A Composite Monitoring Method for Stay Cable Corrosion Based on Stress Concentration and Ultrasonic Guided Wave

Abstract

The invention discloses a stress concentration and ultrasonic guided wave based composite stay cable rusting monitoring method. The method comprises the following steps: manufacturing corrosion sensing units, and connecting the rusting sensing units with an auxiliary frame to form a prestress self-balance system; judging initial rusting time of a steel wire or a steel strand in the stay cable according to the data monitored at continuous stress measuring points which are distributed at different heights of the steel wire slice, and carrying out corresponding programs to calculate rusting extent, rusting rate or depth of stress rusting cracks; analyzing ultrasonic guided wave signal characteristic variation to judge the initial rusting time of the steel wire or the steel strand; comparing change rate of wave signal amplitude differences at different moments, and judging the rusting rate of the steel wire slice. The method can be used for quantitatively monitoring for a long time or regularly detecting the rusting and stress corrosion situation of the steel wires at the lower anchor region of the free section of the stay cable without damage to the local microenvironment; meanwhile, the rusting sensing units are arranged in the area, so that the monitoring authenticity and reliability can be further ensured.

Description

technical field [0001] The invention belongs to the technical field of monitoring the health of civil engineering structures and the durability of bridge cable structures, and is applied to the corrosion monitoring of bridge cable structures. 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 steel wires or parallel steel strands. The methods for detection and monitoring of cable structure corrosion damage include: (1) Manual methods: mainly to check the cable system Whether it is corroded, 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 labor-intensive, the inspection range is limited, and the inspection results can only be used...

AI Technical Summary

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: It is mainly used to detect cracks and rust pits on the surface of parallel steel wires. However, since 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. In addition , the shape of the anchor head is complex, and there is a large blind area in ultrasonic testing

(3) 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 radiation device is often large and not suitable for real-time monitoring

(4) 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

(5) Ultrasonic guided wave method: At present, there are researches on the steel corrosion monitoring method based on the ultrasonic guided wave theory in China, but this method is used on steel bars of full size and length, and is not a sensor product. When used in concrete, There is guided wave signal leakage, and the guided wave signal received by the sensor is weak and complex, so it is difficult to apply to actual engineering

In addition, the steel bar is a solid cylinder, and the guided wave propagating in the steel bar has many modes in the available frequency band (up to more than ten modes), and the signal will be more complicated

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