UDC 004.9 DOI 10.52167/1609-1817-2022-121-2-434-444 A.Kalizhanova

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ҚазККА Хабаршысы № 2 (121), 2022 ISSN 1609-1817 (Print) The Bulletin of KazATC Вестник КазАТК № 2 (121), 2022 ISSN 2790-5802 (Online) DOI 10.52167/1609-1817 vestnik.alt.edu.kz

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UDC 004.9 DOI 10.52167/1609-1817-2022-121-2-434-444

A.Kalizhanova ^1,2, A.Kozbakova^1,3 , M.Kunelbayev¹, Zh. Aitkulov^1,4, Zh.Amirgaliyeva¹

1Institute of Information and Computation Technologies CS MES RK, Almaty, Kazakhstan

2Almaty University of Energy and Communications, Almaty, Kazakhstan

3Almaty Technological University, Almaty, Kazakhstan

4Academy of Logistics and Transport Almaty, Kazakhstan Е-mail: [email protected]

DEVELOPMENT OF A SYSTEM OF FIBER-OPTIC SENSORS BASED ON FIBER BRAGG GRATINGS

Abstract. The article herein considers testing and distant health monitoring of bridge structure in Kazakhstan, Almaty oblast, at river Issyk. Bridge on river Issyk represents a deck type construction with total length of 70 meters and width of 6 meters. Superstructure consists of 10-inch monolithic reinforced concrete plate and leans against at prestrained piled bends, each of which consists of 5 piles. Bragg smart tilted grating fiber-optic sensor for distant health monitoring is embedded beneath the bridge. There have been conducted static and dynamic bridge testing with loaded trucks and automobiles. The sensor was switched on to data collection system, constantly installed in-situ. Collected data, as well, analytical investigations prove, that current bridges specifications are conservative. Technology, having been developed in this work’s framework, will allow fulfill practical, economically effective and reliable systemic technical maintenance of bridge structures, and research will give unique possibility for future growth of the technology in Almaty oblast and in other regions of Kazakhstan.

Keywords. Fiber-optic sensors, structures health monitoring, distributed fiber-optic sensor, time domain optical reflectometer, civil engineering.

Introduction.

Contemporary large-scale construction of engineering and building structures, such as bridges, tunnels, space shuttles, big dams and other infrastructure objects currently has considerable application. The objects thereof demand not merely huge economic investments into production process, but also closely linked with personal safety. Life cycle of those objects usually constitutes decades or even hundreds of years [1,2]. In operation process the sensors can inevitably be accompanied with various disasters (for instance, environmental pressure, fatigue effects, etc.). Structure might show itself in different degree and various damages types [3], which can bring to serious personal accidents and material losses. Therefore, the issue, whether those structures can operate safely within long time, attracted big attention. In real time regime it is necessary to conduct health monitoring and assessment, in order to avoid potential dangers and upgrade the civil objects safety indices.

Real time regime monitoring of big engineering and building structures allows timely detect structures’ total damages and assess their performance characteristics and resources, as well install, corresponding to safety, mechanism of potential calamities early prevention, which allows cut the cost on operation and technical maintenance of structures [4].

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Engineering and building structures health can be monitored with the help of sensors. For monitoring, there used embedded or surface-related sensors as systems for detecting and predicting the inner defects and damages in the construction. At there is sudden breakdown or hazardous environment, the sensor can restore the entire structural system to the best working condition by regulation and control. Engineering and building structures have characteristics of big volume, big span, wide distribution zone and long-life performance [5]. Engineering and building structures usually demand dozens or even hundreds of sensors, which execute full-scale control of deformations, displacements, temperature, vibration, etc. [6].

SHM system might face the problems of receiving, transmitting and storing big data volumes. Recently the sensors make important influence at various types of fields [7]. The most frequently used sensors in engineering and building structures system are piezoelectric element [8], strain element [9] and focus-and-scanning system [10].

Piezoelectric element might be used both as a sensor and executive mechanism with high sensitivity, good dynamic characteristics and wide application spectrum, but it has some shortages, such as fragility, difficulty in embedding into construction, low frequency features, etc. Recently factor of safety (FOS) achieved fast development and application all over the world with developing the technology of processing the signals about damages of materials and structures and enhancement of the probing technology. FOS has small size light weight, anticorrosion protection, protection from electromagnetic interference and easy assembling [11].

Materials and methods.

Bragg fiber-optic sensor with grating.

For engineering and building structures FBG sensors application is the most active area.

FBG sensors has low production cost, high quality system of demodulation and efficient technology, which are important factors for wide application. To achieve structure control in real time and monitoring structural defects occurring, FBG sensors can be fastened to structure surface or embedded into the construction. In gratings domain area FBG sensor has become a widely used one.

Technology of applying fiber-optic sensor. Bridges. Currently it is difficult to forecast and monitor exactly bridge structures and disasters consequences, such as out of date operation, corrosion, fatigue, impact, earthquake and flood. To maintain safety and big bridges longevity, it is indispensable to understand their structural health in real time mode. In works [12] there has been developed multiplexed quasidistributed FBG-sensor for monitoring the most important parts of big structures (such as pipelines, bridges and dams), achieving multiparameter measurement. In the given FBG sensor there used signals transmittance fibers to connect several fibers or sensors together, as well, there is used multiplexing principle to separate different sensors optical signals, in order to analyze different sensors monitoring data. In 2017 Xiao et al.

[13] used FBG tilted meter to monitor the bridge dynamic characteristics. Tilted meter is able not merely register rotation or deviation, but also it monitors dynamic characteristics, based on signals processing technology. FBG tilted meter monitoring system consists of sensors, multiplexers, interrogation units, local computers and remote computers, as it is shown in Fig. 2.

FBG tilted meter is installed on balancing level bearing to control reciprocal motion of lower roll.

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Figure 1 – Configuration of tilted meter monitoring system of fiber Bragg grating (FBG) [13]

Figure 2 shows interrogation system of signals from polarization sensors on the basis of TFBG structures. Important advance feature of interrogation system of signals from polarization sensors on the basis of TFBG structures is the fact, that all used in it elements are passive.

Therefore, it owns all advantages, inherent to fiber-optic sensors. Block schematic diagram, demonstrating the method’s idea is given in the Figure 8. Important practical aspect of the system thereof is insensitivity to the light source capacity fluctuations.

In the work [14] there has been developed the interrogation system of signals, entering from rotation sensors. TFBG structure and principles are illustrated in Fig. 1.

Figure 2 – Interrogation system of signals from polarization sensors on the basis of TFBG structures [13]

Apart from that, temperature insensitivity of TFBG transformer, FBG 1 and FBG 2 optical filters, stored on one optical fiber, single mode, is similar and constitutes approximately 10 pm / ° С. It means, that, if all optical elements are under one and the same ambient temperature, their characteristics, spectral shift will be the same, which assumes the possibility of conducting measuring the bend angle of falling polarization plane, insensitive to temperature changes.

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Braggа fiber grating resonant wavelength depends on effective refraction index (RI) of optical fiber core and RI modulation period. In turn, those two parameters depend on external deforming strains and temperature. Displacement of central refraction wavelength under deformation impact and temperature can be written as follows:

T T T n

l n n l

l n

eff eff eff

eff

BG 

 









 



 





 









 







 2 2 . (1)

The first sum in the expression (1) shows deformation impact on the fiber. Its physical meaning is in changing the grating period and RI, stimulated with elastooptical effect. That effect can be described as follows:

 1 p

_e

 ( Z )

BG

 

  



, (2)

where pe – effective elastooptical constant, defined as: where p11 and p12 – are components of elastooptical tenser, n – core RI, and ν– Poisson ratio. For standard single mode optic fiber with parameters p11 = 0,113, p12 = 0,252, ν = 0,16 and n = 1,482 at FBG refraction wavelength λВ0 ≈ 1550 Nm design sensitivity to deformation is 1,2 pm at relative extension ε(z)=10^-6.

Such shift λB at temperature change ΔT can be written as:



_e

 Т

B

  

    

where α = (1/Λ)(δΛ/δT) - thermal expansion factor (for quartz α

=0,55 ×10-6), ξ =(1/n)(δn/δT) – thermo-optic coefficient (for fibers with germanium additives equals approximately to 8,6×10-6).

It is seen, that RI change is a dominant effect. Bragg grating temperature shift in a single mode optic fiber is ~ 13,7 pm/°С.

Results and discussion.

In 2020 scientists of the Institute of information and computational technologies of the Ministry of education and science, RK developed and studied fiber-optic refractometer (sensor) [14].

Figure 3 – Principal diagram of fiber-optic refractometer (sensor)

Figure 3 demonstrates principal diagram of fiber-optic refractometer (sensor). Operation of the offered installation is fulfilled as follows.

The given fiber-optic refractometer’s novelty is in the fact, that fiber-optic refractometer with Bragg tilted grating considerably simplifies the media refraction index measuring system, as well, it does not demand spectrophotometers and optic spectrum analyzers usage and does not

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require applying optical spectrum analysis algorithms. Invention’s important peculiarity is measurements independence on ambient temperature and electromagnetic field influence at measurement spot, due to the fact, that the gratings have been recorded on one and the same multimode fiber. Fiber-optic refractometer usage also eliminates the problem of light source capacity fluctuations at the expense of the fact, that refractive index measure is the capacity ratio, measured by two photo receivers.

Also the distinction is, that fiber-optic refractometer consists of wideband light source with white beam, connected through multimode optical fiber to Bragg tilted grating, which is coupled by means of multimode optical fiber with optical connector, and outlet of the first optical connector is coupled by means of multimode optical fiber with the first optical circulator, with which the first Bragg grating with linear variable period is connected, by means of multimode optical fiber, which is additionally coupled through the first optical circulator, by means of multimode optical fiber with the first photo receiver, while the second optical connector outlet is switched on for multimode optical fiber to the second optical circulator, which by means of multimode optical fiber is connected to the second Bragg grating with linear variable period, which is additionally switched on through the second optical circulator, using one photo receiver (1,5 hours) , to the second photo receiver.

The proposed remote monitoring system works as follows (Figure 4).

Figure 4 – Remote system of distant monitoring

Building and engineering structures, Bragg tilted grating fiber-optic sensor, Signal forming system, power unit, telephone line

Internet Office Signals processing in MatLab.

Offered system of distant monitoring operates as follows:

Embedded Bragg fiber-optic sensors with tilted grating transfer data to own system of signal conditioner along fiber-optic cables, located in the channels for protecting from the environment. The signal from power source is reliably connected through telephone system to the Internet, from where the data can be easily extracted and processed from the office by means of MatLab software.

Experimental works have been carried out in the Republic of Kazakhstan, Almaty oblast at Issyk river bridge, which has the length of 70 m and is used for transport and people movement. The structure was constructed in 1950th, but there occurred mudflow and the bridge was restored in 1999. The bridge has vertical walls, constraining embankments, they are manufactured form heavy concrete blocks. Bridge structure was fortified by means of fluidic- water-shutoff strings, blocks were connected with vertical steel bars; buckling resistance was

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improved with constant active sinews, mounted along the total bridge length. To control displacements, harbor wall was equipped with a sensor, located beneath the bridge along upper blocks.

Figure 5 – Issyk river bridge, Almaty oblast, sensor placement sketch

At such bridge location we can compute linear deformation in three corners, as well, curvature in vertical and horizontal planes. At this stage there has been created the monitoring system for revealing normal structure behavior, in order to interpret deviations from that behavior as potential disaster sign at later stage, when the works are executed. The system functions since autumn of 2000.

Figure 6 – Temperature curvature graph in gaging cut set

For the first time the sensors have been used separately for quantitative assessing the concrete shrinkage and studying characteristics of different concrete mixtures structures. After the bridge construction was completed, the sensors were joined to compute horizontal and vertical curvature of each cell. During load tests, carried out in May, 1998 subsequent to construction completion, the bridge vertical displacement was monitored with mechanical sensors and compared with outcomes of computation, performed according to sensors readings, using the above-mentioned procedure. The algorithm restored the first pile position and accurately simulate vertical displacement, measured with mechanical sensors.

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Figure 7 – Tests on the bridge at Issyk river, Almaty oblast, Kazakhstan

To confirm the sensors accuracy at dynamic impact there were also conducted bridge dynamic tests with running trucks at different speeds. Sensor deformation dynamic response in case of a truck, travelling with maximum speed of 100 km per hour is shown in Figure 8.

Figure 8 – Sensor deformation dynamic response

From Figure 8 there might be drawn a conclusion, that bending moment, corresponding to motion level, coincides with the data, recorded within remote monitoring. It is stated, that tentative cases of deformation and curvature correlate with ambient temperature. No correlation with the activities at the terminal are revealed. Wall mechanics interpretation by means of analytical methods is rather tedious due to interrelation complexity between blocks and ambiguousness in joints health. There is carried out response characteristic by means of statistical models.

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Figure 9 – Moment dependence on curvature for bridge cross section

From Figure 9 there might be made a conclusion, that the bridge strength capability considerably exceeds the limited need in the moment, accepted within the process designing, also it can be said, that the data, collected by means of distant monitoring proves, that current project specifications of the bridges, constructed from concrete are rather conservative. To confirm that conclusion it is needed to conduct further researches and data collection. Moreover, further investigations and data analysis shall be carried out at final stage.

Figure 10 demonstrates outcomes of developed FBG sensor’s performance tests.

Amplitude-frequency curve, obtained upon impact of various frequencies from 0,5 to 21,5 Hz with acceleration 0,2 m/с². It might be noticed, that resonance frequency is approximately 16 Hz, which exceeds demanded 6 Hz and meets the monitoring requirements. As it is shown on Fig.

3b, test on acceleration was repeated three times. Average data was usable for obtaining sensitivity as 110,789 pm/(m/с2), and measurement showed favorable repeatability of 4 %.

a) b)

Figure 10 - Checking the operability of fiber Bragg grating at Issyk river bridge, Kazakhstan: а) amplitude-frequency curve; б) accelerating characteristic curve

Conclusions.

The article herein presents an example of Bragg fiber-optic sensors application to distant monitoring bridge structures health in the Republic of Kazakhstan, Almaty oblast at Issyk river.

At Issyk river bridge there were installed sensors. The bridge is considered to be the first smart

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structure in Kazakhstan, Almaty oblast. Bragg sensors were attached beneath the bridge. There were carried out static and dynamic tests of the bridge under trucks and automobiles. Obtained outcomes confirmed Bragg sensor accuracy upon assessing the bridge behavior upon road loads.

At conducting experimental loads there has been computed amplitude-frequency curve, obtained under the impact of various frequencies from 0,5 to 21,5 Hz with 0,2 m/с2 acceleration. It can be noticed, that resonance frequency constitutes approximately 16 Hz, which exceeds demanded 6 Hz and meets monitoring requirements. Test on acceleration has been repeated three times.

Average data are usable for obtaining the sensitivity for 110,789 pm/(m/с2), and measurement has shown favorable repeatability of 4%.

This work is supported by grant from the Ministry of Education and Science of the Republic of Kazakhstan within the framework of the Project № AP09259547 «Development of a system of distributed fiber-optic sensors based on fiber Bragg gratings for monitoring the state of building structures», Institute Information and Computational Technologies CS MES RK.

Experimental researches have been carried out in the laboratories of optoelectronics at the Electric engineering and computer sciences faculty of Lublin Technical University.

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[13] Kozbakova Ainur, Piotr Kisała, Wójcik Waldemar, Kalizhanova Aliya, Mamyrbayev Orken & Akhmetzhanov Maksat. Interrogation system of signals from rotation sensors using tilted fiber Bragg gratings // Cogent Engineering – 2020. – P. 1743405

[14] Калижанова А. У., Кунелбаев М. М., Козбакова А. Х. Патент на полезную модель «Волоконно-оптический датчик для контроля состояния инженерных и строительных конструкций» № 6254, 021/0303.2 от 29.03.2021

Әлия Қалижанова, ф.-м.ғ.к., ҚР БҒМ ҒК Ақпараттық және есептеуіш технологиялар институты, Алматы энергетика және байланыс университеті, Алматы, Қазақстан, [email protected]

Айнұр Козбакова, PhD, ҚР БҒМ ҒК Ақпараттық және есептеуіш технологиялар институты, Алматы технологиялық университеті, Алматы, Қазақстан, [email protected]

Мұрат Кунелбаев, PhD, ҚР БҒМ ҒК Ақпараттық және есептеуіш технологиялар институты, [email protected]

Жалау Айтқұлов, ҚР БҒМ ҒК Ақпараттық және есептеуіш технологиялар институты, Алматы логистика және көлік Академиясы, Қазақстан, [email protected]

Жазира Амиргалиева, PhD, ҚР БҒМ ҒК Ақпараттық және есептеуіш технологиялар институты, Алматы, Қазақстан, [email protected]

БРЭГ ТАЛШЫҚТАРЫ НЕГІЗІНДЕГІ ТАЛШЫҚТЫ-ОПТИКАЛЫҚ ДАТЧИКТЕРДІҢ ҮЛЕСТІРІЛГЕН ЖҮЙЕСІН ҚҰРУ

Аңдатпа. Бұл мақалада Қазақстандағы, Алматы облысындағы, Есік өзеніндегі көпір конструкциясының жай-күйін тестілеу және қашықтықтан бақылау қарастырылады.

Есік өзеніндегі көпірдің жалпы ұзындығы 70 метр және ені 6 метр палуба түріндегі құрылыс болып табылады. Аралық құрылым 10 дюймдік монолитті темірбетон плитасынан тұрады және әрқайсысы 5 қададан тұратын алдын-ала созылған қадаларға сүйенеді. Көпірдің күйін қашықтан бақылауға арналған көлбеу Брэгг торлы ақылды оптикалық-талшықты датчиккөпірдің төменгі жағында орналасқан. Жүктелген жүк көліктері мен автомобильдердің ауырлығына көпірге статикалық және динамикалық сынақтары жүргізілді. Датчик үнемі бір орында орнатылған деректерді жинау жүйесіне қосылды. Жиналған мәліметтер, сондай-ақ аналитикалық зерттеулер көпірлердің қазіргі жобалық сипаттамалары консервативті болып табылады. Осы жұмыс шеңберінде құрылған технология көпір құрылыстарына практикалық, экономикалық тиімді және сенімді жүйелі техникалық қызмет көрсетуді жүзеге асыруға мүмкіндік береді, ал зерттеу осы технологияның Алматы облысында Қазақстанның басқа да облыстарында болашақта таралуы үшін бірегей мүмкіндік береді.

Түйінді сөздер. Оптикалық-талшықты датчиктер; құрылымдардың жай-күйін бақылау; үлестірілген оптикалық-талшықты датчик; уақытша аймақтың оптикалық рефлектометрі; азаматтық құрылыс

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Алия Калижанова, к.ф.-м.н, профессор, Институт информационных и вычислительных технологий КН МОН РК, Алматинский университет энергетики и связи, Алматы, Казахстан; [email protected]

Айнур Козбакова, PhD, Институт информационных и вычислительных технологий КН МОН РК, Алматинский технологический университет, Алматы, Казахстан;

[email protected]

Мурат Кунелбаев Институт информационных и вычислительных технологий КН МОН РК, [email protected]

Жалау Айткулов, Институт информационных и вычислительных технологий КН МОН РК, Академия логистики и транспорта, Алматы, Казахстан, [email protected]

Жазира Амиргалиева, PhD, Институт информационных и вычислительных технологий КН МОН РК, Алматы, Казахстан, [email protected]

РАЗРАБОТКА СИСТЕМЫ ИЗ ВОЛОКОННО-ОПТИЧЕСКИХ ДАТЧИКОВ НА ОСНОВЕ ВОЛОКОННЫХ РЕШЕТОК БРЭГГА

Аннотация. В данной статье рассматривается тестирование и дистанционный мониторинг состояния мостовой конструкции в Казахстане, Алматинской области, на реке Иссык. Мост на реке Иссык представляет собой сооружение палубного типа общей длиной 70 метров и шириной 6 метров. Пролетное строение состоит из 10-дюймовой монолитной железобетонной плиты и опирается на предварительно напряженные свайные изгибы, каждая из которых состоит из 5 свай. Умный волоконно - оптический датчик с наклонной решеткой Брэгга для дистанционного мониторинга состояния встроен внизу моста. Были произведены статические и динамические испытания моста на нагруженных грузовиках и автомобилях. Датчик был подключен к системе сбора данных, постоянно установленной на месте. Собранные данные, а также аналитические исследования свидетельствуют о том, что текущие проектные спецификации мостов являются консервативными. Технология, разработанная в рамках этой работы, позволит осуществлять практическое, экономически эффективное и надежное систематическое техническое обслуживание мостовых сооружений, а исследование предоставит уникальную возможность для будущего роста этой технологии в Алматинской области в других областях Казахстана.

Ключевые слова. Волоконно-оптические датчики; мониторинг состояния конструкций; распределенный волоконно-оптический датчик; оптический рефлектометр временной области; гражданское строительство.

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