JP2008025248A - Plastic hinge structure of concrete structure and manufacturing method of precast formwork - Google Patents

Abstract

In a plastic hinge structure of a concrete structure using a precast form made of ultra-high strength fiber reinforced concrete or mortar, precast form that facilitates formation of crack-inducing joints in the precast form and encloses a rebar such as a band rebar. By providing formwork, structural performance such as pier structure, workability, and long-term durability will be improved.
High strength fiber reinforced concrete or mortar is continuously introduced in the circumferential direction of the manufacturing formwork during the manufacture of the precast formwork 4 to be grounded to the plastic hinge section, and is divided and placed in multiple layers. In the circumferential direction, the fibers are continuously arranged, but the crack-inducing joints 10 in which the fibers are not continuous are formed on the joining surfaces of the respective layers, and the crack-inducing joints 10 are vertically spaced in one precast mold 4. In this way, a plurality of them are formed to improve manufacturability and workability, and the long-term durability is improved by the integrally formed crack induction joint.
[Selection] Figure 1

Description

  The present invention relates to a plastic hinge structure of an RC structure having high earthquake resistance and workability, and a method for producing a precast formwork used therefor. For example, the present invention is effectively applied to a pier having a single-column RC structure, a pier having an RC rigid frame structure, and a middle column head and a column base provided in the center of an RC underground structure.

  For example, in a single-column RC structure pier as shown in FIG. 8, damage concentrates on the pier base during a large earthquake, and a so-called plastic hinge section is formed. The seismic resistance of the pier structure as a whole depends greatly on this plastic hinge. As a cause of damage to various piers observed in the 1995 Hyogoken-Nanbu Earthquake, it has been pointed out that large bending deformation concentrated in the plastic hinge section, and its size exceeded the performance of RC members. For this reason, in order to improve the earthquake resistance of the RC structure, it is indispensable to improve the earthquake resistance of the plastic hinge portion where bending deformation concentrates during an earthquake.

  In recent years, RC structures using fibers as reinforcing materials have been developed as structural types with improved seismic performance. For example, Patent Document 1 discloses a concrete structure including a precast concrete member formed by mixing reinforcing short fibers and concrete cast using the precast concrete member as a mold.

  The invention of Japanese Patent Application No. 2005-189247, which is a further development of such a structure, has a high compressive strength by applying a precast form made of ultrahigh strength fiber reinforced mortar to the plastic hinge part of the RC structure. By restraining the inside with a material having a tensile strength, the core concrete is crushed and the main rebar buckling is suppressed to achieve high deformation performance. In the present invention, the shape of the precast formwork is pursued economically by making it a shape that can improve the seismic performance of the RC structure while minimizing the amount of ultra-high strength fiber reinforced mortar used. .

  However, the ultra high strength fiber reinforced mortar has a higher tensile strength than ordinary concrete due to fiber mixing. Therefore, when the mold is integrated only in the plastic hinge section, the mold has a relatively small tensile strength. There is a high possibility that bending deformation concentrates on the joint between the steel and the member made of ordinary concrete, and the mold does not function as a plastic hinge. Therefore, by adjusting the height per piece of precast formwork in the plastic hinge section and not mixing fibers, a joint part with a reduced tensile strength to the size of ordinary concrete is provided, and a structure consisting of multiple precast formwork (See FIG. 8), the cracks are surely dispersed in the plastic hinge section to be induced.

The following technical elements are disclosed with respect to the crack-inducing joint portion.
(1) As shown in FIG. 9A, in the plastic hinge structure 90 including a plurality of precast molds 91, the plastic hinge structure 90 has the same compressive strength as the high-strength material constituting the precast molds 91, and fibers are mixed. By using unmodified mortar as joint mortar, rubber or silicon, etc., the water-stopping property is improved and the durability is improved.

(2) When the cross section of the plastic hinge section is small and workability is better with a single precast formwork, cut it on the surface or inside of the precast formwork 91 as shown in FIG. 9 (b). By providing the notch 92, the occurrence of cracks is induced.

Japanese Patent Laid-Open No. 10-147976

  In the case of the conventional crack induction joint shown in FIG. 9 described above, there are the following problems.

  (1) Providing a large number of joints as shown in FIG. 9 (a) requires a large number of precast molds to be installed, and the operations such as production and installation are complicated. In addition, mortar, rubber, silicon, and the like used for joint treatment have a long-term durability that is inferior to concrete, and there is a concern about the durability of steel materials (band reinforcing bars and axial reinforcing bars) inside the pier.

  (2) The notch provided in the precast form shown in FIG. 9 (b) is susceptible to stress concentration and cannot fully utilize the high strength characteristics of the ultra high strength fiber reinforced mortar.

  (3) In either case, it was impossible to enclose the band reinforcement. As a precast formwork containing a reinforcing bar, there is already a track record in a pillar and a beam member of an architectural building. However, in the process of manufacturing a precast formwork of ultra-high strength fiber reinforced mortar, it is necessary to perform heat curing. At that time, the concrete itself shrinks by about 450μm, so if the reinforcing bars are contained, the reinforcing bars restrain the shrinkage. However, cracks occur and compressive stress is generated in the reinforcing bars. For this reason, a structure in which reinforcing bars are encapsulated using ultra-high-strength fiber mortar is impossible. If it becomes possible to enclose the band rebar, the workability of the pier base can be improved.

  The present invention facilitates the formation of crack-inducing joints in a precast formwork in a plastic hinge structure of a concrete structure using a precast formwork made of ultrahigh-strength fiber reinforced concrete or mortar. By providing a precast formwork to be included, structural performance such as a pier structure, workability, and long-term durability are improved.

  The invention according to claim 1 of the present invention is a plastic hinge structure of a concrete structure composed of a precast mold made of high-strength fiber reinforced concrete or mortar and concrete cast in the precast mold, and the precast By placing the high-strength fiber reinforced concrete or mortar in multiple layers in the formwork for manufacturing the formwork, joints in which the fibers do not continue vertically are formed on the joint surface, and the precast formwork depends on the joints. It is a plastic hinge structure of a concrete structure characterized in that a crack induction joint is formed integrally.

High-strength fiber reinforced concrete or mortar is a material in which steel fiber, carbon fiber, glass fiber, or the like is mixed in concrete or mortar with high compressive strength, and has a compressive strength of 100 to 250 N / mm ² and a bending tensile strength of 10 ~40 N / mm ^2, ultra high strength fiber reinforced concrete or mortar tensile strength cracking is 5 to 15 N / mm ² is preferred. By using a material with high compressive strength and tensile strength for the precast formwork in the plastic hinge section and constraining the inside, it is possible to suppress the collapse of the core concrete and the buckling of the main rebar and achieve high deformation performance it can.

  In the first aspect of the present invention, for example, as shown in FIG. 1, the precast formwork of the plastic hinge section is integrally formed without being divided as in the prior art. Fiber reinforced concrete or mortar is continuously introduced in the circumferential direction of the manufacturing formwork, and divided into multiple layers, and the fibers are continuously arranged in the circumferential direction. In this case, crack-inducing joints in which fibers are not continuous are formed, and a plurality of crack-inducing joints are formed at intervals in the vertical direction in one precast mold. Cracks are easily generated by this crack-inducing joint. In the state where the bridge pier is not bent during an earthquake or the like, cracks do not occur and the cracks close after a small and medium-scale earthquake, so that long-term durability can be ensured while no joint treatment is required. One precast mold can be large in size and weight that can be transported or lifted in construction, and a plastic hinge section is formed by one or a plurality of precast molds.

  According to a second aspect of the present invention, in the plastic hinge structure according to the first aspect, an uncured delayed thermosetting resin is applied to the reinforcing bar and placed in a manufacturing formwork, and the high strength fiber reinforced concrete or It is a plastic hinge structure of a concrete structure characterized in that a reinforcing steel in which a delayed thermosetting resin is cured after heat curing is encased in a precast mold by placing mortar and heat curing.

  This is a case where high strength fiber reinforced concrete or mortar precast formwork, which has been impossible due to heat curing, is used to enclose strip reinforcing bars and axial reinforcing bars, and has delayed hardening properties used in pregrout PC steel As the resin hardens after heat curing, the rebar does not inhibit the contraction of concrete or mortar, and the rebar does not generate compressive stress. By making it unnecessary, the workability is improved.

  The invention according to claim 3 of the present invention is composed of a precast form made of high-strength fiber reinforced concrete or mortar and concrete placed in the precast form, and the precast form is a plurality of precast form blocks This is a plastic hinge structure of a concrete structure constructed by laminating steel bars. Reinforcing bar storage grooves are installed in the reinforcing bar storage grooves provided in advance at the joints of precast formwork blocks that have been self-shrinked during production. Reinforcing bars are included in the precast formwork by filling the voids with high-strength grout material without fibers and joining the precast formwork blocks with the high-strength grout material placed on the joint surface. And the concrete by which the crack induction joint by the said high intensity | strength grout material is formed A plastic hinge structure forming body.

  For example, as shown in Fig. 7, the precast formwork is divided into a plurality of precast formwork blocks with a small height, and the crack reinforcement induction joint is formed at the same time as the band rebar is included, and the precast formwork block is manufactured. After the secondary curing after self-shrinking is completed, band rebars and axial rebars are installed in the grooves, and precast molds are made with high-strength grout materials (high-strength grout materials, mortar, resin, etc.) that are not mixed with fibers. By integrating, the rebar does not obstruct the contraction of concrete or mortar, and the rebar does not generate compressive stress. Thus, workability is improved. At this time, by joining and integrating the precast formwork blocks with the high-strength grout material, a crack-inducing joint that has long-term durability and can induce the occurrence of bending cracks during an earthquake is formed. .

  The invention according to claim 4 of the present invention is the plastic hinge structure according to any one of claims 1 to 3, wherein the neutral axis position in the final state with respect to bending is a boundary between the precast formwork and the internal concrete. It is a plastic hinge structure of a concrete structure characterized by being positioned.

  For example, as shown in FIG. 4, if the thickness of the precast formwork is set to a thickness that can bear the yield load and the axial compression force of all the axial rebars, it will not be compressed and destroyed. It can be a pier structure. As shown in FIGS. 4D and 4E, the thickness of the precast mold is matched with the thickness of the compression region, and the axial reinforcing bars are arranged on the inner surface of the precast mold, that is, the neutral axis position. The thickness of the precast formwork in the final compression zone against bending is secured to ensure the necessary cover thickness for durability, and the cover of the precast formwork is encased in the compression zone. The effect of constraining internal concrete and axial rebars by bending in the lateral direction is improved.

  The invention according to claim 5 of the present invention is the precast mold in a plastic hinge structure of a concrete structure composed of a precast mold made of high-strength fiber reinforced concrete or mortar and concrete cast in the precast mold. A method for manufacturing a frame, in which a high-strength fiber reinforced concrete or mortar is cast in the circumferential direction of the mold frame in the mold for manufacturing the precast mold to form a first layer, and the same casting is performed 2 The production of a precast formwork is characterized by forming a joint in which fibers are not continuous vertically on the joining surface after the layer is formed, and producing a precast formwork integrally formed with a crack-inducing joint by the joint. Is the method.

  It is a manufacturing method of the precast formwork of Claim 1 or 2, for example, as shown in FIG. 2, high strength fiber reinforced mortars are poured into a manufacturing formwork from a discharge part using a pumping hose, for example. Let Stir the mortar with a stick or the like so that the fibers at the start and end positions are continuous. It is preferable that the starting position of the next layer is different from that of the lower layer. If necessary, band rebars are assembled inside the mold before placing. The position of the band reinforcing bar may be arbitrary, but in order to obtain the best restraining effect by the precast formwork, it is preferable to arrange the band reinforcing bar at a position slightly separated from the joining surface.

  The invention according to claim 6 of the present invention is the manufacturing method according to claim 5, wherein a wire mesh for preventing the fibers from continuing is laid on the joining surface. It is.

  If the joining surface of each layer is not agitated with the mortars of the lower layer, the fibers will not penetrate the joining surface and can form a crack-inducing joint, but in order to complete this, It is preferable to lay a suitable wire mesh or the like on the joining surface.

  The invention according to claim 7 of the present invention is composed of a precast form made of high-strength fiber reinforced concrete or mortar and concrete placed in the precast form, and the precast form is a plurality of precast form blocks A method for manufacturing the precast formwork in a plastic hinge structure of a concrete structure formed by laminating layers, wherein the precast formwork block is formed with a reinforcing bar housing groove at the time of manufacturing the precast formwork block, and the self-shrinkage is completed. Install reinforcing bars in the reinforcing bar storage grooves of the block, fill the gaps in the reinforcing bar storage grooves with high-strength grout material that is not mixed with fibers, and use the high-strength grout material placed on the joint surface to form the precast formwork blocks Joints, rebars are included, and crack-inducing joints are formed by the high-strength grout material A method for producing a precast mold, characterized in that the production of precast mold was.

  It is a method of manufacturing the split type precast formwork according to claim 3, for example, as shown in FIG. 7, a precast formwork in which a reinforcing bar is included and a crack induction joint is formed by the high-strength grout material. Can be manufactured. The high-strength grout material applied to the rebar storage grooves and joints is a material with the same elastic modulus as the material used for the precast formwork (for example, fiber removed from the material constituting the formwork) Etc.) is desirable.

Since the present invention is configured as described above, the following effects can be obtained.
(1) A high-strength fiber reinforced concrete or mortar is divided into multiple layers and placed in a precast formwork production form to form joints where the fibers do not continue vertically on the joint surface. Multiple crack-inducing joints can be easily formed in the precast formwork, and there is no need to install many precast formwork and perform joint treatment as before, greatly improving manufacturability and workability. The cost can be reduced, and the long-term durability is improved by the integrally formed crack induction joint.

(2) By applying uncured delayed thermosetting resin to the reinforcing bar and placing it in the manufacturing formwork, it is possible to enclose the reinforcing bar in the precast formwork on which crack-inducing joints are formed. Greatly improved.

(3) Reinforcing bars are installed in the reinforcing bar storage grooves of the precast formwork blocks that have been self-shrinked at the time of manufacture, and the high strength grout material that is not mixed with fibers is filled into the gaps of the reinforcing bar storage grooves. By joining the precast formwork blocks together with the material, the precast formwork can contain reinforcing bars and form crack-inducing joints with high-strength grout material. There is no need to perform joint processing by installing a large number of frames, which greatly improves manufacturability and workability, enables cost reduction, and improves long-term durability with the integrally formed crack induction joint. To do.

(4) The precast formwork as described above can be increased in size to a size and weight that can be transported or lifted for construction, further improving workability.

(5) By setting the neutral axis position in the ultimate state against bending as the boundary position between the precast formwork and internal concrete, there is no compression failure, so ideal plasticity with the precast formwork with the minimum thickness required A hinge structure is obtained. Moreover, the effect of constraining the internal concrete and the axial rebar by the bending in the lateral direction by the cover concrete of the precast formwork is improved by including the band rebar.

  Hereinafter, the present invention will be described based on the illustrated embodiments. This embodiment is an example applied to a single-column RC structure pier. FIG. 1 is a front view of a partial cross section of a bridge pier showing an example of an embodiment of a precast formwork in a plastic hinge structure according to the present invention. 2 is a perspective view, a vertical sectional view, a plan view, and a perspective view of a wire mesh showing an example of a method for manufacturing a precast mold in the plastic hinge structure of FIG.

  In FIG. 1, the column member 2 and footing 3 of the pier 1 are both constructed by RC structure, and a precast formwork 4 made of ultrahigh strength fiber reinforced concrete or mortar is installed in a plastic hinge section L at the base of the column member 2. The column member 2 other than the base is provided with a precast formwork 5 made of ordinary concrete. Each joint of these precast molds 4 and 5 is provided with a joint such as a concavo-convex joint that fits each other, and the integrity of the precast molds 4 and 5 is ensured. In these precast molds 4 and 5, ordinary concrete 6 is continuously placed. In addition, you may comprise the column members 2 other than a base from cast-in-place concrete like the construction method of the conventional RC member.

The ultra high strength fiber reinforced concrete or mortar of the precast form 4 is a material in which steel fiber, carbon fiber or glass fiber is mixed in concrete or mortar with high compressive strength, and the compressive strength is 100 to 250 N / mm. ^2. Refers to a material having a bending tensile strength of 10 to 40 N / mm ² and a tensile strength of 5 to 15 N / mm ² when cracking occurs. Conventionally, such a precast mold 4 is constituted by a plurality of precast mold blocks having a small height, and a joint part of each precast mold block is used as a crack-inducing joint having a low tensile strength, so that the plastic hinge section can be reliably obtained. In the present invention, as shown in FIG. 1, a crack-inducing joint 10 is integrally formed on the precast mold 4 by joints in which fibers do not continue vertically.

  When the direction of the load acting on the member is known, the reinforcing fiber of the ultra high strength fiber reinforced mortar deflects the fiber in a predetermined direction to maximize the reinforcing effect of the fiber in order to increase the strength and toughness in that direction. It is desirable to pull out. As a precast formwork for the pier base, it is necessary to constrain the concrete inside by restraining in the strength and toughness against compression, and in the circumferential direction, and to suppress the buckling of the axial rebar. At the same time, bending cracks need to be dispersed to cause cracks.

The precast mold is manufactured by pouring fiber-reinforced concrete into the mold from the discharge part. For example, the precast mold 4 of the present invention is manufactured by the following method (see FIG. 2).
(1) Assemble the manufacturing form 20 for the precast form. This formwork 20 is horizontally installed with a cross-section of a square shape, as in the case of being placed on a pier or the like. However, the top and bottom may be reversed. A predetermined rebar is disposed inside the mold 20 as necessary.

(2) The ultra high strength fiber reinforced mortar A is poured into the mold 20 from the discharge part through the pressure feeding hose 21, for example. At this time, the discharge part of the hose is moved in the circumferential direction of the mold (horizontal horizontal direction). After the first layer of the mortar A1 has been placed, the mortar is stirred with a stick or the like so that the reinforcing fibers at the placement start position and the finish position are continuous.

(3) Next, the second layer of mortar A2 is placed in the same procedure. At this time, the placement start position is preferably a position different from the first layer. After placing the second layer, the same operation is repeated until the end of the mold 20 is reached.

(4) In order to prevent the fibers from continuing to the joining surface of each layer, the fibers will not penetrate the joining surface unless they are stirred with the mortar of the lower layer. A joint where the fibers do not continue vertically is formed on the joining surface, and the crack induction joint 10 is integrally formed by the joint. In order to make this complete, an appropriate wire mesh 11 or the like may be laid on the joining surface.

  The thickness of one layer of placement can be adjusted by the amount of placement of one layer. The inner diameter of the hose or the discharge port may be arbitrary as long as the mortar and the fiber are not separated or blocked. Further, the joining surface does not need to be a smooth surface. Appropriate unevenness is preferred from the viewpoint of the shear strength of the joint surface when a shearing force acts on the pier or the like. In this sense, the wire mesh 11 or the like may be corrugated or tooth-shaped irregularities (see FIG. 2C). Further, in the drawing, the wave is uneven in one direction, but it may be two-dimensional uneven.

  In addition, in prior art JP-A-2002-47798 and JP-A-2002-47799, it is disclosed that fibers of fiber reinforced concrete are aligned in one direction, but in the present invention, a plurality of arbitrary positions are disclosed. The purpose is to prevent the fibers from continuing in the cross section, and the deflection of the reinforcing fibers in the mortar to be poured is not intended. Therefore, it is not necessary to provide a baffle plate in the mortar discharge part. For placement work, it is necessary to make the hose and the discharge part at the tip small enough to fit within the mold, but it is not necessary for the discharge part to taper in the discharge direction in order to deflect the fibers. .

  As described above, when the ultra-high-strength fiber reinforced mortar A is placed in the production of the precast mold 4, the mortar that has been kneaded is continuously introduced in the circumferential direction of the production mold 20, so that Although the fibers are continuously arranged, the cracks are easily generated because the fibers are not continuous on the joining surface with respect to the occurrence of bending cracks such as bridge piers. In the state where the pier is not bent such as during an earthquake, cracks do not occur, and after a small and medium-sized earthquake, the cracks close, so long-term durability can be ensured while joint treatment is unnecessary.

  FIG. 3 is a horizontal cross-sectional view showing an example in which a band rebar is included in a precast formwork. FIG. 4 is a vertical sectional view showing various arrangement positions of the band reinforcing bars in the precast formwork. As shown in FIG. 3, the band reinforcement 12 is included inside the precast mold 4 having the crack induction joint 10 manufactured as described above. If band rebars can be included, the workability of the pier base can be improved. Moreover, the intermediate strip rebar 13 is disposed as necessary. For example, as shown in FIG. 3, a divided intermediate strip 13 or a steel material that protrudes short in a connectable range is engaged with the strip rebar 12 and arranged so as to be opposed to the inside of the precast mold 4. In addition, after the curing of the precast mold 4 is completed, the lap joint, flare welding, mechanical joint and the like are connected by an appropriate method.

  As shown in FIG. 4, when the thickness of the precast form 4 is set to a thickness that can bear the yield load and the axial compression force of all the axial rebars, it will not be compressed and destroyed, so it is an ideal pier. It can be a structure or the like. When the thickness of the mold is less than the cover thickness (about 90 mm) with respect to a normal rebar, it will not be an ideal plastic hinge because it will be compressed and destroyed in the final bending state. The rebar 12 is arranged as close as possible to the outer edge of the precast mold 4 in the final compression zone with respect to the bending so that the cover thickness required for durability is secured. It is good to do.

  That is, as shown in FIG. 4 (a), when the thickness of the precast mold 4 is thinner than the cover thickness, the necessary compression area is insufficient and cannot be established. As shown in FIG. 4B, when the neutral axis position in the final bending state is the boundary position between the precast mold 4 and the internal concrete 6, it is ideal for the reason described later. As shown in FIG.4 (c), when the thickness of the precast formwork 4 is thicker than a neutral axis position, it becomes uneconomical and a weight increase. As shown in FIGS. 4D and 4E, by placing the rebar 12 inside the precast formwork 4, the restraining effect of the rebar 12 is improved, and the rebar is in the vicinity of the inner surface of the formwork. In contrast, the stress concentration around the belt reinforcing bar 12 can be relaxed, and the cover concrete of the precast formwork 4 restrains the internal concrete 6 and the axial reinforcing bar 14 by lateral bending. Therefore, it is more ideal that the neutral axis position in the final state is the boundary position between the precast formwork 4 and the internal concrete 6 and the band reinforcement 12 is included in the precast formwork 4. Moreover, if the band reinforcement 12 is included, the workability of the pier base will be improved.

By setting the neutral axis position in the final bending state as the boundary position between the precast mold 4 and the internal concrete 6, the following effects can be obtained.
(1) By setting the thickness of the ultra-high-strength fiber reinforced mortar, it is not necessary to bear the tensile force of the reinforcing bar located on the neutral axis, so the necessary thickness of the precast formwork 4 is made thicker than the neutral axis position. It can be made thinner than the case. For example, in the case where the axial rebars 14 are evenly arranged in the circumferential direction on the bridge piers having a square cross section, it is not necessary to consider the tensile force of the axial rebars 14 arranged along the neutral axis position. That will be 3/4. In the case of a double reinforcing bar arrangement like a wall pier, it can be reduced to 1/2.

(2) In the conventional structure, there is an axial rebar 14 in the compression region, and the cover concrete is peeled off due to buckling. On the other hand, in the structure of the present invention, when it receives a seismic load of positive and negative alternating, it turns into compression after tensile yielding, so it does not mean that it does not buckle, but the degree of buckling is reduced, such as peeling of cover concrete Damage can be reduced.

(3) As a result of the above (2), it is possible to omit or reduce the intermediate rebars necessary for the design.

  Next, it has been impossible in the past from the viewpoint of heat curing to enclose the rebar 12 in the precast mold 4 made of ultra-high-strength fiber reinforced mortar. By applying the resin and placing it in the manufacturing formwork 20 and performing mortar placement and heat curing, the rebar 12 can be included in the precast formwork 4 without inhibiting the shrinkage of the mortar. .

In heat curing of ultra-high strength fiber reinforced mortar, generally, a temperature history as shown in FIG. In this process, the shrinkage strain of the mortar reaches 450 × 10 ⁻⁶ as shown in FIG.

  Of the slow-curing resins used in pre-grout PC steel, etc., for the ultra-high temperature type resin, try to find the "cumulative hardening influence coefficient" that indicates the degree of hardening of the resin when subjected to the above temperature history . The cumulative hardening influence coefficient indicates that the tension of PC steel is possible. If this is 1.0 or less, the resin is uncured and can be tensioned. It shows that the adhesive strength of concrete hardens to a practically sufficient level.

  FIGS. 5C and 5D show the calculation results of the cumulative hardening influence coefficient (d is an enlarged view within the dotted line c). In this example, when standard heat curing is applied, the resin hardens for about one year after the precast formwork is cast, so that a precast formwork including a completely attached reinforcing bar is provided in about 2.3 years. The time for maintaining the maximum temperature of 90 ° C. is a time set until the necessary strength is developed, and is generally 48 hours.

  By slightly increasing the time to maintain the maximum temperature of 90 ° C, it is easy to shorten the period until the onset of adhesion strength, and Fig. 5 (e) shows the time to maintain the maximum temperature of 90 ° C. Is 84 hours. According to this, resin hardens | cures in about 100 days, and it becomes perfect adhesion in 230 days which is 2.3 times that. With such a required number of days, a standard pier such as a bridge can sufficiently cope with the time until the completion of the structure. It should be noted that the curing characteristics of the resin can be changed by adjusting the compounding of the resin, and may be dealt with accordingly.

  The mortar placing procedure in the production of the precast mold 4 is as described above, and the position of the joining surface and the band reinforcing bar 12 may be arbitrary. It is preferable to place the band reinforcing bar 12 at a position somewhat apart from the joint surface. When the occurrence interval of bending cracks to be set is larger than the height of one layer of casting, the mortar above and below the joint surface may be stirred and the reinforcing fibers may be cross-linked, but generally, the smaller the crack interval, Since the width of one crack is small and preferable in terms of durability, such necessity is low.

The coating thickness of the pre-grout resin (delay thermosetting resin) may be set from the amount of shrinkage strain of mortar (450 × 10 ⁻⁶ ). Several millimeters may be sufficient. If the length of one side of the precast formwork is 5000 mm at the long side of the pier cross section, in order not to constrain the shrinkage, it is assumed that the shrinkage is uniformly done from the center of 5000 mm, 0.5 × 5000 × 500 × 10 ⁻⁶ = 1.125mm of free space is sufficient. After assembling the reinforcing bars, pre-grout resin with a thickness of 1.125 mm or more is applied to the surface of the reinforcing bars, mortar is placed before curing, and curing is performed after heat curing. Can be manufactured.

  Moreover, when considering the contraction in the axial direction of the reinforcing bars to be included, the coating thickness of the pre-grouting resin may be about the height of the transverse nodes (see FIG. 6) of the deformed reinforcing bars. Since the deformed reinforcing bar used for the normal band reinforcing bar is about D16 to D25, the height of the node is about 2 mm at most. In addition, the uncured viscosity of the pre-grout resin is about the same as that of normal grease, and the coating thickness can be maintained without any practical problem if no special vibration is applied after coating.

  Next, FIG. 7 is a perspective view / vertical sectional view showing another embodiment of the precast mold in the plastic hinge structure of the present invention and an example of the manufacturing method thereof. This embodiment is another means for dividing a precast formwork into a plurality of precast formwork blocks having a small height to enclose the rebar and at the same time forming a crack-inducing joint. Manufacturing formwork.

  (1) First, a precast formwork block 30 having a square shape in a square shape is manufactured with an ultra-high-strength fiber reinforced mortar, a secondary curing is performed, and self-shrinkage is terminated. The formwork block 30 is formed in advance with a reinforcing bar housing groove 31 having a square shape in plan view and an U-shaped cross section that opens to the upper surface, which is a joint surface. Further, by providing a notch 32 penetrating the inside of the mold block 30 and the reinforcing bar housing groove 31, the intermediate band reinforcing bar 13 can be included inside the precast mold 4.

  (2) After the secondary curing in which self-shrinking is completed, the band reinforcing bar 12 is disposed in the reinforcing bar storage groove 31, and a high-strength grout material 33 in which fibers are not mixed in the voids of the reinforcing bar storage groove 31, for example, high-strength grout, Then, resin or the like is filled, and the precast form block 30 and the band reinforcement 12 are integrated. Thereby, the band reinforcement 12 can be included in the precast formwork 4 while preventing the reinforcement of the reinforcement due to the self-contraction of the ultra high strength fiber reinforced mortar and the occurrence of cracks.

  (3) At the same time, a high-strength grout material 33 is laid thinly up to the joint surface of the precast formwork block 30, and the precast formwork block 30 containing another rebar 12 is overlapped and joined between the blocks. The crack-inducing joint 10 that is highly durable and that generates cracks during an earthquake of medium or larger scale can be formed.

  The high-strength grout material 33 applied to the reinforcing-bar storing groove 31 and the joint portion is made of a material having an elastic modulus comparable to the material used for the precast mold 4 (for example, from the material constituting the mold). It is desirable to use those from which fibers have been removed.

  In the above description, the reinforcing bars to be included are described as being limited to band reinforcing bars, but axial reinforcing bars may be included. In this case, it is necessary to connect the axial rebars by mechanical joints or the like at the precast mold joint positions, but there is an advantage that assembly of the rebars at the site can be omitted. Further, in the figure, a column member having a rectangular cross section is shown as an example, but a circular cross section or the like such as a pile head may be used. When applied to piles, it can also be used as a standpipe for excavation work, and there is an advantage that it becomes unnecessary to pull out the standpipe after construction.

It is a partial front view of the bridge pier which shows an example of the embodiment of the precast formwork in the plastic hinge structure concerning the present invention. FIG. 1A is a perspective view and a vertical sectional view showing an example of a method for manufacturing a precast mold in the plastic hinge structure of FIG. 1, FIG. 2B is a plan view and a vertical sectional view, and FIG. It is a horizontal sectional view which shows the example which encloses a band reinforcement in the precast formwork of this invention. It is a vertical sectional view showing various arrangement positions of the band reinforcement in the precast formwork. (A) is a graph showing the standard heat curing conditions of ultra high strength fiber reinforced concrete, (b) is a graph showing shrinkage strain before placing in ultra high strength fiber reinforced concrete, (c) and (d) are cumulative hardening. FIG. 5 is a graph showing the calculation result of the influence coefficient (when 90 ° C. is maintained for 48 hours), and (e) is a graph showing the calculation result of the cumulative hardening influence coefficient (when 90 ° C. is maintained for 84 hours). It is the vertical sectional view and horizontal sectional view which show the rib and bran of a deformed reinforcing bar, and the outermost diameter. (A), (b) is a perspective view and (c) is a vertical sectional view showing another embodiment of a precast formwork and its manufacturing method in the plastic hinge structure of the present invention. It is a model figure which shows the behavior of the single column type RC bridge pier which has a plastic hinge structure which received external force. It is the precast formwork of the conventional plastic hinge structure, (a) is a perspective view which shows the split type precast formwork which has a crack induction joint, (b) is a horizontal cross section which shows the precast formwork which provided the crack induction notch FIG.

Explanation of symbols

1 …… Bridge pier 2 …… Column member 3 …… Footing 4 …… Precast formwork (invention)
5 ... Precast form 6 ... Regular concrete 10 ... Crack induction joint 11 ... Wire mesh 12 ... Reinforcement 13 ... Intermediate rebar 14 ... Axial rebar 20 ... Manufacturing form 21 ... Pressure hose 30 …… Precast form block 31 …… Rebar storage groove 32 …… Notch 33 …… High-strength grout material L …… Plastic hinge section

Claims (7)

  This is a plastic hinge structure of a concrete structure composed of a precast formwork made of high-strength fiber reinforced concrete or mortar and concrete cast in the precast formwork, and is high in the production formwork of the precast formwork. By placing the high-strength fiber reinforced concrete or mortar in multiple layers, joints where the fibers do not continue up and down are formed on the joint surface, and crack-inducing joints due to the joints are integrally formed on the precast formwork. A plastic hinge structure of a concrete structure characterized by having   The plastic hinge structure according to claim 1, wherein an uncured delayed thermosetting resin is applied to the reinforcing bar and placed in a manufacturing formwork, and high strength fiber reinforced concrete or mortar is placed and heat cured. A plastic hinge structure for a concrete structure in which a reinforcing bar in which a delayed thermosetting resin is cured after heat curing is enclosed in a precast mold. It is composed of a precast formwork made of high-strength fiber reinforced concrete or mortar and concrete cast in the precast formwork, and the precast formwork is a concrete structure constituted by laminating a plurality of precast formwork blocks. A plastic hinge structure,
Reinforcing bars are installed in the reinforcing bar storage grooves provided in the joints of the precast formwork blocks that have finished self-shrinking at the time of manufacture, and the voids of the reinforcing bar storage grooves are filled with high-strength grout material that is not mixed with fibers. By joining the precast formwork blocks to each other with the high-strength grout material arranged on the joining surface, reinforcing bars are included in the precast formwork, and a crack-inducing joint is formed by the high-strength grout material. A plastic hinge structure for a concrete structure.   The plastic hinge structure according to any one of claims 1 to 3, wherein a neutral axis position in a final state with respect to bending is a boundary position between the precast formwork and the internal concrete. Plastic hinge structure of the structure. A method for producing the precast formwork in a plastic hinge structure of a concrete structure composed of a precast formwork made of high-strength fiber-reinforced concrete or mortar and concrete cast in the precast formwork,
A high-strength fiber reinforced concrete or mortar is placed in the circumferential direction of the formwork to form a first layer in the precast formwork production form, and the same placement is repeated for the second and subsequent layers. A method for producing a precast mold, comprising: forming a joint in which fibers are not continuous vertically on a joint surface, and producing a crack-cast joint joint integrally formed with the joint.   6. The manufacturing method according to claim 5, wherein a wire mesh for preventing the fibers from continuing is laid on the joint surface. It is composed of a precast formwork made of high-strength fiber reinforced concrete or mortar and concrete cast in the precast formwork, and the precast formwork is a concrete structure constituted by laminating a plurality of precast formwork blocks. A method for producing the precast formwork in a plastic hinge structure,
A rebar storage groove is formed in the joint when the precast formwork block is manufactured, and the rebar is installed in the rebar storage groove of the precast formwork block after self-shrinking. A precast which is filled with a strength grout material, joins precast formwork blocks to each other with the high strength grout material arranged on the joining surface, encloses reinforcing bars, and forms crack-inducing joints with the high strength grout material A method for producing a precast formwork, characterized by producing a formwork.

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