Therefore, there is a concern that the transmission performance of the shearing force by the part is not exhibited. On the other hand, by making the said part into the cylindrical large diameter part 26, even when digging the existing housing 2 deeply, the said part can be provided so that it may straddle the new housing 1 and the existing housing 2, Can respond flexibly to the situation.

  Further, in the joint structure 10 of the new housing 1 and the existing housing 2 according to the present embodiment, the concrete strength Fc1 of the new housing 1 is n (≧ 1) times the concrete strength Fc2 of the existing housing 2, and the large-diameter portion 26 The embedded depth (a + b) in the newly installed casing 1 is not less than 3 / n times the embedded depth c of the large diameter portion 26 in the existing casing 2. As a result, the bearing stress Qc acting in the same direction as the acting direction of the shearing force can be sufficiently exerted in the range from the joining interface of the existing housing 2 to the tip of the large-diameter portion 26, and the large-diameter portion 26 can be It can be prevented from rotating by the shear force of time.

  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.

1 Newly-built frame, 2 Existing frame, 10 Joint structure, 20 Anchor, 22, 24 Small diameter part, 26 Large diameter part

Claims (3)

It is a joint structure between a new structure and an existing structure in which an anchor is embedded in a joint portion between the new structure and the existing structure,
The anchor is
A pair of deformed reinforcing bars, one fixed to the new housing and the other fixed to the existing housing;
It is a columnar steel material provided between the pair of deformed reinforcing bars so as to straddle the new casing and the existing casing, and has a larger diameter than the pair of deformed reinforcing bars, and is embedded in the new casing A joining structure of a new housing and an existing housing, which has a large-diameter portion whose length is larger than the depth of embedding in the existing housing. The concrete strength of the new frame is n (≧ 1) times the concrete strength of the existing frame,
The new housing and the existing housing according to claim 1, wherein an embedding depth of the large-diameter portion into the new housing is 3 / n times or more of an embedding depth of the large-diameter portion into the existing housing. Bonding structure. It is a method of joining a new housing and an existing housing in which an anchor is embedded in a joint portion between the new housing and the existing housing,
The anchor is a pair of deformed reinforcing bars and a columnar steel material provided between the pair of deformed reinforcing bars, and includes a thicker portion having a diameter larger than that of the pair of deformed reinforcing bars,
A new installation body and an existing installation that embeds the anchor so as to straddle the new installation body and the existing installation body so that an embedding depth of the large-diameter portion in the new installation body is larger than an embedding depth of the existing housing. Bonding method with the housing.

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