Method for optical fiber sensing monitoring of steel reinforcement corrosion

Abstract

The invention belongs to the technical field of steel reinforcement corrosion monitoring, and relates to a method for optical fiber sensing monitoring of steel reinforcement corrosion. The method comprises the following steps: making an optical fiber sensing monitoring device, and monitoring the steel reinforcement corrosion condition. A strain measuring grating and a temperature compensation grating are laid in the same step manner, the optical fiber sensor monitoring device and a monitored steel reinforcement are simultaneously poured in a concrete structure to avoid external interference and damages to a corresponding variable fin, the step-shaped optical fiber sensor monitoring device can monitor the corrosion condition of the steel reinforcement with different depths in the concrete structure, the corrosion time and the corrosion degree of the steel reinforcement with different depths are analyzed to know the corrosion time and the corrosion degree of a steel reinforcement to be monitored in the reinforced concrete structure, and bolts with different lengths are selected to control the inclination of the optical fiber sensing monitoring device to realize the real-time and long-term online monitoring of the steel reinforcement corrosion in the concrete structure with different protection layer thicknesses. The method has the advantages of enlargement of the application range, scientific and reliable principle, and accurate and reliable monitoring result.

Description

[0001] Technical field: [0002] The invention belongs to the technical field of steel bar corrosion monitoring, and in particular relates to a method for monitoring steel bar corrosion by optical fiber sensing, which uses an optical fiber sensing monitoring device for real-time monitoring to assess the corrosion status of steel bars in concrete structures. [0003] Background technique: [0004] In reinforced concrete structures, the corrosion of steel bars is one of the important factors affecting the safety and durability of construction engineering structures; when steel bars are corroded, the volume expands, the bond between steel bars and concrete decreases, and the concrete protective layer peels off. In turn, the strength of the building structure is reduced, and the steel bar corrosion occurs inside the building structure, which is difficult to detect with the naked eye. When repairing a slightly damaged building caused by steel bar corrosion, there are problems of heav...

AI Technical Summary

Problems solved by technology

[0004] In reinforced concrete structures, the corrosion of steel bars is one of the important factors affecting the safety and durability of construction engineering structures; when steel bars are corroded, the volume expands, the bond between steel bars and concrete decreases, and the concrete protective layer peels off. In turn, the strength of the building structure is reduced, and the steel bar corrosion occurs inside the building structure, which is difficult to detect with the naked eye. When repairing a slightly damaged building caused by steel bar corrosion, there are problems of heavy workload, high cost and poor benefit. The problem is that when the damage of the building is serious, it will bring immeasurable losses to people's lives and property safety; therefore, it is necessary to monitor the corrosion state of the steel bars in the concrete and grasp the internal conditions of the building structure, so that Early warning before the damage occurs to minimize the loss

At present, the monitoring methods for steel corrosion are divided into physical methods and chemical methods. The commonly used physical methods include the resistance probe method and the optical fiber sensing method. The former uses a probe made of the same material as the structural steel bar and embeds the probe in the concrete structure. Among them, the rate and degree of corrosion of the steel bar are inferred based on the change of the resistance of the real-time monitoring probe. The latter is based on the monitoring principle that after the steel bar is rusted, the expansion stress is generated on the surface of the steel bar, and the optical fiber is affected by the stress to produce strain. The phase, frequency, wavelength and polarization of the optical fiber are changed. The optical fiber sensor has strong corrosion resistance and anti-interference ability, good durability, and can monitor the continuity of space. The disadvantage is that the optical fiber sensing technology requires high technology and high cost; chemical There are half-cell potential method, AC impedance method and linear polarization method. The principle of the half-cell potential method is that when the steel bar is corroded, there is a potential difference between the anode area and the cathode area, and the steel bar corrosion is evaluated by the measured current and voltage values. To a certain extent, the AC impedance method is to send a small current to the target building structure, measure the response of the target building structure to the small current, and then analyze the measured alternating current spectrum. The measuring instruments used in this dynamic measurement method are very Expensive and influenced by the outside world, the later data processing procedures are cumbersome, and cannot be popularized and used; Chinese patent 201310204720.5 discloses a fiber grating detection device for steel bar corrosion in reinforced concrete members, including several steel bar bars of the same material as the steel bar used in the project, The same number of fiber gratings, bases, temperature sensors, terminal test boxes and detectors as the steel bars, the fiber gratings are fixed on the steel bars, the steel bars are fixed on the base, the fiber gratings are connected to the terminal test boxes through cables, and the terminal test The box is connected to the detector, and the temperature sensor is fixed on the base. There is no temperature compensation grating, and the influence of temperature on the wavelength drift is not considered. The fiber grating is pasted on the arc-shaped steel bar that is in direct contact with the concrete, and the service life is greatly shortened; Chinese patent 201220615624.0 discloses a steel bar corrosion monitoring device in a concrete structure, which includes an optical fiber grating strain sensor, a signal processing unit, a stainless steel inclined plane support, at least three optical fiber grating strain sensors and wires, and the optical fiber grating strain sensors are sequentially arranged on the slope of the inclined plane support The signals collected by each fiber grating strain sensor are transmitted to the signal processing unit through wires, and the fiber grating strain sensor measures the tensile strain in the concrete protective layer caused by the rust expansion force generated by the corrosion products of steel bars, and deduces the corrosion rate of steel bars and the initial corrosion of steel bars Time, in order to realize the indirect monitoring steel bar corrosion condition, its device is easily damaged in the process of pouring concrete; Chinese patent 201120123546.8 discloses an embedded steel bar corrosion monitoring system for monitoring steel bar corrosion in reinforced concrete structures, including a single anode , a sensor composed of a single cathode and a PVC pipe, a bracket and a wire, a single anode and a single cathode are alternately connected, the PVC pipe is set between the single anode and the single cathode, the single anode and the single cathode are connected to the wire, and the bracket is connected to the sensor and the wire A half-cell potential-based The device is divided into four layers, and each layer contains 4 cathodes and 4 anodes. A total of 32 wires need to be drawn out. The structure is complex, there are too many wires, and more data needs to be measured.

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