JPH0587626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a structure for anchoring unbonded PC steel strands in the middle of a slab for introducing prestress into a slab of a building structure or the like.

[Conventional technology]

When applying prestress to concrete members using the post-tension method using unbonded PC steel strands to control slab deflection and cracking, use unbonded PC steel strands using special jacks after curing and hardening of the poured concrete. Requires line tension work.

However, if there is an obstacle near the end of the slab that prevents the installation of the tensioning jack, tensioning work at the end of the slab is not allowed.

Therefore, conventionally, in such cases, the sixth
Prestress is applied to the slab by tensioning in the manner shown in Figures 8 to 8.

That is, Fig. 6 shows a method that is used when tension cannot be created at both ends of the slab 2 and concrete is poured at once, and prestress is applied from one end of the slab to the center. An unbonded PC steel stranded wire 1 to give a prestress and an unbonded PC steel stranded wire 1' to give prestress from the other end to the center are arranged so as to overlap each other near the center,
Furthermore, inside the slab, a pocket 3 for tension work, which was cut out during concrete pouring, is provided in contact with the bearing plate 4, and after fixing the end of the slab with a fixing device 5, it is attached to the unbonded PC steel. The wires 1 and 1' are tensioned in the opposite direction at the pocket 3 using a jack (not shown) to introduce prestress into the concrete. 6 in the figure shows the tensioning fixture supported by the bearing plate 4, and the arrow indicates the tensioning direction of the wires 1 and 1' from the unbonded PC steel due to jacking.

On the other hand, the method shown in Fig. 7 is a method in which concrete is placed in sections A and B separately, and wires 1 and 1' of the unbonded PC steel are both tensioned at the center of the slab. The stranded wire 1' is tension-fixed at the joint 7 to introduce prestress into the previously poured section B, and then concrete is poured into section A, and the pocket 3 prepared in advance in section B is poured. In this section, wire 1 from the other unbonded PC steel is fixed under tension to introduce prestress into section A.

In the method shown in Fig. 8, it is possible to tension one end of the slab, but due to reasons such as the slab being too long in the compression direction, the wire 1
This is used when it is necessary to split wiring 1' into sections A and B by using pocket 3 provided in section B, and prestressing sections B by performing tensioning work at the end of the slab. Introduce. This is the same when concrete is poured all at once, or when concrete is placed in sections A and B, as shown in the figure.

[Problem to be solved by the invention]

All three methods described above are unbonded.
The need to wrap the PC steel strands near the center of the slab results in wasted material.

In addition, when concrete pouring is carried out in two sections, it is necessary to pre-wire a part of the unbonded PC steel wire from the subsequent pouring section to the preceding pouring section, and also to Unbonding on the ward side
In order to eliminate any hindrance to the work, the prestressed steel strands must be bundled until the reinforcing bar placement for the subsequent pouring section is completed, which is usually done after the completion of the preceding section.

Furthermore, since a fixing device is used for each unbonded PC steel strand, this increases the cost and the number of work hours.In addition, the prestress in the opposite direction is applied to the slab at the lap of the unbonded PC steel strand. The shearing force caused by

Furthermore, in Japanese Patent Application Laid-Open No. 191868, a notch is provided in the butt part of two concrete pieces, a coupler is placed in the cutout, and by connecting the left and right PC steel members with this coupler, the cutout can be made at the coupler installation part. It is shown that tension work is performed, but in this structure, the coupler is suspended in the air and the left and right steel members are connected in a series, so if the object to be reinforced is long, it is difficult to apply an average compressive force to the entire area. It becomes difficult. In addition, when adding an opening etc. to the object later, it may be required to maintain tension in one steel material and release tension in the other steel material, but it is not possible to meet this request. .

[Means to solve the problem]

In order to eliminate the above-mentioned problems, this invention has been developed using unbonded PC steel that applies prestress from one end of the slab to point Q midway through wire 1 and from unbonded PC steel that applies prestress from the other end to point Q. When wire 1' is placed in the slab and one end of the stranded wire of at least one of wires 1 and 1' is tension-fixed at the Q point, the unbonded PC steel is placed in the Q point. A bearing plate is provided in which the stranded wires 1 and 1' are passed through in opposite directions, and one side and the other side of the bearing plate are supported separately by slabs on both sides of the Q point. Two or more unbonded PC steel stranded wires 1 and 1' are arranged so that no rotational moment is applied to the bearing plate, and are fixed in opposite directions so that the bearing forces on both sides of the bearing plate are balanced. be.

[Effect]

According to the above-mentioned fixing structure, the amount of wrap at the point Q of the unbonded PC steel strands 1, 1' should be equal to the thickness of the bearing plate.

In addition, since both unbonded PC steel strands 1 and 1' are fixed to the same bearing plate, the number of bearing plates used and the effort required for installation can be reduced, and when concrete is poured in two sections. In addition, as can be seen from the examples described later, unbonding of the subsequent pouring area
This eliminates the need for the PC steel stranded wire to be buried in the concrete in the pre-cast area.

Furthermore, since the unbonded PC steel strands 1 and 1' are wrapped in the same bearing plate, the shearing force due to the opposite prestress acts on the strong bearing plate, and no shearing force is applied to the slab. .

In addition, since stress is applied separately to the left and right sections of the Q point, it is possible to apply an average compressive force to the entire area even in long slabs. It is also possible to relieve tension.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 to 4. In each figure, 8 indicates a bearing plate provided at point Q in the middle of the slab in the compression direction, and 1 to 7, excluding 4, indicate the same elements as those described in Figs. 6 to 8, respectively. There is.

Now, among these embodiments, the anchoring structure shown in FIG. First, unbond PC steel strand wire 1
curing of concrete poured in advance in section A,
After curing, set the tension fixing tool (grip) 6 and tension jack on the B section side of the bearing plate and fix it under tension.
After that, wire the unbonded PC steel stranded wire 1' to the B section side (the tension end of this wire is passed through the hole in the bearing plate 8 at this time), pour concrete, and unbond PC steel stranded wire after the concrete hardens. After the wire 1' is tensioned and the wire 1' is fixed by the tension fixing device 6, the wires 1 and 1' are supported in opposite directions by the same bearing plate 8 from the unbonded PC steel of both sections.
In this case, the tensioning work for the unbonded PC steel strand wire 1' is carried out in advance on the bearing plate 8 when concrete is poured in section A.
This is done by using a die-cutting pocket 3 provided in contact with the mold.

Next, in the anchorage structure shown in Fig. 2, in order to place concrete at once, pockets 3 are provided in both sections A and B in contact with both bearing plates 8, and unbonded PC steel strands 1 and 1 are connected to each other. ' are fixed under tension after curing and hardening of the concrete, and are supported in opposite directions by bearing plates 8.

In addition, the structure shown in Figure 3 allows for tensioning at one end of the slab 2, and is adopted when concrete is poured in two steps. With the positional relationship of the fixing device 5 and tension fixing device 6 reversed from that shown in Fig. 1, the prestress introduction work to section A by tensioning the wire 1 from the unbonded PC steel was carried out at the slab end, and then the Each unbonded PC steel strand wire 1, 1' is fixed to the bearing plate 8 through the same work process as on the B section side.

In addition, in both of the above examples, there is no unbonded PC in another section between the two unbonded PC steel strands 1'.
The steel strands 1 are arranged so that the rotational force due to the tensile force of each wire does not act on the bearing plate 8, but the effect in this regard is that the unbonded
The same result can be obtained even if the wires 1 and 1' are alternately arranged from PC steel.

FIG. 5 shows an example in which the unbonded PC steel wires 1, 1' are unevenly distributed. In this case, a rotational moment acts on the bearing plate 8, which is not preferable in terms of stabilizing the prestress applied to the slab.

In addition, the Q point at which the bearing plate 8 is installed is preferably set at the midpoint in the compression direction of the slab in order to equalize the amount of fatigue elongation of the wires 1 and 1' from the unbonded PC steel.

In addition, in the illustrated structure, wires 1 and 1' are distributed in equal numbers from unbonded PC steel, but for example, there are two wires 1' from unbonded PC steel per set, and two wires from unbonded PC steel in other sections. 1 is 2 of the above stranded wire 1'
It is also possible to use one wire with twice the strength. Such a distribution may be used to widen the wiring pitch for the purpose of installing openings in future slabs.

〔effect〕

As described above, in this invention, when unbonded PC steel strand wires wired in the compression direction are tension-fixed at point Q in the middle of a slab, a bearing plate is provided at point Q to pass the wires on both sides to support the wire. Since the unbonded PC steel wires on both sides are fixed to the pressure plate in the opposite direction, Q
The amount of lapping of the unbonded PC steel strands at the points is extremely small, and the number of bearing plates used is also reduced, so there is no wastage of material, which is economically advantageous.

Furthermore, when concrete is placed in sections, there is no need to pre-wire the subsequent sections, and the effort required to install bearing plates is reduced, improving work efficiency and shortening work time.

Furthermore, since pressure in opposite directions acts equally on both sides of the bearing plate, continuous prestress can be introduced into the slab in the same way as when a continuous line is wired from one end to the other. There is no shearing force acting on the slab at this point, and the original characteristics of the prestressing method using unbonded PC steel strands can be fully demonstrated.

In addition, since the bearing plate is applied to the slab on both sides of the Q point, it is possible to apply compressive force with little variation even to long slabs, and later, the tension force on only one steel wire is released and added. It is also possible to carry out construction work.

[Brief explanation of drawings]

1 to 4 are diagrams showing an example of the fixing structure of the present invention, FIG. 5 is a diagram showing an example of an unfavorable fixing structure, and FIGS. 6 to 8 are diagrams showing an example of the fixing structure of the present invention.
FIG. 2 is a diagram showing an example of a conventional fixing structure. 1, 1'... Unbonded PC steel stranded wire, 2... Slab, 3... Pocket, 4... Bearing plate, 5... Fixed anchor, 6... Tension anchor, 7... Splicing part, 8
...Bearing plate, A, B...Divided concrete pouring work area.

Claims (1)

[Claims] 1 Place unbonded PC steel stranded wire 1 that applies prestress from one end of the slab to point Q midway through the slab, and unbonded PC steel stranded wire 1' that applies prestress from the other end to point Q in the slab, and A pressure plate is installed at point Q , and one side and the other side are separately supported by slabs on both sides of point Q, and on the pressure plate, unbonded PC steel strands with a total number of 2 or more per set are attached. 1' is arranged so that no rotational moment is applied to the support plate, and the wires 1 and 1' are pulled in the opposite direction. At least one of these unbonded PC steel stranded wires 1 and 1' is tensioned at the point Q, and then the support plate is pulled out. An anchoring structure for unbonded PC steel strands, which is characterized by being anchored to the pressure plate in a state where the bearing forces on both sides of the pressure plate are balanced.