JP3259888B2 - Reinforcement tensioning jig for forming precast concrete products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary jig for reinforcing steel bars for molding precast concrete products. In this reinforcing bar tension assisting jig, a plurality of reinforcing bars formed by arranging a plurality of reinforcing bars at intervals in the circumferential direction are arranged at intervals in the axial direction within one cylindrical form, and The rebars of the rebar cage are subjected to a tensile force to embed the rebars in the concrete, whereby the rebars are placed within the spacing when forming a prestressed concrete product such as a concrete pile.

[0002]

2. Description of the Related Art When a plurality of prestressed concrete products are simultaneously molded in one cylindrical form, the reinforcing bars of the reinforcing bars included in two adjacent prestressed concrete products are connected to each other. A form-supporting metal fitting capable of simultaneously applying a pulling force to the reinforcing bars of two reinforcing bars has been proposed.
-20330 publication). This formwork auxiliary fitting has a joint ring disposed in the formwork having a flange projecting radially inward at both ends, and one side of the joint ring connected to a reinforcing bar of the reinforcing bar cage on one side. And a plate connected to the reinforcing bar of the rebar cage on the other side and mounted on the other brim of the joint ring.

[0003] For example, when two prestressed concrete products are molded at the same time, prior to the molding,
Fixing one end of a first rebar cage of the two rebar cages to one end of a formwork, and connecting the other end of the first rebar cage to the formwork auxiliary fitting; Further, one end of a second rebar cage of the two rebar cages is connected to the formwork auxiliary metal fitting, and the other end of the second rebar cage is at the other end of the formwork. It is connected to a tension plate and a tension load is applied by the tension plate. The tension load is transmitted from the second rebar cage to the first rebar cage via the formwork fitting. As a result, the individual loads are distributed to the plurality of reinforcing bars of each reinforcing cage, and the individual reinforcing bars are tensioned. In this state, concrete is put into a mold and molded, and then cured to produce a prestressed concrete product.

[0004]

During the molding, a load of 20 to 670 tons is applied to the tension plate. For this reason, the joint ring 10 of the formwork auxiliary fitting may be deformed so as to be curved outward in the radial direction around the neutral point N of the joint ring 10 as shown by a virtual line in FIG. If the two flanges 11 and 12 become too wide due to this deformation, the vicinity of the base of the collar of the joint ring 10 is plastically deformed or broken, and it becomes difficult to introduce a stable prestress, and the joint ring 10 is re-installed. It cannot be used.

An object of the present invention is to provide a reinforcing steel tensioning jig for forming a precast concrete product, which can prevent plastic deformation and destruction of the joint ring without increasing the strength of the joint ring and thereby can introduce a stable prestress. To provide.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a plurality of reinforcing bars each having a plurality of reinforcing bars arranged at intervals in the circumferential direction are arranged at intervals in the axial direction within one cylindrical form. A reinforcing ring tension assisting jig disposed within the installation interval when the reinforcing rod cage is buried in concrete to form a prestressed concrete product, the joint ring; a first plate; And a plate. The joint ring having a cylindrical shape as a whole, which is arranged in the mold, is formed by joining a plurality of arc-shaped sections in a circumferential direction. Each section has first and second flanges projecting radially inward at both ends in the axial direction, and the opposing surfaces of the first and second collars are respectively inclined surfaces. The flange is formed as an inclined surface that is inclined so as to approach the flanges facing each other as the distance from the outer periphery of the collar toward the inside increases. The first plate is an annular plate connected to the plurality of rebars of the rebar cage on one side of the installation interval, and has an inclined surface closely contacting the inclined surface of the first flange of the joint ring. And is hung on the first collar. The second plate is an annular plate connected to the plurality of rebars of the rebar cage on the other side of the installation interval, and has an inclined surface closely contacting the inclined surface of the second flange of the joint ring. And is hung on the second collar.

[0007]

When a load is applied to the joint ring of the reinforcing-bar tension assisting jig from the tension plate outside the invention through the reinforcing bar of the reinforcing-bar cage on one side and the first plate, the first and second flanges of the joint ring are used. Has a specially shaped inclined surface, so that the load component that deforms the joint ring outward is reduced, and the bending moment is eventually reduced.

[0008] Since the flange of the joint ring has a sloping surface for hanging a plate connected to a plurality of reinforcing bars of each reinforcing cage, a bending moment acting on the joint ring is reduced, and plastic deformation or breakage of the brim is prevented. Can be. In addition, since the plate has the inclined surface that is in close contact with the inclined surface, the load is uniformly transmitted from the joint ring to the plate, so that a stable prestress can be introduced into the reinforcing bar.

It is possible to prevent the plastic deformation of the joint ring of the reinforcing-bar tensioning jig simply by providing the joint ring with a specially shaped inclined surface without increasing the strength or changing the material of the joint ring.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 showing a detailed cross section and FIG. 5 showing an entire cross section, a reinforcing bar tension assisting jig 20 has a reinforcing cage 2 in which a plurality of reinforcing bars 22 are arranged at intervals in a circumferential direction.
A plurality of the reinforcing steel cages 24, 2 are arranged at an installation interval 30 in the axial direction within one cylindrical formwork 28,
6 is disposed in the installation interval 30 when the prestressed concrete product is formed by embedding the concrete 6 in the concrete 32, and includes a joint ring 34, a first plate 36, and a second plate 38.

The reinforcing bars 24 and 26 are of a shape known per se suitable for the prestressed concrete product to be formed. A required number of reinforcing bars 22 such as PC steel bars are circumferentially equally spaced. They are arranged and formed. In the illustrated embodiment, each end of the plurality of rebars 22 of the rebar cages 24, 26 is caulked to an annular joint plate 40.

The formwork 28 is a cylindrical body having a length such that a plurality of, for example, two rebar cages 24, 26 can be arranged in the axial direction at an installation interval 30 for the rebar tension assisting jig 10. The formwork 28 can be formed by a single cylinder or, for example, two semi-cylindrical bodies can be circumferentially fitted and flanged together at the mating surface to form a cylindrical body. The formwork 28 has a plurality of tires 42 spaced apart in the axial direction of the outer periphery. These tires 42 are placed on rollers (not shown), and one of the rollers is driven to form the mold 2.
8 is rotated and formed by centrifugal force.

The joint ring 34 is slidably disposed in the formwork 28, has a cylindrical shape as a whole, and is formed by joining a plurality of sections in the circumferential direction. In the embodiment shown, the joint ring 34 consists of two semi-cylindrical sections 44 extending 180 ° in the circumferential direction, and these sections 44 are formed in a cylindrical shape so as to fit in the circumferential direction. Joint ring 34
Can be formed in a plurality of sections, such as three sections extending 120 degrees circumferentially, or four sections extending 90 degrees circumferentially.

The two sections 44 of the joint ring 34 are aligned with the axis of the joint ring 34 or the formwork 28.
Has the same shape in a cross section cut along a virtual plane including the axis C (FIG. 5). Referring to FIG. 2 showing an enlarged cross section,
The section 44 has a first flange 46 and a second flange 48 projecting radially inward A, respectively, at both axial ends. The surface 47 of the first collar 46 facing the second collar 48 is an inclined surface which is inclined so as to approach the second collar 48 as the distance from the outer periphery of the first collar 46 to the inside A increases. It is formed as. On the other hand, the surface 49 of the second collar 48 facing the first collar 46 is an inclined surface and is inclined so as to approach the first collar 46 as the distance from the outer periphery of the second collar 48 to the inside A increases. It is formed as an inclined surface. As a result, the surfaces 47 and 49 have a tapered shape toward the inside A in a cross section taken along a virtual plane including the axis of the joint ring 34.

The inclination angle of the surface 47 with respect to the imaginary vertical plane P orthogonal to the axis C and the inclination angle of the surface 49 with respect to the imaginary vertical plane P have the same magnitude θ in which the inclination directions are different. The magnitude of the inclination angle θ can be determined with reference to a vector diagram described later.

The first plate 36 is an annular plate connected to the plurality of reinforcing bars 22 of the reinforcing bar cage 24 on one side of the installation interval 30. As shown in detail in FIG. 3, the first plate 36 is provided with a first collar 46 of the joint ring 34.
And has a slope 37 that is in close contact with the slope 47 of the first member. That is, the inclined surface 37 provided on the flange of the first plate 36 is inclined at an inclination angle θ with respect to the virtual vertical plane P.

In the embodiment shown, the first plate 36
Has a plurality of through holes 52 equally spaced in the circumferential direction. On the other hand, the joint plate 40 of the reinforcing cage 24 is shown in FIG.
As shown in FIG. 7, a plurality of screw holes 54 having the same pitch as the through holes 52 are provided between the reinforcing bars 22 located adjacent to each other. First
When the first plate 36 is screwed into the screw hole 54 through the bolt 56 through the through hole 52 of the plate 36, the first plate 36 is connected to the joint plate 40, and is connected to the reinforcing bar 22 via the joint plate 40.

The second plate 38 is an annular plate connected to the plurality of reinforcing bars 22 of the reinforcing bar cage 26 on the other side of the installation interval 40, and is in close contact with the inclined surface 49 of the second flange 48 of the joint ring 34. And has a slant surface 39 which is hung on the second collar 48. The inclined surface 39 is inclined at an inclination angle θ with respect to the virtual vertical plane, similarly to the inclined surface 37 shown in FIG. The connection structure between the second plate 38 and the reinforcing bar 22 is the same as the connection structure between the first plate 36 and the reinforcing bar 22.

A first plate 36 and a second plate 38
The sealing material 58 is attached to the surfaces facing each other, and the two are brought into contact with each other, and the joint ring 34 is brought radially outward and pushed inward. Then, the pawl 46 of the joint ring 34 is attached to the inclined surface 37 of the first plate 36.
In addition, the pawl 48 is hooked on the inclined surface 39 of the second plate 38, and the joint ring 34 is connected to the first and second plates 36, 38.

As shown in FIG. 5, a base 60 is detachably attached to one end of the mold frame 28. Base 6
A through-hole is formed in the center of 0, and the tension bar 62 is passed through the through-hole. A shoulder is formed on the outer periphery of the base 60, and the shoulder is fitted to the end plate 64 of the mold frame 28, thereby preventing the base 60 from moving in the radial direction. An external thread is provided at a portion of the tension bar 62 protruding from the base 60 to the outside. A nut 66 is screwed into this external screw.

The tension bar 62 extends into the formwork 28,
It is connected to a substantially circular tension plate 68. A joint ring 70 is hung on the tension plate 68 and the annular plate 72. The joint ring 70 is composed of a plurality of sections like the joint ring 34 of the reinforcing-bar tension assisting jig 20, and each section has two claws, and the opposing surfaces of these claws are aligned with the axis C of the formwork 28. It is an orthogonal plane that is orthogonal. The plate 72 is connected to the reinforcing bar 22 via the joint plate 40 at the end of the reinforcing bar cage 26, similarly to the plate 36 of the reinforcing bar tension assisting jig 20.

An annular fixing plate 74 is detachably attached to the other end of the formwork 28. The fixing plate 74 includes a tension plate 68, the reinforcing bar 22 of the reinforcing bar cage 26, and the reinforcing bar tension assisting jig 2.
0 and the reaction force of the load applied through the reinforcing bar 22 of the reinforcing bar cage 24. In the illustrated embodiment, the fixing plate 74 has a plurality of bolt holes on the outer peripheral portion, and bolts 76 passed through these bolt holes are screwed into end plates 78 of the form and attached to the form 28. The joint plate 40 of the rebar cage 24 is connected to the inside of the fixing plate 74 in the radial direction of the bolt hole by the same structure as described above.

In using the reinforcing bar tension assisting jig 20,
The first plate 36 of the reinforcing bar tension assisting jig 20 is connected to the reinforcing bar 22 of the reinforcing bar cage 24 on one side, and the second plate 3
8 and the reinforcing bar of the reinforcing bar cage 26 on the other side. Then, the claws 46, 48 of the joint ring 34 are wound around the inclined surfaces of the plates 36, 38, respectively, and the two rebar cages 24, 26 are connected via the rebar tension assisting jig 20,
Rebar basket 26, rebar tension assisting jig 20, and rebar basket 2
4 are inserted into the mold 28 in this order. Then, the tension bar 62 projects from the base 60 to the outside, and the nut 66 is screwed into the outer screw. On the other hand, the fixing plate 74 and the joint plate 40 of the reinforcing cage 24 are connected, and the fixing plate 74 is fixed to the end plate 78 of the mold.

The nut 66 is screwed into the tension bar 6
When the tension plate 68 is pulled through the reinforcing member 2, the tensile load is applied to the reinforcing bar 22 of the reinforcing bar cage 26, the reinforcing bar tension assisting jig 20, and the reinforcing bar 22 of the reinforcing bar cage 24. Thus, preparation for molding is completed. The concrete 32 is formed by a method known per se, for example, a centrifugal force forming method, while holding the reinforcing bars 22 of the respective reinforcing bars in a state where a tensile load is applied. At the time of release after molding, the joint plate 40
Loosen the bolts fixing the fixing plate 74 and the fixing plate 74 to fix the fixing plate 7
Remove 4 and introduce stress into the concrete product.

The joint ring 34 of the reinforcing bar tension assisting jig 20 applies a tensile load from the tension plate 68 to the reinforcing bar cage 26.
This load is transmitted to the reinforcing bar 22 of the reinforcing bar cage 24, but the reinforcing bar 22 of the reinforcing bar cage 24 is fixed to the formwork 28 by the fixing plate 74. Receives the reaction force of the load. This and
Since the joint ring 34 is loaded by the two inwardly projecting collars 46, 48, the joint ring is eventually loaded by the load, as shown by phantom lines in FIG. Around the point, that is, the neutral point N, one half is clockwise, and the other half is counterclockwise, so as to be curved outward in the radial direction.

When a load F is applied to the joint ring 34, as shown in FIG.
A half of the joint ring 34 is deformed by a bending moment M = FL given by a product of the vertical distance L from to the neutral point N and the load F. A straight line DE is drawn from the tip of the load F in parallel to a straight line BN connecting the point of action B and the neutral point N, and a perpendicular line is drawn down from the point of action B to the straight line DE. It becomes ₁ . Therefore, the bending moment M is equal to the bending moment M ₁ = F ₁ L ₁ given by the product of the actual distance L ₁ from the point of action B to the neutral point N and the component force F ₁ . Here, when theta ₁ a <BDE, a F ₁ = Fsinθ _1.

As shown in FIGS. 6A and 6B, the inclined surface 47 of the collar 46 (the analysis is the same for the other collar).
Is inclined at an inclination angle θ ₂ with respect to a virtual vertical plane P orthogonal to the axis of the joint ring, a component F ₂ due to the load F is generated on the inclined plane 47. Since this component force acting to push the inclined surface 47 radially inward, the component force F ₁ is reversed, the size is a F ₂ = Fsinθ _2. The angle θ ₃ between the inclined surface 47 and the direction of the component force F ₁
Is (θ ₁ −θ ₂ ), the component F ₃ of the component F _{2 in} the direction of the component F ₁ is: F ₃ = F ₂ cos (θ ₁ −θ ₂ ) = F sin θ ₂ cos (θ ₁ − θ ₂ ).

Therefore, the collar 46 of the joint ring
Result of providing the inclined surface 47, deforming the joint ring, the component force f of the outward force F becomes _{f = F 1 -F 3 = Fsinθ} 1 -Fsinθ 2 cos (θ 1 -θ 2). The value of the second term in the equation is positive, the component force f in the case where there is the inclined surface is smaller than the component force F ₁ in the absence of the inclined surface. Therefore, the bending moment fL ₁ when there is an inclined surface is the bending moment F L when there is no inclined surface.
₁ L Less than ₁ . Thereby, deformation of the joint ring can be prevented, and plastic deformation of the collar 46 can be prevented.

Θ ₁ in the equation is fixed when the length of the joint ring 34 is determined. On the other hand, the inclination angle θ
₂ is a variable having an arbitrary value. Therefore, the second term in the formula is a arbitrary value depending on the size of the inclination angle theta _2. Differentiating this second term with respect to the inclination angle θ ₂ and applying the condition that the value of the second term is maximal, 2θ ₂ −θ ₁ = π / 2 is obtained. Therefore, the inclination angle θ _{2 is set} to (π / 4 + θ ₁
/ 2), the component force f given by the equation is minimized, and the deformation of the joint ring can be minimized.

In the above embodiment, one rebar tension assisting jig 20 and two rebar cages 24 and 26 are used.
Instead, a plurality of rebar tension assisting jigs 20 and one more rebar cage can be used.

For example, if θ ₁ = 13 ° and θ ₂ = 5 °, f = 0.139 F is obtained from the equation. On the other hand, when the inclination angle θ ₂ = 0 ° as in the conventional case, f ′ = 0.225
F. In the end, in the example in which the inclination angle θ ₂ = 5 °, f is reduced by about 38%. The reduction in the component force f means that a correspondingly large tensile load can be applied. Therefore, it is possible to introduce a large prestress into the reinforcing steel without forming a joint ring with, for example, high-tensile steel.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of a reinforcing bar tension assisting jig according to the present invention, which is cut along a plane including an axis, and shows an enlarged portion of FIG.

FIG. 2 is an enlarged cross-sectional view of a section of a joint ring used in the reinforcing bar tension assisting jig shown in FIG.

FIG. 3 is an enlarged sectional view showing a part of a joint ring and a plate of the reinforcing bar tension assisting jig shown in FIG. 1;

FIG. 4 is a front view showing a part of a joint plate provided at an end of the reinforcing cage.

FIG. 5 is a cross-sectional view of a form incorporating the reinforcing bar tension assisting jig according to the present invention, taken along a plane including an axis.

FIGS. 6A and 6B are schematic views showing the operation of the reinforcing bar tension assisting jig according to the present invention, wherein FIG. 6A shows the entirety, and FIG.

FIG. 7 is a schematic view showing deformation occurring in a conventional joint ring.

[Explanation of symbols]

 Reference Signs List 20 Reinforcement tension assisting jig 22 Reinforcing bar 24, 26 Reinforcing cage 26 Joint ring 28 Formwork 30 Setting interval 34 Joint ring 36 First plate 38 Second plate 40 Joint plate 46, 48 Pawl 37, 39, 47, 49 Incline surface

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 48-97458 (JP, U) JP-A 58-76712 (JP, U) JP-A 56-555618 (JP, U) 10173 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B28B 23/00-23/22 B28B 21/00-21/98

Claims (1)

(57) [Claims] 1. A plurality of rebar cages in which a plurality of rebars are arranged at intervals in the circumferential direction are arranged at intervals in the axial direction in one cylindrical form, and each of the rebar cages is arranged. A reinforcing bar tension assisting jig disposed within the installation interval when embedding in a concrete to form a prestressed concrete product, wherein the joint ring has a cylindrical shape as a whole and is disposed in the formwork. Are formed in the circumferential direction so that each section has a first flange and a second flange protruding inward in the radial direction at both ends in the axial direction. The opposite faces of the two collars are
Joint rings formed as inclined surfaces which are inclined surfaces and which are inclined so as to approach the flanges facing each other as they move inward from the outer periphery of the collar, and the plurality of reinforcing bars in one side of the installation interval. An annular first plate connected to a reinforcing bar, the first plate having an inclined surface closely contacting the inclined surface of the first collar of the joint ring, the first plate being hung on the first collar; An annular second plate connected to the plurality of rebars of the rebar cage on the other side of the installation interval, the plate having an inclined surface closely contacting the inclined surface of the second flange of the joint ring; A second reinforcing plate for forming a precast concrete product, comprising: a second plate that is hung on a second brim.