KR100478561B1 - continued prestressed composite beam having a slanted cross-section portion formed in steel and method for continuously constructing the composite beam - Google Patents

Abstract

       The present invention relates to a continuous prestressed composite beam having an oblique cut portion formed in a steel material and a construction method for continually synthesizing the composite beam. It is produced by dividing into the parent member, but when manufacturing the positive moment member, the upper casing gives the upward upward load and loads the preflexion load to the downward downward rise, and then pours constrained concrete at the bottom of the steel to cure the lower casing concrete. It is formed, and gradually removes the loaded preflection load to introduce a compressive force, when manufacturing the parent member, only the bottom of the concrete is poured into the steel, and the steel is connected to each other at the split point to produce a composite beam.

       At this time, an oblique cut portion in which the steel is cut diagonally is formed at the connection portion of the steel forming the positive moment member and the parent moment member so that a gap having a size of 1 to 3 cm in the form of a "V" shape is formed, and a continuous composite beam is formed. When connecting the positive and negative moment members to each other, make contact with each other so as to eliminate the gap formed by the slanted cutting part formed in the steel, and then connect them using high-strength bolts, and when placing the upper concrete, the amount of bending moment acting on the positive moment member The amount of bending moment acting on the positive moment member is reduced by partially restoring by the restoring moment generated in the steel by the connection of the oblique cut portion, so that the prestressed continuous bridge having a safe and slender structure can be manufactured.

Description

     Continuous prestressed composite beam having a slanted cross-section portion formed in steel and method for continuously constructing the composite beam}

       The present invention relates to a construction method for continuous prestressed composite beams using diagonal cutouts formed in steel at the spanning points of continuous prestressed composite beams. Manufactured by dividing it into a constant moment member and a parent moment member, but in the case of manufacturing the constant moment member, it gives upward upward rise, loads a pre-flection load on the produced steel, changes it to downward downward rise, and pours constrained concrete at the bottom of the steel. To form the lower casing concrete, and gradually remove the loaded preflection load to introduce the compressive force.When manufacturing the parent member, only the bottom concrete is cast on the steel, and the steel is connected to each other at the span splitting point. A composite beam is produced.

       At this time, an oblique cut portion in which the steel is cut diagonally is formed at the connection portion of the steel forming the positive moment member and the parent moment member so that a gap having a size of 1 to 3 cm in the form of a "V" shape is formed, and a continuous composite beam is formed. When connecting the positive and negative moment members to each other for manufacturing, remove the gap formed by the diagonal cuts formed in the steel, and then contact each other with the diagonal cuts, and then use high tension bolts to connect the concrete to the top moment Since the amount of bending moment is partially canceled by the restoring moment generated in the steel material by the connection of the diagonal cut portion, the amount of bending moment acting on the positive moment member is reduced, so that a prestressed continuous bridge having a safe and slender structure can be manufactured.

        The purpose of the present invention is to connect the prestressed composite beams to each other in the case of sequential construction of the concrete creep dry shrinkage when the upper concrete is poured after connecting the steel forming the positive and secondary moment members and fixing with bolts There is a problem in that the cross-sectional shape is excessively designed because the stress reduction due to or the like cannot be corrected.

       Therefore, in order to solve this problem, the present invention forms a diagonal cut portion at the connection portion of the steel constituting the positive and negative moment members and connects the diagonal cut portions to each other when connecting the positive and negative moment members to continuous the prestressed composite beam. When connecting with bolts and placing top concrete, the bending moment of the positive moment member is reduced by the secondary moment formed by the slanted cut in the steel, resulting in a smaller cross section of the prestressed composite beam. The purpose is to provide a construction method in which the height is reduced to secure a wider communication surface and a geometric space, and the bridge is slender.

       Conventionally, the construction is performed by the method as shown in FIG. 1. In detail, FIG. 1 (a) shows the constant moment member 7 and the parent moment at the span splitting point 9 so as not to be affected by fatigue in steel and concrete. The length of the two-stage continuous prestressed composite beam becomes 2L if the length between the alternating 11 and the pier 12 is L. This length is divided into a constant moment member (7) and a parent moment member (8) at 0.825L to produce a steel material, but the steel material (2) of the positive moment member is produced by giving a predetermined rise (1), and the steel material of the parent moment member. (3) is manufactured without giving rise (1). Figure 1 (b) is a structural diagram showing a process of applying a pre-flection load (4) to the positive moment member steel material (2) is made to bend the steel material 2 of the positive moment member in the opposite direction of the upward rise (1). Figure 1 (c) is to cast the lower casing concrete (5) to the steel material 2 of the positive moment member bent downward constrains the rise (1) deformed downward and when curing of the lower casing concrete (5) is completed The reflection load 4 is gradually removed to introduce a compressive force to the lower casing concrete 5 to produce the positive moment member 7, and the parent moment member 8 is manufactured with the concrete poured on the lower edge side. Fig. 1 (d) is a structural diagram showing the produced constant moment member 7 and the parent moment member 8, and Fig. 1 (e) uses the high tension bolt for the constant moment member 7 and the parent moment member 8; Is a structural diagram showing a state of connection. FIG. 1 (f) is a structural diagram showing a state in which the top plate and the connection part concrete of the moment moment member 7 and the parent moment member 8 are poured, and FIG. 1 (g) is a structure diagram showing a state where the top concrete is cured and completed. . FIG. 1 (h) is a structural diagram showing the spanning point 9 and the constant moment section and the parental section, and the spanning point 9 divides the constant moment section and the parental section to minimize fatigue stress acting on the steel. It is positioned at 0.825L which is larger than 0.75L. The reason is to reduce the fatigue of concrete and steel caused by the discontinuous change of the moment of moment and the moment of parent connection when the load of the vehicle is loaded.

       The prestressed continuous composite beam manufactured in this way has a problem in that it is impossible to add stress reduction due to concrete creep deformation and dry shrinkage, resulting in excessive cross section.

The present invention has been proposed to improve the above problems, the bending moment generated in the secondary steel by forming a slant cut portion in the connection portion of the steel when the continuous prestressed composite beam is made and the slant cut portion in contact with each other when connecting By connecting the prestressed composite beam and casting concrete on the upper concrete and the connecting part to reduce the amount of bending moment generated in the static moment member, the bridge is sharpened while reducing the width of the girder while maintaining structural stability. There is an advantage that can secure more water passing area.

       The present invention relates to a construction method for continuous prestressed composite beams using diagonal cutouts formed in steel at the spanning points of continuous prestressed composite beams. (9) divided into a constant moment member (7) and the parent moment member (8), but in the production of the constant moment member (7) the pre-flexion load ( 4) is loaded and changed to a downward rise, and after the restraint concrete is poured into the lower end of the steel material 2 to form the lower casing concrete 5, the preloaded load 4 is gradually removed to compress the compressive force (23). In the case of manufacturing the parent member (8), only the bottom concrete is poured into the steel (3), and the steel (3) is connected to each other at the split point (9), and the upper plate and the connection. The concrete is poured into the part 30 to produce a continuous prestressed composite beam bridge.

       At this time, an oblique cut portion 20 formed by diagonally cutting the steel materials 2 and 3 is formed at the connection part 30 of the steel forming the positive moment member 7 and the parent moment member 8. When the interval 24 having a size of 1 to 3 cm is formed in a “V” shape, and the positive and minor moment members 7 and 8 are connected to each other to produce a continuous composite beam, the diagonal cut portion 20 formed in the steel material is formed. After removing the gap (24) formed by the contact with the diagonal cut portion 20 to each other and connected using a high-strength bolt, and when the concrete is poured into the upper concrete and the connecting portion 30, the bending acting on the constant moment member (7) Part of the moment amount is canceled by the restoring moment, which is the second moment generated in the steel by the connection of the diagonal cut portion 20, the amount of bending moment acting on the positive moment member 7 is reduced, the prestress of a safe and slender structure To build a continuous bridge It is characteristic that there is.

       Hereinafter, the configuration of the present invention with reference to the accompanying drawings in detail as follows.

Figure 2 (a) (b) (c) (d) (e) is a view showing the connection between the positive moment member and the parent moment member formed with an oblique cut portion in the steel material of the present invention using a high-tensile bolt to each other. (a) is a moment diagram for the fixed load action of a general continuous prestressed composite beam, and the moment inflection point and span split point (9) are indicated, and the hatched parts indicate the allowable lengths for the fatigue of steel (2,3) and concrete. . The allowable length by the above calculation can be expressed as 0.825L-0.75L = 0.075L. FIG. 2 (b) illustrates the connection of steel materials using high tension bolts to generate secondary moments generated by connecting diagonal cuts 20 to steels 2 and 3 of the positive and secondary moment members 7 and 8. As a diagram showing one state, when the diagonal cut portions are in contact with each other, a load acting on the intermediate point is 2P, a tensile force 22 is generated at the upper end of the prestress girder, and a compression force 23 is generated at the lower end.

(C) of FIG. 2 (c) is a diagonal line with the connecting portion 30 of the steel materials 2 and 3 constituting the constant moment member 7 and the parent moment member 8 so as to maintain the interval calculated at the time of design. An oblique cut 20 is formed, where the spacing 24 is 1 to 3 cm and the preferred spacing 24 is to maintain 2 cm.

(2) of FIG. 2 (c) shows that the diagonal cut portions 20 formed at the connecting portions 30 of the steel materials 2 and 3 are connected to each other using high tension bolts. When the diagonal cutouts 20 are connected to each other so that the diagonal cutouts 20 are in contact with each other so as to be connected to each other by bolts so that secondary moments are generated in the steel materials 2 and 3 by the intervals 24. Thus, when connecting the steel (2, 3) without a gap 24, as shown in the drawing, the tensile force 22 is applied to the upper portion of the steel (2, 3), the compression force 23 is applied to the lower portion of the steel . Therefore, the design compressive force acting on the positive moment member 7 can be reduced by such a secondary moment, so that the cross section can be reduced, so that the width of the girder can be reduced.

Fig. 2 (d) shows a moment diagram when the diagonal cut portions of the steel are connected to each other. At this time, the amount of moment generated in the diagonal cut portion 20 is represented by the product of the distance and the force, it can be represented by the value of ΔM = P.L. Where L represents the span length and P represents the force generated by the oblique cut 20.

FIG. 2 (e) is a diagram showing the change of moment when the diagonal cuts 20 are brought into contact with the steel materials 2 and 3, and 1) of FIG. 2 (e) is a joint connection of the diagonal cuts 20. FIG. The moment diagram when the applied force 2P is applied is expressed as ΔM = PL. 2 (e) is a moment diagram due to the fixed load of the two span continuous beam, and a moment inflection point is formed at 0.75L. 3 (e) of FIG. 2 (e) is a moment diagram showing the sum of the moment due to the joint connection of the oblique cut portion 20 and the moment due to the fixed load, and is the result of 1) +2) of FIG. Due to this, the length of the constant moment section is formed at 0.75L by the fixed load, but a change occurs depending on the size of the interval 24 of the diagonal cut portion 20. That is, when the moments of 1) and 2) are combined, the moment value of the constant moment section is significantly reduced, which is a factor that can reduce the size of the cross section when constructing the cross section. 2 (e) of Figure 2 (e) shows that the maximum static moment occurs at the 0.375L position.

Equation 1

Is displayed. Where w is an equal load value and a variation that can vary from bridge to bridge.

 And the stress is

..... Equation 2

Z is the value of section modulus. The maximum moment value in 1) of FIG. 2 (e) is M = P.L.

△ m = -0.375P.L .... [Formula 3]

P denotes a load generated by the interval 24 of the oblique cut 20 and L denotes a distance between them.

The stress at this time is

Equation 4

Indicated by

again Equation 5

It may be represented as. Δl represents the interval 24 of the oblique cut 20 in FIG. 2 (c), and E is an elastic modulus indicating the characteristics of the cross section. By using this equation, it is possible to determine the amount of secondary moment generated by the interval 24 of the oblique cut 20. 3 (e) of FIG. 2 (e) which is a moment diagram in the state which adjusted the space | interval 24 of the diagonal cut part 20,

........... [Equation 6]

Can be displayed as

Where Δσ is Is displayed as

............... Equation 7

Is converted to

[Equation 8]

Is converted to

Equation 9

The displacement generated by the interval 24 of the oblique cut portion 20 can be calculated. In addition

Equation 10

Because of

Equation 11

The interval 24 of the diagonal cut portion 20 can be calculated as indicated by. The change in the constant moment section occurs through the interval 24 of the diagonal cut portion 20, and the change in the constant moment section is expressed by Equation 1. It is calculated by adding Δm = -0.375PL in Equation 2. Therefore, the moment change value is the moment due to the distributed load Calculated to -0.375PL. That is, the decrease amount of the constant moment cross-section is determined by the force P generated by the interval 24 of the oblique cut portion 20, and when the calculation is made in consideration of the allowable stress, the length of the constant moment section can be reduced by 5 to 10%. This also has a side effect of increasing the role of reducing the lower casing fatigue breakage by moving the connection portion 30 to the compression side. As shown in 3) of FIG. 2 (e), the cross section of the constant moment section changes according to the size of Δm, and the length of the constant moment section is 0.75L in 1) of FIG. After adjusting the space | interval 24, the change of a positive moment section arises from 0.6L-0.70L. This means a reduction in the amount of static moment, which is a secondary parabola. The reduced amount of static moment further reduces the cross section of the static moment, enabling the fabrication of continuous prestressed bridges of economical and low geometry space. As an example, a slight reinforcement point section reinforcement is required in a two span continuous beam, but the overall section reduction is about 5%.

3 (a) (b) (c) (d) (e) (f) (g) (h) show a method of manufacturing a continuous prestressed composite beam by the method of FIG. ) Is given the upward rise (1) to the constant moment member (7) to produce the steel (2), and the parent moment member (8) is produced from the steel (3) without giving rise, Figure 3 (b) FIG. 3 is a structural diagram showing a state in which a pre-flection load 4 is applied to the constant moment member 7, and FIG. 3 (c) shows a steel material 2 rising upward by applying a pre-flection load 4 to the constant moment member 7. 3 is a structural diagram showing a state in which the tensile force 22 is generated at the bottom of the steel material 2 by deflecting downward, and FIG. 3 (d) removes a load applied in advance after the confining concrete is poured into the constant moment member 7. The parent member 8 shows a state in which only concrete is poured. FIG. 3 (e) removes the preflection load 4 previously applied to the constant moment member 7, restraining the steel material 2 of the constant moment member 7 while restoring to the state of the first upward rise (1). 3 (f) shows a process of allowing the compressive force 23 to be introduced into the concrete. Figure 3 is a view showing a state connected to each other, as shown in Figure 3 (g) is a structural diagram showing a state in which the secondary moment is generated by using a high-tension bolt to contact the diagonal cut portion 20 to each other. The actual construction method is formed by forming the diagonal cut portion 20 on both sides of the steel (2, 3) connection by the interval (24) calculated at the time of manufacturing the steel (2, 3), these steel (2, 3) to each other Removing the gap 24 of the oblique cut portion 20 in the connection mounting step, and the oblique cut portion 20 is connected to each other and mounted, the internal stress which is a secondary moment to the steel (2, 3) easily generated. 3 (h) is a structural diagram showing a state in which concrete is poured on the upper plate and the connecting portion in a state in which internal stress, which is a secondary moment, is generated in the members by connecting the diagonal cut portions 20 in contact with each other.

The present invention is to make the connection by the division between the positions of the connection portion in the place without affecting the fatigue of the steel and concrete by making the pre-stressed composite beam continuously and the diagonal line to the connection portion of the steel forming the positive and secondary moment members When the cutouts are formed and the diagonal cuts are connected to each other, the gap between the diagonal cuts is eliminated, so that internal stress, which is a secondary moment, is generated in the steel, thereby reducing the amount of moment acting on the positive moment member. It is possible to reduce the cross section of the bridge because of this is a useful construction method that can be constructed with a beautiful bridge appearance.

1 (a), (b), (c), (d), (e), (f), (g), and (h) show a manufacturing process of a continuous prestressed composite beam according to the prior art.

Figure 2 (a) (b) (c) (d) (e) is a view showing the connection between the positive moment member and the parent moment member formed with an oblique cut portion in the steel of the present invention using a high tension bolt.

3 (a) (b) (c) (d) (e) (f) (g) (h) illustrate a method of manufacturing a continuous prestressed composite beam by the method of FIG.

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

1 ... rising from the top 2 ... steel with no positive moment

3 ... Steel in parent member part 4 ... Preflection load

5 ... lower casing concrete 6 ... release

7 ... Static moment member 8 ... Parent moment member

9 ... span split 11 ... shift

12 ... piers 20 ... oblique cut

22 ... tensile force 23 ... compression force

24 ... spacing 30 ... connection

Claims (4)

       In joining steels to manufacture prestressed composite beams continuously,        Formed to maintain a constant interval in the form of a "V" to form a diagonal cut portion formed by cutting the steel diagonally in the connection portion of the steel forming the pre-stressed composite beam and the parent moment member A continuous prestressed composite beam in which diagonal cuts are formed in a steel material.        The method of claim 1,        A continuous prestressed composite beam having an oblique cut portion formed in the steel, characterized in that the constant interval formed by the oblique cut portion is 1 ~ 3cm.        The method of claim 1,        Diagonal cuts are formed in the steel, characterized in that the cross-sectional reduction of the bridge is 5% of the cross-sectional area of the entire bridge by the second moment generated in the steel by connecting the diagonal cuts formed in the connection part of the steel to each other by using high tension bolts. Continuous prestressed composite beam.        In the method of manufacturing by connecting the prestressed composite beam continuously,        a) forming an oblique cut portion in the connection portion of the steel which has been provided with an upward rise in the positive moment member, and installing the oblique cut portion in the connection portion of the steel in a state where the parent moment member is not raised;        b) generating a tensile force at the bottom of the steel by imparting a preflexion load to the positive moment member to sag downward the steel that has risen upward;        d) removing the load applied in advance after the confining concrete is poured into the constant-moment member, the parent-ment member is to cast only concrete;        e) removing the preflection load applied to the static moment member in advance so that the compressive force is introduced into the constrained concrete while restoring the steel of the constant moment member to the initial upward rise state;        f) arranging the static moment member and the parent moment member on a pier and connecting them to the diagonal cuts provided in the connecting portion of the steel, which is the span split point, to be connected to each other and fixed with high tension bolts; And        g) connecting the slanted cut portion formed in the connection portion of the steel by using a high tension bolt to generate an internal stress which is a second moment in the steel, and casting concrete to the upper plate and the connection portion of the steel to complete the construction of the bridge; A continuous construction method for a continuous prestressed composite beam, in which an oblique cut is formed in a steel material.