JP2000290926A - Prestressed concrete girder using outer cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve bending fracture resistance, and to disperse a crack without increasing quantity of a PC steel material by embedding a PC cable after introducing prestress in additionally placing covering concrete, and integrally sticking the additionally placing covering concrete to girder concrete. SOLUTION: After introducing prestress, a PC cable 2 of part positioned outside a girder concrete cross section between two deviators 5 is embedded in additionally placing covering concrete 6, and this additionally placing concrete 6 is integrally stuck to under floorboard concrete 7. When applying grout in a polyethylene tube for covering a bending-up part of the PC cable 2, an embedded part of the PC cable 2 is also covered with a sheath communicating with the polyethylene tube, and the grout is injected over the total length to be embedded in the additionally placing covering concrete 6. Thus, bending fracture resistance can be improved without increasing quantity of a steel material while keeping lightness, and durability can be improved by double and triple corrosion preventive means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a prestressed concrete girder using an external cable such as a bridge.

[0002]

2. Description of the Related Art Concrete bridges are frequently used as bridges for railways and roads because of their characteristics such as quietness and rust resistance. Especially for long span bridges, prestressed concrete bridges are excellent, and various types of prestressed concrete bridges are employed. However, as the span becomes longer, the cross section of the girder becomes larger, the girder's own weight inevitably increases, and the amount of PC steel increases. Also, structures such as piers become larger, causing problems in seismic resistance and economic efficiency. .

As one of the solutions, a PC cable, which was conventionally housed in a girder concrete section, is disposed outside the concrete section, and the web and floor slab concrete are reduced in thickness to reduce the weight. It is being done.

FIG. 12 is a schematic perspective sectional view of a prestressed concrete girder using an external cable. A supporting and deflecting projection (deviator) 5 is arranged in an inner box-shaped space of a box-shaped concrete girder composed of an upper floor slab 21, a web 22, and a lower floor slab 23, and the PC cable 2 is stretched outside the concrete cross-section of the girder. The structure supports the bridge body via the deviator 5 and introduces prestress. As described above, the PC cable, which has been conventionally arranged in the web or the floor slab, is taken out of the concrete section, whereby the member thickness can be reduced, and the weight of the girder can be reduced. In FIG. 12, 24 is a cross beam, and 4 is a pier.

However, in the prestressed concrete girder 1 using the external cable, the PC cable 2 is arranged outside the concrete section, and the contact point between the bridge and the PC cable 2 is limited to both ends of the girder 1 and the deviator 5. Therefore P
C-cable has low friction with concrete and pre-stress can be effectively introduced. However, since there is no adhesion between PC cable and bridge body, bending fracture resistance is small especially at the part where bending moment is large near the center of the span. However, it has been pointed out that it is necessary to increase the amount of PC steel to compensate for the problem, and that when cracks occur, they are not dispersed but concentrated.

[0006]

DISCLOSURE OF THE INVENTION The present invention has a small cross section, is lightweight, has a bending fracture resistance comparable to that of a conventional prestressed concrete girder with a built-in cable, without increasing the amount of PC steel material, and temporarily generates cracks. The purpose of the present invention is to develop a prestressed concrete girder using an external cable that has a structure that causes harmless dispersion cracking without concentration even if it occurs.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a prestressed concrete girder in which a PC cable is arranged outside the concrete cross section of a girder. A prestressed concrete girder using an external cable, which is buried and the post-coated concrete is adhered to and integrated with the girder concrete.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG.
Is a prestressed concrete girder using an external cable 1
FIG. Girder 1 supported on abutment 3 and pier 4
The PC cable 2 bent down from the tension fixing ends at both ends applies a bending force to the spar through two deviators 5 and introduces prestress into the spar concrete.
The part of the PC cable 2 located outside the girder concrete section between the two deviators 5 is pre-stressed and then buried in the post-cast covering concrete 6 by casting. The post-cast covering concrete 6 is a girder floor slab concrete 7
And integrated.

FIG. 2 is a detailed view of a portion A in FIG. 1. The deviator 5 is provided with a hole 8 through which the PC cable 2 penetrates, and the PC cable 2 continuous from the fixing ends at both ends of the beam is disposed therein. ing. The bent portion of the PC cable 2 is covered with a polyethylene tube 9 for rust prevention. The portion buried in the post-coated concrete 6 between the deviators 5 and 5 is left uncovered and bare to enhance the adhesion performance with the post-coated concrete 6, and the PC cable 2 is embedded in the post-coated concrete 6. When the grout is applied to the inside of the polyethylene pipe 9 of the bent-up portion of the PC cable 2 by using a method for preventing the cable from rusting,
It is preferable to cover the C cable portion with a sheath communicating with the polyethylene pipe 9, inject grout over the entire length, and bury the grout in post-coated concrete to improve the rust prevention effect.

FIG. 3 is a view taken in the direction of arrows BB in FIG. 1 and shows the tension fixing ends at both ends of the box girder. 4 is a cross-sectional view of the deviator section as viewed in the direction of arrows CC in FIG. 1, and FIG. 5 is a cross-sectional view as viewed in the direction of arrows DD in FIG.
The C cable 2 is shown. FIG. 6 is a detailed view of a portion E in FIG. 4, in which the PC cable 2 is inserted into a hole 8 embedded in a deviator 5 projecting from the lower slab concrete 7. FIG. 7 is a detailed view of a portion F of FIG. 5, in which the PC cable 2 is embedded in the post-cast concrete 6, and the post-cast concrete 6 is integrated with the lower slab concrete 7.

FIG. 8 is a side view of a cable system suitable for applying the present invention, and is a side view showing an example of a PC strand aggregated cable. The end of the cable is shown in FIG.
−G As shown in the view of the arrow G, each PC is provided with a wedge 14 divided in a tapered hole formed in the steel anchor head 11.
A type in which the strand 13 is fixed, and a known cable system may be used.

If several portions of the cable system are buried in the post-cast concrete, the expanded portions are provided in several places, so that the concrete wraps around the PC strands and the adhesion between the concrete and the PC strands is further ensured. As shown in FIG. 10 as viewed from the direction of arrows HH in FIG.
Each PC strand 13 is dispersed with the separator 15 interposed. FIG. 11 is a view taken on line II of FIG.
By squeezing the front and rear with the press ring 16, the expanded portion can be easily formed.

In the above embodiment, a simple girder type bridge girder has been described. However, in the case of a continuous girder, the outer cable at a position where positive and negative bending moments are generated is buried in post-coated concrete and adhered to the concrete. It is more effective.

[0014]

The prestressed concrete girder using an external cable in which the PC cable according to the present invention is disposed outside the concrete section of the girder is constructed by embedding the PC cable in post-coated concrete after the introduction of prestress and adhering to the girder concrete. The integrated girder makes it possible to reduce the weight of the girder to the same level as that of conventional external cable concrete girder. In addition, the steel girder requires only the same amount of steel as the conventional concrete girder with a built-in cable, and is economical and has low bending fracture resistance. It has become possible to provide a prestressed concrete girder having a property.
Also, if grout is injected into the sheath of the buried portion that communicates with the polyethylene pipe of the PC cable bending part, it is possible to check the filling state of grout by injecting grout before constructing the coated concrete. And increase the reliability of grouting work,
Sheath and grout and double and triple anticorrosion means improve durability and realize highly reliable prestressed concrete girder. Furthermore, since the bridge body becomes lighter, it is also possible to reduce the foundation costs of the piers and the like, so that an immeasurable effect is exhibited.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a prestressed concrete girder using an outer cable.

FIG. 2 is a detailed view of a portion A in FIG.

FIG. 3 is a view taken in the direction of arrows BB in FIG. 1;

FIG. 4 is a view taken in the direction of arrows CC in FIG. 1;

FIG. 5 is a view as seen in the direction of the arrows D in FIG. 1;

FIG. 6 is a detailed view of a portion E in FIG. 4;

FIG. 7 is a detailed view of a portion F in FIG. 5;

FIG. 8 is a side view of the PC cable system.

FIG. 9 is a view taken in the direction of arrows GG in FIG. 8;

FIG. 10 is a view taken along the line HH of FIG. 8;

FIG. 11 is a view taken along the arrow II in FIG. 8;

FIG. 12 is a perspective sectional view of a prestressed concrete girder using an outer cable.

[Explanation of symbols]

Reference Signs List 1 prestressed concrete girder using external cable 2 PC cable (external cable) 3 abutment 4 pier 5 deviator 6 post-cast covering concrete 7 lower floor concrete 8 hole 9 polyethylene pipe 11 anchor head 12 support plate 13 PC strand 14 wedge 15 separator 16 Holding ring 21 Upper deck 22 Web 23 Lower deck 24 Cross beam

Claims (1)

[Claims] 1. A prestressed concrete girder having a PC cable disposed outside a concrete cross section of a girder, wherein a portion of the PC cable along the concrete surface after the introduction of the prestress is buried in the post-clad covering concrete, Is a prestressed concrete girder using an external cable, which is attached to and integrated with the girder concrete.