Pre-stress damage monitoring method based on optical fiber Brillouin full-dimension sensing

Abstract

The invention provides a prestress loss monitoring method that is based on full-scale optical fiber Brillouin sensing. The prestress loss monitoring method is that a layer of high-stretchability metallic foil is winded on the outer surface of an intelligent tendon of fiber reinforced resin and Brillouin distributed optical fiber sensing so as to be a packing medium, and an outer steel wire layer of a steel stranded wire with a central wire removed is evenly twisted in the same direction of the intelligent sensing tendon, thus forming an intelligent steel stranded wire of Brillouin distributed optical fiber sensing with the property of intelligent sensing. By sensing the straining of the intelligent tendon through distributed optical fiber, the prestress loss monitoring method extrapolates a stress result of the steel stranded wire and consequently monitors the prestress loss of the whole structure, and adopts an absolute optical fiber temperature compensating method for implementing temperature compensation. The prestress loss monitoring method and the technique have the advantages of full scale, good durability, easy transmission, less wear and tear, easy setting and network building, absolute measurement and strong real-time monitoring ability, etc.

Description

(1) Technical field [0001] The invention relates to the field of long-term structural damage monitoring, in particular to a structure prestress loss monitoring technology based on Brillouin distributed optical fiber sensing. (2) Background technology [0002] Today's prestressing technology has been widely used in various fields of civil engineering. Since the reform and opening up, my country has been able to produce high-strength steel products by itself, creating conditions for the development of high-efficiency prestressed structures, which have been widely used in multi-story (high) buildings, long-span buildings, special structures, engineering reinforcement, and bridge cables or tie rods, etc. field. The loss of prestress will reduce the effect of prestress and reduce the crack resistance and stiffness of prestressed concrete components. Security risks. In addition, the existing theoretical calculation methods of prestress loss are not perfect, reliable and comprehe...

AI Technical Summary

Problems solved by technology

But these prestress monitoring sensors mainly have the following deficiencies: 1) poor long-term durability and stability

Existing sensors have poor moisture-proof, anti-corrosion, lightning-proof, and anti-interference performances, and cannot adapt to the harsh environment of long-term field work. Generally, they will fail within 2 to 3 years, and cannot achieve the purpose of long-term structural health monitoring.

2) Distributed measurement cannot be realized

The existing point-type and quasi-distributed monitoring instruments cannot fully reflect the overall stress loss mechanism of the prestressed structure, and most of them are some local point-type measurements

3) Signals cannot be transmitted over long distances

The electrical signals of resistance strain type and differential resistance sensors are generally between microvolts and millivolts. As the transmission distance increases, noise and interference increase, and the sensitivity decreases significantly. The general use distance is several meters to ten between a few meters

The steel string sensor is an AC frequency signal, and the amplitude of the output voltage waveform is distorted or attenuated, which has little influence on the measurement results, so the transmission distance can be farther, but it can only reach hundreds of meters

4) Cannot be absolutely measured

However, how to effectively combine Brillouin distributed optical fiber sensing (or supplemented by fiber Bragg gratings at local key points) with steel strands, and analyze the prestress loss according to the structural stress monitoring results, and evaluate the structure due to the prestress loss zone. The security issue that comes is a technical issue that has not yet been resolved

Although there are reports to test the prestress loss of steel strands by sampling fiber Bragg gratings, the process is to paste bare gratings directly, and its fatal disadvantage is that the twisting of steel strands during stress can easily damage the transmission line of the sensor. And the durability of the adhesive has no basic guarantee, and long-term durability monitoring cannot be realized

In addition, some people use fiber gratings and fiber-reinforced resins to form smart steel bars (fiber-reinforced plastics-fiber grating sensing composite sensing bars, authorization number: ZL 02132998.2) that are directly used in steel strands, although it is more convenient to monitor fiber gratings. The deformation information of the position point can be used to judge the stress level, but this method cannot fully grasp the rules of the time period (instantaneous loss or long-term loss) and spatial distribution of the prestress loss of the steel strand.

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