KR101244219B1 - Prestressed concrete beam, steel confined prestressed concrete girder using the same and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A steel confined prestressed(SCP) girder thereof and a manufacturing method thereof are provided to minimize the stress loss and to efficiently introduce the prestress to the central area of a concrete beam. CONSTITUTION: A PSC(Prestressed Concrete Beam) includes a beam main body(10), a first fixture(20), a second fixture(30), a first bearing plate(40), a first bearing plate(40), a second bearing plate(50), a first tension member(60) and a second tension member(70). The first fixture is installed on one end of the beam main body. The second fixture is installed on the other end of the beam main body. The first bearing plate is buried in between the center in a longitudinal direction of the beam main body and the second fixture compresses the beam main body in a longitudinal direction. The second bearing plate is buried in between the center in a longitudinal direction of the beam main body and the first fixture compresses the beam main body in a longitudinal direction. The first tensile member is connected in between the first fixture and the first bearing plate and provides compression stress on the central area of the lower part of the beam main body. The second tensile member is connected between the second fixture and the second bearing plate and provides a compression stress on the center area of the lower part of the beam main body.

Description

PS beam, SCC girder using the same and manufacturing method thereof {PRESTRESSED CONCRETE BEAM, STEEL CONFINED PRESTRESSED CONCRETE GIRDER USING THE SAME AND MANUFACTURING METHOD THEREOF}

The present invention relates to a PS beam (hereinafter referred to as 'PSC beam'), SPC girder (hereinafter referred to as 'SCP girder') using the same and a method of manufacturing the same, and more particularly to the concrete generated by the tensile stress The present invention relates to a PSC beam and an SCP girder in which the PSC beam is embedded, and a method of manufacturing the same.

Concrete has a disadvantage in that tensile strength is relatively lower than compressive strength. Therefore, in order to offset the tensile stress generated in the tensile region, when the concrete beam (Beam) or girder (Girder) is manufactured to the tensile material to the concrete to be able to resist the tensile stress.

1 is a perspective view of a conventional PSC beam. As shown in FIG. 1, the conventional PSC beam fixes the tension member 2 in the longitudinal direction of the concrete beam 1, and introduces a compressive stress to the concrete beam 1 by tensioning the tension member 2 to the tensile stress. Make it resistant. However, since the conventional PSC beam introduces tensile stress throughout the concrete beam 1 by tensioning the tension member 2 at both ends of the concrete beam 1, both ends of the concrete beam 1 in which the tensile stress is weakly generated. Excessive compressive stress is applied to the, there is a problem that can not apply as much compressive stress as necessary in the central region of the concrete beam (1) where the tensile stress is strongly generated. In addition, since the tension member 2 is required at least as long as the concrete beam 1, there is a problem in that the consumption amount of the tension member 2 is large.

This will be described in more detail.

First, the principle of prestress introduction of a PSC beam will be briefly described. Assuming that a certain distributed load is applied to the concrete beam 1 as shown in FIG. 2 (a), the moment acting along the longitudinal direction of the concrete beam 1 is the concrete beam 1 as shown in FIG. 2 (b). In the central region of

과 같다 (여기서, M은 모멘트, y는 중립축에서부터 높이, I는 빔의 단면 2차 모멘트이다). 따라서 인장응력의 최대치는 콘크리트 빔(1)의 하단에서 발생되며, 이러한 인장응력은 모멘트에 비례하기 때문에 콘크리트 빔(1)의 길이방향을 따라 발생되는 인장응력(σ)은 도 3과 같다.Assuming that only a pure moment acts on a cross section of the concrete beam 1, compressive stress is generated above the neutral axis of the concrete beam 1, and tensile stress is generated below the neutral axis.

(Where M is the moment, y is the height from the neutral axis, and I is the cross-sectional secondary moment of the beam). Therefore, the maximum tensile stress is generated at the bottom of the concrete beam (1), the tensile stress (σ) generated along the longitudinal direction of the concrete beam (1) is as shown in Figure 3 because the tensile stress is proportional to the moment.

Meanwhile, as shown in FIG. 4, when the tension member 2 is embedded in the longitudinal direction of the concrete beam 1 and tensioned at both ends of the concrete beam 1, the compressive force applied to the concrete beam 1 is Since it occurs at a uniform level throughout the longitudinal direction of the concrete beam 1, the tensile force in the central region of the concrete beam 1 can be reduced, but on the contrary, the compressive force is increased at both ends of the concrete beam 1.

This does not take into account the stress loss, and considering the stress loss that increases toward the middle of the tension member 2, the longer the length of the tension member 2 to offset the tensile force generated in the longitudinal central region of the concrete beam (1) At both ends of the concrete beam 1, the tensile strength of the tension member 2 should be further increased, which is necessary to increase the compressive strength of the concrete beam 1 as a whole in order to offset the tensile force generated in the longitudinal central region of the concrete beam 1. Very inefficient. That is, the conventional PSC beam which embeds and tensions the tension member 2 over the entire longitudinal direction of the concrete beam 1 has a concrete beam 1 in order to offset the tensile force generated in the longitudinal central region of the concrete beam 1. It is necessary to introduce a relatively large amount of prestress in the whole, which causes a problem in that extreme loads are caused at both ends of the concrete beam 1.

The present invention has been made to solve the above problems, the problem to be solved in the present invention, PSC beam, SCP girder using the same and a method for manufacturing the prestress effectively introduced into the central area of the concrete beam while minimizing the stress loss To provide.

In addition, another problem to be solved in the present invention is to reduce the use of the tension material.

PSC beam according to the present invention for solving the above problems is the beam body; A first fixture installed at one end of the beam body; A second fixture installed at the other end of the beam body; A first acupressure plate buried under the neutral axis of the beam main body and positioned between the longitudinal center of the beam main body and the second fastener; A second acupressure plate buried under the neutral axis of the beam main body and positioned between the longitudinal center of the beam main body and the first fastener; A first tension member connected between the first fixture and the first pressure plate; And a second tension member connected between the second fixture and the second pressure plate.

In addition, SCP girder according to the present invention is a PSC beam according to the present invention; And a steel girder accommodating the PSC beam therein.

In addition, the manufacturing method of the PSC beam according to the present invention comprises the steps of connecting the first fixture and the first pressure plate with a first tension member; Disposing the first fixture at one end of the beam body and disposing the first pressure plate between the longitudinal center of the beam body and the other end of the beam body; Connecting the second fixture and the second pressure plate with a second tension member; Disposing the second fixture at the other end of the beam body, and disposing the second pressure plate between the longitudinal center of the beam body and the first fixture; And tensioning the first and second tension members in the first and second fasteners, respectively, to introduce a compressive stress to a region between the first pressure plate and the second pressure plate of the beam body. .

In addition, the manufacturing method of the SCP girder according to the present invention is a steel girder manufacturing step of producing a steel girder by bending the steel plate; A sheath pipe having a first acupressure plate and a second acupressure plate is installed inside the manufactured steel girder, wherein the first acupressure plate is disposed between the longitudinal center of the steel girder and one end of the steel girder, and the second acupressure plate is Sheath pipe installation step disposed between the longitudinal center of the steel girder and the other end of the steel girder; The girder concrete filling step for placing and curing concrete in the steel girder and the installation and tension step to install a tension wire to apply a compressive force to the concrete by tension after inserting the strand into the sheath pipe.

The PSC beam according to the present invention can effectively prevent the breaking phenomenon generated in the central region of the beam by intensively applying a compressive stress between the first pressure plate and the second pressure plate to cancel the tensile stress of the beam. This allows the state of the PSC beam to remain robust and stable for a long time.

In addition, it is possible to minimize the stress loss while using less tensile material by reducing the length of the tensile material.

In addition, SCP girder according to the present invention, while maintaining the effect of the PSC beam according to the present invention, the steel girders are not easily destroyed even when the ultimate load is generated by restraining the concrete inside.

1 is a perspective view of a conventional PSC beam
2 is a view showing the moment generated in the beam under uniform load
3 is a view showing the tensile stress occurring at the bottom of the beam along the longitudinal direction of the beam;
4 is a view showing a state in which the tensile stress is removed by the introduction of pre-stress in the conventional PSC beam
5 is a perspective view of a PSC beam according to the present invention;
6 is a plan view schematically showing the structure of a PSC beam according to the present invention;
7 is a side view schematically showing the structure of a PSC beam according to the present invention;
8 is a cross-sectional view showing the first and second tension member structure
9 is a graph comparing a state in which tensile stress is removed by prestressing a PSC beam according to the present invention with a conventional PSC beam.
10 is a perspective view of an SCP girder according to the present invention;
11 is an exploded perspective view of the SCP girder according to the present invention
12 is a flowchart illustrating a method of manufacturing a PSC beam according to the present invention.
13 is a flow chart illustrating a method of manufacturing an SCP girder according to the present invention.

Hereinafter, a PSC beam according to the present invention, an SCP girder using the same, and a manufacturing method thereof will be described in detail with reference to the accompanying drawings.

5 is a perspective view of the PSC beam according to the present invention, FIG. 6 is a plan view schematically showing the structure of the PSC beam according to the present invention, and FIG. 7 is a side view schematically showing the structure of the PSC beam according to the present invention.

The PSC beam according to the present invention includes a beam body 10; A first fixture 20 installed at one end of the beam body 10; A second fixture 30 installed at the other end of the beam body 10; A first pressure plate 40 embedded in the beam body 10; A second acupressure plate 50 embedded in the beam body 10; A first tension member 60 connected between the first fixture 20 and the first pressure plate 40; And a second tension member 70 connected between the second fixture 30 and the second pressure plate 50.

The beam body 10 is horizontally disposed on the pillar of the vertical member to support the load. The beam body 10 is made of a concrete material, in the case of the beam body 10 that is usually used for bridges are made of a length of about 45 ~ 70m in the cross-sectional shape of I-type, inverted T-type, box-shaped The shape and length of the beam main body 10 can be variously changed according to its use.

The first fixture 20 and the second fixture 30 are installed at both ends of the beam body 10 in the longitudinal direction. That is, the first fixture 20 is connected to one end of the longitudinal direction of the beam body 10, the second fixture 30 is connected to the other end of the longitudinal direction of the beam body (10).

The first fastener 20 and the second fastener 30 are disposed adjacent to the neutral axis of the beam body 10 to maintain the tension of the first and second tension members 60 and 70 firmly and stably. On the other hand, the first fastener 20 and the second fastener 30 can be selectively applied to various kinds of known.

The first pressure plate 40 is for compressing the beam main body 10 in the longitudinal direction, and is buried between the longitudinal center of the beam main body 10 of the beam main body 10 and the second fixture 30, and the second The pressure plate 50 is for compressing the beam body 10 in the longitudinal direction similarly to the first pressure plate 40, and is embedded between the longitudinal center of the beam body 10 and the first fixture 20. At this time, the first and second acupressure plate (40, 50) should be installed so that the compressive force can be applied to the portion in which the tensile force of the beam body 10 is generated, in the case of the horizontally high beam lower portion of the neutral shaft of the beam body 10 Since the tensile force in the region has a positive value, the first and second acupressure plates 40 and 50 are embedded below the neutral shaft.

The distance between the first fixture 20 and the first pressure plate 40 is to be 0.65 to 0.85 times the length of the beam body 10, and the distance between the second fixture 30 and the second pressure plate 50 is also the beam body ( 10) It is preferred to be 0.65 to 0.85 times the length, but this may be appropriately changed according to the use of the PSC beam according to the present invention and the use environment. In other words, the moment is generated in the longitudinal direction in consideration of the use environment of the designed PSC beam, and then the first pressure plate (A) is positioned at a position capable of appropriately compensating the tensile stress at the bottom of the PSC beam according to the maximum value of the moment and its distribution. By providing the 40 and the second pressure plate 50, the prestress can be introduced more efficiently than the conventional PSC beam in which the tension member is uniformly arranged in the longitudinal direction of the beam.

In addition, since the first and second acupressure plates 40 and 50 are embedded in the beam body 10, there is a risk of inhibiting the stiffness of the cross-sectional shearing force, so that the cross-sections of the first and second acupressure plates 40 and 50 may have a compressive force. It is preferable to form a suitable shape so as not to concentrate on any one of the beam main body 10 to reinforce the cross-sectional loss.

In addition, although only one first tension member 60 and one second tension member 70 are shown in the drawing, the first and second tension members 60 and 60 may be considered in consideration of the limit tensile strength of the tension member and the amount of prestress to be introduced into the PSC beam. 70 may include a plurality.

The PSC beam according to the present invention provides a sufficient compressive stress to the beam body 10 through the first pressure plate 40, the second pressure plate 50, the first tension member 60 and the second tension member 70 as described above. By canceling the tensile stress in the center region, the fracture can be effectively prevented.

The first tension member 60 and the second tension member 70 pull out the first pressure plate 40 and the second pressure plate 50, which are connected thereto by tension, and the area between the first and second pressure plates 40, 50. That is, it serves to provide a compressive stress in the lower central region of the beam body (10). As such, since the first and second tension members 60 and 70 are disposed so as to overlap only the lower center region of the beam body 10, the compressive stress acts on the center region of the beam body 10 more than both ends, thereby causing the moment. Appropriate compensation is provided for the lower portion of the beam main body 10 in which the tensile stress is largely generated, and compressive stress is relatively small on both sides of the beam main body 10 to prevent excessive compensation of the tensile stress. The first tension member 60 is installed through the second pressure plate 50, and the second tension member 70 is installed through the first pressure plate 40.

Although not shown in the drawings, the first and second tension members 60 and 70 may be provided at the ends of the first and second tension members 60 and 70 that penetrate the first and second pressure plates 40 and 50. Fixtures for engaging 40 and 50 may be provided.

FIG. 8 is a cross-sectional view of the first and second tension members, and the first and second tension members 60 and 70 are the sheath tubes 62 and 72 and the strands 64 and 74 disposed inside the sheath tubes 62 and 72. FIG. Is done. At this time, it is preferable that the first and second tension members 60 and 70 do not grout the sheath tubes 62 and 72 so as to freely tension the strands 64 and 74 in the sheath tubes 62 and 72.

The first tension member 60 and the second tension member 70 are arranged side by side in the longitudinal direction of the beam body 10, the interval can be appropriately changed as necessary.

In addition, the profile of the first tension member 60 and the second tension member 70 has a parabolic shape when viewed from the side, so that the moment generated by the distributed load is parabolic along the longitudinal direction of the beam body 10. Is caused. That is, the prestress is concentrated in the center region of the beam main body 10 in which the moment is largely generated, and the prestress is uniformly applied to the cross section of the beam main body 10 in the vicinity of both ends where the moment is small.

9 is a graph comparing a state in which tensile stress is removed by the prestress introduction of a PSC beam according to the present invention with a conventional PSC beam. Figure 9 (a) shows the tensile stress (A), prestress (B) and the final result (A + B) at the bottom of the beam, in the conventional structure in which the fasteners are fixed to both ends of the beam with a tension member therebetween Due to the stress loss, the tensile stress due to prestress decreases gradually toward the center of the beam, and the prestress is minimal in the center of the beam where prestress is most demanded. Therefore, the final result of the lower beam stress due to prestress when tensioning the tension member can be minimized in the middle of the beam. do.

On the other hand, Figure 9 (b) shows the tensile stress (A) at the bottom of the beam, the prestress (C1) of the first tension member, the prestress (C2) of the second tension member, the sum of the prestresses (C = C1 + C2) and the final result (A). + C), in the PSC beam structure according to the present invention, since the maximum position of the stress loss of the two tension members is located at a position other than the center region of the beam, the stress loss is properly distributed so that the center region of the beam having the maximum moment is appropriately distributed. It can be reinforced. In addition, since prestress is intensively applied to the central region of the beam, as shown in FIG. Can be prevented from occurring.

10 is a perspective view of the SCP girder according to the present invention, Figure 11 is an exploded perspective view of the SCP girder according to the present invention.

SCP girder according to the present invention comprises a PSC beam 100 according to the present invention and a steel girder 200 for receiving the PSC beam 100 therein.

Steel girder 200 has a hollow portion formed therein to accommodate the PSC beam 100 according to the present invention, the cross section may be manufactured in various shapes such as I-type, inverted T-type, box-shaped .

At this time, the first pressure plate 40 and the second pressure plate 50 of the PSC beam 100 according to the present invention may be coupled to the inner surface of the steel girder 200 by welding or the like.

Hereinafter will be described a PSC beam and a method of manufacturing the SCP girder using the same according to the present invention.

12 is a flowchart illustrating a method of manufacturing a PSC beam according to the present invention.

① first step (S10): connecting step of the first fixture 20 and the first pressure plate 40

At this time, the first fixture 20 and the first pressure plate 40 are connected to each other through the first tension member (60). That is, one end of the first tension member 60 is fixed to the first fastener 20, and the other end penetrates through the second pressure plate 50 and is connected to the first pressure plate 40.

② second step (S20): the first fixture 20 and the first pressure plate 40 arrangement step

In this case, the first fixture 20 is disposed at one end of the beam body 10, and the first pressure plate 40 is stably disposed in the region between the longitudinal center of the beam body 10 and the second fixture 30. Let's do it.

③ 3rd step (S30): the step of connecting the second fixture 30 and the second pressure plate 50

At this time, the second fixture 30 and the second pressure plate 50 are connected to each other through the first tension member (60). That is, one end of the second tension member 70 is fixed to the second fastener 30, and the other end penetrates through the first pressure plate 40 and is connected to the second pressure plate 50.

④ fourth step (S40): second fixture 30 and the second pressure plate 50 arrangement step

At this time, the second fixture 30 is disposed on the other end of the beam body 10, the second pressure plate 50 is stably disposed in the region between the longitudinal center of the beam body 10 and the first fixture 20. Let's do it.

⑤ fifth step (S50): the first, second tension member (60, 70) tension step

In this case, the first and second tension members 20 and 30 are tensioned by the first and second fasteners 20 and 30 to compress the stress in the region between the first pressure plate 40 and the second pressure plate 50 of the beam body 10. Is introduced. As the first and second tension members 60 and 70, sheath pipes 62 and 72 in which the strands 64 and 74 are embedded are used.

By going through the five steps described above, the manufacturing process of the PSC beam is completed.

On the other hand, the first step (S10) to the fourth step (S40) can be appropriately changed in order according to the manufacturing convenience.

13 is a flowchart illustrating a method of manufacturing an SCP girder according to the present invention.

① Step a (S110): steel girder manufacturing step

Steel girder 200 for SCP girder is formed to bend the plate-shaped steel to fill the inside with a tension member and concrete. In this case, the cross section of the steel girder 200 may be any one of an I-type, an inverted T-type, and a box shape, and other shapes may be appropriately selected depending on the use environment in which the SCP girder is to be installed.

② step b (S120): sheath pipe installation step

Sheath pipes 62 and 72 in which the first pressure plate 40 and the second pressure plate 50 are coupled to one end of the inner hollow portion of the steel girder 200 are installed. At this time, the first pressure plate 40 is disposed between the longitudinal center of the steel girder 200 and one end of the steel girder 200, the second pressure plate 50 is the longitudinal center of the steel girder 200 and the steel girder It is disposed between the other ends of the (200). Step b (S120) is to weld the first acupressure plate 40 and the second acupressure plate 50 to the inner surface of the steel girder 200 in order to ensure safety during the tension work (64, 74) afterwards Combining acupressure plate coupling step (S122) may be included.

③ c step (S130): girder concrete filling step

Concrete is poured and cured inside the steel girders 200 in which the sheath pipes 62 and 72 are installed. According to the manufacturing method of the SCP girder according to the present invention, the steel girders 200, sheath pipes (62, 72), the first and second acupressure plate relatively light in step a (S110) and step b (S120) ( 40, 50) only to be manufactured and transported to the shop floor, step c (S130) can be carried out at the shop floor, the convenience of work and transfer is greatly increased.

④ third step (S140): strand installation and tension step

When the concrete is filled in the steel girder 200 through the c step S130, the strands 64 and 74 are inserted into the sheath pipes 62 and 72 to be tensioned so that the compressive force is applied to the concrete.

⑤ step e (S150): sheath pipe grouting step

Step e is not an essential step, but it is determined that sufficient compressive force is applied to the concrete by the strands 64 and 74, and there is no need to adjust the tensile force of the strands 64 and 74 later. Grouting may be performed on the sheath tubes 62 and 72 for fixing.

10: beam main body 20: first fixture
30: second fixture 40: first pressure plate
50: second pressure plate 60: first tension member
62, 72: sheath pipe 64, 74: strand
70 second tension member 100 PSC beam according to the present invention
200: steel girder

Claims (14)

Beam body 10;
A first fixture 20 installed at one end of the beam body 10;
A second fixture 30 installed at the other end of the beam body 10;
A first acupressure plate 40 embedded in a lower portion of the neutral shaft of the beam main body 10 and positioned between the longitudinal center of the beam main body 10 and the second fixture 30;
A second acupressure plate (50) embedded in a lower portion of the neutral shaft of the beam body (10) and positioned between the longitudinal center of the beam body (10) and the first fixture (20);
A first tension member 60 connected between the first fixture 20 and the first pressure plate 40;
PSC beam, characterized in that it comprises a second tension member (70) connected between the second fixture (30) and the second pressure plate (50).
The method according to claim 1,
The first tension member (60) is installed through the second pressure plate (50), the second tension member (70) is installed through the first pressure plate (40), the PSC beam.
The method according to claim 1,
The first tension member 60 and the second tension member 70 are formed of sheath pipes 62 and 72 and strand wires 64 and 74 disposed inside the sheath pipes 62 and 72, respectively. PSC beam.
The method according to claim 1,
The first tension member (60) and the second tension member (70) is a PSC beam, characterized in that installed in a parabolic form.
PSC beam 100 according to any one of claims 1 to 4 and
SCP girder, characterized in that it comprises a steel girder 200 for receiving the PSC beam 100 therein.
The method according to claim 5,
The steel girder 200 has a hollow portion, the cross section is an SCP girder, characterized in that any one of the I-type, inverted T-type, box type.
The method according to claim 5,
SCP girder, characterized in that the first pressure plate (40) and the second pressure plate (50) of the PSC beam 100 is coupled to the inner surface of the steel girder (200).
Connecting the first fixture 20 and the first pressure plate 40 to the first tension member 60 (S10);
The first fixture 20 is disposed at one end of the beam body 10, and the first pressure plate 40 is disposed between the longitudinal center of the beam body 10 and the other end of the beam body 10. Step S20;
Connecting the second fixture 30 and the second pressure plate 50 with a second tension member 70 (S30);
The second fixture 30 is disposed at the other end of the beam body 10, and the second pressure plate 50 is disposed between the longitudinal center of the beam body 10 and the first fixture 20. Step S40 and
The first and second tension members 60 and 70 are tensioned by the first and second fasteners 20 and 30, respectively, to between the first pressure plate 40 and the second pressure plate 50 of the beam body 10. And introducing a compressive stress into the region (S50).
The method according to claim 8,
The first tension member 60 is installed to penetrate through the second pressure plate 50, and the second tension member 70 is installed to penetrate through the first pressure plate 40. .
The method according to claim 8 or 9,
The first tension member 60 and the second tension member 70 are formed of sheath pipes 62 and 72 and strand wires 64 and 74 disposed inside the sheath pipes 62 and 72, respectively. Method of manufacturing PSC beams.
The method according to claim 8,
The first tension member (60) and the second tension member (70) is a method of manufacturing a PSC beam, characterized in that installed in a parabolic form.
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