JP2831934B2 - How to build substructure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a so-called substructure such as a pier,
The present invention relates to a construction method for constructing a pier or the like in a prestressed reinforced concrete (PRC) structure using a precast concrete block (hereinafter, referred to as a precast block). This technology can be suitably used for construction of a pier or the like having a height of about 30 to 50 m.

[0002]

2. Description of the Related Art FIGS. 14 and 15 show an example of a concrete bridge 100 to which the present invention is applied. A pier 10 rising from a footing 102 constructed on a foundation pile 101 or the like.
The bridge body 104 (upper structure) is supported on the upper part of the so-called lower structure composed of 3. FIG. 15 is a sectional view of the lower structure (a sectional view taken along the line AA in FIG. 14).

Conventionally, in the case of constructing a structure such as a pier, etc., in the case of an RC (reinforced concrete) structure by a cast-in-place concrete method, generally, a full formwork method in which all formworks are attached and constructed or a sliding formwork is used. It was constructed by a sliding method of construction. Construction methods of RC structures using precast blocks and construction methods of PC (prestressed concrete) structures are also known. Compared with cast-in-place concrete methods, high-quality blocks that do not require formwork on site are required. There are advantages that can be used.

In the RC structure using a precast block, reinforcing bars having a length substantially equal to the block length are embedded in each precast block, and the reinforcing bars are sequentially stacked while being connected to each precast block. Therefore, there are problems that the number of joints is large, complicated, and the construction period becomes long. In addition, since there is a joint on the joint surface of the precast block, it is necessary to provide reinforcement for shearing of the joint and to provide a shear key or the like. In order to shorten the construction period, the technique of stacking blocks in multiple stages and inserting and connecting through-the-bar reinforcing bars in multiple stages is also described in, for example, "Civil Engineering Construction" Vol. 8, No. 8, pp. 25-32, "Tohoku Main Line No. 8 Mabuchigawa Bridge Ryo" Construction of RC Precast Block Type Bridge Pier in Construction ", but because it is still RC structure, it requires many reinforcing bars and is not a fundamental measure.

On the other hand, using a precast block
(Prestressed concrete) There is also a technology for constructing bridge piers and the like, but in this case, full prestress acts on the mutual joining surfaces of the precast blocks, and if the joining surfaces of the precast blocks have irregularities, large local There is a problem that stress is generated and vertical cracks and the like occur. Therefore, the joining surface of the precast block is required to have a high flatness accuracy. For example, the precast block must be mirror-finished or manufactured by match casting.

A construction example in which PC strands fixed to a footing are arranged in a J shape using a precast block is described in "PCI Journal: September 1985". Also, "W. Poldonie, J.M. By Mueller: PC
Bridge Design and Construction: Translated by Kyushu Bridge Engineering Society, 1992.
2.20 issuance ”, the precast pier includes a pile, a pile cap, an upper part of the skeleton and a pier cap as precast segments. The lower part of the skeleton and the upper part of the footing are cast in place.
An example is described in which the device is inserted into a character-shaped place-in-place footing. These are all PC structures.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the case of constructing a pier or the like using a precast block, and provides a construction method capable of constructing a structure in a short construction period. is there. That is, an object of the present invention is to provide a novel construction method of a prestressed reinforced concrete (PRC) structure using a precast block.

The objects of the present invention are as follows. (A) Eliminate the trouble of providing a reinforcing joint in the precast block in advance when manufacturing the precast block. (B) Reducing the number of rebar joints as much as possible. (C) Prevent the rebar joint from concentrating on the joint surface of the precast block.

(D) It is not necessary to improve the production accuracy (mirror finish or the like) of the joint surface of the precast block. (E) Eliminates the problem of shear at the joint surface in design. (F) Reduce the total amount of steel materials, and increase the economy and workability.

[0010]

The present invention is characterized by taking the following technical means in order to solve the above problems. That is, the present invention embeds a U-shaped sheath tube in the footing, stacks a precast block having a main reinforcing bar insertion hole and a PC steel wire insertion hole on the footing,
The main rebar is inserted from above through the main rebar insertion holes of the stacked blocks, and the PC stranded wire insertion hole and the U
After penetrating the PC steel stranded wire from above through the shape and tube, and tensioning the PC steel stranded wire at the upper end of the uppermost block to introduce a slight longitudinal prestress into the stacked blocks, A method for constructing a substructure, comprising: injecting grout into an insertion hole and a PC steel wire insertion hole and attaching the grout to a block to form a PRC structure.

In the above method, it is preferable that a long reinforcing bar is used as the through reinforcing bar, and that joints are provided at different heights to disperse weak points of the reinforcing bar, thereby enhancing safety against an earthquake load. is there. In the present invention,
"Mild" pre-stress refers to a level of pre-stress introduced into concrete at a lower level than normal full stress.

For example, the prestress introduction amount is set to 10 to 15
kgf / cm ² .

[0013]

According to the present invention, the following effects are produced by the above configuration. (A) The structure according to the present invention has a PRC structure. The mechanical structure of this structure is mainly reinforced by rebar,
The one with C steel strand is secondary. The amount of prestress introduced due to the tension of the PC steel strand is a "mild" small value. For example, it was set to 10 to 15 kgf / cm ² . This makes the adhesive effect of the adhesive between the precast blocks sufficient. In the present invention, since the prestress introduced by the tension of the PC steel has a small value in the PRC structure, the precast block does not require a high flatness of the joint surface. Therefore, it is not necessary to perform a mirror-finish treatment on the joint surface of the precast block or make the joint surface a match cast. As a result, in the present invention, the precast block can be manufactured as a single unit, and it is not necessary to consider the manufacturing order, so that the manufacturing process of the precast block is simplified.

(B) The arrangement of the main reinforcing bars is not performed at the time of manufacturing the precast block, but the insertion holes are formed by a sheath or the like at the time of concrete casting, and after the precast blocks are stacked, the reinforcing bars are inserted through the insertion holes. It is. The main reinforcement and the block are fixed by grouting. The number of joints can be reduced by rear-inserting the main reinforcing bar, the concentration of the joints on the joint surface can be eliminated, the joint work can be simplified, and the complexity of manufacturing can be improved. In addition, since the through-rebar is grouted after the tension of the PC steel strand, prestress is effectively introduced to the entire cross section of the precast block without being restricted by the rebar.

(C) After completion of stacking of the precast block, the PC steel strand is drawn in from one side of the U-shape with a guide wire, passed through a sheath in the footing, and drawn out from the other side. Since the tension fixing of the PC steel material is performed collectively by the uppermost block, the number of fixing tools can be reduced, and the construction is simple. (D) Since the through-bar reinforces the joint surface between the precast blocks, special considerations such as a precast block having an RC structure, for example, a measure such as providing a shear key is not required.

(E) As a result, the construction period can be shortened.

[0017]

1 shows an example of a pier constructed by the construction method of the present invention. Reference block 2a on footing 1
A large number of precast blocks 2 are stacked via a bridge, and a pier (substructure) with a rectangular section of 6m x 4m and a height of 31m
Has been built. Main rebar 3 is 35mmφ × 160,
PC steel rod 13 for temporary fastening of assembly is 32mmφ × 24, PC
The steel strand 4 is a 12.4 mmφ × 12 × 7 cable. FIG. 2 is a plan view of the precast block, and shows the arrangement positions of the main reinforcing bar 3, the PC steel strand 4, and the PC steel rod 13 for temporarily fastening the assembly shown in FIG.

The construction method of the structure of the embodiment will be described below with reference to FIGS.
13 will be described. (1) Prior to placing footing 1 in concrete, Fig. 3
As shown in the figure, the steel tube 11 for inserting the main reinforcing bar, the U-shaped sheath tube 1
2. Assemble a steel frame 14 to which a PC steel bar 13 for temporarily fastening the assembly is fixed, and as shown in FIGS.
To be fixedly installed. Next, the reference block 2a is installed in the footing 1 so that it can be embedded about half.

(2) The footing 1 concrete is carefully poured in so that the steel frame 14 and the reference block 2a do not shift. (FIG. 6) (3) After the concrete strength of the footing 1 has developed, the precast blocks 2 are stacked using the crane 21 as shown in FIG. An epoxy resin adhesive is applied to the end face of the precast block 2, and the reference block 2a
The PC steel rods 13 for temporary tightening, which are erected from above, are used as a guide to stack four blocks, and the PC steel rods 13 are temporarily tensioned and temporarily fixed. Next, as shown in FIG. 8, the PC steel rods 13 for temporary assembling for four blocks in the next process are connected using the coupler 16.

(4) Next, four blocks are stacked while applying an epoxy resin adhesive to the contact end surface of the next block 2 on the last block of the previous process, and the PC steel rod 13 is temporarily tensioned and temporarily fixed. This is repeated up to a predetermined height. (5) When the stacking of the precast block 2 is completed to a predetermined height, as shown in FIG.
1 and insert it from the upper end of the block. At this time, as shown in FIG. 10, the main reinforcing bar 3 is connected using the coupler 16. The main reinforcing bars 3 are combined with different lengths so that the connecting positions in the longitudinal direction of the main reinforcing bars 3 do not concentrate on the same level position. The efficiency was improved by inserting a large number of main reinforcing bars 3 into the hanging jig 22 in a comb shape and inserting them at the same time.

(6) When the insertion of the main reinforcing bar 3 is completed, FIG.
As shown in FIG. 1, a PC steel stranded wire 4 was pushed from the open end of the sheath at the upper end of the precast block to a pushing machine 25.
Then, the wire is inverted through the footing 1 and pushed until the PC stranded wire protrudes upward from the open other end of the sheath and a tension allowance appears. In this embodiment, the guide wire is pushed and inserted by a pushing machine. However, it is also possible to insert a guide wire from a U-shaped insertion hole in advance before inserting a strand of PC steel, and to collectively insert the guide wire with the wire.

(7) Inserting a predetermined number of PC stranded wires 4
Is completed, U-shaped PC steel strand as shown in FIG.
Attach the fixing device 26 to both ends of the
And tension the PC steel strand 4 to pre-cast block.
10-15kgf / cm ^Two Inducing a degree of prestress
Enter. Because the main reinforcing bar 3 does not adhere to concrete
Do not restrain axial force. Therefore, a small amount of PC steel strand 4
Thus, prestress can be effectively introduced.

(8) When the tension of all the PC steel strands 4 is completed, grout is injected into the ducts of the PC steel strands 4, the main reinforcing bars 3, and the PC steel rods 13 to integrate the precast block. (9) Reinforcing bars and formwork are assembled on the pier thus constructed to construct a cross beam, and a bridge body is constructed.

The construction of the bridge pier of the above embodiment conventionally required about 5 months, but according to the method of the present invention, it could be reduced to 1.5 months. Moreover, the amount of rebar became about 2/3 of the conventional one. In addition, the toughness of the pier was improved, and the weakness of the main rebar joint of the precast block was eliminated. In addition, the thickness of the members can be reduced, and the weight can be reduced, and the main reinforcing joints are dispersed and not concentrated at the joints of the precast blocks, so that it is easy to construct lower structures such as tall piers. It has become possible.

FIG. 13 shows a connecting portion of a PC steel rod for provisional tightening. The PC steel rod 13 of the lower precast block 2 is fixed to a fixing plate 33 on the top surface by a fixing nut 32. The PC steel bar 13 is inserted into the upper precast block 2 and the upper and lower PC steel materials 1 are
3 and 13 are connected. In the method of the present invention, the pressure required to cure the adhesive by tensioning the strand of PC steel, ie, 1
Stress is introduced so as to be about 0 to 15 kg / cm ² , and then the main reinforcing bar is grouted to be integrated with the concrete of the precast block. Therefore, it is not necessary to mirror-finish the joint surface of the precast block, there is no weak point at the seam of the precast block, the amount of rebar can be reduced comprehensively, the structure is rich in rigidity and toughness,
The manufacturing process of the precast block is also simplified, and the construction of the substructure can be performed safely, at low cost, and in a short construction period.

[0026]

According to the method of constructing a substructure of the present invention, since the main reinforcing bars are inserted in the back and the PRC structure is used, the manufacturing accuracy of the joint surface can be made normal, and match casting,
There is no need for a mirror finish or the like, and the production order of the blocks is also free. In addition, high-quality structures are safe, efficient,
It has an excellent effect that it can be constructed in a short construction period.

[Brief description of the drawings]

FIG. 1 is an overall view of a structure according to an embodiment of the present invention.

FIG. 2 is a plan view showing a steel material arrangement of a precast block of a structure according to an example.

FIG. 3 is an explanatory view of a process of the present invention.

FIG. 4 is a process explanatory view of the present invention.

FIG. 5 is a process explanatory view of the present invention.

FIG. 6 is a process explanatory view of the present invention.

FIG. 7 is a process explanatory view of the present invention.

FIG. 8 is a process explanatory view of the present invention.

FIG. 9 is an explanatory view of a process of the present invention.

FIG. 10 is a process explanatory view of the present invention.

FIG. 11 is a process explanatory view of the present invention.

FIG. 12 is a process explanatory view of the present invention.

FIG. 13 is a detailed connection diagram of a PC steel rod for temporary assembly in the embodiment.

FIG. 14 is an explanatory view showing an example of a structure according to an embodiment to which the method of the present invention is applied.

FIG. 15 is a view taken in the direction of arrows AA in FIG. 14;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Footing 2 Precast block 3 Main reinforcing bar 4 PC steel strand 11 Steel tube for reinforcing bar 12 Sheath tube 13 PC steel rod 14 Frame 15 Reinforcing bar 16 Coupler 21 Crane 22 Suspension jig 23 Scaffold 25 Pushing machine 31 Coupler 32 Fixing nut 33 Fixing plate 35 Surface 36 grout injection hole

Claims (2)

(57) [Claims] 1. A U-shaped sheath is embedded in a footing,
A precast block having a main reinforcing bar insertion hole and a PC steel stranded wire insertion hole is stacked on the footing, the main reinforcing bar is inserted from above through the main reinforcing bar insertion hole of the stacked block, and the PC steel stranded wire is inserted. A PC steel strand is inserted from above through the insertion hole and the U-shaped sheath, and the PC strand is tensioned at the upper end of the uppermost block to introduce mild longitudinal prestress into the stacked blocks. After that, a grout is injected into the main rebar insertion hole and the PC steel wire insertion hole and adhered to the block to form a PRC structure. 2. The method for constructing a lower structure according to claim 1, wherein the through-bars are provided with joint positions at different heights.