JPH0481008B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" When constructing a concrete structure, this invention applies to the already formed concrete structure.
The present invention relates to a method of constructing a prestressed concrete structure extending between concrete structures.

"Conventional technology" As is well known, as a prestress introduction method when manufacturing prestressed concrete structures,
Conventionally, there are a pretension method and a posttension method. The former is a method in which tensile force is applied to the prestressing steel, concrete is poured, and after the concrete has hardened, the tensile force applied to the prestressing steel is transferred to the concrete through adhesion between the prestressing steel and the concrete, giving prestress. In the latter case, when pouring concrete, a sheath is embedded in the position where the prestressing steel material is passed through, and after the concrete has hardened, the prestressing steel material is passed through the sheath and one end is fixed.
The other end is tensioned by water pressure or hydraulic jacks, and the reaction force applies strong compression to the concrete, which is then fixed using wedges, screws, etc. In this case, in order to protect the steel material and ensure the safety of the members, it is desirable to inject mortar into the lead-through hole to attach the steel material to the sheath (bond construction method).

"Problems to be Solved by the Invention" However, each of the above two methods had the following problems.

In other words, in the pretension method, there is no cost for the anchoring part, and there is no need for construction such as grout injection, but it does require a sturdy reaction force platform (abbutt) to pre-tension the prestressing steel. With the post-tension method, it is relatively easy to introduce prestressing on-site because it does not require very large tensioning equipment, but it takes time and effort to arrange the sheath and fill it with grout. .

Furthermore, when introducing prestress using prestressed steel materials, the placement of the prestressed steel materials must be made in such a way as to correspond to the stress generated in the member, in other words, to cancel out the stress generated in the member. For example, if the member is considered as a simple beam, the moment of bending is large at the center and small at the ends.
The prestressing steel material is placed at the bottom end of the beam at the center of the beam, and at the top end near the ends of the beam, near the columns. For example, in the case of prestressed precast concrete, the prestressed precast concrete is tensioned in a straight line by pulling it down at the center of the member, while in the post-tensioning method, the sheath is placed in a bent position. There is. However, the production of prestressed concrete using the pretension method is usually carried out in factories equipped with equipment such as large abutments (reaction tables), so this is possible; In the method of bending the prestressing steel, when tensioning the casting,
Because of the large frictional resistance, the tension applied at one end could not be transmitted to the other end, resulting in the inconvenience that prestressing had to be applied by dividing it.

The present invention was made in view of the above circumstances, and
It eliminates work such as installing a sheath over the entire length of the structure and filling it with grout, and also eliminates the need for large butts that require time and effort to transport and set up.Moreover, the tension of the prestressed steel material arranged in bends can be applied to multiple bends. The purpose of this is to provide a method of introducing prestress that can be sufficiently transmitted to distant places via.

"Means for Solving the Problems" Therefore, in order to achieve the above object, the present invention first performs vertical construction when constructing a concrete structure having horizontal structural parts such as beams and floor slabs that connect multiple columns. A method of constructing a prestressed concrete structure in which the horizontal structural part extends between the columns and prestressed concrete steel is bent inside the plurality of columns, the method comprising: A step of providing a sheath on each of the horizontal structural parts at both ends and pouring concrete thereon to form a reaction force support body that is integrated with some of the plurality of columns, and a prestressing steel material to be installed. A roller support body is made up of a shoring that supports the bent part of the shaft, and a fixed arm that is fixed to the shoring and has a stay at the end. The opposing ends are fixed to the upper side parts of the plurality of columns, and the shoring and stay of the roller support body is allowed to move in the direction in which the PC steel material is arranged;
and a step of installing a roller bending point part for bending the PC steel material, and providing a PC steel material extending between the reaction force supports with the roller bending point part as a bending point, and connecting one end of the PC steel material to one of the reaction force supports. The process of inserting the other end into the sheath of the other reaction force support and attaching it to a tensioning jack that is supported and fixed as a reaction force stand, and tensioning the PC steel material with the tensioning jack. and a step of placing concrete to form the intended prestressed concrete structure after tensioning the prestressed steel material, and a step of placing the above-mentioned concrete after hardening of the poured concrete.
The process includes the process of introducing prestress into concrete by releasing the tension in the prestressing steel.

``Function'' Reaction force supports are formed at both ends of the prestressed concrete structure to be constructed, and these are used to
In order to tension steel materials, there is no need to separately install a reaction force table, which is generally heavy, so it is possible to tension prestressed steel materials on site without using a large-scale reaction force table. In addition, most of the prestressed concrete structures that are formed are prestressed using the so-called pretension method, which eliminates most of the work such as sheath placement and grout filling. Furthermore, the roller bending point part reduces the frictional resistance of the prestressed steel material to be tensioned as much as possible, has a bending part, and makes it possible to complete tensioning of the prestressed steel material over a long period of time once.

"Embodiments" Examples of the present invention will be described below with reference to FIGS. 1 to 6. These figures illustrate the invention.
This is an example of application to the construction of beams for RC (reinforced concrete) structures.

Figures 1 to 3 show a first embodiment of the present invention, and in the figures, what is indicated by the reference numeral 1 as a whole is a concrete structure to be constructed, and Figure 1 shows the concrete structure that constitutes this concrete structure 1. The figure shows a state in which reinforced concrete columns 2 have already been constructed, and a beam 3 spanning these columns 2 is being formed in the middle of the construction process. The pillar 2 has a foundation 17 placed in the ground G, and is structurally reinforced by underground beams 18. Further, the columns 2 are attached with formwork 16 for forming beams 3 spanning these columns 2.

Then, the following method is used to construct beams 3 on the pillars 2 that span these pillars 2.

First, concrete is poured into a portion corresponding to one span at both ends of the beam 3 to be constructed to form the reaction force support 4 which will form the body with the column 2. this is,
This method is based on the "Method for constructing prestressed concrete structures" (Japanese Patent Application Laid-Open No. 14936/1983) previously filed by the present applicant, and sheaths 15 are embedded in each of the reaction force supports 4.

Next, a roller bending point portion 5 is installed by providing a roller support 6 at a portion of the PC steel material that will be a bending point. The roller support body 6 is for fixing the roller break point part 5 at a predetermined position within the formwork 16, and in this first embodiment, as shown in FIG. It consists of two things. The shoring 7 resists the downward force of the roller corner portion 5, and its lower part is supported by the underground beam 18. One of the position-fixing arms 8 resists the upward force of the roller corner portion 5, has its base end firmly fixed to the column 2, extends in the direction in which the beam is constructed, and has its end portion fixed firmly to the pillar 2. A roller break portion 5 is provided via a stay 8a that protrudes from the formwork 16. The roller bending point part 5 is a bending point of the PC steel wire, which will be described later.
PC to allow longitudinal movement of PC steel wire
It has a rotation axis in a direction perpendicular to the direction in which the steel wires are arranged.

Once the installation of the roller corner part 5 is completed,
A PC steel wire 9 is stretched between the two reaction force supports 4. The PC steel wire 9 is installed so as to pass below the roller corner 5 fixed by the position fixing arm 8 and above the roller corner 5 fixed to the shoring 7. Further, both ends of the PC steel wire 9 are extended to the outside of the reaction force support 4 by being inserted through the sheath 15 of the reaction force support 4.

Once the PC steel wire 9 has been installed, it is then tensioned. This process is the same as the method conventionally used to tension prestressing steel materials using the post-tension method. That is, as shown in FIG. 1, the fixing device 13 is attached to one end of the PC steel wire 9, and the other end is tensioned by setting the tensioning jack 14 and then operating the tensioning jack. At this time, the reaction support 4 acts as a reaction table for the fixing device 13 and the tension jack 14, respectively. At this time, the tensed PC steel wire 9 may be temporarily attached with a nut or wedge, and the jack 14 may be removed. The tensile force applied to the PC steel wire 9 is transmitted to the fixing device 13 side without being greatly attenuated due to the frictional resistance of the roller bending point 5 even at the bent portion.

Once the PC steel wire 9 is tensioned, then the formwork 16
Concrete 10 (not shown) for forming the intended beam 3 is placed in a portion located between the two reaction force supports 4. Since the PC steel wire 9 is already installed under tension between the two reaction force supports 4, the PC steel wire 9 is buried in the concrete 10.

When the poured concrete has hardened, the tension jack 14 releases the tension on the PC steel wire 9 caused by the nuts and wedges and removes the fixing device 13. Thereby, prestress is introduced into the poured concrete 10 using the same principle as that in which prestress is introduced into concrete by the so-called pretension method. In other words, when the tension of the PC steel wire 9 is released, a compressive force acts on the PC steel wire 9, and since the concrete 10 is attached to the PC steel wire 9, this compressive force is introduced into the concrete 10. In other words, prestress is introduced. Furthermore, if the sheath 15 is filled with grout after the PC steel wire 9 is tensioned, prestress is also introduced into the reaction force support 4 by the so-called post-tension bond method. After the concrete 10 hardens, the reaction support 4 becomes integral with the concrete 10 to form the beam 3.

As mentioned above, prestressed concrete beam 3
Once constructed, demolding and removal of the roller support body are carried out. When removing the roller support body 6, the roller support arm 7a on the upper part of the support structure 7 and the stay 8a at the tip of the position fixing arm 8 are removed. a method of leaving it in a state where it is driven into the constructed beam 3;
There is a method of removing the entire roller support 6 while leaving only the roller break point 5 inside. If the latter method is used, in which all the roller supports 6 are removed, when installing the shoring 7 and the position fixing arm 8, the portions of the roller supports 6 located inside the beams 3, i.e. A sleeve or the like is provided on the roller support arm 7a and the stay 8a to cover the outside thereof, thereby preventing the roller support arm 7a and the stay 8a from coming into contact with the poured concrete 10, and preventing the roller support arm 7a and the stay 8a from coming into contact with the concrete 10 even after the concrete 10 has hardened. Take measures to remove these.

According to the method for constructing a prestressed concrete structure as described above, the tensile force applied to the prestressed steel material is transmitted to the end portion without being greatly attenuated due to the friction reduction effect of the roller corner portion 5. Tensioning of prestressing steel over a long structure can be done in one go. In addition, it eliminates the hassle of arranging a sheath along the entire length of the structure and filling the sheath with mortar, improving structural strength by integrating prestressing steel and concrete, and resulting in synergistic effects such as a reduction in concrete volume. can be utilized.

Note that the number of roller break points 5 may be increased depending on the magnitude of the force that it receives and the degree of bending of the break points, or if the tension force must be changed between the roller break points, If necessary, the PC steel wire 9 may be fixed at the roller bending point. In the latter case, since a horizontal force is applied to the roller support 6, as shown in FIG. 3, the roller support 6, especially the roller support arms 7a,
Reinforce the stay 8a.

FIG. 4 shows a second embodiment of the present invention. In the second embodiment, a support 7 and a position fixing arm 8 are used as the roller support 6, similar to those shown in the first embodiment. is used, but the PC steel wire 9
are placed above and below beam 3, and the second
The PC steel wire 9a is a PC wire placed at the bottom near pillar 2.
It crosses the steel wire 9 and passes through the lower part of the beam 3. Therefore, two roller break points 5 are provided on each of the roller support arm 7a on the upper part of the support 7 and the stay 8a at the tip of the position fixing arm 8.

By inserting the PC steel wire 9 in this way, the beam 3
It is possible to increase the rigidity of the structure and increase its strength against concentrated loads or vibrations caused by earthquakes, etc. However, in carrying out this second embodiment, in order to comply with the original purpose of introducing prestress into concrete, the PC steel wire 9 inserted in the lower part is replaced with the second PC steel wire 9a inserted in the upper part. Introduce a tensile force greater than the

FIG. 5 shows a third embodiment of the present invention. In the third embodiment, the roller support 6 is attached to the upper part of the column 2 using the reinforcing bars 2a of the column 2.
The roller support body 6 may be a steel plate or may be a thick reinforcing bar. A roller support arm 7a and a stay 8a are provided at a predetermined upper position and an end portion of the roller support body 6, respectively, so that the roller break point portion 5 is installed.

In the third embodiment, the roller bending point 5 is different from that shown in the first and second embodiments.
can be easily supported.

FIG. 6 shows a fourth embodiment of the present invention, in which the upper part of the pillar 2, that is, the PC
A sheath 12 for a bent part is provided in advance in the arrangement form of the PC steel wire 9 at the part where the steel wire 9 is bent, and a roller bending point part 5 is temporarily installed at the bent part, and then concrete 10a is placed there. Play first with 2. The rotating outer circumferential surface of the roller bending point part 5 projects into the sheath 12 at the bending point of the bending part sheath 12. And this concrete 10a
After hardening, the PC steel wire 9 is attached to the bending part sheath 12.
or have been inserted in advance.
Tension the PC steel wire 9. That is, the concrete 10a is used as the roller support 6. The other steps are the same as those of the first embodiment.

Although the function of the fourth embodiment is the same as that of the first to third embodiments, the fourth embodiment is applied when forming the reaction force support 4 shown in FIG. Then, the transmission loss of the tension force of the PC steel wire 9 will be further reduced.

Although the above four embodiments describe beams of RC structures, the present invention is not limited to these examples, and may of course be applied to SRC (steel reinforced concrete) structures. wall,
It can also be used for

"Effects of the Invention" As explained above, the present invention provides a method for constructing concrete structures that have horizontal structural parts such as beams and floor slabs that connect multiple columns. A method of constructing a prestressed concrete structure in which the horizontal structural part extends between the horizontal structural parts and the prestressed concrete steel material is bent and arranged inside the prestressed concrete structure. A step of providing a sheath and pouring concrete therein to form a reaction force support body that is integrated with some of the plurality of columns, and shoring to support the bent portion of the prestressing steel material to be installed. and a roller support consisting of a position fixed arm fixed to a shoring and having a stay at the end, the support is supported on an underground beam, and the end opposite to the stay attachment end of the position fixed arm is connected to the plurality of roller supports. a step of installing a roller bending point part fixed to the upper side of the column, allowing movement in the installation direction of the prestressing steel material to the shoring and stay of the roller support body, and bending the prestressing steel material; and the roller bending point part. A PC steel material extending between the reaction force supports is provided with the bending point at
One end of the steel material is inserted into the sheath of one reaction force support and fixed, the other end is inserted through the sheath of the other reaction force support, and this is attached to a tension jack that is supported and fixed as a reaction force stand. PC due to the tension
a step of tensioning the steel material, and a step of pouring concrete to form the intended prestressed concrete structure after tensioning the prestressed steel material;
After hardening of this poured concrete, the PC
Since the process involves introducing prestress into the concrete by releasing the tension in the steel, there is no need to install a separate reaction table, which would normally be heavy, so a large-scale reaction table is used. PC steel wire tensioning can be carried out on site without
Moreover, due to the friction reduction effect of the roller bending point,
Since the tensile force applied to the prestressing steel material is transmitted to the end without significant attenuation, tensioning can be applied to the entire length of the prestressing steel material in one go, without having to divide it over a long structure. In addition, most of the structures are prestressed using the so-called pretension method, which eliminates the hassle of installing a sheath over the entire length of the structure and filling the sheath with mortar. It is possible to take advantage of synergistic effects such as improving structural strength through integration and reducing the concrete volume associated with it.This has various excellent effects, such as shortening the construction period and reducing costs.

[Brief explanation of the drawing]

1 and 3 illustrate one embodiment of the present invention, in which FIG. 1 is a front sectional view of a concrete structure, and FIG. 2 is an enlarged partial front sectional view of the upper part of a column in FIG. 1. FIG. 3 is a partial front sectional view showing reinforcing members 19a and 19b attached to the roller support 6 in FIG. 2. FIG. 4 is a partial front sectional view of a concrete structure illustrating a second embodiment of the present invention. 1... Concrete structure, 2... Pillar, 3...
Beam, 4... Reaction force support, 5... Roller break point,
6...Roller support, 9...PC steel wire.

Claims (1)

[Claims] 1. When constructing a concrete structure with horizontal structural parts such as beams and floor slabs that connect multiple columns,
A method of constructing a prestressed concrete structure in which a plurality of columns that have been erected in advance serve as the horizontal structure extending between the columns, and a prestressed steel material is bent inside the prestressed concrete structure. A step of providing a sheath at each of the horizontal structural parts at both ends of the structure and pouring concrete therein to form a reaction force support body that is integrated with some of the plurality of columns; should
A roller support body consisting of a shoring that supports the bending part of the prestressing steel and a fixed arm that is fixed to the shoring and has a stay at the end.The shoring is supported on an underground beam, and the stay attachment end of the fixed arm A roller bending point part is fixed to the upper side part of the plurality of pillars, and allows movement of the prestressing steel material in the installation direction of the prestressing steel material to the shoring and stay of the roller support body, and bends the prestressing steel material. A step of installing a PC steel material extending between the reaction force supports with the roller bending point as a bending point, and inserting and fixing one end of the PC steel material into the sheath of one reaction force support, and fixing the other end of the PC steel material. is inserted into the sheath of the other reaction force support, and attached to a tensioning jack that is supported and fixed as a reaction force table, and the prestressing steel material is tensed by the tensioning jack, and after the tensioning of the prestressing steel material is It is characterized by comprising a step of placing concrete to form a prestressed concrete structure, and a step of introducing prestress into the concrete by releasing the tension of the prestressing steel material after the placed concrete has hardened. A method of constructing prestressed concrete structures.