KR20190127016A - Construction method of multi preflex composite girder - Google Patents

Abstract

Disclosed is a construction method of a multi-preflex composite girder which uses a restoring force of a steel beam to introduce prestress to casing concrete. The construction method of a multi-preflex composite girder comprises: a steel beam mounting step of mounting a front and a rear end of a steel beam whose longitudinal middle portion is cambered upwards on a support; a temporary reinforcing plate installation step of fixing a temporary reinforcing plate in a longitudinal direction of an upper plate of the steel beam to bring the temporary reinforcing plate into surface contact with the upper plate; a preflexion load applying step of applying a preflexion load to the temporary reinforcing plate and the steel beam; a casing concrete deposition step of installing casing concrete on a lower plate of the steel beam; a preflexion load removal step of removing the preflexion load applied to the temporary reinforcing plate and the steel beam; and a temporary reinforcing plate separation step of separating the temporary reinforcing plate from the steel beam. According to the present invention, since additional compressive stress is introduced to the casing concrete by the temporary reinforcing plate, the amount of steel used in an upper plate of an I-shaped steel beam can be reduced. Therefore, construction costs can be reduced.

Description

Construction method of composite preflex composite girder {CONSTRUCTION METHOD OF MULTI PREFLEX COMPOSITE GIRDER}

The present invention relates to a method for constructing a composite preflex composite girder that introduces prestress into casing concrete using the restoring force of the steel beam. More particularly, the present invention relates to a precise prefabricated composite girder using a steel beam. It is possible to introduce reflection and to construct a composite preflex composite girder that uses temporary reinforcement plates to reduce the amount of steel and introduce additional compressive stress to the casing concrete.

The preflex composite girder is made by placing and curing casing concrete around the lower plate of the steel beam in a state where a predetermined preflection load is applied to the steel beam for the preflex composite girder (usually I-shaped steel), and then the applied preflection load is applied. By using the restoring force of the steel beam generated by removal, it means a girder configured to introduce a kind of prestress to the casing concrete.

In general, I-beams made in factories are bent upward by the required rise. The steel beams are made by loading a constant preflection load (Pf) by the hydraulic jack from the beam end to two points on both sides of L / 4, removing the preflex load (Pf) introduced by the hydraulic jack after placing and hardening the casing concrete. Compressive stress is introduced into the casing concrete by the restoring force of the preflex steel composite girders.

1 is a flowchart schematically showing a method of constructing a general preflex composite girder.

More specifically, the construction method of the preflex composite girder first performs the process of mounting the I-beam steel beam 1, which is raised upward as shown in Figure 1 (a) to the support (3). At this time, the configuration shown in 1H is the upper plate, the configuration shown in 1L is the lower plate.

Next, the steel beam 1 mounted on the support 3 is loaded with the pre-flection load Pf in the main load direction so that the steel beam 1 is deformed as shown in FIG.

Subsequently, as shown in FIG. 1B, the casing concrete 2 is placed on the lower plate 1L side of the steel beam 1 in the state where the preflection load Pf is loaded, as shown in FIG. 1C. Perform the process of pouring and curing.

Finally, when the casting and curing of the casing concrete (2) is completed, the process of introducing the pre-stress to the casing concrete (2) by removing the loaded preflection load (Pf) as shown in Figure 1 (d) Perform.

However, the conventional simple synthetic type preflection construction method and the multi-span fabrication method connecting the same have the following problems.

In other words, temporary facilities such as the installation of hydraulic jacking facilities and steel reaction zone earth anchor facilities for the introduction of preflection loads occupy a large proportion of the manufacturing cost of preflex composite type, and many basic concrete is disposed of after completion of construction. As a result, waste disposal costs were additionally generated, which contributed to an increase in the overall construction cost.

Moreover, casing concrete supported on the ground during the release process in which the compressive stress is introduced into the casing concrete through the release operation in which the casing concrete is poured and hardened after the pre-exposure process removes the load of the hydraulic jack and causes the return force of the type I steel beam. The steel composite girder including the restoring upwards, wherein the return force of the type I steel beam is reduced by an amount corresponding to the weight of the casing concrete having a heavy weight, and the compressive stress introduced into the casing concrete is immediately lost. This happens.

Accordingly, in order to introduce the pre-designed compressive stress during the manufacturing process, a greater return force is required, that is, a larger pre-flection load by the hydraulic jack, and ultimately, more steel is required. Caused it.

In addition, in terms of structure, the use of a large amount of temporary steel is necessary for the construction of the casing concrete, but only for the purpose of supporting, it can be said that the contribution to the introduction of the compressive stress to the casing concrete or to reduce the manufacturing cost.

In case of using PS steel wire for structural continuity of composite type, in order to draw PS steel wire from the bottom of composite bottom plate to the top of upper plate near the piers, perforated hole must be formed in upper plate and lower plate respectively. Therefore, it is necessary to penetrate through holes having upper holes and lower plates, which leads to cumbersome processes.When concrete steel is placed in contact with steel, the PS steel wire breaks during tension or bridge work. Since serious problems may arise in safety, very thorough construction management is required.

Moreover, the greatest concentrated load in the steel beam is the preflection stage, whereby the perforated hole is mechanically located near the preflex concentration load point on the PS steel wire arrangement. May cause defects such as buckling and cracks in the

Republic of Korea Patent No. 10-1339367 (2014.01.03 announcement) Republic of Korea Patent No. 10-1319993 (announced on October 29, 2013) Republic of Korea Patent No. 10-1339362 (announced on March 11, 2016) Republic of Korea Patent Registration No. 10-1664165 (2016.10.11 announcement

Accordingly, an object of the present invention is to improve the construction and weight of the installation of the temporary structural structure indispensable to the efficient construction method in consideration of the construction ability to lead to a mechanically useful process, thereby reducing the construction cost by the optimized reduction of the main material type I steel beam The present invention provides a method for constructing a composite preflex rigid girder.

At this time, the maximum stress generation of the steel beam is a process of loading and removing the pre-flection load in order to introduce the compressive stress to the casing concrete, and since the bottom plate and other concrete stiffness much larger than the steel beam in the future, the object of the present invention is The present invention provides a method for constructing a composite preflex composite girder that can improve the stress state until the bottom plate synthesis.

In order to achieve the above object of the present invention, in one embodiment of the present invention, the temporary reinforcing plate along the longitudinal direction of the upper plate so as to be in contact with the upper plate of the steel beam with the central portion raised upward relative to the longitudinal direction Temporary reinforcing plate installation step of fixing, and the steel beam mounting step of mounting the front and rear ends of the steel beam to the support, Pre-load load loading step of applying a pre-flection load to the temporary reinforcing plate and steel beam, and the steel beam Casing concrete pouring step of installing the casing concrete on the lower plate of the pre-flection load removing step of removing the pre-flection load loaded on the temporary reinforcement plate and the steel beam, and temporary to separate the temporary reinforcement plate from the steel beam Provided is a method for constructing a composite preflex composite girder comprising a reinforcing plate separating step.

In addition, in another embodiment of the present invention, the steel beam mounting step of mounting the front and rear ends of the steel beam with the central portion soared upward based on the longitudinal direction, and the temporary reinforcing plate to be in contact with the upper plate of the steel beam Temporary reinforcement plate installation step of fixing the length along the longitudinal direction of the upper plate, Preflection load loading step of applying a preflection load to the temporary reinforcement plate and the steel beam, and to install the casing concrete on the lower plate of the steel beam A composite free comprising a casing concrete placing step, a pre-flection load removing step of removing the pre-flexion load loaded on the temporary reinforcing plate and the steel beam, and a temporary reinforcing plate separating step of separating the temporary reinforcing plate from the steel beam. Provides a method for constructing a flex rigid girder.

The present invention can increase the efficiency of stress introduction and the economics of material savings by using the temporary reinforcing plate in the introduction of compressive stress to the lower casing concrete by loading the preflex load.

More specifically, the highest risk point in the production of general preflex composite girders is the point where the preflex load is applied to introduce the compressive stress to the casing concrete, and the stress is subtracted by a subsequent process such as release. Is reduced, or the stiffness is increased by casing and bottom plate pours, resulting in a stressed stabilization state rather than a preflex load overall. Therefore, the governing condition for determining the amount of steel of the girder is absolutely influenced by the magnitude of the preflection load introduced, and the temporary stiffening plate not only reduces the absolute value of the preflection load by increasing the compression efficiency but also after the instantaneous peak occurs. It provides the effect of increasing the economics by eliminating the unnecessary rigidity.

In the present invention, in loading the preflex load, the temporary reinforcing plate is installed on the upper part of the steel beam, and then the preplex load is loaded, and the casing concrete is removed after placing and curing the casing concrete on the lower part of the steel beam. Compressive stress can be introduced into the In the present invention, when the temporary reinforcing plate is temporarily installed from the steel beam, the additional compressive stress due to the stiffness difference can be introduced into the casing concrete.

More specifically, in the present invention, when the temporary reinforcing plate is separated from the steel beam after removing the preflection load, the same rising force is introduced in the smaller cross section, so that the compressive stress is reduced in the upper plate of the steel beam, which is the compression region, and the tensile region. Tensile stress is reduced in the lower plate of the steel beam, and compressive force is additionally introduced into the casing concrete.

As a result, the present invention uses a temporary reinforcement plate that can be recycled during the process of removing the preflex load after loading the preflex load on the steel beam, and as supplemented by the temporary reinforcement plate on the upper plate of the steel beam. Since the amount of steel used can be reduced, construction costs can be reduced and additional compressive stress can be introduced into the lower casing concrete.

1 is a flowchart schematically showing a construction method of a conventional preflex rigid composite girders.
Figure 2 is a flow chart for explaining the construction method of pre-flex composite girder according to an embodiment of the present invention.
Figure 3 is a flow chart for explaining the construction method of pre-flex composite girder according to another embodiment of the present invention.
Figure 4 is a schematic diagram schematically showing the construction method of the preflex composite girder of the present invention.
5 is a perspective view showing a preflex loading device according to an embodiment of the present invention.

Hereinafter, a method of constructing a composite preflex composite girder according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings (hereinafter, abbreviated as a method of constructing a composite girder).

Figure 2 is a flow chart for explaining the construction method of the preflex composite girder according to an embodiment of the present invention, Figure 3 is a flow chart for explaining the construction method of the preflex composite girder according to another embodiment of the present invention. 4 is a schematic diagram schematically showing a method for constructing a preflex rigid girder of the present invention.

2 and 4, the construction method of the composite girder according to the present invention is installed a temporary reinforcing plate to fix the temporary reinforcing plate 30 to the steel beam 10 to be in contact with the upper portion of the steel beam (10) Step (S100), the steel beam mounting step (S200) for mounting the front and rear ends of the steel beam 10 to the support 20, and the pre-flection load on the temporary reinforcing plate 30 and the steel beam (10) Pre-load load loading step (S300) for applying a, casing concrete placing step (S400) for installing the casing concrete 40 in the lower portion of the steel beam 10, the temporary reinforcing plate 30 and the steel beam (10) The preflection load removing step (S500) for removing the preflection load loaded on the), and the temporary reinforcing plate separating step (S600) for separating the temporary reinforcing plate 30 from the steel beam (10).

As a specific aspect, the steel beam 10 according to the present invention preferably uses an I-shaped steel beam composed of an upper plate 12, a lower plate 14 and an abdomen (web, 16) connecting these plates. At this time, the upper plate 12 is provided on the upper part of the abdomen 16 arranged in the vertical direction, the lower plate 14 is provided on the lower part of the abdomen 16 arranged in the vertical direction, the upper plate 12 and The lower plate 14 is disposed to face each other.

If necessary, the present invention first proceeds to the steel beam mounting step (S100) for mounting the front end and the rear end of the steel beam 10 to the support 20, then the steel beam 10 of the It may be configured to proceed to the temporary reinforcing plate installation step (S200) for fixing the temporary reinforcing plate 30 to the steel beam 10 so as to be folded in the upper portion.

Hereinafter, each component will be described in more detail with reference to the accompanying drawings. In this case, the steel beam 10 will be described as using an I-shaped steel beam.

First, the construction method of the composite girder according to the present invention includes a steel beam mounting step (S100).

The steel beam mounting step (S100) is a step of mounting the front and rear ends of the steel beam 10, the center portion is raised upwards relative to the longitudinal direction to the support 20, the steel beam 10 using a crane or the like. After lifting from the ground to place the support 20 in the lower end of the front and rear ends of the steel beam 10 and then seat the steel beam 10 on the support 20.

The support 20 is installed on the bottom surface of the steel beam 10, the first support 22 for separating the steel beam 10 from the ground, and the steel beam 10 is installed on the bottom surface of the rear beam 10 ) May be configured as a second support 24 spaced apart from the ground.

If necessary, in the step S100, the plurality of steel beams 10 may be arranged in the same line and assembled to generate a steel beam assembly, and then the center of the steel beam assembly may be manufactured to be curved in a convex shape. In this case, the contact surface of the steel beam 10 and the steel beam 10 may be directly welded and connected, or may be connected to the steel beam 10 and the steel beam 10 in a bolting and riveting method. In other words, the plurality of steel beams 10 may be connected to each other through physical coupling means such as bolts, or may be connected through chemical bonding methods such as welding.

Subsequently, the construction method of the steel composite girder according to the present invention includes a temporary reinforcing plate installation step (S200).

The temporary reinforcing plate installation step (S200) is the upper plate 12 so that the temporary reinforcing plate 30 is in contact with the upper plate 12 of the steel beam seated on the support 20 through the steel beam mounting step (S100). In the step of fixing the temporary reinforcing plate 30 in the longitudinal direction of, the temporary reinforcing plate 30 is preferably fixed by physical coupling means such as bolts so that the separation from the upper plate 12 later proceeds smoothly.

The temporary reinforcing plate 30 is a first point of 1/5 to 1/3 of the steel beam 10 used in the steel composite girder of the present invention, and 2/3 to 4/5 of the steel beam 10 It is preferably configured to have a length covering the second point. This is because the preplex composite girder is composed of two parts, a relatively thick center part and a relatively thin both end part, and the section is about 1/5 to 1/3 from both ends. Therefore, the present invention can reduce the amount of steel in the thick section of the middle portion by providing a temporary reinforcing plate in the intermediate position where the cross-sectional force is generated and a large rigidity is required.

Then, the construction method of the composite girder according to the present invention includes a pre-flection load loading step (S300).

The pre-flection load loading step (S300) is a step of loading the pre-flection load on the temporary reinforcing plate 30 installed in the steel beam 10 through the temporary reinforcing plate installation step (S200), around the steel beam (10) The preflex load is loaded on the temporary reinforcing plate 30 and the steel beam 10 through the installed preflex loading device. In this case, it is preferable to load the preflection load at the first point of 1/5 to 1/3 and the second point of 2/3 to 4/5 of the entire length of the steel beam 10.

"형 구조를 갖도록 형성될 수 있다.5 is a perspective view showing a preflex loading device according to an embodiment of the present invention. Referring to FIG. 5, the preflex loading device includes a plurality of two-row posts 100 and steel beams 10 installed at regular intervals from the steel beams 10 so as to face each other with respect to the steel beams 10. It is installed at regular intervals along the longitudinal direction of the () and includes two stands (210, 220) formed to cover the circumference of the left, right, and the upper surface of the steel beam (10). For example, the stand "

It may be formed to have a "type structure.

As a specific aspect, the pre-load load loading step (S300) according to the present invention may be composed of a stand installation process (S310), jack installation process (S320), and jack driving process (S330).

"형 제1 스탠드(210)를 설치하고, 상기 강재빔(10)의 전체 길이 중 2/3 내지 4/5의 제2 지점에 "

"형 제2 스탠드(220)를 설치한다. In the stand installation process (S310) "1/5 to 1/3 of the entire length of the steel beam 10,"

&Quot; Install the first stand 210, and at the second point of 2/3 to 4/5 of the entire length of the steel beam 10 "

The second stand 220 is installed.

In the jack installation process (S320), as shown in FIG. 5, a first jack 310 is installed between the first stand and the temporary reinforcing plate 30, and between the second stand and the temporary reinforcing plate 30. Install the second jack 320 in the. Here, as the first jack 310 and the second jack 320, a hydraulic jack, a screw jack and the like can be used.

In the jack driving process (S330), a pre-flection load is applied to the temporary reinforcing plate 30 in the ground direction through the first jack 310 and the second jack 320.

If necessary, the construction method of the composite girder according to the present invention may further include a transverse support steel installation step (S250) between the temporary reinforcing plate installation step (S200) and the pre-flection load loading step (S300).

The horizontal support steel installation step (S250) is provided in the vertical direction on the left side of the steel beam 10 to install a first horizontal support steel 410 in contact with the steel beam 10, the steel beam 10 Is provided in the vertical direction on the right side of the step of installing the second horizontal support steel 420 in contact with the steel beam (10).

The first lateral support die 410 is connected to the post positioned on the left side of the two-row posts as shown in FIG. 5, and the second lateral support die 420 is connected to the post located on the right side of the two-row posts. .

 As such, when the horizontal support steels 410 and 420 are installed on the left and right sides of the steel beam 10, the steel beam 10 is prevented from lateral movement in the pre-loading load loading step S300, so that the steel beam 10 has a purpose. It is possible to load the pre-fraction load, and the buckling of the steel beam 10 is prevented.

Thereafter, the construction method of the composite girder according to the present invention includes a casing concrete pouring step (S400).

The casing concrete pouring step (S400) is a step of installing the casing concrete 40 on the lower plate 14 of the steel beam 10, it may be composed of the formwork installation process and the casing concrete 40 curing process.

The formwork installation process is a process of installing the formwork on the lower plate 14 of the steel beam 10, the casing concrete curing process is a process of removing the formwork after placing and curing concrete in the formwork.

Subsequently, the construction method of the rigid girder according to the present invention includes a preflection load removing step (S500).

The preflection load removing step (S500) is a step of removing the preflection loads loaded on the temporary reinforcing plate 30 and the steel beam 10, the preflection load loaded in the temporary reinforcement plate 30 in the ground direction By removing the temporary reinforcing plate 30 and the steel beam 10 is rotated to the initial position.

Specifically, in the step (S500) after removing the pre-flection load applied to the temporary reinforcing plate 30 and the steel beam 10 through the first jack 310 and the second jack 320, the first jack ( 310 and the second jack 320 is separated between the stand (210, 220) and the temporary reinforcing plate (30).

In this step (S500), the compressive stress is introduced to the casing concrete 40 installed on the lower plate 14 of the steel beam 10 by removing the preflection load introduced to the steel beam 10.

Finally, the construction method of the composite girder according to the present invention includes a temporary reinforcing plate separating step (S600).

The temporary reinforcing plate separating step (S600) is a step of separating the temporary reinforcing plate 30 fixed to the steel beam 10 through the temporary reinforcing plate installation step (S200) from the steel beam (10).

By removing the temporary reinforcing plate 30, the upward force of the steel beam 10 is generated, and additional compressive stress is introduced into the casing concrete 40.

If necessary, the construction method of the composite girder according to the present invention may further include a transverse support-type separation step (S700) between the preflection load removing step (S500) and the temporary reinforcing plate separating step (S600).

The horizontal support steel separating step (S700) is a step of separating the first horizontal supporting steel 410 and the second horizontal supporting steel 420 installed in the above-described horizontal supporting steel installation step (S250) from the steel beam (10). The second horizontal supporting steel 410 and the second horizontal supporting steel 420 are separated from the second row post 100, and then the first horizontal supporting steel 410 and the second horizontal supporting steel 420 are removed. .

Hereinafter, it will be described in more detail through specific embodiments of the present invention. However, this embodiment is to help the understanding of the specific examples of the above-described invention, and thus the scope of rights and the like should not be construed as limited.

Example 1

1. Composition of the rigid beam

Span length: 40 m, Height: 1.5 m, Reinforcement plate: 20 x 900 mm ²

Top plate: 30 x 900 mm ² , Abdomen plate: 1178 x 12 mm ²

Bottom plate: 46 x 900 mm ² , Rigid gross height: 1274 mm

Cross section characteristic calculation:

A: cross-sectional area, Y: distance from the center of the part to the lower surface

Io: Cross section second moment of the part

Thus, after calculating the cross-sectional rigidity for each part, the cross-sectional rigidity of one whole cross section was computed as follows.

Y = 0.658 m, Yt1 = 0.616 m, Yt = 0.616 m, Yb1 = 0.658 m

Yb = 0.658 m, Ic = 0.03407 m⁴

Y, Yb: Distance from the center of the entire section to the bottom of the entire section

Yt: Distance from the center of the whole section to the top of the whole section

Yt1: Distance from the center of the entire section to the top of the rigid

Yb1: Distance from the center of the entire section to the bottom of the rigid

Yb2: Distance from the center of the whole section to the bottom of the casing

Ic: Cross section secondary moment of whole section

Cross Section A: 0.101m ²

Self-weight of the rigid beam w: 7.892 kN / m

Section secondary moment: 0.03407 m ⁴

Ganghyeong moment due to self weight ^{M: M = w × L 2} /8 = 1578 kN.m

Stress due to heavy weight

fst1 = M × Yt1 / I = −28.547 MPa. fsb1 = M × Yb1 / I = 30.475 MPa

The first letter f is the stress, Y is the stress calculation position, I is the section stiffness represented by the section second moment, and M is the bending moment of the section.

2. Preflection Load

Preflection load P: 1000 kN

M = P × L / 4 = 10000 kN.m, fst1 = M × Yt1 / I = -180.860 MPa

fsb1 = M × Yb1 / I = 193.076 MPa, fst1_sum = -209.407 MPa> -319.500 MPa

fsb1_sum = 223.551 MPa <284.000 MPa

3. casing concrete

Casing concrete size: 400 x 1000 mm ²

Total height with casing: 1374 mm

Y = 0.589 m, Yt 1 = 0.785 m, Yt = 0.785 m, Yb 1 = 0.489 m

Yb = 0.589 m, Yb2 = 0.589 m, Ic = 0.04409 m⁴

Self weight of casing w: 10.000 kN / m

Moment due to self-weight casing ^{M: w × L 2/8} = 2000 kN.m

Stress due to casing weight

fst1 = M × Yt1 / I = -35.588 MPa, fsb1 = M × Yb1 / I = 22.201 MPa

fsb2 = M × Yb2 / I = 2.905 MPa, fst1_sum = -244.995 MPa> -248.500 MPa

fsb1_sum = 245.753 MPa <248.500 MPa

fsb2_sum = 2.905 MPa <3.220 MPa

4. Remove Preflection Load

Reinforcement plate removal w: -1.413 kN / m

Moment due to remove the reinforcing plate ^{M: M = w × L 2} /8 = -283 kN.m

Preflection load P: -1000 kN

M = P × L / 4 = -10000 kN.m

Moment M by Reinforcement Plate Removal and Preflection Load Removal M:

M = -10283 kN.m

fst1 = M × Yt1 / I = 182.967 MPa, fsb1 = M × Yb1 / I = -114.144 MPa

fsb2 = M × Yb2 / I = -14.937 MPa, fst1_sum = -62.028 MPa> -248.500 MPa

fsb1_sum = 131.609 MPa <248.500 MPa

fsb2_sum = -12.032 MPa> -24.300 MPa

Preflection load: 100 ton

Steel amount after removal of preflection load: 25.916 ton

Example 2

Span length: 40 m, Height: 1.5 m, Reinforcement plate: 20 x 900 mm ²

Top plate: 40 x 900 mm ² , Abdomen plate: 1178 x 12 mm ²

Lower plate: 56 x 900 mm ^2, rigid gross height: 1294 mm

Cross section characteristic calculation:

Y = 0.665 m, Yt1 = 0.629 m, Yt = 0.629 m, Yb1 = 0.665 m

Yb = 0.665 m, Ic = 0.04150 m⁴

Cross section A: 0.119m ²

Self-weight of rigid beam w: 9.305 kN / m

Section secondary moment: 0.04150 m ⁴

Ganghyeong moment due to self weight ^{M: w × L 2/8} = 1861 kN.m

Stress due to heavy weight

fst1 = M × Yt1 / I = -28.225 MPa, fsb1 = M × Yb1 / I = 29.808 MPa

2. Preflection Load

Preflectional load P: 1200 kN

M = P × L / 4 = 12000 kN.m, fst1 = M × Yt1 / I = -182.000 MPa

fsb1 = M × Yb1 / I = 192.208 MPa, fst1_sum = -210.225 MPa> -319.500 MPa

fsb1_sum = 222.016 MPa <284.000 MPa

3. casing concrete

Casing concrete size: 400 x 1000 mm ²

Total height with casing: 1394 mm

Y = 0.613 m, Yt 1 = 0.781 m, Yt = 0.781 m, Yb 1 = 0.513 m

Yb = 0.613 m, Yb2 = 0.613 m, Ic = 0.05221 m⁴

Self weight of casing w: 10.000 kN / m

Moment due to self-weight casing ^{M: w × L 2/8} = 2000 kN.m

Stress due to casing weight

fst1 = M × Yt1 / I = -29.909 MPa, fsb1 = M × Yb1 / I = 19.656 MPa

fsb2 = M × Yb2 / I = 2.552 MPa, fst1_sum = -240.134 MPa> -248.500 MPa

fsb1_sum = 241.672 MPa <248.500 MPa

fsb2_sum = 2.552 MPa <3.220 MPa

4. Remove Preflection Load

Reinforcement plate removal w: -1.413 kN / m

Moment due to remove the reinforcing plate ^{M: M = w × L 2} /8 = -283 kN.m

Preflection Load P: -1200 kN

M = P × L / 4 = -12000 kN.m

Moment M by Reinforcement Plate Removal and Preflection Load Removal M:

M = -12283 kN.m

fst1 = M × Yt1 / I = 218.554 MPa, fsb1 = M × Yb1 / I = -136.345 MPa

fsb2 = M × Yb2 / I = -17.842 MPa, fst1_sum = -21.579 MPa> -248.500 MPa

fsb1_sum = 105.327 MPa <248.500 MPa

fsb2_sum = -15.290 MPa> -24.300 MPa

Preflection Load: 120 ton

Steel amount after removal of pre-flex load: 31.568 ton

[Comparative Example]

1. Composition of the rigid beam

Span length: 40 m, Height: 1.5 m, Reinforcement plate: 0 x 0 mm ²

Top plate: 50 x 900 mm ² , Abdomen plate: 1178 x 12 mm ²

Lower plate: 46 x 900 mm ^2, rigid gross height: 1274 mm

Cross section characteristic calculation:

Y = 0.658 m, Yt1 = 0.616 m, Yt = 0.616 m, Yb1 = 0.658 m

Yb = 0.658 m, Ic = 0.03407 m⁴

Cross Section A: 0.101m ²

Self-weight of the rigid beam w: 7.892 kN / m

Section secondary moment: 0.03407 m ⁴

Ganghyeong moment due to self weight ^{M: M = w × L 2} /8 = 1578 kN.m

Stress due to heavy weight

fst1 = M × Yt1 / I = -28.547 MPa, fsb1 = M × Yb1 / I = 30.475 MPa

2. Preflection Load

Preflection load P: 1000 kN

M = P × L / 4 = 10000 kN.m, fst1 = M × Yt1 / I = -180.860 MPa

fsb1 = M × Yb1 / I = 193.076 MPa, fst1_sum = -209.407 MPa> -319.500 MPa

fsb1_sum = 223.551 MPa <284.000 MPa

3. casing concrete

Casing concrete size: 400 x 1000 mm ²

Total height with casing: 1374 mm

Y = 0.589 m, Yt 1 = 0.785 m, Yt = 0.785 m, Yb 1 = 0.489 m

Yb = 0.589 m, Yb2 = 0.589 m, Ic = 0.04409 m⁴

Self weight of casing w: 10.000 kN / m

Moment due to self-weight casing ^{M: w × L 2/8} = 2000 kN.m

Stress due to casing weight

fst1 = M × Yt1 / I = -35.588 MPa, fsb1 = M × Yb1 / I = 22.201 MPa

fsb2 = M × Yb2 / I = 2.905 MPa, fst1_sum = -244.995 MPa> -248.500 MPa

fsb1_sum = 245.753 MPa <248.500 MPa

fsb2_sum = 2.905 MPa <3.220 MPa

4. Remove Preflection Load

Preflection load P: -1000 kN

M = P × L / 4 = -10000 kN.m

fst1 = M × Yt1 / I = 177.938 MPa, fsb1 = M × Yb1 / I = -111.006 MPa

fsb2 = M × Yb2 / I = -14.526 MPa, fst1_sum = -67.057 MPa> -248.500 MPa

fsb1_sum = 134.746 MPa <248.500 MPa

fsb2_sum = -11.621 MPa> -24.300 MPa

Preflection load: 100 ton

Steel amount after removal of pre-flex load: 31.568 ton

Looking at [Example 1] and [Comparative Example], when the temporary stiffening plate and the preflection load are removed together, the same lifting force is introduced in the smaller cross section, and thus the upper plate as the compression region as shown in [Table 1] below. The compressive stress is reduced by about 7.5% at, the tensile stress is reduced by about 2.3% at the lower plate, which is the tensile area, and the 3.5% additional compressive stress is introduced in the casing concrete, and recyclable temporary stiffeners are used. In this case, it was observed that the actual amount of steel input was reduced by about 17.9%.

Looking at [Example 2] and [Comparative Example], when the temporary stiffening plate and the preflection load are removed together, the same lifting force is introduced into the smaller cross section, and thus the upper plate as the compression region as shown in [Table 1] below. The compressive stress of about 67.8% is reduced at, the tensile stress of about 21.8% is decreased at the lower plate, the tensile area, about 31.6% of the compressive stress is additionally introduced in the casing concrete, and the amount of steel beam is maintained. It has been observed that maximal cross-section efficiency is possible because of the additional loading of 20% preflection load.

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated.

10: steel beam 12: upper plate
14: lower plate 16: abdomen
20: support 20, 22: first support
24: second support 30: temporary reinforcement plate
40: casing concrete 100: two-row post
210: first stand 220: second stand
310: first jack 320: second jack
410: first lateral support steel 420: second lateral support steel

Claims (7)

A temporary reinforcing plate installation step of fixing the temporary reinforcing plate along the longitudinal direction of the upper plate so as to be in contact with the upper plate of the steel beam with the central portion rising upwardly based on the longitudinal direction;
Steel beam mounting step of mounting the front and rear ends of the steel beam to the support;
A preflection load loading step of applying a preflection load to the temporary reinforcing plate and the steel beam;
Casing concrete placing step of installing the casing concrete on the lower plate of the steel beam;
A preflection load removing step of removing a preflection load loaded on the temporary reinforcing plate and the steel beam; And
Construction method of a composite preflex composite girder comprising a temporary reinforcing plate separating step of separating the temporary reinforcing plate from the steel beam.
The method of claim 1, wherein the preflection load is
Method of constructing a composite preflex composite girder, characterized in that the loading at the first point of 1/5 to 1/3 and the second point of 2/3 to 4/5 of the total length of the steel beam. According to claim 1, Between the temporary reinforcing plate installation step and the pre-load load loading step
The first horizontal support steel is provided on the left side of the steel beam in the up-and-down direction to contact the steel beam, and the horizontal side is provided on the right side of the steel beam in the vertical direction to install the second horizontal support steel in contact with the steel beam. Construction method of a composite preflex composite girder, characterized in that it further comprises a support steel installation step. According to claim 3, Between the pre-flection load removing step and the temporary reinforcing plate separating step
And a lateral support steel separation step of separating the first lateral support steel mold and the second lateral support steel mold from the steel beams. The method of claim 1, wherein the pre-load loading step
At a first point of 1/5 to 1/3 of the total length of the steel beam;

"Install a shaped first stand, and at the second point of 2/3 to 4/5 of the entire length of the steel beam"

Stand installation process for installing the second type of stand,
A jack installation process of installing a first jack between the first stand and the temporary reinforcing plate, and installing a second jack between the second stand and the temporary reinforcing plate, and
Method of constructing a composite preflex composite girder, characterized in that consisting of a jack driving process for applying a preflection load to the temporary reinforcing plate in the ground direction through the first jack and the second jack. According to claim 1,
The temporary reinforcing plate of the steel beam
A method for constructing a composite preflex composite girder, characterized in that it has a length covering a first point of 1/5 to 1/3 and a second point of 2/3 to 4/5. Steel beam mounting step of mounting the front end and the rear end of the steel beam with the central portion rises upward relative to the longitudinal direction to the support;
A temporary reinforcing plate mounting step of fixing the temporary reinforcing plate along the longitudinal direction of the upper plate so as to be in contact with the upper plate of the steel beam;
A preflection load loading step of applying a preflection load to the temporary reinforcing plate and the steel beam;
Casing concrete placing step of installing the casing concrete on the lower plate of the steel beam;
A preflection load removing step of removing a preflection load loaded on the temporary reinforcing plate and the steel beam; And
Construction method of a composite preflex steel composite girder comprising a temporary reinforcing plate separating step of separating the temporary reinforcing plate from the steel beam.

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