KR101057409B1 - Hollow prestressed concrete girder and method for manufacturing thereof - Google Patents

Abstract

PURPOSE: A hollow prestressed concrete beam and a manufacturing method thereof are provided to effectively control tension cracks on the top of the concrete beam when compressive force is applied to the beam. CONSTITUTION: A hollow prestressed concrete beam comprises first blocks(10), second blocks(20), third blocks, a fourth block(40), tendon ducts, tendons, and a fixing units. The first blocks have first concave parts. The second blocks have second concave parts. The bottom ends of the third blocks are inserted into the second concave parts, and the top ends are exposed to the outside. The fourth block has a concave part for connecting the first blocks. The tendon ducts pass through one first block and the second blocks. The tendons are inserted into the tendon ducts. The fixing units are formed in both ends of the tendon ducts and fixes the tendons.

Description

Hollow Prestressed Concrete Girder and Method for manufacturing description

The present invention relates to a hollow prestressed concrete beam and a multi-stage fabrication method. More specifically, the present invention relates to a hollow prestressed concrete beam and a multi-stage fabrication method. Pre-stressed concrete beams through multi-stage tension and the method of fabricating the lower and end blocks by pre-cast line tension and the top of the central beam to the cast in place to perform the secondary tension.

In bridges with reinforced concrete beams, it is very common to introduce prestresses on the lower side of the neutral axis of the beam to control the tensile stress of the concrete below the neutral axis and to increase the length of the span. When the prestress is introduced into the beam, a tensile force is applied to the upper side of the beam in the beam arrangement state, and therefore, the introduction of the prestress is limited because it is vulnerable to the tension due to the properties of the concrete material. Such limitations have led to the use of multistage tensions to address the difficulty of introducing sufficient prestress. The multi-stage tension method is composed of the steps shown in (a) to (g) of Figure 1, Figure 1 shows the construction sequence of the two-span continuous bridge of the multi-stage tension method. The construction sequence is first made of the beam 100 as shown in Figure 1 (a), and then tensioned using the anchorage of the primary tendon 200 (hereinafter referred to as end anchorage) on the beam end surface as shown in Figure 1 (b). . The first strained beam is mounted on the bridge substructure 300 such as alternating or pier as shown in FIG. 1 (c), and concrete is poured into the continuous part on the slab 400 and the pier as shown in FIG. When the slab load is additionally applied to the beam, the prestress can be additionally introduced. When the continuous portion and the slab concrete reach the predetermined strength, as shown in FIG. Make the car nervous. When the secondary tension is completed, as shown in Fig. 1 (f) to complete the bridge by installing a packaging and protective measures or a protective wall (500). Since the side anchoring opening is exposed to the outside to allow the tension work, the tension work is possible even after the completion of the bridge as shown in FIG. 1 (g). Therefore, it is also possible to use a third tension at the side anchorage by using extra unattached steel wire preliminarily installed or extra duct installed when the structural performance of the bridge deteriorates after a long time. On-site casting is mainly used for slab slabs, but in some cases precast slabs or precast panels are used. In this case, a method of installing a precast panel or precast slab in the beam and performing secondary tension before composing it to the beam is mainly used.

The higher the tensile force introduced to the primary tendon is structurally advantageous, but in order to introduce a larger tensile force, the longer the longitudinal length of the beam in the tendon arrangement, the better. However, when the length of the beam increases in length, the size of the beam increases and the self-weight also increases, thereby eliminating the advantage of the amount of tensile force introduced. On the other hand, since excessive initial tension may cause cracks on the upper surface of the beam, this is also an important parameter defining the limit of tension.

In the case of the conventional prestressed concrete beams are mostly made of the "I" -shaped cross-section there is a limit in manufacturability or stability during construction. In addition, since the amount of tensile force introduced by the crack generated on the upper surface during the prestressing is limited, there is a possibility that problems such as cracking at the lower part of the beam occur when live load is applied due to limited prestressing. to be.

Due to this problem, various methods for maintaining cracks in the beam have been proposed.

The present invention is derived to solve the problems of the conventional prestressed concrete beam described in the background, the problem to be solved by the present invention is more stable by effectively controlling the tensile stress of the beam upper surface generated when the compression force is introduced into the beam It can be used to reduce the need for maintenance, and to provide a hollow prestressed concrete beam and its manufacturing method that can improve the ease of manufacture and construction stability.

The present invention as a means for solving the above problems,

In prestressed concrete beams used for bridges,

A pair of first blocks disposed at both ends and facing each other and having recesses recessed in an end direction, the first block being made of reinforced concrete material;

A plurality of second blocks disposed between the pair of first blocks and provided with recesses downwardly and made of reinforced concrete material;

A lower third part inserted into a groove part of the second block and an upper end part exposed to the outside of the groove part and having a light weight third block for forming a hollow in the beam;

The second block in a space formed by a virtual straight line connecting the pair of first blocks with the first block and the second block disposed and a third block inserted into a groove of the second block; A fourth block made of reinforcing steel and concrete installed and poured in a space except for the third block;

A plurality of tendon ducts connected from the first block of any one of the pair to second ones through the second blocks;

A plurality of tendons inserted into the plurality of tendons ducts; And,

Fixing means provided at both ends of the tendon duct to fix the tendon under tension; It provides a prestressed concrete beam comprising a.

The tendon duct is a first tendon duct disposed without changing the height in the vertical direction from the bottom of one of the first block to the bottom of the other first block through the second block,

It is preferred to consist of a second tendon duct having a similar profile in a gentle "U" shape to extend from the center or top of one first block to the center or top of the other first block via the second block.

The third block is preferably a lightweight material that can withstand the pressure of the cast-in-place concrete for the formation of the fourth block, such as foamed styrene, a box made of plastic, and is capable of forming the hollow part originally planned.

In addition, the present invention,

In the manufacturing method of the prestressed concrete beam used for the bridge,

A first block provision step of providing a pair of first blocks disposed at both ends and facing each other and having recesses recessed in an end direction;

A second block provision step of providing a plurality of second blocks disposed between the pair of first blocks and recessed downwardly to provide a plurality of second blocks having a cross-sectional shape similar to a '凹';

A tendon duct preparing step of preparing a plurality of tendon ducts connected from the first block of any one pair of the pair to the other one first block;

Disposing a second block between the pair of first blocks;

A first tensioning step of pressing the first blocks and the second blocks in a direction in which the first blocks and the second blocks are close to each other by inserting the tendons into a part of the tendon duct after the placing step is completed and introducing a tensile force;

The lower end portion is inserted into the groove portion of the second block and the upper end portion is exposed to the outside of the groove portion is provided with a third block to provide a lightweight third block for the effect of forming a hollow in the beam inserted into the groove portion of the second block step;

After the installation of the third block is completed, the reinforcing bar is installed and installed in the space except the second block and the third block among the spaces formed by the virtual straight lines connecting the pair of first blocks to each other. A fourth block installation step of pouring; And,

A second tension step of pressing in the direction in which the first blocks and the second blocks are close to each other by inserting the tendon in the remaining tendon duct in which the tendon is not inserted in the first tension step and introducing and pulling tension force; It provides a prestressed concrete beam manufacturing method comprising a.

The tendon duct provided in the tendon duct preparation step,

The tendon duct is a first tendon duct disposed without changing the height in the vertical direction from the bottom of one of the first block to the bottom of the other first block through the second block,

It is preferred that the second tendon duct has a similar profile in a gentle "U" shape to extend from the center or top of one first block to the center or top of the other first block via the second block.

The first tensioning step is performed by inserting tendons in the first tendon duct,

Preferably, the second tensioning step is performed by inserting tendons in the second tendon duct.

The third block inserted into the groove of the second block is more preferably a lightweight material that can withstand the pressure of the cast-in-place concrete for the formation of the fourth block, such as foamed styrene and a plastic box, and is capable of forming the hollow part originally planned. Do.

According to the present invention, it is possible to provide a hollow prestressed concrete beam and a method for manufacturing the same, which can be used more stably and require less maintenance by effectively controlling the tensile cracking of the beam upper surface generated when the compressive force is introduced.

In addition, by appropriately adjusting the width of the concrete block it is possible to reduce the number of beams or the height of the beam compared to the conventional I-beam.

In addition, it has a box shape as compared to the conventional I-beam, it is easy to reinforce reinforcement, formwork, etc., and the stability and handleability to conduction during construction is improved.

1 is a view showing the construction sequence of a two-span continuous bridge of the multi-stage tension method.
2 and 3 are views for explaining the arrangement of the first block, the second block and the third block of the prestressed concrete beam according to an embodiment of the present invention.
4 is an enlarged view of part IV shown in FIG. 3;
5 is a view showing a state in which a fourth block is installed.
FIG. 6 is an enlarged view of part VI shown in FIG. 5; FIG.
7 is a view for explaining an embodiment including a tendon for re-tension.
8 is an enlarged view of part V shown in FIG. 7;
9 is a view for explaining an arrangement of tendon ducts;
10A to 11 are views for explaining the advantages of the present invention.

Hereinafter, with reference to the drawings will be described a prestressed concrete beam and a method of manufacturing the same according to an embodiment of the present invention to provide specific details for carrying out the present invention.

2 and 3 are views for explaining the arrangement of the first block, the second block and the third block of the prestressed concrete beam according to an embodiment of the present invention, Figure 4 is an enlargement of the IV portion shown in FIG. 5 is a view showing a state in which a fourth block is installed, FIG. 6 is an enlarged view of part VI shown in FIG. 5, FIG. 7 is a view for explaining the arrangement of the tendon duct, and FIGS. It is a figure for explaining the advantage of this invention.

The prestressed concrete beam according to the present embodiment is used for a bridge and a slab and a protection facility are installed on the top of the beam. In FIG. 1 the beam is indicated at 100 and the slab is indicated at 400.

Prestressed concrete beam of the present embodiment is the first block 10, the second block 20, the third block 30, the fourth block 40, tendon duct 50, tendon 60 and fixing means 70 It is composed of

The first block 10 is arranged at both ends, that is, the alternating or pier side, the concave portion 11 is provided in the end direction on the side facing each other. The first block 10 is made of reinforced concrete material, the reinforcement is reinforced in the interior of the concrete is not shown for convenience in the city.

As shown in FIG. 3, the second block 20 is disposed between the pair of first blocks 10, and as illustrated in FIG. Similar to the 凹 'shape.

In the present embodiment, the first block 10 and the second block 20 are manufactured by precasting at a manufacturing site provided near the site, or are manufactured at a precast manufacturing factory and transported to the site.

The third block 30 has a lower end inserted into the groove 21 of the second block 20 and the upper end is exposed to the outside of the groove 21 and is a lightweight block for imparting a hollow effect to the beam. . The third block 30 is made of a material capable of forming the hollow portion originally designed to withstand the pressure of the cast-in-place concrete, and foamed styrene (styrofoam) or a plastic box inside is used. The shape may be made of wood, steel sheet or the like.

As shown in FIG. 3, the fourth block 40 includes the first block 10 and the second block 20, and the third block 30 includes the groove 21 of the second block 20. Reinforcing bars are installed and poured, except for the second block 20 and the third block 30, which are formed by a virtual straight line connecting the pair of first blocks 10 to each other in the inserted state. It is a block made of and concrete. For this purpose, an external formwork is required in the manufacturing process of the fourth block 40. Although the fourth block 40 includes the rebar, the reinforcement bar is a design matter, so it is difficult to accurately display the location and is not shown on the drawing for convenience of illustration. On the other hand, the first block 10, the second block 20, of course, the reinforcing bar is reinforcement, the reinforcing bar for forming the fourth block for the synthesis of the fourth block and the reinforcing bars for coupling Reinforced to be coupled to the reinforcing bar of the fourth block 40 disposed at the site of the reinforcement is exposed to the first block 10 and the second block 20 is also omitted for convenience of illustration.

The tendon duct 50 accommodates tendons for applying compressive force to the blocks in a state where the first block 10, the second block 20, the third block 30, and the fourth block 40 are assembled. It is space to do it. The tendon duct 50 is connected to the first block 10 through the second block 20 from one of the first block 10, the first block 10 and the second block ( 20) is formed during the precast process.

The tendon duct 50 includes a first tendon duct 51 and a second tendon duct 52. The first tendon duct 51 is a second block 20 from a lower portion of the first block 10. The first tendon duct 52 is disposed without changing the height in the vertical direction up to the bottom of the other first block 10, and the second block 20 is disposed from the center or the upper portion in the height direction of the first block 10. It is formed along a profile similar to a gentle "U" so as to run through) to the center or top of the other first block 10. Although the arrangement of the first tendon duct 51 and the second tendon duct 52 is schematically shown in FIG. 9, the exact profile is determined by design in consideration of the magnitude of the tensile force introduced to the tendon.

The tendon 60 is inserted into the tendon duct 50 to introduce a compressive force to the beam.

The tendon 60 includes a first tendon 61 and a second tendon 62, and the first tendon 61 applies a compressive force to the beam in a state accommodated in the first tendon duct 51, and the second tendon ( 62 applies a compressive force to the beam in a state accommodated in the second tendon duct 52. In FIG. 9, the tendon duct 50 and the tendon 60 are shown by the same dotted line and are simultaneously displayed because they are arranged along the same profile.

As shown in FIGS. 4 and 6, the fixing means 70 includes wedges and fixing plates as means for fixing both ends of the tendon 60. Since the fixing means 70 generally uses a configuration used for the prestressed beam, further detailed description thereof will be omitted.

Hereinafter, one embodiment of the method of manufacturing the above-described prestressed beam will be described.

The prestress beam manufacturing method of the present embodiment includes a first block preparing step, a second block preparing step, an arranging step, a first tension step, a third block installation step, a fourth block installation step, and a second tension step.

The first block preparing step is a step of preparing a pair of first blocks 10 are disposed on both ends and are provided with concave portions 11 in the end direction on the side facing each other.

In the preparing of the second block, a groove part 21 disposed between the pair of first blocks 10 and recessed downward is provided to prepare a second block 20 having a cross-sectional shape similar to '凹'. .

The tendon duct provision step is to provide a tendon duct 50 for accommodating tendons in the first block 10 and the second block 20, the tendon duct 50 is any one of the first block ( Starting from 10) and passing through the second blocks 20, up to the other one first block 10 is provided. Tendon duct 50 is composed of a first tendon duct 51 and a second tendon duct 52, the first tendon duct 51 is a second block 20 from the lower portion of the first block (10) The first tendon duct 52 is disposed up to the bottom of the other first block 10 without changing in height, and the first tendon duct 52 is disposed from the central portion or the top in the height direction of the first block 10 to the second block 20. Are formed along a profile similar to a gentle "U" so as to run through to the center or top of the other first block 10.

The first block preparing step, the second block preparing step, and the tendon duct preparing step are performed at the same time during the precasting process, and are divided for convenience of description.

The disposing step is disposing the second blocks 20 between the pair of first blocks 10. The number of the second blocks 20 may be appropriately selected in consideration of the length of the second block 20, the span length, and the like.

In the first tensioning step, the first block 10 and the second block 20 are closer to each other by inserting the first tendon 61 into the first tendon duct 51 and introducing the tensile force into the tendon. Pressing to step. In other words, the compressive force is introduced into the first block 10 and the second block 20. The fixing of the first tendon 61 is made by the fixing means 70. The fixing means 70 is composed of a wedge and a fixing plate which are generally used.

In the third block installation step, the lower portion is inserted into the groove portion 21 of the second block 20 and the upper end is exposed to the outside of the groove portion 21 and has a light weight third block for forming a hollow in the beam. A step 30 is provided and inserted into the groove 21.

As described above, the third block 30 may be foamed styrene (styrofoam), a hollow plastic box, or the like, and may be molded and used according to the shape of the groove 21.

The order in time of the third block installation step is not very important. It only needs to be done before the fourth block installation step. The first tension step may be performed after the installation of the third block. The third block may be installed after the first tension step.

The fourth block installation step is the second block 20 and the third of the space formed by imaginary straight lines connecting the pair of first blocks 10 after the first tension step and the third block installation is completed Reinforcing the reinforcing bar in the space except the block 30 and the step of installing concrete to install the fourth block (40). In this case, the reinforcing bar can be prepared in advance by fabricating the reinforcing bar network, and in case of such construction, the construction period can be shortened.

In the second tensioning step, after the installation of the fourth block 40 is completed, the second tendon 62 is inserted into the second tendon duct 52 and a tension force is applied to the second tendon 62 and then the fixing means 70 is applied to the fixing means 70. It is a step of fixing by applying a compressive force to the beam.

When the second tension step is completed, the production of the prestressed concrete beam of the present embodiment is completed.

When the fabrication of the prestressed concrete beam is completed, it is installed on the piers or shifts, and the slab is installed as an upper structure, and if necessary, additional tension may be introduced by installing anchorages on the side of the first block. The prestressed beam has an advantage that it can be applied regardless of the type of bridge, such as a simple bridge or continuous bridge.

The action and effect of the above-described prestressed concrete beam of the present invention is as follows.

Prestressed concrete beams (hereinafter referred to as PSC beams) have a disadvantage in that tension stress is applied to the concrete at the upper end of the beam due to the introduction of tension during fabrication. As the tension is created in the state where only the necessary part of the lower part of the neutral shaft, which has no concrete and only compressive stress, is made, it is possible to introduce sufficient tension so that the compressive stress acts on the shear surface without the tensile stress on the upper end. There is an advantage. After the first tension step is completed, the second tension step is performed in a state in which the fourth block is manufactured, and thus, a large compressive force can be introduced while minimizing the tensile stress on the neutral shaft. The introduction of such a large compressive force exerts sufficient resistive stress even when a large live load is applied to the PSC beam during use, thereby minimizing tensile cracking due to tensile stress at the neutral axis of the PSC beam, that is, at the lower end of the PSC beam. Can prevent the performance degradation.

7 and 8 are views for explaining an embodiment including the retension tendon, Figure 8 is an enlarged view of the portion shown in Fig.

In order to use the beam when additional prestressing is required during the use of the bridge, grooves are provided in the side of the first block 10 shown in FIG. When the tension by the existing tendons (61, 62) is lowered by introducing an additional tension to maintain the continuous tension.

10A to 11 are diagrams for explaining another effect of the present invention.

In the present invention, the PSC beam is manufactured in the form of a hollow box. By increasing the width of the beam, instead of using five I-type beams as shown in FIG. 9A, three beams can be used as shown in FIG. 9B. You can also expect the effect. The height h of the beams shown in FIGS. 9A and 9B are the same.

On the other hand, as shown in Fig. 11, a beam having a larger width d2 (shown on the right side in the drawing as a beam according to the present invention) than the width d1 of the I-type beam (shown on the left side in the drawing) is used. As a result, the effect and effect of producing the beam at a lower height h2 than the height h1 of the I-beam can be expected.

Although the following provides specific details for the practice of the present invention by describing the preferred embodiment of the present invention, the technical idea of the present invention is not limited to the described embodiment, the scope does not deviate from the technical idea of the present invention It can be embodied in various forms of prestressed concrete beams and manufacturing methods therein.

10: first block
20: second block
30: third block
40: fourth block
50: tendon duct
60: tendon
70: fixing means

Claims (7)

In prestressed concrete beams used for bridges,
A pair of first blocks disposed at both ends and facing each other and having recesses recessed in an end direction, the first block being made of reinforced concrete material;
A plurality of second blocks disposed between the pair of first blocks and provided with recesses downwardly and made of reinforced concrete material;
A lower third part inserted into a groove part of the second block and an upper end part exposed to the outside of the groove part and having a light weight third block for forming a hollow in the beam;
The concave portion of a space formed by an imaginary straight line connecting the pair of first blocks to each other in a state in which the first block and the second block are disposed and a third block is inserted into a groove portion of the second block; A fourth block made of reinforcing steel and concrete installed and poured in a space except for the second block and the third block;
A plurality of tendon ducts connected from the first block of any one of the pair to second ones through the second blocks;
A plurality of tendons inserted into the plurality of tendons ducts; And,
Fixing means provided at both ends of the tendon duct to fix the tendon under tension; Prestressed concrete beams comprising a. The method of claim 1,
The tendon duct is a first tendon duct disposed without changing the height in the vertical direction from the bottom of one of the first block to the bottom of the other first block through the second block,
And a second tendon duct having a similar profile in a “U” shape that is gentle from the center or top of one first block to the center or top of the other first block. Prestressed concrete beams. The method of claim 1,
The third block is a prestressed concrete beam, characterized in that the foam styrene or a hollow plastic box inside. In the manufacturing method of the prestressed concrete beam used for the bridge,
A first block provision step of providing a pair of first blocks disposed at both ends and facing each other and having recesses recessed in an end direction;
A second block provision step of providing a plurality of second blocks disposed between the pair of first blocks and recessed downwardly to provide a plurality of second blocks having a cross-sectional shape similar to a '凹';
A tendon duct preparing step of preparing a plurality of tendon ducts connected from the first block of any one pair of the pair to the other one first block;
Disposing a second block between the pair of first blocks;
A first tensioning step of pressing the first blocks and the second blocks in a direction in which the first blocks and the second blocks are close to each other by inserting the tendons into a part of the tendon duct after the placing step is completed and introducing a tensile force;
The lower end portion is inserted into the groove portion of the second block and the upper end portion is exposed to the outside of the groove portion is provided with a third block to provide a lightweight third block for the effect of forming a hollow in the beam inserted into the groove portion of the second block step;
After the installation of the third block is completed, the reinforcing bar is installed and installed in the space except the second block and the third block among the spaces formed by the virtual straight lines connecting the pair of first blocks to each other. A fourth block installation step of pouring; And,
A second tension step of pressing in the direction in which the first blocks and the second blocks are close to each other by inserting the tendon in the remaining tendon duct in which the tendon is not inserted in the first tension step and introducing and pulling tension force; Prestressed concrete beam manufacturing method comprising a. The method of claim 4, wherein
The tendon duct provided in the tendon duct preparation step,
The tendon duct is a first tendon duct disposed without changing the height in the vertical direction from the bottom of one of the first block to the bottom of the other first block through the second block,
A frist characterized by a second tendon duct having a similar profile in a “U” shape that is gentle to extend from the center or top of one first block to the center or top of the other first block. How to make a rest concrete beam. The method of claim 5,
The first tensioning step is performed by inserting tendons in the first tendon duct,
The second tension step is a prestressed concrete beam manufacturing method characterized in that by inserting the tendon in the second tendon duct. The method according to any one of claims 4 to 6,
The third block is inserted into the groove portion of the second block is a pre-stressed concrete beam manufacturing method, characterized in that the foam styrene or a hollow plastic box.

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