KR100995114B1 - Method for introducing tension pre-stress using the slab - Google Patents

Abstract

The present invention relates to a method of introducing prestress, and more particularly, a tensile force for maximizing a moment effect while canceling all or a part of the compressive force applied to a member in order to introduce a prestress for pre-applying a warp in the opposite direction to a structural member that resists warpage. It relates to a technique for introducing prestress by.

The present invention is to separate the bottom plate is fixed to the upper portion of the bending resistance member in order to achieve the above object is fixed, and to install the jack in the separation between the bottom plate and the bottom plate by pushing the bottom plate Disclosed is a method of introducing tensile prestress of a bending resistance member using a bottom plate, characterized in that a tensile force is applied to an upper end of the bending resistance member fixed to a lower part of the plate.

By the introduction of the optimum prestress by the present invention, it is possible to design and construct an economical bending resistance structural member. Although the present invention is effective even in the case of concrete composite bridges, particularly in steel composite bridges using steel materials in which compressive forces adversely affect the design.

Tensile force, prestress, bottom plate, strand, hydraulic jack.

Description

Method for introducing tension pre-stress using the slab

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of introducing a prestress, and more particularly, to all of the compressive forces applied to a cross section to introduce a prestress (hereinafter referred to as "compression-prestress") that pre-applies a deflection in the opposite direction to a structural member that resists warpage. Alternatively, while canceling a part, the moment effect relates to a technique for introducing prestress (hereinafter, referred to as 'tension-prestress') by a tensile force to maximize.

This is mainly applied to structures such as bridges that fix the bottom plate on top of the bending resistance member, and more specifically, to increase the load carrying capacity of structural members that resist bending such as beams and girders used in structures such as bridges. The present invention relates to a technique for introducing pre-stress, but not only introducing compression-prestress to the tensile region of the structural member, but also introducing tension-prestress to the compression region. That is, by applying an axial compressive force on the lower end of the bending resistance member and an axial tensile force on the upper end of the beam, reducing the compressive force generated in the cross section of the beam to maximize the tension-prestress introduction method to maximize the moment effect by the prestress will be.

In general, in a bridge composed of a bending resistance member that resists bending such as a girder or a beam and a bottom plate installed on the upper portion, steel and concrete are mainly used for the bending resistance member. Particularly, in the case of steel composite bridges, the self and shared loads were resisted only by concrete slabs corresponding to steel castings and slabs. Prestress was introduced to resist external loads with a large compressive force acting in the axial direction of the beam.

The steel composite bridge is solved only by increasing the amount of steel used for the increase of the common load and the length of the bridge (the length between the bridge and the bridge), and the construction cost is relatively expensive compared to the concrete bridge. However, even in the case of a composite bridge, a method of introducing prestress has been attempted, but the compressive force adversely affects the steel and thus cannot use the prestress effectively. In addition, in the case of a concrete composite bridge, there is a disadvantage that the size of the cross-sectional specification is accompanied by a large compressive force due to prestress.

Referring to this in more detail through the drawings, as shown in Figure 1a, the compressive stress (+) is applied to the upper portion of the bending resistance member in the middle moment section of the span when the external load is applied and the tensile stress at the lower portion of the bending resistance member (-) Will work. For the same reason as described above, the prestress (FIG. 1B) that can cope with the stress is applied before this load is applied. In particular, in the case of concrete composite bridges vulnerable to tensile force, prestresses that can cancel the tensile stress are introduced before the tensile stress is applied. One typical method of such prestressing is post-tensioning, which is a method of introducing prestress by fixing an axially stretched strand in the lower portion of the bending resistance member.

When the compression-prestress is introduced as shown in FIG. 1B, the compressive force is applied in the axial direction of the member, and an inverse moment corresponding to the moment due to external load is generated. However, such a compressive force has a problem that adversely acts in the design of the structural member.

Accordingly, the present invention is to solve the above problems, firstly to introduce the pre-stress, and to introduce the optimum pre-stress to the structural member resisting the bending by applying only the bending without applying a compressive force to the structure.

That is, in a bridge or the like consisting of a bottom plate and a bending resistance structural member, the lower end of the bending resistance structural member is applied with an axial compressive force to introduce compression-prestress, while an tensile force is applied to the upper end of the bending resistance structural member by applying an axial tensile force. -To introduce prestress. That is, the compression-prestress and tension-prestress are simultaneously introduced to solve the compressive force applied to the cross section of the beam, and through the doubled compressive stress acting on the lower part of the bending resistance member and tensile stress acting on the upper portion of the bending resistance member. Disclosed is a tensile-prestressed introduction method which maximizes the moment effect to have only structurally beneficial effects on the bending resistant structural members.

Second, in order to solve the above problems, a means for introducing compression-prestress acting on the compressive force and tensile pre-stress acting on the tensile force should be provided. Generally, the prestress for introducing the compressive force can achieve its purpose relatively easily by using a tension member. However, it is a reality that there is a technical difficulty to introduce prestress with a tensile force. The present invention seeks to disclose a tensile-prestressed introduction method that is economical and highly efficient.

That is, the tension-prestress is introduced only by adjusting the construction order of the bottom plate installed on the upper portion of the bending resistance structural member and the hydraulic jack. Specifically, it is intended to disclose a method with excellent economics and workability that does not require cuts or even shields, steel wires or even steel bars in order to introduce tensile-prestress.

The present invention for achieving the above object is applied to a structure including a bending resistance member that is a structure that resists bending and a bottom plate fixed to the upper portion of the bending resistance member. More specifically, in the method of introducing the prestress to increase the load capacity of the bending resistance member, in order to reduce the moment generated in the bending resistance member by applying an axial compressive force to the lower end of the bending resistance member compression-prestress Introducing the tension-prestress by reducing the generated moment of the bending resistance member and applying an axial tensile force to the upper end of the bending resistance member to release the compressive force applied for the introduction of the compression-prestress. It discloses a prestress introduction method comprising a. By simultaneously applying tension-prestress and compression-prestress, the axial forces cancel each other out and maximize the moment effect.

The greatest feature of the present invention, and the most significant effect is to disclose a means capable of introducing the tensile-prestress economically and efficiently. That is, the tension-prestress separates and fixes the bottom plate fixed to the upper portion of the bending resistance member, and installs a jack at a spaced portion between the bottom plate and the bottom plate, and then extends and pushes the bottom plate. A tensile-prestressed introduction method of a bending resistance member using a bottom plate is disclosed, wherein a tensile force is applied to an upper end of the bending resistance member fixed to a bottom of the bottom plate. As described above, the present invention is a technique applied to the bottom plate to be installed on the bending resistance member and the bending resistance member. That is, the bottom plate is to be installed regardless of the introduction of the prestress, the present invention is to remove the bottom plate in order to be fixed to the bottom plate in order to install a jack between the bottom plate and the bottom plate by applying a compressive force to the bottom plate At the bottom of the bottom plate, the bending resistance member fixed to the bottom plate is subjected to a tensile force, thereby introducing tensile-prestress.

In addition, the bottom plate may be divided into a first bottom plate and a second bottom plate in an order of being fixed to the bending resistance member. In this case, the step of introducing the tensile-prestress, the step of fixing the first bottom plate on both ends in the longitudinal direction of the bending resistance member and the bending while forming a spaced apart from the first bottom plate at a predetermined interval Mounting a second bottom plate on the center portion of the resistance member (not placed on the bending resistance member) and installing a jack on the separation part, and tensioning the jack to apply a force to the bottom plate to the first bottom plate. The bending resistance member fixed to the plate may be made to act to the tensile force. Preferably, in order to prevent the second bottom plate from being injured in the process of receiving a pressure may be further provided with a prevention means.

According to the tensile-prestress introduction method of the flexural resistance structural member using the bottom plate of the present invention, it is possible to effectively use the prestress by canceling the compressive force applied during the introduction of the prestress, and consequently to maximize the moment effect, Can be reduced. That is, by introducing the optimal prestress, it is possible to design and construct an economically flexible bending resistance structural member. Although the present invention is effective even in the case of concrete composite bridges, particularly in steel composite bridges using steel materials in which compressive forces adversely affect the design.

Of course, it is apparent that the optimum design value can be derived by adjusting the amount of tension-prestress in consideration of the characteristics of the bending resistance member and the load applied to the structure.

In addition, the greatest difference from the prior art of the present invention is that the heterogeneous and remarkable effect is that the process of introducing tension-stress is very economical and easy. In other words, by removing the additional cost and technical difficulties by introducing the tension-prestress through the order of fixing the bottom plate, which is an essential element of the structure, and fixing it to the bending resistance member and the extension of the jack. Furthermore, the present invention is not limited to the material of bending resistance members such as concrete and steel, or the type of steel casting such as box type or plate type, and can be easily applied to any structure having fixing of the bottom plate and the bending resistance member. There is a wide range of benefits. Representatively, in terms of bridge design, it is possible to design long span bridges economically and with excellent constructability.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the tensile-prestress introduction method of the bending resistance structural member using the present invention will be described in detail. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the present embodiments are provided to those skilled in the art to make the disclosure of the present invention complete. It is provided for complete information.

1A to 1D are diagrams illustrating the stress of the bending resistance member according to the introduction of the existing pressure-prestress and the tension-prestress according to the present invention. Figure 1a shows the axial force and the moment generated by the self-load and the common load acting on the bending resistance member, Figure 1b is applied by compressive force to the tension of the bending resistance member in order to cancel the moment of Figure 1a When prestress is introduced, the axial force and moment generated in the bending resistance member are shown. In general, steel and concrete are mainly used for the bending resistance member that resists the bending used in the structure. Among them, the concrete is strong in compression but very weak in tension. Therefore, the bending resistance member made of concrete needs to eliminate the occurrence of tensile stress by introducing compression-prestress as shown in FIG. 1B. Of course, even in the case of steel, a method of introducing compression-prestress using a stranded wire has been attempted for economic construction by reducing the amount of steel used.

However, the introduction of compression pre-stress can cope with the moment due to the action of external load, but the compression force exerted in the axial direction to introduce the compression pre-stress acts adversely in the design of the bending resistance member. Therefore, the introduction of the prestress should only take the moment effect and a way to solve the compressive force should be taken. Therefore, as shown in FIG. 1C, a method of introducing tensile-prestress to the upper end of the bending resistance member is disclosed.

That is, in order to reduce the tensile stress generated in the tension portion of the bending resistance member due to the self-load and the common load acting on the bending resistance member, as shown in Figure 1b, the axial compressive force ( When the compression-prestress is applied by applying the direction of the arrow, a tensile stress (-) is applied to the upper part and a compressive stress (+) is applied to the lower part. In addition, in order to solve the axial compressive force for introducing the compression-prestress, as shown in Figure 1c, when the tension-prestress is introduced by applying an axial tensile force (arrow direction) to the upper end of the beam, the axial direction Tensile force acts, tensile stress acts on the upper beam, and compressive stress acts on the lower beam.

When the compression-prestress and the tension-prestress are simultaneously introduced into the bending resistance member, as shown in FIG. 1D, the axial force for introducing the compression-prestress acts as an axial compressive force (+) and the tension-prestress. The axial force for introducing N acts as an axial tensile force (-), which is offset. In terms of moment, the tensile stress (-) acting on the bending resistance member and the compressive stress (+) acting on the lower part act the same by the compression-prestress and the tensile-prestress, thus maximizing the third prestress. The effect of the prestress can be obtained. As a result, if the tensile and compressive forces are applied at the same time, the desired moment can be obtained with a small force.

Of course, the above description is representative of the case where the magnitude of the compressive force and the tensile force is the same, and when the material is vulnerable to the tension, such as concrete, it is preferable to apply a greater compression-prestress to the bending resistance member.

The tension-prestress introduction method according to the present invention will be described in detail with reference to the drawings. The present invention is always applicable if the bending resistance member and the bottom plate is fixed, but will be described in detail through the embodiment of the bridge in which the bending resistance member is typically used (more specifically, through a steel box-type steel composite bridge To explain). In modern society, where the importance of public design is emphasized, the bridge has become an important element as well as its appearance, and according to the present invention, it is easy to design and construct a low failure span bridge which is economical and beautiful in appearance.

2A and 2B are schematic diagrams for explaining tensile-prestress introduction of a flexural resistance structural member using a bottom plate as an embodiment according to the present invention. In general, bridges are completed by placing girders (girders or steel castings) such as steel boxes or I-beams on the pier, constructing floor plates (or top plates, slabs), and finishing road pavement and auxiliary facilities. The girder corresponds to the bending resistance member 10 of the present invention. The bending resistance member 10 plays a structural role as a member for resisting bending. 2A is a view illustrating the construction of the bottom plate 30 on the steel box type bending resistance member 10 during the construction step of the bridge. The bottom plate 30 is formed by installing a formwork as a temporary facility in the field and placing concrete and a method of mounting the base plate (precast) in the factory or the site (top) to the upper portion of the bending resistance member (10) All. 2A illustrates a process of mounting the prefabricated bottom plate 30 on the bending resistance member 10. In this case, the bottom plate 30 corresponds to a plurality of studs 20 welded to the top surface of the bending resistance member 10 to fix the bending resistance member 10 and the bottom plate 30. ) Is formed. The stud 20 is inserted into the shear pocket 40 to mount the bottom plate 30 on the bending resistance member 10, and then the shear pocket 40 is concrete (preferably non-contraction grout). The bottom plate 30 is fixed to the bending resistance member 10 and synthesized by pouring and curing.

The greatest feature of this embodiment in the above step is divided into two or more bottom plate 30 divided construction, with a spaced portion 31 between the divided bottom plate 30, concrete placing on the front pocket 40 Fixing the bottom plate 30 to the bending resistance member 10 through the preferential application of both end portions of the bending resistance member 10. That is, the central portion of the bending resistance member 10 is not synthesized with the bottom plate 30, but both ends of the bending resistance member 10 are constructed to be combined with the bottom plate 30. According to FIG. 2B, the front pocket 40 is not filled with the front pocket 40, but the front pocket 40 at both ends is filled with concrete.

Then, the hydraulic jack 70 (various types of pressurizing means may be applied, but preferably hydraulic jack) is installed on the spaced portion 31 between the bottom plate 30 and the hydraulic jack 70 is extended to extend the bottom plate 30. Tensile force is transmitted to the bending resistance member 10 fixed to both ends of the bottom plate 30 through. This introduces tension-prestress.

Of course, when placing the bottom plate 30 in the field to install the formwork with the spaced portion 31 but the center of the studs 20 welded to the upper surface of the bending resistance member 10 is covered with the bottom plate 30 concrete It is apparent that the hydraulic jack 70 may be installed at the spaced portion 31 so as not to be buried at the time of placing, and thus the tensile force may be transmitted to the bending resistance member 10.

Through the drawings of another embodiment to which the present invention is applied in more detail will be described the construction of the bending resistance member and the bottom plate of the bridge to which the present invention is applied. 3 is a perspective view of a bending resistance member and a bottom plate of a bridge in which a tension-prestress is introduced according to the present invention.

As shown in the drawing, there is a box-shaped girder corresponding to the bending resistance member 10, and at the upper portion of the bending resistance member 10, a second bottom plate 30b of concrete material having a large area is disposed at the center thereof. On both sides of the bending resistance member 10, the concrete first bottom plate 30a is disposed in a long rectangular shape at regular intervals from the second bottom plate 30b, and a lower end portion of the bending resistance member 10 is disposed. The stranded wire anchorages 11b are fixed to the ends of the width direction at regular distances in the longitudinal direction, respectively, and the stranded wires 11a are respectively fixed between the stranded wire anchorages 11b facing each other in the longitudinal direction. Here, the strand wire anchorage (11b) and the strand wire (11a) is provided to apply compression-prestress to the bending resistance member (10).

Shear pockets on the first bottom plate 30a and the second bottom plate 30b for fixing the bottom plates 30a and 30b to the bending resistance member 10 at regular intervals along the length direction in both width directions. A plurality of the grooves 40 are formed in the shape of the recess, and the hydraulic jack 70 is provided in the space between the first bottom plate 30a and the second bottom plate 30b, that is, the separation part 31 in both width directions. The hydraulic jacks 70 are disposed in the same manner in the space between the first bottom plate 30a and the second bottom plate 30b on the opposite side. Here, the hydraulic jack 70 is installed to apply tension-prestress to the bending resistance member 10.

Thus, after the prestressing equipment is installed in the bending resistance member 10, the first bottom plate 30a, and the second bottom plate 30b, the stranded wire 11a provided inside the bending resistance member 10 is tensioned. By applying compression-prestress, and applying hydraulic pressure to the hydraulic jack 70 disposed in the space between the first bottom plate 30a and the second bottom plate 30b, tension-prestress is applied to the bending resistance member 10. .

Here, the first bottom plate 30a is fixed to the bending resistance member 10 before the prestress is introduced, and the second bottom plate 30b is fixed to the bending resistance member 10 after the prestress is introduced.

Therefore, the prestress, which may be called a third prestress, is finally acted on the bending resistance member 10 by the simultaneous action of the compression-prestress and the tension-prestress, which will be described later in detail by dividing step by step. Figures 4a to 4e is a front sectional view showing in step by step the pre-stress introduction method according to the present invention to the bottom plate and the bending resistance member, Figure 5a is a plan view of Figure 4e, Figure 5b is a pre-stressed state of the present invention A plan view of the is shown.

First, as shown in FIG. 4A, the bending resistance member 10 is mounted on a support point, and at this time, a stud for connecting and fixing the bottom plate to the bending resistance member 10 on the upper portion of the bending resistance member 10 ( 20) is welded, and the strand wire anchorage opening 11b is provided in the lower end part in the said bending resistance member 10. As shown in FIG.

Next, as shown in FIG. 4B, the first bottom plate 30a and the second bottom plate 30b are installed by mounting a concrete bottom plate on an upper portion of the bending resistance member 10, but the first bottom plate is provided. In the plate 30a and the second bottom plate 30b, a front pocket 40 having a space as a recess in which the stud 20 is inserted is formed. Since the second bottom plate 30b is not fixed to the bending resistance member 10 when the prestress is applied to the second bottom plate 30b, it is preferable to install the injury prevention means 60 to prevent the damage. Do.

Next, as shown in FIG. 4C, the first bottom plate 30a is respectively mounted on the bending resistance member 10 by pouring the back bottom plate 40 formed in the first bottom plate 30a into concrete and backfilling it. Fix the tension wire 11a inside the bending resistance member 10 and fix it over the strand anchorage opening 11b to apply compression-prestress by applying an axial compression force (arrow direction) to the bending resistance member 10. By applying hydraulic pressure to the hydraulic jacks 70 disposed in the space between the first bottom plate 30a and the second bottom plate 30b, respectively, the length of the hydraulic jack 70 is increased in the axial tensile force (arrow direction) to the bending resistance member 10. To introduce tension-prestress.

At this time, even if tension-prestress is applied by the hydraulic jack 70, as described above, the anti-floating means 60 is installed on the second bottom plate 30b, so that the second bottom plate 30b is a bending resistance member ( The problem that comes up without being fixed in 10) does not occur. Next, as shown in FIG. 4D, the shear pocket 40 formed in the second bottom plate 30b is poured into the concrete to fix the second bottom plate 30b to the bending resistance member 10. Let's do it.

Next, as shown in FIGS. 4E and 5A, the remaining space 31, that is, the space remaining between the space between the first bottom plate 30a and the second bottom plate 30b except for the space in which the hydraulic jack 70 is installed. By pouring in concrete, the first bottom plate 30a and the second bottom plate 30b are connected to each other.

Next, as shown in FIG. 5B, after removing the hydraulic jack 70, the removed space is poured into concrete and fixed to the bending resistance member 10 on the bending resistance member 10 as shown in FIG. When the first bottom plate 30a and the second bottom plate 30b are completely connected to each other to form a single concrete bottom plate 30, compression-prestress and tensile-prestress are introduced to the bending resistance member (maximum moment effect). 10) and the composite fixed bottom plate 30 thereon is completed.

Therefore, due to the simultaneous action of the compression-prestress and the tension-prestress, as described above, the axial force acting on the cross section of the bending resistance member 10 is canceled, and the tensile stress on the top of the bending resistance member 10 is the bending resistance member. The lower part of (10) introduces a third prestress acting on the compressive stress, thereby constructing an efficient structure that effectively responds to external loads (such as self load and shared load).

As described above with reference to the drawings illustrating an embodiment according to the present invention, the present invention is not limited by the embodiments and drawings disclosed herein, but by those skilled in the art within the scope of the technical idea of the present invention Of course, various modifications may be made. That is, the first floor plate 30a, which is relatively small and easy to manufacture in the factory by applying the precast concrete floor plate 30 and the site construction concrete floor board efficiently according to the site situation, uses the precast concrete floor plate, The second floor plate 30b, which may be a problem for site adaptability when manufacturing a factory as a large-scale floor plate, is subjected to field construction, but the tension-prestress is introduced after the block-out without embedding the stud 20. After that, you can consider the method of pouring concrete to the block-out part.

1A to 1D are views representing axial force and moment acting on a bending resistance member.

2A and 2B illustrate a prestress introduction process as an embodiment of the present invention.

Figure 3 is a perspective view of the bottom plate and the bending resistance member is applied tension-prestress introduction method as another embodiment according to the present invention

Figures 4a to 4e is a front cross-sectional view showing the compression-prestress and tensile-prestress introduction method according to the present invention in the bottom plate and the bending resistance member as another embodiment of the present invention in order

5A is a plan view of FIG. 4E, and FIG. 5B is a plan view in the final state to which the prestress of the present invention is applied.

<Explanation of symbols for main parts of the drawings>

10: bending resistance member 11a: stranded wire

11b: stranded anchorage

20: stud 30: bottom plate

31: spacing

30a, 30b: 1st bottom plate, 2nd bottom plate 40: shear pocket

60: injury prevention means 70: hydraulic jack

Claims (4)

delete In the method comprising a bending resistance member that is a structure that resists bending and a bottom plate fixed to the upper portion of the bending resistance member, a method of introducing a prestress to increase the load capacity of the bending resistance member, Introducing a compression-prestress by applying an axial compressive force to the tension portion of the bending resistance member to reduce the tensile stress generated in the tension portion of the bending resistance member; and Introduces a tensile-prestress acting as an axial tensile force on the compression portion of the bending resistance member to reduce the compressive stress generated in the compression portion of the bending resistance member and to release the compression force applied to introduce the compression-prestress. Comprising; In the step of introducing the tension-prestress, the bottom plate fixed to the upper portion of the bending resistance member is separated but fixed and spaced apart, by installing a jack in the separation between the bottom plate and the bottom plate to push the bottom plate And a tensile force acts on the upper end of the bending resistance member fixed to the bottom of the bottom plate. The method of claim 2, wherein the bottom plate is divided into a first bottom plate and a second bottom plate in the order of being fixed to the bending resistance member, the step of introducing the tension-prestress, Fixing the first bottom plate on both ends in the longitudinal direction of the bending resistance member; Mounting a second bottom plate at a center portion of the bending resistance member while forming a spaced portion spaced apart from the first bottom plate by a predetermined distance; And And installing a jack on the separation part, and tensioning the jack to apply a force to the bottom plate so that a tensile force acts on the bending resistance member fixed to the first bottom plate. Tensile-prestressed introduction method of bending resistance member using. The bending resistance member using a bottom plate according to claim 3, further comprising an anti-floating means for preventing the second bottom plate from being injured when the second bottom plate is mounted at the center of the bending resistance member. Of tensile-prestress introduction.

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