JP6886664B2 - Plastic hinge structure of RC columnar structure and plastic hinge part repair method of RC columnar structure - Google Patents

Description

The present invention relates to a plastic hinge structure of an RC columnar structure and a method of repairing a plastic hinge portion of an RC columnar structure.

In the wake of a major earthquake such as the Hyogoken Nanbu Earthquake that occurred on January 17, 1995, seismic design (toughness design) based on the horizontal holding capacity method became the mainstream for RC structures such as bridge structures and building structures. It was. For this reason, for example, in RC columnar structures such as piers of bridge structures and columns of building structures, generally, a plastic hinge portion is provided at the lower part or upper part of the reinforcing bar to absorb seismic energy due to bending stress, and collapses. It is done to prevent brittle fracture of.

However, plastic hinges mean damage to the plastic hinges of RC columnar structures such as RC piers, and if the residual strain is large even if it does not collapse, not only large-scale repairs but also removal is unavoidable. Was also possible. For example, even if the superstructure of the bridge structure is sound, if the inclination angle of the RC pier, which is the substructure, is 1.0 degree or more, or the horizontal displacement of the top of the pier is 150 mm or more, the RC pier It was necessary to remove and install a new one.

As a method for reducing the residual strain of the plastic hinge portion, for example, in Patent Document 1, the bridge pedestal 10 includes a closed circular steel pipe 16 filled with concrete C inside, and the steel pipe 16 is footed. Plastic that is a normal steel pipe with a smooth inner peripheral surface, consisting of a plastic hinge region changing steel pipe 18 arranged near the joint with the portion 12 and a ribbed steel pipe 20 arranged above the changed steel pipe 18. The lower end edge of the hinge region changing steel pipe 18 is separated upward by a gap δ from the upper end surface of the footing portion 12, and the inner peripheral surface of the plastic hinge changing steel pipe 18 is coated with an adhesion preventive material 22 such as grease. A bridge pedestal structure in which an edge is cut from the concrete C to be filled therein is disclosed (claim 1, of the scope of the patent claim of Patent Document 1, paragraphs [0011] to [0032] of the specification. , See FIGS. 2, 3 etc. of the drawing).

It is said that the pier structure described in Patent Document 1 can minimize damage to the footing portion and the superstructure portion, and can be easily repaired or reinforced. However, in the pier structure described in Patent Document 1, since the plastic hinge changing steel pipe 18 is mounted on the outer surface of the plastic hinge portion, the plastic hinge changing steel pipe 18 is cut and removed, and the entire pier structure is removed. It had to be dismantled, removed and rebuilt. In other words, when dismantling and removing the pier structure and reconstructing it, it was necessary to support the superstructure with temporary columns such as vents. In short, the fact that repair and reinforcement can be easily performed refers only to the footing portion and the superstructure portion with little damage, and there is a problem that the structure is not such that the plastic hinge portion can be quickly repaired.

Further, as a method of repairing the plastic hinge portion, for example, in Patent Document 2, the concrete of the plastic hinge sections 2 and 2'of the damaged existing railway high bridge column 1 is scraped and the buckled axial reinforcing bar 3 is used. , 3'was exposed, the existing railway high bridge column 1 was removed leaving the buckled axial reinforcing bars 5, 5', and the buckled axial reinforcing bars 5, 5'were bent back and subjected to this bending back treatment. A new axial reinforcing bar 6 is connected to the axial reinforcing bar with joints 7 and 7', a plastic hinge section protection cap 8 and 8'is installed, and a band reinforcing bar 9 is wound around the new axial reinforcing bar 6. A method for replacing a damaged railway high-bridge column by placing concrete 10 on an axial reinforcing bar 6 around which the concrete is wound is disclosed (Patent Request of Patent Document 2). Scope claim 1, paragraphs [0012] to [0016] of the specification, FIG. 1 of the drawing, etc.).

However, since the railway viaduct column replacement method described in Patent Document 2 eventually replaces the existing railway viaduct column 1, the upper structure is vented or the like as in the case of the bridge pier structure described in Patent Document 1 described above. There was a problem that it was necessary to support it with a temporary support column or the like, and the structure was not such that the plastic hinge portion could be repaired quickly.

Further, in Non-Patent Document 1, a conventional RC that can reduce the residual strain of the pier column after an earthquake by using a copper-based superelastic shape memory alloy (CuAlMn) for the axial reinforcing bar of the plastic hinge portion. The structure of the pier column is disclosed (see pages 29 to 58 of Non-Patent Document 1).

However, in the structure of the conventional RC pier described in Non-Patent Document 1, the shape memory alloy is extremely expensive, it is difficult to reduce the damage of the plastic hinge portion, and the risk of collapse during a large earthquake is eliminated. There was a problem that it was not possible.

Japanese Unexamined Patent Publication No. 9-209308 Japanese Unexamined Patent Publication No. 2012-144919

M.'Saiid' Saiidi, Sebastian Varela, "DYNAMIC PERFORMANCE OF NOVELBRIDGE columns with superelastic CuAlMn shape memory and ECC", International Journal of Bridge Engineering (IJBE), vol.2, July 2014, p.29-58

Therefore, the present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to reduce residual strain of the plastic hinge portion while preventing brittle fracture such as collapse even in the event of a large earthquake. It is an object of the present invention to provide a plastic hinge structure of an RC columnar structure capable of rapid repair and a method of repairing a plastic hinge portion of the RC columnar structure.

The plastic hinge structure of the RC columnar structure according to claim 1 is provided on the upper part and / or lower part of the RC columnar structure that receives an axial force such as an RC bridge pedestal or an RC column, and bends that acts on the RC columnar structure. A plastic hinge structure of an RC columnar structure having a plastic hinged portion in which axial streaks yield due to stress to absorb seismic energy. In order to prevent damage to the core concrete that supports the axial force, the RC columnar structure A pipe body embedded along the central axis of the inside and extending vertically along the axial direction from the plastic hinge portion, and an axial muscle provided near the upper and lower ends of the plastic hinge portion and bending and yielding. It is provided with a plurality of pairs of mechanical joints for connecting the RC columnar structures, and a partition member having a plate surface orthogonal to the axial direction of the RC columnar structure and separating the plastic hinge portion from other portions. It is a feature.

The plastic hinge structure of the RC columnar structure according to claim 2 is the plastic hinge structure of the RC columnar structure according to claim 1. The partition material is made of a perforated steel plate such as an expanded metal or a punching metal and can be ventilated. It is characterized in that a hole is formed.

The method for repairing the plastic hinge portion of the RC columnar structure according to claim 3 is the plastic hinge repair portion of the RC columnar structure for repairing the plastic hinge portion of the plastic hinge structure of the RC columnar structure according to claim 1 or 2. The repair method is characterized by having a plastic hinge portion concrete removing step of removing the damaged concrete of the plastic hinge portion while supporting the load of the superstructure with the core concrete in the pipe body.

The method for repairing the plastic hinge portion of the RC columnar structure according to claim 4 is the method for repairing the plastic hinge portion of the RC columnar structure according to claim 3 , wherein the plastic hinge portion concrete removing step removes the mechanical joint. It is characterized in that the damaged axial muscle is removed.

The method for repairing a plastic hinge portion of an RC columnar structure according to claim 5 is the method for repairing a plastic hinge portion of an RC columnar structure according to claim 3 or 4 , wherein the step of removing concrete from the plastic hinge portion is a shaft from the partition material. It is characterized in that all the concrete of the plastic hinge portion on the outer side of the direction is removed.

According to the invention of claim 1 or 2 , damage to the plastic hinge portion at the time of an earthquake is divided into a portion outside the pipe body that is damaged and absorbs energy, and a portion of the core concrete inside the pipe body that is not damaged. It is a separate dual system. Therefore, it is possible to reduce the residual strain of the plastic hinge portion while preventing dangerous brittle fracture such as collapse even in the event of a large earthquake. Further, since the mechanical joint can be removed to remove the yielded axial streaks, it is easy to remove the damaged concrete of the plastic hinge portion, and quick repair is possible.
Further, according to the invention of claim 1 or 2, since the partition material for separating the plastic hinge portion and the other portion is provided, the plastic hinge portion damaged at the time of an earthquake and the other general portion are separated from each other. A plate-shaped partition is formed on the surface. Therefore, the concrete of the plastic hinge portion can be easily removed, the residual strain can be reduced, and the repair can be performed more quickly.

In particular, according to the invention of claim 2 , even if there is a partition material which is a horizontal member, there is no possibility that air pools will be formed when concrete is placed in a new RC columnar structure, and a place where concrete is placed poorly such as a junker. It is possible to carry out the construction easily and in a short time by eliminating the above.

According to the inventions according to claims 3 to 5 , the damaged concrete of the plastic hinge portion is removed while supporting the load of the superstructure with the core concrete in the pipe, so that when repairing the plastic hinge portion, a vent or the like is used. There is no need to provide a temporary support mechanism. Therefore, the plastic hinge portion can be easily repaired in a short time, and the temporary installation cost can be reduced and the repair can be performed at low cost.

In particular, according to the invention of claim 4 , since the mechanical joint is removed, the damaged axial bar is removed, and the damaged concrete of the plastic hinge portion is removed, the repair of the plastic hinge portion is easier and shorter. Can be done in time.

In particular, according to the invention of claim 5 , since the plastic hinge portion and other portions are separated by a partition material and edge-cut, not only the residual strain of the plastic hinge portion can be reduced, but also the plastic hinge portion is damaged at the time of an earthquake. It is possible to reduce the risk that the general part will receive the above. In addition, since the edge is cut by partitioning with a partition material, it is extremely easy to remove the damaged concrete of the plastic hinge part, and when the concrete is scraped and removed, the general part can be damaged. Absent.

It is a block diagram which shows the case where the plastic hinge structure of the RC columnar structure which concerns on embodiment of this invention is applied to the rigid structure of a pier. It is a structural explanatory view which shows typically the plastic hinge structure of the RC columnar structure of the same above. It is a flowchart which shows each process of the plastic hinge part repair method of RC columnar structure which concerns on embodiment of this invention. It is a figure which shows the specimen made as the conventional RC pier, (a) is a sectional view, (b) is a side view. It is a figure which shows the specimen produced as the RC pier which concerns on this invention, (a) is a sectional view, (b) is a side view. It is a figure which shows the damage state at the end of 6δy. It is a figure which shows the damage state at the end of an experiment. It is a history curve of the load-displacement of the conventional RC pier. It is a history curve of the load-displacement of the RC pier according to the present invention. It is a graph which shows the comparison of the envelope of FIG. 8 and FIG. It is a graph which shows the comparison of the residual displacement of the conventional RC pier and the RC pier which concerns on this invention.

Hereinafter, an embodiment of the plastic hinge structure of the RC columnar structure and the method of repairing the plastic hinge portion of the RC columnar structure according to the present invention will be described in detail with reference to the drawings.

<Plastic hinge structure of RC columnar structure>
The plastic hinge structure of the RC columnar structure according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. In this embodiment, an RC pier will be illustrated as an RC columnar structure. FIG. 1 is a configuration explanatory view showing a case where the plastic hinge structure 1 of an RC pier, which is a plastic hinge structure of an RC columnar structure according to an embodiment of the present invention, is applied to a rigid pier structure, and FIG. 2 is a configuration explanatory view. It is a structural explanatory view which shows typically the plastic hinge structure 1 of the RC pier which concerns on this embodiment.

First, the RC pier exemplified as the RC columnar structure will be briefly described. As shown in FIG. 1, in the RC pier 10 which is the RC columnar structure according to the present embodiment, the RC pier 10 which is the lower structure (substructure) of the bridge is rigid together with the upper structure (superstructure). It is the pier of the connected rigid-frame bridge RB. The RC pier 10 is rigidly joined to the footing 11 which is the foundation of the RC pier 10 and the superstructure 12 (superstructure) composed of a bridge girder, a deck, and the like.

As shown in FIG. 1, the plastic hinge structure 1 of the RC pier 10 according to the present embodiment is provided on both the upper part and the lower part of the RC pier 10. This is because in the case of a rigid-frame bridge RB in which the substructure (substructure) of the bridge and the superstructure 12 are rigidly connected, a horizontal force due to seismic energy also acts on the upper part of the RC pier 10, which is the substructure. Of course, the plastic hinge structure 1 of the RC pier 10 may be provided only at the lower part of the RC pier 10 when a bearing is provided between the RC pier 10 and the upper structure 12, and in some cases, the RC pier It may be provided only on the upper part of 10.

As shown in FIG. 2, the plastic hinge structure 1 according to the present embodiment is a plastic hinge structure of an RC pier 10 including a plastic hinge portion 2 that absorbs seismic energy and a general portion 3 other than that.

(Plastic hinge part)
The plastic hinge portion 2 is provided at the lowermost part of the RC pier 10 connected to the footing 11 and at the lowermost part of the RC pier 10 connected to the upper structure 12. In this plastic hinge portion 2, a plurality of axial reinforcing bars 4 (axial reinforcing bars) buried and arranged along the axial direction (vertical direction) of the RC pier 10 bend and yield, and the entire RC pier 10 is displaced to perform RC. It has a function of consuming and absorbing the seismic energy input to the pier 10 as strain energy.

Axial reinforcing bars 4 are arranged at least at four corners of the RC pier 10, and a plurality of reinforcing bars (not shown) are arranged at predetermined intervals in the vertical direction so as to surround them. Of course, the number of axial reinforcing bars 4 and the number of reinforcing bars (band reinforcing bars) and the like are appropriately set according to the structural design.

The plastic hinge portion 2 includes a plurality of axial reinforcing bars 4, a plurality of pairs of upper and lower mechanical joints 5 in which these axial reinforcing bars 4 are removed and interchangeably connected, and along the central axis of the RC bridge pedestal 10. It is provided with a steel pipe 6 which is a pipe body buried in the water. Further, at the boundary between the plastic hinge portion 2 and the general portion 3 of the RC pier 10, a steel plate 7 is installed as a partitioning material for separating them.

(Mechanical fitting)
The mechanical joint 5 makes it possible to replace the axial reinforcing bar 4 damaged when seismic energy is input to the plastic hinge portion 2, and may be a general mechanical joint. Here, the mechanical joint refers to a threaded joint, a mortar-filled joint, an end threaded joint, a steel pipe crimping joint, a steel pipe crimping threaded joint, or a joint in which these are used in combination. In short, the mechanical joint refers to a joint in which a steel pipe (sleeve or coupler) made of a special steel material and a joint of a deformed reinforcing bar are joined by utilizing the meshing of the joints of the reinforcing bar, instead of directly joining the reinforcing bar.

Explaining a typical example, a threaded rebar joint is a joint in which deformed reinforcing bars in which the surface nodes are threaded at the manufacturing stage are joined by a steel pipe (coupler) threaded inside. is there. Further, the mortar-filled joint is a joint in which a high-strength mortar is filled in a gap between a steel pipe (sleeve) for joint and a reinforcing bar whose inner peripheral surface is ribbed and joined.

(Steel pipe)
The steel pipe 6 is a steel pipe having a circular cross section for forming a CFT (Concrete Filled Tube) in which the pipe axis is arranged so as to overlap the centroid position of the horizontal cross section of the RC pier 10 and the inside is filled with concrete. The steel pipe 6 has a function of protecting the concrete filled inside with core concrete that is not damaged even when seismic energy is input. The steel pipe according to the present invention is not limited to a steel pipe having a circular cross section, and may be a square steel pipe or a steel pipe having a star-shaped cross section. However, since it is not possible to predict where the seismic wave will come from, it is preferable that the cross-sectional shape such as a circular cross section has no anisotropy.

The diameter and thickness of the steel pipe 6 are set by the ratio of the core concrete required to support the superstructure 12 to the outer concrete of the plastic hinge portion 2 for absorbing seismic energy when damaged. Of course, at least the diameter of the steel pipe 6 needs to be smaller than the width in the short side direction of the RC pier 10, and generally, 1/3 to 1/2 of the width in the short side direction of the RC pier 10. It will be in the range of degree.

Further, as shown in FIG. 2, the length of the steel pipe 6 is longer than the plastic hinge portion 2 both above and below, and is extended so as to bite into the footing 11 and the general portion 3 by a predetermined length. Specifically, the length of biting into the footing 11 and the general portion 3 must be such that the steel pipe 6 does not come out from the footing 11 and the general portion 3 even when a horizontal force for yielding the steel pipe 6 acts. is there. Of course, as the pipe body according to the embodiment of the present invention, the steel pipe 6 has been described as an example, but a cylinder body made of FRP, reinforcing fibers, or the like may be used. In short, the pipe body according to the present invention may be a tubular object that can withstand a predetermined horizontal force such as seismic energy and can protect the core concrete.

(Partition material)
The steel plate 7 is a rectangular steel plate having a predetermined thickness, which is provided between the plastic hinge portion 2 and the general portion 3 and functions as a partitioning material for separating the plastic hinge portion 2 and the general portion 3, and is the RC pier 10. It has a plate surface orthogonal to the axial direction. By providing the steel plate 7, the damaged concrete can be easily removed and the residual strain can be reduced. Further, as will be described later, the plastic hinge portion 2 damaged by the seismic force can be quickly repaired.

The steel plate 7 may be a perforated steel plate such as an expanded metal or a punching metal. By using a perforated steel plate, air can pass through the holes. Therefore, when the new concrete of the RC pier 10 is placed, there is no possibility that an air pool is formed, and it is possible to eliminate a defective concrete placement place such as a junker, which is preferable. Further, the partition material according to the present invention may be a sheet material such as an inorganic plate material or a vinyl sheet. In short, a plate-shaped or sheet-shaped member can be applied to the partition material according to the present invention as long as it is a member that separates the plastic hinge portion from the other portion, regardless of the presence or absence of holes.

According to the plastic hinge structure 1 of the RC pier 10 according to the present embodiment described above, the plastic hinge portion 2 at the time of an earthquake is damaged, and the outer portion of the steel pipe 6 that is damaged and absorbs energy is damaged. It is a double system divided into a core concrete part in the steel pipe 6 that does not exist. Therefore, even in the event of a large earthquake, the outer portion of the plastic hinge portion 2 absorbs energy to prevent dangerous brittle fracture such as collapse, and the damaged portion of the plastic hinge portion 2 is replaced to reduce residual strain. be able to. Further, since the mechanical joint 5 can be removed to remove the yielded axial reinforcing bar 4, it is easy to remove the damaged concrete of the plastic hinge portion 2, and quick repair is possible.

Further, according to the plastic hinge structure 1, a steel plate 7 is provided between the plastic hinge portion 2 which is damaged at the time of an earthquake and the other general portion 3, and the plastic hinge portion 2 and the general portion 3 are cut off from each other. There is. Therefore, it is extremely easy to remove the concrete of the plastic hinge portion 2, and quick repair is possible.

<Repair method for plastic hinges of RC columnar structures>
Next, a method of repairing the plastic hinge portion of the RC columnar structure according to the embodiment of the present invention will be described with reference to FIG. The case where the plastic hinge portion 2 is repaired when the plastic hinge portion 2 is damaged by the seismic force input to the plastic hinge structure 1 of the RC pier 10 described above will be described as an example. FIG. 3 is a flowchart showing each step of the method of repairing the plastic hinge portion of the RC columnar structure according to the embodiment of the present invention.

(1. Reinforcing bar removal process)
As shown in FIG. 3, first, in the method of repairing the plastic hinge portion of the RC columnar structure according to the present embodiment (hereinafter, simply referred to as the method of repairing the plastic hinge portion), the plastic hinge portion 2 yields and is deformed in the axial reinforcing bar. Reinforcing bar removal step of removing 4 is performed.

Specifically, the mechanical joint 5 is removed, and the deformed axial reinforcing bar 4 is removed. At this time, since the joints are originally joined via the mechanical joint 5, it is extremely easy to remove the axial reinforcing bars 4.

(2. Plastic hinge part concrete removal process)
Next, in the plastic hinge portion repair method according to the present embodiment, the plastic hinge portion concrete removing step of removing the damaged concrete of the plastic hinge portion 2 is performed. At this time, the damaged concrete of the plastic hinge portion 2 is removed while supporting the load of the superstructure 12 with the core concrete in the steel pipe 6. Therefore, it is not necessary to provide a temporary support mechanism for temporarily supporting the load of the superstructure 12 such as a vent.

Further, in this step, since all the axial reinforcing bars 4 are removed in the previous step, the concrete portion is exposed, and it is extremely easy to scrape the damaged concrete with a chipping machine or the like.

Further, in this step, all the concrete of the plastic hinge portion 2 on the outer side in the axial direction is removed from the steel plate 7 which is a partition material. At this time, in the plastic hinge structure 1 of the RC pier 10, the plastic hinge portion 2 and the general portion 3 are edge-cut by the steel plate 7 as described above. Therefore, in this step, it is extremely easy to scrape the damaged concrete, and the general portion 3 is not affected when scraping the concrete of the plastic hinge portion 2. Therefore, the residual strain can be reduced also in this respect.

(3. Reinforcing bar and formwork assembly process)
Next, in the plastic hinge portion repair method according to the present embodiment, a new axial reinforcing bar 4 and necessary reinforcing bars are arranged on the plastic hinge portion 2 via a new mechanical joint 5, and concrete is placed on the outside. Reinforcing bar and formwork assembly process to assemble the formwork.

(4. Concrete placing process)
Next, in the plastic hinge portion repair method according to the present embodiment, a concrete placing step of placing concrete in the formwork assembled in the previous step is performed.

Then, if the mold is removed after a curing period until the cast concrete develops a predetermined strength, all the repairs of the plastic hinge portion repair method according to the present embodiment are completed.

According to the plastic hinge portion repair method according to the present embodiment described above, the entire process is performed while supporting the load of the superstructure 12 with the core concrete in the steel pipe 6. Therefore, it is not necessary to provide a temporary support mechanism for temporarily supporting the load of the superstructure 12 such as a vent. Therefore, the plastic hinge portion 2 can be easily repaired in a short time, and the temporary installation cost can be reduced and the repair can be performed at low cost.

Further, according to the method for repairing the plastic hinge portion according to the present embodiment, the mechanical joint 5 is removed, the damaged axial reinforcing bar 4 is removed, and the damaged concrete of the plastic hinge portion 2 is removed. Repair of 2 can be performed easily and in a short time.

Further, according to the plastic hinge portion repair method according to the present embodiment, the plastic hinge portion 2 and the general portion 3 are separated by a steel plate 7 and edge-cut. Therefore, when the concrete is scraped, the general portion 3 is separated. There is no risk of damage, and the residual strain of the plastic hinge portion 2 can be reduced. In addition, it is possible to reduce the risk of damage to the general part 3 during an earthquake.

The plastic hinge structure of the RC columnar structure and the method of repairing the plastic hinge portion of the RC columnar structure according to the embodiment of the present invention have been described in detail above. It merely shows one embodiment that has been embodied in doing so. Therefore, the technical scope of the present invention should not be construed in a limited manner by these.

In particular, although the RC pier has been described as an example of the RC column structure, the present invention is not limited to the RC pier, and the present invention can be applied to the RC column of the building structure and the like. In short, the RC columnar structure to which the present invention can be applied may be an RC structure that is installed with the vertical direction as the axial direction and receives an axial force such as a load of the superstructure. Further, the RC columnar structure to which the present invention can be applied is a structure designed with a toughness design in which axial streaks are finally bent and broken by bending stress prior to brittle fracture such as shear fracture and crushing of a concrete portion. Is.

<Effect confirmation experiment>
Next, the verification experiment performed for confirming the effect of the present invention will be described with reference to FIGS. 4 to 11.

(Sample)
First, the specimen used in the experiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing a specimen prepared as a conventional RC pier, and FIG. 5 is a diagram showing a specimen prepared as an RC pier according to the present invention.

The specimen shown in FIG. 4 was prepared as a conventional RC pier, and the specimen shown in FIG. 5 was prepared as an RC pier according to the present invention. The cross-sectional dimensions of each specimen were a square cross section of 250 mm × 250 mm, the height of the specimen was 1400 mm, the effective height was 875 mm, and the shear span ratio was 3.5.

In addition, a total of 12 D13 (SD295) bars were placed at 60 mm intervals for the axial reinforcing bars, and D6 (SD295) were placed at 70 mm intervals for the band reinforcing bars. The axial rebar ratio is 2.4% and the band rebar ratio is 1.0%. Yield strength of longitudinal bars obtained from a tensile test is 346N / mm ² in a conventional RC piers, 362N / mm ² at RC piers according to the present invention, the yield strength of the hoop is both a 360N / mm ^2.

The compressive strength of the concrete on the day of the experiment on the conventional RC bridge skeleton ^{and the plastic hinge of the RC bridge according to the present invention was 28.9 N / mm 2} , and the concrete on the day of the experiment on the RC bridge skeleton outside the plastic hinge according to the present invention. The compressive strength is 31.3 N / mm ² . The plastic hinge length of the conventional RC pier is 130 mm, and the plastic hinge length of the RC pier according to the present invention is 230 mm in consideration of the length of the mechanical joint.

The hinge portion of the RC pier according to the present invention is provided with a steel pipe, a mechanical joint, and a steel plate in the same manner as the plastic hinge portion 2 described above. The steel pipe had a diameter of 89.1 mm, a wall thickness of 1.6 mm, a total length of 740 mm, and was placed up to a height of 460 mm from the base of the pier. The steel plate is placed at a height of 230 mm from the upper end of the plastic hinge, that is, the base of the pier, and the mechanical joint is 50 mm long and placed under the base of the pier and the steel plate, two for each axial reinforcement. There was.

(experimental method)
Next, the experimental method will be described. In this experiment, H steel and weight steel plate were placed on the specimen, and with ^{the axial stress of 0.37 N / mm 2} applied to the base of the pier, horizontal force was applied by displacement control using a hydraulic jack to load positive and negative alternating numbers. An experiment was conducted. The loading speed is 0.04 to 0.4 mm / s. In addition, the loading pattern was a constant displacement amplitude gradual increase method, and the same displacement amplitude was given three times each.

The reference displacement is defined as the yield displacement δy of the axial reinforcement, and the horizontal displacement at the loading position when the outermost axial reinforcement strain near the base of the bridge pedestal reaches the yield strain at the time of the experiment is defined as the yield displacement δy. The conventional RC pier has 1δy of 4 mm, and the RC pier according to the present invention has 1δy of 4.5 mm. The displacement amplitudes given in this experiment are 1δy to 6δy, 8δy, 11δy for the conventional RC pier, and 1δy to 10δy for the RC pier according to the present invention.

The loading direction is the arrow direction (EW direction) in FIGS. 4 and 5, and the case of pushing the hydraulic jack is defined as the normal load and the case of pulling is defined as the negative load. The E surface is the normal load surface and the W surface is the negative load surface. And said.

In the experiment, horizontal load, horizontal displacement, strain of axial reinforcing bars and steel pipes, and strain of reinforcing bars were measured. After the loading was completed, the axial reinforcing bars, the reinforcing bars, and the concrete of the RC pier plastic hinge portion according to the present invention were removed, and the horizontal displacement at the loading position was measured.

[Experimental result]
Next, the experimental results will be described with reference to FIGS. 6 to 11. First, the damage situation will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram showing a damage situation at the end of 6δy, and FIG. 7 is a diagram showing a damage situation at the end of the experiment.

(Damage status)
As shown in FIGS. 6 and 7, cracks developed during loading of each specimen 1δy to 6δy, and there were some signs of the cover concrete peeling off. Large cover concrete peeling occurs when the conventional RC pier (RC-1) is loaded with 8δy and the RC pier (RC-PHS) according to the present invention is loaded with 9δy, and finally RC-1 is 11δy and RC-PHS. The experiment was terminated because the bearing capacity was reduced due to the out-of-plane buckling of the axial reinforcement and damage to the core concrete during loading.

6δy Fig. 6 and Fig. 7 show the cracks on the four sides of the pier skeleton at the end of loading and the end of the experiment, the peeling of the cover concrete, and the buckling of the axial reinforcing bars. Each specimen is marked with a mesh at 83.3 mm intervals. From FIGS. 6 and 7, in RC-1, cracks in concrete, peeling of cover concrete, and protrusion of axial reinforcing bars can be seen in the section 200 mm from the base of the pier. On the other hand, in RC-PHS, the cover concrete was peeled off at a position 300 mm from the base of the pier, and the axial reinforcing bars and the mechanical joints were also bulged out at the upper part of the mechanical joints. From this, it can be seen that the formation status of the plastic hinge, which is the damaged part, differs between RC-1 and RC-PHS.

Next, the load-displacement relationship will be described with reference to FIGS. 8 to 11. FIG. 8 is a load-displacement history curve of a conventional RC pier, and FIG. 9 is a load-displacement history curve of the RC pier according to the present invention. FIG. 10 is a graph showing a comparison of the envelopes of FIGS. 8 and 9. FIG. 11 is a graph showing a comparison of residual displacement between a conventional RC pier and an RC pier according to the present invention.

The horizontal axis of FIGS. 8 to 10 is the horizontal displacement at the loading position, and the vertical axis is the horizontal load. Here, the drift ratio is the ratio of the effective height of the pier to the horizontal displacement. The solid line in FIG. 10 is the conventional RC pier (RC-1), and the broken line is the RC pier (RC-PHS) according to the present invention.

According to this, RC-1 has a stable maximum yield strength of 61 kN and a drift ratio of up to 5% near the maximum yield strength. On the other hand, RC-PHS has a stable maximum yield strength of 75 kN and a drift ratio of up to 5% near the maximum yield strength. Here it there is a difference of 14kN maximize strength is 362N / mm ² in RC-PHS whereas the yield strength of the longitudinal bar is RC-1 at 346N / mm ² between the mechanical joint, In addition, it is conceivable that the bearing capacity will increase due to the steel pipe.

Further, from FIG. 10, it can be said that the deformation performances are the same because the proof stress of both specimens is not significantly reduced. However, considering that RC-PHS has a larger total number of repeated loads than RC-1, it can be said that the deformation performance of RC-PHS is equal to or better than that of RC-1.

In addition, FIG. 11 shows a comparison of the relationship between the displacement amplitude and the residual displacement when the horizontal load in the first cycle at each displacement amplitude is 0 kN. From FIG. 11, it can be seen that the residual displacement of RC-PHS is slightly reduced when a horizontal displacement similar to that of RC-1 is applied. This is also considered to be due to the steel pipe placed in the center of the RC-PHS skeleton.

Finally, let us consider after the loading is completed. In RC-PHS, after removing the horizontal load after loading, the axial reinforcing bars, reinforcing bars and core concrete of the plastic hinges were removed. At that time, it was possible to maintain the loading load by the core portion made of steel pipe and concrete. However, in the end, a residual displacement of 42 mm occurred. It is considered that the cause is that the steel pipe yields at a position 130 mm from the base of the pier when loaded with 3δy, and the steel pipe is largely plasticized.

Summarizing the above experiments, it was found that the RC pier according to the present invention has a different formation state of the plastic hinge, which is a damaged part, as compared with the conventional RC pier.

Further, the RC pier according to the present invention has a deformation performance equal to or higher than that of the conventional RC pier from the comparison of the envelopes of the history curves in the load-displacement relationship, and it is expected that the bearing capacity will be increased and the residual displacement will be slightly reduced. it can.

The concrete and reinforcing bars of the plastic hinge portion of the RC pier according to the present invention could be easily removed, and the loading load could be maintained by the core concrete in the steel pipe. However, residual displacement was observed at the time of removal, which is considered to be due to the plasticization of the steel pipe at an early stage.

1: Plastic hinge structure 2: Plastic hinge part 3: General part 4: Axial reinforcing bar (axial reinforcing bar)
5: Mechanical fitting 6: Steel pipe (tube body)
7: Steel plate (partition material)
RB: Rigid frame bridge (bridge)
10: RC pier 11: Footing 12: Superstructure

Claims (5)

Plastic that is provided on the upper and / or lower part of an RC columnar structure that receives axial force such as RC bridge piers and RC columns, and the axial muscle yields due to the bending stress acting on the RC columnar structure to absorb seismic energy. A plastic hinge structure of an RC columnar structure having a hinge portion.
In order to prevent damage to the core concrete that supports the axial force, a pipe body that is buried along the central axis in the RC columnar structure and extends vertically along the axial direction from the plastic hinge portion, and a pipe body.
A plurality of pairs of mechanical joints provided near the upper and lower ends of the plastic hinge portion and connecting the axial streaks that bend and yield are provided , and also.
A plastic hinge structure of an RC columnar structure, which has a plate surface orthogonal to the axial direction of the RC columnar structure and includes a partition member for separating the plastic hinge portion from another portion. The plastic hinge structure of the RC columnar structure according to claim 1, wherein the partition material is made of a perforated steel plate such as an expanded metal or a punching metal and has a ventilable hole. A method for repairing a plastic hinge portion of an RC columnar structure according to claim 1 or 2 , wherein the plastic hinge portion of the plastic hinge structure of the RC columnar structure is repaired.
A method for repairing a plastic hinge portion of an RC columnar structure, which comprises a plastic hinge portion concrete removing step of removing the damaged concrete of the plastic hinge portion while supporting the load of the superstructure with the core concrete in the pipe body. The method for repairing a plastic hinge portion of an RC columnar structure according to claim 3 , wherein the step of removing the plastic hinge portion concrete is performed by removing the mechanical joint and removing the damaged axial streaks. The method for repairing a plastic hinge portion of an RC columnar structure according to claim 3 or 4 , wherein the step of removing the concrete of the plastic hinge portion is to remove all the concrete of the plastic hinge portion on the outer side in the axial direction from the partition member. ..

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