Reinforced concrete structure demolition system and demolition method

Abstract

To provide a reinforced concrete structure demolishing system capable of further reducing environmental influences.SOLUTION: A direct current is supplied to a reinforcing bar 13 exposed from a reinforced concrete structure 12, and the reinforcing bar 13 expands with heat as a result of the supply of current, thereby reducing adhesion force of the reinforcing bar 13 and concrete 14, a grounding wire with electrical grounding to the concrete 14 is connected, and a second ammeter 25 is disposed on the grounding wire.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system and method for dismantling a reinforced concrete structure, for example, by electrical heating. [Background technology]

[0002] In recent years, many new construction projects in urban areas involve the demolition of existing reinforced concrete structures. Large-section components such as pressure slabs are difficult to crush, so large breakers are used for demolition. When using large breakers for demolition, the impact on the surrounding environment, such as the noise, vibration, and dust they generate, becomes an issue. There are also demolition methods that use wire saws and continuous core boring, but these have the drawback of being less efficient and more expensive than large breakers.

[0003] Against this background, the inventors have proposed a demolition method that uses an electrical heating method for rebars (hereinafter referred to as the "electrical heating and crushing method"), with the aim of improving the efficiency of demolition of reinforced concrete structures and reducing the impact on the surrounding environment (Patent Document 1). This method is a demolition auxiliary method that uses a direct current to pass through the rebars, causing cracks in the concrete and facilitating the subsequent demolition work. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-159080 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, the demolition method using the electric heating crushing method is effective in improving the efficiency of demolition and reducing the impact on the surrounding environment. Therefore, it is desirable to improve the demolition method using the electric heating crushing method so that it can further reduce the impact on the environment.

[0006] An object of the present invention is to provide a system and method for demolition of reinforced concrete structures that can further reduce the impact on the environment. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a method for supplying a direct current to a reinforcing bar exposed from a reinforced concrete structure, and the reinforcing bar thermally expands due to the supply of the current, thereby reducing the adhesive force between the reinforcing bar and the concrete, The system and method for demolishing reinforced concrete structures are characterized in that a ground wire that electrically grounds the concrete is connected and a ground wire ammeter is placed on the ground wire. In order to solve the above problem, the present invention provides a method for supplying a direct current to a reinforcing bar exposed from a reinforced concrete structure, and the reinforcing bar thermally expands due to the current supply, thereby reducing the adhesive force between the reinforcing bar and the concrete, Connecting a current supply line to the reinforcing bar via a connection terminal; This system for demolition of reinforced concrete structures is characterized in that multiple pairs of the connection terminal and the current supply line are provided on both the positive and negative sides of the DC current, and the DC current is supplied while detecting the current in each pair. In order to solve the above problem, the present invention provides a method for supplying a direct current to a reinforcing bar exposed from a reinforced concrete structure, and the reinforcing bar thermally expands due to the current supply, thereby reducing the adhesive force between the reinforcing bar and the concrete, A plate-shaped conductive member is interposed between the reinforcing bar exposed in the recess of the concrete and the end face of the connection terminal facing the reinforcing bar, and both sides of the conductive member contact the reinforcing bar and the end face of the connection terminal to establish electrical continuity between the reinforcing bar and the connection terminal in the recess, and the connection terminal is pressed against the reinforcing bar from the end face opposite to the end face of the connection terminal by a pressure generating mechanism, The rebar The aforementioned Connect the current supply line via the connection terminal did The present invention relates to a system for dismantling reinforced concrete structures. [Effects of the Invention]

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

[0009] [Figure 1] 1 is a diagram for explaining a dismantling system and a dismantling method according to an embodiment of the present invention; [Figure 2] 10A and 10B are diagrams showing an example of a contact state between a connection terminal and a reinforcing bar. [Figure 3] FIG. 10 is a diagram showing an example in which a plurality of connection terminals are provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] A demolition system 10 and a demolition method according to one embodiment of the present invention will be described below. Figure 1 shows a schematic diagram of the demolition system 10 according to one embodiment of the present invention. In this demolition system 10, a DC power source 17 (connected to a generator, not shown) supplies DC current to rebars 13 of a reinforced concrete structure (hereinafter referred to as "structure") 12, which is placed directly on the ground (earth) 11, via a control device 18 or a rectifier (not shown).

[0011] Connection terminals 19 and 20 are electrically connected to two locations in the axial direction of the reinforcing bars 13 exposed from the structure 12. A positive output cable (+) and a negative output cable (-) of the DC power supply 17 are connected to these connection terminals 19 and 20. The positive output cable (+) and the negative output cable (-) function as current supply lines (or power supply lines).

[0012] The connection terminals 19, 20 may be, for example, of a type (pressure type) that applies pressure to the reinforcing bar 13 to bring them into close contact. Although not shown, an example of a mechanism for generating such a pressure (pressure generating mechanism) is one that presses the connection terminals 19, 20 against the reinforcing bar 13 by tightening a bolt. 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) acts on the connection terminals 19, 20 to press the connection terminals 19, 20 against the reinforcing bar 13. Another example is one in which the connection terminals 19, 20 are configured as clips having a leaf spring or coil spring.

[0013] Using connection terminals 19, 20 that generate a pressure force can prevent loosening of connection terminals 19, 20 while current is flowing. Furthermore, if a mechanism that applies the elastic restoring force of an air spring (balloon) to connection terminals 19, 20 is used as the pressure force generation mechanism, the pressure force is determined by the air pressure and the contact area between reinforcing bar 13 and connection terminals 19, 20.

[0014] Regarding the reinforcing bars 13, if the reinforcing bars 13 are already protruding from the concrete 14 of the structure 12, the connection terminals 19, 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 the reinforcing bars 13 by drilling holes in the concrete 14 or by scraping and removing the area around the reinforcing bars 13 exposed at the end surface of the concrete 14. Various common techniques can be used to drill holes in the structure 12 or scrape the concrete 14.

[0015] Furthermore, in structure 12, as shown schematically in Fig. 2, concrete 14 may bulge around reinforcing bar 13. In such cases, electricity may be passed through a conductive plate-like body (conductive member) 28 interposed between reinforcing bar 13 and a connection terminal (connection terminal 19 in Fig. 2). In this case, it is possible to ensure electrical continuity between reinforcing bar 13 exposed in a recess in concrete 14 and connection terminals 19, 20.

[0016] 2, a circular plate-shaped body (also called a "filler" or "spacer") 28 is in surface contact with the end face of the reinforcing bar 13, and a connection terminal 19 is in surface contact with the plate-shaped body 28. The outer dimension (here, diameter d1) of the plate-shaped body 28 is smaller than the outer dimension (here, diameter d2) at the end face of the reinforcing bar 13. In addition, various mechanisms such as those described above can be used as a mechanism for generating a pressure force that presses the connection terminal 19 (and connection terminal 20) against the reinforcing bar 13.

[0017] 2 only shows the reinforcing bar 13, concrete 14, connection terminal 19, and plate-like body 28 in a schematic manner, and for example, the shape of concrete 14 often has complex irregularities. Also, as long as a sufficient contact area between plate-like body 28 and reinforcing bar 13 can be ensured, the contact position between reinforcing bar 13 and plate-like body 28 may be a portion other than the end face (such as a portion midway along the length).

[0018] The DC power supply 17 is connected to a control device 18, and the supply of electricity from the DC power supply 17 is controlled by the control device 18. In this embodiment, the value (rated) of the current supplied to the reinforcing bar 13 is DC 2500 A, and the value (rated) of the voltage is 50 V. These current and voltage values ​​take into consideration the maximum capacity of the power supply being used, and it is also possible to increase the current and voltage values ​​according to the capacity of the power supply being used. In addition, although not shown, a temperature measuring means and a leakage current detecting means for the reinforcing bar 13 are provided, and the status of the electrical heating of the reinforcing bar 13 is monitored in real time.

[0019] The value of the current supplied to the reinforcing bars 13 is set taking into consideration the condition of the structure 12 to be demolished, the thickness and arrangement of the reinforcing bars 13, and other factors. For example, the power (rated) can be changed between DC 2000A-20V and DC 2500A-50V (the rated capacity can be expanded by using a single power source or by combining multiple power sources), making it possible to adjust the value of the current depending on the condition of the structure 12 and the reinforcing bars 13 to be demolished. Furthermore, the reinforcing bars 13 thermally expand when current is applied. Due to the difference in the thermal expansion coefficients between the reinforcing bars 13 and the concrete 14, cracks occur in the concrete 14, and the concrete 14 is weakened by heat, reducing the adhesive strength between the reinforcing bars 13 and the concrete 14.

[0020] If an excessive temperature rise or leakage current is detected by monitoring using a temperature measuring means, a leakage current detecting means, or the like, the output of DC power supply 17 is adjusted or stopped. Such control of DC power supply 17 based on the detection result of the current flow state may be performed by an operator while visually checking the meters. Alternatively, various monitoring signals may be input to control device 18, and the control device 18 may perform the control automatically.

[0021] A first ammeter (ammeter for 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 is capable of detecting the current flowing through the concrete 14 (current between concrete surfaces) and displaying the current value. The current value may be displayed in either an analog or digital format. Both ends of the concrete leakage current detection line 21 are connected to the concrete 14 so that electricity can be conducted therethrough.

[0022] Furthermore, the concrete 14 is electrically grounded (earthed) via a grounding wire 23 and an earth terminal 24, and a second ammeter (grounding wire ammeter) 25 is disposed between the concrete 14 and the earth terminal 24. The second ammeter 25 is capable of detecting the current flowing through the earth wire (the current between the concrete surface and the earth) and displaying the current value. The display of the current value may be analog or digital, as with the first ammeter 22. One end of the grounding wire 23 is electrically connected to the concrete 14, and the other end is connected to the earth terminal 24.

[0023] Here, it is also possible to adjust the output of the DC power supply 17 by monitoring the current values ​​indicated by the first ammeter 22 and the second ammeter 25. Such adjustment of the output of the DC power supply 17 may be performed by an operator while visually checking 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] A field experiment was conducted on the demolition system 10 described above, in which the structure 12 (particularly the concrete 14) was kept dry and electricity was passed through the reinforcing bars 13. As a result, the value of the first ammeter 22 (concrete surface - concrete surface value) was 0.001 mA. Furthermore, with regard to the value of the first ammeter 22, the structure 12 (particularly the concrete 14) was kept wet by spraying water, and electricity was passed through the reinforcing bars 13. As a result, the value of the first ammeter 22 was 0.025 mA, and the measured current value was higher than when it was dry.

[0025] Here, the structure 12 was a beam-shaped reinforced concrete structure, with dimensions of W (width) 600 × H (height) 600 × L (length) 1200 (units in mm). The types and sizes of the rebars 13 were main rebars (D) 25 and stirrup rebars (D10), and electricity was passed through one main rebar. The current value was controlled to 2500 A using a rectifier (not shown), and the current value was read when the current and voltage stabilized. While the number of rebars to be energized is not limited to one, electricity was passed through one rebar in this field experiment. The required power (here, a current value of 2500 A) was the value used in this field experiment and may vary depending on conditions such as the size (length and diameter) of the rebar.

[0026] In contrast, the value of the second ammeter 25 (concrete surface - earth value) was 0.006 mA when the structure 12 (particularly the concrete 14) was dry. Furthermore, when the structure 12 was wetted with water, the value of the second ammeter 25 was 0.010 mA, and the measured current value of the second ammeter 25 also increased compared to when it was dry. For reference, the measured earth resistance value of the earth was 12 Ω. This value is equal to or lower than the value generally measured, and it can be said that the state at the time of measurement was such that current easily flowed to the ground.

[0027] As described above, 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, but were 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] Because 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 returns to the structure 12 via a portion near the surface of the ground 11. In other words, a closed current loop (current-carrying circuit) is formed between the structure 12 and the ground 11, and current circulates between the structure 12 and the ground 11. For this reason, current exceeding 1 mA does not leak from the portion of the ground 11 where the structure 12 is placed to an outer portion, and it is thought that excessive leakage current is prevented.

[0029] Furthermore, current measurements were conducted not only in the field experiments described above but also at actual construction sites. The target structures (corresponding to structure 12) were the foundation underground beams and the foundation footing, and the reinforcing bars to which current was applied were all D25 main reinforcement bars. For the foundation underground beams, both ends of the structure (structure 12) were cut, and then the structure was lifted with a crane (not shown), and electrical heating was carried out in a demolition yard on the ground. For the foundation footing, electrical heating was carried out in situ.

[0030] For the underground foundation beams, measurements were taken in a wet state after sufficient water was sprayed on the concrete. For the foundation footings, the concrete surface was wet due to the influence of groundwater and rainfall. The current value for the electrical heating was DC 2500A, the same as in the field experiment.

[0031] The current measurement results (value between concrete surface and earth) were 0.106 mA at the foundation underground beam, 0.518 mA at the top reinforcement of the foundation footing, and 0.017 mA at the bottom reinforcement of the foundation footing. Regardless of whether water was supplied (whether in wet or dry conditions), the current was below 1 mA at all measurement points.

[0032] According to the demolition system 10 and demolition method described above, the cut structure 12 is placed directly on the ground, the first ammeter 22 and the second ammeter 25 are connected to the concrete 14, and the reinforcing bars 13 are heated by passing electricity through them while displaying the current value during the work. This makes it possible to reduce leakage current even while using a high current value (e.g., DC 2500A). Furthermore, it is possible to clearly indicate to workers, supervisors, etc. (workers, etc.) that the work involves using a high current value but with little leakage current.

[0033] Such electrical heating causes the rebars 13 to expand, cracking the concrete 14 and reducing the concrete strength (weakening the concrete 14), as well as weakening the adhesive force between the rebars 13 and the concrete 14. This allows the concrete 14 to be crushed efficiently with a relatively small force. Furthermore, demolition can be performed with low noise, low vibration, in a short time, and with little dust, minimizing the impact on the surrounding environment. In addition to crushing, this method can also contribute to improving workability (labor savings, time reduction, etc.) for demolition methods using heavy machinery such as giant breakers. In experiments conducted by the inventors, the ease with which the rebars 13 are separated from the concrete 14 has resulted in an approximately two-fold improvement in the demolition efficiency (demolition efficiency) of the structure 12, and the time required for demolition has been reduced by approximately half.

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

[0035] The structure 12 may be cut by a method using a wire saw or the like and subjected to the method of this embodiment. The structure 12 may also be cut by a gas cutting method, which is quiet and produces little vibration or noise. An example of the gas cutting method in this case is one in which fuel gas or powder (metal powder) is sprayed from a cutting torch and the structure 12 is cut out by the flame generated by burning the fuel gas or powder (for example, JP 2020-138303 A).

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

[0037] A crack is formed in the reinforced concrete structure due to the melting of the reinforcing bars 13 and concrete 14. The structure 12 is cut into, for example, a rectangular parallelepiped shape by inserting a cutting torch into the crack and proceeding with the internal melting, or by moving the cutting torch horizontally or vertically.

[0038] The inventors have also proposed a cutting device and method that allows a worker to hold a cutting torch by hand and move it flexibly to cut reinforced concrete structures (Patent Application No. 2020-157195). 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. This prevents the cutting torch from becoming too hot, making it possible to hold the cutting torch.

[0039] By using the demolition system 10 and cutting method of this embodiment for such structures 12 cut out by gas cutting, a highly silent construction method can be continuously used, and the entire process from cutting to demolition of the structure 12 can be carried out in one go. This makes it possible to demolition the structure 12 with even less impact on the environment.

[0040] At least one of the positive output cable (+) and the negative output cable (-) may be divided into multiple cables, and a connection terminal 19 (or connection terminal 20) may be provided for each cable to pass current through the rebar. FIG. 3 schematically shows an example in which both the positive output cable (+) and the negative output cable (-) are provided in multiple cables. In the example of FIG. 3, six cables are used for both the positive and negative sides, but the number of cables is not limited to this. In this way, by connecting multiple cables to one connection area, the connection terminals 19, 20 can be made smaller and lighter, and the work involved in connecting the individual connection terminals 19, 20 can be improved.

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

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

[0043] Furthermore, by simultaneously energizing a plurality of reinforcing bars 13, it is possible to perform electrical heating in an area including the energized reinforcing bars 13. In this case, it is possible to connect one or more cables (connection terminals) to each reinforcing bar 13.

[0044] Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and many modifications are possible within the scope of the technical concept of the present invention. The described embodiment is merely an example of a specific embodiment for carrying out the present invention, and the technical scope of the present invention should not be interpreted as being limited thereby. [Explanation of symbols]

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

Claims

1. A direct current is supplied to the reinforcing bars exposed from the reinforced concrete structure, and the supply of current causes the reinforcing bars to thermally expand, thereby reducing the adhesive force between the reinforcing bars and the concrete. A system for demolition of reinforced concrete structures, characterized in that a ground wire that electrically grounds the concrete is connected and a ground wire ammeter is placed on the ground wire.

2. A reinforced concrete structure demolition system as described in claim 1, characterized in that both ends of a concrete leakage current detection line are connected to the concrete, and an ammeter for a concrete leakage current detection line is arranged on the concrete leakage current detection line.

3. 3. The system for dismantling a reinforced concrete structure according to claim 1, wherein the reinforced concrete structure is cut out by gas cutting.

4. A direct current is supplied to the reinforcing bars exposed from the reinforced concrete structure, and the supply of current causes the reinforcing bars to thermally expand, thereby reducing the adhesive force between the reinforcing bars and the concrete. A method for demolishing a reinforced concrete structure, characterized in that a ground wire that electrically grounds the concrete is connected and a ground wire ammeter is placed on the ground wire.

5. A method for demolishing a reinforced concrete structure as described in claim 4, characterized in that both ends of a concrete leakage current detection line are connected to the concrete, and an ammeter for a concrete leakage current detection line is arranged on the concrete leakage current detection line.

6. 6. The method for demolishing a reinforced concrete structure according to claim 4, wherein the reinforced concrete structure is cut out by gas cutting.

7. Direct current is supplied to the exposed rebars of the reinforced concrete structure, and the supply of current causes the Thermal expansion of the reinforcing bars reduces the adhesive strength between the reinforcing bars and concrete, Connecting a current supply line to the reinforcing bar via a connection terminal; A system for dismantling reinforced concrete structures, characterized in that multiple pairs of the connection terminal and the current supply line are provided on both the positive and negative sides of the DC current, and the DC current is supplied while detecting the current in each pair.

8. A direct current is supplied to the reinforcing bars exposed from the reinforced concrete structure, and the supply of current causes the reinforcing bars to thermally expand, thereby reducing the adhesive force between the reinforcing bars and the concrete. A system for demolishing reinforced concrete structures, characterized in that a conductive plate-shaped member is interposed between the reinforcing bar exposed in a recess in the concrete and the end face of a connection terminal facing the reinforcing bar, the conductive member having both sides in contact with the reinforcing bar and the end face of the connection terminal to establish electrical continuity between the reinforcing bar and the connection terminal within the recess, and a current supply line is connected to the reinforcing bar via the connection terminal by pressing the connection terminal against the reinforcing bar from the end face opposite the end face of the connection terminal using a pressure generating mechanism.

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