JP7223391B2 - Structure for prestressed concrete - Google Patents

Description

The present invention relates to a prestressed concrete structure for prestressed concrete walls.

A conventional example of formwork and spacers used in the construction of concrete walls is shown in FIG. Conventional formwork spacers as shown in FIG. 5 are used for the purpose of maintaining the spacing between opposing formwork and preventing the formwork spacing from widening during concrete placement. There is prior art.

In the invention of "attachment and detachment device for concrete placing formwork" of Patent Document 1, a mounting hole is provided through the formwork in the thickness direction, and a bolt-shaped member is slidably and rotatably inserted into the mounting hole. , an attaching and detaching device for a concrete placing formwork is disclosed in which a nut-like member is screwed to one end of a bolt-like member protruding from the outer surface of the formwork.

In the invention of "Assembling and holding material for concrete formwork" of Patent Document 2, a stopper is provided in the middle part of the fastening rod, and a sliding part that is stopped by the stopper is provided in the intermediate fastening part between the stopper and the head. Assembly and holding of a concrete formwork in which a ring is fitted and the tip of an adjustment band protruding from a sliding ring is fixed to a connecting female screw body to maintain the shortest effective depth when adjusting the degree of spiraling of a fastening rod. materials are disclosed.

There is an invention of a "separator for form assembly" in Patent Document 3. The invention consists of a combination of two rods and joints which are directly or indirectly connected at one end of each to the formwork plate clamps, the joint being one rod at the other end provided with a projection. A mold assembly separator is disclosed that is fitted to the rods so that they can move relative to each other along their lengths and rotate relative to each other about the axis of the rods.

There is an invention of a "separator for formwork" in Patent Document 4. In this invention, the inner ends of a pair of separator-constituting rods arranged in series are slidably connected in the longitudinal direction of the rods via sliding connecting fittings attached thereto, and Each sliding connector is disclosed with a formwork separator provided with through-holes for insertion of locking members at locations where the separators are aligned when extended to a predetermined length.

The "formwork binding tool" of Patent Document 5 includes a tubular body that is penetrated and fixed to the dam, and a cone that is integrally attached to the projecting part of the dam on the side of the concrete placing surface in a penetrating state. It consists of a shaft that can be inserted in a rotatable and slidable manner for a certain length in a state that cannot be pulled out, and a threaded hole for screwing a threaded end of a separator that is inserted into the tube from the cone side is formed at the end of the shaft, and the other end of the shaft is the other end of the shaft. A mold binding device is disclosed in which a rotary operation portion is formed by protruding from the end of a tubular body, and a slide stopper is protruded from the portion.

JP-A-62-268467 Japanese Utility Model Publication No. 51-11239 Japanese Utility Model Publication No. 54-15946 Japanese Utility Model Laid-Open No. 51-045234 Japanese Utility Model Laid-Open No. 64-43143

In general, when placing concrete, a large number of separators are used to connect opposing formwork to each other and to keep the distance between the opposing formwork constant. Further, in the construction of the cylindrical prestressed concrete wall PC in which the circumferential tendon is tensioned and the prestress is applied to the concrete C, the prestressing causes the diameter of the cylindrical prestressed concrete wall to shrink. Therefore, when the prestress is applied, a pressure toward the center of the cylinder acts on the mold on the inner peripheral side.
Therefore, when the inner peripheral side formwork of the opposing steel formwork used for constructing a cylindrical prestressed concrete wall is a permanent formwork that remains as part of the structure to be constructed, the steel permanent formwork There was a risk that the steel would peel off or deform from the prestressed concrete wall.
In addition, considering the pressure acting on the steel permanent formwork on the inner peripheral side due to the tension of the prestressed concrete wall, it is possible to increase the thickness of the steel permanent formwork to increase the compressive strength. In some cases, there are problems such as a significant increase in the cost of the materials used.

Therefore, as a method of relieving the pressure acting on the steel permanent formwork on the inner peripheral side, a buffer material is attached in advance to the surface of the steel permanent formwork on the side where concrete is placed, so that when the prestress is applied, The applicant of the present invention has filed an application for a technique for reducing the pressure acting on the steel permanent form with the cushioning material to prevent the steel permanent form from being deformed or the like.
However, the opposing formwork used for placing concrete uses separators that connect the opposing formwork together to maintain the spacing between the formwork when the concrete is placed. There was a problem that the steel permanent formwork of the separator attachment portion did not have a cushioning material, and the pressure acting on the steel permanent formwork due to prestressing could not be reduced.

The conventional techniques described in Patent Documents 1 to 5 absorb the displacement in the direction of the center of the cylinder due to the application of prestress acting on the separator mounting portion of the steel permanent form, and the deformation of the steel permanent form. It does not relate to a structure for prestressed concrete intended to prevent damage or damage.

The present invention has been made in view of the problems of the prior art as described above, and its object is to construct a prestressed concrete wall by placing concrete between forms and applying a prestress force. A structure for prestressed concrete that is integrated with a spacer capable of maintaining a predetermined distance between the formwork against the concrete placing pressure and preventing deformation and damage of the steel permanent formwork. It is to provide the body.

A structure for prestressed concrete according to the invention of claim 1,
a steel plate, a bar-shaped steel member which is expanded by providing a flange at a first end thereof and serves as a spacer for prestressed concrete to which a temporary formwork is connected to a second end on the opposite side; A columnar member having an inner diameter larger than that of a first end, and having an end face having an insertion hole having a diameter smaller than that of said first end and through which said steel bar is inserted so as to be horizontally movable in its axial direction . A columnar member having one end inside thereof, and a cushioning material covering a portion of the columnar member and the steel plate facing the prestressed concrete ,
Inside the cylindrical member, the gap between the end face of the first end flange of the bar-shaped steel material and the inner surface side of the steel plate or the end portion of the stud provided on the inner surface side of the steel plate in the inward direction of the mold is formed by a press. It is characterized by having a length capable of absorbing displacement toward the center of the cylinder due to application of stress force .

A structure for prestressed concrete according to the invention of claim 2,
The cylindrical member is fixed to the steel plate by welding,
A stopper portion is provided on the end surface to abut against the collar portion of the steel bar and lock the steel bar in a retaining state,
The rod-shaped steel material is axially inserted into the fitting hole of the cylindrical member into which the collar part is fitted so that the collar part of the first end of the rod-shaped steel material abuts the stopper part of the cylindrical member. It is characterized by being fitted so as to be slidable .

A structure for prestressed concrete according to the invention of claim 3,
the cylindrical member is internally threaded and engages a stud fixed to the steel plate with the thread ;
A stopper portion is provided on the end surface to abut against the collar portion of the steel bar and lock the steel bar in a retaining state,
The rod-shaped steel material is axially inserted into the fitting hole of the cylindrical member into which the collar part is fitted so that the collar part of the first end of the rod-shaped steel material abuts the stopper part of the cylindrical member. It is characterized by being fitted so as to be slidable .

A structure for prestressed concrete according to the invention of claim 4,
Inside the cylindrical member, at a position that can be installed in the gap and is in contact with the first end of the steel bar, a prestressing force is applied to the steel plate to exert a force toward the center of the cylinder. It is characterized by the presence of cushioning material that absorbs displacement .

The structure for prestressed concrete of the present invention acts on the steel permanent formwork side when constructing a prestressed concrete wall by applying a prestress force to the concrete placed between the steel permanent formwork and the temporary formwork. It is possible to absorb the displacement toward the center of the cylinder and prevent deformation and damage of the steel permanent formwork.

FIG. 2 is a cross-sectional view during construction (right side) and after construction (left side) of an example of a new above-ground cylindrical tank 1 having a structure 9 for prestressed concrete according to the present invention. It is an enlarged view of the A part of FIG. 1, and is sectional drawing which shows the example of the detailed structure of the structure 9 for prestressed concrete. It is an exploded cross-sectional view showing an example of the detailed structure of the structure 9 for prestressed concrete of FIG.2(b). FIG. 4 is a cross-sectional view showing an example of the situation of the prestressed concrete structure 9 attached between the steel permanent form 4b and the temporary form 12 (a) during concrete placement and (b) during concrete tension. It is sectional drawing which shows the example of the detailed structure of the conventional structure 9 for prestressed concrete.

An embodiment of a prestressed concrete structure 9 according to the present invention will be described with reference to FIGS. 1 to 4. FIG. In addition, the present invention is not limited only to the following embodiments. It is of course possible to omit or add the components described below and to modify the embodiments such as the shape of the components without departing from the gist of the present invention. Moreover, the drawing shows an outline, only a part of which is drawn, and the detailed structure is omitted.

FIG. 1 is an explanatory side view of an example of a newly constructed above-ground cylindrical tank 1 having a structure 9 for prestressed concrete according to the present invention, where 2 indicates the ground, 3 the outer tank, and 4 the inner tank.
This cylindrical tank 1 of double-shell structure has a structure comprising an inner tank 4 made of metal and an outer tank 3 made of concrete surrounding the inner tank 4 . The left side of FIG. 1 shows a sectional view of the tank 1 after construction, and the right side shows a sectional view of the prestressed concrete side wall 3b of the tank 1 during construction.
The outer tank 3 has a structure comprising the concrete bottom slab 3 a and prestressed concrete side walls 3 b surrounding the side plates 4 b of the inner tank 4 .

An example of the order of constructing the side walls 3b made of prestressed concrete of the newly installed fixed-roof cylindrical tank 1 will be described.
Prior to constructing the side walls 3b of the outer tank 3, the bottom plate 4a and the side plates 4b of the inner tank 4 are constructed, and the inner tank side plates 4b are used as permanent steel forms 4b for placing prestressed concrete.
Subsequently, a columnar member 11 for attaching a bar-shaped steel material 10 acting as a separator is installed on the outer peripheral surface of the inner tank side plate 4b. Here, the inner tank side plate 4b is the steel permanent formwork 4b.
Subsequently, a temporary formwork 12 is temporarily installed at a distance of the concrete placement width W from the inner tank side plate 4b.
Subsequently, the inner tank side plate 4b of the permanent steel formwork and the temporary formwork 12 are connected with the bar-shaped steel material 10, and the concrete C is poured between both the formwork.
Subsequently, the prestressing force Ps is applied by tensioning the circumferential tendon 19 of the concrete C to construct the side wall 3b made of prestressed concrete. As a result, the outer tank side wall 3b is deformed in the direction of compressing the inner tank side plate 4b.

FIG. 2 is an enlarged view of part A in FIG. 1, and is a sectional view showing an example of the detailed structure of the structure 9 for prestressed concrete.
The prestressed concrete structure 9 has a permanent steel form 4b and a first end 10a that is expanded, and serves as a spacer for prestressed concrete construction in which a temporary form 12 is connected to the opposite second end 10c. It is composed of a bar-shaped steel material 10 and a cylindrical member 11 having an inner diameter larger than that of the first end 10a and fixed to the steel permanent form 4b.
Each component of the prestressed concrete structure 9 will be described in detail.
The bar-shaped steel material 10 has a structure in which a first end 10a is provided with a collar portion 10b and expanded.
The columnar member 11 has an end face having an insertion hole 11a which has a diameter smaller than that of the first end 10a and through which the steel bar 10 is horizontally movably inserted in the axial direction thereof. is located inside it.
The columnar member 11 has a stopper portion 11b on the end surface thereof, which abuts against the flange portion 10b and locks the flange portion 10b of the bar-shaped steel material 10 to prevent it from coming off.
The cylindrical members 11 are directly or indirectly attached to a plurality of locations on the outer peripheral surface of the steel permanent formwork 4b.
(a) is an example in which the cylindrical member 11 is fixed to the outer peripheral surface of the steel permanent form 4b by direct welding S or the like. (b) is an example in which the cylindrical member 11 has a threaded hole 11d inside, and the stud 25 fixed by welding to the steel permanent form 4b is engaged with the threaded hole 11d of the cylindrical member 11. .
The flange portion 10b of the first end 10a of the bar-shaped steel material 10 is fitted into the fitting hole 11c of the cylindrical member 11 so that the flange portion 10b of the first end 10a of the bar-shaped steel material 10 abuts against the stopper portion 11b of the cylindrical member 11. , the bar-shaped steel material 10 is fitted so as to be slidable in the axial direction.
The cylindrical member 11 and the steel permanent formwork 4b are provided with cushioning materials 8b covering the portions facing the prestressed concrete PC.
Inside the cylindrical member 11, a stud 25 provided on the end surface of the collar portion 10b of the first end 10a of the steel bar 10 and the inner surface side of the steel permanent form 4b or the inner surface side of the steel permanent form 4b. The gap 20 with the end portion 25b in the mold inward direction has a length L of several millimeters to several tens of millimeters. The length L of the gap 20 is set to a distance that can absorb the displacement toward the center of the cylinder due to the application of the prestress force Ps.
A buffer material 8c is provided in the gap 20. As shown in FIG.

FIG. 3 is an exploded sectional view showing an example of the detailed structure of the prestressed concrete structure 9 of FIG. 2(b).
D ₁ is the outer diameter of the steel bar 10 .
D ₂ is the inner diameter of the insertion hole 11a into which the bar-shaped steel material 10 of the cylindrical member 11 is inserted.
D ₃ is the outer diameter of the flange portion 10b extending from the first end 10a of the bar-shaped steel material 10 .
D ₄ is the inner diameter of the fitting hole 11c into which the flange portion 10b of the bar-shaped steel material 10 of the cylindrical member 11 is fitted.
Next, the relation of each dimension will be explained.
The outer diameter _D1 of the steel bar 10 is smaller than the inner diameter _D2 of the insertion hole 11a of the cylindrical member 11 and the inner diameter _D4 of the fitting hole 11c. The flange portion 10 b is placed inside the columnar member 11 .
The outer diameter _D3 of the flange portion 10b of the bar-shaped steel material 10 is set to a value larger than the inner diameter _D2 of the stopper portion 11b of the insertion hole 11a. Avoid slipping out of the columnar member 11. - 特許庁
In addition, the inner diameter _D4 of the fitting hole 11c of the cylindrical member 11 is set to a value larger than the outer diameter _D3 of the collar portion 10b of the bar-shaped steel material 10, and the collar portion 10b is positioned inside the fitting hole 11c of the cylindrical member 11. , so that the bar-shaped steel material 10 can move horizontally in the axial direction.

The following effects are obtained by using the structure 9 for prestressed concrete of the present invention.
The prestressed concrete structure 9 is easy to process and can be easily attached to a formwork, so that construction costs and material costs can be reduced.
It is possible to counteract the concrete pressure placed between the steel permanent form 4b and the temporary form 12 and reliably prevent the gap between the steel permanent form 4b and the temporary form 12 from widening due to the concrete pressure. It is possible.
When constructing the prestressed concrete wall PC by applying a prestressing force Ps to the concrete placed between the two forms, the first end 10a of the bar-shaped steel material 10 horizontally moves inside the columnar member 11, causing the steel to move. It is possible to absorb the displacement toward the center of the cylinder due to the prestress force Ps acting on the steel permanent form 4b, thereby preventing deformation and damage to the steel permanent form 4b.
When the steel inner tank side plate 4b of a double-shell tank is used as a steel permanent formwork 4b when concrete is constructed for the outer tank side wall 3b, the inner tank side plate 4b cannot be provided with the cushioning material 8a. To absorb the displacement due to the concrete placing pressure Pc and the prestress force Ps acting toward the center of the cylinder at the mounting portion of the bar-shaped steel material 10 on the outer peripheral surface, and to prevent the inner tank side plate 4b from being deformed or damaged. is possible.

Inside the cylindrical member 11, the end surface of the collar portion 10b of the steel rod 10 and the inner surface of the steel permanent form 4b or the form of the stud 25 provided on the inner surface of the steel permanent form 4b. By setting the gap 20 with the inward end 25b to a length L of several millimeters to ten-odd millimeters, the displacement toward the center of the cylinder due to the application of the prestressing force Ps can be displaced horizontally in the gap 20 by the steel bar 10. It is possible to absorb the movement and prevent deformation and damage of the steel permanent formwork 4b.

Furthermore, by providing the buffer material 8c in the gap 20, the steel bar 10 does not rattle in the columnar member 11 when the steel permanent form 4b and the temporary form 12 are connected and when the concrete is placed. It becomes possible to stably maintain the distance between frames.
The cushioning material 8c has a thickness capable of being installed in the gap 20 and capable of absorbing displacement toward the center of the cylinder acting on the side of the steel permanent formwork 4b due to the application of the prestress force Ps. Satoru.

Furthermore, by covering the portion of the cylindrical member 11 and the steel permanent formwork 4b facing the prestressed concrete wall PC with the cushioning material 8b, when the concrete is tensioned, the prestressing force Ps is applied to the cushioning material 8b by the cushioning material 8b. It is possible to absorb the displacement toward the center of the cylinder acting on the side of the steel permanent form 4b and to prevent deformation and damage of the steel permanent form 4b.

FIG. 4 is a sectional view showing an example of the situation of the prestressed concrete structure 9 mounted between the steel permanent form 4b and the temporary form 12 (a) during concrete placement and (b) during concrete tension. .
(a) At the time of placing the concrete, the placing pressure Pc of the concrete placed between the steel permanent form 4b and the temporary form 12 acts in the direction to widen the distance W between the two forms. The flange portion 10b of the first end 10a of the steel material 10 abuts against the stopper portion 11b of the cylindrical member 11, thereby holding the predetermined gap W between the two forms so as not to widen, and the designed width W of concrete is formed. It becomes possible to set.
In the concrete tensioning of (b), when the circumferential tension member 19 of the concrete between the steel permanent form 4b and the temporary form 12 is tensioned, pressure is applied toward the center of the cylinder by applying the prestressing force Ps, and the bar steel material The collar portion 10b of the first end 10a of 10 moves horizontally in the direction away from the stopper portion 11b of the cylindrical member 11, and is provided on the inner surface side of the steel permanent form 4b or the inner surface side of the steel permanent form 4b. The cushioning material 8c provided in the gap 20 between the stud 25 and the end portion 25b of the mold inward is compressed to absorb the displacement, and the rod-shaped cushioning material 8a cannot be installed on the inner surface side of the steel permanent form 4b. It is possible to prevent deformation and damage to the mounting portion of the steel material 10 due to the pressure toward the center of the cylinder due to the application of the prestress force Ps.

By using the structure 9 for prestressed concrete of the present invention, the following effects can be obtained during (a) concrete placement and (b) concrete tensioning.
In the mounting portion of the steel bar 10 where the buffer material 8b of the steel permanent form 4b cannot be provided, the flange portion 10b of the first end 10a of the steel bar 10 moves horizontally in the fitting hole 11c of the columnar member 11. The displacement due to the prestress force Ps is absorbed by the amount of movement, and the pressure acting on the steel permanent form 4b toward the center of the cylinder is reduced by applying the prestress force Ps, so that the steel permanent form 4b It is possible to prevent deformation and damage.
By covering the portion of the cylindrical member 11 facing the prestressed concrete wall PC with the cushioning material 8b, the displacement due to the pressure toward the center of the cylinder due to the application of the prestress force Ps acting on the cylindrical member 11 and the stud 25 is absorbed. It is possible to prevent deformation and damage of the steel permanent formwork 4b.
By installing the cushioning material 8c inside the cylindrical member 11 and in contact with the flange portion 10b of the first end 10a of the steel bar 10, the steel bar 10 can be easily secured when concrete is placed or tensioned. It is possible to stably maintain the distance between both forms without rattling.

The steel permanent formwork 4b is not only used as a formwork when the concrete is placed, but also remains as it is as the inner tank side plate 4b of the above-ground cylindrical tank 1 without being dismantled after the concrete is placed. Permanent formwork. The temporary formwork 12 is a formwork to be dismantled and removed after the concrete is placed.
Both 4b and 12 may be permanent forms.

The cushioning materials 8a to 8c are excellent in shock absorption performance, energy absorption performance, pressure dispersion performance, etc., and absorb displacement toward the steel permanent form due to the application of concrete placing pressure Pc and prestress force Ps. Use low-resilience urethane foam, etc., made of low-resilience materials that can
In addition, when applying to tanks that store flammable hazardous materials such as heavy oil and crude oil, use flame-retardant low-resilience urethane foam, etc., which is obtained by adding a flame retardant to the low-resilience material. .

The prestressed concrete structure 9 can also be applied to structures such as storages other than tanks where tsunami countermeasures are desired, and is effective for structures that need to construct side walls made of prestressed concrete.

1 (cylindrical) tank
2 Ground
3 (concrete) outer tank 3a bottom slab (foundation slab, reinforced concrete)
3b side wall (prestressed concrete)
4 (made of metal) inner tank 4a bottom plate 4b side plate (permanent steel formwork)
5 Storage liquid 6 Fixed roof 6a Roof frame structure 6b Roof plate 7 Top angle 8 Cushioning material 8a (Outer surface of side plate 4b) Cushioning material 8b (covering cylindrical member 11) Cushioning material 8c (inside cylindrical member 11) Material 9 Structure for prestressed concrete 10 Rod-shaped steel material 10a First end 10b Collar portion 10c Second end 10d Screw portion 11 Columnar member 11a Insertion hole 11b Stopper portion 11c Fitting hole 11d Screw hole 12 Temporary formwork 12a Hole 13 Cone 13a Screw hole 13b Threaded rod 14 Form tie 15 Thick end member 15a End thick member 15b End thick member 16 Washer 17 Nut 18 Form clamping rod 18a Threaded portion 19 Circumferential tension member 20 Gap 21 Bar member 21a First end 21b Threaded portion 21c Second end 21d Threaded portion 22 Stud 22a Threaded portion 23 Cover portion 24 Nut member 24a Threaded hole 25 Threaded member 25a Threaded portion 25b Mold inward end

Pc Concrete placing pressure (tensile stress) of side wall 3b
Ps External pressure (compressive stress) at the time of prestressing of side wall 3b
S: Stud weld W: Gap between steel permanent form 4b and temporary form 12 C: Concrete PC Prestressed concrete L: Gap in columnar member 11

Claims (4)

a steel plate, a bar-shaped steel member which is expanded by providing a flange at a first end thereof and serves as a spacer for prestressed concrete to which a temporary formwork is connected to a second end on the opposite side; A columnar member having an inner diameter larger than that of a first end, and having an end face having an insertion hole having a diameter smaller than that of said first end and through which said steel bar is inserted so as to be horizontally movable in its axial direction . A columnar member having one end inside thereof, and a cushioning material covering a portion of the columnar member and the steel plate facing the prestressed concrete ,
Inside the cylindrical member, the gap between the end face of the first end flange of the bar-shaped steel material and the inner surface side of the steel plate or the end portion of the stud provided on the inner surface side of the steel plate in the inward direction of the mold is formed by a press. It is a length that can absorb the displacement toward the center of the cylinder due to the application of stress force.
Structures for prestressed concrete. The cylindrical member is fixed to the steel plate by welding,
A stopper portion is provided on the end surface to abut against the collar portion of the steel bar and lock the steel bar in a retaining state,
The rod-shaped steel material is axially inserted into the fitting hole of the cylindrical member into which the collar part is fitted so that the collar part of the first end of the rod-shaped steel material abuts the stopper part of the cylindrical member. to be slidable in
The structure for prestressed concrete according to claim 1. said cylindrical member is internally threaded and engages with said thread a stud fixed to said steel plate ;
A stopper portion is provided on the end surface to abut against the collar portion of the steel bar and lock the steel bar in a retaining state,
The rod-shaped steel material is axially inserted into the fitting hole of the cylindrical member into which the collar part is fitted so that the collar part of the first end of the rod-shaped steel material abuts the stopper part of the cylindrical member. to be slidable in
The structure for prestressed concrete according to claim 1. Inside the cylindrical member, at a position that can be installed in the gap and is in contact with the first end of the steel bar, a prestressing force is applied to the steel plate to exert a force toward the center of the cylinder. 4. The structure for prestressed concrete according to any one of claims 1 to 3, further comprising a cushioning material that absorbs displacement .

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