A device for monitoring the radial strain distribution of steel reinforcement corrosion expansion

Abstract

This invention provides a device for monitoring the radial strain distribution of steel reinforcement corrosion expansion, belonging to the field of structural health monitoring technology. The device comprises a semi-annular stainless steel shell, a semi-annular stainless steel shell cover, a semi-annular stainless steel shell base, a fan-shaped hollow convex extrusion block, a single-mode optical fiber, a Fabry-Perot cavity, a protective soft sleeve, butterfly-shaped hand-tightened rubber-tipped screws, and rivets. This device is based on the principle of a multiplexed intrinsic Fabry-Perot interferometer and the change in the length of the Fabry-Perot cavity caused by steel reinforcement corrosion expansion. When the steel reinforcement corrodes and expands, the tensile strain of the Fabry-Perot cavity increases, and the increase is proportional to the magnitude of the radial strain caused by the steel reinforcement corrosion expansion. By monitoring the increase in the tensile strain of the Fabry-Perot cavity, real-time, quantitative, and non-destructive monitoring of the radial strain distribution of steel reinforcement corrosion expansion is achieved. This invention is simple to manufacture, has low economic cost, greatly reduces manual labor, and is easy to install, facilitating large-scale deployment.

Description

Technical Field

[0001] This invention relates to a device based on a multiplexed intrinsic Fabry-Perot interferometer for monitoring the radial strain distribution of steel reinforcement corrosion expansion, belonging to the field of structural health monitoring technology, and is used for monitoring the radial strain distribution of steel reinforcement corrosion expansion in concrete structures. Background Technology

[0002] Reinforced concrete structures offer numerous advantages, including simple construction procedures, high construction efficiency and short construction periods, and high cost-effectiveness over long-term use. They are a highly economical structural form, widely used in industrial and civil buildings, and are one of the most widely used structural types in the global construction industry. However, with the passage of time and the increasing complexity of the service environment for engineering structures, the durability issues of reinforced concrete structures have become increasingly prominent. Steel corrosion leads to premature failure of concrete structures. Furthermore, in projects such as bridges or ports near the coast, corrosion causes reinforced concrete structures to fail even earlier after construction, failing to reach their designed service life and reducing their intended economic benefits. Therefore, monitoring the radial strain distribution of steel corrosion expansion within the structure is essential to ensure its safe and normal operation.

[0003] Currently, common detection methods for steel reinforcement corrosion and expansion are divided into two main categories: destructive testing and non-destructive testing. Destructive testing involves chiseling open the structure and visually inspecting the exposed steel reinforcement. This method is generally used when the corrosion is severe, indicating a later stage of structural damage, and cannot achieve real-time monitoring. Non-destructive testing includes methods such as resistance rod testing, eddy current testing, acoustic emission testing, and corrosion potential testing. However, these methods are currently limited in practical engineering applications due to their high cost, inability to provide long-term real-time monitoring, and constraints related to installation conditions and site environment. Furthermore, steel reinforcement corrosion in concrete structures is often characterized by uneven, localized corrosion along the length and circumference, which these methods cannot detect.

[0004] In recent years, optical fibers have received significant attention in structural health monitoring due to their advantages such as small size and light weight, corrosion resistance, electromagnetic interference resistance, real-time monitoring capabilities, networking, and data reliability. Among these, Fabry-Perot interferometric fiber optic sensors achieve beam interference by constructing Fabry-Perot cavities on the fiber. When the measured physical quantity changes, the phase difference between the two coherent beams also changes, causing a shift in the interference spectrum. Compared to distributed fiber optics, traditional Fabry-Perot interferometric fiber optic sensors offer higher resolution, reaching the nanometer level, but their drawback is that they can only measure at a single location. Multiplexed intrinsic Fabry-Perot interferometric fiber optic sensors, however, possess multiple Fabry-Perot cavities, enabling monitoring at multiple locations and overcoming the limitations of traditional sensors. These sensors offer high resolution and sensitivity, making them suitable for health monitoring of reinforced concrete structural components, and they hold great potential for development in the field of steel corrosion and expansion monitoring.

[0005] Therefore, it is particularly important to provide a highly sensitive, real-time, and non-destructive monitoring device from a new technological perspective for monitoring the circumferential strain distribution of steel corrosion expansion in reinforced concrete structures, thereby providing an important guarantee for the safe service of reinforced concrete structures. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a device for monitoring the radial strain distribution of steel reinforcement corrosion expansion. The purpose is to achieve real-time monitoring of the radial strain distribution of steel reinforcement corrosion expansion, accurately determine the health status of the structure, and thus ensure the safety of the structure.

[0007] The technical solution of this invention:

[0008] A device for monitoring the radial strain distribution of steel bar corrosion expansion includes a semi-annular stainless steel shell 1, a semi-annular stainless steel shell cover 2, a semi-annular stainless steel shell bottom 3, a fan-shaped hollow outwardly protruding extrusion block 4, a single-mode optical fiber 5, a Fabry-Perot cavity 6, a protective soft sleeve 7, a butterfly-shaped hand-tightened rubber head screw 8, and a rivet 9.

[0009] The semi-annular stainless steel outer shell 1 is composed of a semi-annular stainless steel outer shell cover 2 and a semi-annular stainless steel outer shell bottom 3, as shown below. Figure 1 As shown, epoxy resin adhesive is used for bonding during splicing;

[0010] The inner semicircular side of the semi-annular stainless steel shell 1 is open, and there is a raised part at the edge.

[0011] The aforementioned fan-shaped hollow convex extrusion block 4 is made of PA12 nylon material and is manufactured using multi-jet melting 3D printing technology;

[0012] The semi-annular stainless steel shell 1 contains several fan-shaped hollow outwardly protruding extrusion blocks 4 arranged along the circumference.

[0013] The fan-shaped hollow convex extrusion block 4 is placed in the semi-circular stainless steel shell 1, and the outer concave arc surface is blocked by the protrusion of the inner semi-circular side edge of the semi-circular stainless steel shell 1, so it will not slip out.

[0014] The convex arc apex of the outer side of the fan-shaped hollow convex extrusion block 4 is in contact with the inner wall of the semi-annular stainless steel shell 1 and is bonded with cyanoacrylate adhesive. The other contact parts are ordinary contacts without any bonding or fixing.

[0015] The height of the fan-shaped hollow convex extrusion block 4 is the same as the height of the internal space of the semi-annular stainless steel shell 1;

[0016] Several Fabry-Perot cavities 6 were generated on the single-mode fiber 5 using femtosecond laser technology;

[0017] The single-mode optical fiber 5 passes through the midpoint of the intersection line between the plane and the arc-shaped surface of the fan-shaped hollow convex extrusion block 4, as... Figure 2 As shown;

[0018] The contact portion between the fan-shaped hollow convex extrusion block 4 and the single-mode optical fiber 5 is bonded with cyanoacrylate adhesive.

[0019] The Fabry-Perot cavity 6 on the single-mode optical fiber 5 is located at the middle position of the hollow part in the middle of the fan-shaped hollow outward convex extrusion block 4.

[0020] The portion of the single-mode optical fiber 5 extending out of the semi-annular stainless steel outer shell 1 is protected by a protective soft sleeve 7.

[0021] The two semi-annular stainless steel shells 1 are joined together by rivets 9 at one end, which allow the device to rotate but are not detachable. The other end is connected by a butterfly-shaped hand-tightened rubber-tight screw 8, allowing the device to be opened.

[0022] The size of the semi-annular stainless steel shell 1 and the quantity and size of the fan-shaped hollow convex extrusion blocks 4 are adjusted according to the actual diameter of the steel bar to be tested.

[0023] Working principle of the invention:

[0024] The principle of the device for monitoring the radial strain distribution of steel corrosion expansion based on a multiplexed intrinsic Fabry-Perot interferometer is as follows: Figure 9As shown, when the reinforcing steel corrodes and expands, the expanded material exerts radial compressive force on the fan-shaped hollow convex extrusion block 4. At this time, the radial strain of the fan-shaped hollow convex extrusion block 4 decreases, while the circumferential strain increases. Since the contact portion between the fan-shaped hollow convex extrusion block 4 and the single-mode optical fiber 5 is bonded with cyanoacrylate adhesive, the single-mode optical fiber 5 elongates as the circumferential strain of the fan-shaped hollow convex extrusion block 4 increases. This also causes the cavity length of the Fabry-Perot cavity 6 to elongate from l to l', thereby increasing the tensile strain of the Fabry-Perot cavity 6. By establishing the relationship between the circumferential strain of the fan-shaped hollow convex extrusion block 4 and the increase in tensile strain of the Fabry-Perot cavity 6, real-time monitoring of the radial strain distribution of the reinforcing steel corrosion expansion can be achieved.

[0025] like Figure 9 As shown, before the steel reinforcement corrodes, the upper half of the hollow portion of the sector-shaped hollow convex extrusion block 4 can be considered as an isosceles triangle with side length a and base angle θ. At this time, the fiber length l at the hollow portion of the sector-shaped hollow convex extrusion block 4 is...

[0026] l=2acosθ (1)

[0027] When the reinforcing steel corrodes, the volume expansion causes an increase in radius x at a certain point along the circumference. At this time, the length of the isosceles triangle in the upper half of the hollow part of the sector-shaped hollow convex extrusion block 4 remains unchanged, while the height decreases. This causes the optical fiber to undergo circumferential strain and be elongated, with a length l′ of...

[0028]

[0029] The fiber elongation deformation Δ in this part l for

[0030]

[0031] The strain ε of the optical fiber is then...

[0032]

[0033] Based on the principle of Rayleigh scattering distributed fiber optic strain sensing, when the strain changes, the backscattered Rayleigh spectrum of the optical signal in the fiber will shift in frequency. The magnitude of this shift is proportional to the magnitude of the strain change.

[0034] v′=v 0 +C·ε (5)

[0035] In the formula, ν 0 ν′ and ν′ represent the spectral frequency shifts of the steel reinforcement before and after corrosion, respectively; C is the strain coefficient (dv / dε); and ε is the fiber strain.

[0036] Furthermore, the relationship between the radial strain ε′ at a certain point along the circumference of the reinforcing bar and the increase x is as follows:

[0037]

[0038] In the formula, r is the original radius of the reinforcing bar.

[0039] Substituting relation (4) into relation (5), and then substituting relation (6), we obtain the relation between the spectral frequency shift and the radial strain ε′ at a certain point along the circumference of the steel bar, i.e.

[0040]

[0041] Therefore, by measuring the spectral frequency shift through optical fiber and then using the relation (7), the radial strain ε′ at a certain point along the circumference of the steel bar after corrosion can be obtained.

[0042] Therefore, based on the above-mentioned invention principle, we can monitor whether the steel bar is corroded by measuring the spectral frequency shift through continuous optical fiber, and calculate the radial strain distribution at each point along the circumference after the steel bar corrodes and expands.

[0043] The present invention has the following advantages over the prior art:

[0044] (1) This invention monitors the radial strain distribution of steel reinforcement corrosion expansion by monitoring the changes in spectral signals in optical fibers.

[0045] (2) The present invention is highly sensitive to the compressive force generated by the corrosion expansion of steel bars, and its performance is stable.

[0046] (3) The present invention can monitor the radial strain distribution of steel reinforcement corrosion expansion in real time, online and non-destructively, thereby providing early warning and maintenance for structural safety.

[0047] (4) This invention is simple to manufacture, has low economic cost, greatly reduces the amount of manual labor, and is easy to install, making it convenient for large-scale use. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the semi-annular stainless steel casing of the device for monitoring the radial strain distribution of steel bar corrosion expansion according to the present invention;

[0049] Figure 2 This is a schematic diagram of the fan-shaped hollow convex extrusion block of the device for monitoring the radial strain distribution of steel corrosion expansion according to the present invention;

[0050] Figure 3 This is a schematic diagram of the structure of the device for monitoring the radial strain distribution of steel bar corrosion expansion according to the present invention;

[0051] Figure 4 This is a top view of the device for monitoring radial strain distribution of steel bar corrosion expansion according to the present invention;

[0052] Figure 5 This is a cross-sectional view of section AA of the device for monitoring radial strain distribution of steel bar corrosion expansion according to the present invention;

[0053] Figure 6 This is a front view of the device for monitoring radial strain distribution of steel bar corrosion expansion according to the present invention;

[0054] Figure 7 This is a cross-sectional view of the BB section of the device for monitoring the radial strain distribution of steel bar corrosion expansion according to the present invention;

[0055] Figure 8 This is a schematic diagram of the arrangement for monitoring the radial strain distribution of actual steel bar corrosion expansion according to the present invention;

[0056] Figure 9 This is a schematic diagram illustrating the monitoring principle of the present invention.

[0057] In the figure: 1. Semi-circular stainless steel shell; 2. Semi-circular stainless steel shell cover; 3. Semi-circular stainless steel shell bottom; 4. Fan-shaped hollow convex extrusion block; 5. Single-mode optical fiber; 6. Fapper cavity; 7. Protective soft sleeve; 8. Butterfly-shaped hand-tightened rubber head screw; 9. Rivet; 10. Fiber optic sensing device for monitoring the radial strain distribution of steel corrosion expansion; 11. Steel bar; 12. Concrete. Detailed Implementation

[0058] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0059] like Figures 1-9 As shown, the present invention provides a device for monitoring the radial strain distribution of steel bar corrosion expansion, comprising a semi-annular stainless steel shell 1, a semi-annular stainless steel shell cover 2, a semi-annular stainless steel shell bottom 3, a fan-shaped hollow outwardly protruding extrusion block 4, a single-mode optical fiber 5, a Fabry-Perot cavity 6, a protective soft sleeve 7, a butterfly-shaped hand-tightened rubber head screw 8, and a rivet 9.

[0060] The semi-annular stainless steel outer shell 1 is composed of a semi-annular stainless steel outer shell cover 2 and a semi-annular stainless steel outer shell bottom 3, as shown below. Figure 1 As shown, epoxy resin adhesive is used for bonding during splicing;

[0061] The inner semicircular side of the semi-annular stainless steel shell 1 is open, and there is a raised part at the edge.

[0062] The aforementioned fan-shaped hollow convex extrusion block 4 is made of PA12 nylon material and is manufactured using multi-jet melting 3D printing technology;

[0063] The semi-annular stainless steel shell 1 contains several fan-shaped hollow outwardly protruding extrusion blocks 4;

[0064] The fan-shaped hollow convex extrusion block 4 is placed in the semi-circular stainless steel shell 1, and the outer concave arc surface is blocked by the protrusion of the inner semi-circular side edge of the semi-circular stainless steel shell 1, so it will not slip out.

[0065] The convex arc apex of the outer side of the fan-shaped hollow convex extrusion block 4 is in contact with the inner wall of the semi-annular stainless steel shell 1 and is bonded with cyanoacrylate adhesive. The other contact parts are ordinary contacts without any bonding or fixing.

[0066] The height of the fan-shaped hollow convex extrusion block 4 is the same as the height of the internal space of the semi-annular stainless steel shell 1;

[0067] Several Fabry-Perot cavities 6 were generated on the single-mode fiber 5 using femtosecond laser technology;

[0068] The single-mode optical fiber 5 passes through the midpoint of the intersection line between the plane and the arc-shaped surface of the fan-shaped hollow convex extrusion block 4, as... Figure 2 As shown;

[0069] The contact portion between the fan-shaped hollow convex extrusion block 4 and the single-mode optical fiber 5 is bonded with cyanoacrylate adhesive.

[0070] The Fabry-Perot cavity 6 on the single-mode optical fiber 5 is located at the middle position of the hollow part in the middle of the fan-shaped hollow outward convex extrusion block 4.

[0071] The portion of the single-mode optical fiber 5 extending out of the semi-annular stainless steel outer shell 1 is protected by a protective soft sleeve 7.

[0072] The two semi-annular stainless steel shells 1 are joined together by rivets 9 at one end, which allow the device to rotate but are not detachable. The other end is connected by a butterfly-shaped hand-tightened rubber-tight screw 8, allowing the device to be opened.

[0073] The size of the semi-annular stainless steel shell 1 and the quantity and size of the fan-shaped hollow convex extrusion blocks 4 are adjusted according to the actual diameter of the steel bar to be tested.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for monitoring the radial strain distribution of steel reinforcement corrosion expansion, characterized in that, The device for monitoring the radial strain distribution of steel bar corrosion expansion includes a semi-annular stainless steel shell (1), a semi-annular stainless steel shell cover (2), a semi-annular stainless steel shell bottom (3), a fan-shaped hollow outward convex extrusion block (4), a single-mode optical fiber (5), a Fabry-Perot cavity (6), a protective soft sleeve (7), a butterfly-shaped hand-tightened rubber head screw (8), and a rivet (9). The semi-annular stainless steel shell (1) is formed by splicing a semi-annular stainless steel shell cover (2) and a semi-annular stainless steel shell bottom (3); The inner semicircular side of the semi-annular stainless steel shell (1) is open, and there is a raised part at the edge; The fan-shaped hollow convex extrusion block (4) is made of PA12 nylon material and is manufactured by multi-jet melting 3D printing technology; The semi-annular stainless steel shell (1) contains several fan-shaped hollow convex extrusion blocks (4) placed along the circumference; The concave arc surface on the outer side of the fan-shaped hollow convex extrusion block (4) is blocked by the protrusion of the inner semi-circular side edge of the semi-circular stainless steel shell (1), and will not slip out. The arc apex of the outer side of the fan-shaped hollow convex extrusion block (4) is in contact with the inner wall of the semi-annular stainless steel shell (1) and is bonded with cyanoacrylate adhesive. The other contact parts are ordinary contacts without any bonding or fixing. The height of the fan-shaped hollow convex extrusion block (4) is the same as the height of the internal space of the semi-annular stainless steel shell (1); Several Fabry-Perot cavities (6) were generated on the single-mode fiber (5) using femtosecond laser technology; The Fabry-Perot cavity (6) on the single-mode fiber (5) is located at the middle position of the hollow part in the middle of the fan-shaped hollow outward convex extrusion block (4); The single-mode optical fiber (5) passes through a fan-shaped hollow outwardly protruding extrusion block (4) placed along the circumference in a semi-annular stainless steel shell (1); The portion of the single-mode optical fiber (5) extending out of the semi-annular stainless steel outer shell (1) is protected by a protective soft sleeve (7); When the two semi-annular stainless steel shells (1) are assembled, one end is riveted by a rivet (9) to support the rotation of the device and is not detachable; the other end is connected by a butterfly-shaped hand-tightened rubber head screw (8) so that the device can be opened.

2. The device for monitoring the radial strain distribution of steel reinforcement corrosion expansion according to claim 1, characterized in that, When the two parts of the semi-circular stainless steel shell (1), namely the semi-circular stainless steel shell cover (2) and the semi-circular stainless steel shell bottom (3), are spliced ​​together, epoxy resin glue or anti-corrosion, waterproof glue with high strength after curing is used.

3. The device for monitoring the radial strain distribution of steel reinforcement corrosion expansion according to claim 1, characterized in that, The contact portion between the fan-shaped hollow convex extrusion block (4) and the single-mode optical fiber (5) is bonded with cyanoacrylate adhesive.

4. The device for monitoring the radial strain distribution of steel reinforcement corrosion expansion according to claim 1, characterized in that, The dimensions of the semi-annular stainless steel shell (1) and the number and dimensions of the fan-shaped hollow convex extrusion blocks (4) are adjusted according to the actual diameter of the steel bar to be tested.

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