Concrete column

Abstract

To provide a prestressed concrete column that is unlikely to collapse by its own weight.SOLUTION: A prestressed concrete column 1 includes an elongated body part 2 centrifugally molded from concrete, and a coating part 3 formed of a synthetic resin and covering an outer peripheral surface 2a of the body part 2 over a predetermined range in the longitudinal direction including at least a ground-level part 2c.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a concrete pillar having a main body formed of concrete. [Background technology]

[0002] Conventionally, concrete columns have been pretensioned, prestressed, centrifugally compacted, high-strength concrete columns (hereinafter simply referred to as concrete columns), in which prestressing steel bars are placed in high-strength concrete compacted by centrifugation, and compressive stress is transmitted to the concrete along the entire length of the prestressing steel bars by applying tension to the prestressing steel bars. Concrete columns have a proven track record, characterized by their high durability, due to the protection of the reinforcing steel bars within the dense concrete, which is resistant to neutralization. Furthermore, they are significantly cheaper than steel pipe columns, and have been widely used in Japan. They are used as supports for a wide range of tracks and antennas, including electric train lines, power distribution lines, communication lines, and mobile radio facilities.

[0003] The required performance of concrete pillars is that the above-ground portion is designed to withstand vertical loads based on their own weight, horizontal loads based on wind loads, and moments caused by these loads acting eccentrically on the pillars of road accessories (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-155144 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because concrete columns are concrete structures, they do not have the same toughness as steel supports, and there have been cases where they have been destroyed by impact loads such as car collisions, earthquakes, and typhoons, and have collapsed under their own weight.

[0006] In reality, overhead wires do not collapse due to the inertial force of their own weight during an earthquake (except for those built on viaducts). Most collapses occur due to excessive tension in the overhead wires, caused by buildings or structures collapsing due to seismic forces collapsing onto them, or by building roofs, signs, or greenhouses blown off by strong winds during typhoons getting caught on the wires. Due to the unique design of concrete poles, which use overhead line messenger wires that are stronger than the strength of the poles, the collapse of one pole can easily cause the entire line to collapse. There have also been cases where collapsed concrete poles have crossed roads at ground level, blocking vehicle traffic. Therefore, in addition to disaster prevention and mitigation, it is necessary to prevent collapse due to self-weight failure, in order to ensure evacuation routes.

[0007] The present invention has been made in consideration of these points, and has as its object to provide a concrete pillar that is less likely to collapse under its own weight. [Means for solving the problem]

[0008] The prestressed concrete column described in claim 1 comprises a long main body portion centrifugally formed from concrete, and a coating portion formed from synthetic resin that covers the outer surface of the main body portion over a predetermined longitudinal range including at least the ground-level portion.

[0009] The prestressed concrete column according to claim 2 is the prestressed concrete column according to claim 1, further comprising a base portion located between the outer peripheral surface of the main body portion and the coating portion.

[0010] The prestressed concrete column of claim 3 is a prestressed concrete column of claim 2, in which the coating portion is made of a synthetic resin having physical properties of tensile strength of 15 to 30 MPa and breaking elongation of 200% or more, and is formed to a thickness of 1 to 4 mm via a primer, which is a base portion with adhesive properties.

[0011] A prestressed concrete column according to claim 4 is the prestressed concrete column according to claim 2 or 3, wherein the coating portion and the base portion each have translucency.

[0012] The prestressed concrete column of claim 5 is a prestressed concrete column of claim 1, wherein the coating portion covers the outer surface of the main body portion from the ground level to 2500 mm above ground. [Effects of the Invention]

[0013] According to the present invention, a prestressed concrete column that is less likely to collapse under its own weight can be provided. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are perspective cross-sectional views showing a prestressed concrete column according to an embodiment of the present invention, in which FIG. 1A shows one example and FIG. 1B shows another example. [Figure 2] 1(a) and 1(b) are side views schematically showing a test device for an impact test in an embodiment of the prestressed concrete column. [Figure 3] 10 is a table showing test results of the impact test. [Figure 4] FIG. 2 is a side view schematically showing a test device for a bending test in an embodiment of the prestressed concrete column. [Figure 5] 1 is a table showing the conditions and test results of the bending test of each example and comparative example. [Figure 6] 10 is a graph showing test results of the bending test. [Figure 7] 10 is a graph showing test results of the bending test. [Figure 8] FIG. 10 is an explanatory diagram showing the results of a test on the visibility of the coating portion in an example of the same prestressed concrete column. [Figure 9] FIG. 2 is an explanatory diagram schematically showing a test device for a hammer impact test in an embodiment of the prestressed concrete column. [Figure 10] 10 is a table showing test results of the hammer impact test. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] In Figures 1(a) and 1(b), reference numeral 1 denotes a prestressed concrete column. Hereinafter, the prestressed concrete column 1 will be simply referred to as a concrete column 1. The concrete column 1 is used, for example, as a utility pole, and is formed by covering the outer surface 2a, i.e., the surface, of a concrete main body 2 with a reinforcing coating 3 made of synthetic resin.

[0017] The main body 2 is formed by centrifugal compaction molding and has a circular cross section. That is, the main body 2 is made of centrifugally compacted concrete. In terms of design, the main body 2 has a hollow cross section with a hollow portion 2b formed in the center in order to increase bending strength. For example, the main body 2 is a concrete structure having a design standard strength of 50 to 85 N / mm 2 In this embodiment, the main body 2 is formed in a tapered shape, for example, gradually reducing in diameter from the lower end, which is the base of the concrete column 1, to the upper end, which is the distal end. However, the main body 2 may be formed with at least a straight section with a constant diameter. Tendons are embedded in the main body 2 along the axial direction, which is the longitudinal direction. The tendons apply tension (prestress) to the main body 2. In addition to the tendons, non-tendons and / or spiral reinforcement may also be embedded in the main body 2.

[0018] The coating 3 is a reinforcing coating that covers a predetermined area of ​​the outer peripheral surface 2a of the main body 2. The "predetermined area" refers to the longitudinal region that covers the entire circumferential direction of the outer peripheral surface 2a and includes at least the base area 2c of the main body 2. The coating 3 is formed only on the outer peripheral surface 2a of the main body 2, not on the inner peripheral surface. FIG. 1(a) shows an example in which the coating 3 covers a portion of the vertical range of the main body 2, from the base area 2c. In this example, the coating 3 extends from the base area 2c to a predetermined height above ground, for example, 2500 mm, preferably 2200 mm. This range is set based on the assumption that the source of impact on the concrete pillar 1 is a car collision, flying debris, or drifting debris, and does not include the area where scaffolding bolts for climbing the pillar or various accessories are attached. Furthermore, the coating portion 3 is intended to cover the range from the ground level portion 2c to a predetermined depth underground, for example, 700 mm, preferably 600 mm, but taking into consideration the erection state of the concrete pillar 1, it may be possible not to cover the underground portion.

[0019] 1(b) shows an example in which the coating 3 covers the entire outer surface 2a of the main body 2. In this example, the concrete pillar 1 is assumed to be built in a salt damage area or a special environment where chemical corrosion is a concern, and the coating 3 covers the entire length of the main body 2 to block factors that deteriorate the concrete (such as acid, air, and water).

[0020] In each example, the synthetic resin constituting the coating portion 3 is, for example, a resin having a tensile strength of 15 to 30 N / mm at room temperature (25°C). 2 , preferably 20N / mm 2 As described above, a material having physical properties of 200% or more breaking elongation is used. Furthermore, a material that does not or is unlikely to yellow due to ultraviolet rays is used for the coating 3. As an example, a polyurethane resin is used as the synthetic resin that constitutes the coating 3. However, the synthetic resin that constitutes the coating 3 is not limited to this, and a hard or soft synthetic resin with a breaking elongation of 200% or more is preferably used. The coating 3 may be colored gray to match the color of the main body 2, or may be colored any other color.

[0021] The thickness of the coating 3 is preferably 1 to 4 mm. If it is thinner than 1 mm, the coating 3 cannot fully exert its effect, and if it is 4 mm or thicker, the effect of the coating 3 does not change significantly.

[0022] Furthermore, in order to improve adhesion between the coating portion 3 and the outer peripheral surface 2a of the main body portion 2, the coating portion 3 is formed on the outer peripheral surface 2a of the main body portion 2 via a primer 4. The primer 4 has adhesive properties. Furthermore, the primer 4 has flexibility. Preferably, the primer 4 is made of, for example, an epoxy or urethane base. The primer 4 can be either solvent-based or solventless.

[0023] Preferably, the coating portion 3 and the base portion 4 are translucent, and more preferably transparent, so that the condition of the surface of the main body portion 2 located inside them, particularly the state of cracks, can be visually confirmed from the outside. If a transparent base portion 4 is used, it is preferable to use one that does not or is unlikely to yellow due to ultraviolet rays.

[0024] The concrete pillar 1 is manufactured, for example, by either (1) forming the covering portion 3 after manufacturing the main body portion 2 and erecting the pillar, or (2) forming the covering portion 3 on the main body portion 2 that has already been erected.

[0025] In the above method (1), after the main body portion 2 is centrifugal molded, the base portion 4 is applied to a predetermined area of ​​the outer peripheral surface 2a of the main body portion 2, and the coating portion 3 is applied onto the base portion 4 and hardened to form the coating portion 3.

[0026] In the method (2) above, the base portion 4 is applied to a predetermined area from the ground level of the outer peripheral surface 2a of the erected main body portion 2, and the covering portion 3 is applied to the base portion 4 and hardened to form the covering portion 3.

[0027] Because the concrete pillar 1 manufactured in this way is a concrete structure, it does not have the same toughness as a steel support, and there is concern that it may be destroyed and collapse under its own weight due to, for example, a collision with an automobile, a collision with flying or drifting objects, or an impact load during an earthquake or typhoon. To prevent the concrete pillar 1 from collapsing under its own weight, it is necessary to either prevent brittle fracture or ensure that the concrete pillar 1 can maintain its own weight even if brittle fracture occurs.

[0028] Therefore, in this embodiment, a synthetic resin-molded coating 3 is formed on a long concrete body 2 so as to cover the outer circumferential surface 2a of the body 2 over a predetermined longitudinal range including at least the ground-level portion 2c. Even if the body 2 reaches its plastic region due to a load such as an impact and is destroyed, the coating 3 stretches, and its deformation resistance force maintains the shape of the body 2, making it possible to withstand overloads and provide a concrete column 1 that will not or will not easily collapse under its own weight due to localized destruction. Here, overload mainly refers to impact loads and kinetic loads, and does not include static loads.

[0029] Specifically, in this embodiment, the outer surface 2a of the circular cross section of the main body 2 is covered with the coating portion 3, and the high breaking elongation of the coating portion 3 efficiently absorbs energy during impact, thereby improving impact resistance.

[0030] That is, the coating 3 has the effect of locally dispersing the impact load when a load is input, and this dispersion of the impact load causes low-level damage over a wide area instead of localized crushing of the main body 2, thereby maintaining the independence of the concrete pillar 1. Furthermore, even if part of the concrete in the internal main body 2 is destroyed, the coating 3 wraps around and restrains the fragments, preventing or suppressing the concrete pillar 1 from collapsing under its own weight.

[0031] In particular, concrete pillars 1 often have drainage channels installed near their erection position, meaning that they are in a position where drifting debris is likely to collide with the ground-level portion 2c due to flooding during typhoons and other events. Furthermore, the structure of the ground-level portion 2c is prone to horizontal cracks. Therefore, by covering a predetermined area on the outer surface 2a of the main body 2, including the ground-level portion 2c, with the coating portion 3, even if cracks occur in the main body 2, the coating portion 3 will expand in response to deformation of the main body 2, and will continue to exert its protective effect.

[0032] By providing a base portion 4 between the outer surface 2a of the main body portion 2 and the coating portion 3, the adhesion between the outer surface 2a of the main body portion 2 and the coating portion 3 can be improved, further improving the effect of making the concrete pillar 1 less likely to collapse under its own weight.

[0033] Furthermore, by making the coating portion 3 and the base portion 4 translucent, the surface condition of the main body portion 2 covered by them can be visually observed from the outside. [Example]

[0034] The present example and a comparative example will be described.

[0035] The concrete pillar 1 of this embodiment and a conventional concrete pillar were subjected to an impact test and a bending test, and the results are shown below.

[0036] <Impact test> Impact tests were conducted on Example 1 and Example 2 corresponding to the concrete pillar 1 of this embodiment, and Comparative Example 1 and Comparative Example 2 corresponding to the conventional concrete pillars, using a test device 5 as shown in Figures 2(a) and 2(b).

[0037] Here, the test apparatus 5 is configured by suspending a weight 8 from an upper support 6 by a suspension member 7 such as a wire. The weight 8 is a rectangular box made of, for example, steel plate, filled with concrete and set to a predetermined weight, for example, 1 ton. As shown in FIG. 2(a), with the suspension member 7 stretched, the weight 8 is lifted from its lowest position corresponding to the ground level 2c until its center of gravity G reaches a predetermined height H. The weight 8 is then set to strike the test specimen at its lowest point by causing a pendulum motion due to gravity, as shown in FIG. 2(b).

[0038] The conditions and test results for Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are shown in the table of Figure 3. In the figure, the physical properties of the material of the coating portion 3 are those at room temperature (25°C). Note that, except for Comparative Example 2, each test was conducted twice, and the number indicating the number of tests is added to the end with a hyphen. For example, "Example 1-2" indicates the data of Example 1 used in the second test.

[0039] In Examples 1 and 2, although the concrete of the main body 2 at the impact point was partially destroyed upon impact, it was restrained by the coating 3, and no clear damage was observed on the other side of the impact, and both remained upright, whereas in Comparative Examples 1 and 2, the concrete of the entire cross section at the impact point collapsed upon impact, and the inertial force of the weight 8 caused the part above the impact point to be pushed by the weight 8 and move, leading to collapse. As a result, it was confirmed that the concrete column 1 of this embodiment has the effect of dispersing the impact load and preventing major breakage due to the coating 3, and it was confirmed that it has improved impact resistance and the ability to prevent damage and collapse under its own weight due to the restraint effect.

[0040] <Bending test and examination of the material of the coating part 3> For Examples 3 to 5 corresponding to the concrete pillar 1 of this embodiment and Comparative Example 3 corresponding to the conventional concrete pillar, bending tests were conducted using a test device 10 as shown in FIG. 4 based on the cantilever beam loading method specified in JIS A 5363.

[0041] Here, in the test device 10, a pillow material 13 is placed inside a cylindrical fixed base 11 via a jack 12, and the pillow material 13 is pressed by the jack 12 against the butt end, i.e., near the base end, of the test specimen, for example, at a position 100 mm from the base end, and at a predetermined support point position from the base end, to support the test specimen. In this state, a load F is applied in a direction perpendicular to the axis of the test specimen to the end end, i.e., near the top, of the test specimen, for example, at a loading point 250 mm from the top, and the load F at the time of failure and the top displacement δ of the test specimen are measured.

[0042] Example 3 was the same as Example 1, and Example 4 was the same as Example 1 except that the area in which the coating portion 3 was formed was the entire outer peripheral surface 2a of the main body portion 2. Comparative Example 3 was the same as Comparative Example 1. The conditions for Examples 3 and 4 are shown in the table of FIG. 5, and the results of the bending test are shown in the table of FIG. 5 and the graph of FIG. 6. In the figure, the physical properties of the material of the coating portion 3 are those at room temperature (25°C).

[0043] In Examples 3 and 4, no significant difference in breaking load was confirmed compared to Comparative Example 3. In other words, no improvement in yield strength (rigidity) due to the coating portion 3 was confirmed.

[0044] On the other hand, in Examples 3 and 4, the apex displacement at the time of fracture was larger than that in Comparative Example 3. That is, it was confirmed that the coating portion 3 tends to increase the apex displacement.

[0045] The results of the impact test and bending test above show that the coating portion 3 of this embodiment makes the concrete pillar 1 less likely to collapse under its own weight.

[0046] Moreover, Example 5 was the same as Example 3, except that the material of the coating portion 3 was changed to a soft material. The conditions are shown in FIG.

[0047] In order to confirm the residual strength, loading was continued after the specimens were broken for Examples 3 to 5. The outline and results of the bending test are shown in the table of FIG. 5 and the graph of FIG.

[0048] In Example 4, no residual strength was confirmed after the destruction of the main body 2, but in Examples 3 and 5, a strength of approximately 0.6 kN remained even after the destruction of the main body 2 until the top displacement reached 2000 mm.

[0049] Furthermore, in Example 5, no fracture of the tendons (reinforcing bars) occurred when the main body 2 was destroyed, and immediately thereafter the load dropped to 2.8 kN due to the collapse of the main body 2. As the load continued, ductile fracture progressed gradually, and the yield strength at a top displacement of 1500 mm fell to 1 kN or less. After that, because concrete fragments were packed on the compression side of the main body 2, the yield strength was maintained at around 0.6 kN up to a top displacement of 2000 mm. In Example 5, no damage occurred to the coating 3 until the end of the test. This is thought to be due to the larger fracture elongation of the material of the coating 3 compared to Example 3.

[0050] As described above, regarding the material of the coating 3, although the hard one had a larger top displacement before the main body 2 broke, the soft one had a larger breaking elongation, and no damage occurred to the coating 3 even after the main body 2 broke, and the restraint effect around the broken cross section was maintained, allowing the main body 2 to support its own weight even after breaking, demonstrating that it was more advantageous than the hard one in terms of collapse resistance. In other words, it was shown that the magnitude of the breaking elongation of the coating 3 has an effect on collapse resistance.

[0051] <Test for visibility of coated area> A transparent coating 3 with a thickness of 2 mm or more was formed on a plastic crack scale, and an investigation was conducted to determine whether the crack scale markings were visible. As shown in Figure 8, the thinnest markings, 0.05 mm wide, were visible.

[0052] Therefore, it was confirmed that the surface condition of the main body 2 covered with the coating 3 could be visually observed from the outside.

[0053] <Hammer impact test> Examples 6 and 7 corresponding to the concrete pillar 1 of this embodiment and Comparative Example 4 corresponding to the conventional concrete pillar were placed sideways on the ground as shown in Figure 9, and a hammer HM of 4.5 kg (approximately 10 pounds) was swung down from a predetermined height H, for example, 1.6 m above the ground, to conduct an impact test and compare the damage conditions.

[0054] In Example 6, a transparent coating 3 was formed to a thickness of 1.7 mm on a main body 2 having a diameter of 300 mm and formed from centrifugally compacted concrete, similar to the specimen specified in JIS A 1136. In Example 7, a non-transparent coating 3 was formed to a thickness of 2.0 mm on a main body 2 similar to that of Example 6. On the other hand, Comparative Example 4 was made of concrete without a coating, corresponding to the main body 2 of Examples 6 and 7.

[0055] The test results are shown in Figure 10. As shown in Figure 10, Comparative Example 4 fractured into four pieces after one hit, whereas Examples 6 and 7 were able to withstand up to four hits. In Example 6, the fifth hit caused the coating 3 to rupture in the impacted area and the concrete in the main body 2 to collapse. In Example 7, the coating 3 on the horizontal side of the coating 3 to tear, and the concrete in the main body 2 to crack.

[0056] This indicates that the coating 3 improves the impact resistance. [Explanation of symbols]

[0057] 1. Prestressed concrete columns 2 Main body 2a Outer surface 2c Ground area 3 Coating part 4 Base

Claims

1. a long main body portion centrifugally formed from concrete; a coating portion formed of a synthetic resin and covering an outer peripheral surface of the main body portion over a predetermined range in the longitudinal direction, including at least a ground portion; A prestressed concrete column comprising:

2. A base portion is provided between the outer circumferential surface of the main body portion and the coating portion.

2. The prestressed concrete column according to claim 1.

3. The coating is made of a synthetic resin with physical properties of tensile strength of 15 to 30 MPa and elongation at break of 200% or more, and is formed with a thickness of 1 to 4 mm via a primer, which is a base layer with adhesive properties.

3. A prestressed concrete column according to claim 2.

4. The coating portion and the base portion are each translucent.

4. A prestressed concrete column according to claim 2 or 3.

5. The coating covers the outer periphery of the main body from the ground to 2500 mm above ground.

2. The prestressed concrete column according to claim 1.

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