JP6979542B1 - Prestressed concrete deck expansion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a prestressed concrete deck slab, which can extend a tension material and expand a concrete deck into which prestress is introduced, without suddenly releasing the tension force of the existing tension material. SOLUTION: This is an expansion method of a concrete deck into which prestress is introduced, and a step of exposing a tension material by sticking concrete of the deck near an end on the expansion side and the exposed tension. The step of attaching the intermediate fixing tool to the material, the step of heating the exposed tension material, the step of cutting the heated tension material, and the step of attaching the connector to the end of the cut tension material and expanding it. The process of dismantling the floor slab on the side of the concrete, the process of connecting the tension material of the expansion part to the connector, the process of placing concrete on the expansion part of the concrete deck, and the concrete of the expansion part that was placed hardened. A method for expanding a prestressed concrete deck, which comprises a step of tensioning the tension material of the expanded portion and introducing prestress into the concrete of the widened portion. [Selection diagram] Fig. 2

Description

The present invention relates to an expansion method for a prestressed concrete deck (PC deck) such as an existing bridge.

When widening an existing bridge, the method described in Patent Document 1 is known as a widening method when the bridge is a PC deck.
The method comprises the following steps.
(A) The concrete of the floor slab is put on to expose the tension material (b) The intermediate fixing tool is attached to the exposed tension material (c) The hung part is backfilled (d) The existing fixing tool is covered. The existing concrete is hung, the existing fixing tool is removed, and the end of the tension material is exposed (e) The connector is attached to the end of the exposed tension material, and the extension tension material is connected (f) Widening. Placing concrete in the part (g) After the cast concrete is hardened, tension force is introduced into the extension tension material and prestress is introduced into the concrete of the widening part. It is possible to widen the bridge while using the above.
Patent Document 2 describes an intermediate fixing tool that can be used in this construction method.

JP-A-2017-193899 Japanese Unexamined Patent Publication No. 2017-186814

In the step (d) described above, when the concrete covering the existing fixing tool is removed by chipping, the cross section of the concrete on the back surface of the bearing plate of the fixing tool is reduced by the chipping, and the bearing stress degree is supported. When the pressure strength is exceeded, the concrete may be crushed or the bearing plate may shift and move, resulting in loss of the fixing function and sudden release of tension.
Since the sudden release of the tension force is accompanied by an impact, when it is transmitted to the intermediate fixing tool, the tensioning material slips and the tension force on the service side is reduced.
When slippage occurs, the wedge-type intermediate fixing tool causes cross-sectional defects due to scraping and rubbing of the tension material, and the fixing performance deteriorates due to the wedge blade spillage. ..
Furthermore, even if an attempt is made to recover the tension on the service side once reduced when the tension material connected for the extension of the widening portion is tensioned, it is almost impossible to know the range of reduction of the tension material due to slipping with impact. Not only is it impossible to obtain the necessary moving tension, but the introduction of excessive tension affects the safety of the concrete, which is prestressed by tension, as well as the tension material itself. To exert.
In addition, such a decrease or recovery of tension, that is, fluctuation of tension, causes the tension to expand and contract, so that the tension causes grout and breakage around it, and the PC tension and concrete are integrated in this part. Will be lost.

INDUSTRIAL APPLICABILITY The present invention is an expansion method for a prestressed concrete deck, which can extend a concrete deck into which prestress is introduced by extending the tension material without suddenly releasing the tension force of the existing tension material. The purpose is to provide.

The first invention of the present application made in order to achieve the above object is an expansion method of a concrete deck in which prestress is introduced, and the concrete of the deck is sewn near the end on the expansion side. A step of exposing the tension material, a step of attaching an intermediate fixing tool to the exposed tension material, a step of heating the exposed tension material, a step of cutting the heated tension material, and a step of cutting the tension material. A step of attaching a connecting tool to the end of the concrete and disassembling the deck on the expanding side, a step of connecting the tension material of the expanding portion to the connecting tool, and the intermediate fixing tool, the connecting tool and the expanding portion. The process of placing concrete on the expanded part of the concrete deck by covering the tension material of the Provided is an expansion method of a prestressed concrete deck, which comprises a step of introducing prestress into the concrete.
The second invention of the present application is an expansion method of a concrete deck in which prestress is introduced, and is a step of exposing a tension material by sticking concrete of an existing deck in a portion remaining after expansion, and exposure. The step of attaching the intermediate fixing tool to the tensioning material, the step of covering the intermediate fixing tool and the exposed tensioning material with a sheath, and the step of backfilling the concrete-covered portion of the floor slab, and the expansion side. A step of exposing the tension material by putting concrete on the floor slab near the end, a step of heating the exposed tension material, a step of cutting the heated tension material, and a step of cutting the tension material. The step of attaching the connecting tool to the end and disassembling the deck on the expanding side, the step of connecting the tensioning material of the expanding portion to the connecting tool, and the step of connecting the connecting tool and the tensioning material of the expanding portion by a sheath. In the process of placing concrete on the expanded part of the concrete deck by covering it, and after the concrete of the placed expansion part is hardened, the tension material of the expanded part is tensioned to introduce prestress to the concrete of the widened part. Provided is an expansion method of a prestressed concrete deck, which comprises a process and.

The present invention can obtain at least one of the following effects by means for solving the above-mentioned problems.
(1) By heating the tension material, the tension force is gradually reduced, and when the tension material is cut, there is no impact due to the sudden release of the tension force.
(2) Since there is no impact due to the sudden release of the tension force, the tension material does not slip in the intermediate fixing tool, and the tension force on the service side does not decrease.

Explanatory drawing of process of expansion method of PC floor slab of 1st Example (1) Explanatory drawing of process of expansion method of PC floor slab of 1st Example (2) Explanatory drawing of process of expansion method of PC floor slab of 1st Example (3) Explanatory drawing of process of expansion method of PC floor slab of 2nd Example (1) Explanatory drawing of process of expansion method of PC floor slab of 2nd Example (2) Explanatory drawing of process of expansion method of PC floor slab of 2nd Example (3)

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Example]
<1> Bridge to which the present invention can be applied The bridge to which the expansion method of the PC floor slab of the present invention can be applied has a concrete floor slab, and tension force is introduced into the tension material arranged in the floor slab. , Prestress is introduced in the concrete deck.
In the embodiment of the present application, the widening of the PC deck in the width direction of the bridge will be described, but the present invention is not limited to this, and the present invention is not limited to this, and can be applied to the expansion of the existing PC deck in the direction in which prestress is introduced. Can be applied.

<2> Exposure of the existing tension material The existing tension material 2a is exposed by squeezing the concrete of the floor slab 1a near the side end of the existing floor slab 1a on the side to be widened (FIG. 1 (a)). ). If the vine position is too close to the existing fixing tool 3a, the tension force introduced into the tensioning material 2a may crush the concrete near the fixing tool 3a to release the tension force, and the prestress of the floor slab 1a may decrease. Therefore, the fishing portion 4 is set at a position away from the fixing tool 3a until the concrete is not crushed by the tension force.
The range of the fishing portion 4 in the direction of the bridge axis is based on the spacing between the tension members 2a, but a plurality of strips may be bundled together in a place where the spacing is narrow, such as at the end of a girder.
The exposed tension material 2a cleans and removes the adhering grout and the like.

<3> Attaching the intermediate fixing tool The intermediate fixing tool 5 is attached to the exposed tension material 2a (FIG. 1 (b)).
The intermediate fixing tool 5 grips the tensioning material 2a and transmits the tensioning force to the floor slab 1a, and the intermediate fixing tool (i-fix (registered trademark)) described in Patent Document 2 described above is preferable. be.

The intermediate fixing tool 5 used in the present invention is composed of a fixing force generating component 5a and an adjusting bearing plate 5b, and in this step, the following two operations are performed to mount the intermediate fixing tool.

<3.1> Mounting of fixing force generating component The fixing force generating component 5a grips the tension material 2a by a built-in wedge and generates a fixing force. The wedge is press-fitted with a force higher than the existing tension force of the tension material 2a, and a sufficient fixing force is generated so that slipping does not occur even if the tension force acts due to the cutting of the tension material 2a.

<3.2> Insertion of the adjusting bearing plate The adjusting bearing plate 5b is inserted between the fixing force generating component 5a and the service side of the deck 1a, and is brought into close contact with both. An adjustment bolt is built in between the two adjustment bearing plates 5b, and by rotating this, the distance between the two adjustment bearing plates 5b is widened and brought into close contact with each other, and the fixing force generated in the fixing force generating component 5a is applied. , Communicate to the service side of the floor slab 1a. When a predetermined torque is introduced into the adjusting bolt during rotation of the adjusting bolt, the two adjusting bearing plates 5b are forcibly expanded and the tension force of the portion is increased. By doing so, the loss of the tension force due to the familiarity of the intermediate fixing tool 5 that occurs when the tension material 2a is cut is corrected, and the tension force on the service side from the intermediate fixing tool 5 is the existing value even after the tension material 2a is cut. Can be maintained.

<4> Heating / cutting of tension material The tension material 2a is heated / cut using the gas cutting device 6 (FIG. 2 (c)).
Heating and cutting are performed by the following two steps.

<4.1> Heating step First, the tension material 2a near the cutting position is heated by the gas cutting device 6.
The gas cutting device 6 can switch the functions of preheating and cutting by changing the supply amounts of acetylene and oxygen.
In this step, the tension material 2a is exposed to the preheating flame to cause thermal expansion and decrease in elongation rigidity, and the tension force is gradually reduced.
The heating range is widened to about twice or more the diameter of the tension material (or the diameter of the bundle when there are a plurality of tension materials) in the length direction of the tension material 2a. The reason is that the temperature of the acetylene flame is as high as about 3000 ° C, and when the flame is concentrated in one place like general gas cutting, the temperature rises rapidly locally, and the tensile strength of the heated part decreases and it breaks. Because there is a fear.
In addition, the decrease in tension due to heating becomes remarkable in the temperature range of 450 ° C to 550 ° C. Therefore, as a guideline for heating work, a dark red heating color (about 600 ° C) is applied to the surface of the tension material 2a from the start of heating. ) Appears, widen the heating range to slow down the heating rate, and after the heating color appears, narrow the heating range slightly and heat further, and finally the heating color is orange (about 700 ° C). ), The tension becomes almost 0 kN.

<4.2> Cutting step The tension material 2a is fused by increasing the supply amount of oxygen (FIG. 2 (d)). The tension material 2a, which has been sufficiently heated in the heating step and whose tension has been reduced, can be easily cut without impact.
Since there is no impact due to the sudden release of the tension force, the tension material 2a does not slip on the intermediate fixing tool 5, and the tension force on the service side does not decrease.
Further, both the heating step and the cutting step are only heated and cut by the gas cutting device 6, and can be easily performed without any danger.

<5> Attaching the connecting tool After the cutting of the tensioning material 2a is completed, the tensioning material 2a is cut off leaving the extra length required for attaching the connecting tool (FIG. 3 (e)), and the connecting tool 7 is attached (FIG. 3 (e)). FIG. 3 (f). At the same time, in order to construct the floor slab of the expanded portion, the existing floor slab 1a on the side to be expanded is dismantled and the end portion is shaped.

<6> Construction of expansion part Finally, in order to construct the expansion part 1b of the floor slab, the formwork is assembled and the reinforcement is arranged. Since the intermediate fixing tool 5 and the connecting tool 7 are accommodated in the expansion portion 1b of the floor slab, not only the tension material 2b of the expansion portion but also the intermediate fixing tool 5 and the connecting tool 7 are covered by the sheath 8. When the expansion portion is constructed by the precast member, the intermediate fixing tool 5 and the connecting tool 7 are embedded in the filling portion between the existing portion 1a and the expansion portion 1b, so that the formwork of that portion is assembled and arranged. Arrange the muscle and sheath 8.
Next, the tension material 2b of the expansion portion is inserted into the sheath, connected to the connector 7, and then the concrete of the expansion portion is placed.
Then, when the cast concrete is hardened and reaches a strength that allows tension, the tension material 2b of the expansion portion is tensioned using a jack and fixed by the fixing tool 3b of the expansion portion, thereby fixing the expansion portion of the floor slab. Prestress is introduced into 1b and integrated with the existing portion 1a (FIG. 3 (g)). After the tension is complete, grout is injected and the construction of the expansion is completed. When a pre-grout steel material is used for the tension material 2b of the extended portion, the grout after the tension of the portion is completed can be omitted.

[Second Example]
In the above-mentioned first embodiment, the intermediate fixing of the tension material 2a and the connection of the tension material 2b were performed within the range of the hanging portion 4 at one place. It may not be possible to provide a fishing range just for fixing and connecting.
In such a case, the fishing range is set to two points and the procedure is as follows.

<1> Exposure of the existing tension material The existing tension material 2a is exposed by sticking the concrete of the existing floor slab 1a (FIG. 4A). The position of the chipping portion 4 is a position that remains after the expansion portion is constructed, away from the existing fixing tool 3a. The range of the chipping portion 4 is based on the spacing between the tension members 2a, but a plurality of strips may be bundled together in a place where the spacing is narrow, such as at the end of a girder.
The exposed tension material 2a cleans and removes the adhering grout and the like.

<2> Attaching the intermediate fixing tool The intermediate fixing tool 5 is attached to the exposed tension material 2a (FIG. 4 (b)).
The intermediate fixing tool 5 transmits the tension force of the tensioning material 2a to the floor slab 1a, and the intermediate fixing tool described in Patent Document 2 described above is suitable.
The intermediate fixing tool 5 is fixed to the service side of the fishing portion 4 to correct the increase in tension.

<3> Backfilling of the hanging part and exposure of the cutting part The hanging part 4 is backfilled, and the cutting part 9 with the concrete of the existing floor slab 1a placed near the fixing group with the existing fixing tool 3a. The existing tension material 2a is exposed at (FIG. 5 (c)).
Since the chipping range of the chipping portion 9 for cutting is near the fixing end, its size and position are set so as not to affect the concrete stress as much as possible.

<4> Cutting the tension material The tension material 2a is cut at the fishing portion 9 for cutting (FIG. 5 (d)).
This step is performed in the same manner as the step of cutting the tension material of the first embodiment.
After that, excision of the tension material 2a, dismantling of the existing deck 1a, shaping of the end portion (FIG. 6 (e)), attachment of the fitting and construction of the extended portion (FIG. 6 (f)) are referred to as the first embodiment. Do the same.

1a: Existing floor slab, 1b: Floor slab expansion part 2a: Existing tension material, 2b: Expansion part tension material 3a: Existing fixing tool, 3b: Expansion part fixing tool 4: Fishing part 5: Intermediate fixing Tool 6: Gas cutting device 7: Connecting tool 8: Sheath 9: Cutting part

Claims (2)

It is an expansion method for concrete decks with prestress introduced.
The process of exposing the tension material by sticking the concrete of the floor slab near the end on the expanding side,
The process of attaching the intermediate fixing tool to the exposed tension material, and
The process of heating the exposed tension material and
The process of cutting the heated tension material and
A process of attaching a connector to the end of the cut tension material and disassembling the deck on the expanding side, and
The process of connecting the tension material of the expansion part to the connector and
A step of covering the intermediate fixing tool, the connecting tool, and the tension material of the expanding portion with a sheath , and placing concrete on the expanding portion of the concrete deck.
It is characterized by including a step of tensioning the tension material of the extended portion and introducing prestress into the concrete of the widened portion after the concrete of the cast extended portion is hardened.
Expansion method for prestressed concrete decks. It is an expansion method for concrete decks with prestress introduced.
The process of exposing the tension material by peeling the concrete of the existing floor slab that remains after expansion,
The process of attaching the intermediate fixing tool to the exposed tension material, and
A step of covering the intermediate fixing tool and the exposed tension material with a sheath and backfilling the concrete-covered portion of the deck.
The process of exposing the tension material by sticking the concrete of the floor slab near the end on the expanding side, and
The process of heating the exposed tension material and
The process of cutting the heated tension material and
A process of attaching a connector to the end of the cut tension material and disassembling the deck on the expanding side, and
The process of connecting the tension material of the expansion part to the connector and
A process of covering the fitting and the tension material of the expansion portion with a sheath and placing concrete on the expansion portion of the concrete deck.
It is characterized by including a step of tensioning the tension material of the extended portion and introducing prestress into the concrete of the widened portion after the concrete of the cast extended portion is hardened.
Expansion method for prestressed concrete decks.

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