JPH0548725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing prestressed concrete members.

``Prior Art'' As is well known, prestressed concrete members are a new structural style that differs from conventional reinforced concrete structures. It is a concrete member with a structure that gives a certain fixed stress state (hereinafter referred to as prestress) to the concrete cross section so that it occurs.

A post-tension method is known as a method for providing such a stress state, that is, pre-stress. In this method, a prestressed steel material to which no tensile stress is applied is placed in a hole in a concrete member (a hole formed by a sheath, etc.), and the concrete member itself is used as a supporting material to apply tensile stress to the prestressed steel material.
This is fixed to the concrete member via a bearing plate or the like to apply prestress.

``Problems to be Solved by the Invention'' By the way, in the post-tension method, many methods have been implemented for the end fixing device and tension device of the prestressed steel material. Construction methods can be broadly divided into those that use wire rods (cable or strand wedge anchoring) or steel rods (screw anchoring).

However, each of these construction methods has its advantages and disadvantages. For example, in the method using the wire rod, the tensile force per unit is large and the adhesion force is large, and the bending ratio when arranging in a curved line can be reduced, but there is some damage during fixation. There are problems that need to be solved, such as the error in the introduced prestress increases with short members that are misaligned. In addition, although the construction method using steel rods has the advantage that there is little error in the introduced prestress, it also has the problem of being unsatisfactory in terms of cost.

The present invention was proposed in view of the above circumstances, and
The purpose of this invention is to provide a method for manufacturing prestressed concrete members that is effective in efficiently introducing prestress even in short concrete members, has low overall construction costs, and has good workability on site. .

"Means for Solving the Problems" In order to achieve such an objective, the present invention has the following features:
No tensile stress applied to concrete members
After the prestressing steel material is installed, a tensile stress is applied to the prestressing steel material, and at least one end of the prestressing steel material is fixed to the concrete member via a bearing plate using a wedge anchor to introduce prestress. In the method for manufacturing concrete members, after the prestressing steel material is fixed using the wedge fixing tool, the end of the prestressed steel material is again tensioned using a tension jack to create a tensile stress of the same magnitude as the initially applied tensile stress. After that, a filler is filled in the space between the end of the concrete member and the bearing plate, and then, after the filler hardens, the tension jack is loosened and the end of the PC steel is fixed. The feature is that after fixing the end of the prestressing steel material with a wedge anchor to create a pull-in (PULL IN), tensile stress is applied to the prestressing steel material again, and the prestressing steel material is pulled by the amount pulled in by the pull-in to form a concrete member. This is a manufacturing method in which a filler is filled in the gap created between the bearing plate and the bearing plate to fill the gap and maintain the tensile stress level.

``Example'' Hereinafter, an example of the method for manufacturing a prestressed concrete member of the present invention will be explained in order of steps. ``Step of introducing prestress in the first stage'' As shown in FIG. Insert the PC steel material 2 into the PC steel material insertion hole 1a, fix one end (not shown) of the PC steel material 2, insert the other end into the bearing pressure plate 3, and then
A wedge fixture 4 is attached to the other end of the steel material 2. This wedge fixing device 4 consists of a pedestal 5 having a tapered insertion hole 5a through which the prestressed steel material 2 is inserted, and a plurality of wedges 6 inserted into the insertion hole 5a. One end is inserted into the insertion hole 5 of the pedestal 5.
a, and the wedge 6 is inserted between the pedestal 5 and the prestressing steel material 2 and assembled.

In this way, once the PC steel material 2 is placed on the concrete member 1 and the wedge anchor 4 is attached to one end thereof, the PC steel material 2 is pulled as shown by arrow A using a tension jack or the like. 2 with the required tensile stress, one end of the PC steel material 2,
It is fixed to the wedge fixing device 4. At this time, since PULL IN occurs in the PC steel material 1, the PC steel material 1
is stopped when it is pulled in by ΔL.

"Filling process of filler material" After fixing the prestressed steel material 2, as shown in Figure 2, the end of the prestressed steel material 2 is tightened again using a tension jack to achieve the same tensile stress as the first one. A tensile stress of the same magnitude is applied to the PC steel material 2. Due to this operation, pull-in occurs in the PC steel material 2, and it is stretched by ΔL as it is pulled inward.
A distance G of ΔL is generated between the concrete member 1 and the bearing plate 3.

As shown in FIG. 3, this gap G is filled with a filler 7. As the filler 7, for example, ultra-quick hardening concrete is preferable in terms of exhibiting early strength, but it is not limited to this.
It may be a fast-curing resin.

"Step of introducing prestress in the second stage" When the filler (for example, ultra-fast hardening grout) 7 filled in the gap G reaches the required compressive strength, the tension of the tension jack is loosened, and one end of the PC steel material 2 is is fixed on the filler material 7 via the bearing plate 3 (see FIG. 3). At this time, since PULL IN does not occur in the PC steel material 1, a predetermined tensile force can be applied to the concrete.

In the prestressed concrete member A produced in this way, the end of the PC steel material 2 is fixed by the wedge fixing device 4 that causes pull-in, so that the required tensile stress is reliably maintained, and there are also advantages such as less error in introduced prestress even in short members.

In the above embodiment, the PC steel material 2 was constructed to be installed inside the sheath pipe, but for example, a lubricant such as grease may be applied around the PC steel material and coated with a plastic sheath. It may also be a so-called unbonded wire made of.

Further, in this embodiment, an example was shown in which prestress is introduced into the precast concrete member 1, but the process of introducing this prestress is, for example, by placing the PC steel material 2 to which no tensile stress has been applied in advance in the formwork. However, there may be a method in which tensile stress is applied to the prestressing steel material 2 after the concrete placed in the formwork has hardened.

"Effects of the Invention" As explained above, according to the present invention, the following excellent effects can be achieved.

(a) After fixing the end of the prestressing steel material with a wedge fixing device and causing a pull-in, tensile stress is applied to the prestressing steel material again, and the prestressing steel material is pulled by the amount pulled in by the pull-in to form a concrete member. Fill the space between the bearing plate and the bearing plate with filler material,
Since this gap is filled with a filler to fix the PC steel material, the tensile stress level can be maintained reliably and a decrease in introduced prestress can be prevented. Additionally, since it is a simple process that adds tensioning of the prestressing steel and filling with filler to the conventional prestress introduction process, the overall construction cost is low and workability on site is also good.

(b) As a result of the above, prestress can be introduced efficiently even in short members, and tensile stress can be reliably applied, so there is no fear that the amount of prestress introduced will be small.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention in the order of steps. Figure 1 shows the prestress introduction process in the first stage, Figure 2 shows the filler filling process, and Figure 3 shows the prestress introduction process in the second stage. FIG. 3 is a cross-sectional view showing each introduction step. 1... Precast concrete member, 2...
PC steel material, 3... bearing plate, 4... wedge anchor,
5...cradle, 6...wedge, G...〓between.

Claims (1)

[Claims] 1 After placing a prestressing steel material to which no tensile stress is applied to a concrete member, applying a tensile stress to the prestressing steel material, and fixing at least one end of this prestressing steel material to the concrete member using a wedge anchor via a bearing plate. In the manufacturing method of prestressed concrete members, which introduces prestress by applying prestress, after fixing the prestressed steel material using the wedge fixing device, the end of the prestressed steel material is again tensioned with a tension jack to remove the initial tension. A tensile stress of the same magnitude as the stress is applied to the prestressing steel material, then a filler is filled in the space between the end of the concrete member and the bearing plate, and after the filler hardens, tension jacks are applied. A method for manufacturing a prestressed concrete member, characterized by loosening and fixing the ends of a prestressed concrete member.