ADVANCEMENT OF BRIDGE HEALTH MONITORING BASED ON DISTRIBUTED FIBER OPTIC SENSORS

Transcription

1 Abstact ADVANCEMENT OF BRIDGE HEALTH MONITORING BASED ON DISTRIBUTED FIBER OPTIC SENSORS Zhishen Wu 1, Suzhen Li and Koichi Yokoyama 3 Ove the past few yeas, ou lab has caied out a seies of studies based on advanced distibuted stain sensing techniques fo the development of an integated stuctual health monitoing (SHM) system. This pape pefoms a thoough and systematic eview on the impotant esults of this wok, including the development of a feasible distibuted long-gage stain sensing system fo pactical adaptation to civil stuctual engineeing, innovative analysis and intepetation of the measued data, as well as use of the geneated infomation to implement effective diagnosis and monitoing. Intoduction Stuctual health monitoing (SHM) fo on-line diagnosis of damage, assessment of the safety and integity of infastuctue, and evaluation of the emaining stuctual sevice life has eceived consideable inteest in contempoay liteatue. Most of the existing SHM eseach has focused eithe on global damage assessment techniques using stuctual dynamic esponses, o on limited local independent damage detection mechanisms. The amount of liteatue elated to this aea is quite extensive [1,, 3]. Some of the citical challenges pesently facing the development of civil SHM systems that ae lagely based on taditional, widely-used sensing technologies (e.g. acceleometes, velocimetes, displacement tansduces, and foil stain gauges) include the fact that: (1) Stuctues ae lage and complex but stuctual damage is usually localized; () Static fielding tests equie expensive equipments, laboious aangements, and suspension of the nomal woking condition of the stuctues; (3) The sensitivity of the fequency shift due to local damage is vey small despite the elatively high measuing pecision of the natual fequency fo vibation-based SHM. On the othe hand, the mode shape may be moe sensitive to damage but easily distubed by measuing noise. Futhemoe, limited by measuement pactice, it is often necessay to deive a moe eliable and effective index fo damage diagnosis fom the tanslational mode shape, such as a second diffeential to calculate cuvatue, which in tun geatly enhances the influence of the measuing noise and makes many algoithms theoetically feasible but pactically ineffective; (4) A citical issue egading FE model updating fo civil stuctues is that although 1 Pofesso, Dept. of Uban and Civil Engineeing, Ibaaki Univesity, Hitachi, Japan College of Civil Engineeing, Tongji Univesity, Shanghai, China 3 Pofesso, Dept. of Uban and Civil Engineeing, Ibaaki Univesity, Hitachi, Japan

2 the numbe of unknown paametes is usually lage, the measued esponses ae so limited that the invese o optimal algoithms seldom come to convegence and the updated esults ae had to evaluate; (5) Most taditional measuement vaiables, such as acceleation, velocity and displacement, ae essentially point measuements at a tanslational degee of feedom (DOF). Such tanslational esponses ae global quantities of stuctues which ae consideed insensitive and having no clea elationship to a specific incident of local damage, even fo those occuing nea the tansduces. Moeove, fo the case of multiple damage incidents at diffeent locations o fo diffeent kinds of damage, the situation will be extemely complicated. The mutual influence of stuctual damage on the measuements makes it difficult to pefom effective stuctual paametic and damage identification; (6) Stain may be the most sensitive paamete to local damage. Howeve, the influence of damage on a stain measuement cannot be eflected detemined effectively unless the aea whee the stain senso is fixed exactly coves the damaged egion. Howeve, this is difficult given the fact that stuctual damage is an abitay and unfoeseen phenomenon. Actually, taditional foil stain gauges ae fa fom taking the task to monito a stuctue not only owing to poblems concening stability, duability, long-tem eliability, as well as the difficulty fo lage aea distibuted placements. Theefoe, with egad to these existing obstacles which taditional SHM mannes may be fa fom ovecoming, as some expets stongly suggested, it is impotant to intoduce some inheently innovative elements to help the cuent SHM eseach get out of the dilemma. Based on advanced distibuted stain sensing techniques [4], a seies of systematic studies have been caied out in ou lab to put fowad an integated SHM system, as outlined in Fig. 1. This wok involves thee pats: the development of a feasible distibuted long-gage stain sensing system fo pactical adaptation to civil stuctual engineeing, the innovative analysis and intepetation of the measued data, and the use of geneated infomation to implement effective diagnostic and monitoing capability. Monitoed subject Distibuted measuement Distibuted sensos Senso development and pefomance chaacteization Static Dynamic t Fequency domain Modal analysis Time domain Modal paametes Steel stuctues RC stuctues Non-paametic scheme Senso coelation based method Two-level stategy Stuctual assessment and damage detection Fig. 1 An oveall view of this wok

3 A Distibuted Long-gage Fibe Optic Sensing System [5] A long-gage fibe optic senso aay based on a fibe Bagg gating (FBG) has been developed to implement distibuted static and dynamic stain sensing, as shown in Fig. 1. In spite of its high pecision and excellent dynamic measuing ability, the odinay FBG faces an unfavoable poblem in that its inheent gauge length is aound 1-cm, which makes FBG appopiate as taditional point stain gauge but inappopiate fo distibuted placement. Ou idea is to extend the senso gauge length by fist using a tube to sleeve the optical fibe and then fixing the two ends of the tube. (1) Unifom in-tube optical fibe () Recoated in-tube optical fibe fo enhancing SMF SM FBG Gauge length Epoxy esin L 1 Gauge length L Senso-1 Senso- Senso-m v i v f p j Reinfoced Cabon fibe/epoxy with esin Fibe- Epoxy composite esin composites Maco-stain hm v v m Lm h: the distance fom the inetia axis to the bottom of a beam L: senso gauge length v: otational displacement i j Connecto (3) Gauge lengths (sensing pats) Fig. Long-gage FBG senso aay FBG Connecto Fo a geneal long-gage senso (Fig. (1)), the in-tube fibe has the same mechanical behavio and hence the stain tansfeed fom the shift of Bagg cente wavelength epesents the aveage stain (o say maco-stain) ove the senso gauge length. In ode to obtain effective measuements in the case whee the stain esponse is vey small o envionmental noise is lage, an impoved packaging design is poposed to enhance the measuing sensitivity of long-gage FBG sensos (Fig. ()) by utilizing two mateials with diffeent modulus to package the optic fibe and to impose defomation within the gauge length L, lagely on the essential sensing pat of the FBG L1. Afte connecting the long-gage sensos in seies, an FBG senso aay can be ealized, fo distibuted maco-stain measuements (Fig. (3)). Poof tests have veified the ability of the developed sensos fo both static and dynamic measuements. The developed sensos ae chaacteized by thei capability to obtain measuements that integate both local and global infomation, which is due to the fact that: (1) stain is typically a local esponse; () distibuted senso placement helps to ecod the data coveing the lage egion of a stuctue; (3) a the high sampling ate of FBG inteogato makes it possible to obtain boad-band spectum and global modal paametes. Widely-used tansduces, such as acceleometes, velocimetes and displacement tansduces essentially povide some kind of measuement of the tanslational degees of feedom (DOFs). In contast, the maco-stains fom long-gage FBG sensos have a clea

4 elation with otational displacements (see Fig. ). In light of this featue, the novel sensos can pefom similaly to conventional tansduces. What is moe impotant is that maco-stain measuements ae moe sensitive to damage and can be diectly applied fo damage detection with no equiement fo a detailed analytical model o say a baseline stuctue. SHM Stategy Based on Static Sensing Health Monitoing of Steel Flexual Stuctues [6] To chaacteize the ascendancy of the developed sensing system and povide a valuable efeence fo long-tem monitoing, the eseach concening pactical application of the innovative sensos in SHM begins with expeimental investigations of steel flexual stuctues. Steel beams with I-shaped coss-section ae designed as the test specimens, suppoted at two points and installed by vaious sensos, as shown in Fig. 3. By and lage, this pat of the wok is devoted to the compaison of the newly developed and the taditional sensos fom the pespective of SHM P (Unit: mm) A1 A A3 A4 A5 A6 A7 A8 A9 Saw-cut location Fusion welding Fusion welding Cell1 Cell Cell3 Cell4 Cell5 Cell6 Cell7 Cell8 Cell9 D1 D D3 D4 D6 D7 D8 D9 D5 F1 F F3 F4 F5 F6 F7 F: FBG senso B1 B B3 B4 B5 B6 B7 B8 A, B: stain gauge B9 D: LVDT = C1: Intact C:Cack1 C3:Cack Fig. 3 Steel specimens and senso placement Since thee is no equiement fo an analytical model, damage identification can be pefomed by diectly utilizing the measuements fom vaious sensos. Focusing on the pue bending sections, including Cell4, Cell5 and Cell6, the identified esults in the case of small damage (C) ae displayed in Fig. 4. Appaently, the FBG-based method is effective, as the measuements fom F3, F4 and F5 fo the intact beam agee well, while those fom F4 obviously deviate fom the data obtained by F3 and F5 fo the damaged beam. Compaatively, it seems that the measuements fom the stain gauge, which is installed pecisely at the location whee the cack damages ae peset (B5), diffe emakably fom the othe measuements. Howeve, the stain gauges placed at multiple points face a vey unfavoable poblem: the measued esponses ae so concentated on the local infomation that they ae too vulneable to localized uncetainties to eflect damage accuately. Moeove, at least one senso must be fixed exactly to the damaged aea, which is difficult to implement by employing such point sensos fo lage-scale stuctues due to the fact that damage is an abitay and unfoeseen phenomenon inheent in the stuctues. Fo diect measuement of the global displacement paamete, cuvatues ae usually constucted via cental diffeentiation as the featues of inteest fo damage

5 detection. It can be seen fom Fig. 4 (3) that the featues obtained in this way ae seiously distubed by measuing noise and fail to identify the damages pactically. Load(KN) (1) FBG sensos () Stain gauges (3) LVDTs Maco-stain(µ) Maco-stain(µ) Stain (µ) Fig. 4 Model-fee damage identification based on vaious sensos The intact beam C1 is specially selected fo stuctual paametic estimation. A finite element (FE) model is fist established and model updating is caied out to bidge the gap between the numeical model and expeimental measuements. The flexual stiffness of the beam coesponding to each cell is consideed as an object paamete fo identification. An optimization-iteative algoithm (see Fig. 5 (1)) is then employed to estimate stuctual paametes based on the static maco-stain distibution fom the FBG senso seies as well as the displacement esponses fom LVDTs. As shown in Fig. 5, the satisfied esults can be achieved based on a maco-stain distibution with the maximum eo below 10%, wheeas the algoithm fails to convege to a stable solution in the case of displacement measuements. Theefoe, a significant fact can be claimed, which is that distibuted long-gage sensos, athe than LVDTs, ae moe suitable fo stuctual paametic estimation because maco-stain, unlike displacement, only esponds to extenal influences such as loads o stuctual damages in the aea whee the coesponding senso is installed and is inetia to those in the othe aeas. Real Stuctue R m FE Model p, 0 P R a 0 EoE(P) E( P)? Yes Done s(p) p p p E( p) No (1) Optimal-iteative algoithm fo paametic estimation based on static sensing s ( p) p Load(KN) () Paametic estimation based on maco-stain distibution (3) Paametic estimation based on displacement measuements E(p) Fig. 5 Model-based paametic estimation based on vaious sensos Load(KN) Cuvatue Iteative times Cell 1 Cell Cell 3 Cell 4 Cell 5 Cell 6 Cell 7 Cell 8 Cell 9 Iteative times Cell 1 Cell Cell 3 Cell 4 Cell 5-1 Cell 5- Cell 6 Cell 7 Cell 8 Cell 9 E( p) E E-07 Exact Eo (%) E E+00 0 NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN

6 An inteesting idea is poposed hee fo long-tem stuctual health monitoing based on the coelations of the static stain distibution. Conside the above expeimental esults. At a cetain time, seven static maco-stain measuements fom F1~F7 can be obtained. Take the data fom F1 as a efeence, fo example. Given a coodinate system with maco-stain values fom the efeence senso on the x axis and those fom all the sensos on the y axis, seven points ae dawn fom this measuement. Suppose that the data is ecoded at a cetain sampling ate. Appaently, as is shown in Fig. 6, if thee is no damage, the points coesponding to a senso ae all located on a staight line with a detemined slope. When damage happens, the points will seveely deviate fom the oiginal tack and eventually sit on a staight line with anothe slope. The advantage of this method lies in the fact that the indication to damage is sensitive and statistically eliable, which will geatly educe the distubance due to measuing eos and envionmental noise. An impotant issue woth noting is that the efeence sensos should be those installed onto the aea with the minimum pobability of incuing damage duing the stuctual in-sevice tem, such as the pats o membes undegoing a elatively small load, having excellent mateial popeties, o seving in a good envionmental condition, etc. Maco-stains of all sensos (µ) F1 F3 F5 F7 one ecod at a cetain time F F4 F6 damage occus at Cell 5 whee F4 is fixed Maco-stains of the efeence senso F1 (µ) Fig. 6 Long-tem monitoing based on the coelations of static stain distibution Health Monitoing of RC Flexual Stuctues [7] Health monitoing of RC stuctues often includes two main concens with egad to local damage detection and global stuctual behavio. A nomal RC beam with a flexual failue mode in the design is taken as an example fo ou expeimental investigations. FBG sensos of diffeent gauge lengths ae installed onto the bottom suface of the beam, as illustated in Fig. 7. The impotant findings concening the behavio of FBG sensos in the application of RC stuctues ae summaized as follows: (1) The FBG senso aay can effectively detect the occuence, location and extent of cacks. With an incease in gauge length, FBG senso may weaken the stess/stain concentation (Fig. 7 (1)); () The maco-stains measued by a senso of gauge length 0.4m o longe pesent a pefect linea coelation with the deflections at the mid-span fom a displacement tansduce (Fig. 7 ()). This leads to the vey valuable conclusion that as long as the distibuted sensos ae easonably installed, they can eplace the displacement

7 tansduce, which is often used fo global displacement measuements but is difficult to affix to pactical civil stuctues due to the baseline position equiement; (3) The maco-stains ove a gauge length of 800mm fom the FBG sensos of diffeent gauge lengths ae compaed in Fig. 7 (3). The nice ageements veify that maco-stain measuements ove a cetain gauge length can be obtained fom the aveage of those ove seveal sub-gauge lengths. In the othe wods, the fou distibuted FBG sensos of 00mm gauge length can also act as the stain sensos of 400mm, 600mm and 800mm gauge length D F1, F, F3, F4 F6, F5 F7 S1~S1 C1~C Zone1 Zone Zone3 Zone4 F: FBG senso S: stain gauge C: cack gauge D: displacement tansduce load(kn) S8(60mm) F3(00mm) F5(400mm) F7(800mm) Maco-stain(µ) (1) Detection of fist cack Deflection(m Initiation of fist cack Yielding of ebas Maco-stain(µ) () Deflection vs. maco-stain cuves (3) The aveage of maco-stain measuements Fig. 7 Expeimental investigations on a nomal RC beam load(kn) (F1+F+F3+F4)/4 (F5+F6)/ F7 Maco-stain(µ) On the othe hand, by employing a typical fibe section model (Fig. 8) on the basis of the plane section assumption, the nonlinea behavio of this RC beam is simulated. It is confimed that the load vs. maco-stain elations match well with the analytic esults befoe initiation of the fist cacks and have close ageement with those afte cacking. This confimation is impotant because it ensues that the maco-stain measuements, unlike taditional point measuements, may epesent the stain esponses fo the plane section. That is to say, by vitue of the distibuted long-gage sensos, a solid inteelation of the measued stain esponse, stuctual paametes including mateial and geometic popeties, as well as loads can be constucted based on classic bending theoy. Any one of them can be estimated as the othes ae known in advance. Theefoe, the method of invese analysis is poposed fo load o paametic identification of RC flexual stuctues. Combined with expeimental and analytical investigations, an integated health monitoing stategy fo RC flexual stuctues based on the developed long-gage fibe optic sensos aay is finally put fowad in Fig. 9, including: (a) local damage

8 identification, (b) paametic estimation, and (c) global behavio evaluation. Y Y1 ' A s 1 h i h A s n b d i Z i ' a a ' Z s Z s i s M ' s 0 s t i ' c ' s Load(KN) Initiation of fist cack Yielding of eba Maco-stain(µ) Fig. 8 Fibe section model fo simulation Cell i MP: mateial paamete GP: geometic paamete Distibuted long-gage FBG sensos aay Maco-stain distibution Contolled Static Load Cack monitoing Detection Locating Invese Analysis Load level identification MP estimation Aveage cuvatue fo cell i: i Cack width GP estimation Conjugated beam Damage identification Paametic estimation Global behavio evaluation Deflection distibution RC stuctual health monitoing Fig. 9 SHM stategy on RC flexual stuctues based on static sensing SHM Stategy Based on Dynamic Sensing As is summaized in Fig. 1, the SHM eseach based on dynamic sensing is appoached fom two angles: the time and fequency domain. Many yeas ago, a neual netwok based algoithm was poposed fo damage identification using time-seies data. Inteested eades can go diectly to the efeences [8, 9]. Anothe scheme developed in the fequency domain will be stessed hee instead. Afte pefoming modal analysis, two damage identification methods ae pesented by using modal paametes extacted fom dynamic maco-stain esponses. Modal Analysis Concening Distibuted Stain Measuements [10] This pat of the wok elaboates theoetical and expeimental modal analyses on the dynamic stain distibution fo the sake of data pocessing and featue extaction. Fom the pespective of the time and fequency domains, the maco-stain fequency esponse function (FRF) moe closely esembles a displacement FRF than a velocity o acceleation

9 one, which leads to the esult that the elation between the maco-stain FRF vesus fequency can povide a moe sensitive indicato at low modes, especially when the esonant fequencies ae small (see Fig. 10). This featue may be valuable fo the on-line monitoing of stuctues of high flexibility, such as long-span bidges with initial fequencies having vey small values (1 ad/s o even 0.1 ad/s) and densely congegating. Although dynamic displacement esponses can theoetically play the same ole, so fa it is still difficult to obtain effective eal-time measuements in tue civil engineeing stuctues due to the lack of effective displacement sensos. With espect to modal paametes, the identified esonant fequency and damping atio fom dynamic maco-stain measuements have the same pecision as those fom conventional tansduces like acceleometes o stain gauges, as listed in Fig. 10. In paticula, the esonant fequency povides a vey high identified pecision which is below Maco-stain FRF m H mp P H H mp mp p M N 1 M j m i j p m p i j p M Modal maco-stain vecto (MMSV) 1,,, m, T m i Consideing magnitude Fequency, damping atio j m Acceleation FRF a vl Hlp P H a lp same H a lp N l p 1 M j p M l p 1 p l Mode shape 1,,, l T, M Sensos FBG senso Acceleomete Stain gauge Fequency Damping atio Fequency Damping atio Fequency Damping atio case case case case case case Fig. 10 FRFs and modal paametes It is woth emphasizing that simila to mode shape, a special modal paamete, called modal maco-stain vecto (MMSV), can be extacted fom distibuted maco-stain measuements. It has been theoetically and expeimentally veified that the MMSV vesus the mode shape have the same mapping elation as the time-seies and fequency esponses

10 of the measued maco-stain vesus displacement esponses. This inteesting finding confims that the MMSV is actually a diect measuement of the cuvatue/stain mode shape and hence has moe sensitivity to local damage and is subject to fewe distubances fom measuing eos. Sensos Coelation based Damage Identification [11] Based on the coelation within the dynamic maco-stain distibution, a stategy with no equiements fo an analytical model has been poposed fo damage locating and quantifying. Many numeical simulations on flexual stuctues yield a quantitative elation of damage index vs. damage seveity, as is shown in Fig. 11 (1), whee the damage index is given as the elative eo of the nomalized MMSV. It should be noted that pe-estimation of the pecentage of the senso gauge length subject to localized damage (e.g. n= in Fig. 11 () means the senso gauge length is divided by and the pecentage is 50%) can enable moe accuate quantification of the extent of damage. (%) (%) (1) () Damage extent Fig. 11 Damage index vs. damage seveity elations based on sensos coelation Taking a beam stuctue with fou distibuted long-gage FBG sensos as an example, Fig. 1 descibes the pocess fo featue extaction and damage identification. Unde an excitation case, the maco-stain esponses fom all sensos ae ecoded (Fig. 1 (1)). Via the FFT, the MMSV can be constucted fom the peak values of the stain magnitude FRF. It is obvious fom Fig. 1 () that the MMSVs fom seveal cases whee single-point hamme impulsive excitation is applied at abitay locations with abitay amplitudes ae linealy coelated. The slopes of the fitted lines ae then taken as the featues fo futhe damage identification. In fact, these featues ae the nomalized MMSV, taking the MMS fom S1 as a efeence. Moeove, the fitted line is a type of statistical esult, which can be helpful in educing andom eos by fitting the measuements fom vaious load cases. As is listed in Fig. 1 (3), the featues pesent a nice indication fo damage locating and quantifying. Two-level Stategy fo Damage Identification [1, 13] Consideing the difficulty of identifying damage in lage-scale stuctues (due to such poblems as ill-conditioning, slow convegence, and occasional non-uniqueness when thee ae many unknown paametes fo the invese and optimal analysis), a Damage extent(%) n=1 n= n=3 n=4 n=5 n=6 n=7 n=8

11 two-level damage detection stategy using modal paametes extacted fom distibuted maco-stain data is poposed (see Fig. 13). Level 1 of the MMSV-based damage index method is fist pefomed fo locating damage with a spatial esolution of the gauge lengths of fibe optic sensos. Heeafte, the numbe of candidate paametes to be identified is shaply educed and level of the natual-fequency-based damage quantification can be then caied out. This step-by-step pocedue helps to utilize data with diffeent measuing pecisions, i.e., locate the damage using low quality data (e.g. the MMSV) and then to quantify the damage using the paametes of high pecision (e.g. fequency). Expeimental esults of a cantileveed beam have veified the effectiveness and applicability of the poposed two-level stategy. C1: Intact beam 3 50 F4 F3 () Modal macostain unde seveal cases Fig. 1 Model-fee damage identification based on dynamic maco-stain distibution Conclusions MMSs fo FBG sensos Senso C: Beam with one damage at element 6 C3: Beam with two damages at elements 6,10 C1F1 C1F C1F3 C1F4 MMS fo S1 One case C1 F1 (3) Featue extaction (slope of the lines in () ) and damage identification C1 C C3 MMSV MMSV Damage extent (1) Macostain esponse s unde an excitation A seies of studies on the development and application of distibuted fibe optic sensing techniques in SHM ae summaized. The following achievements and contibutions show the oiginality and significance of this wok to the existing state of knowledge concening health monitoing fo civil stuctues. (1) A feasible distibuted long-gage stain sensing system based on a FBG is n=1 n=4 set MMSV (1) F C1 Damage extent n=1 n=4 set F % % F % 1.0% 51.5% 5% % 0.9% 51.3% 5% F % 1.0% 8.5% % 1.3% 5.1% 5% F % 1.5% 9.8% % 0 0 0

12 developed fo pactical adaptation to civil stuctual engineeing. The pefomance of the developed sensos as well as that of the FBG inteogatos is chaacteized on the basis of accuacy, pecision, stability and eliability unde static and dynamic tests. () An integated SHM stategy on a steel flexual stuctue based on static maco-stain distibution has been poposed fo stuctual damage identification, paametic estimation, and global behavio evaluation. (3) An integated SHM stategy on a RC flexual stuctue has been put fowad concening: local cack monitoing, paametic estimation based on nonlinea invese analysis, and global behavio evaluation in tems of stuctual deflection distibution. (4) Modal analysis is specially addessed fo dynamic maco-stain distibution. The method fo modal testing, esponse FRF measuement, modal paamete extaction, and data intepetation has been established. (5) A model-fee method based on the coelation among the distibuted fibe optic sensos is developed fo damage locating and quantifying (6) A two-level damage detection stategy is poposed by using modal paametes extacted fom dynamic distibuted stain data to settle the conflict between the lage numbe of unknown paametes and the limited quantities of measued stuctual esponses. It pocesses using a two level stategy: (1) level 1 uses an MMSV-based damage index method fo locating the damage with a spatial esolution on the ode of the gauge lengths of fibe optic sensos, and () the level FE model updating method locates and quantifies the damage with a spatial esolution on the ode of the sizes of the finite elements. Refeences [1] S.W. Doebling, C.R.Faa, M.B.Pime and D.W.Shevita. Damage identification and health monitoing of stuctual and mechanical systems fom changes in thei vibation chaacteistics: A liteatue eview. Los Alamos National Laboatoy Repot, [] Hoon Sohn, Chales R. Faa, Fancois M. Hemez, Devin D. Shunk, Daniel W. Stinemates, and Bett R. Nadle. A Review of Stuctual Health Monitoing Liteatue: Los Alamos National Laboatoy Repot, 003. [3] Aftab Mufti. Manual No. - Guidelines fo stuctual health monitoing. ISIS Canada, 001 [4] Z.S.Wu and S.Z. Li. Stuctual damage detection based on smat and distibuted sensing technologies. Poc. of the nd Intenational Confeence on Stuctual Health Monitoing of Intelligent Infastuctue (Keynote), Shenzhen, China, 005: [5] S.Z.Li and Z.S.Wu. Development of Distibuted Long-gage Fibe Optic Sensing System fo Stuctual Health Monitoing. Stuctual Health Monitoing [J]. 007, Vol.6: [6] S.Z.Li, Z.S.Wu and L.L.Zhou. Health monitoing of flexual steel stuctues based on distibuted fibe optic sensos. Stuctue and Infastuctue Engineeing [J]. 007 (Accepted) [7] Suzhen LI, Zhishen WU and Watanabe TAKUMI. A health monitoing stategy fo RC flexual stuctues based on distibuted long-gage fibe optic sensos. Jounal of

13 Applied Mechanics [J], JSCE. 007(Accepted) [8] Zhishen Wu and Bin Xu. Neual netwoks fo localized and decentalized identifications of lage-scale stuctues. Poc. of Neual Netwoks and Soft Computing 005 (Keynote), Cacow, Poland [9] B.Xu, S.Z.Li, Z.S.Wu and K.Yokoyama. Pefomance of neual netwoks based damage identification stategy fo noise polluted esponses. Intenational symposium on Netwok and Cente-based Reseach fo Smat Stuctues Technologies and Eathquake Engineeing (SE 04), Osaka, Japan, 004: [10] S.Z.Li and Z.S.Wu. Modal analysis on maco-stain measuements fom distibuted long-gage fibe optic sensos. Jounal of Intelligent Mateial Systems and Stuctues [J]. 007(Accepted) [11] S.Z.Li and Z.S.Wu. A Non-baseline Method fo Damage Locating and Quantifying in Beam-like Stuctue based on Dynamic Distibuted Stain Measuements. Compute-Aided Civil and Infastuctue Engineeing [J]. (In evise) [1] S.Z.Li and Z.S.Wu. A non-baseline algoithm fo damage locating in flexual stuctues using dynamic distibuted maco-stain esponses. Eathquake Engineeing and Stuctual Dynamics [J], 007, 36: pp [13] Z.S.Wu and S.Z.Li. Two-level damage detection stategy based on modal paametes fom distibuted dynamic maco-stain measuements. Jounal of Intelligent Mateial Systems and Stuctues [J], 007, Vol.18, No.7, pp