KR100811203B1 - Prestressed composite beam - Google Patents

Abstract

A prestressed composite beam is provided to manufacture a steel-concrete composite beam economically by prestressing to a steel-concrete composite beam and minimizing the use of subsidiary materials, and to make quality control easy by distributing prestress to steel materials evenly. A prestressed composite beam is manufactured by composing steel materials(100) and concrete, wherein buried reinforcement materials(200) projected upward are formed on the upper parts of the steel materials to be buried in a slab to have a variable cross section decreasing toward two ends from the center according to stress, and the concrete is formed to cover the lower part of the steel materials from the center of a steel-concrete composite beam and formed to have a variable cross section increasing toward two ends to cover the lower part and the web of the steel materials, and the prestress is introduced to the steel-concrete composite beam in a parabolic shape via the center from two ends of the steel-concrete composite beam by tension members(400) formed in the concrete. In addition, many stress guide blocks(500) are installed to inner webs of the steel materials according to the arrangement of the tension member to set up the tension members smoothly in a parabolic shape and to disperse and transfer the tensile force to the concrete and the webs of the steel materials to prevent the partial stress concentration of the steel-concrete composite beam caused by compression prestress effectively.

Description

Prestressed Steel Composite Beam {PRESTRESSED COMPOSITE BEAM}

1A, 1B, 1C and 1D illustrate examples of conventional prestressed rigid composite beams.

Figure 2a shows the steel constituting the steel, U-shaped prestressed steel composite beam according to Embodiment 1 of the present invention,

2B illustrates another U-shaped prestressed rigid composite beam and cross-sectional views thereof according to Embodiment 1 of the present invention;

2C is a variation of Embodiment 1 of the present invention.

3A, 3B, 3C, and 3D illustrate a steel material, an installation form of a buried reinforcement material, and an I-type prestressed steel composite beam according to Embodiment 2 of the present invention.

<Description of the symbols for the main parts of the drawings>

100: steel 200: buried reinforcement

300: concrete 400: tension material

500: stress transfer guide block 600: slab

The present invention relates to a prestressed rigid composite beam. More specifically, the present invention relates to a prestressed steel composite beam (girder) for bridges in which steel and concrete are synthesized, but a tension material is settled after tension in the concrete so that compression prestress is introduced.

Conventional bridge girders have been introduced a number of pre-stressed composite beams made to introduce the compression prestress by the tension material disposed in the concrete of the lower cross-section (eg RPF composite beams, MSP composite beams, precom steel Composite beams, etc.)

The steel material 10 used in such a steel composite beam is generally formed of an upper flange 11, an abdomen 12, and a lower flange 13 as an I-shaped cross section as shown in FIG. 1A.

The concrete 20 is formed to surround the lower flange 13 (lower flange concrete) so that the steel 10 and the concrete 20 are synthesized with each other, but the lower flange concrete has a tension member 30 such as a PC strand. The pre-stress is introduced in advance by buried by tension and fixation.

At this time, the abdomen 12 and the upper flange 11 of the steel is exposed to the outside when not forming a separate concrete, so that the concrete is applied to the abdomen and the upper flange of the steel for maintenance, the upper flange 11 Is formed to be embedded in the slab 40, the bottom plate.

However, since the concrete 20 formed on the abdomen and the upper flange of the steel has almost no load-sharing structurally, the functional problems have been pointed out by increasing the self-weight of the steel composite beam and causing cracking.

In addition, in the case of the tension member 30 is installed so that the formation height is embedded in the lower flange concrete 20, there is no choice but to follow the straight arrangement form,

In this case, it was pointed out that both ends of the lower flange concrete may cause compression cracking due to excessive tension.

That is, in the steel composite beam made of the lower flange concrete and the steel as shown in (a) of Figure 1b by placing a tension member in a straight form on the lower flange concrete,

As shown in (b) of FIG. 1B, a predetermined compressive stress (+) is introduced into the rigid composite beam by the tension member.

At this time, if the compressive stress (+) introduced into the rigid composite beam is roughly formulated and displayed,

(P / A + (Pe) y / I)

Where A is the cross-sectional area of the composite beam

P: Tension (prestressing force) by tensioning material

e: Distance from the neutral axis of the steel composite beam to the tension material center (eccentricity)

y: distance from the neutral axis of the steel composite beam to the podium

I: Cross section secondary moment of steel composite beam

to be.

In addition, a tensile stress (-) is generated in the steel composite beam due to the self-weight of the steel and the self-weight of the lower flange concrete. When the tensile stress (-) is formulated and examined, as shown in FIG.

-Mdy / I

Here, Md: bending moment due to the weight of steel and lower flange concrete

I: Cross section secondary moment of steel composite beam

y: distance from the neutral axis of the composite beam to the podium.

According to FIG. 1B (d), which shows the stress acting on the final composite beam, despite the fact that a significant magnitude of compressive stress is introduced at both ends of the composite beam, unlike the central portion of the composite composite beam,

In general, the compressive stress is not considered in the design, so that both ends of the lower flange concrete of the rigid composite beam may have excessive stresses exceeding the allowable stress.

In order to solve this problem, a part of the tension member 30 is separated from both ends of the lower flange concrete so as to be drawn out on the upper surface of the lower flange concrete so that excessive compressive stress is distributed on both ends of the composite beam. Sometimes,

Arrange the tension member in a straight shape on the lower flange concrete, but as shown in Figure 1c, the tension member is placed only in the center of the rigid composite beam where the tensile stress due to the action load is large, that is, two of the four strands of tension material (30) 31 is end fixed, and two 32 have been introduced to fix the inner anchor 50,

This method is basically not only complicated for prestressing work by tension material,

As the arrangement of the tension material is separated from each other and the tension is settled by changing the time difference, it is not easy to manage the camber of the steel,

As the anchoring position of the tension member is different, stress distortion of the compressive prestress may occur, which makes it difficult to design and construct the structure.

The stress distribution of the inelastic concrete and the steel of the elastic material is inevitably uncertain, and there is a limit to the efficient quality control of the steel composite beam.

In addition, as shown in Figure 1d in the steel composite beam using the abdomen 60 made of steel in the form of a truss to avoid forming concrete on the abdomen and the upper flange separately,

Although the abdomen of steel is used as the corrugated steel sheet, the method may reduce the self-weight of the steel composite beam.

Such a composite beam has a problem in that manufacturing is complicated and expensive.

The present invention is to solve the problems of the prior art, an object of the present invention is to provide a compression prestress required to the steel composite beam by a more efficient prestressing operation, economical by minimizing the subsidiary materials in the production of steel It can be said to provide a prestressed steel composite beam that is easy to control the quality of the composite beam by enabling the production of the composite beam, and by effectively distributing the prestress introduced by the tension material to the steel constituting the steel composite beam.

The present invention to achieve the above technical problem

In the prestressed steel composite beam produced by combining the steel 100 and concrete 300,

The buried stiffener 200 is further formed to be buried in the slab 600 to be formed later on the steel 100, wherein the buried stiffener 200 is formed in a central portion except for both ends of the steel. According to the cross section is formed,

The concrete 300 is formed so as to surround the lower portion of the steel in the center portion of the steel composite beam, and formed in the form of a cross-section that increases the forming height to cover the lower and abdomen of the steel toward both ends,

The prestress introduced to the rigid composite beam is introduced by the tension member 400 formed inside the concrete in a parabolic form while passing through the central portion from both ends of the rigid composite beam.

BRIEF DESCRIPTION OF DRAWINGS To describe the present invention more clearly and easily, the following describes the best embodiments of the present invention in detail with reference to the accompanying drawings, and embodiments according to the present invention may be modified in various other forms, and thus the scope of the present invention. Is not limited to the embodiment described below.

Figure 2a shows the steel of the U-shaped cross-section used for the steel composite beam according to Embodiment 1 of the present invention,

Figure 2b is a perspective view, A-A, B-B cross-sectional view of a steel composite beam fabricated using the U-shaped cross-section steel of Figure 2a according to the first embodiment of the present invention,

2C is a modification of the first embodiment,

FIG. 3A illustrates a steel having an I-shaped cross section used for the steel composite beam according to Example 2; FIG.

FIG. 3B shows a cross-sectional view of a steel composite beam according to examples of buried reinforcement embedded in slab in Example 2,

FIG. 3C illustrates a side view and a front view of a steel composite beam fabricated using the steel of section I cross-section of FIG. 3A according to Embodiment 1 of the present invention.

3D is a perspective view and A-A and B-B cross-sectional views of the steel composite beam according to the second embodiment of the present invention.

First, the steel composite beam of the present invention may be divided into a U-shaped steel composite beam (Example 1) and a I-shaped steel composite beam (Example 2) manufactured with a U-shaped cross section as a whole.

<Example 1>

The U-type rigid composite beam (Embodiment 1) according to the first embodiment has a technical feature that its shape is made of a U-shaped cross section, and will be described with reference to FIGS. 2A and 2B.

The U-shaped steel composite beam according to the second embodiment is largely arranged to form a steel composite beam in a U-shaped cross-section, the reinforcing steel material 200, concrete 300, tension member 400, the stress transmission guide block It consists of 500.

The steel composite beam as in Example 1 is arranged so that the two steel materials 100 are spaced apart from each other so as to be manufactured as a U-shaped cross section as shown in FIG. 2A.

At this time, each of the steel 100 is composed of the upper flange 110, the abdomen 120 and the lower flange 130 in the I-shaped cross-section, by using a steel plate processed by welding.

At this time, the buried reinforcing material 200 protrudes upward as shown in FIGS. 2A and 2B on the upper flange 110, the upper surface thereof, and is fixed and installed to be embedded in the slab 600.

The buried reinforcement 200 may be I-shaped steel, T-shaped steel, H-beams as shown in Figure 3b, the upper flange 110 of the steel 100 to be embedded in the slab 600 The bottom surface of the slab 600 can be bolted or welded L-shaped steel. In this case, the L-shaped steel of the steel serves as the upper flange, the upper flange of the steel will be seen to play the role of the buried reinforcement (200).

When used as a simple school girders, the reinforcement reinforcement 200 may be formed in a large cross-section at the central portion over the entire length of the steel 100, as shown in Figure 2a, 2b and formed into a cross-sectional shape of the cross-section smaller toward the end. In some cases, the end side can be eliminated. This is because the bending stress due to the working load is the largest in the center of the rigid beam.

In addition, when used as a continuous bridge girders, only one end portion located in the beam center portion and the branch portion can enlarge the cross section because the bending stress is the greatest at the center portion and one end portion. At this time, the one end portion is to be connected to each other and the other buried reinforcement of the beam to be connected.

In addition, the landfill stiffener 200 is disposed to be embedded in the slab 600 to have a height (molding height) of the steel material 100 and the landfill stiffener 200 combined, and in fact, steel materials are installed by installing the landfill stiffener without increasing the mold height. Will have the advantage of increasing the rigidity of,

In addition, the steel 100 is restrained by the buried reinforcement 200 embedded in the slab 600 and the concrete 300 formed inside the steel material has a greater compression buckling as the concrete height surrounding the abdomen increases toward the end Since the abdominal height of the side steel is greatly reduced to sufficiently resist the buckling, it is possible to minimize the amount of stiffeners (vertical horizontal stiffeners installed between the upper flange and the lower flange) that are usually installed on the steel abdomen of the U-shaped cross section. The advantage is that the manpower and cost of installing subsidiary materials can be greatly reduced.

In addition, a plurality of stress transmission guide block 500 according to the arrangement form of the tension member 400 is installed on the inner side abdomen 120 of the steel material 100.

The stress transmission guide block 500 is to be welded to the steel abdomen 120 to be installed, but for convenience of the body portion is to be formed in the groove is formed in the groove so that the tension member 400 is inserted into the groove to be set. 2A, the through hole may be formed in the body portion of the block form as shown in FIG. 2A to allow the tension member 400 to pass through the through hole, and the shape and shape of the through hole may be changed according to the manufacturing cost and workability.

At this time, the arrangement of the stress transfer guide block 500 is installed inclined to the steel end abdomen 120 so that the tension member 400 is disposed in a parabolic shape as a whole, so that the tension member 400 naturally depends on the arrangement of the guide stress block 500. In addition to reducing the setting effort of the tension member 400 by being installed in the form,

When the tension member 400 is settled after the tension, the tension force is distributed to the concrete 300 and the steel abdomen 120 by the stress transfer guide block 500, thereby introducing the required compression prestress (prestress force). Even if the local stress concentration of the composite beam can be effectively avoided.

Accordingly, the stress transmission guide block 500 of the present invention has a function of easily setting the arrangement of the tension member and a function of effectively dispersing the prestressing force at both ends of the steel composite beam so as to be effectively transmitted to the steel abdomen. do.

In addition, in order to more effectively secure the function of the stress transmission guide block 500, it is preferable to have an effective dispersion resistance ability of the compression prestress by installing at right angles to the abdominal surface of the steel, but the arrangement angle is not limited otherwise.

At this time, by further forming a stud 131 on the upper and / or bottom surface of the lower flange of the steel to enhance the adhesive force with the concrete 300 to be described later, and the prestressing force by the steel wire to the lower flange concrete by the stud To be smoothly delivered to the steel (100).

The concrete 300 is to be formed in a block of the rectangular parallelepiped shape having a predetermined height in the central portion of the inner steel 100, it is formed in the form of a cross-section that increases the forming height toward both ends of the steel.

The reason for the formation of such a cross section is that when the fixing plate is installed at the end formed in the same cross section with the central portion in order to fix the tension member 400 for introducing the required compression prestress, the cross section of the fixing portion is insufficient due to the end stress concentration. Many

In order to solve this problem, the concrete (300) corresponding to the fixing portion of the tension material to increase the cross-sectional area to facilitate tension tension, fixing work more easily, but to have a minimum cross-sectional area in the center of the steel unnecessary steel To prevent the self-weight of the composite beam from increasing

Accordingly, since all the tension members 400 may be disposed in a parabolic shape as a whole by forming the cross-section of the concrete, more effective compression prestress may be introduced by eccentricity.

Since the tension material is not tensioned or settled by changing the position separately, the introduction of the compression prestress is introduced uniformly throughout the steel composite beam, thereby allowing the introduction of the prestressing force that is more precise and easier to control the quality.

In detail, as a manufacturing method, the two steels 100 are spaced apart by a predetermined distance, but are inclined inward, and the concrete 300 is poured into the lower inside of the two steels 100 to produce a U-shaped steel composite beam. do.

At this time, since the two steels 100 are spaced apart from each other, when the concrete 300 is poured, the concrete is spaced between the two steels 100 using a bottom plate formwork not shown between the lower flanges of the steels 100. Do not spill.

Thus, the steel composite beam according to the first embodiment has the advantage that the both steel material 100 serves as a form of formwork, and also has the advantage that can significantly reduce the manufacturing cost as a bridge girders of U-shaped cross-section It is possible to significantly reduce the cost of manufacturing a composite beam because it does not have to use the system formwork.

In addition, due to the concrete 300, in the case of a conventional steel box girders, a reinforcement which is a subsidiary material such as many diaphragms is installed on the inner side, and the role of the subsidiary material is to prevent twisting or buckling in the box-shaped structure. This function is replaced by the concrete in the form of the cross section (remarkably reducing the subsidiary materials (vertical and horizontal reinforcement)) to enable more economical and efficient cross-sectional design.

In addition, the concrete composited with the abdomen of the steel beam at the end of the steel composite beam is formed in the beam so that it is aesthetically pleasing and an external steel wire arrangement can be added to the inside in some cases, which greatly reduces the girder weight and can be used for maintenance. Very advantageous in processing. In addition, the opening type girder bridge is proposed as a more economical rationalized bridge type (20% reduction in construction cost, etc.) than steel box, but this bridge type replaces the bottom flange of steel composite beam with concrete to replace the lower flange and subsidiary materials of steel ( It can significantly reduce the required steel materials such as reinforcement materials, and it has economical efficiency with 60% of construction cost of steel box, and it is advantageous for long time as an alternative type of steel box.

In FIG. 2C, a variation of Embodiment 1 is shown, and the upper portion is a cross-sectional view at the end side of the steel composite beam, and the lower portion is a central cross-sectional view of the steel composite beam. The steel composite beam is not to form the concrete 300 in the lower portion of the inner bottom of the lower flange 130 of the steel material, the lower flange of the U-shaped steel composite beam to form the concrete portion 310, the concrete It can be seen that the lower flange 130 of the steel material is buried in the upper portion 310, or can be installed in contact with the upper surface.

<Example 2>

The I-type steel composite beam according to the second embodiment is composed of steel 100, I-shaped reinforcement 200, concrete 300, tension member 400, stress transmission guide block 500 of the I-shaped cross-section, implementation The difference from Example 1 can be said to be the cross-sectional shape of steel. That is, the rigid composite beam according to the second embodiment is the same as the first embodiment except that the whole is manufactured in the form of I-shaped cross section.

The steel 100 is an I-shaped cross-section as shown in Figure 3a also consists of the upper flange 110, the abdomen 120 and the lower flange 130, using a steel sheet is manufactured by welding and also of steel You will be able to add more studs to your abdomen.

At this time, the buried reinforcing material 200 is fixed to the upper flange, is installed so as to protrude upward.

In this buried reinforcement 200, the I-shaped cross-section steel 210, T-shaped steel 220, H-beam steel 230 may be used from the left side of Figure 3b, the upper flange of the steel 100 The 110 is buried in the slab 600, but the L-shaped steel 240 may be bolted or welded to the bottom of the slab 600.

In addition, the stress transmission guide block 500 is also inclined in the abdomen of the I-type steel as in Embodiment 1 so that the tension member 400 is disposed in a parabolic form.

3C and 3D, the concrete 300 is formed in the form of a cross-section so that the formation height increases toward both ends of the steel composite beam to form a lower portion of the steel composite beam, the abdomen of the steel 100 And the upper flange to be exposed to the outside.

The tension member 400 is disposed in a parabolic form on the concrete 300 and is tensioned at the end of the concrete 300, and then fixed. The tension member 400 is installed in the center of the steel composite beam and disposed below the lower flange of the steel. .

In the composite steel beam according to the present invention, in forming concrete in steel, both ends of the steel composite beam are formed so that the height of the composite beam is increased to be combined with the steel abdomen, and relatively small at the center portion of the steel composite beam. Self-increasing factors were excluded.

Both ends are composited with abdominal steel and the formation height is increased, so that the neutral axis is lowered at both ends of the steel composite beam. The fixed load can be reduced by minimizing the abdominal composite concrete by adjusting the position of the secondary moment and the neutral axis according to the flexural stress generated.

Excellent workability in tensioning and fixing work of tension material, making it possible to produce steel composite beam more efficiently,

By embedding the reinforcement material installed in the steel into the slab, it effectively secures the rigidity of the steel without increasing the mold height and facilitates the composite action of the bottom plate and the steel,

The tension material can be effectively placed in a parabolic form, allowing more effective compression prestressing,

In particular, when manufacturing the composite beam in the U-shaped cross-section, the use of subsidiary materials is greatly reduced compared to the conventional box girders, and the form installation cost can be lowered, so that it is possible to manufacture a steel composite beam in the form of an economical and efficient box.

An embodiment of the present invention described above and illustrated in the drawings should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can change and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications fall within the protection scope of the present invention as long as it will be apparent to those skilled in the art.

Claims (7)

In the prestressed steel composite beam manufactured by combining steel and concrete, The buried reinforcement is further formed to be buried in the slab to be formed later on the upper portion of the steel, the buried reinforcement is to be formed in the cross-section according to the generated stress, such as formed in the central portion except the both ends of the steel, The concrete is formed to surround the lower portion of the steel in the center portion of the steel composite beam, so as to form a cross-sectional shape that is formed to increase the height formed to surround the lower and abdomen of the steel toward both ends, The prestress directed to the rigid composite beam is introduced by a tension member formed inside the concrete in a parabolic form while passing through the central portion from both ends of the rigid composite beam. At both ends of the steel, a stress transmission guide block is further installed to resist the stress concentrated at the end of the steel composite beam and to facilitate the inclination of the tension material, but the tension material is supported by the stress transmission guide block to form a parabola in the concrete. Prestressed rigid composite beam, characterized in that arranged. The prestressed steel composite beam of claim 1, wherein the steel constituting the steel composite beam is formed of a steel having an I-shaped cross section so that the concrete is wrapped around and exposed to the steel having an I-shaped cross section. According to claim 1, The steel constituting the composite beam is disposed so that the steel of the I-shaped cross-section is spaced from each other, the concrete composite beam is formed so that the concrete is formed inside the both steel to be manufactured in a U-shaped cross-sectional shape. Prestressed steel composite beam, characterized in that. delete The method of claim 3, wherein the concrete of the pre-stressed steel composite beam manufactured by manufacturing the U-shaped cross-sectional shape is to be formed of a concrete portion of the flange form formed in addition to the inner side of the steel abdomen, the lower flange of the steel inside the concrete portion Prestressed steel composite beam, characterized in that to be embedded in. The prestressed composite beam according to any one of claims 1 to 3, wherein the stress transfer guide block is formed of a steel block having a through hole or a block having an open groove. The prestressed rigid composite beam according to claim 6, wherein the tension member disposed in the parabolic form is tensioned after the steel and the concrete are synthesized to be fixed at the end of the rigid composite beam.

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