Concrete column and method for improving seismic isolation of concrete column

Abstract

To provide a base isolation structure of a concrete column, which can enhance aseismatic strength without the need for large-scale construction work.SOLUTION: A concrete column for supporting an overhead electric wire, the concrete column being erected in a vertical direction, the concrete column being divided into an upper column part and a lower column part at a predetermined interval in a state where axes of the upper column part and the lower column part coincide with each other, A pair of flanged half-split steel pipes are joined to the lower end of the upper pillar part and the upper end of the lower pillar part so that the flanges face each other, a seismic isolation rubber body having a smaller outer shape than the flanges in a plan view is disposed between the upper pillar part and the lower pillar part, and a plurality of support members are disposed between the flanges of the pair of flanged half-split steel pipes so as to surround the seismic isolation rubber body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a seismic isolation structure for a concrete pillar and a method for improving the seismic isolation performance of a concrete pillar, and more particularly to a seismic isolation structure for a concrete pillar suitable for, for example, a train line support structure, and a method for improving the seismic isolation performance of an existing concrete pillar. [Background technology]

[0002] In recent years, there has been an increase in the occurrence of large earthquakes that cause buildings to collapse, so there is an urgent need to take measures to counter earthquakes on the electricity poles erected alongside railway tracks and to reinforce existing electricity poles against earthquakes. Conventionally, earthquake countermeasures for prestressed concrete columns (hereinafter referred to as PC columns) used as supports for electric train lines have been widely implemented, including high-toughness reinforcement, conversion to portal-type columns, and replacement with steel pipe columns. Furthermore, earthquake countermeasures for structures above tracks have been proposed, such as a method of adding seismic control performance using viscoelastic dampers (see Patent Document 1), and earthquake countermeasures for PC columns have been proposed, such as a method of response control by replacing sand-filled foundations with silicone rubber-filled foundations (see Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-249795 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-187381 Summary of the Invention [Problem to be solved by the invention]

[0004] In existing overhead structures adjacent to substations, consisting of electrification poles and beams, known as structures, where PC poles are used as electrification poles, there have been several reported incidents of damage to the lower parts of the poles due to past earthquakes. Therefore, the inventors have investigated earthquake-resistant reinforcement techniques for existing PC poles. As a result, due to the complexity of the structure, if the equipment is damaged in an earthquake, it takes a great deal of time and effort to restore it.In addition, since it is not easy to replace the electric poles with new ones, the challenge is how to reduce the earthquake response load of existing structures.

[0005] However, it has become clear that none of the conventional earthquake countermeasure technologies are suitable for seismic reinforcement of existing structures. For example, the measures described in Patent Documents 1 and 2 above require complex structures for seismic control and large-scale construction work, making them unsuitable for seismic reinforcement of existing structures. The present invention was made in response to the above-mentioned problems, and its purpose is to provide a seismic isolation structure for concrete pillars that can improve seismic isolation without requiring large-scale construction work. Another object of the present invention is to provide a method for improving the seismic isolation of concrete pillars that is suitable for increasing the seismic isolation of existing electric train line support structures. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention is A concrete pole erected in the vertical direction to support an overhead electric wire, The upper and lower pillars are separated at a predetermined interval with their axes aligned. A pair of flanged half steel pipes are connected to the lower end of the upper column portion and the upper end of the lower column portion so that the flanges face each other, Between the upper column portion and the lower column portion, a seismic isolation rubber body having an outer shape smaller than that of the flange in a plan view is disposed, A plurality of support members are arranged between the flanges of the pair of flanged half steel pipes so as to surround the seismic isolation rubber body.

[0007] With the concrete pillar having the above-mentioned configuration, a single pillar is divided into upper and lower halves with a seismic isolation rubber body interposed between them, so that even if shaking occurs due to an earthquake, the seismic isolation rubber body can prevent the shaking of the foundation from being transmitted to the upper part, thereby preventing the collapse of the concrete pillar. Furthermore, since multiple support members are arranged between the flanges of the half steel pipes so as to surround the seismic isolation rubber body, they can support the vertical load immediately after the concrete pillar is cut during seismic isolation work, and after installation, they can withstand external forces associated with constant loads such as wind and vibrations caused by passing trains.

[0008] Here, the seismic isolation rubber body has a laminated structure of a plurality of rubber plates or a laminated structure in which a plurality of rubber plates and steel plates are alternately laminated. With this configuration, the seismic isolation rubber body can exhibit the necessary performance for seismic isolation, being rigid in the vertical direction and flexible in the horizontal direction.

[0009] Preferably, the support material is made of a deformable material and is configured so that when a force greater than a predetermined value is applied, the support material deforms and the seismic isolation function of the seismic isolation rubber body is realized. Alternatively, the support material may be made of a rigid material and configured so that when a force greater than a predetermined level is applied, it comes off from between the flanges, allowing the seismic isolation function of the seismic isolation rubber to be exerted, or it may be made of a brittle material and configured so that when a force greater than a predetermined level is applied, it breaks from between the flanges, allowing the seismic isolation function of the seismic isolation rubber to be exerted.

[0010] According to the above-mentioned configuration, the seismic isolation function of the seismic isolation rubber is only exerted when an earthquake of a predetermined strength or greater occurs. Therefore, under normal circumstances, the support material can support external forces associated with constant loads such as wind and vibrations caused by passing trains, preventing deformation of the seismic isolation rubber. This can suppress deterioration of the seismic isolation rubber and reduce horizontal deviation of the overhead wires.

[0011] Furthermore, it is desirable that the earthquake-resistant structure consisting of the flanged half steel pipe, the seismic isolation rubber body, and the support material be installed at a position higher than the upper end of the parapet wall installed on the elevated structure. With this configuration, the earthquake-resistant structure installed midway up the concrete pillar does not interfere with the parapet wall, so when installing an earthquake-resistant structure on the concrete pillar, it is not necessary to carry out work to renovate the parapet wall.

[0012] In addition, other inventions according to the present application include: A method for improving the seismic isolation of a concrete pole for improving the seismic isolation of a vertically erected concrete pole supporting an overhead electric wire, comprising: a position determination step for determining a height position at which the earthquake-resistant structure of the concrete pillar to be reinforced is to be provided; a half steel pipe joining process in which a pair of flanged half steel pipes are joined to the outer circumferential surface of the concrete column to be reinforced at the determined height so that the flanges face each other; a support member attachment step of inserting a support member over half the circumference between the flanges of the pair of flanged half steel pipes; a concrete pillar cutting process for cutting and removing a portion of the concrete pillar corresponding to the space between the flanges of the pair of flanged half steel pipes; a seismic isolation rubber body installation process for inserting a seismic isolation rubber body into the cut portion of the concrete column; and a support member attaching step of inserting the support member over the remaining half circumference between the flanges of the pair of flanged half steel pipes.

[0013] By following the above-described procedure for improving the seismic isolation of concrete pillars, even if shaking occurs due to an earthquake, the seismic isolation rubber body will prevent the shaking of the foundation from being transmitted to the upper part, thereby providing a seismic isolation function that can prevent the collapse of the concrete pillar to existing concrete pillars without carrying out large-scale construction work. In addition, since the support material installed between the flanges supports the load of the upper part of the concrete column that has been cut along the way, earthquake-resistant structures can be added to existing concrete columns without using large heavy machinery. [Effects of the Invention]

[0014] According to the present invention, it is possible to improve the seismic isolation of concrete poles that constitute electric train line support structures, which are called structures and are made up of electrification poles and beams. Also, the method for improving the seismic isolation of concrete poles according to the present invention has the effect of improving the seismic isolation of concrete poles that constitute existing structures. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B show an embodiment of a seismic isolation structure for a concrete column according to the present invention, in which (A) is a front view of the seismic isolation structure, and (B) is a cross-sectional plan view taken along line BB in (A). [Figure 2] 1 shows an example of a flanged half steel pipe that constitutes a seismic isolation structure installed on a concrete column of an embodiment, where (A) is an oblique view showing one half steel pipe, (B) is an oblique view showing the half steel pipe joined together, and (C) is an oblique view showing the half steel pipe joined together in a modified example. [Figure 3] FIG. 1 is an overall front view showing an example in which a seismic isolation structure is applied to a concrete pillar that constitutes a train line support structure. [Figure 4] 1 is a flowchart showing an example of a construction procedure for a method for improving the seismic isolation performance of a concrete pillar according to the present invention. [Figure 5] 3 is a front view (top) and a cross-sectional plan view (bottom) showing the state of the reinforcement part of the concrete column at each step of the construction of the seismic isolation structure according to the procedure of the flowchart in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of a seismic isolation structure for a concrete pillar and a method for improving the seismic isolation performance of a concrete pillar according to the present invention will be described in detail with reference to the drawings. An embodiment of a seismic isolation structure for a concrete column according to the present invention is shown in Figure 1. Figure 1(A) is a front view of the seismic isolation structure, and Figure 1(B) is a cross-sectional plan view taken along line BB in (A).

[0017] The present invention relates to a seismic isolation structure for a concrete pillar, and since the seismic isolation structure of this embodiment is provided on a portion of the concrete pillar, the entire concrete pillar is not shown in Figure 1, and only the portion where the seismic isolation structure is provided is shown. Furthermore, although the inventors have studied prestressed concrete pillars (PC pillars), the present invention is also applicable to ordinary concrete pillars, and therefore will be referred to as concrete pillars in the description of the embodiment.

[0018] The seismic isolation structure 20 for a concrete pillar of this embodiment is provided midway along a concrete pillar 10, as shown in Fig. 1. Fig. 1 shows only the upper column portion 10a and the lower column portion 10b of the concrete pillar 10, with the seismic isolation structure 20 shown between 10a and 10b, but the concrete pillar 10 is cut at the center of the seismic isolation structure 20, and the upper column portion 10a and the lower column portion 10b are joined by the seismic isolation structure 20 and maintained at a predetermined distance with their axes aligned.

[0019] The seismic isolation structure 20 shown in Fig. 1 has four flanged half steel pipes 21 as shown in Fig. 2(A), two of which are fixed to the lower end of the upper column portion 10a with the flanges 21a facing downward, and the remaining two are fixed to the upper end of the lower column portion 10b with the flanges 21a facing upward. The two paired half steel pipes 21 are joined to the outer peripheries of the upper column portion 10a and the lower column portion 10b from both sides so as to sandwich the columns, and then joined to the surface of the concrete column by inserting bolts 22 into multiple bolt insertion holes 21c provided in the fastening piece portion 21b, screwing in nuts, and tightening them.

[0020] The seismic isolation structure 20 of this embodiment also includes a seismic isolation rubber body 23 interposed between the flanges 21a, 21a of the upper and lower half steel pipes 21, and a plurality of (e.g., eight) support members 24 interposed between the flanges 21a, 21a so as to surround the seismic isolation rubber body 23. In Fig. 1(A), the three support members 24 in the foreground are omitted and are indicated by dashed lines. The seismic isolation rubber body 23 may be a single piece, but in this embodiment it is made of laminated rubber consisting of multiple rubber plates stacked together. Specifically, thin rubber plates or rubber layers are alternately stacked with steel plates, and the rubber layers are constrained by the steel plates, resulting in a laminated structure that is rigid in the vertical direction and flexible in the horizontal direction, providing the necessary seismic isolation performance. Furthermore, because the seismic isolation rubber body 23 has a laminated structure, it can easily accommodate differences in the spacing between the upper and lower columns by changing the number of layers. Note that the seismic isolation rubber body 23 may also be made of only multiple rubber plates stacked together.

[0021] The support material 24 supports the vertical load immediately after the concrete pillar is cut during seismic isolation work, and is strong enough to withstand external forces associated with constant loads such as wind and vibrations caused by passing trains even without the seismic isolation rubber body 23.It is preferable that the support material 24 is configured so that when an earthquake occurs, a difference in displacement occurs between the upper and lower half steel pipes 21 and a force greater than a predetermined value acts on the seismic isolation structure 20, causing the support material 24 to break (deform), and the seismic isolation function provided by the seismic isolation rubber body 23 is exerted. As a specific example, it is conceivable to construct the support member 24 from a deformable metal such as soft iron so that when a force greater than a predetermined level is applied, the support member 24 deforms, thereby realizing the seismic isolation function of the seismic isolation rubber body 23. Alternatively, the support member 24 may be constructed from a material that is difficult to deform, such as steel, so that when a force greater than a predetermined level is applied, the support member 24 comes off from between the flanges 21a, 21a.

[0022] Furthermore, the location (height) of the seismic isolation structure 20 can be anywhere, but generally, the lower the location, the greater the seismic isolation effect. For example, in a structure composed of an electric pole and a beam, or in a concrete column constituting a portal-shaped electric line support structure in which a truss beam 11 is suspended horizontally between the tops of two concrete columns 10A and 10B as shown in Figure 3, the location should be lower than the beam. Also, some structures near substations have parapet walls (approximately 2.5 m high). In such cases, installing the seismic isolation structure 20 lower than the top of the parapet wall often requires the parapet wall to be renovated. Therefore, it is better to install the seismic isolation structure 20 higher than the top of the parapet wall of the concrete column (for example, 2.5 m higher than the top of the track slab).

[0023] As explained above, in the seismic isolation structure 20 of this embodiment, the seismic isolation rubber body 23 is provided midway along the concrete pillar, so that when an earthquake causes shaking of a predetermined magnitude or greater, the seismic isolation function of the seismic isolation rubber body 23 is exerted, thereby suppressing the shaking of the concrete pillar and preventing damage to parts of the concrete pillar (especially the parts close to the foundation). Furthermore, since a support material 24 is provided between a pair of flanges 21a, 21a that sandwich the seismic isolation rubber body 23 from above and below, external forces associated with constant loads such as wind under normal conditions and vibrations when trains pass by are supported by the support material 24, preventing deformation of the seismic isolation rubber body 23 and suppressing deterioration of the seismic isolation rubber body 23.

[0024] Next, a construction procedure for constructing the seismic isolation structure 20 of the above embodiment on a concrete pillar will be described with reference to FIGS. When constructing the seismic isolation structure 20, first, the height position of the seismic isolation structure 20 to be installed on the target concrete column (PC column) is determined (step S1 in Fig. 4). Next, as shown in Fig. 5(A), the flanged half steel pipe 21 is attached to the concrete column 10 at the height position determined in step S1, by positioning it so that the flanges 21a, 21a are spaced apart by a predetermined distance (step S2).

[0025] Next, as shown in Fig. 5(B), the support material 24 is inserted between the flanges 21a, 21a over half the circumference (step S3). After that, as shown in Fig. 5(C), the concrete exposed between the flanges 21a, 21a is cut and removed (step S4). Next, the seismic isolation rubber body 23 is inserted between the flanges 21a from the side where there is no support material 24 (the front in the figure) to create the state shown in Figure 5(D) (step S5). At this time, a jack may be inserted between the flanges 21a to widen the gap before inserting the seismic isolation rubber body 23. Thereafter, a support material 24 is inserted on the side where there is no support material 24 between the flanges 21a, as shown in Figure 5(E) (step S6). This completes the work of attaching the seismic isolation structure 20 to a single concrete column.

[0026] When reinforcing concrete pillars that make up a structure made up of utility poles and beams, it is desirable to provide the seismic isolation structure 20 to all of the concrete pillars that make up the structure, but existing structures vary in the number and spacing of concrete pillars, which in turn result in different characteristics against shaking during an earthquake. Therefore, for example, it is possible to perform structural calculations for the target structure and install the seismic isolation structure 20 on concrete pillars that are particularly important structurally, while omitting the installation of the seismic isolation structure on less important concrete pillars.

[0027] Furthermore, for concrete pillars that do not have a seismic isolation structure, the seismic performance of the entire structure can be improved by combining the seismic isolation structure of this embodiment with other existing seismic control technologies, for example by installing a support wire with a seismic damper between the pillar and the track base (track).

[0028] While the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention. For example, in the above embodiments, a deformable material (mild steel) was given as an example of a material for the support member 24 that breaks (deforms), but the material for the support member 24 is not limited to this, and a brittle material that breaks when a load exceeding a predetermined value is applied, such as mortar, may also be used. Furthermore, although the opposing surfaces of the pair of flanged half steel pipes 21 in the above embodiment are flat, these surfaces may be provided with shallow recesses 21d into which the ends of the support material 24 fit, as shown in Figure 2(C).

[0029] In the above embodiment, the present invention has been mainly described as being applied to a gate-shaped electric line support structure or concrete pole that constitutes a structure such as that shown in FIG. 3. However, the present invention can also be applied to concrete poles that are erected independently and support electric lines such as feeder lines, and further to concrete poles that support electric wires and telephone lines that supply power to ordinary homes. Furthermore, in the above embodiment, the case where the seismic isolation structure of the present invention is applied to an existing concrete pillar has been described, but the seismic isolation structure of the present invention can also be applied to a newly installed concrete pillar. [Explanation of symbols]

[0030] 10, 10A, 10B Concrete pillars 10a Upper pillar 10b Lower column part 20 Seismic isolation structure 21 Flanged half steel pipe 21a flange 21b Fastening piece 21c Bolt insertion hole 22 volts 23 Seismic isolation rubber 24 Support material

Claims

1. A concrete pole erected in the vertical direction to support an overhead electric wire, The upper and lower pillars are separated at a predetermined interval with their axes aligned. A pair of flanged half steel pipes are connected to the lower end of the upper column portion and the upper end of the lower column portion so that the flanges face each other, Between the upper column portion and the lower column portion, a seismic isolation rubber body having an outer shape smaller than that of the flange in a plan view is disposed, A concrete column characterized in that a plurality of support members are arranged between the flanges of the pair of flanged half steel pipes so as to surround the seismic isolation rubber body.

2. 2. The concrete column according to claim 1, wherein the seismic isolation rubber body has a laminated structure of a plurality of rubber plates or a laminated structure in which a plurality of rubber plates and steel plates are alternately laminated.

3. A concrete column as described in claim 1 or 2, characterized in that the support material is made of a deformable material and is configured to deform when a force greater than a predetermined value is applied, thereby enabling the seismic isolation function of the seismic isolation rubber body to be exerted.

4. A concrete column as described in claim 1 or 2, characterized in that the support material is made of a rigid material and is configured so that when a force greater than a predetermined value is applied, it comes off between the flanges and the seismic isolation function of the seismic isolation rubber body is exerted.

5. A concrete column as described in claim 1 or 2, characterized in that the support material is made of a brittle material and is configured to be destroyed when a force greater than a predetermined value is applied, thereby allowing the seismic isolation function of the seismic isolation rubber body to be exerted.

6. A concrete column as described in claim 1 or 2, characterized in that the earthquake-resistant structure consisting of the flanged half steel pipe, the seismic isolation rubber body, and the support material is located at a position higher than the upper end of the parapet wall located on the elevated structure.

7. A method for improving the seismic isolation of a concrete pole for improving the seismic isolation of a vertically erected concrete pole supporting an overhead electric wire, comprising: a position determination step for determining a height position at which the earthquake-resistant structure of the concrete pillar to be reinforced is to be provided; a half steel pipe joining process in which a pair of flanged half steel pipes are joined to the outer circumferential surface of the concrete column to be reinforced at the determined height so that the flanges face each other; a support member attachment step of inserting a support member over half the circumference between the flanges of the pair of flanged half steel pipes; a concrete pillar cutting process for cutting and removing a portion of the concrete pillar corresponding to the space between the flanges of the pair of flanged half steel pipes; a seismic isolation rubber body installation process for inserting a seismic isolation rubber body into the cut portion of the concrete column; a support member attachment step of inserting the support member over the remaining half circumference between the flanges of the pair of flanged half steel pipes; A method for improving the seismic isolation of a concrete pillar, comprising:

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