JPH023844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing prestressed concrete slabs for road bridges and the like.

In recent years, road maintenance has become even more difficult as the volume of traffic has increased and the speed and weight of vehicles have increased, and even the slightest weak point in a road can cause damage. In particular, in so-called steel bridges in which reinforced concrete deck slabs are constructed on steel girders, the reinforced concrete deck slabs are frequently damaged, and countermeasures for this problem include increasing the slab thickness and increasing the stiffness of the main girder. The Ministry of Construction has issued new guidance regarding consideration of bending moments, appropriate reinforcement methods, etc.

By the way, the conventional construction method for constructing this type of concrete slab is to construct shoring, formwork, etc. on the main girder, then place reinforcement on the bottom and top surfaces, and then pour concrete. The main method of construction was to remove the cast concrete from the mold after it had hardened. In this construction method, all of the concrete is poured on-site, so there are no joints formed in the slab itself, and the overall construction cost is low. Since it is a printed version, it is susceptible to damage for the reasons mentioned above.

On the other hand, as another construction method, pre-cast deck slabs manufactured in advance at a factory etc. are used to create an RC structure in the direction of the main reinforcement, that is, in the width direction, and prestress for vertical tightening is introduced in the direction of the distribution reinforcement, that is, in the direction of the bridge axis. In some cases, a method of pouring concrete joints and integrating them with the main girder is also being implemented. This construction method has the advantage of increasing the strength and durability of the reinforced concrete deck slab itself to some extent by introducing prestress in the bridge axis direction, but it has the following drawbacks. In other words, in order to introduce vertical tightening prestress in the direction of the bridge axis of the deck, it is necessary to proceed with the work discontinuously at certain intervals in the direction of the bridge axis. Furthermore, since precast slabs are quite heavy, transporting them from the place of manufacture (factory, etc.) to the erection site is costly, and it is difficult to erect at high places. Construction costs were high, and since the concrete joints were used as joints between the slabs, there were disadvantages such as the possibility of forming discontinuous areas in terms of strength.

The present invention has been made in consideration of the above points, and it is possible to continuously introduce prestress to the deck slab substantially in both the bridge axis direction and the width direction, thereby improving strength and durability. We have developed a construction method for prestressed concrete deck slabs for road bridges, etc., which can form excellent deck slabs, has no discontinuous parts in terms of strength, has low overall construction costs, and is easy to construct on-site. The purpose is to provide.

The present invention will be described below based on an embodiment shown in the drawings.

As shown in Fig. 1, the construction method according to the present invention involves assembling a reinforcing bar mesh consisting of main bars 2 and distribution bars 2' above and below a support beam 1 having holes 1a in advance in a factory or the like, and suspending it from the support beam 1. So-called semi-prefabricated floor slabs 5 are manufactured by attaching formwork 4 made of plates through materials 3, and these are transported to the site and erected by arranging them sequentially on main girders 6, 6 as shown in the figure. do. In addition, semi-prefabricated floor slab 5
As the formwork 4, as shown in Fig. 2, the main girder 6
Large-diameter holes 8 are provided in portions corresponding to the dowels 7 erected on the upper flange 6a of the semi-prefabricated deck 5. By fitting these holes 8 into the dowels 7, these The dowels 7 are constructed so as to face the upper surface of the formwork 4 through the holes 8, respectively. Although not particularly shown, wrap allowances are provided in the formwork 4 of the semi-prefabricated floor slabs 5, and consideration is given so that these lap allowances overlap each other when the semi-prefabricated floor slabs 5 are erected side by side. has been done.

In this way, after the semi-prefabricated deck slabs 5 are sequentially arranged and erected on the main girders 6, 6, before pouring concrete onto these semi-prefabricated deck slabs 5, only the bottom surface is open as shown in Fig. 2. A hollow cutting die 9 is placed over each dowel 7 and set on the formwork 4, thereby sealing the surface of each dowel 7 and the upper flange 6a exposed through the hole 8 to prevent concrete from adhering to it. I'll keep it.
Furthermore, the necessary number of PC steel members 1 to introduce prestress into the concrete to be poured.
0 are inserted obliquely in the width direction between the upper and lower ribs of the semi-prefabricated floor slab so as to intersect in an X-shape when viewed from above as shown in FIGS. 3 and 4. Here, it is preferable that the inner diameter of the hollow part of the cutting die 9 is larger than the diameter of the hole 8, and that the outer diameter of the die 9 is gradually smaller toward the bottom so that it can be easily demolded later. . In addition, the inclination angle θ of the prestressing steel material 10 with respect to the width direction is usually around 30°, but if necessary
It may be around 45°. However, in any case, 1
As shown in FIG. 3, the PC steel material 10 must be diagonally arranged so as to penetrate at least two adjacent semi-prefabricated floor slabs. The prestressed steel material 10 is a so-called unbonded material made by applying a lubricant such as grease around a prestressed steel wire and covering it with a plastic sheath so that it can be tensed in poured concrete. Either wire or PC wire may be used. In addition, when using PC wire,
Set the sheath pipe inside the semi-prefabricated floor slab in advance,
Insert the PC wire through this.

After the cutting die 9 and the prestressing steel material 10 have been set in this way, concrete 11 is poured and cured for a predetermined period of time, and after the concrete hardens, both ends of the prestressing steel material 10 are sequentially tensed to introduce prestress. do. When this prestress introduction work is performed, compressive force acts on the hardened concrete 11 in both the width direction and the bridge axis direction. That is, as shown in FIG. 3, since the PC steel materials 10 are arranged diagonally in the width direction so as to intersect in an X shape when viewed from above, the compressive force due to the PC steel materials 10 is absorbed by the PC steel materials 10. A component force corresponding to the inclination angle θ acts as a compressive force in the bridge axis direction.

By the way, this compressive force in both directions naturally acts on each semi-prefabricated deck slab 5 that is integrated with the hardened concrete 11, and as a result, each semi-prefabricated deck slab 5 is compressed along with the concrete 11 in the bridge axis direction and width. Main girder 6 in both directions or in one direction,
6 will be subjected to a force that will cause it to move slightly. Here, the dowel 7 facing onto the formwork 4 is prevented from being integrated with the concrete 11 by the cutting die 8, and the hole 8 provided in the formwork 4 has a diameter sufficiently larger than that of the dowel 7. As a result, each unit slab 5 is movable in any direction, and as a result, the prestress can be introduced without any problem.
In addition, when performing this prestress introduction work, since all of the ends of the prestressing steel material 10 except for the first part are located at both ends in the width direction, it is easy to perform the prestress introduction work on site, and even the concrete 11 hardens. If you do so, you can continue working on it.

After introducing prestress as described above, the cutting die 9 is removed and concrete is filled in this area to form a prestressed concrete slab A as shown in FIG. 3. The deck A formed in this way is given a certain degree of compressive stress (prestress) in both the bridge axis direction and the width direction, and as a result, it has excellent strength and durability. The floor slab is constructed. In addition,
The deck slab A is integrated with the main girders 6, 6 through post-cast concrete around the dowel.

In addition, in the embodiment, an example was shown in which the formwork 4 was formed of an integral plate and holes 8 were provided in the portions located above the main girders 6, 6 to eliminate interference with the dowels 7, but for example, When the formwork 4' is formed of divided plates as shown in FIG. 5, and they are spaced apart from each other within a range that is sufficient to rest on the upper flange 6a as shown in the figure, the width is equal to the space between them. It is also possible to use a disposable mold frame 12 made of a band-shaped rubber plate or the like having a hole 8' which is large and has holes 8' to prevent interference with the dowel 7, and to set the cutting die 9 thereon.

In addition, in the example, an example was shown in which two PC steel materials 10 were passed through one hole 1a provided in the support beam 1, but as shown in FIG. 6, for example, the number of holes 1a could be increased. One wire may be passed through each hole 1a.

As described in detail above, the present invention is a semi-prefabricated floor slab made by assembling necessary reinforcing bars such as main bars and distribution bars on a main girder provided with a plurality of dowels extending upward, and attaching formwork underneath. A hole with a diameter larger than the dowel formed in the formwork is inserted into the dowel to construct a plurality of them side by side, and then, before pouring concrete into these semi-prefabricated slabs, hollow and By covering the hole and the dowel with a cutting die that can be removed upward from inside the poured concrete, the dowel and the top surface of the main girder are sealed so that the poured concrete does not adhere to them, and the required number of PC steel pieces are are arranged across at least two adjacent semi-prefabricated slabs diagonally in the width direction and intersect in an X-shape when viewed from above, and in a tensionable state in the poured concrete after hardening. After the concrete hardens, the PC steel materials are sequentially tensed to introduce prestress to form the deck slab, so that the deck is substantially continuously prestressed in both the axial and width directions of the bridge. Introducing the strength,
It is possible to form a floor slab with excellent durability, and since the concrete is cast on-site, there are no discontinuities in strength due to joints, and the overall construction cost is also low. Since the construction method involves erecting semi-prefabricated floor slabs that have been manufactured in advance at a factory, there is less reinforcement work on site, and prestressing can be easily introduced, making construction easier on site. It has various excellent effects.

[Brief explanation of drawings]

The figures are shown to explain embodiments of the present invention. Figure 1 is a schematic sectional view of a semi-prefabricated deck constructed on the main girder, and Figure 2 is a section where the formwork is located on the main girder. , FIG. 3 is a schematic plan view of the erected floor slab, FIG. 4 is an enlarged view of the part shown in FIG. 1 (excluding support beams), and FIGS. FIG. 2 is a perspective view similar to FIG. 2 showing another embodiment; 1... Support beam, 2... Main reinforcement, 2'... Distribution reinforcement,
4,4'...Formwork, 5...Semi-prefabricated floor slab, 6
...Main girder, 7...Dovetail, 8, 8'...Hole, 9...
...Cutting die, 10...PC steel material, 11...Concrete, 12...Disposable formwork.

Claims (1)

[Claims] 1. On the main girder with multiple dowels extending upward,
Semi-prefabricated floor slabs are made by assembling the necessary reinforcing bars such as main bars and distribution bars, and installing formwork underneath.
By fitting a hole with a larger diameter than the dowel formed in the formwork into the dowel, a plurality of holes are installed side by side,
Next, before pouring concrete into these semi-prefabricated deck slabs, a hollow cutting die with only the lower surface open and capable of being removed upwards from within the poured concrete is placed over the hole and the dowel to form the dowel and the main girder. Seal the top surface of the poured concrete to prevent it from adhering to it, and also
PC steel materials are arranged across at least two adjacent semi-prefabricated slabs diagonally in the width direction and intersect in an X-shape when viewed from above, and in a state where they can be tensioned in the poured concrete after hardening, A method for constructing prestressed concrete slabs for road bridges, etc., characterized by introducing prestress by sequentially tensioning the prestressed steel materials after the poured concrete has hardened.