Pillar reinforcement structure and pillar reinforcement method

Abstract

To reinforce a column body with easier work. [Solution] The column reinforcement structure is a reinforcement structure for a roughly cylindrical column with PC steel embedded in it, and comprises: a first filling material filled inside the column, which is erected with its lower part buried; a first reinforcing member arranged along the outer periphery of the lower side of the column, leaving a gap between it and the column; and a second reinforcing member arranged alongside the first reinforcing member above the position of the first reinforcing member on the column, and reinforcing the column relatively more strongly than the reinforcement provided by the first reinforcing member.

Description

[Technical Field]

[0001] The present invention relates to a reinforcement structure for a pillar body and a reinforcement method for a pillar body. [Background technology]

[0002] In the event of an earthquake, the concrete in prestressed concrete (PC) electrification poles may undergo compressive failure and brittle failure. In response to this, for PC electrification poles (also simply referred to as "electrification poles") used on Shinkansen viaducts and bridges, for example, a method has been proposed in which the existing PC steel members (also referred to as "PC steel") are cut in advance and reinforcing steel bars are installed around the periphery instead (also referred to as the "first conventional method") (see, for example, Patent Document 1).

[0003] The first conventional method described above aims to avoid compressive failure and improve the deformation performance of the utility pole by absorbing energy through the yielding of the reinforcing steel bars. A method (also called the "second conventional method") has also been proposed in which the strength of the utility pole itself is improved by filling the interior of the utility pole with mortar and installing reinforcing steel plates around the periphery (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-055764 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-037764 [Non-patent literature]

[0005] [Non-Patent Document 1] Daisuke Tsukishima, Takato Sasaki, Hideaki Kusano: “Seismic reinforcement of PC electrification poles on viaducts”, Proceedings of the Japan Concrete Institute, Vol. 38, No. 2, pp. 1087-1092, July 2016 [Non-patent document 2] Michitoshi Iwata, Kazunori Watanabe, Hideaki Kusano, Shinichiro Nozawa: “Seismic reinforcement method for PC electrification poles”, SED, No. 39, pp. 152-161, May 2012 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of the first conventional method described in Patent Document 1, cutting the prestressing steel takes one-third (one day) of the current total construction process (three days), making it extremely time-consuming to apply to the large number of utility poles that require countermeasures. Furthermore, if the second conventional method described in Patent Document 2 increases the strength of the utility pole, the base of the utility pole may become a new weak point. Therefore, the introduction of this method requires verifying the safety of the base of the utility pole and designing reinforcement, which takes time and makes it practically difficult to implement. Thus, for both conventional methods, there is a need to reduce the number of days (time) required for construction. There is room for improvement in terms of time and other costs, and there is a need for easier column reinforcement work.

[0007] An object of the present invention is to reinforce a column body with easier work. [Means for solving the problem]

[0008] The reinforcement structure for a column body according to the present invention is a reinforcement structure for a substantially cylindrical column body in which PC steel is embedded, and comprises: a first filling material filled inside the column body, which is erected with its lower part buried; a first reinforcing member arranged along the outer periphery of the lower side of the column body, leaving a gap between the first reinforcing member and the column body; and a second reinforcing member arranged alongside the first reinforcing member above the position of the first reinforcing member on the column body, and reinforcing the column body relatively more strongly than the reinforcement provided by the first reinforcing member. [Effects of the Invention]

[0009] According to the present invention, there is an effect that the column body can be reinforced with easier work. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing a pillar body reinforcement structure according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along the line BB in FIG. [Figure 4] FIG. 4 is a diagram showing an overview of each case. [Figure 5] FIG. 5 shows the specifications of the test specimen of the existing utility pole. [Figure 6] FIG. 6 is a diagram showing design values ​​of materials used. [Figure 7] FIG. 7 shows the specifications of the test specimens for each case. [Figure 8] FIG. 8 is a diagram showing the moment-displacement relationship in Case A. [Figure 9] FIG. 9 is a diagram showing the moment-displacement relationship in Case B. [Figure 10] FIG. 10 is a diagram showing the moment-displacement relationship in Case C. [Figure 11] FIG. 11 is a diagram showing the moment-displacement relationship in case D. [Figure 12] FIG. 12 shows the relationship between the load displacement and the vertical displacement of the base in each case. [Figure 13] FIG. 13 is a diagram showing a method for decomposing displacement components. [Figure 14] Figure 14 shows the amount of δextend and δnon-extend with respect to the loading displacement for each case. [Figure 15] FIG. 15 is a diagram showing the envelope of the moment-displacement relationship. [Figure 16] FIG. 16 is a diagram showing the calculation results of the toughness rate. DETAILED DESCRIPTION OF THE INVENTION

[0011] A stealing method according to an embodiment of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiment described below.

[0012] [Column reinforcement structure] First, a column reinforcement structure 100, which is an example of a column reinforcement structure, will be described using Figure 1. Figure 1 is a cross-sectional view showing a column reinforcement structure according to an embodiment. Figure 1 describes a reinforcement structure for an electricity pole 10, which is a column that is erected with its lower part 13 buried in a base part BS, as an example of the column reinforcement structure 100. For example, the column reinforcement structure 100 shown in Figure 1 is a reinforcement structure for providing earthquake-resistant reinforcement for the electricity pole 10. The base part BS may be a foundation part (main girder) or the like provided on a pier erected from the ground in a Shinkansen viaduct or the like. Note that the base part BS is not limited to the above, and may be anything, such as the ground, as long as it is capable of supporting a column such as an electricity pole 10 that is erected by being buried.

[0013] The utility pole 10 is a substantially cylindrical concrete pole with PC steel 11 embedded therein. The utility pole 10 has an interior 12, which is a space that penetrates the utility pole 10 in the axial direction (height direction). In FIG. 1, the column reinforcement structure 100 has an interior filling member 20 including a first filling material 22, a first reinforcing member 30, a second reinforcing member 40, a second filling material 50, and a third filling material 60.

[0014] An internal filling member 20 is disposed in the interior 12 of the utility pole 10. The internal filling member 20 has a bag member 21 and a first filling material 22. The bag member 21 is a bag-shaped member capable of holding the first filling material 22 inside. For example, the bag member 21 is formed by weaving a fiber material such as a fiber sheet into a bag shape. The bag member 21 can have any configuration, such as a tubular bag. For example, the first filling material 22 is mortar such as non-shrink mortar. The first filling material 22 is filled into the interior 12 of the utility pole 10 in a fluid state and then hardened to form the first filling material 22. The first filling material 22 is not limited to mortar, and any material may be used as long as it fulfills the desired function.

[0015] As shown in FIG. 1 , the internal filling member 20 fills the interior 12 of the pole 10 in a range that includes the area where the pole 10 is surrounded by a second reinforcing member 40, which will be described later. For example, a bag member 21 is inserted into the interior 12 of the pole 10 through a through-hole HD provided in a part of the pole 10, and the first filler material 22 is injected into the bag member 21, thereby filling the interior 12 of the pole 10 with the first filler material 22; this will be described later. The internal filling member 20 placed in the interior 12 of the pole 10 can have any configuration as long as it can fill the interior 12 of the pole 10 with the first filler material 22. For example, the internal filling member 20 may not have a bag member 21 and may only contain the first filler material 22. In this case, the interior 12 of the pole 10 may be filled with only the first filler material 22.

[0016] The first reinforcing member 30 is arranged along the outer periphery of the lower portion 13 of the utility pole 10, with a gap between it and the utility pole 10. For example, the first reinforcing member 30 has a size of 350 mm in the axial direction (height direction) of the utility pole 10. Note that 350 mm is merely an example, and the size of the first reinforcing member 30 in the axial direction (height direction) of the utility pole 10 can be set to any value depending on the size of the utility pole 10, etc. The first reinforcing member 30 is arranged with its lower end close to the surface SR of the foundation portion BS. Note that while FIG. 1 shows a state in which there is a gap between the surface SR, which is at ground level, and the lower end of the first reinforcing member 30, there need not be a gap between the surface SR and the lower end of the first reinforcing member 30.

[0017] Furthermore, the second reinforcing member 40 is arranged next to the first reinforcing member 30 above the location of the first reinforcing member 30 on the utility pole 10. In this way, the first reinforcing member 30 and the second reinforcing member 40 are reinforcing members arranged next to each other along the axial direction of the utility pole 10. For example, the second reinforcing member 40 has a size of 600 mm in the axial direction (height direction) of the utility pole 10. Note that 600 mm is just one example, and the size of the second reinforcing member 40 in the axial direction (height direction) of the utility pole 10 can be set to any value depending on the size of the utility pole 10, etc.

[0018] As shown in FIG. 2, the first reinforcing member 30 is arranged so as to surround the outer periphery of the utility pole 10. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. For example, a steel pipe is used for the first reinforcing member 30. The first reinforcing member 30 is a steel pipe (also referred to as a "lower steel pipe") that is arranged below the second reinforcing member 40. For example, a steel pipe having a steel plate thickness (thickness) in the range of 1.6 to 6.4 mm is used for the first reinforcing member 30. The thickness of the steel plate used for the first reinforcing member 30 is not limited to the above range, and may be any value as long as it satisfies the desired function. Specific examples of the steel plate thickness of the first reinforcing member 30 will be described later.

[0019] For example, the first reinforcing member 30 is formed in a circular shape with a diameter in the range of 413.2 to 457.2 mm in the cross section shown in Fig. 2. Note that the diameter of the cross section of the first reinforcing member 30 is not limited to the above range and may be any value, as long as the first reinforcing member 30 can be arranged to surround the outer periphery of the utility pole 10. Note that specific examples of the diameter of the cross section of the first reinforcing member 30 will be described later. Also, while Fig. 2 illustrates the first reinforcing member 30 as a continuous circle, the first reinforcing member 30 may be in any form, such as two or more separate members connected together, as long as the first reinforcing member 30 can be arranged to surround the outer periphery of the utility pole 10; this will be described later.

[0020] As shown in FIG. 3, the second reinforcing member 40 is arranged to surround the outer periphery of the utility pole 10. FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1. For example, a steel pipe is used for the second reinforcing member 40. The second reinforcing member 40 is a steel pipe (also referred to as an "upper steel pipe") that is arranged above the first reinforcing member 30. For example, a steel pipe with a steel plate thickness (thickness) of 6.4 mm is used for the second reinforcing member 40. Note that the thickness of the steel plate used as the second reinforcing member 40 is not limited to the above, and may be any value as long as it satisfies the desired function.

[0021] As shown in FIG. 1, a gap is provided between the first reinforcing member 30 and the second reinforcing member 40 along the axial direction of the utility pole 10. In FIG. 1, a gap (gap) with a gap amount V1 is provided between the first reinforcing member 30 (upper end) and the second reinforcing member 40 (lower end) in the axial direction of the utility pole 10. For example, the gap amount V1 is 20 mm. Note that 20 mm is merely an example, and the value of the gap amount V1 can be set to any value that satisfies the desired function. In this way, by providing a gap (gap) between the first reinforcing member 30 and the second reinforcing member 40, the column body reinforcing structure 100 can prevent unexpected interactions from occurring due to contact between the first reinforcing member 30 and the second reinforcing member 40 when deformation of the utility pole 10 occurs due to load.

[0022] As shown in Figures 1 and 2, a gap is provided between the first reinforcing member 30 and the utility pole 10. In Figure 2, a gap (gap) of gap amount V2 is provided in the radial direction (width direction) of the utility pole 10 between (the inner peripheral surface of) the first reinforcing member 30 and (the outer peripheral surface of) the utility pole 10. For example, gap amount V2 is set in the range of 5.0 to 22.2 mm. Note that gap amount V2 is not limited to the above range and may be any value as long as it satisfies the desired function.

[0023] A gap of gap V2 between the first reinforcing member 30 and the utility pole 10 is filled with a second filler 50. For example, the second filler 50 may be urethane foam or the like. The second filler 50 is filled in a fluid state between the utility pole 10 and the first reinforcing member 30 and then hardened to form the gap. The second filler 50 is not limited to urethane foam, and any material may be used as long as it satisfies the desired function. Also, while FIG. 2 shows a case in which the second filler 50 is disposed around the entire circumference of the gap between the first reinforcing member 30 and the utility pole 10, the second filler 50 may be disposed in only a portion of the gap between the first reinforcing member 30 and the utility pole 10. For example, the second filler 50 may be disposed around a portion of the entire circumference of the gap between the first reinforcing member 30 and the utility pole 10, and other locations may be spaces (gap) where the second filler 50 is not disposed. Specific examples of the gap amount V2 and the arrangement of the second filler 50 will be described later.

[0024] As shown in Figures 1 and 3, a gap is provided between the second reinforcing member 40 and the utility pole 10. In Figure 3, a gap (gap) of gap amount V3 is provided in the radial direction (width direction) of the utility pole 10 between (the inner peripheral surface of) the second reinforcing member 40 and (the outer peripheral surface of) the utility pole 10. For example, gap amount V3 is set to 22.2 mm. Note that gap amount V3 is not limited to the above and may be any value as long as it satisfies the desired function.

[0025] For example, the second reinforcing member 40 is formed in a circular shape with a diameter of 457.2 mm in the cross section shown in Fig. 3. Note that the diameter of the cross section of the second reinforcing member 40 is not limited to the above and may be any value, as long as the second reinforcing member 40 can be arranged so as to surround the outer periphery of the utility pole 10. For example, if the diameter of the utility pole 10 in the cross section shown in Fig. 3 is 400 mm, the second reinforcing member 40 is formed in a range that surrounds the outer periphery of the utility pole 10 and allows for a gap to be provided (a circular shape with a diameter greater than 400 mm).

[0026] A third filler 60 is filled into the gap of gap V3 between the second reinforcing member 40 and the utility pole 10. For example, mortar or the like is used as the third filler 60. The third filler 60 is filled in a fluid state between the utility pole 10 and the second reinforcing member 40, and then hardened to form the gap. The third filler 60 is not limited to mortar, and any material may be used as long as it fulfills the desired function. The third filler 60 may be placed in part of the gap between the second reinforcing member 40 and the utility pole 10, similar to the second filler 50.

[0027] The second reinforcing member 40 reinforces the utility pole 10 relatively more strongly than the reinforcement provided by the first reinforcing member 30. The second reinforcing member 40 is controlled by setting the components related to the second reinforcing member 40 so as to reinforce the utility pole 10 relatively more strongly than the reinforcement provided by the first reinforcing member 30. For example, the second reinforcing member 40 is controlled by setting (selecting) at least one of the gap amount V3, the second filler 50 placed in the gap between the utility pole 10 and the utility pole 10, the size in the axial direction (height direction) of the utility pole 10, the thickness (steel plate thickness), etc.

[0028] In Fig. 3, the second reinforcing member 40 is shown as being continuous in a circle, but the second reinforcing member 40 may be in any form, such as two or more separate members connected together, as long as it can be arranged to surround the outer periphery of the utility pole 10; this will be described later. In addition, the example shown in Figs. 2 and 3 shows a case in which a total of 30 prestressing steels 11, consisting of 24 tension steels 11a and 8 non-tension steels 11b, are embedded in the utility pole 10. In Figs. 2 and 3, the tension steels 11a and non-tension steels 11b are shown separately, but when no distinction is made between them, they will be referred to as "PC steels 11."

[0029] [Method of reinforcing the column body] Next, an example of a column reinforcement method will be described. Below, a method for reinforcing an electricity pole 10 in which the lower part 13 is buried in the base part BS and erected will be described, which is a method for constructing a column reinforcement structure 100. Note that explanations of points similar to those described above will be omitted as appropriate. Furthermore, the order of explanation below shows an example of the order of work (processing) of each step of the reinforcement method, and the order in which each step is performed is not limited to the order described below, and may be performed in any order. In other words, each step of the reinforcement method may be performed in an appropriate interchangeable order to the extent that the step is practicable. Furthermore, if multiple steps of the reinforcement method can be performed in parallel, the multiple steps may be performed in parallel.

[0030] The method for reinforcing an electric pole 10 includes a first filling step, which is a step of filling the interior 12 of the electric pole 10 with a first filler material 22. For example, the first filling step involves drilling a portion of the existing electric pole 10, and filling the interior 12 of the electric pole 10 with a first filler material 22 such as mortar through the through hole HD created by the drilling. In this way, the first filling step involves drilling a portion of the existing electric pole 10, and filling the interior 12 of the electric pole 10 with the first filler material 22 through the drilled portion (through hole HD). Note that in FIG. 1 , for convenience of illustration, the through hole HD overlaps with the prestressing steel 11, but the through hole HD is provided in a location in the circumferential direction of the electric pole 10 where there is no prestressing steel 11.

[0031] As described above, when the bag member 21 is used to fill the interior 12 of the electricity pole 10, the bag member 21 is inserted into the interior 12 of the electricity pole 10 through the through hole HD, and the first filler 22 is injected into the bag member 21, thereby filling the interior 12 of the electricity pole 10 with the first filler 22. In this way, in the first filling step, the bag member 21 is first inserted into the interior 12 of the electricity pole 10, and the bag member 21 is filled with the first filler 22, or only the first filler 22 is filled.

[0032] The method for reinforcing an electricity pole 10 includes a first arrangement step of arranging a first reinforcing member 30 along the outer periphery of the lower portion 13 of the electricity pole 10, with a gap provided between the first reinforcing member 30 and the electricity pole 10. The method for reinforcing an electricity pole 10 also includes a second arrangement step of arranging a second reinforcing member 40, which is stronger than the first reinforcing member 30, next to the first reinforcing member 30 above the location of the first reinforcing member 30 on the electricity pole 10. For example, in the method for reinforcing an electricity pole 10, the first reinforcing member 30, which is a lower steel plate, and the second reinforcing member 40, which is an upper steel plate, which are divided into two in the height direction, are installed on the outer periphery of the electricity pole 10.

[0033] The diameter (inner diameter) of the first reinforcing member 30, which is a lower steel plate, is formed to be approximately 10 mm larger than the diameter (outer diameter) of the utility pole. The first reinforcing member 30, which is a lower steel plate, is formed by integrating two semicircular halves of a member, which are split into two halves in a plan view (cross-sectional view of FIG. 2), with bolts. The first reinforcing member 30 may be, for example, a semicircular member formed by bending a steel plate.

[0034] The diameter (inner diameter) of the second reinforcing member 40, which is an upper steel plate, is formed to be large enough relative to the diameter (outer diameter) of the utility pole 10 so that mortar can be filled without any problems. The second reinforcing member 40, which is an upper steel plate, is formed by integrating two semicircular halves of the member in a plan view (cross-sectional view in FIG. 3) with bolts. The second reinforcing member 40 may be, for example, a semicircular member formed by bending a steel plate.

[0035] In the first and second placement steps, a gap is provided between the first reinforcing member 30 and the second reinforcing member 40 in the height direction, thereby preventing contact between the first reinforcing member 30 and the second reinforcing member 40 due to deformation of the utility pole 10. For example, in the second placement step, the second reinforcing member 40 is placed with a gap provided between the first reinforcing member 30 and the second reinforcing member 40 along the axial direction of the utility pole 10. Note that if the first placement step is performed after the second placement step, the first placement step places the first reinforcing member 30 with a gap provided between the second reinforcing member 40 and the first reinforcing member 30 along the axial direction of the utility pole 10.

[0036] The method for reinforcing an electricity pole 10 includes a second filling step of filling the gap between the first reinforcing member 30 and the electricity pole 10 with a second filler 50. In the second filling step, the gap between the first reinforcing member 30, which is the lower steel plate, and the electricity pole 10 is left partially empty, or the entire periphery is filled with a second filler 50 such as a foamed material with low rigidity.

[0037] The method for reinforcing an electricity pole 10 includes a third filling step of filling a gap provided between the second reinforcing member 40 and the electricity pole 10 with a third filler 60. The third filling step integrates the second reinforcing member 40 and the electricity pole 10 by filling the entire periphery of the gap between the second reinforcing member 40 and the electricity pole 10 with the third filler 60 such as mortar.

[0038] The pole reinforcement structure 100 is completed and the reinforcement of the utility pole 10 is completed by the reinforcing method for the utility pole 10, which includes the first filling step, the second filling step, the third filling step, the first arranging step, and the second arranging step as described above. Note that the reinforcing method for the utility pole 10 described above is merely one example, and the reinforcing method for the utility pole 10 may be a variety of steps as long as the desired reinforcement is possible. For example, the reinforcing method for the utility pole 10 may be a reinforcing method having any steps as long as it includes the first filling step, the first arranging step, and the second arranging step.

[0039] 〔effect〕 The above-described reinforcement structure and reinforcement method allow the column body of the utility pole 10 to be reinforced with easier work. The above-described reinforcement structure and reinforcement method allow the column body to be reinforced without cutting the existing PC steel. In other words, the above-described reinforcement structure and reinforcement method eliminate the need to cut the existing PC steel, and therefore can reduce the number of construction days compared to conventional construction methods (for example, from three days to two days).

[0040] Furthermore, the above-described reinforcement structure and reinforcement method combine filling the interior of the utility pole with reinforcing material and installing reinforcing steel plates divided along the pole's height along its periphery. By controlling the size of the gap between the reinforcing steel plate and the utility pole and the amount of filler material in the gap, relative weak spots can be located in the divided lower reinforcing steel plate sections. As a result, the above-described reinforcement structure and reinforcement method can, for example, cause compressive failure of the utility pole concrete at the weak spot, and then restrain the compressed concrete from both inside and outside with the filled reinforcing material and the periphery reinforcing steel plates, thereby imparting deformation performance equivalent to that of conventional construction methods without increasing the strength. Because the above-described reinforcement structure and reinforcement method do not increase the strength of existing utility poles, there is no need to consider the safety of the utility pole foundation.

[0041] [Experimental results] Hereinafter, experimental results (test results) using the above-described configuration will be described. First, an outline of the experiment (test) from which the following experimental results were obtained will be described. Note that explanations of points similar to those described above will be omitted as appropriate.

[0042] Figure 4 shows an overview of the four cases in which the following experiments were conducted. Figure 4 is a diagram outlining each case. As shown in Figure 4, in the experiments described below, test specimens corresponding to each of Cases A to D were fabricated and used for the experiments. Figure 5 also shows an existing utility pole. Figure 5 is a diagram showing the specifications of the test specimen for the existing utility pole. The specifications of the existing utility pole were based on the previous study in Non-Patent Document 1. The PC utility pole used as the existing utility pole is model 12-40-N150B, and is manufactured to have a breaking load of at least twice the design value (150 kN m) (300 kN m). Hereinafter, 300 kN m may be referred to as the design breaking strength. For example, in the loading test in Non-Patent Document 2, the design breaking strength was exceeded, resulting in compressive failure of the concrete.

[0043] As shown in Fig. 4, this pole was cut to a length of 2650 mm, and the opposite side of the cut surface was embedded 500 mm into the footing and fixed with mortar. The length from the base of the pole to the loading point was 2000 mm.

[0044] The design values ​​of the materials used are shown in Figure 6. Figure 6 is a diagram showing the design values ​​of the materials used. The internal mortar was filled by drilling a hole in a part of the utility pole and inserting a bag-shaped fiber sheet inside. The upper steel pipe was 600 mm high and had a steel plate thickness of 6.4 mm, and the gap with the concrete was filled with mortar. The reinforcement was determined so as not to cause damage to the footing. The compressive strength of the utility pole concrete and the specifications of the lower steel pipe for each case are also shown in Figure 7. Figure 7 is a diagram showing the specifications of the test specimen for each case.

[0045] In Cases A and B, in order to understand the effect of the gap between the steel pipe and the concrete on behavior during compressive failure, the gap was set to 22.2 mm and 5.0 mm, respectively, and urethane foam was used as the filler. This is because the steel pipe does not constrain the concrete until compressive failure, preventing an increase in the pole's strength. To ensure sufficient constraining effect after compressive failure, the steel plate thickness was increased to approximately 6 mm. For example, the steel pipe with a diameter that results in a gap of 5.0 mm in Case B was manufactured by bending a steel plate of that thickness.

[0046] In Cases C and D, the steel plate thickness was reduced to 1.6 mm compared to Case B in order to understand the effect of steel plate thickness on behavior after compressive failure. In Case C, no filler was used, and 5 mm thick polystyrene foam was placed only in the 90-degree range centered on the direction perpendicular to the loading direction. This resulted in a complete 5 mm gap in the loading direction. In Case D, the entire periphery was filled with cement paste.

[0047] An alternating positive and negative load test was conducted on each specimen in cases A to D. The loading conditions were the same as those in the loading test in Non-Patent Document 1, with a reference displacement of 30 mm and repeated loads of one positive and one negative, gradually increasing in integral multiples. No axial force was applied. Loading was continued until the load had sufficiently decreased, resulting in a load of ±240 mm for cases A to C and ±180 mm for case D.

[0048] Figure 8 shows the relationship between the load point displacement and the moment at the base in the Case A test. Figure 8 illustrates the moment-displacement relationship for Case A. For example, the moment is the product of the applied load and the loading point height (2.0 m). For comparison, Figure 8 also includes the test results (without reinforcement) of an unreinforced PC utility pole from Non-Patent Document 2. During the test, an impact sound was heard at a load displacement of +88 mm, and the moment dropped sharply from 444 kN·m to 314 kN·m. Subsequently, when the load was applied to the negative side at -88 mm, a similar load drop occurred, although no impact sound was heard. Further loading resulted in two slight load drops, accompanied by impact sounds, at -19 mm and -236 mm.

[0049] Furthermore, although not shown in the figure, the lower steel pipe was deformed into an elliptical shape in plan view after the test in Case A. The concrete of the electric pole was crushed throughout the entire lower steel pipe, but only minor horizontal cracks occurred in the upper steel pipe. The prestressing tendons buckled in the direction normal to the pipe approximately 150 mm above the base, and two tendons near the outermost edge on the positive side were fractured. This is presumably associated with the impact sound and load drop at load displacements of -196 mm and -236 mm, and the prestressing tendons are thought to have fractured due to tensile force. Based on these findings, the load drop at ±88 mm is believed to be due to compressive failure of the concrete. Although the internal mortar was also crushed, the fiber sheet showed no fractures or cracks. This suggests that the internal mortar maintained its original shape even after damage, and, together with the steel pipe, constrained the concrete from both inside and outside.

[0050] From the above, in Case A, the concrete in the lower steel pipe section failed in compression as expected. Although the load decreased below the design fracture strength at the time of compressive failure, the load was maintained at approximately the design fracture strength until the PC tendon fractured. The reason for the large load decrease is thought to be that the gap between the concrete and the lower steel pipe was large at 22.2 mm, which meant that the concrete that had failed in compression was not sufficiently restrained.

[0051] Next, Figure 9 shows the relationship between the load point displacement and the moment at the base in the Case B test. Figure 9 illustrates the moment-displacement relationship for Case B. As shown in Figure 9, the behavior of Case B up to the maximum load is very similar to Case A. At a load displacement of +90 mm, an impact sound was heard and the load dropped from 387 kN·m to 346 kN·m. Given the similarity to Case A, it is believed that compressive failure occurred at this point. However, the amount of load drop was less than in Case A. This is thought to be because the small gap meant that the concrete that had compressed and failed was immediately restrained by the steel pipe, further suppressing the decrease in the concrete's compressive resistance. The load was generally maintained after compressive failure, and at +173 mm, an impact sound was heard and a slight load drop occurred. This is thought to be the first time that the tension-side prestressing steel member fractured. After that, impact sounds and load drops associated with fracture occurred intermittently.

[0052] Furthermore, although not shown in the figure, the deformation of the lower steel pipe after the test in Case B was smaller than in Case A. The PC steel had buckled and broken in the tangential direction of the steel pipe about 150 mm above the base, and it was apparent that the steel pipe was restricting deformation. Damage to the internal mortar was less severe than in Case A.

[0053] Next, Figure 10 shows the relationship between the load point displacement and the moment at the base in the Case C test. Figure 10 illustrates the moment-displacement relationship for Case C. As shown in Figure 10, in Case C, a load drop of approximately 10-20% occurred around ±90 mm, and it is believed that compressive failure occurred at this point. The amount of load drop was similar to that in Case B, and considering the results of Cases A and B, a correlation can be seen between the gap size and the amount of load drop. After compressive failure, the load was maintained until the end of loading at ±180 mm. At +209 mm, an impact sound was heard and the load dropped from 340 kN·m to 273 kN·m, which is believed to be the first time that the prestressing tendon fractured. After that, intermittent load drops occurred due to fracture.

[0054] Furthermore, although not shown in the figure, in the post-test state of Case C, unlike Cases A and B, the lower steel pipe buckled in a lantern shape approximately 150 mm from the base. This was because the thin steel plate caused the deformation of the steel pipe to be localized. Damage to the concrete was concentrated in the buckling area of ​​the lower steel pipe. The prestressing steel also deformed in the normal direction along the buckling shape of the steel pipe, and fractured around the outermost edge in the loading direction.

[0055] Next, the relationship between the loading point displacement and the moment at the base in the test for Case D is shown in Figure 11. Figure 11 shows the moment-displacement relationship for Case D. As shown in Figure 11, in Case D, the load suddenly dropped from 475 kN m to 331 kN m, accompanied by two impact sounds, at loading displacements of +143 mm to +149 mm. After that, impact sounds accompanied by a drop in load continued to occur intermittently, and the test was terminated at a loading point of -180 mm.

[0056] Furthermore, although not shown in the figure, in the post-test state of Case D, unlike the other Cases A to C, no deformation of the lower steel pipe was confirmed. The concrete also had prominent horizontal cracks only at the base, and no signs of compressive failure were found. Meanwhile, a total of 30 prestressing steel members had fractured. Given these circumstances, it is inferred that both the impact noise and the load reduction were caused by fractures in the prestressing steel members.

[0057] Thus, one possible reason why the prestressing tendons fractured first in Case D is that the concrete was constrained by the lower steel pipes from the early stages of loading due to the use of cement paste as filler, which may have increased the strength required to reach compressive failure. In addition, the load loss when the prestressing tendons first fractured was greater than in Cases A to C, suggesting a brittle fracture pattern.

[0058] The test results described above show that in cases A to C, compressive failure of the concrete in the lower steel pipe section was induced as expected. At this time, it was confirmed that a smaller gap between the lower steel pipe and the concrete tends to suppress the decrease in strength during compressive failure. On the other hand, in case D, the PC tendon fractured first. From this, it is believed that in order to induce compressive failure in the target utility pole using the proposed method, it is effective not only to make the lower steel pipe thinner, but also to provide a gap between the utility pole and the concrete.

[0059] Next, we will discuss the deformation mode and deformation capacity. Figure 12 shows the relationship between the load displacement and the vertical displacement at the bottom end of the lower steel pipe in each case. Figure 12 is a diagram showing the relationship between the load displacement and the vertical displacement at the base in each case. As shown in Figure 12, it can be seen that significant vertical displacement occurred in all cases A to D. Since the prestressing tendons ultimately fractured near the base, this vertical displacement is thought to be due to the elongation of the prestressing tendons. Therefore, in order to understand the deformation mode focusing on the elongation of the prestressing tendons, the load displacement δ load is decomposed using the following formula (1).

[0060]

number

[0061] δ in Equation (1) extend represents the rotational displacement component of the base due to the extension of the PC steel. non-extend indicates a displacement component that occurs due to a reason other than the extension. A schematic diagram of the method for decomposing the displacement is shown in FIG. 13. FIG. 13 shows the method for decomposing the displacement component. As shown in FIG. 13, the rotational displacement component due to the extension is expressed as a function of the rotation angle θ extend and the specimen height H (= 2000 mm), and the vertical displacement d v1 , d v2 The measured values ​​are used to calculate the following equation (2).

[0062]

number

[0063] In equation (2), B represents the distance between the two vertical displacement gauges. As shown in Figure 13, the displacement gauges were installed 20 mm outside the steel pipe.

[0064] Displacement component δ due to factors other than extension non-extend is δ load From δ extend The value was calculated by subtracting δ non-extend includes the rotational displacement component due to the plastic hinge formed by the compressive failure and the bending deformation component above the plastic hinge. extend and δ non-extend The calculated values ​​of are shown in Figure 14. Figure 14 shows the relationship between the load displacement and δ extend and δ non-extend FIG.

[0065] As shown in Fig. 14, in cases A to C, δ extend accounts for about 70 to 80% of the loading displacement. non-extend is mainly a bending deformation component. On the other hand, after compressive failure, δ non-extend This is because a plastic hinge was formed in the lower steel pipe due to compressive failure, and a rotational component was added. non-extend The absolute value of δ does not change much from the initial stage of loading. extend Only the number of cases is increasing.

[0066] From the above, it was found that even when compressive failure occurs, rotational behavior due to elongation of the PC steel is the main deformation mode before compressive failure. Furthermore, after compressive failure, a plastic hinge is formed in the lower steel pipe, and the deformation mode changes to one in which rotational behavior occurs at two points: the base and the plastic hinge. On the other hand, when compressive failure does not occur, elongation of the PC steel is always predominant. It is thought that changes in deformation mode must be appropriately taken into account when evaluating seismic performance.

[0067] The deformation performance is evaluated by the toughness factor μ shown in the following formula (3).

[0068]

number

[0069] δ in Equation (3) y is the yield displacement, the displacement at which the design fracture strength of 300 kN m is first reached, δ u is the ultimate displacement, which is the smaller of the displacements at which the design fracture strength is exceeded or the prestressing tendon first breaks. The envelope curves of the relationship between the loaded displacement and moment for each case are shown in Figure 15, and the toughness factor is shown in Figure 16. Figure 15 shows the envelope curves of the moment-displacement relationship. Figure 16 shows the calculation results of the toughness factor.

[0070] As shown in Figures 15 and 16, the toughness ratio was improved in both cases compared to the unreinforced case (2.98). In Case A, where the gap between the concrete and the steel pipe was large, the toughness ratio was the lowest at 4.72 because the design fracture strength was lower during compressive failure. The toughness ratios of Cases B and C were more than twice that of Case A, and reducing the gap improved deformation performance. Furthermore, Case C, where the lower steel pipe was thinner, had a toughness ratio 16% higher than Case B. This may be because the restraining force of the steel pipe was smaller after compressive failure, dispersing the strain in the prestressing tendons and making them less likely to fracture. On the other hand, when the prestressing tendons fracture first, as in Case D, the toughness ratio is thought to be limited to around 8.

[0071] As described above, the reinforcement structure and method are easy to install and reinforce the existing prestressing tendons by filling the interior with mortar and wrapping the outer periphery with steel plates without cutting them. Experiments have confirmed that the reinforcement structure and method significantly suppresses the decline in strength during compressive failure of concrete compared to unreinforced concrete, improving deformation performance by approximately 3 to 4 times. Furthermore, it has been revealed that the reinforcement structure and method are more effective in improving deformation performance when the gap between the steel pipe and the utility pole is reduced. Furthermore, with the reinforcement structure and method, rotational behavior due to elongation of the prestressing tendons is dominant before compressive failure, while rotational behavior due to the formation of plastic hinges becomes significant after compressive failure, demonstrating a change in behavior before and after compressive failure.

[0072] Although some of the embodiments of the present application have been described above based on the drawings, these are merely examples, and the present invention may be embodied in other forms that include various modifications and improvements based on the knowledge of those skilled in the art, including the aspects described in the Disclosure of the Invention section. [Explanation of symbols]

[0073] 10 Electric pole (pillar body) 11 PC steel 12 Inside 13 Lower 20 Internal filling member 21 Bag parts 22 First filling material 30 First reinforcing member 40 Second reinforcing member 50 Second Filler 60 Third Filler 100 Column reinforcement structure BS basics SR surface

Claims

1. A reinforcement structure for a substantially cylindrical column in which PC steel is embedded, a first filler material filled inside the pillar body, the lower part of which is buried and erected; a first reinforcing member disposed along the outer periphery of the lower side of the pillar body with a gap provided between the first reinforcing member and the pillar body; a second reinforcing member arranged next to the first reinforcing member above the position of the first reinforcing member on the pillar body, and reinforcing the pillar body relatively more strongly than the reinforcement provided by the first reinforcing member; A column reinforcement structure comprising:

2. a second filler material filled in the gap between the first reinforcing member and the column; The reinforcement structure for a pillar body according to claim 1 , comprising:

3. A gap is provided between the first reinforcing member and the second reinforcing member along the axial direction of the column body. The reinforcement structure for a pillar body according to claim 1.

4. a third filler that fills a gap provided between the second reinforcing member and the column; The reinforcement structure for a pillar body according to claim 1 , comprising:

5. A method for reinforcing a substantially cylindrical column in which PC steel is embedded, comprising the steps of: a first filling step of filling a first filler material into the interior of the columnar body, the columnar body being erected with its lower portion buried; a first disposition step of disposing a first reinforcing member along the outer periphery of a lower side of the pillar body with a gap provided between the first reinforcing member and the pillar body; a second placement step of placing a second reinforcing member that reinforces the pillar body relatively more strongly than the reinforcement by the first reinforcing member, next to the first reinforcing member, above the placement position of the first reinforcing member on the pillar body; A method for reinforcing a column body comprising:

6. The first filling step involves drilling a hole in a part of the pole body, which is an existing electricity pole, and filling the inside of the pole body through the drilled part with a first filling material. The method for reinforcing a pillar body according to claim 5.

7. The second arranging step arranges the second reinforcing member with a gap provided between the second reinforcing member and the first reinforcing member along the axial direction of the column body. The method for reinforcing a pillar body according to claim 5.

8. a second filling step of filling the gap between the first reinforcing member and the column with a second filler; a third filling step of filling a gap provided between the second reinforcing member and the column with a third filler; The method for reinforcing a pillar body according to claim 5, comprising:

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