KR20150033221A

KR20150033221A - Prestressed Concrete Girder

Info

Publication number: KR20150033221A
Application number: KR20130112936A
Authority: KR
Inventors: 민대홍; 윤용석
Original assignee: 주식회사 다음이앤씨
Priority date: 2013-09-24
Filing date: 2013-09-24
Publication date: 2015-04-01

Abstract

The present invention relates to a prestressed concrete girder and, more specifically, to a prestressed concrete girder which increases the amount of prestress which is possible to be early phased in by a reinforcing portion, and improves workability as well as safety during construction. The present invention comprises: a long main body in one direction which is used as a girder of a bridge as the prestress is phased in, and having an upper flange, a web, and a lower flange which are made of a steel concrete material; multiple tendon ducts arranged inside the main body, and to contain tendon for phasing the prestress; the reinforcing portion made of the steel concrete material, integrally formed with the upper flange, protruding from an upper side of the upper flange for a certain height, and formed long in a longitudinal direction of the upper flange; multiple shear steels arranged along a longitudinal direction of the main body where one part of the center is arranged inside the reinforcing portion and both end portions protrude toward a side of the reinforcing portion and then are bent downward and then inserted into the upper side of the main body; and a longitudinal steel arranged in the longitudinal direction of the main body, and combined with bent parts of the shear steels.

Description

{Prestressed Concrete Girder}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestressed concrete girder, more particularly, to a prestressed concrete girder which not only improves workability but also improves safety during construction, while increasing the amount of prestress that can be introduced by a reinforcement portion .

In bridges containing reinforced concrete girders, it is very commonly used to introduce prestressing into the girder to increase the length of the span. If prestressing is applied to the girder, tensile force is applied to the upper part of the girder in the state where the girder is arranged. Since it is vulnerable to tensile due to the characteristic of the material called concrete, introduction of prestressing is limited. In order to solve the difficulty of introducing sufficient prestress due to such limitations, a multi-stage tension system has been used. The multistage tension system is composed of the steps shown in Figs. 1 (a) to (g). Fig. 1 shows a construction sequence of the double span continuous bridge system of the multistage tension system. As shown in FIG. 1 (a), the girder 100 is first fabricated and tensioned using a fixture 200 (hereinafter, referred to as an end fixture) of the primary tendon on the girder end face as shown in FIG. 1 . The first tensional girder is mounted on a bridge substructure 300 such as an alternate bridge or a pier as shown in Fig. 1 (c), and concrete is poured into the continuous portion of the pier with the slab 400 as shown in Fig. 1 (d). When the slab load is additionally applied to the girder, it is possible to further introduce the prestressing. Therefore, when the continuous portion and the slab concrete reach the predetermined strength, the side fittings 201 of the continuous bridge- Car tension is carried out. When the secondary tension is completed, as shown in FIG. 1 (f), a package, a barrier or a barrier 500 is installed to complete the bridge. Since the side fixture is exposed to the outside in order to be able to work on the tension, it is possible to work on the bridge even after the completion of the bridge as shown in FIG. 1 (g). Therefore, it is possible to use the extra unbonded steel wire preliminarily installed or the extra duct installed preliminarily when the structural performance of the bridge deteriorates after a long period of time, thereby enabling a third tension in the side anchorage. In-situ slabs are mainly used for floor slabs, but precast slabs and precast panels are sometimes used. In this case, precast panels or precast slabs are installed on the girder and the secondary tension is applied before composing it to the girder.

The larger the tensile force introduced into the primary tent, the more advantageous the structure is. The larger the length of the girder in the vertical direction in the arrangement of the tent is advantageous in order to introduce a larger tension force. However, as the length of the girder becomes longer, the girder becomes larger and the weight of the girder becomes larger. Therefore, the advantages of the tensile force introduced are eliminated. On the other hand, when excessive initial tension is applied, cracks may occur on the upper surface of the girder, and this is also an important parameter for defining the limit of the tension.

In the case of a prestressed concrete girder, the magnitude of the tension should be controlled only by the profile of the steel wire. In the conventional case, there is a problem that the magnitude of the tension is limited.

Korean Patent No. 10-1012402 (entitled "Prestressed Concrete Girders ") has been proposed by one of the inventors of the present invention to solve these problems. And a hoop-like stud is disposed on the upper surface of the protruding portion.

However, if such a configuration is taken, there is a problem that the stud makes the walking of the worker inconvenient, which not only deteriorates the workability but also causes a safety accident of the worker.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the background arts, and it is an object of the present invention to provide a prestressed concrete girder which can increase the amount of initial prestress that can be applied, while improving safety and workability.

As a means for solving the above-mentioned problems,

Prestresses are introduced and used as girders in bridges,

It consists of upper flange, abdomen and lower flange made of reinforced concrete material and has a long unidirectional body;

A plurality of tendon ducts provided inside the main body and adapted to receive a tendon for introducing the prestress;

A reinforcing portion of a reinforced concrete material protruding at a predetermined height from an upper surface of the upper flange and extending in the longitudinal direction of the upper flange and integrally formed with the upper flange;

And a plurality of shear reinforcing bars disposed along the longitudinal direction of the main body, the reinforcing bars being inserted into the upper surface of the main body. And

And a longitudinal reinforcing bar disposed in the longitudinal direction of the main body and coupled to the bent portion of the front reinforcing bar.

Preferably, the portion of the shear reinforcement inserted into the upper surface of the main body is connected to the reinforcing bars disposed inside the main body.

According to the present invention, it is possible to provide a prestressed concrete girder which is structurally reinforced by the projections to improve the workability while increasing the amount of prestress that can be introduced in the early stage, securing the safety of the operator, and facilitating construction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view for explaining a method of constructing a prestressed concrete girder bridge. FIG.
2 is a perspective view of a prestressed concrete girder according to one embodiment of the present invention;
3 is a sectional view of the prestressed concrete girder shown in Fig.
Fig. 4 is a sectional view for explaining the arrangement of the shear reinforcement and the longitudinal reinforcement shown in Fig. 2. Fig.
5 is a sectional view of a slab constructed using the prestressed concrete girder shown in Fig.
Figs. 6 and 7 are diagrams for explaining construction of the main steel bars of the slab by using the front-end reinforcing bars shown in Fig. 2 as spacers. Fig.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, and specific details for carrying out the present invention will be provided.

FIG. 2 is a perspective view of a prestressed concrete girder according to an embodiment of the present invention, FIG. 3 is a sectional view of the prestressed concrete girder shown in FIG. 2, Fig. 5 is a cross-sectional view of a slab constructed using the prestressed concrete girder shown in Fig. 2, and Figs. 6 and 7 are cross-sectional views showing a slab, Fig.

A prestressed concrete girder according to an embodiment of the present invention is composed of a main body 10, a tent duct 20, a reinforcing portion 30, a shear reinforcing bar 40 and a longitudinal reinforcing bar 50.

The main body 10 is made of a reinforced concrete material and is composed of an upper flange 11, a lower portion 12 and a lower flange 13 as shown in FIG. Although not shown in FIG. 2, both end portions of the main body 10 may be provided with a side surface section (a hatched portion) for prestressing. Inside the main body 10, reinforcing bars are embedded by design. The first reinforcing bars 15 and the second reinforcing bars 16 are provided in FIG. 4, and additional reinforcing bars may be provided although not shown.

The tendon duct 20 receives a tendon as a through-hole provided in the longitudinal direction of the main body 10, as shown in Fig. The tension duct 20 shown in FIG. 3 is not shown to be precisely proportioned to show more clearly, and the position, number, and placement profile of the tension duct 20 may vary as desired depending on the design. When prestressing is applied after the tendon is accommodated in the tent duct 20, both ends of the tent are fixed using a fixing device so that the applied prestress is held in the main body 10. [

2, the reinforcing portion 30 is formed on the upper surface of the upper flange 11 of the main body 10 so as to protrude at a predetermined height in the height direction of the main body. The reinforcing portion 30 is integrally formed with the upper flange 11 Of reinforced concrete material. The reinforcing portion 30 is provided so as to coincide with the longitudinal center of the reinforcing portion 30 and the longitudinal center of the main body 10 and that the reinforcing portion 30 is provided symmetrically with respect to the center of the main body 10 ) May be about 1/16 to 3/4 of the length of the main body 10. The length of the reinforcing portion 30 can be appropriately determined according to the amount of the prestress to be introduced.

When the height of the reinforcing portion 30 is less than 5 cm, the desired effect of the present invention is not expected. When the height of the reinforcing portion 30 is more than 20 cm, the problem of the synthesis with the slab concrete .

As shown in FIG. 2, both end portions of the reinforcing portion 30 are tapered so as to become thicker from the end to the center, and the taper angle is about 10 to 80 degrees. The reason for tapering both ends of the reinforcing portion 30 is that the stress concentration may occur when the reinforcing portion 30 assumes the shape of a rectangular parallelepiped, so that the stress is naturally dispersed, and when the slab concrete is poured, .

2 and 4, the central portion of the shear reinforcement 40 is disposed inside the reinforcing portion 30, both ends of the shear reinforcement 40 are exposed to the outside of the reinforcing portion 30, And the end portion inserted into the upper surface of the main body is connected to the reinforcing bars (first reinforcing bars 15 in this embodiment) laid inside the main body 10 as shown in Fig.

It is preferable that the front shear reinforcing bars 40 are provided at a plurality of spaced intervals along the longitudinal direction of the main body 10.

The longitudinal reinforcing bars 50 are disposed in the longitudinal direction of the main body 10 and are coupled to the bent portions of the front reinforcing bars 40 as shown in FIG.

Hereinafter, functions, actions, and effects of the respective structures will be described.

Since the main body 10 and the tent duct 20 are the same as those of a generally used prestressed girder, a detailed description thereof will be omitted. The reinforced portion 30, the front-end reinforcing bars 40, (50) will be mainly described.

The reinforcing portion 30 enhances the cross section of the central portion of the main body 10 in the slab direction of the bridge, thereby enabling the introduction of a larger prestress. So far, the size of the prestress applied to the girder has been determined by the profile of the steel wire. In the case where prestressing is applied by the tenter, tensile force is applied to the upper flange 11 at the center portion of the girder, where the maximum moment acts. However, there is a limit to the characteristics of the concrete material which is weak in tensile force. In order to introduce greater stress, the cross section must be enlarged. Until now, it has been thought that the entire section should be enlarged. When the whole cross section is enlarged, the self weight is increased, so even if the size of the introduced prestress is increased, the effect is canceled by the increasing weight. The introduction of a larger prestress could increase the length of the span, which could not be expected. However, in the case of the present invention, by providing the reinforcing portion 30 on the upper flange 11 of the girder, it is possible to introduce a larger prestress by enlarging the cross section only in a part of the girder. Therefore, a prestressed girder with a longer diameter can be manufactured.

The reinforced portion 30 protruded upward is combined with the slab concrete as shown in FIG. 5, so that it is possible to construct the reinforced portion 30 without knowing that the reinforced portion 30 exists after the completion of the construction of the bridge.

The portion of the shear reinforcing bars 40 embedded in the reinforcing portion 30 serves to reinforce the reinforcing portion 30 and the portion exposed to the outside of the reinforcing portion 30 serves to reinforce the reinforcing portion 30 reinforcing the slab concrete 63. [ And also has a shape of "a" shape so as to serve as a stud when synthesizing the slab concrete 63 with the slab concrete 63. In addition, the reinforcement member 50 also serves as a reinforcing bar for restraining the longitudinal reinforcement 50.

In the present invention, since the shear reinforcement 40 plays the role of a stud, the workability is remarkably improved and the safety of the worker is secured, compared with a case where the stud is formed on the upper surface of the reinforcement. In the case where a stud is provided on the upper surface of the reinforcement portion, a safety accident such as a walker's difficulty in walking due to the operator stepping on the reinforcing portion while walking on the reinforcement portion or falling on the stud may occur. In the present invention, It is possible to expect the effect of the problem solved.

The longitudinal reinforcing bars 50 serve not only to reinforce the slab concrete 63 but also to serve as spacers for installing the underground steel rods 61 used for the slabs. The spacing material is used to maintain the distance between the top surface of the main body 10 and the bottom steel main pole 61 before the concrete is poured, and must be installed on all reinforcing bars and must be directly installed by a worker. It is very troublesome to work with a lot of hands. However, since the longitudinal reinforcing bars 50 do not use the spacers of the cast iron rods 61, the workability can be expected to be improved.

Examples of the connection between the longitudinal reinforcement 50 and the bottom reinforcement 61 are shown in Figs. 6 and 7. Fig. FIG. 6 shows a state in which a connecting member 611 (generally a thin wire is used) used for connecting reinforcing bars, and FIG. 7 shows a state where a ring 612 is provided at the end of the lower casting muscle 61, And the ring is connected to the longitudinal reinforcing bars 50 to connect the reinforcing bars 61 and the longitudinal reinforcing bars 60 to each other.

Hereinafter, a state in which the slab is installed using the prestressed concrete girder described above with reference to FIG. 5 will be described.

In the state where the above-described prestressed girder is disposed, the lower side cast iron rope 61 is connected to the longitudinal reinforcing bar 50, the additional reinforcing rope is installed in the state that the upper side cast iron rope 62 is installed, and the slab concrete 63 is poured And cures to form the slab.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments, May be embodied as various types of prestressed concrete girders.

10: Body 20: Tendon duct
30: reinforcement portion 40: shear reinforcement
50: longitudinal reinforcement

Claims

Prestresses are introduced and used as girders in bridges,
It consists of upper flange, abdomen and lower flange made of reinforced concrete material and has a long unidirectional body;
A plurality of tendon ducts provided inside the main body and adapted to receive a tendon for introducing the prestress;
A reinforcing portion of a reinforced concrete material protruding at a predetermined height from an upper surface of the upper flange and extending in the longitudinal direction of the upper flange and integrally formed with the upper flange;
And a plurality of shear reinforcing bars disposed along the longitudinal direction of the main body, the reinforcing bars being inserted into the upper surface of the main body. And
And a longitudinal reinforcing bar disposed in the longitudinal direction of the main body and coupled to the bent portion of the front reinforcing bar.

The method according to claim 1,
Wherein a portion of the shear reinforcing bars inserted into the upper surface of the main body is connected to reinforcing bars disposed inside the main body.