JP2014020072A - Demolition method for pre-stressed concrete beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a demolition method for a pre-stressed concrete beam, capable of demolishing the pre-stressed concrete beam at low cost.SOLUTION: A demolition method for a pre-stressed concrete beam is used for demolishing a pre-stressed concrete beam 10 including a reinforced-concrete beam skeleton 20 and a PC steel wire 21 provided inside the beam skeleton 20, with both ends of the PC steel wire 21 being fixed to both end sides of the beam skeleton 20, respectively. The demolition method includes: a step of providing a lid member 43 for covering a fixing position of the PC steel wire 21 and providing a temporary column 30 for supporting the pre-stressed concrete beam 10 from below; and a step of chipping the pre-stressed concrete beam 10 at an intermediate position A thereof to expose a part of the PC steel wire 21 and cutting the exposed PC steel wire 21.

Description

  The present invention relates to a method for dismantling a prestressed concrete beam. For example, the present invention relates to a method for dismantling a prestressed concrete beam provided in an existing building.

Conventionally, a prestressed concrete beam (hereinafter referred to as a PC beam) is provided in order to build a large space by increasing the distance (span) between columns.
For example, in a post-tension type PC beam, a PC steel wire is passed through the sheath tube inside the beam housing, tension is introduced into the PC steel wire, and in this state, both ends of the PC steel wire are fixed to both ends of the beam. The sheath tube is filled with non-shrink mortar (grout), and a compressive force is introduced into the beam frame in advance. As a result, since the bending strength of the beam can be increased without increasing the weight of the beam, a large span can be realized.

  By the way, the building provided with the PC beam may be dismantled due to circumstances such as aging or rebuilding of the building. In this case, it is necessary to disassemble the PC beam, but since the tension force is introduced into the PC steel wire of this PC beam, if the PC steel wire is cut as it is, the tension force introduced into the PC steel wire is There was a risk that the PC steel wire end and the fixing hardware jumped out to the outside by being released at a stretch.

  Moreover, the crack may arise between PC steel wire and grout by the secular change in the vicinity of the cutting location of PC steel wire. In this case, when the PC steel wire is cut, the PC steel wire may jump out from the cut portion to the outside direction. Moreover, it is difficult to grasp in advance the location and size of such cracks, and as a result, it has not been possible to estimate how much the PC steel wire will jump out.

Thus, it has been proposed to gradually release the tension introduced into the PC steel wire using a tension release device (see Patent Document 1).
That is, the tension release device includes two steel blocks, a PC steel rod inserted through a connection hole between the two steel blocks, and a center hole jack that moves the steel block along the PC steel rod. Prepare.
First, a tension release device is set on the PC steel wire, and two places of the PC steel wire are held by the first steel block and the second steel block.

Next, the center hole jack is driven to bring the steel blocks closer together. Then, the tension of the PC steel wire is borne by the steel block and the center hole jack, and the tension of the PC steel wire between the steel blocks decreases.
Next, cut the PC steel wire between the steel blocks. Thereafter, the center hole jack is driven to gradually separate the steel blocks, thereby gradually releasing the tension introduced into the PC steel wire.

JP 2011-190616 A

  However, when the PC steel wire is provided in the PC beam over the entire length, the PC steel wire is stretched over a predetermined length by a suspending operation or the like in order to attach the tension releasing device to the PC steel wire. It was necessary to expose completely. Therefore, there has been a problem that large-scale construction is required and the construction cost increases.

  It is an object of the present invention to provide a prestressed concrete beam disassembly method capable of disassembling the prestressed concrete beam at a low cost when a tension member is provided over the entire length inside the beam frame of the prestressed concrete beam. To do.

  The method for disassembling a prestressed concrete beam according to claim 1 includes a reinforced concrete beam frame (for example, a beam frame 20 described later) and a tension member (for example, a PC steel wire 21 described below) provided inside the beam frame. ), And a dismantling method of a prestressed concrete beam (for example, a prestressed concrete beam 10 to be described later) in which both ends of the tendon are fixed on both ends of the beam frame, and covers the fixing part of the tendon A step of providing a cover member (for example, a cover member 43 described later) and a temporary column (for example, a temporary column 30 described later) for supporting the prestressed concrete beam from below, and specifying the length direction of the prestressed concrete beam A step of exposing a portion of the tendon material through a position (for example, an intermediate position A described later) and cutting the exposed tendon material , Characterized in that it comprises a.

According to this invention, for example, a lid member that covers a fixing portion of a tendon is provided for a post-tension type prestressed concrete beam. Therefore, when the tendon is cut, the tension force introduced into the tendon is released at once, and the end of the tendon jumps out from the fixing portion and collides with the lid member. Thus, when a tension material collides with a cover member, the momentum of a tension material can be reduced significantly.
Therefore, even if the tendon is cut, the end of the tendon can be prevented from jumping out of the building, so that the PC beam can be safely recovered.

Moreover, since the compressive force applied to the PC beam is released at once when the tendon is cut, the PC beam may be bent downward and collapse due to the load on the upper floor. In view of this, provisional columns for supporting the PC beam from below are provided, so that the PC beam can be prevented from collapsing.
Thus, since it is only necessary to provide the lid member and the temporary pillar, the PC beam can be disassembled by a simple method, and the cost is reduced.

  According to a second aspect of the present invention, there is provided a method for disassembling a prestressed concrete beam, wherein the lid member is provided so as to be opened and closed.

After the tension material collides with the lid member, the tension material may bounce back and damage the temporary material such as the scaffold material.
However, according to this invention, the lid member is provided so as to be openable and closable. Therefore, when the tendon is cut, the end of the tendon collides with the lid member, and the lid member is pushed and rotated by the impact of the tendon. Therefore, the moment of the tension member can be absorbed by the rotation of the lid member, and the tension member can be prevented from colliding with the lid member and bounced back, so that the temporary member such as the scaffold member can be prevented from being damaged.

  The prestressed concrete beam disassembling method according to claim 3 is provided with a protective member (for example, a protective panel 42 described later) that covers the lid member at a predetermined distance from the lid member before cutting the tendon. It is characterized by keeping.

  According to the present invention, since the protective member for covering the lid member is provided, even if the tension member collides with the lid member, even if the momentum jumps out of the lid member without much reduction, Since the tendon that has collided with the protective member stops, the tendon can be collected more safely.

  The method for disassembling a prestressed concrete beam according to claim 4 comprises a reinforced concrete beam housing and a tension member provided inside the beam housing, and tension force is introduced into the beam housing by the tension material. A method of disassembling a prestressed concrete beam, comprising a step of providing a temporary column for supporting the prestressed concrete beam from below, and a part of the tension material with a specific position in the length direction of the prestressed concrete beam. Exposing and cutting the exposed tendon.

  According to the present invention, the same effect as that of the first aspect can be obtained with respect to the prestressed prestressed concrete beam.

  According to the present invention, the lid member covering the fixing portion of the tendon is provided so as to be openable and closable. Therefore, when the tendon is cut, the tension force introduced into the tendon is released at once, and the end of the tendon jumps out from the fixing portion and collides with the lid member. The lid member is pushed by the impact of the tension material colliding and rotates in the opening direction. On the other hand, the momentum of the tendon material is greatly reduced by colliding with the lid member. Therefore, even if the tendon is cut, the end of the tendon can be prevented from jumping out of the building, so that the PC beam can be safely recovered. Moreover, since the compressive force applied to the PC beam is released at once when the tendon is cut, the PC beam may be bent downward and collapse due to the load on the upper floor. In view of this, provisional columns for supporting the PC beam from below are provided, so that the PC beam can be prevented from collapsing. Thus, since it is only necessary to provide the lid member and the temporary pillar, the PC beam can be disassembled by a simple method, and the cost is reduced.

It is sectional drawing of the existing building demolished using the disassembly method of the PC beam which concerns on one Embodiment of this invention. FIG. It is a flowchart of the procedure which demolishes the existing building which concerns on the said embodiment. It is a figure for demonstrating the procedure which demolishes the existing building which concerns on the said embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of an existing building 1 to be demolished using a PC beam demolishing method according to an embodiment of the present invention.
This existing building 1 has four stories. The second floor beam, the third floor beam, the fourth floor beam, and the R floor (roof floor) floor beam of the existing building 1 are post-tensioned prestressed concrete beams (PC beams) 10, respectively.
Among them, the PC beams 10 on the third floor, the fourth floor, and the R floor are supported by the outer peripheral pillars 11 of the existing building at both ends, so that the second floor, the third floor, and the fourth floor are large spans. It is a pillarless space.
On the other hand, the PC beam 10 on the second floor is supported by the outer peripheral column 11 at both ends, and is supported by the intermediate column 12 at substantially the center.

  Each PC beam 10 includes a reinforced concrete beam frame 20 and three PC steel wires 21 as tension members provided inside the beam frame 20. Both ends of these PC steel wires 21 are fixed to both ends of the beam frame with fixing hardware 22, and the fixing hardware 22 is exposed on the outer wall surface 2 of the existing building 1.

Hereinafter, the procedure for dismantling the existing building 1 will be described with reference to the flowchart of FIG.
In step S1, an external scaffold 40 is installed around the existing building 1 as shown in FIG. The external scaffold 40 includes a frame scaffold 41 and an aluminum protection panel 42 as a protection member attached to the outside of the frame scaffold 41. This protective panel 42 is provided to prevent the dismantling material from scattering and to prevent noise leakage during dismantling.

  In step S <b> 2, temporary pillars 30 that support the PC beam 10 from below are installed on two floors of the existing building 1. This temporary pillar 30 is installed at the same position on the upper and lower floors, and the load on the temporary pillar 30 on the upper floor is supported by the temporary pillar 30 on the lower floor.

In step S3, for each of the fixing hardware 22 exposed on the outer wall surface 2 of the existing building 1, as shown in FIG. 3, a plate material such as a panel is used as the lid member 43, and the lid member 43 is fixed to the fixing hardware 22. Attach to the external scaffold 40 to cover. That is, the outer wall surface 2 of the existing building 1 corresponds to both ends of the beam housing 20, and the plate-like lid member 43 is substantially orthogonal to the beam axis direction of the PC beam 10.
Specifically, the single pipe pipe 44 is attached to the frame scaffold 41 substantially horizontally, and the lid member 43 is bound to the single pipe pipe 44 with a number line. Thereby, the cover member 43 is attached to the frame scaffold 41 so that opening and closing is possible.
Further, the protective panel 42 facing the fixing hardware 22 is separated from the lid member 43 by a predetermined distance and covers the lid member 43.

  In step S4, the PC steel wire 21 is exposed at the intermediate position A in the length direction by exposing the PC steel wire 21, and the exposed PC steel wire 21 is cut. Then, the tension force introduced into the PC steel wire 21 is released all at once, and the end portion of the PC steel wire 21 and the fixing hardware 22 jump out from the fixing portion and collide with the lid member 43. The lid member 43 is pushed by an impact that has collided with the PC steel wire 21, and rotates in the opening direction (that is, the direction indicated by the arrow in FIG. 3). On the other hand, the momentum of the PC steel wire 21 is greatly reduced by colliding with the lid member 43.

  In step S5, the existing building 1 is demolished in order from the R floor to the lower floor.

According to this embodiment, there are the following effects.
(1) Since the lid member 43 covering the fixing portion of the PC steel wire 21 is provided, when the PC steel wire 21 is cut, the end portion of the PC steel wire 21 protruding from the fixing portion and the fixing hardware 22 are attached to the lid member 43. The momentum is greatly reduced by collision. Therefore, even if the PC steel wire 21 is cut, it is possible to prevent the end portion of the PC steel wire 21 from jumping out of the existing building 1, so that the PC beam 10 can be recovered safely.

Further, when the PC steel wire 21 is cut, the compressive force applied to the PC beam 10 is released at once, so that the PC beam 10 may be bent downward due to the load on the upper floor and collapse. Therefore, since the temporary column 30 that supports the PC beam 10 from below is provided, the PC beam 10 can be prevented from collapsing.
Thus, since it is only necessary to provide the lid member 43 and the temporary pillar 30, the PC beam 10 can be disassembled by a simple method, and the cost is reduced.

  (2) The lid member 43 is provided so that it can be opened and closed. Therefore, when the PC steel wire 21 is cut, the end portion of the PC steel wire 21 and the fixing hardware 22 collide with the lid member 43, and the impact of the PC steel wire 21 causes the lid member 43 to be pushed and rotated to open. . Therefore, since the moment of the PC steel wire 21 is absorbed by the rotation of the lid member 43 and the PC steel wire 21 can be prevented from colliding with the lid member 43 and rebounding, temporary materials such as scaffolding materials are damaged. Can be prevented.

  (3) Since the protective panel 42 that covers the lid member 43 is provided, even if the PC steel wire 21 collides with the lid member 43, the momentum does not decrease so much and it jumps out of the lid member 43. Since the protruding PC steel wire 21 collides with the protective panel 42 and stops, the PC steel wire 21 can be recovered more safely.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in the above-described embodiment, the frame scaffold 41 is provided outside the existing building 1, and the lid member 43 and the protective panel 42 are provided on the frame scaffold 41. The PC beam 10 may be disassembled by providing a scaffold, a lid member, and a protection panel.

  Further, in the present embodiment, the present invention is applied to the post-tension type prestressed concrete beam 10. However, the present invention is not limited to this, and can also be applied to a pre-tension type prestressed concrete beam.

A ... Intermediate position 1 ... Existing building 2 ... Outer wall surface 10 ... PC beam 11 ... Peripheral column 12 ... Intermediate column 20 ... Beam frame 21 ... PC steel wire (tension material)
22 ... Fixing hardware 30 ... Temporary pillar 40 ... External scaffold 41 ... Frame scaffold 42 ... Protective panel (protective member)
43 ... Lid member 44 ... Single pipe

Claims (4)

A method for dismantling a prestressed concrete beam comprising a reinforced concrete beam housing and a tension member provided inside the beam housing, wherein both ends of the tension member are fixed to both ends of the beam housing,
Providing a lid member for covering the fixing portion of the tendon, and providing a temporary column for supporting the prestressed concrete beam from below;
A method of disassembling the prestressed concrete beam, comprising: exposing a part of the tendon material at a specific position in a length direction of the prestressed concrete beam, and cutting the exposed tendon material. .   The method of disassembling a prestressed concrete beam according to claim 1, wherein the lid member is provided so as to be openable and closable.   The method for disassembling a prestressed concrete beam according to claim 1 or 2, wherein a protective member that is separated from the lid member by a predetermined distance and covers the lid member is provided before the tendon is cut. A method for dismantling a prestressed concrete beam comprising a reinforced concrete beam frame and a tension member provided inside the beam frame, wherein tension force is introduced into the beam frame by the tension member,
Providing a temporary column for supporting the prestressed concrete beam from below;
A method of disassembling the prestressed concrete beam, comprising: exposing a part of the tendon material at a specific position in a length direction of the prestressed concrete beam, and cutting the exposed tendon material. .

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