JP3437818B2 - Construction method of post tension type prestressed concrete - 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 post-tensioning prestressed concrete such as bridge girders and beam materials of buildings to which prestressing is introduced by the post-tensioning method.

[0002]

2. Description of the Related Art A post-tensioning prestressed concrete is a compressive stress equivalent to the tensile stress generated in a tensile edge by inserting a PC tension material into a concrete member formed by embedding a PC tension material insertion duct to tension the PC tension material. To P
It can be applied to concrete in advance by C steel material so that tensile stress does not occur on the tensile edge of concrete even when a load is applied, or it can be maintained within the range of allowable tensile stress of concrete. It is used for structures. This theoretically excellent prestressed concrete is also excellent in strength and can make a structure a rational cross section, and is particularly often used for bridge girders and beams of buildings. In such post-tensioning prestressed concrete, the PC tension material is tensioned, both ends are fixed to introduce stress into the concrete, and then a sealant such as mortar is injected into the sheath in which the PC tension material is stored. To integrate the sheath and PC steel.

FIGS. 10 to 12 show an example of a prestressed concrete girder (PC girder) 20 manufactured by the post-tension method used as a bridge girder, for example. FIG. 10 is a vertical cross-sectional view of a PC girder 20 having a T-shaped cross section, P
The C steel material 21 is fixed at both ends of the girder 20, and the tensile stress due to the bending moment generated by the load acting on the girder is PC
It is the figure stretched so that a steel material may take charge. Figure 11
10 shows the arrangement of the fixing member 22 fixed on the end face of the beam 20 in the EE arrow view of FIG. 10, and FIG.
7 is a layout view of the PC steel material 21 housed in the sheath 23 and attached by grout in the vicinity of the lower end of the girder 20 in the FF arrow view of FIG. In this way, by using the PC steel material 21 having a tensile strength several times that of the reinforcing bar, the PC girder 20 can reduce the total amount of steel material, increase the span of the girder, and reduce the weight, as compared with the girder made of reinforced concrete. Etc. have advantages.

However, the PC girder manufactured by this excellent post-tension method is a jack on the PC steel material inserted in a state where it is adhered to the surrounding concrete in a sheath which is a PC steel material insertion duct that penetrates the girder longitudinally. After applying a predetermined tension force and fixing the PC steel material at the girder ends to introduce prestress to the girder, grout (cement milk) is injected into the sheath to adhere the PC steel material to the sheath. This grout is a very important element such that the PC steel material is integrated with the girder and the PC steel material has an anticorrosive action. Therefore, it is possible to add various admixtures such as an expanding agent to cement milk or pressurize the cement milk so that the fluidity that can be completely filled around the PC steel material and the sheath and the breathing after the grout hardening does not occur. We carry out using technology such as.

There is also a technique that does not require grout.
For example, as a post-tension PC steel material called post bond that does not require grout, there is a technique in which an epoxy resin or the like is applied to the outer surface of the PC steel material. According to this technique, after the PC steel material is tension-fixed, the PC steel material and the resin are mounted and the resin is bonded to the concrete, so that adhesion and corrosion resistance can be obtained. But such a PC
Steel materials are not easy to handle, and there is a problem that a reliable bond between resin and concrete cannot be guaranteed.

[0006]

As described above, the PC steel material can be inserted into the sheath even if various admixtures such as an expanding agent are added to the cement milk or pressure injection is performed. It is difficult to completely fill the grout into the narrow space formed by inserting the PC tendons. For example, since the surface tension of the grout liquid acts, it is difficult to make the grout liquid sufficiently wrap around, and minute bubbles entrained by the grout liquid or excess water for hydration of cement hydrate aggregates. , A void or water pool remains in the middle of the sheath. FIG. 9 schematically shows this, in which the PC steel material 2 is placed in the sheath 23 embedded in the concrete 24.
1 is inserted, and a grout 25 is provided in the sheath 23. However, the air 26 entrained during the grout injection, the hydration surplus water, and the like create a void 26, which is originally the PC steel material 21.
Should have been covered by grout 25,
It will be exposed in this void. For a long period of time, chlorides and the like enter such voids to corrode the PC steel material, and eventually the PC steel material is broken, and concrete is peeled off. In reality, such a phenomenon occurs in some structures, which has become a social problem. This is because, as described above, the PC steel material 21 is inserted into the sheath 23 and then the narrow space is filled with grout later.
As one of the solutions, if the diameter of the sheath duct is increased, the filling becomes easier, but the concrete cross section is reduced correspondingly, and a problem of strength occurs. Therefore, there has been an urgent need to develop a technique capable of completely filling grout even in a sheath duct having a predetermined diameter similar to the conventional one.

As a result of intensive research to solve the above-mentioned problems, the inventors of the present invention have reviewed the order of steps and created the present invention. The present invention provides such a technology. It is intended.

[0008]

According to the present invention, when a tension force is introduced into post tension type prestressed concrete having a PC tension material insertion duct, a grout made of a time-curable filler is first introduced into the duct. After injecting it, and then immersing it in the uncured grout inside the duct, inserting the PC tension material and sealing both ends of the duct,
A post-tensioning prestressed concrete construction method, characterized in that the PC tension material is tensioned and prestress is introduced into the prestressed concrete member. As the time-curable filler, cement grout containing a delay-curable admixture is preferably used without limitation in working time. It should be noted that the sealing can be omitted in a duct having a shape in which there is no risk of grouting even if both ends of the duct are not sealed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. This example shows a schematic example applied to a prestressed concrete member having the most basic shape, and is simplified for easy explanation of the gist of the present invention. Types of steel materials
Of course, the quantity and the shape of the jig are not limited to these.

FIG. 2 is a vertical sectional view of a prestressed concrete (PC) member 10 used for explaining the present invention.
FIG. 4 is a view taken in the direction of arrows AA and BB in FIG. 2, respectively. The finished PC member 10 itself is not much different in appearance from those manufactured by the conventional technique. Prestress is introduced into the member by tensioning and fixing the PC steel material (PC tension material) 21 inserted in the sheath 23, which is a PC tension material insertion duct extending longitudinally in the member longitudinal direction, and the grout 25 is introduced into the sheath 23. The filled state is shown.

The feature of the present invention resides in that the grout is injected into the sheath disposed in the member prior to the insertion of the PC steel material, and then the PC steel material is inserted to fix the tension.

FIG. 1 is a process diagram for explaining the manufacturing process of the PC member shown in FIG. Although FIG. 1 shows only one end of the member, it is arbitrary whether the other end of the member is similarly processed or a functionally homogeneous structure is changed.

(A) A grout injection step is shown. The exhaust pipe 12 communicating with the sheath 23 near the end of the member is projected to the outside of the member 10, and the portion of the sheath 23 opening to the end face of the member 10 is enlarged in diameter so that the sealing material can be seated. The funnel tube 11 is fitted into the end face opening of the sheath 23 for filling grout, and the sheath in the member 10 is filled with the grout liquid 25 from the fitted funnel tube. As the grout 25 used here, a time-curable filler obtained by adding a setting retarder for delaying the setting of cement to cement grout containing cement as a main component is used. The delay time can be adjusted according to actual circumstances. In this way, by injecting the grout liquid prior to the insertion of the PC steel material, the sheath 2 without obstacles can be obtained.
It is possible to completely fill the space within 3.

(B) After the filling of the grout into the sheath is completed, the PC steel material 13 is continuously uncured.
Insert while immersing in 5 liquids. At this time, P to insert
The grout liquid corresponding to the volume of the C steel material 13 is discharged from the exhaust pipe 12. In addition, it is desirable to perform a treatment for preventing the grout liquid from adhering to the surplus tension work length of the tip of the PC steel material 13.

(C) P while leaving an extra working length of PC steel
It is a process drawing which inserts the sealing material 14 after insertion of C steel material is completed. As the sealing material 14 used here, a spongy material having elasticity and water sealing property is preferable, and, for example, a material obtained by impregnating a bituminous material into a polyurethane foam resin is preferable. Further, it may be sponge-like and impregnated with grout solution by a capillary phenomenon, and the impregnation time may be adjustable so as to match the grout hardening delay time.
Further, a material having an antirust effect is preferable.

(D) The sealing material 14 is pushed into the funnel tube,
It is the figure which is seated in the sheath diameter expansion part. The grout liquid in the funnel tube is pressed by the sealing material and leaks from the discharge tube.

(E) When the grout liquid is sealed in the sheath by the sealing material, the funnel tube 11 is removed and the PC steel material 1
The grout liquid adhered to the tension work portion 3 is wiped off, the fixing body is attached, and the tension jack 15 is attached to introduce prestress to the member 10. The introduction of prestress is completed,
The tension jack 15 is removed, the work length of the PC steel material is cut, and the pre-stressed concrete member 10 is completed by performing post-injection grout on the sheath between the sealing material and the fixing body.

FIG. 5 shows an example of a jig (pushing handle) 16 for pushing the sealing material 14 into the funnel tube 11 and the sealing material 14. 6 is a view taken along the arrow CC of FIG. 5, and FIG. 7 is a view taken along the arrow DD of FIG. Since the sealing material 14 has an elastic sponge shape, a steel plate disk 17 is attached to the jig 16 for seating the sealing material on the expanded diameter portion of the sheath via the funnel tube. Further, the sealing material 14 and the disk 17 have through holes for the number of PC steel materials that are inserted into the sheath. In this example, twelve through holes 18 are shown, but the number may be set as required for design. The through hole of the sealing material 14 has a diameter slightly smaller than the diameter of the PC steel material 11, and it is possible to prevent the grout liquid in the sheath from leaking from the opening.

FIG. 8 shows that it is difficult to completely prevent grout leakage when the sealing material 14 is inserted in the steps (b), (c) and (d) of FIG. It is explanatory drawing at the time of keeping a tail end side so that it may not contact a grout. As shown in FIG. 8A, the sealing material 1
The PC steel material 13 at the rear of 4 is covered with the inner cylinder 11b and the sealing material 14 is inserted into the funnel tube (outer cylinder) 11, and the sealing material 14 is inserted into the sheath 23 as shown in FIG. 8B. Then, as shown in FIG. 8C, if the outer cylinder 11 is pulled out in the direction of the arrow and then the inner cylinder 11b is removed, the portion of the PC steel material 13 outside the sealing material 14 will not be contaminated with grout. After that, the fixing step shown in FIG.

[0020]

According to the method of the present invention, the procedure of the method for constructing a prestressed concrete member by the post-tension system is reviewed, a concrete member having a duct is manufactured, and a time-curable filler is injected into the duct in advance. In advance (pre-grout method), by inserting the PC tension material into the filling material, the difficulty of injecting into the conventional narrow filling space is eliminated, and it becomes possible to manufacture a highly durable PC member.

[Brief description of drawings]

FIG. 1 is a process drawing of an example.

FIG. 2 is a vertical cross-sectional view of prestressed concrete of an example.

FIG. 3 is a view taken along the line AA of FIG.

FIG. 4 is a view taken along the line BB of FIG.

FIG. 5 is an explanatory diagram of a pushing jig.

6 is a view taken along the line CC of FIG.

7 is a view taken in the direction of arrows D-D in FIG.

FIG. 8 is an explanatory diagram of a sealing material inserting step.

FIG. 9 is a vertical sectional view of a sheath.

FIG. 10 is a vertical sectional view of a PC girder.

11 is a view as seen from the arrow EE of FIG.

FIG. 12 is a view on arrow FF in FIG.

[Explanation of symbols]

10 members 11 Funnel tube (outer cylinder) 11b inner cylinder 12 Exhaust pipe 13 PC steel 14 Sealant 15 Tension jack 16 jigs 17 discs 18 through holes 20 PC digits 21 PC steel 22 Fixed body 23 sheath 24 concrete 25 grout (liquid) 26 vacant places

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Claims (2)

(57) [Claims] 1. When introducing a tension force into a post-tensioning type prestressed concrete in which a PC tension material insertion duct is formed, a grout consisting of a time-curable filler is first injected into the duct, and then the duct inside the duct is injected. Unhardened
A post-tensioning method, in which a PC tension member is inserted while being immersed in a crushed grout , both ends of the duct are sealed, the PC tension member is tensioned, and prestress is introduced into the prestressed concrete member. Prestressed concrete construction method. 2. The method for constructing post-tension prestressed concrete according to claim 1, wherein the time-curable filler is cement grout to which a delay-hardening admixture is added.