JPS5853286Y2 - Composite girder with PC precast concrete blocks in the tension section - Google Patents

Description

[Detailed description of the invention] This invention relates to a composite girder having PC precast concrete blocks in the tension section.

Composite girders that combine steel girders and concrete and use both as stress-resistant materials are widely known, but most of them use concrete on the compressive stress side.
The steel girder is exposed as is on the tensile stress side.
As a result, noise problems due to local vibrations of the steel plate when the vehicle is running, or the complexity of maintenance such as painting, have become problems.

These problems can be solved by completely covering the steel girder with concrete, but since concrete is strong in compression but weak in tension, it is difficult to directly pour concrete into areas with high tensile stress. Even if the concrete is installed, the tensile stress will cause the concrete to crack and fail, and the problem will not be solved.

That is, in order to use concrete on the side of large tensile stress, it is essential to introduce compressive stress commensurate with the tensile stress into the concrete in advance.

A composite girder made of steel and concrete is already known, in which concrete is used on the tensile stress side, prestress compressive stress is applied to this concrete, and the steel girder is finally completely covered with concrete (Japanese Patent Publication No. 1973- 10424
issue).

The method of applying prestress to the concrete in this composite girder is to pre-deflect the steel girder due to the load, and in this state, concrete members are placed on the tensile stress side of the steel girder on a table or on a concrete hardening plate. By removing the front deflection load applied to the rear steel girder, the restoring force of the girder is utilized to introduce compressive stress into the concrete member on the tension side (Japanese Patent Publication No. 31563/1983).

In this girder, the concrete on the tension side becomes the stress-resisting cross section, so the girder height can be lowered compared to a normal composite girder that uses concrete only on the compression side, and it is suitable for bridges with girder height restrictions. Very advantageous.

However, this method has the problem that the work of applying a forward deflection load to the steel girder is complicated.

In consideration of this point, a composite girder was proposed in which a prestressed concrete block, to which prestress stress has been applied in advance, is fixed to the tensile stress side of the steel girder using adhesive or fixing means such as bolts and nuts (in practice). Publication No. 52-5856).

However, in this type of composite girder, when the concrete blocks and steel girder flanges are bonded using adhesive, there is a problem that the adhesive is extremely weak against impact force, and the bond is not connected using bolts and nuts. When this is done, creep occurs in the concrete due to concrete compressive stress generated as a reaction force to the axial force introduced into the bolt.
This has the problem of reducing the axial force introduced into the bolt.

In view of the above-mentioned circumstances, the composite girder according to the present proposal is intended to eliminate the drawbacks of the composite girder with concrete on the tension side as described above, and to provide a more specific composite girder that can expand the range of application. Basically, a prestressed concrete block is attached to the flange on the tensile stress side of the steel girder, but the connection between the block and the steel girder flange prevents undue compressive stress from being applied to the concrete block by tightening the bolts. It is characterized in that it can be obtained in a non-active state.

Next, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows a partial perspective view of a steel girder used in the composite girder of the present invention, and FIG. 2 shows a perspective view of a concrete block.

The steel girder 1 has bolt holes 3 at predetermined intervals in the flange 2 on the tension side, and dowels 5 on the flange 4 on the compression side.
, the web 6 is manufactured in advance in a factory so that reinforcing steel bars 7 are provided thereon.

On the other hand, the precast concrete block 8 has a sheath 9 and auxiliary reinforcing bars 10 for inserting PC steel rods (hereinafter referred to as steel rods including steel wires) inside, which are also pre-produced in a factory, and the steel girder 1 and the steel girder 1 on the surface. Processed steel plate 1 for the purpose of joining
・It is formatted so that 1 is provided.

As shown in FIGS. 3 and 4, the processed steel plate 11 has a dowel 12 protruding from its back surface to improve adhesion to the concrete block 8, and a dowel 12 for bonding to the steel girder 1. A bolt hole 13 is opened.

Furthermore, prior to forming the block 8 having the processed steel plate 11, a bolt 14 having threads at both ends is inserted into the bolt hole 13 of the processed steel plate 11 as shown in FIG. Concrete is cast with the bolts 14 screwed onto both ends of the bolts 14 so as to be located on both the inner and outer surfaces of the processed steel plate 11, and the nuts 15 on the back side of the processed steel plate 11 are screwed together.
be firmly fixed in concrete.

Needless to say, a cap nut is used for this nut 15 to prevent it from penetrating into the internal threads of the concrete.
It goes without saying that 3 is arranged at the same position as the bolt hole 3 of the tensile stress side flange 2 in the steel girder 1.

In the figure, 17 indicates a washer.

The steel girder 1 and the precast concrete block 8 are joined together in a factory or at an erection site in the following manner.

First, either simply support the steel girder 1 in the yard as shown in Figure 6, or
Alternatively, the bridge is constructed using a support system in a completed state, and several sets of precast concrete blocks 8 are arranged in series on the tensile stress side flange 2 of this steel girder.

Prior to placement, all the bolts 14 of the processed steel plate 11 in the block 8 are removed, and the bolt holes 1 of the processed steel plate 11 are removed.
3 and the flange bolt hole 3 of the steel girder 1 are in communication,
The bolt 14 is inserted through the steel girder flange bolt hole 3 into the cap nut 15 in the block processed steel plate bolt hole 13 and screwed into the cap nut 15 to temporarily fix the steel girder 1 and the block 8.

At that time, it is desirable to interpose a steel spacer 18 in order to adjust the gap between the steel girder flange 2 and the block processed steel plate 11.

After a plurality of sets of concrete blocks 8 are temporarily assembled and arranged on the steel girder 1 in this way, a PC steel rod 19 is inserted into the sheath 9 of each block 8, and a concrete-based steel rod is inserted into the joint surface of each block 8. Then, as shown in FIG. 7, the gap between the steel girder 1 and the block 8 is filled with a filler 21 such as high-strength cement material or epoxy mortar.

After curing of the adhesive 20 and filler 21, pcfA rod 19
to introduce compressive prestress stress into several sets of precast concrete blocks 8.

The remaining concrete blocks 8 are sequentially attached to the flanges 2 of the steel girder 1 in the same manner as described above, and finally a large number of concrete blocks 8 to which prestress stress has been introduced are attached to the steel girder 1 over a predetermined length. state.

After that, by tightening the nuts 16 exposed on the steel girder flange 2, a predetermined tensile axial force is introduced into the bolts 14, and by grouting the inside of the sheath 9, the connection between the steel girder and the PC precast concrete block is completed. do.

As shown in FIG. 7, wave concrete 22 and slab concrete 23 are placed on the steel girder 1 on which the precast concrete blocks 8 have been joined at the construction site, and the concrete 23 on the compression side is also placed on the dowel 5.
By doing this, it is combined with the steel girder 1, and a composite girder in which the steel girder 1 is completely covered with concrete is completed.

FIG. 8 is an example in which two composite girders according to the present invention are applied to a composite box girder, and shows a cross section near the intermediate support of the continuous girder.

In this example, since the lower concrete precast member 24 is in compression, there is no need to introduce prestress using the PC steel rod, and the connection between the steel girder 1 and the precast member 24 is performed in the same manner as in the previous example. .

Since the upper (slab) concrete precast member 25 is on the tension side, prestress is introduced using the PC steel rod 19, and then it is combined with the steel girder 1 in the same manner as in the above example.

The wave concrete section 26 is constructed for the purpose of covering the steel girder, and reinforcing reinforcing bars are inserted in the tension side section to prevent the concrete from peeling off.

The composite girder according to the present invention has the structure as described above, and a processed steel plate 11 is provided on the surface of the precast concrete block 8, and the processed steel plate 11 and the tensile stress side flange 2 of the steel girder 1 are connected by bolts 14. Therefore, the horizontal shear force acting from the steel girder 1 to the precast concrete block 8 is 15,1 (bolts 14, oak)
6. The friction force of the friction bonding member consisting of the washer 17 and the spacer 18 is transmitted to the processed steel plate 11, and is further transmitted to the prestressed concrete block 8 via the dowel 12.
transmitted to.

In addition, the connection between the steel girder 1 and the precast concrete block 8 is basically friction bonding by metal touch between the steel girder flange 2 and the processed steel plate 11, and it is directly connected to the concrete like the conventional composite girder of this type. Since compressive stress based on bolt axial force can be prevented from acting, phenomena such as a decrease in bolt axial force when joining concrete and steel can be eliminated, and a rational composite structure of steel and concrete can be created. Obtainable.

Furthermore, when bolts 14 having threads at both ends are provided in the bolt holes 13 of the processed steel plate 11 in the concrete block 8, the bolts 14 are completely inserted into the block 8.
Since the blocks 8 can be made to touch the steel girder 1 with the blocks 8 removed from the steel girder 1, as shown in FIG. Even after reaching the given state, several sets of blocks 8 can be touch-connected to the rest of the steel girder 1 in the same manner with the bolts 14 removed, and an improvement in work efficiency can be expected.

Furthermore, since prestress is applied by the PC steel bars 19 after the precast concrete block 8 is attached to the steel girder 1, the tensile stress acting on the block 8 can be reduced by adjusting the number of PC steel bars 19. This has the advantage of being economical as it allows the introduction of prestress stress depending on the size, and has the practical benefit of increasing the practicality of this type of composite girder.

[Brief explanation of drawings]

Figure 1 is a partial perspective view of the steel girder used in the composite girder according to this proposal, Figure 2 is a perspective view showing the structure of a precast concrete block, and Figure 3 is a perspective view of a processed steel plate fixed to the surface of the concrete block. Figure 4 is a side view, Figure 5 is a sectional view taken along the ■-V line in Figure 4, Figure 6 is a side view showing the connection relationship between the steel girder and the concrete block, and Figure 7 is the 6 FIG. 8 is an enlarged cross-sectional view taken along the line Vll-Vll in the figure, and FIG. 8 is a cross-sectional view showing an application example of the composite girder according to the present invention. In the figure, 1... Steel girder, 2, 4...
Flange, 3.13... Bolt hole, 5,12.
...Jibel, 6...Web, 7,10.
...Reinforcement reinforcing bar, 8...Precast concrete block, 9...Sheath, 11...
...Processed steel plate, 14...Bolt, 15゜16
...Natsuto, 17...Washer, 18
...Spacer, 19...PC steel bar,
20... Adhesive, 21... Filler, 2
2.26...Wave concrete, 23...
...Floor slab concrete, 24.25...Precast concrete members.

Claims (1)

[Scope of utility model registration request] 1. A tensile stress side flange 2 of a steel girder 1 formed by type steel such as I type steel or H type steel or welding has a PC steel bar sheath 9 inside, and a processed steel plate 11 for transmitting horizontal shear force on the surface. A plurality of precast concrete blocks 8 provided through dowels 12 are attached by connecting the flange 2 and processed steel plate 11 through bolts 14, and each block 8 is inserted into the sheath 9. Composite girder with PC precast concrete blocks in the tensile section, which are adapted to be prestressed by compressive prestressed PC steel rods 19. 2. A practical method in which the flange 2 and the processed steel plate 11 in the block 8 are connected by a bolt 14 having threads at both ends that is screwed into a nut 15 embedded inside the bolt hole of the processed steel plate 11. A composite girder having a precast concrete block made of precast concrete in the tensile part as claimed in claim 1.