Method for reinforcing existing beam

Abstract

To provide a reinforcing method of an existing beam capable of easily reinforcing the existing beam of reinforced concrete construction or reinforced steel frame concrete construction of an existing building.SOLUTION: A method for reinforcing existing beams 10 of a reinforced-concrete structure or a reinforced-steel-frame concrete structure of an existing building, the method comprising: a chipping step of chipping a part of an existing concrete portion 14 of a lower portion of the existing beams 10 to form a chipped portion 14d where an existing internal reinforcing bar 15 is exposed; a reinforcing bar joining step of disposing a new internal reinforcing bar 18 below the exposed existing internal reinforcing bar 15 and joining the new internal reinforcing bar 18 to the existing internal reinforcing bar 15; and a new concrete portion placing step of placing a new concrete portion 17 so as to fill the chipped portion 14d and cover the new internal reinforcing bar 18.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for reinforcing existing beams of reinforced concrete or reinforced steel-framed concrete structures in existing buildings. [Background technology]

[0002] For example, when constructing a new building such as an office building, hotel, or apartment building, it has been proposed to reuse the underground structure and foundation structure of an existing building and construct the new building on top of it, thereby shortening the construction period and reducing costs associated with constructing the new building (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-142687 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the new building is larger than the existing building, the existing beams of reinforced concrete or reinforced steel concrete that make up the underground structure or foundation of the existing building may not be strong enough, and in this case, there is a problem in that it is not easy to reinforce the existing beams.

[0005] The present invention has been made in consideration of such problems, and its purpose is to provide a method for reinforcing existing beams that can easily reinforce existing beams made of reinforced concrete or reinforced steel concrete in existing buildings. [Means for solving the problem]

[0006] The method for reinforcing an existing beam of the present invention is a method for reinforcing an existing beam of an existing building made of reinforced concrete or reinforced steel concrete, and is characterized by comprising: a chipping process in which a portion of the existing concrete section at the bottom of the existing beam is chipped away to form a chipped section in which the existing internal reinforcing bars are exposed; a reinforcing bar joining process in which new internal reinforcing bars are placed below the exposed existing internal reinforcing bars and joined to the existing internal reinforcing bars; and a new concrete section pouring process in which new concrete sections are poured to fill the chipped sections and cover the new internal reinforcing bars.

[0007] In the reinforcing method for an existing beam of the present invention, in the above configuration, it is preferable that in the chipping step, the bottom end surface, a portion of the lower side of one side surface, and a portion of the lower side of the other side surface of the existing beam are chipped off to expose portions of the lower ends of the existing internal reinforcing bars that are arranged as stirrup bars inside the existing concrete section in the chipped portions, and in the reinforcing bar joining step, the portions of the existing internal reinforcing bars that are arranged as stirrup bars are joined to the portions of the existing internal reinforcing bars exposed in the chipped portions. [Effects of the Invention]

[0008] According to the present invention, a method for reinforcing an existing beam can be provided that can easily reinforce existing beams of reinforced concrete or reinforced steel-reinforced concrete structures in existing buildings. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a main part of a building structure including an existing beam reinforced by a method for reinforcing an existing beam according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along the line AA in FIG. [Figure 3] This shows the state of the existing beam before reinforcement, where (a) is a cross-sectional view corresponding to Figure 1, and (b) is a cross-sectional view corresponding to Figure 2. [Figure 4] 1A and 1B show the state of an existing beam in which a chipped portion has been formed by a chipping process, where FIG. 1A is a cross-sectional view corresponding to FIG. 1, and FIG. 2B is a cross-sectional view corresponding to FIG. [Figure 5]This shows the state of the existing beam with the new internal rebar joined below the existing internal rebar through the rebar joining process, where (a) is a cross-sectional view corresponding to Figure 1 and (b) is a cross-sectional view corresponding to Figure 2. [Figure 6] This shows the state of the existing beam after the new concrete portion has been poured to fill the gaps and cover the newly installed internal reinforcing bars during the new concrete portion pouring process. (a) is a cross-sectional view corresponding to Figure 1, and (b) is a cross-sectional view corresponding to Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a method for reinforcing an existing beam according to one embodiment of the present invention will be described in detail with reference to the drawings.

[0011] The building structure 1 shown in Figures 1 and 2 is constructed by reusing the underground structure 2 and foundation structure (not shown) of an existing building, on which the above-ground section (not shown) is built. The underground structure 2 is made of reinforced concrete and is constructed underground together with the foundation structure (not shown).

[0012] The underground structure 2 has an existing beam 10 supported by an existing column 3.

[0013] The existing beam 10 is reinforced by a method for reinforcing an existing beam according to one embodiment of the present invention. More specifically, the existing beam 10 has a beam main body portion 11 and a reinforcing portion 12 integrally provided at the lower end portion of the beam main body portion 11. In this embodiment, the reinforcing portion 12 is provided in a predetermined range from one end of the existing beam 10 connected to the existing column 3 (the right end in FIG. 2 ) to the other end. The beam thickness of the existing beam 10 in the portion where the reinforcing portion 12 is provided is greater than the beam thickness of the existing beam 10 in the portion where the reinforcing portion 12 is not provided. As a result, the existing beam 10 has increased strength against vertical loads in the portion where the reinforcing portion 12 is provided.

[0014] The beam main body portion 11 has an internal steel frame 13, an existing concrete portion 14 covering the internal steel frame 13, and a plurality of existing internal reinforcing bars 15 embedded in the existing concrete portion 14.

[0015] In this embodiment, the inner steel frame 13 is made up of a plurality of equal-leg angle steel pieces arranged in an H-shape. Note that the inner steel frame 13 may also be made up of steel frames of other shapes, such as H-shaped steel.

[0016] The existing concrete portion 14 has a rectangular cross section perpendicular to the horizontal direction in the portion where the reinforcing portion 12 is not provided, and in the portion where the reinforcing portion 12 is provided, a bottom end surface 14a, a part of the lower side of one side surface 14b, and a part of the lower side of the other side surface 14c are chipped away from the portion where the reinforcing portion 12 is not provided, to form a chipped portion 14d. The existing concrete portion 14 may also be configured such that an existing floor (floor slab) 16 is provided integrally therewith.

[0017] The multiple existing internal reinforcing bars 15 include four main reinforcing bars 15a arranged along the longitudinal direction of the beam body portion 11 at four corners inside the existing concrete portion 14, and multiple stirrup reinforcing bars 15b that surround each of the four main reinforcing bars 15a and are arranged at intervals from each other in the longitudinal direction of the beam body portion 11. For convenience, only some of the stirrup reinforcing bars 15b are labeled in FIG. 2. In the portion where the reinforced portion 12 is provided, the two lower main reinforcing bars 15a and some of the lower ends of the multiple stirrup reinforcing bars 15b are arranged in the notched portion 14d. The existing internal reinforcing bars 15 may be configured to include reinforcing bars other than the main reinforcing bars 15a and stirrup reinforcing bars 15b.

[0018] The reinforced portion 12 has a newly constructed concrete portion 17 and a plurality of newly constructed internal reinforcing bars 18 .

[0019] The new concrete section 17 is integrally connected to the underside of the existing concrete section 14, filling in the recess 14d formed in the existing concrete section 14 and covering the multiple newly installed internal reinforcing bars 18. The portion of the existing internal reinforcing bars 15 located in the recess 14d is embedded in the new concrete section 17. The lower end surface 17a of the new concrete section 17 is parallel to and below the lower end surface 14a of the existing concrete section 14, and both side surfaces 17b, 17c of the new concrete section 17 are flush with the corresponding side surfaces 14b, 14c of the existing concrete section 14, respectively. In addition, the front end surface 17d connecting the lower end surface 14a of the existing concrete section 14 and the lower end surface 17a of the new concrete section 17 is parallel to the vertical direction. As a result, the cross section of the existing beam 10, perpendicular to the horizontal direction, at the portion where the beam body section 11 and the reinforcement section 12 are provided, is a vertically elongated rectangle.

[0020] The multiple newly installed internal reinforcing bars 18 include five main reinforcing bars 18a arranged parallel to the main reinforcing bars 15a of the existing internal reinforcing bars 15 inside the newly installed concrete section 17, and multiple U-shaped stirrup reinforcing bars 18b surrounding each of the five main reinforcing bars 18a. For convenience, only some of the stirrup reinforcing bars 18b are labeled in FIG. 2 . The three main reinforcing bars 18a arranged along the lower end face 17a have both ends bent upward along the front end face 17d or the existing column 3. Each stirrup reinforcing bar 18b is welded at both ends on the upper side to the vertically extending portion of the corresponding stirrup reinforcing bar 15b of the existing internal reinforcing bar 15. The newly installed internal reinforcing bars 18 may be configured to include reinforcing bars other than the main reinforcing bars 18a and stirrup reinforcing bars 18b. The number of main reinforcements 18a arranged inside the newly constructed concrete portion 17 is not limited to five, and the number of main reinforcements 18a arranged along the lower end surface 17a is not limited to three.

[0021] As shown in Figure 2, the reinforcement portion 12 may be configured by embedding anchor bolts 4, which are fixed to the existing column 3 by post-construction in order to provide the reinforcement portion 12, in the newly constructed concrete portion 17. This allows the reinforcement portion 12 to be fixed to the existing column 3.

[0022] Next, a procedure for reinforcing the existing beam 10 using the reinforcing method for an existing beam according to this embodiment will be described.

[0023] The existing beam 10 shown in Figure 3 is in a state before reinforcement, i.e., before the formation of the reinforced portion 12. In this state, the existing beam 10 is composed only of the beam body portion 11, the existing concrete portion 14 has a rectangular cross section without the chipped portion 14d (see Figure 1), and the existing internal rebar 15 is entirely buried inside the existing concrete portion 14.

[0024] In the method for reinforcing an existing beam according to this embodiment, first, in the chipping step, a portion of the existing concrete portion 14 at the bottom of the existing beam 10, i.e., the beam body portion 11, shown in Fig. 3 is chipped (scraped) to form a chipped portion 14d in which the existing internal reinforcing bars 15 are exposed in part of the existing concrete portion 14, as shown in Fig. 4. That is, in the chipping step, by chipping off a portion of the bottom of the existing concrete portion 14, a portion of the existing internal reinforcing bars 15 is exposed to the outside of the existing concrete portion 14 at the chipped portion 14d.

[0025] In this embodiment, in the chipping process, the lower end surface 14a, a portion of the lower side of one side surface 14b, and a portion of the lower side of the other side surface 14c within a predetermined range from the existing column 3 of the existing concrete section 14 are chipped away, thereby forming a U-shaped chipped section 14d in the lower portion of the existing concrete section 14 in a cross section viewed from the horizontal direction. As a result, in the chipped section 14d, the two lower main reinforcements 15a and portions of the lower ends of the multiple stirrup reinforcements 15b are exposed from the existing concrete section 14. Note that the horizontally extending portions of the lower ends of the multiple stirrup reinforcements 15b, which are central portions between the two main reinforcements 15a, are not placed in the chipped section 14d but are embedded in the existing concrete section 14. Furthermore, the internal steel frame 13 is not placed in the chipped section 14d but is entirely embedded in the existing concrete section 14.

[0026] Next, as shown in FIG. 5, in the reinforcing bar joining step, new internal reinforcing bars 18 are placed below the existing internal reinforcing bars 15 exposed in the chipped portions 14d, and the new internal reinforcing bars 18 are joined to the existing internal reinforcing bars 15.

[0027] In this embodiment, in the reinforcing bar joining step, both ends on the upper end side of the U-shaped stirrup bars 18b of the new internal reinforcing bars 18 are joined by welding to the vertically extending portions of the plurality of stirrup bars 15b exposed in the chipped portion 14d of the existing internal reinforcing bars 15. In addition, five main reinforcing bars 18a are joined by welding to each of the stirrup bars 18b.

[0028] In this embodiment, in addition to the reinforcing bar joining step, the anchor bolts 4 are fixed to the existing column 3 so as to protrude toward the inside of the stirrup bars 18b.

[0029] Next, as shown in Figure 6, in the new concrete portion pouring process, new concrete portion 17 is poured to fill chipped portion 14d and cover newly installed internal reinforcing bars 18. When poured new concrete portion 17 hardens, reinforced concrete portion 12 having new concrete portion 17 and newly installed internal reinforcing bars 18 is integrally formed at the bottom of reinforced steel concrete beam body portion 11 having internal steel frame 13, existing concrete portion 14, and existing internal reinforcing bars 15, and thus existing beam 10 is reinforced by reinforcing portion 12.

[0030] In this embodiment, the reinforcement portion 12 is fixed to the existing column 3 by embedding the anchor bolt 4 in the new concrete portion 17 in the new concrete portion pouring step.

[0031] As described above, according to the method for reinforcing an existing beam of this embodiment, in the chipping process, a portion of the existing concrete portion 14 at the bottom of the existing beam 10 is chipped away to form a chipped portion 14d that exposes the existing internal reinforcing bar 15; in the reinforcing bar joining process, a new internal reinforcing bar 18 is placed below the exposed existing internal reinforcing bar 15 and joined to the existing internal reinforcing bar 15; and in the new concrete portion pouring process, a new concrete portion 17 is poured to fill in the chipped portion 14d and cover the new internal reinforcing bar 18, thereby integrally forming a reinforced concrete reinforcing portion 12 at the bottom of the beam main body portion 11 and easily reinforcing the existing beam 10.

[0032] Furthermore, in this embodiment, in the chipping process, the lower end surface 14a of the existing beam 10, a portion of the lower side of one side surface 14b, and a portion of the lower side of the other side surface 14c are chipped away to expose a portion of the lower end of the existing internal reinforcing bar 15 arranged as stirrup reinforcing bar 15b inside the existing concrete section 14 in the chipped portion 14d, and in the reinforcing bar joining process, the portion of the existing internal reinforcing bar 15 arranged as stirrup reinforcing bar 18b of the new internal reinforcing bar 18 is joined to the portion exposed in the chipped portion 14d of the existing internal reinforcing bar 15. Therefore, in the chipping process, the range or amount of chipping of the existing concrete section 14 is reduced while the new internal reinforcing bar 18 can be reliably joined to the existing internal reinforcing bar 15, making it possible to reinforce the existing beam 10 more easily.

[0033] The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit and scope of the present invention.

[0034] For example, in the above embodiment, the existing beam 10 to be reinforced is made of reinforced steel concrete, but the existing beam 10 to be reinforced may also be made of reinforced concrete without internal steel frame 13.

[0035] In addition, in the chipping process, a portion of the existing concrete portion 14 at the bottom of the existing beam 10 is chipped away to form a chipped portion 14d so that a portion of the existing internal reinforcing bars 15 is exposed, and the range and shape of the chipped portion 14d can be changed as appropriate.

[0036] Furthermore, the number and arrangement of the existing internal reinforcing bars 15 and the new internal reinforcing bars 18 are not limited to those described above and can be changed as appropriate.

[0037] Furthermore, the joining of the existing internal reinforcing bars 15 and the new internal reinforcing bars 18 is not limited to welding, but may be by other methods such as pressure welding or mechanical joining. [Explanation of symbols]

[0038] 1. Building structure 2 Underground structure 3 Existing pillars 4 anchor bolts 10 Existing beam 11 Beam body part 12 Reinforcement part 13 Internal steel frame 14 Existing concrete section 14a Lower end surface 14b Side 14c side 14d Chipboard 15 Existing internal rebar 15a Main bar 15b Stirrup muscle 16 Existing floor 17 Newly constructed concrete section 17a Lower end surface 17b Side 17c side 17d Front end 18 Newly installed internal rebar 18a Main bar 18b Stirrup muscle

Claims

1. A method for reinforcing existing beams of reinforced concrete or reinforced steel concrete structures in existing buildings, comprising: a chipping process of chipping a portion of the existing concrete portion at the bottom of the existing beam to form a chipped portion in which the existing internal reinforcing bars are exposed; a reinforcing bar joining process in which a new internal reinforcing bar is placed below the exposed existing internal reinforcing bar and the new internal reinforcing bar is joined to the existing internal reinforcing bar; A method for reinforcing an existing beam, characterized by comprising a step of pouring a new concrete section to fill the recessed section and to cover the newly installed internal reinforcing bars.

2. In the chipping step, the lower end surface, a portion of the lower side of one side surface, and a portion of the lower side of the other side surface of the existing beam are chipped to expose a portion of the lower end side of the existing internal reinforcing bar arranged as a stirrup reinforcing bar inside the existing concrete part in the chipped portion, 2. The reinforcing method for an existing beam according to claim 1, wherein in the reinforcing bar joining step, a portion of the new internal reinforcing bar to be arranged as a stirrup reinforcing bar is joined to the portion of the existing internal reinforcing bar exposed in the chipped portion.

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