土木工程專業(yè)用低變形傳感器監(jiān)測民用工程結構變形的一致性畢業(yè)論文外文文獻翻譯及原文

1、畢業(yè)設計（論文） 外文文獻翻譯文獻、資料中文題目：用低變形傳感器監(jiān)測民用工 程結構變形的一致性文獻、資料英文題目: 文獻、資料來源： 文獻、資料發(fā)表（出版）日期院（部）:專業(yè):班級:姓名:學號:指導教師:土木工程翻譯日期： 2017.02. 14題 i西北物流屮心2號樓沒計low-coherence deformation sensors for themonitoring of civil-engineering structuresd. inaudi3, a. elamarib, l. pfluga, n. gisinb, j. breguetb, s. vurpillot3"i

2、mac, laboratory of stress analysis, swiss federal institute of technology, ch-1015 lausanne，switzerland 'gap, group ofapplied physics -optical seciion, geneva university ch-1205 geneva, switzerlandreceived 25 january 1993; in revised form 8 march 1994; accepted 25 march 1994abstractan optical-fi

3、ber deformation sensor with a resolution of 10 pm and an operational range of 60 mm has been realized. the system is based on low-coherence interferometry in standard single-mode telecommunication fibers. it allows the monitoring of large structures over several months without noticeable drift. no c

4、ontinuous measurement is needed and the system is insensitive to variations of the fiber losses. this technique has been applied to the monitoring of a 20 m xs m xo.sm, 120 ton concrete slab over six months. it is possible to measure the shrinkage of concrete and its elastic coefficient during pre-s

5、training, giving reproducible results in good agreement with theoretical calculations and measurements performed on small concrete samples. this paper describes the optical arrangement and the procedures used to install optical fibers in concrete.keywor&： ikformation sensors; civil-engineering s

6、tructuresi. introductionboth the security of civil-engineering works and the law require a periodic monitoring of structures. the methods used for this purpose, such as triangulation，water levels or vibrating strings， arc often of tedious application and require one or many specialized operators. th

7、is complexity and the resulting costs limit the frequency of the measurements. furthermore， the spatial resolution is often poor and the observation is usually restricted to the surface of the object. there is thus a real demand for a tool allowing an internal, automatic and permanent monitoring of

8、structures with high accuracy and stability over periods typically of the order of 100 years for bridges. in this framework， fiber-optic smart structures (i.e.，structures with self-testing capabilities) are gaining in importance in many fields including aeronautics and composite material monitoring.

9、 this technology can be applied in civil engineering and in particular for the short- and long-time observation of large structures such as bridges， tall building frames， dams，tunnels，roads， airport runways， domes，pre-stressing and anchorage cables. the monitoring of such structures requires the dev

10、elopment of a measuring technique with high accuracy，stability and reliability over long periods. it has to beindependent of variations in the fiber losses and adapted to the adverse environment of a building site. to reduce the cost of the instrumentation， it is furthermore desirable to use the sam

11、e portable reading unit for the monitoring of multiple structures. we describe here asystem based on low-coherence interferometry responding to all these requirements.2. experimental arrangementthe measuring technique relies on an array of standard telecommunication optical fibers in mechanical cont

12、act with concrete. any deformation of the host structure results jn a change in the optical length of he fibers. each sensor line consists of two single-mode ibers: one measurement fiber in mechanical contact with the structure (glued or cemented) and a reference iber placed loose near the first one

13、 (in a pipe) in order to be at the same temperature. since the measurement technique monitors the length difference beween these two fibers，only the mechanical deformation will have an effect on the results while all other perurbations, such as thermally induced changes in the refractive index of th

14、e fibcrs.will affect the two in an identical way and cancel each another out. to measure the optical path difference between the two fibers，a low-coherence double interferometer in tandem configuration has been used (fig. 1) 1. the source is an led (light-emitting diode) working around 1.3 pm with a

15、 coherence length l， of 30 pm and a rated power of 200 pw. the radiation is launched into a single-mode fiber and then directedtoward the measurement and the reference fibers by means of a 50:50 single-mode directional coupler. at the ends of the fibers two mirrors reflect the light back to the coup

16、ler, where the beams arc recombined with a relative delay due to the length difference al， between the fibers，and then directed towards the second (reference) interferometer. the reference interferometer is of michelson type with one of the arms ended by a mobile mirrormounted on a micrometric displ

17、acementtable with aresolution of0.1 pmandan operating range of 50 mm.it allowstheintroduction of an exactly known path diffcrence al，between its two arms. this fiber interferometer is portable and needs no optical adjustment after transportation. it has been developed by the gap with the support of

18、the swiss ptt for optical cable testing 2.the intensityattheoutput of the reference inter- ferometerismeasured with a pig-tail photodiode and is then given by 3(1)(2)(3)(4)/ = /,十，2 + 2(，人)i/2p"(巾)cos(a</>)乙 zzg/ao/zs = zze(f 4- ?(da7cfl/ch?)az.2jwhere zz，r is the effective refractive ind

19、ex of the fiber，zzg the group refractive index (about 1% higher than nefr in silica)，a, the central vacuum wavelength of the light, zi” the autocorrelation function taking the spectral characteristics of the emission into account and al the physical path difference between the two interfering paths.

20、 further similar interference terms appear in eq. (1) in the special cases when al， <l， or al， < l，. when the optical path difference between the arms in the reference interferometer corresponds to the one induced by the two fibers installed in the structure (within the coherence length of the

21、 source), interference fringes appear. scanning al， with the mirror of the reference interferometer it is possible to obtain al = 0either with al， = al， or with al, = -al， and thus two interference fringe packets as described by eq. (i). the mirror position corresponding to al，=0 also produces an in

22、terference and is used as a reference. these three fringe packets arc detected by means of a lock-in amplifier synchronized with the mirror displacements. the mirror displacements and the digitalization of the lock-in output are earned out by means of a portable personal computer. since the referenc

23、e signal is generated separately and does not have a constant phase relation to the interference signal, only the envelope of the demodulated signal has a physical meaning and corresponds to the envelope of the fringe pattern. alock-in plot showing the three typical peaks is shown in fig. 2. each pe

24、ak has a width of about 30 pm. the calculation of its center of gravity determines its position with a precision better than 10 pm. this precision is the limiting factor of the whole measurement technique. since al， is known with micrometer precision， it is possible to follow al， with the same preci

25、sion.:;1v| nfig. 1. experimental setup of the low-coherence double michelson interferometer. d. innudi et al. 1 semors andlock-in-i1-*l.1.11-1.i.126002000ibuu10oo500o-3000-2000.1000oiooo3000mirror displacernem | ptn|fig. 2. typical fringe envelope as a function of the mirror position. the distance b

26、etween the central and the lateral peaks corresponds to the length difference between the measurement and the reference fibers mounted in the table. any change in the length of the structure results in a change in the position of these peaks. any change in the losses of the fibers will result in a c

27、hange of the height of the peaks. the central peak is fixed and used as a reference.the path difference al，is proportional to the de-formation of the structure al，with the relation between the two given by 4(5)als =o.887ajl14=1 -z2?f(i - /x)/?12- mpi i v2 = -78(in silica glass fibers)where p is pois

28、sons ratio and pij is the strain optic tensor (pockcls coefficients). the coefficient 5 takes into account the variation of the effective index neff in a fiber under strain. a degradation of one or both fibers (due to aging, for example) will result in a lower visibility of the fringes but will not

29、affect its position. the information about the deformation of the structure is encoded in the coherence properties of light and not in its intensity as in the majority of the sensors applied to date in civil-engineering structures, mostly based on microbend losses and/or optical time-domain reflecto

30、metry (otdr) techniques. interference peaks resulting from reflections as low as -30 db of the source power can be detected by our system without phase modulators. by modulating the phase in one of the four arms of the two interferometers, one can increase the dynamic range of the device to more tha

31、n 100 db 5】.even if the polarization dispersion and bend-induced birefringence in the sensing fibers could reduce the visibility of the interference fringes or even split the fringe packets, none of those effects was observed in our experiment. no adjustment of polarization between the reference and

32、 the sensing arm was then necessary. a good mechanical contact between the measurement fiber and the structure under test is fundamental. in this study a number of installation procedures have been tested and optimized for the different measurements (shrinkage，elasticity modulus, etc.). the mounting

33、 techniques can be divided into two main categories: full-length coupling and local coupling.during our tests five out of six optical fiber pairs with a 0.9 mm nylon coating, being mounted on the external face of a 20 m long plastic pipe and protected only with thin rubber bands (see fig. 3(a), surv

34、ived the concreting process. during the setting process the concrete envelops the fiber and realizes the desired mechanical contact. those fibers showed a minor increase in the scattering losses and the appearance of small parasite peaks. the measurements on those fibers were consistent with the res

35、ults obtained with other installation techniques (see below). it seems that for full-length coupling the nylon coating transmits the structure deformations (extension and shortening) entirely to the fiber core. this installation technique is very promising when compared to the usual procedure, consi

36、sting of a pipe protecting the fibers during the pouring of concrete and being removed before the setting process begins. this second method seems more adapted to small samples than to full-scale structures. eleven other fiber pairs were glued at the two ends of the table after removing locally the

37、protective coating layers of the fibers (see fig. 3(b). the silica fiber was ftxed with epoxy glue to a metallic plate mounted on the end faces of the concrete structure. the gluing length was about 20 mm. a pre-strain (between 0.1 and 0.4%) has been given to those fibers during the gluing process t

38、o keep them under tension and allow the measurement of both expansion and shrinkage of the structure. this type of local coupling proved to be the most reliable, but was not adapted to following the deformation during the pre-stressing of the table because of the important surface deformations occur

39、ring during this operation. the problem has been overcome by gluing other fibers inside the pipes at about two meters from the surfaces, i.e., far from the force insertion region (see fig. 3(c).(c)fig. 3. schematic representation of three of the installation techniques used:(a) direct concreting of

40、the measurement fiber mounted on a plastic pipe; (b) fiber glued at the table surface; (c) fiber glued inside the pipe at 2m from the pipe ends.side viewfig. 4. top and side views of the concrete table measured in the experiment and position of thesensing-fiber pairs a, b, c and d. fibers a, b and c

41、 arc glued at the surface of the structure, while fiber d is glued inside a pipe, 2 m away from the surface of the slab. twelve more fihcr pairs were installed, but are not shown for simplicity.luon望 oleoto study the possible effect of creep in strained fibers 6, one fiber has been mounted on a mech

42、anical support that allows the fiber to be tightened only at the time of the measurement. no difference between this fiberand those permanently strained has been observed over a period of six months，confirming the assumption that no creep occurs for fiber strains below 1%. since the scanning range o

43、f the mirror is 5 mm, it was easy to cleave the 20 m long fibers within this margin. the fresnel reflection of the cleaved fibers combined with the high dynamic of the system allow a measurement of al，” this value of al, can than be used to correct the cutting and obtain pairs with length difference

44、s below 1 mm. two ferrules were then installed on the fiber ends and mounted in front of a polished inox surface. chemical silver deposition was also used to produce mirrors on the cleaved fiber ends.322o102030405060days after concretingfig. 6. comparison between the measurements performed on the st

45、ructure by optical fibers and the ones performed on 360 mm and 500 mm samples in a mechanical micrometer comparator. the measurement on the samples was possible only during the first two months.3. resultssul lsmeopqseveral long- and short-term measurements have been carried on a 20 m x 5 m x 0.5 m，1

46、20 ton concrete slab intended to be used as a vibration-isolated base for optical analysis (in particular by holographic and speckle interferometry) of large structures 7. this structure has been concreted indoors, allowing controlled environmental conditions and known concrete composition to be ach

47、ieved. samples have been prepared with the same material composition and are under permanent test for their mechanical properties (resistance， shrinkage and elastic coefficient). this allows a direct comparison between the results on the full-scale structure and the samples. thetable hasbeen pre-str

48、ained23 days after concreting inbothlength and width. it was possible at this time to measure the elastic coefficient of the material infull scale.fig.4 shows aschematic representation of thetableand the positionof the fibers referredto in the experimental results. atthetime of writing,thetable has

49、beenunder test for six months. overthisperiod the shrinkage in the longitudinal direction (i.e., over 20 m) has been about 6 mm. weshowin fig. 5 the resultsof the measurements for three (glued)fibers over 175days.the table has atprofile (fig. 4). it is evidentfromfig. 5 that thefibers mounted near t

50、he borders of the table，i.e., were the thickness is smaller, registered a larger shrinkage, as expected according to the concrete theory.adjacentfibers give consistent results independently of the installation technique. no difference has been noticed between the fibers under permanent tension and t

51、hose loosened between the measurements，suggesting that no creep of glass fibers occurred. the shrinkage measured with the fiber system has been compared during the first two months with the results obtained with a mechanical comparator mounted on two samples of 360 mm and 500 mm, respectively.the ob

52、served deformations have been scaled to 20m and are compared in fig. 6 to the results obtained with fibers b and c. very good agreement is found between the two measurements. a theoretical comparison between the experimentalresults and the swiss civil engineering standards has also been carried out.

53、 the experimental data and the standards are in agreement within f 10%. a more accurate simulation including the physico-chemical properties of the concrete used is under development. the table was pre-stressed 23 days after concreting. the five steel cablesrunning over the lengthofthe tableandthefo

54、rtycablesrunning over itswidth were stretched withaforce of185kn(18.5tons)each. thefibersglued to the surfaceand those indirect contact withconcreteover thewhole lengthmeasured anexpansion ofthe table insteadof the expected shrinkage. this is due to the important surface deformations occurring near

55、the force-insertion points, i.e., near the pre-stress heads that were placed near the fiber ends. fiber d glued inside the plastic pipe at 2m from each end was not subject to these local effects and measured a shortening of 0.23 mm. the theoretical calculation based on an elastic coefficient of 30 k

56、n/mm2 gives a shortening of 0.28mm at the borders and 0.19 mm at the center of the table. since fiber d was placed in an intermediate position, the experimental value can be considered to be in good agreement with the theory.4. conclusionsa new deformation sensor adapted to the monitoring of civil-e

57、ngineering structures has been proposed, it is based on low-coherence interferometry in standard lowcost telecommunication fibers. the resolution of the measurements is 10 pm, the operational range is 60mm and the stability has been tested over six months without noticeable drift. the reading unit i

58、s compact and portable, needing no optical alignment before the measurements. it is controlled by a portable personal computer, which is also responsible for the data treatment. the same reading unit can be used to monitor multiple fiber lines by simple manual unplugging. this technique is furthermore practically insensitive to increased losses due to degradation of the fibers. a test study has been carried out on a 20m 5m x 0.5m concrete slab, giving consistent results when compared to other measurement techniques based