Demolition system and demolition method for reinforced concrete structures

Abstract

To provide a demolition system for reinforced concrete structures that can further reduce the environmental impact. [Solution] A pressure generating mechanism applies pressure to the reinforcing bars 13, and a DC current is supplied to the reinforcing bars 13 exposed from the reinforced concrete structure 12 via connecting terminals 19 and 20 that are tightly attached to the reinforcing bars 13. The supply of current causes the reinforcing bars 13 to expand due to heat, thereby reducing the adhesion force between the reinforcing bars 13 and the concrete 14.

Description

Technical Field

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[0001] The present invention relates to, for example, a demolition system and method for reinforced concrete structures by electric heating.

Background Art

[0002] In recent years, in new construction projects in urban areas, there have been an increasing number of projects involving the demolition of existing reinforced concrete structures. For members with a large cross-section such as pressure-resistant slabs, crushing is not easy, and demolition using a large breaker has been carried out. When a large breaker is used for demolition, the impact on the surrounding environment, such as noise, vibration, and dust generated, becomes an issue. There are also demolition methods that combine a wire saw and continuous core boring, but these have the problem of low demolition efficiency and high cost compared to a large breaker.

[0003] From such a background, the inventors have proposed a demolition method by a method of electrically heating reinforcing bars (hereinafter, the electric heating crushing method) for the purpose of improving the demolition efficiency of reinforced concrete structures and reducing the impact on the surrounding environment (Patent Document 1). This method is a demolition assisting method that generates cracks in the concrete by flowing a direct current through the reinforcing bars, making the subsequent demolition work easier.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, the demolition method by the electric heating crushing method is effective in improving demolition efficiency and reducing the impact on the surrounding environment as described above. Therefore, it is desirable to improve the demolition method by the electric heating crushing method to further reduce the impact on the environment.

[0006] The present invention aims to provide a demolition system and method for reinforced concrete structures that can further reduce their environmental impact. [Means for solving the problem]

[0007] To solve the above problems, the present invention relates to a demolition system and method for a reinforced concrete structure, characterized in that a pressure generating mechanism applies pressure to the reinforcing bars, and a direct current is supplied to the reinforcing bars exposed from the reinforced concrete structure via a connecting terminal that adheres tightly to the reinforcing bars, thereby reducing the adhesion force between the reinforcing bars and the concrete due to the thermal expansion of the reinforcing bars caused by the supply of current. Furthermore, in order to solve the above problems, the present invention supplies a direct current to the reinforcing bars exposed from a reinforced concrete structure, and reduces the adhesion force between the reinforcing bars and the concrete by causing the reinforcing bars to expand due to the thermal expansion caused by the supply of current. A pressure generating mechanism applies pressure to the reinforcing bar, and a current supply line is connected to the reinforcing bar via a connecting terminal that makes close contact with the reinforcing bar. The demolition system for reinforced concrete structures is characterized in that at least one set of connection terminals and current supply lines is provided on at least one of the positive and negative sides of the DC current, and the DC current is supplied while detecting the current of each set. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a demolition system and method for reinforced concrete structures that can further reduce the impact on the environment. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram illustrating a demolition system and a demolition method according to one embodiment of the present invention. [Figure 2] This figure shows an example of the contact configuration between the connection terminal and the reinforcing bar. [Figure 3] This diagram shows an example of a case where multiple connection terminals are used. [Modes for carrying out the invention]

[0010] The following describes a demolition system 10 and a demolition method according to one embodiment of the present invention. Figure 1 schematically shows a demolition system 10 according to one embodiment of the present invention. In this demolition system 10, a DC current is supplied to the reinforcing bars 13 of a reinforced concrete structure (hereinafter referred to as "structure") 12 placed directly on the ground (earth) 11 from a DC power supply 17 (connected to a generator not shown) via a control device 18 or a rectifier (not shown).

[0011] Connection terminals 19 and 20 are connected to two axial locations on the reinforcing bars 13 exposed from the structure 12, respectively, in a way that allows for electrical conduction. The positive output cable (+) and negative output cable (-) of the DC power supply 17 are connected to these connection terminals 19 and 20. The positive output cable (+) and negative output cable (-) function as current supply lines (or power supply lines).

[0012] As connection terminals 19 and 20, for example, it is possible to use a type that applies pressure to the reinforcing bar 13 to create a tight seal (pressure type). As a mechanism for generating such pressure (pressure generation mechanism), although not shown in the diagram, an example is one in which the connection terminals 19 and 20 are pressed against the reinforcing bar 13 by tightening bolts. Another example is one in which the elastic restoring force of an elastic body such as a leaf spring, coil spring, or air spring (balloon) is applied to the connection terminals 19 and 20 to press them against the reinforcing bar 13. Furthermore, an example is one in which the connection terminals 19 and 20 are configured as clips having a leaf spring or coil spring.

[0013] By using connection terminals 19 and 20 that generate applied pressure, loosening of the connection terminals 19 and 20 during energization can be prevented. Furthermore, if a mechanism is adopted that uses the elastic restoring force of an air spring (balloon) to act on the connection terminals 19 and 20 as the applied pressure mechanism, the applied pressure will be determined by the air pressure and the contact area between the reinforcing bar 13 and the connection terminals 19 and 20.

[0014] Regarding the reinforcing bars 13, if they are already protruding from the concrete 14 of the structure 12, the connection terminals 19 and 20 are connected to the protruding reinforcing bars 13. If the reinforcing bars 13 are not exposed from the concrete 14, it is possible to expose them by drilling holes in the concrete 14 or by scraping away the area around the exposed reinforcing bars 13 on the end face of the concrete 14. Various general techniques can be used when drilling holes in the structure 12 or scraping away the concrete 14.

[0015] Furthermore, in the structure 12, there may be cases where the concrete 14 is raised around the reinforcing bars 13, as schematically shown in Figure 2. In such cases, a conductive plate-like body (conductive member) 28 may be interposed between the reinforcing bars 13 and the connection terminal (connection terminal 19 in Figure 2) to conduct electricity. In this case, it becomes possible to ensure electrical conductivity between the reinforcing bars 13 exposed in the recesses of the concrete 14 and the connection terminals 19 and 20.

[0016] In the example shown in Figure 2, a circular plate-like body (also called a "filler" or "spacer") 28 is in surface contact with the end face of the reinforcing bar 13, and a connecting terminal 19 is in surface contact with the plate-like body 28. The outer dimensions of the plate-like body 28 (here, diameter d1) are smaller than the outer dimensions of the end face of the reinforcing bar 13 (here, diameter d2). Furthermore, various mechanisms as described above can be used to generate the pressure that presses the connecting terminal 19 (and connecting terminal 20) against the reinforcing bar 13.

[0017] Note that FIG. 2 only schematically shows the reinforcing bar 13, the concrete 14, the connection terminal 19, and the plate-like body 28. For example, the shape of the concrete 14 often has complicated shape irregularities. Further, if a sufficient contact area between the plate-like body 28 and the reinforcing bar 13 can be ensured, the contact position of the reinforcing bar 13 with the plate-like body 28 may be a portion other than the end face (such as a portion in the middle of the longitudinal direction).

[0018] The DC power supply 17 is connected to the control device 18, and the energization by the DC power supply 17 is controlled by the control device 18. In the present embodiment, the value (rated value) of the current supplied to the reinforcing bar 13 is DC2500 A, and the value (rated value) of the voltage is 50 V. These current value and voltage value are considered in view of the maximum capacity of the power supply being used, and it is also possible to increase the current value and voltage value in accordance with the capacity of the power supply being used. Although not shown, the reinforcing bar 13 is provided with temperature measurement means, leakage current detection means, etc., and the situation of the energization heating of the reinforcing bar 13 is monitored in real time.

[0019] The value of the current supplied to the reinforcing bar 13 is set in consideration of the state of the structure 12 to be disassembled, the thickness and arrangement of the reinforcing bar 13, etc. For example, the power (rated value) is changed between, for example, DC2000 A - 20 V to DC2500 A - 50 V (the rated capacity can be expanded by combining a single power supply or a plurality of power supplies), and the current value can be adjusted according to the structure 12 to be disassembled and the situation of the reinforcing bar 13. Further, the reinforcing bar 13 thermally expands due to energization. Due to the difference in the thermal expansion coefficients of the reinforcing bar 13 and the concrete 14, cracks occur in the concrete 14, the concrete 14 is weakened by heat, and the adhesion between the reinforcing bar 13 and the concrete 14 decreases.

[0020] By monitoring using a thermometer measuring means, a leakage current detection means, etc., if an excessive temperature rise or a leakage current is detected, the output of the DC power supply 17 is adjusted or the output of the DC power supply 17 is stopped. Such control of the DC power supply 17 based on the detection result of the energization status may be performed by an operator while visually observing the instruments. Alternatively, various monitoring signals may be input to the control device 18 and the control device 18 may perform it automatically.

[0021] A first ammeter (ammeter for the concrete leakage current detection line) 22 is connected to the concrete 14 of the structure 12 via a concrete leakage current detection line 21. The first ammeter 22 can detect the current flowing through the concrete 14 (the current between the concrete surfaces) and display the current value. The display of the current value may be analog or digital. Both ends of the concrete leakage current detection line 21 are connected to the concrete 14 so as to be energizable.

[0022] Furthermore, the concrete 14 is electrically grounded (earthed) via a ground wire 23 and an earth terminal 24, and a second ammeter (ammeter for the ground wire) 25 is arranged between the concrete 14 and the earth terminal 24. The second ammeter 25 can detect the current flowing through the earth wire (the current between the concrete surface and the earth) and display the current value. The display of the current value may be analog or digital, similar to the first ammeter 22. One end of the ground wire 23 is connected to the concrete 14 so as to be energizable, and the other end is connected to the earth terminal 24.

[0023] Here, it is also possible to monitor the current values indicated by the first ammeter 22 and the second ammeter 25 and adjust the output of the DC power supply 17. Such adjustment of the output related to the DC power supply 17 may be performed by an operator while visually observing the first ammeter 22 and the second ammeter 25 (mainly the first ammeter 22). Alternatively, the detection results of the first ammeter 22 and the second ammeter 25 may be input to the control device 18 and the control device 18 may automatically adjust the output of the DC power supply 17.

[0024] Field experiments were conducted on the demolition system 10 described above. The structure 12 (especially the concrete 14) was dried, and the reinforcing bars 13 were energized. As a result, the value of the first ammeter 22 (value between concrete surfaces) was 0.001 mA. Furthermore, regarding the value of the first ammeter 22, the structure 12 (especially the concrete 14) was moistened by watering, and the reinforcing bars 13 were energized. As a result, the value of the first ammeter 22 was 0.025 mA, indicating that the measured current increased compared to when it was dry.

[0025] Here, structure 12 was a reinforced concrete beam, with dimensions of W (width) 600 x H (height) 600 x L (length) 1200 (units in mm). The type and size of the reinforcing bars 13 were D (diameter) 25 for the main bars and D10 for the stirrup bars, and current was supplied to one main bar. The current value was controlled by a rectifier (not shown) to be 2500A, and the current value was read when the current and voltage stabilized. Here, the number of reinforcing bars to be supplied with current is not limited to one, but in this field experiment, current was supplied to one reinforcing bar. Also, the required power (current value of 2500A in this case) is the value for this field experiment and will change depending on differences in conditions such as the size (length and diameter) of the reinforcing bars.

[0026] In contrast, the value of the second ammeter 25 (concrete surface-to-ground value) was 0.006 mA when the structure 12 (especially the concrete 14) was in a dry state. Furthermore, when the structure was wet due to watering, the value of the second ammeter 25 was 0.010 mA, indicating that the current measurement value for the second ammeter 25 also increased compared to the dry state. For reference, the measured grounding resistance value was 12 Ω. This value is equivalent to or lower than the generally measured value, suggesting that the current was easily flowing to the ground at the time of measurement.

[0027] Thus, while the measured values ​​of the first ammeter 22 and the second ammeter 25 increased when the structure 12 was wet compared to when it was dry, they were still below 1 mA in both cases. The reason why the measured values ​​of the first ammeter 22 and the second ammeter 25 were both low, below 1 mA, can be inferred as follows.

[0028] Since the structure 12 is placed on the ground 11 and is in contact with the ground 11, even if current leaks from the concrete 14 of the structure 12, most of the current will return to the structure 12 through the part near the surface of the ground 11. In other words, a closed loop (current-carrying circuit) of current is formed spanning the structure 12 and the ground 11, and the current circulates between the structure 12 and the ground 11. For this reason, it is thought that currents exceeding 1 mA will not leak from the part of the ground 11 outside the part where the structure 12 is placed, thus preventing the occurrence of excessive leakage current.

[0029] In addition to the field experiments described above, current measurements were also performed at actual construction sites. The structures targeted (corresponding to structure 12) were the foundation underground beams and foundation footings, and the main reinforcement bars used for energization were both D25. For the foundation underground beams, after cutting both ends of the structure (structure 12), they were lifted by a crane (not shown) and energized and heated in the demolition yard on the ground. For the foundation footings, energized and heated in their original location.

[0030] For the foundation beams, measurements were taken in a wet state after thoroughly watering the concrete. For the foundation footings, the concrete surface was damp due to the effects of groundwater and rainfall. The current value for electrical heating was set to DC2500A, the same as in the field experiment.

[0031] The current measurements (concrete surface-to-ground values) were 0.106 mA at the foundation's underground beam, 0.518 mA at the upper reinforcement of the foundation footing, and 0.017 mA at the lower reinforcement of the foundation footing. At all measurement points, the current was less than 1 mA regardless of water supply (whether wet or dry).

[0032] According to the demolition system 10 and demolition method described above, the excavated structure 12 is placed directly on the ground, and the first ammeter 22 and the second ammeter 25 are connected to the concrete 14. The reinforcing bars 13 are heated by applying current while displaying the current value during the work. Therefore, it is possible to reduce leakage current even when using a high current value (e.g., DC2500A). Furthermore, it is possible to clearly indicate to workers and supervisors (workers, etc.) that the work involves low leakage current despite the use of a high current value.

[0033] This type of electric heating causes the reinforcing bars 13 to expand, resulting in cracks in the concrete 14, which reduces the concrete's strength (weakening of the concrete 14), and also reduces the adhesion between the reinforcing bars 13 and the concrete 14. As a result, the concrete 14 can be efficiently crushed with relatively little force during crushing. Furthermore, demolition can be carried out with low noise, low vibration, short time, and low dust, minimizing the impact on the surrounding environment. In addition to crushing, it can also contribute to improving workability (labor saving, time reduction, etc.) compared to demolition methods using heavy machinery such as giant breakers. Experiments conducted by the inventors showed that the ease with which the reinforcing bars 13 separated from the concrete 14 improved the efficiency of demolition of the structure 12 by about twofold, and the time required for demolition was reduced by about half.

[0034] Here, for example, it is also possible to mount the DC power supply 17 (and generator) and control device 18 on a work vehicle and move the DC power supply 17 and control device 18 to perform the demolition work.

[0035] Furthermore, the structure 12 may be cut using a wire saw or other method and then subjected to the construction method of this embodiment. Alternatively, the structure 12 may be cut using a gas cutting method, which produces less vibration and noise and is quieter. In this case, an example of a gas cutting method is one in which fuel gas or powder (metal powder) is sprayed from a cutting torch, and the structure 12 is cut out using the flame produced by burning the fuel gas or powder (for example, Japanese Patent Application Publication No. 2020-138303).

[0036] In this type of gas cutting, fuel gas and powder (metal powder) are injected from the cutting torch as a mixed gas along with combustion oxygen. The mixed gas is ignited, and a high-temperature flame (2000-2500°C or higher) is blown onto the reinforced concrete structure. The high-temperature flame melts both the reinforcing steel 13 and the concrete 14 of the reinforced concrete structure.

[0037] The melting of the reinforcing bars 13 and concrete 14 creates a crack in the reinforced concrete structure. By inserting the cutting torch into the crack and allowing the internal melting to progress, or by moving the cutting torch in the horizontal or vertical direction, the structure 12 is cut out, for example, in the shape of a rectangular parallelepiped.

[0038] Furthermore, the inventors have proposed a cutting device and cutting method (Japanese Patent Application No. 2020-157195) that allows a worker to grip the cutting torch by hand and move it flexibly to cut reinforced concrete structures. In this method, cooling water is supplied to the cutting torch, and the cooling water circulates between the inside and outside of the cutting torch. As a result, the cutting torch does not become hot, and it is possible to grip the cutting torch.

[0039] By using the demolition system 10 and cutting method of this embodiment on structures 12 cut out by gas cutting, it is possible to continuously perform a quiet construction method and carry out the entire process from cutting to demolition of the structure 12. This makes it possible to demolish the structure 12 while further reducing the environmental impact.

[0040] Alternatively, at least one of the positive output cable (+) or negative output cable (-) may be divided into multiple cables, and each cable may be provided with a connection terminal 19 (or connection terminal 20) to supply power to the reinforcing bars. Figure 3 schematically shows an example in which both the positive output cable (+) and the negative output cable (-) are multiple. In the example in Figure 3, six cables are used for both the positive and negative sides, but the number of cables is not limited to this. By connecting multiple cables to a single connection area in this way, the connection terminals 19 and 20 can be made smaller and lighter, and the workability of connecting each connection terminal 19 and 20 can be improved.

[0041] Furthermore, although not shown in the diagram, an ammeter may be installed on each cable to monitor the balance of current flowing through each cable. In this case, for example, it is possible to prevent current from concentrating in one of the cables, which could cause the cable to overheat or melt.

[0042] For example, if there are six positive and six negative cables, the current meter readings on each cable are monitored at the start of power supply to check the balance of current supply. If there are no problems with the balance of current supply, the current supply is continued. In this way, by checking the ammeter at the start of power supply, it is possible to omit subsequent monitoring of the ammeter. However, if power supply is stopped and then restarted, it is also possible to check the balance of current supply again using the ammeter at the start of power supply restart.

[0043] Furthermore, by simultaneously energizing multiple reinforcing bars 13, it becomes possible to perform electric heating on the area containing the energized reinforcing bars 13. In this case, one or more cables (connection terminals) can be connected to each reinforcing bar 13.

[0044] Although one embodiment of the present invention has been described above, the present invention is not limited to these embodiments, and many modifications are possible within the scope of the technical idea of ​​the present invention. Furthermore, the embodiments described are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. [Explanation of Symbols]

[0045] 10 Demolition System 11 Ground 12. Reinforced concrete structures 13 Reinforcement bars 14 Concrete 17 DC power supply 18 Control device 19, 20 Connection terminals 21 Concrete Leakage Current Detection Line 22. First ammeter (ammeter for concrete leakage current detection wire) 23 Ground wire 24 Ground terminal 25 2nd ammeter (ammeter for ground wire) 28 Plate-like body

Claims

1. A system for demolishing reinforced concrete structures, characterized by applying pressure to the reinforcing bars using a pressure generation mechanism, supplying a direct current to the reinforcing bars exposed from the reinforced concrete structure via a connecting terminal that adheres tightly to the reinforcing bars, and reducing the adhesion between the reinforcing bars and the concrete due to the thermal expansion of the reinforcing bars caused by the supply of current.

2. The demolition system for a reinforced concrete structure according to claim 1, characterized in that the pressure generating mechanism presses the connecting terminal against the reinforcing bar by tightening a bolt, thereby making the connecting terminal tightly attached to the reinforcing bar.

3. The demolition system for a reinforced concrete structure according to claim 1, characterized in that the pressure generating mechanism applies the elastic restoring force of an elastic body to the connecting terminal, thereby pressing the connecting terminal against the reinforcing bar and making the connecting terminal tightly attached to the reinforcing bar.

4. A demolition system for a reinforced concrete structure according to any one of claims 1 to 3, characterized in that an electrical grounding wire is connected to the concrete and an ammeter for the grounding wire is placed on the grounding wire.

5. A method for demolishing a reinforced concrete structure, characterized by applying pressure to the reinforcing bars using a pressure generating mechanism, supplying a direct current to the reinforcing bars exposed from the reinforced concrete structure via a connecting terminal that adheres tightly to the reinforcing bars, and reducing the adhesion between the reinforcing bars and the concrete due to the thermal expansion of the reinforcing bars caused by the supply of current.

6. The method for demolishing a reinforced concrete structure according to claim 5, characterized in that the pressure generating mechanism presses the connecting terminal against the reinforcing bar by tightening a bolt, thereby making the connecting terminal tightly attached to the reinforcing bar.

7. The method for demolishing a reinforced concrete structure according to claim 5, characterized in that the pressure generating mechanism applies the elastic restoring force of an elastic body to the connecting terminal, thereby pressing the connecting terminal against the reinforcing bar and making the connecting terminal tightly attached to the reinforcing bar.

8. A method for demolishing a reinforced concrete structure according to any one of claims 5 to 7, characterized in that an electrical grounding wire is connected to the concrete and a grounding wire ammeter is placed on the grounding wire.

9. A direct current is supplied to the reinforcing bars exposed from the reinforced concrete structure, and the supply of current causes the aforementioned The thermal expansion of the reinforcing steel reduces the adhesion between the reinforcing steel and the concrete. A pressure generating mechanism applies pressure to the reinforcing bar, and a current supply line is connected to the reinforcing bar via a connecting terminal that makes close contact with the reinforcing bar. A demolition system for reinforced concrete structures, characterized in that at least one set of the connection terminal and the current supply line is provided on at least one of the positive and negative sides of the DC current, and the DC current is supplied while detecting the current of each set.

10. The demolition system for reinforced concrete structures according to claim 9, characterized in that multiple sets of the connection terminal and current supply line are provided on both the positive and negative sides of the DC current.

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