Corrosion Monitoring Method of Bridge Cables Based on Stress Concentration of Plane Stress State

Abstract

The invention discloses a bridge cable corrosion monitoring method based on stress concentration in a plane stress state. The method comprises the following steps: with a high-strength steel wire sheet with the same mark as an inner steel wire of a cable as a sensitive element, reserving one side face of the section of the steel wire sheet as a corrosion monitoring surface; setting continuous strain measuring points at different heights on the section of the steel wire sheet; applying pre-tensioning stress same as dead load cable force on the cable to the steel wire sheet, and anchoring the steel wire sheet in an auxiliary frame, wherein the steel wire sheet is in a plane stress state; arranging a corrosion monitoring device in a high-density polyethylene jacket or an anchor head protective cover of the cable; and judging initial time of corrosion or stress corrosion and calculating the corrosion degree, the corrosion rate and stress corrosion crack depth according to monitoring data when sudden change of local strain of the corrosion monitoring surface is caused. The method has the advantages of high sensitivity, stability and reliability, and the corrosion and stress corrosion states of the inner steel wire in the cable are quantitatively monitored for a long time under the condition that a local micro-environment on the surface of the steel wire is not damaged.

Description

technical field [0001] The invention belongs to the health monitoring technology of civil engineering structures, in particular to the durability monitoring and detection technology of bridge cable structures, which is applied to the corrosion monitoring of bridge cable structures and external prestressed cables. Background technique [0002] The corrosion damage of bridge cables is related to the protective measures of cables. In recent years, hot-extruded high-density polyethylene (HDPE) sheaths have been widely used for protection. The cable body is composed of parallel high-strength steel wires or parallel steel strands. The methods for detecting and monitoring cable structure corrosion damage include: (1) Manual methods: mainly to check cable Whether the system suffers from corrosion, whether the fasteners are loose, and whether the cable body is damaged. The advantage is that it can be inspected qualitatively and visually; the disadvantage is that the inspection is la...

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Problems solved by technology

The advantage is that it can be inspected qualitatively and intuitively; the disadvantage is that the inspection is labor-intensive and material resources, the inspection range is limited, and the inspection results can only be used for qualitative evaluation, which is difficult to meet the quantitative evaluation requirements, and it is impossible to realize timely detection and monitoring of sudden accidents

(2) Ultrasonic method: mainly used to detect cracks and rust pits on the surface of parallel steel wires, but because the cable is composed of multiple parallel steel wires or steel strands, the cross-sectional shape is complex, and the location of corrosion damage is uncertain, ultrasonic waves can only detect surface defects. , the shape of the anchor head is complex, and there is a large blind area in ultrasonic testing

(3) Acoustic emission method: mainly used in the monitoring of broken wires in cables, but the signal attenuation is serious

(4) Magnetic flux leakage method: It is suitable for detecting corrosion and broken wires in the free section of cables. The disadvantage is that the efficiency is low, and the detection accuracy and sensitivity are not high.

(5) Radiation method: It can detect the internal damage and defects of the cable, and can accurately obtain the damage such as corrosion and broken wires inside the cable body. The disadvantage is that in order to shield the radiation to the human body, the ray device is often large and is not suitable for real-time monitoring

(6) Electrochemical method: The electrochemical method is mainly aimed at a single steel bar or steel strand, and its detection effect is not good for cables composed of multiple parallel steel wires or steel strands, especially the current evaluation method is basically based on the potential difference. The scope judges the possibility of corrosion of the cable, but it is significantly affected by environmental factors such as temperature and humidity in the test local area

(7) Fiber Bragg grating monitoring method based on corrosion expansion: this type of method is mainly based on the corrosion expansion mechanism of steel bars, and its concrete cushion avoids interference with the corrosion interface, but the air-permeable adhesive layer and the wound optical fiber substantially affect the ion intrusion. There are differences in the real corrosion environment, and the expansion is limited by concrete extrusion, and its sensitivity and effectiveness have yet to be tested in actual engineering

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