Concrete column with both cathodic protection and constraint adjustment and operation and maintenance method thereof

Abstract

The application discloses a concrete column with cathode protection and adjustable constraint, and a method for operation and maintenance of the concrete column. The concrete column comprises a steel reinforcement cage, concrete, a carbon fiber reinforced polymer (CFRP) layer, a shape memory alloy (SMA) spiral reinforcement, a power supply and an excitation device. The steel reinforcement cage is embedded in the concrete. The CFRP layer is sleeved on the outside of the concrete. The SMA spiral reinforcement is arranged in the CFRP layer. A plurality of longitudinal reinforcements are connected to the negative electrode of the power supply. The CFRP layer is connected to the positive electrode of the power supply. The excitation device is connected to the SMA spiral reinforcement. When the thickness of the CFRP is less than a preset value, the excitation device is started to heat the SMA spiral reinforcement. The SMA spiral reinforcement provides an active constraint to the concrete column by using the restoring force, so as to offset the passive constraint lost by the anode of the CFRP layer due to deterioration, thereby maintaining the bearing capacity of the component. While inhibiting the corrosion of the steel reinforcement, the restoring force provided by the SMA makes up for the loss of the constraint force caused by the anode deterioration of the CFRP, so as to ensure the long-life and safe service of the component.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete structure, and particularly relates to a concrete column with adjustable cathode protection and constraint and a method for operation and maintenance thereof. BACKGROUND

[0002] Reinforced concrete is the most widely used and largest demand building material in civil engineering infrastructure construction due to its low cost, wide material sources, and strong durability, and the demand is increasing. However, the reinforced concrete infrastructure in coastal areas is long-term served in high temperature and humidity, high chloride ion environment, the internal steel bars of the concrete structure are prone to corrosion, the external concrete is prone to cracking, and the overall structure is also aging, thereby seriously reducing the service performance of the structure, and even causing the destruction of the structure. Therefore, the durability of the reinforced concrete structure served in the coastal environment has been a scientific and technical problem difficult to overcome. On the other hand, for the deteriorated concrete column, direct removal will bring a large economic cost, and a more reasonable method is to reinforce the deteriorated concrete column.

[0003] In recent years, CFRP (CFRP is the abbreviation of carbon fiber reinforced polymer, which is carbon fiber reinforced composite material) reinforcement is a common and effective method to improve the mechanical properties of deteriorated concrete columns. However, the traditional CFRP reinforcement can only improve the mechanical properties of the column, and has the following two shortcomings: 1) cannot prevent secondary corrosion of steel bars; 2) cannot provide active constraint. For the concrete column served in the coastal area, two problems need to be solved: first, to inhibit or prevent the corrosion of steel bars; second, to reinforce the deteriorated concrete column due to the corrosion of steel bars, and at the same time, to inhibit the secondary corrosion of steel bars.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] The main purpose of the present application is to provide a concrete column with adjustable cathode protection and constraint and a method for operation and maintenance thereof, which aims to solve the problem of mechanical property reduction of the concrete column caused by the structural deterioration of the anode protection cathode steel bar in the concrete column in the prior art.

[0006] To achieve the above object, the present application provides a concrete column with adjustable constraint and cathodic protection, comprising: a steel reinforcement cage; concrete, wherein the steel reinforcement cage is embedded in the concrete; a carbon fiber reinforced composite layer, which is sleeved outside the concrete; a shape memory alloy spiral reinforcement, which is arranged in the carbon fiber reinforced composite layer; a power supply, wherein the steel reinforcement cage is connected to the negative electrode of the power supply, and the carbon fiber reinforced composite layer is connected to the positive electrode of the power supply; an excitation device, which is connected to the shape memory alloy spiral reinforcement; the power supply is used to apply current to the carbon fiber reinforced composite layer when the steel reinforcement cage is corroded and deteriorated, so as to prevent the steel reinforcement cage from continuing to corrode; and the excitation device is used to heat the shape memory alloy spiral reinforcement when the carbon fiber reinforced composite layer is deteriorated, so that the restoring force generated by the shape memory alloy spiral reinforcement offsets the tensile force lost by the deterioration of the carbon fiber reinforced composite layer.

[0007] In a possible implementation, the carbon fiber reinforced composite layer comprises: a first composite layer, which is arranged in close contact with the outer side of the concrete, and the shape memory alloy spiral reinforcement is wound on the first composite layer; and a second composite layer, which is sleeved outside the first composite layer by the shape memory alloy spiral reinforcement.

[0008] In a possible implementation, the shape memory alloy spiral reinforcement comprises a shape memory alloy spiral fiber bundle and an insulating layer; the insulating layer is coated on the outer side of the shape memory alloy spiral fiber bundle, and the insulating layer is used to isolate the shape memory alloy spiral fiber bundle and the second composite layer, so that the shape memory alloy spiral fiber bundle is not in contact with the second composite layer.

[0009] In a possible implementation, the carbon fiber reinforced composite layer further comprises: a heat-resistant conductive adhesive, which connects the first composite layer and the second composite layer, and the heat-resistant conductive adhesive is arranged opposite to the shape memory alloy spiral reinforcement; and the thickness of the carbon fiber reinforced composite layer is the sum of the thicknesses of the first composite layer and the second composite layer.

[0010] In a possible implementation, the strain range of the shape memory alloy spiral fiber bundle is 5%-7%.

[0011] In a possible implementation, the steel reinforcement cage comprises a stirrup and a plurality of longitudinal reinforcements, and the outer sides of the plurality of longitudinal reinforcements are respectively connected to the inner side of the stirrup.

[0012] In a possible implementation, the excitation device is respectively connected to both ends of the shape memory alloy spiral reinforcement through excitation wires; the negative electrode of the power supply is connected to the steel reinforcement cage through a cathode lead-out wire, and the positive electrode of the power supply is connected to the carbon fiber reinforced composite layer through an anode lead-out wire.

[0013] In a possible implementation, the concrete column with both cathode protection and adjustable constraint further comprises: a solar panel connected with the power supply, the solar panel being used for storing and supplying power to the power supply; a corrosion monitoring device, one end of the corrosion monitoring device being connected with the cathode lead-out wire, a calomel electrode being embedded in the concrete, and the other end of the corrosion monitoring device being connected with the calomel electrode.

[0014] To achieve the above object, the application further provides a concrete column operation and maintenance method of the concrete column with both cathode protection and adjustable constraint according to any one of the above schemes, wherein the concrete column operation and maintenance method comprises: obtaining an initial current density of the concrete column with both cathode protection and adjustable constraint meeting a preset requirement; calculating a loss thickness of the carbon fiber reinforced composite material layer under the power supply applying the initial current density; calculating a load-carrying capacity of the carbon fiber reinforced composite material layer to the concrete column provided by passive constraint according to the loss thickness; calculating an excitation temperature required by the excitation device to apply to the shape memory alloy spiral rib according to the load-carrying capacity; and the excitation device heating the shape memory alloy spiral rib according to the excitation temperature, so that the active constraint load-carrying capacity of the shape memory alloy spiral rib provided by the generated restoring force offsets the member load-carrying capacity provided by the passive constraint lost by the carbon fiber reinforced composite material layer.

[0015] In a possible implementation, the obtaining of the initial current density of the concrete column with both cathode protection and adjustable constraint meeting the preset requirement specifically comprises: obtaining a cross-sectional dimension of the concrete column with both cathode protection and adjustable constraint, a thickness of the carbon fiber reinforced composite material layer, a spiral interval of the shape memory alloy spiral rib, and a service life; calculating a load-carrying capacity and ductility of the concrete column with both cathode protection and adjustable constraint according to the cross-sectional dimension, the thickness, and the spiral interval; if the load-carrying capacity and the ductility meet design values respectively, determining a design current density according to the service life; calculating a service tensile strength of the steel reinforcement cage and a service loss thickness of the carbon fiber reinforced composite material layer of the concrete column with both cathode protection and adjustable constraint when reaching the service life according to the design current density; calculating a service load-carrying capacity and a service ductility according to the service tensile strength and the service loss thickness; and if the service load-carrying capacity and the service ductility meet design values respectively, taking the design current density as the initial current density.

[0016] Beneficial effects: The application provides a concrete column with adjustable cathode protection and constraint, and a maintenance method thereof. In the concrete column, a power source applies current to a carbon fiber reinforced composite layer when a steel reinforcement framework is corroded and deteriorated, so as to prevent multiple longitudinal reinforcements from continuing to corrode. When the carbon fiber reinforced composite layer is deteriorated, an excitation device heats a shape memory alloy spiral reinforcement, so that the restoring force generated by the shape memory alloy spiral reinforcement offsets the tensile force lost due to the deterioration of the carbon fiber reinforced composite layer. Therefore, the power source applies current to the carbon fiber reinforced composite layer as an anode to protect the steel reinforcement framework as a cathode, and the excitation device heats the shape memory alloy spiral reinforcement to provide active constraint force to the carbon fiber reinforced composite layer sleeved on the inside and outside of the shape memory alloy spiral reinforcement, so as to stably protect the steel reinforcement framework, reinforce the concrete column, prevent the steel reinforcement from continuing to corrode, and further improve the mechanical properties of the concrete column. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0018] Figure 1 The structural schematic diagram of the concrete column with adjustable cathode protection and constraint provided by the embodiment of the present application is shown in the figure.

[0019] Figure 2 The schematic diagram of the connection between the first composite layer and the concrete of the concrete column with adjustable cathode protection and constraint provided by the embodiment of the present application is shown in the figure.

[0020] Figure 3 The schematic diagram of the connection between the first composite layer and the shape memory alloy spiral reinforcement of the concrete column with adjustable cathode protection and constraint provided by the embodiment of the present application is shown in the figure.

[0021] Figure 4 The schematic diagram of the connection between the C-S-C reinforcing layer and the concrete of the concrete column with adjustable cathode protection and constraint provided by the embodiment of the present application is shown in the figure.

[0022] Figure 5 The sectional view of the concrete column with adjustable cathode protection and constraint provided by the embodiment of the present application is shown in the figure.

[0023] Figure 6 The schematic diagram of the steel reinforcement potential monitoring of the concrete column with adjustable cathode protection and constraint provided by the embodiment of the present application is shown in the figure.

[0024] Figure 7The flow chart of the concrete column operation and maintenance method provided by the embodiment of the present application is shown in the figure;

[0025] Figure 8 The system full-stage operation chart of the concrete column with adjustable cathode protection and constraint provided by the embodiment of the present application is shown in the figure;

[0026] Figure 9 The specific embodiment flow chart of the concrete column operation and maintenance method provided by the embodiment of the present application is shown in the figure;

[0027] Figure 10 The relationship chart of the SMA stress strain and temperature provided by the embodiment of the present application is shown in the figure;

[0028] Figure 11 The relationship between the SMA spiral fiber bundle spacing and the bearing capacity provided by the embodiment of the present application is shown in the figure;

[0029] Figure 12 The relationship chart between the CFRP layer thickness and the bearing capacity provided by the embodiment of the present application is shown in the figure;

[0030] Figure 13 The relationship chart between the time t and the CFRP thickness under different current densities provided by the embodiment of the present application is shown in the figure;

[0031] Figure 14 The current density i and the corresponding steel corrosion condition provided by the embodiment of the present application are shown in the figure;

[0032] Figure 15 The relationship chart between the temperature T and the SMA spiral fiber bundle lifting bearing capacity provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0034] In the related art, various methods can be used to deal with the corrosion of steel bars in concrete. 1) Improve the impermeability of concrete or add rust inhibitor to concrete. This method can better delay the corrosion of steel bars, but it cannot improve the crack state of concrete, and the crack is a potential channel for the penetration of corrosion medium into concrete. 2) Use fiber reinforced polymer (FRP) bars to replace steel bars. However, the linear elastic mechanical properties of FRP bars can significantly reduce the ductility of the structure, which is not conducive to structural seismic resistance, and the destruction is sudden. In addition, the low elastic modulus of FRP bars. 3) Cathodic protection technology, which can be divided into sacrificial anode cathodic protection and impressed current cathodic protection (ICCP). ICCP has better adaptability and durability. The selection of auxiliary anode is the most critical step in the ICCP system. CFRP has been tested and is a reliable anode, but it will deteriorate to varying degrees under long-term power supply, which will reduce its mechanical properties and weaken the restraining efficiency of CFRP on concrete, thereby gradually reducing the mechanical properties of the confined concrete column.

[0035] The reinforcement methods for deteriorated reinforced concrete structures are: 1) Pouring new concrete on the deteriorated load-bearing member to increase the load-bearing section. The advantages of this reinforcement method are that the stiffness of the member is improved and it is relatively economical. The disadvantages are that the overall performance of the new and old concrete is poor, there is a stress and strain lag problem, the weight of the structure increases, and it has a great impact on adjacent members such as beams, columns, foundations, and foundations. 2) Steel plates are adhered to the outside of the reinforced member, and the internal force of the concrete is transmitted to the steel plate through structural adhesive, so that the steel plate and the original member jointly resist tension, compression, and shear to improve the load-bearing capacity and stiffness of the member, and to meet the design requirements of reinforcement. There are defects such as lagging strain, increased steel consumption, and small member ductility. 3) CFRP cloth is bonded to the surface of the member with adhesive, so that the original member jointly bears the load, which can improve the bending, shear, torsion, and compression bearing capacity of the member, increase the stiffness and ductility, and effectively control the deflection and crack width. The disadvantages are stress lagging and easy peeling failure of the adhesive-concrete interface.

[0036] The terms of the embodiments of the present application are explained:

[0037] Shape Memory Alloy (SMA) is a SMA spiral bar; Carbon Fiber Reinforced Polymer (CFRP) is a CFRP layer.

[0038] In view of the problem of the mechanical performance of the concrete column being reduced due to the structural deterioration of the structure in which the steel reinforcement is protected as a cathode by an anode in the related art mentioned above, the application provides a concrete column with adjustable cathode protection and constraint and a method for operating and maintaining the concrete column. In the concrete column, the power source applies current to the carbon fiber reinforced composite material layer when the steel reinforcement cage is corroded, so as to prevent the plurality of longitudinal reinforcement from continuing to corrode, and the excitation device heats the shape memory alloy spiral reinforcement when the carbon fiber reinforced composite material layer is deteriorated, so that the restoring force generated by the shape memory alloy spiral reinforcement offsets the tensile force lost due to the deterioration of the carbon fiber reinforced composite material layer. Therefore, the power source applies current to the carbon fiber reinforced composite material layer as an anode to protect the steel reinforcement cage as a cathode, and the excitation device heats the shape memory alloy spiral reinforcement to provide active constraint force to the carbon fiber reinforced composite material layer sleeved inside and outside the shape memory alloy spiral reinforcement, so as to stably protect the steel reinforcement cage, realize the reinforcement of the concrete column, prevent the steel reinforcement from continuing to corrode, and further improve the mechanical performance of the concrete column. Thus, the technical problem of the mechanical performance of the concrete column being reduced due to the structural deterioration of the structure in which the steel reinforcement is protected as a cathode by an anode in the related art is solved.

[0039] The application first wraps the concrete column with the CFRP layer to provide passive constraint to improve the ultimate bearing capacity of the component, and then determines the steel reinforcement corrosion state by monitoring the longitudinal reinforcement corrosion potential. When the steel reinforcement corrosion is found, the power source is turned on to use the CFRP layer as an anode to protect the steel reinforcement as a cathode to prevent further corrosion. The thickness and strain of the CFRP layer are monitored, and when the thickness and strain are found to be lower than the preset value, the excitation device is turned on to heat the SMA spiral reinforcement, and the restoring force of the SMA spiral reinforcement is used to provide an active constraint to the concrete column to offset the passive constraint lost due to the deterioration of the CFRP layer, so as to maintain the bearing capacity of the component. The device overcomes the key problem that the traditional cathode protection cannot make up for the constraint loss caused by the anode deterioration. While inhibiting the corrosion of the steel reinforcement, the restoring force provided by the SMA makes up for the loss of the constraint force caused by the anode deterioration, and ensures the long-term safe service of the component.

[0040] The technical solutions of the application and how the technical solutions of the application solve the above technical problems will be described in detail in the following specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes can not be described again in some embodiments.

[0041] As Figure 1As shown, the embodiment of the present application provides a concrete column with adjustable cathodic protection and constraint, which comprises: a steel reinforcement cage; concrete, a plurality of longitudinal reinforcement bars embedded in the concrete; a carbon fiber reinforced polymer layer (CFRP layer) sleeved outside the concrete; a shape memory alloy spiral reinforcement (SMA spiral reinforcement, a shape memory metal) arranged in the carbon fiber reinforced polymer layer; a power supply, a plurality of longitudinal reinforcement bars connected to the negative electrode of the power supply, and the carbon fiber reinforced polymer layer connected to the positive electrode of the power supply; an excitation device connected to the carbon fiber reinforced polymer layer; the power supply is used to apply current to the carbon fiber reinforced polymer layer when the plurality of longitudinal reinforcement bars are corroded and deteriorated, so as to prevent the plurality of longitudinal reinforcement bars from continuing to corrode; the excitation device is used to heat the shape memory alloy spiral reinforcement when the carbon fiber reinforced polymer layer deteriorates, so that the restoring force generated by the shape memory alloy spiral reinforcement offsets the tensile force lost by the deterioration of the carbon fiber reinforced polymer layer.

[0042] It is worth mentioning that the embodiment of the application provides a CFRP-SMA-CFRP (C-S-C) reinforcing layer outside the surface of the reinforced concrete column (i.e., the concrete surface), wherein CFRP is an abbreviation of carbon fiber reinforced polymer, which is a carbon fiber reinforced composite material; SMA is an abbreviation of shape memory alloy, which is a shape memory metal. The carbon fiber reinforced composite material layer (i.e., the CFRP layer) provides a passive constraint force to improve the ultimate bearing capacity of the concrete column, and also serves as an auxiliary anode of ICCP (impressed current cathodic protection), thereby inhibiting the corrosion of the steel bars. The potential of the column is monitored through the corrosion monitoring device, the cathodic protection system is started when the steel bars are corroded to a certain extent, and a certain amount of current is provided for the steel bars (i.e., the steel skeleton) through an external direct-current power supply, so that the steel bars (as cathodes) are subjected to cathodic polarization, the anodic reaction (Fe is oxidized into Fe2+) of the steel bars is inhibited, and thus the corrosion of the longitudinal bars is prevented. During the operation of the cathodic protection, the CFRP layer serving as the anode of the system will be deteriorated to a certain extent, and the mechanical properties thereof will be reduced, thereby causing the efficiency of the constrained concrete to decrease and the bearing capacity of the concrete column to decrease. At this time, the excitation device can be used to heat the prestressed SMA spiral bars to provide a recovery stress, so as to form an active constraint force to offset the mechanical property deterioration caused by the material loss of the CFRP layer. The SMA spiral bars are located in the middle of the two CFRP layers. The technology not only utilizes the passive constraint provided by the CFRP in the C-S-C reinforcing layer to improve the ultimate bearing capacity of the reinforced concrete column, but also utilizes the electrical conductivity of the CFRP to make the CFRP serve as the anode of the ICCP, thereby inhibiting the corrosion of the longitudinal bars. Meanwhile, the SMA spiral bars are heated by the excitation device to shrink and provide an active constraint for the column, so as to offset the decrease in the ultimate bearing capacity of the reinforced concrete column caused by the deterioration of the CFRP layer. The cathodic protection system not only improves the service life of the structure, but also significantly enhances the durability of the structure while ensuring the mechanical properties and ductility of the structure, thereby providing a scientific basis and an effective technical approach for the construction and operation of the coastal concrete infrastructure.

[0043] That is, the C-S-C reinforcing layer composed of the carbon fiber reinforced composite material layer and the shape memory alloy spiral bars can provide an active constraint for the reinforced concrete column, and the passive constraint of the CFRP layer can also provide cathodic protection for the steel bars.

[0044] It can be understood that the power supply of ICCP (impressed current cathodic protection) and the excitation device of the SMA spiral rib have long-term stable power supply capability. The application has a corrosion detection function, and the cathodic protection function is started when the reinforcement is corroded to a certain extent; the application can calculate the ultimate bearing capacity of the column improved by passive constraint according to the mechanical properties of CFRP; the application can calculate the mechanical properties and ultimate bearing capacity of the loss of CFRP after degradation according to the current density and energization time; the application can calculate the recovery stress of the SMA spiral rib and the ultimate bearing capacity of the column improved by active constraint according to the temperature.

[0045] The concrete column with adjustable cathodic protection and constraint of the embodiment of the application is used for reinforcing the coastal reinforced concrete structure and solving the corrosion problem of the reinforcement in the structure. The new structural member has advantages that the previous technology does not have in the aspects of structural reinforcement and inhibition of reinforcement corrosion.

[0046] In an embodiment of the application, the carbon fiber reinforced composite material layer comprises: a first composite layer (i.e., an inner CFRP layer) arranged in contact with the outer side of the concrete, and the shape memory alloy spiral rib is wound on the first composite layer; and a second composite layer (i.e., an outer CFRP layer) arranged outside the first composite layer by sleeving the shape memory alloy spiral rib.

[0047] Specifically, as shown in Figure 2 , Figure 3 and Figure 4 , the first composite layer and the second composite layer are arranged inside and outside each other, and the SMA spiral rib (i.e., the SMA spiral rib) is located between the two composite layers. It should be noted that the SMA spiral rib is not electrically connected with the two composite layers, so as to prevent the circuit from being short-circuited when the current is applied to the composite layer.

[0048] In an embodiment of the application, the shape memory alloy spiral rib comprises a memory spiral fiber bundle and an insulating layer; the insulating layer is coated on the outer side of the memory spiral fiber bundle, and the insulating layer is used to isolate the memory spiral fiber bundle and the second composite layer, so that the memory spiral fiber bundle is not in contact with the second composite layer.

[0049] Specifically, as shown in Figure 3 , Figure 4 and Figure 5 , the memory spiral fiber bundle (i.e., the SMA fiber bundle) is coated with an insulating layer (i.e., a gel paint) of the same thickness on the outside, and a plastic corrugated pipe is sleeved on the outside, the gel paint is filled in the corrugated pipe, the formed memory spiral prop is spirally wound on the first composite layer and fixed, and the second composite layer is tightly combined with the shape memory alloy spiral rib.

[0050] In an embodiment of the present application, the carbon fiber reinforced composite layer further comprises: a heat-resistant conductive adhesive connecting the first composite layer and the second composite layer, and the heat-resistant conductive adhesive is arranged opposite to the shape memory alloy spiral tendon; and the thickness of the carbon fiber reinforced composite layer is the sum of the thicknesses of the first composite layer and the second composite layer.

[0051] Specifically, as shown in Figure 5 the thickness of the CFRP layer is the sum of the thicknesses of the inner layer and the outer layer CFRP; the heat-resistant conductive adhesive can make the temperature of the SMA increase more, and the conductivity is to exert the cathodic protection function of the CFRP layer.

[0052] In an embodiment of the present application, the strain range of the memory spiral fiber bundle is 5%-7%.

[0053] Specifically, the strain of the memory spiral fiber bundle in the embodiment is 6%.

[0054] It should be noted that the shape memory alloy spiral fiber bundle is first subjected to cold drawing treatment to have a strain of 5%-7%, so as to have a recovery force of heating shrinkage.

[0055] In an embodiment of the present application, the concrete column with adjustable constraint and cathodic protection further comprises: a stirrup connecting a plurality of longitudinal tendons and buried in the concrete.

[0056] Specifically, as shown in Figure 6 the plurality of longitudinal tendons are connected by the stirrup to form a steel reinforcement cage, so as to improve the stability of the plurality of longitudinal tendons in the concrete.

[0057] In an embodiment of the present application, the excitation device and the two ends of the shape memory alloy spiral tendon are connected by excitation wires respectively; the plurality of longitudinal tendons are electrically connected, the negative electrode of the power supply is connected to the plurality of longitudinal tendons by a cathode lead-out wire, and the positive electrode of the power supply is connected to the carbon fiber reinforced composite layer by an anode lead-out wire.

[0058] Specifically, as shown in Figure 1 and Figure 6 the positive electrode of the power supply-carbon fiber reinforced composite layer-shape memory alloy spiral tendon-negative electrode of the power supply form a current loop for cathodic protection; the temperature excitation device is connected to the memory spiral fiber bundle by excitation wires, so as to heat the memory spiral fiber bundle to provide a recovery force.

[0059] In an embodiment of the present application, the concrete column with adjustable constraint and cathodic protection further comprises: a corrosion monitoring device, one end of the corrosion monitoring device is connected to the cathode lead-out wire, a calomel electrode is buried in the concrete, and the other end of the corrosion monitoring device is connected to the calomel electrode.

[0060] Specifically, as shown in Figure 1 and Figure 6 The rust monitoring device is a multimeter, and the multimeter is used to monitor the potential.

[0061] In an embodiment of the present application, the concrete column with both cathodic protection and adjustable constraint further comprises a solar panel connected to the power supply, and the solar panel is used to store and supply power to the power supply.

[0062] The outer CFRP cloth in the C-S-C reinforcing layer composed of the carbon fiber reinforced composite layer and the shape memory alloy spiral rib plays a dual function, that is, the CFRP cloth passively reinforces the reinforced concrete column and also serves as an anode protection rib to prevent corrosion of the cathodic protection system, wherein the passive constraint force of the CFRP can be compensated by heating the inner SMA spiral rib due to weakening of the cathodic protection, so that the existing CFRP-SMA reinforced reinforced concrete column with both structural reinforcement and cathodic protection functions can be obtained.

[0063] The present application has the following features: the SMA spiral rib of the C-S-C reinforcing layer is bonded to the CFRP cloth by heat-resistant conductive adhesive, and the excitation device heats the SMA spiral rib to generate a circular hoop force to give the column an active constraint force. The CFRP-SMA patch is attached to the outside of the reinforced concrete, the SMA spiral rib is located inside the CFRP cloth, and the SMA spiral rib is bonded to the CFRP cloth by adhesive after being insulated. The corrosion detection function is added to the component, so that the cathodic protection function is started immediately when the steel bar in the component is corroded to a certain extent. The ultimate bearing capacity of the column with passive constraint is calculated according to the mechanical properties of the CFRP, the current density and the energization time are used to calculate the mechanical properties and the ultimate bearing capacity of the CFRP after degradation, and finally the recovery stress of the SMA spiral rib is calculated by temperature, and the ultimate bearing capacity of the column with active constraint is calculated to compensate for the part of the ultimate bearing capacity lost.

[0064] That is, the embodiment of the present application solves the problems of steel bar corrosion in reinforced concrete structures in coastal environments and reinforcement of reinforced concrete columns by using a C-S-C reinforcing layer (i.e., a carbon fiber reinforced composite layer and a shape memory alloy spiral rib) to wrap the reinforced concrete column, which passively and actively constrains the component to reinforce and improve the ultimate bearing capacity of the component, and the carbon fiber reinforced composite layer (i.e., the CFRP layer) also serves as an anode material for cathodic protection to solve the problems of corrosion of the steel longitudinal rib and reinforcement of the reinforced concrete column in the structure in the coastal environment. At the same time, solar energy is introduced as a new energy source, a corrosion monitoring function is introduced, and the excitation device can also heat the shape memory alloy spiral rib (i.e., the SMA spiral rib) to compensate for the stress loss according to the stress loss of the CFRP in the cathodic protection process.

[0065] In the embodiment of the present application, the minimum thickness of the carbon fiber composite layer is determined within the service life, and the concrete column is designed according to the calculation. The potential of the longitudinal steel bars is detected to determine whether the steel bars are corroded. If the steel bars are corroded, the cathodic protection system is started, in which the carbon fiber composite layer is connected to the positive electrode and the longitudinal steel bars are connected to the negative electrode (note that the current density is determined and can be adjusted). With the operation of the cathodic protection, the corrosion of the steel bars is inhibited and will not continue to corrode, but the carbon fiber composite layer will deteriorate under long-term power supply, and its strength / capacity will decrease. Therefore, the restraining effect of the carbon fiber composite on the inner concrete decreases, resulting in a decrease in the bearing capacity of the entire column. The thickness and strain of the carbon fiber composite layer are monitored, and when it is found that the thickness and strain reach the preset value, the shape memory spiral steel bars are powered to heat and trigger the restoring force to make up for the decrease in the restraining effect of the carbon fiber composite layer, so that the column can be safely served for a long life (note that the excitation temperature is determined and can be adjusted).

[0066] Based on the above embodiment, the present application also provides a preparation method of a concrete column with both cathodic protection and adjustable restraint. After the design of the CFRP-SMA reinforced reinforced concrete column with the function of cathodic protection is completed, the component size, the arrangement of the C-S-C reinforcement layer, the specifications and amount of the longitudinal steel bars and stirrups, and the cathodic protection operation parameter setting are determined, and the preparation of the reinforced concrete column can be carried out. The structure system is intended to overcome the problem of easy corrosion of steel bars in traditional reinforced concrete structure system in coastal environment, and at the same time, the excellent mechanical properties and electrochemical properties of CFRP material are utilized to improve the strength of the structure and inhibit the corrosion of the steel bars and the development of cracks. The structure system mainly comprises a C-S-C reinforcement layer, concrete, longitudinal steel bars, standing steel bars, stirrups, heat-resistant conductive glue, insulating materials, a potentiometer, a power supply, an excitation device, and the like. The preparation method is as follows:

[0067] K1, a plurality of longitudinal steel bars and stirrups are combined into an initial steel cage. The plurality of longitudinal steel bars can be divided into tensile longitudinal steel bars, compressive steel bars, and standing steel bars. Note that the standing steel bars should be arranged at both ends and in the middle of the beam to ensure the stiffness of the initial steel cage.

[0068] K2, a lead wire is led out from the protected longitudinal steel bars (cathode), and the concrete is poured and the component is cured.

[0069] K3, after the pouring of the reinforced concrete column is completed, a C-S-C reinforcing layer is bonded to the surface, first, the SMA wire is cold-drawn to apply a prestress, to reach a strain of 6%, then a layer of plastic bellows is sleeved, the plastic bellows is filled with adhesive paint to complete the insulation treatment, second, the inner CFRP cloth of the correct size is immersed in glue and attached to the surface of the column, after the position of the inner CFRP cloth is fixed, the SMA spiral wire is spirally wound on the CFRP cloth at a certain interval and is anchored, finally, the outer CFRP cloth immersed in glue is tightly attached to the inner CFRP cloth and the SMA spiral wire. During the curing process, a template can be used to fix the position to prevent falling off during the curing process.

[0070] K4, the lead wires are led out on the outer CFRP cloth (anode) and the SMA spiral wire, and the connection of the lead wires is sealed with insulating tape.

[0071] K5, after the curing is completed, a solar panel with a power storage function and a potentiometer are connected.

[0072] K6, a high-power excitation device is connected.

[0073] The important process in the preparation of the present application is described in detail below in combination with the structural diagram.

[0074] In order to achieve the purpose of the present application, when the SMA spiral wire is subjected to the descaling treatment in step K3, the contact surface fiber bundle is polished flat to prevent the uneven surface from causing the insulation glue to be applied at different thicknesses, which in turn leads to the contact of the outer CFRP with the fiber bundle, so that a short circuit phenomenon occurs in the later power protection stage. When the insulation glue is applied, the coating film thickness should not be less than 2 mm, and the application method is to apply around the fiber bundle diameter at the contact point. This step also prevents the above-mentioned short circuit phenomenon from occurring.

[0075] The first thing to make the C-S-C reinforcing layer is to select a heat-resistant conductive glue for the bonding glue, which can make the temperature of the SMA rise more, and the conductive is to play the cathodic protection function of the CFRP layer; the thickness of the CFRP layer is the sum of the thicknesses of the inner and outer CFRP.

[0076] When the lead wires are led out in steps K2 and K4, it is appropriate to bind the lead wires at both ends of the steel bar where the stress is small. And after binding the lead wires, tin soldering is used to seal the binding place and is wrapped with insulating tape to ensure the communication and stability between the lead wires and the steel bar. For the lead wire leading-out position of the CFRP cloth, the lead wire connection is also carried out at the position where the stress is small. The connection method can be divided into two kinds: drilling holes in the cured CFRP cloth to bind the lead wires, and then sealing with tin soldering and wrapping with insulating tape; or binding the lead wires when winding the CFRP cloth, and then curing the conductive glue to make the lead wire binding place cured in the conductive glue.

[0077] Based on the above embodiments, asFigure 7 As shown, the application also provides a concrete column operation and maintenance method of the concrete column with adjustable restraint and cathodic protection, based on any one of the above schemes, comprising:

[0078] In step S101, an initial current density is obtained, which satisfies a preset requirement of the concrete column with adjustable restraint and cathodic protection.

[0079] In an implementation, in the process of determining the initial current density, the cross-sectional size of the concrete column with adjustable restraint and cathodic protection, the thickness of the carbon fiber reinforced composite material layer, the spiral interval of the shape memory alloy spiral reinforcement and the service life are obtained; the bearing capacity and the ductility of the concrete column with adjustable restraint and cathodic protection are calculated according to the cross-sectional size, the thickness and the spiral interval; if the bearing capacity and the ductility meet the design values respectively, the design current density is determined according to the service life; the service tensile strength of the longitudinal reinforcement and the service loss thickness of the carbon fiber reinforced composite material layer of the concrete column with adjustable restraint and cathodic protection when reaching the service life are calculated according to the design current density; the service bearing capacity and the service ductility are calculated according to the service tensile strength and the service loss thickness; if the service bearing capacity and the service ductility meet the design values respectively, the design current density is taken as the initial current density.

[0080] In step S102, the loss thickness of the carbon fiber reinforced composite material layer under the application of the power supply according to the initial current density is calculated.

[0081] In step S103, the passive restraint force provided by the carbon fiber reinforced composite material layer and the shape memory alloy spiral reinforcement to the concrete is calculated according to the loss thickness.

[0082] In step S104, the excitation temperature applied to the shape memory alloy spiral reinforcement by the excitation device is calculated according to the passive restraint force.

[0083] In step S105, the excitation device heats the shape memory alloy spiral reinforcement according to the excitation temperature, so that the restoring force generated by the shape memory alloy spiral reinforcement offsets the tensile force lost by the deterioration of the carbon fiber reinforced composite material layer, to form active restraint protection for multiple longitudinal reinforcements.

[0084] Next, the above-mentioned concrete column operation and maintenance method of the application will be further described through specific embodiments: Figures 8-15

[0085] ​S1, according to the sectional dimension of the concrete column, the thickness d of the CFRP layer of the C-S-C reinforcement layer and the spiral spacing s of the SMA spiral reinforcement, the tensile strength, arrangement and reinforcement ratio of the longitudinal reinforcement and the stirrup.

[0086] S2, the bearing capacity (F) and the ductility (μ) of the member are calculated.

[0087] S3, it is judged whether the bearing capacity (F) and the ductility (μ) of the member are greater than the design value (F d ) and the ductility design value (μ d ) of the bearing capacity of the member. If yes, S4 is carried out, and if no, S2 is returned. The parameters are adjusted.

[0088] S4, the member is put into use, and the time when the electric potential reaches-276mV is recorded.

[0089] S5, based on the corrosion electrochemistry principle, the corrosion state of the steel bar is evaluated by using the half-potential measurement method, and the cathodic protection effect is detected to realize the monitorability of the structure data. One end of the potentiometer is connected with the longitudinal reinforcement lead-out wire, and the other end is connected with the reference electrode close to the structure. According to the method for determining the steel bar corrosion state by measuring the steel bar corrosion potential in the concrete in the American Society for Testing and Materials standard ASTM C876-09 (see Table 1), the time t1, t2, …, tn when the potential of each partition reaches-276Mv is recorded, and the cathodic protection system is started.

[0090] Table 1: Relationship between steel bar corrosion potential and corrosion probability

[0091]

[0092] S6, the initial current density meeting the structure service life requirement is given. The current density can be adjusted appropriately according to the above steel bar corrosion evaluation method. The protection current density calculation method is shown in formula 1.

[0093]

[0094] wherein i' is the protection current density, Q is the total electric flux of the CFRP anode calculated according to the structure service life, k is the adjustment coefficient, and t is the time from the beginning of the service of the concrete member to the start of the cathodic protection.

[0095] S7, the tensile strength (f y ) of the longitudinal reinforcement and the reduced thickness (d0) of the CFRP layer when the member reaches the design service life under the condition of cathodic protection are calculated, as shown in formula 2 and formula 3.

[0096] f y = f (p, t, i0); (2)

[0097] d0 = f (t, i0); (3)

[0098] wherein, p is the longitudinal reinforcement corrosion rate, i0 represents the initial current density.

[0099] S8, calculate the bearing capacity (F t ) and ductility (μ t ) of the component when it reaches the design service life, see formula 4, formula 5.

[0100] F t = F(f y , d0); (4)

[0101] μ t = G(f y , d0); (5)

[0102] S9, determine whether the bearing capacity (F t ) and ductility (μ t ) of the component when it reaches the design service life are greater than the design value of the bearing capacity (F d ) and the design value of the ductility (μ d ). If yes, proceed to S10, if not, adjust the current density, and then return to S6.

[0103] S10, record each parameter that meets the conditions, and input i' that meets the conditions to the power supply, the power supply outputs the protection current according to the current density, and the cathodic protection system is started.

[0104] S11, use a potentiometer to monitor the size of the current density i of each subarea in real time, and monitor the longitudinal reinforcement corrosion rate (p) every month.

[0105] S12, calculate the corrosion growth rate λ, see formula 6.

[0106]

[0107] wherein, p' is the longitudinal reinforcement corrosion rate of a certain subarea in the current month, p'' is the longitudinal reinforcement corrosion rate of the same subarea in the next month, t m is a constant value.

[0108] S13, determine whether the longitudinal reinforcement corrosion growth rate is within the ideal range, i.e. λ0≥λ≥λ t . λ0 is the longitudinal reinforcement corrosion growth rate under the condition that the cathodic protection is not started, and λ tThe longitudinal reinforcement corrosion growth rate under the maximum current density i0 without affecting the structural seismic performance under the cathodic protection system. The reasons are as follows: for the structure with corrosion of steel bars and opening of cathodic protection, the selection of protection current density is extremely critical: if the protection current density is small, it cannot play the role of cathodic protection; if it is too large, over-protection will occur, which will cause acidification at the steel-concrete interface, affect the bonding of steel and concrete, and accelerate the deterioration of CFRP layer, leading to the decline of structural seismic performance. The current density i and the corresponding steel corrosion are shown in Figure 14 .

[0109] S14, output the current density i of the cathodic protection system.

[0110] S15, calculate the reduced thickness d of the CFRP layer when the CFRP layer reaches the designed service life under the current density i. The relationship between the time t and the initial CFRP thickness under different current densities is shown in Figure 13 ;

[0111] d L =g(i,t); (7)

[0112] S16, judge whether the reduced thickness d L of the CFRP layer is greater than the initial CFRP layer thickness d when it is reached, and if so, proceed to S17, otherwise return to S1 and input the increased d.

[0113] S17, calculate the reduced passive confinement force F L caused by the thickness of the CFRP layer, see formula 8. The relationship between the CFRP layer thickness and the bearing capacity is shown in Figure 12 .

[0114] F L =f(d L ); (8)

[0115] S18, and calculate the excitation temperature T of the SMA spiral reinforcement according to the reduced passive confinement force equal to the increased active confinement force F L , see formula 9.

[0116] F Z =f(T,s), F Z =F L , and T is obtained by inverse calculation as f(F Z ,s); (9)

[0117] S19, if T < T max , T max is the glass transition temperature of the heat-resistant conductive adhesive, if so, proceed to S20, otherwise return to S1 and input the new SMA spiral reinforcement spacing. The relationship between the temperature T and the SMA spiral reinforcement to improve the bearing capacity is shown in Figure 6 , and the relationship between the spiral spacing and the bearing capacity is shown inFigure 11 .

[0118] S20, every other month, record the thickness d of the reduced CFRP layer and raise to the corresponding temperature T for the bearing capacity of the supplement.

[0119] The concrete column operation and maintenance method provided by the application is applied to the concrete column with the above-mentioned cathodic protection and constraint adjustment, thereby having all the beneficial effects of the concrete column with the above-mentioned cathodic protection and constraint adjustment, which will not be described here again.

[0120] In the description of the present application, unless explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, or electrical connection or can be in communication with each other; can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0121] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0122] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is at least two, for example, two, three, etc., unless otherwise explicitly specified and limited.

[0123] It should be noted that in the present application, unless specifically defined and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be directly above or obliquely above the first feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be directly below or obliquely below the first feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0124] The terms "first", "second", "third", "fourth" and the like in the description and in the claims of the present application, if any, are used for distinguishing between similar objects and not necessarily for describing a specific sequential or chronological order. It is to be understood that the use of these terms herein is to be construed as interchangeable in order to describe the embodiments of the present application as outlined herein, for instance, the terms "first" and "second" can be interchanged with respect to the description of the embodiments of the present application. Further, the terms "comprise", "comprising", "containing", "having" and the like are to be construed as not necessarily excluding other steps, elements or features, whether or not these steps, elements or features are specifically recited in this description. It is also to be understood that the description and the drawings are not to be construed as limiting the application, but rather as illustrating the application.

[0125] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example" or "some examples" means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In the present description, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A concrete column that combines cathodic protection and adjustable constraint, characterized in that, The concrete column that combines cathodic protection and adjustable restraint includes: Reinforcing steel frame; Concrete, wherein the reinforcing steel cage is embedded in the concrete; A carbon fiber reinforced composite material layer is fitted over the outside of the concrete. Shape memory alloy spiral ribs are disposed within the carbon fiber reinforced composite material layer; A power source, wherein the steel reinforcement frame is connected to the negative terminal of the power source, and the carbon fiber reinforced composite material layer is connected to the positive terminal of the power source; The excitation device is connected to the shape memory alloy spiral bar; The power source is used to apply current to the carbon fiber reinforced composite layer when the steel reinforcement skeleton corrodes and deteriorates, so as to prevent the steel reinforcement skeleton from continuing to corrode; The excitation device is used to heat the shape memory alloy spiral tendon when the carbon fiber reinforced composite layer deteriorates, so that the restoring force generated by the shape memory alloy spiral tendon offsets the tensile force lost due to the deterioration of the carbon fiber reinforced composite layer; The carbon fiber reinforced composite material layer includes: The first composite layer is attached to the outside of the concrete, and the shape memory alloy spiral bar is wound around the first composite layer; The second composite layer is sleeved on the outside of the first composite layer by the shape memory alloy spiral ribs; The shape memory alloy spiral rib includes a shape memory alloy spiral fiber bundle and an insulating layer; The insulating layer is coated on the outside of the shape memory alloy helical fiber bundle. The insulating layer is used to isolate the shape memory alloy helical fiber bundle from the second composite layer, so that the shape memory alloy helical fiber bundle does not come into contact with the second composite layer. The carbon fiber reinforced composite material layer further includes: A heat-resistant conductive adhesive is used to connect the first composite layer and the second composite layer, and the heat-resistant conductive adhesive is disposed opposite to the shape memory alloy spiral rib. The thickness of the carbon fiber reinforced composite material layer is the sum of the thicknesses of the first composite layer and the second composite layer; The strain range of the shape memory alloy helical fiber bundle is 5%-7%; The steel reinforcement cage includes stirrups and multiple longitudinal bars, with the outer sides of the multiple longitudinal bars respectively connected to the inner sides of the stirrups; The excitation device is connected to both ends of the shape memory alloy spiral bar via excitation wires. The negative terminal of the power supply is connected to the steel reinforcement skeleton through a cathode lead-out line, and the positive terminal of the power supply is connected to the carbon fiber reinforced composite material layer through an anode lead-out line. The concrete column, which combines cathodic protection and adjustable restraint, also includes: A solar panel, connected to the power source, wherein the solar panel is used to store electricity and supply power to the power source; A corrosion monitoring device, one end of which is connected to the cathode lead wire, and a calomel electrode is embedded in the concrete, the other end of which is connected to the calomel electrode.

2. A method for the operation and maintenance of a concrete column based on the cathodic protection and adjustable constraint of a concrete column as described in claim 1, characterized in that, The operation and maintenance method for the concrete column includes: Obtain the initial current density of the concrete column that combines cathodic protection and adjustable constraint to meet the preset requirements. Calculate the thickness loss of the carbon fiber reinforced composite layer under the power supply applied at the initial current density; Based on the stated loss thickness, calculate the reduction in the load-bearing capacity provided by passive restraint to the concrete column by the carbon fiber reinforced composite layer; Based on the load-bearing capacity, calculate the excitation temperature that the excitation device needs to apply to the shape memory alloy spiral bar; The excitation device heats the shape memory alloy spiral tendon at the excitation temperature, so that the increased component load-bearing capacity of the shape memory alloy spiral tendon due to the active constraint provided by the generated restoring force offsets the component load-bearing capacity provided by the passive constraint due to the deterioration loss of the carbon fiber reinforced composite layer.

3. The method for operation and maintenance of concrete columns according to claim 2, characterized in that, Obtaining the initial current density of the adjustable concrete column with both cathodic protection and constraint to meet preset requirements specifically includes: Obtain the cross-sectional dimensions of the concrete column that combines cathodic protection and adjustable constraint, the thickness of the carbon fiber reinforced composite material layer, the helical spacing of the shape memory alloy helical reinforcement, and the service life. Based on the cross-sectional dimensions, the thickness, and the helical spacing, calculate the bearing capacity and ductility of the concrete column that combines cathodic protection and adjustable constraint. If the bearing capacity and the ductility respectively meet the design values, the design current density is determined according to the service life; Based on the design current density, calculate the service tensile strength of the steel reinforcement cage and the service loss thickness of the carbon fiber reinforced composite layer when the concrete column with both cathodic protection and adjustable constraint reaches the service life. Calculate the service bearing capacity and service ductility based on the service tensile strength and the service loss thickness; If the service bearing capacity and the service ductility respectively meet the design values, then the design current density is used as the initial current density.

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