Multi-Scale Structural Health Monitoring Technologies

Transcription

1 6 th Intrnational Confrnc on Avancs in Exprintal Structural Enginring 11 th Intrnational Worshop on Avanc Sart Matrials an Sart Structurs Tchnology August 1-2, 2015, Univrsity of Illinois, Urbana-Chapaign, Unit Stats Multi-Scal Structural Halth Monitoring Tchnologis Y.L. Xu 1 an B.F. Spncr 2 1 Chair Profssor, Dpartnt of Civil an Environntal Enginring, Th Hong Kong Polytchnic Univrsity, Kowloon, Hong Kong. E-ail: cylxu@polyu.u.h. 2 Nathan M. Nw Mar Profssor, Dpartnt of Civil an Environntal Enginring, Univrsity of Illinois at Urbana- Chapaign, Illinois, USA. E-ail: bfs@uiuc.u. ABSTRACT This stuy prsnts ulti-scal structural halth onitoring (SHM) tchnologis for larg civil structurs. It involvs four ajor tass: (1) th ulti-scal finit lnt oling of a larg civil structur that can intgrat th global structural ol quipp with global snsors with th local structural tails install with local snsors; (2) th vlopnt of ulti-scal ol upating tho that uss ulti-scal upating paratrs an objctiv functions togthr with th Kriging tho; (3) th optial placnt of ulti-typ snsors that can intgrat global an local snsors, iniiz th rquir nubr of snsors, an incras th accuracy of aag tction via bst rspons rconstruction; an (4) th vlopnt of ulti-scal aag tction tho that can synthsiz th asurnt ata fro iffrnt snsors with iffrnt scals. Th accuracy of th propos tchnologis is valiat by conucting various xprintal stuis. KEYWORDS: Multi-scal, structural halth onitoring, larg civil structurs, aag tction 1. INTRODUCTION Many innovativ civil structurs hav bn construct aroun th worl. Ths structurs ar subjct to harsh nvironnts, which prsnt any challngs to profssionals for th functionality, safty an sustainability of th structurs. Th structural halth onitoring (SHM) tchnologis hav bn rgar as a cutting-g approach to proviing a bttr solution for th probls. Ovr th past two cas, significant ffort has bn icat to vibration-bas thos for aag tction in trs of asur global structural rsponss. Howvr, ost larg civil structurs ar coplx structurs, coprising tns of thousans of structural coponnts of iffrnt sizs an connct to on anothr in iffrnt ways. Local aag oftn os not significantly affct th global rsponss of a structur, aing global rspons-bas aag analysis inaccurat an sotis ipossibl. Morovr, th nubr of snsors in an SHM syst for a larg civil structur is always liit, an th snsors ay not irctly onitor th locations of structural fcts. Thrfor, th succssful application of aag tction thos to a larg civil structur is vry liit. This stuy prsnts ulti-scal structural halth onitoring (SHM) tchnologis for larg civil structurs. It involvs four ajor tass: (1) th ulti-scal finit lnt oling of a larg civil structur; (2) th vlopnt of ulti-scal ol upating tho; (3) th optial placnt of ulti-typ snsors; an (4) th vlopnt of ulti-scal aag tction tho. Th accuracy of th propos tchnologis is valiat by conucting various xprintal stuis. 2. MULTI-SCALE FINITE ELEMENT MODELING In practic, a larg civil structur is oftn ol via finit lnt (FE) tho using a cobination of ba, shll, soli, an othr lnts of siilar scal for th static an ynaic analyss at a global lvl. Strss concntration, crac initiation an propagation, fatigu, an fractur ar local phnona that ar oftn not rprsnt in th global structural ol. Howvr, any typs of fcts ar locally gnrat at th atrial points an sctional lvls an ay volv into a global structural aag an possibly caus structural failur. Thus, a ulti-scal FE oling of larg civil structurs has rcntly attract incrasing attntion in th fil of structural halth onitoring [1]. Multi-scal oling of a larg civil structur ainly ais to siulat an valuat siultanously its structural prforanc at both th acro- an icro-scals. This sction first

2 prsnts a nw ix-insional FE coupling tho that can achiv both isplacnt copatibility an strss quilibriu at th intrfac btwn th iffrnt lnt typs. Th nw ix-insional FE coupling tho is thn us to stablish th ulti-scal FE ol of a transission towr Intrfac Coupling of Mix-Dinsional Elnts Taing th intrfac coupling of ba-to-soli lnts as an xapl, th isplacnt constraint can b stablish in th sns that th isplacnt of ba at th intrfac quals to th gnraliz isplacnt of soli at th intrfac, which can b xprss as cu B, usub Cu S 0 (2.1) whr u B an u S ar th noal isplacnt vctor of ba an soli, rspctivly, at th intrfac; C is th cofficint atrix of th isplacnt constraint quation. Th tr of CuS can b sn as th gnraliz isplacnts of th soli, atching with th ba isplacnts u B at th intrfac an obtain by wighting th cofficint atrix C ovr th soli isplacnt vctor us at th intrfac. In consiration that th su of virtual wor on by th corrsponing forcs at th intrfac of th two typs of lnts shall b zro, th constraint quation of noal forcs at th intrfac can b xprss as T FS C F B (2.2) whr F B an F S ar th noal forc vctor of ba an soli, rspctivly. It is intrsting to s that th cofficint atrix C T of th forc constraint quation is th transpos of th cofficint atrix C T of th isplacnt constraint quation. Th cofficint atrix of th forc constraint quation can b rgar as a istribution atrix to istribut th forcs or ont at th no of th ba to th nos of th soli at th intrfac. Th satisfaction of both Eq. (2.1) an Eq. (2.2) can achiv both isplacnt copatibility an strss quilibriu btwn th iffrnt lnt typs. Furthror, Eq. (2.2) inicats that th istribution cofficints in th forc istribution atrix ar th corrsponing noal forcs of th soli at th intrfac unr unit forc or ont. Hnc, th cofficint atrix of th forc constraint quation actually rfrs to th noal forcs along th cross-sction of th soli unr unit forc or ont. Bas on this principl, a nw nurical tho copatibl with corcial FE cos has bn vlop to figur out th cofficint atrix of th forc constraint quation. Onc it is obtain, th cofficint atrix of th isplacnt constraint quation can b asily foun, an both isplacnt copatibility an strss quilibriu conitions at th intrfac ar satisfi. Local joint (a) global towr ol (b) local joint 2.2. A Physical Mol of a Transission Towr Figur 2.1 Physical ol of a transission towr In orr to vrify th accuracy of ulti-scal oling an analysis, a physical ol of a transission towr structur was built (s Figur 2.1). Th towr is assbl fro 23 typs of angl brs, which ar

3 connct to ach othr at joint plats with bolts. Th angl brs an gusst plats wr tailor-a in a factory by using th stainlss stl plats. Th coplt towr ol ha 930 angl brs, 402 gusst plats an 3649 bolts. Th static tsts wr carri out on th physical ol of th transission towr to obtain th strain an isplacnt rsponss of th towr unr a concntrat loa. Th har tsts wr carri out on th physical ol of th transission towr to intify th natural frquncis an oal shaps of th towr. Th tst ata will b thn us for valiating th ulti-scal oling an analysis rsults Multi-Scal Moling of th Transission Towr For a transission towr, thr ar any coplx probls to al with in th procss of ulti-scal oling, such as th intrfac coupling of ix-insional lnts an th contact probl btwn bolts an plats. It is thrfor or convnint to buil th ulti-scal ol of th transission towr using corcial FE softwar. Th FE softwar ANSYS is us in this stuy togthr with th slf-writtn supplntal progras for ulti-scal oling an analysis of th transission towr structur. Gusst plat (b) local joint Blot Angl br (c) bolt connction (a) global towr ol Figur 2.2 Multi-scal ol of a transission towr For th sa of a clar onstration, only on typical an ost iportant towr joint btwn th cran ar an th towr boy is slct to construct a tail local FE joint ol (s Figur 2.2b). Th slct joint consists of 9 angl brs of a shortn lngth, 3 gusst plats an 40 bolts. In orr to accuratly siulat th bolt connction, all th coponnts of th joint ar ol using soli lnts. Consquntly, th 20-no SOLID95 lnts of highr orr, which can siulat irrgular shaps with no loss in accuracy, ar us to ol angl brs, gusst plat an bolts of th slct joint. Apart fro this joint, all othr brs of th towr ar ol using ba lnts an all othr joints ar ol as rigi joints. Th coplt ulti-scal ol of th transission towr is shown in Figur 2.2a togthr with th local joint ol an th bolt connction shown in Figur 2.2b an Figur 2.2c rspctivly. It is not that thr is an intrfac for ach of 9 angl brs us in th joint btwn th global towr ol an th local joint ol. Th intrfac of th angl br btwn th soli an ba lnts is coupl by using th propos intrfac coupling tho. Anothr coplx probl in th local oling of th joint is th intraction btwn iffrnt coponnts for bolt connction, such as th contact btwn th bolt an th angl br, th contact btwn th bolt an th gusst plat, an th contact btwn th angl br an th gusst plat. Ths intractions ar achiv by using th contact lnts TARGE170 an CONTA174 of surfac-to-surfac typ, which avoi on lnt to pntrat into anothr. Furthror, ths contact lnts can siulat friction forcs btwn th two surfacs accoring to th Mohr Coulob law. 3. MULTI-SCALE MODEL UPDATING Although thr is lss uncrtainty in th ulti-scal ol than in th convntional FE ol, ulti-scal ol upating shall b prfor to nsur th quality of th ulti-scal ol of th transission towr at both acro an icro lvls. A ulti-scal ol upating tho using th ulti-objctiv optiization an Kriging tho is thrfor prsnt in this sction.

4 3.1. Paratrs an Objctiv Functions of Multi-Scal Mol Upating In FE ol upating, a st of y paratrs of th structur is upat by ans of iniizing th objctivs for by th rsiuals btwn th xprintal an FE analytical rsults of ynaic charactristics an/or rsponss. Copar with convntional FE ol upating, th ulti-scal ol upating rquirs th upating of both global an local ols siultanously. Thus, th upating paratrs ar slct fro both global an local ols. In this stuy, th global paratrs of th structur rfr to th lastic ouli of angl brs, th nsitis of angl brs, an th lup asss at th rigi joints. Th local paratrs rfr to th lastic ouli of gusst plats an bolts an th nsitis of gusst plats an bolts of th slct local joint. Accoringly, th structural rsponss us to calculat th rsiuals ar classifi as ithr global rsponss or local rsponss. In this stuy, th ynaic charactristics an th static rsponss of isplacnt an strain fro th global ol ar rgar as global charactristics or global rsponss whil th strain rsponss of th slct local joint ar tan as local rsponss. Multi-objctiv optiization algorith is vlop to al with th iniization of a vctor of objctiv functions subjct to a nubr of constraints or bouns. A ulti-objctiv optiization probl (MOP) is forulat as follows: iniiz J(θ) { J1(θ), J2(θ),..., Jq(θ)} (3.1) subjct to θl θθu whr θ is th vctor of upating paratrs; θ l an θ u ar th lowr an uppr bouns of θ; an J(θ) is a vctor of objctiv functions. It shoul b not that th optiality of MOP is not obvious bcaus a solution θ that siultanously iniizs all sub-objctivs os not gnrally xist. Insta, th Parto optiality is us to charactriz th objctivs. Th Parto optiality is a solution in which it is ipossibl to a any on objctiv bttr off without aing at last on objctiv wors off. Hr, th prfrr FE ol is slct by using th rsiual of ach Parto optial solution. Th solution with th iniu rsiual is slct as th prfrr FE ol with th upat paratrs. In this stuy, non-oinat sorting gntic algorith-ii (NSGA-II) is ploy for th iplntation of ulti-objctiv optiization to fin th Parto optial solution. In th algorith NSGA-II, th objctiv functions ar calculat for vry itration procss. Thrfor, th ulti-scal analysis of th structur is rquir to b carri out for ach itration procss, which ns hug coputation ti. To ruc th coputation ffort of th ol upating, th Kriging ta-ol is built an us to rplac th ulti-scal analysis in th itrativ optiization procss. In th Kriging ta-ol, th unnown functions ar th rsiuals of isplacnts, strains, natural frquncis an MAC. Th variabls ar upating paratrs, such as lastic oulus an nsity Multi-Scal Mol Upating of th Transission Towr Bas on th tst typs an rsults of th transission towr, th ulti-objctiv optiization ol is stablish for ulti-scal ol upating, which consists of objctiv functions, constraints an upating paratrs. Firstly, th 31 rsiuals of isplacnts, strains, natural frquncis an MACs ar calculat. Th 3 objctiv functions ar fin by ths rsiuals as follows: frquncy MAC i i i1 i1 3 6 isplacnt strain i i i1 i1 10 strain Ri i7 J (θ) R R J (θ) R R J (θ) whr J 1 ( x) an J 2 ( x) ar th global objctiv functions; an J ( ) 3 of ffctiv upating paratrs is a crucial stp in ol upating. It is ipractical to associat on upating paratr with ach lnt. Hr, on ol paratr is us for all th angl brs with th sa thicnss. Th snsitivitis ar thn us for th slction of paratrs, in which paratrs with lowr snsitivity ar liinat. As a rsult, a total of 13 upating paratrs ar slct. Th slct upating paratrs rfr to 7 lastic ouli, 4 nsitis an 2 lup asss. (3.2) x is th local objctiv function. Th slction Th upating rsults show that th axiu chang in all th upating paratrs is 16% of th quivalnt oulus of lasticity of th gusst plats. This is bcaus th strain rsponss of th gusst plats prict by th initial ol hav th largst rror copar with th tst rsults. Furthror, thr is only on upating paratr with a chang or than 10% aong th svn upating paratrs of lastic oulus, but thr ar four upating paratrs with a chang or than 10% aong th six upating paratrs of ass (incluing

5 nsitis an lup asss). This is bcaus th asss of th gusst plats an bolts ar about 15.6% of th total ass of th transission towr but it is ifficult to accuratly stiat th asss of th gusst plats an bolts. Both th initial an upat ulti-scal FE ols of th transission towr ar us to calculat th strain an isplacnt rsponss of th towr unr th concntrat loa. Th rsults fro th initial an upat ulti-scal ol ar thn copar with thos fro th static tsts. Th coparison rsults of th isplacnt rsponss show that th rsults obtain fro th upat ulti-scal ol ar closr to th tst rsults copar with thos fro th initial ol. Th coparison rsults of strain rsponss anifst that th strain rsponss of th ain angl brs of th local joint calculat fro th upat ulti-scal ol ar or accurat than thos fro th initial ol. Th axiu rrors of strains fro th initial an upat ulti-scal ols ar 30.37% an 9.77%, rspctivly, copar with th tst rsults. Th oal analysis is also carri out using th initial an upat ulti-scal ols of th transission towr. Th natural frquncis ar obtain an copar with th tst rsults. Th axiu rrors using th upat ulti-scal ol occurs at th sixth natural frquncy with a rlativ rror of 5.41%. Th axiu rror of th frquncis of th initial ol is 6.98% for th thir o of vibration. 4. MULTI-TYPE SENSOR PLACEMENT This sction invstigats a practical an challnging probl on how to plac ulti-typ snsors with th ai of bst rconstruction of ulti-scal rsponss at y locations. Givn that strain asurnt snsors ar usually us to rcor local rsponss, whras isplacnt an acclration rsponss ar appli to obtain global rsponss such as natural frquncis an o shaps, th thr typs of snsors coonly us in SHM, naly, acclrotrs, strain gaugs an isplacnt snsors, ar consir. Th locations of th ulti-typ snsor syst ar optiiz siultanously, an th asurnts fro th thr typs of snsors ar intgrat to rconstruct th structural rsponss of th structur at y locations with th Kalan filtr algorith. Th postriori rror covarianc is slct as a prforanc asur of rconstruction accuracy in th optiization [Error! Rfrnc sourc not foun.]. A siply-support ovrhanging stl ba is analyz as a cas stuy Frawor Th oally ruc orr ol of a structur with a proportional aping can b scrib by th following ti-invariant continuous stat spac quation in oal coorinat as x t = Acx t +Bcu() t (4.1) y t =Ccx t +Dcu() t By incluing th oling rror an asurnt nois, th continuous-ti stat spac ol in Eq. (4.1) can b transfrr into a iscrt-ti stat spac ol as x A x B u w y Cx Du v 1 2r whr x xt is th iscrt-ti stat vctor with t bing th sapling intrval; w ~ N 0, Q an v ~ N 0, R rprsnt th inpnnt, whit Gaussian oling rror an asurnt nois vctors, rspctivly. Th Kalan filtr givs an unbias an rcursiv algorith to optially stiat th unnown stat vctor of a linar ynaic syst [3] as: in which y nots th snsor asurnts; DOFs; an ˆ (4.2) xˆ A K C x B K D u G y D u (4.3) C an G is th Kalan gain. Th rconstruct rsponss at th y locations ar thn D ar copos of th o shaps with asur y ˆ Cx Du (4.4) C an D ar copos of oal shaps corrsponing to DOFs of th y location, whr no snsors ar install. Th accuracy of th rconstruct rsponss can b asur by th rconstruction rror δ as ˆ ˆ δ Cx Du Cx Du C x x (4.5) Th rspons rconstruction rror covarianc atrix is

6 T x T E Δ δ δ CP C (4.6) whr P x is th postriori stat rror covarianc of stat vctor at a ti stp. Th nubr an location of snsors ar optially sign by slcting th propr output atrix C an transission atrix D to iniiz th trac of stabl rconstruction rror covarianc atrix. Notably, th output influnc atrix C or C tns to b highly ill-conition bcaus th strain, th isplacnt an th acclration hav significantly iffrnt orrs of agnitu. Thus, th rconstruction rrors ar noraliz as - 1/ 2-1/ 2 ˆ ˆ δ R δ R C x x C x x (4.7) whr R is covarianc atrix of iffrnt typ asurnt nois. Th objctiv an constraint functions of th snsor location slction can b xprss as 4.2. Cas Stuy 2 T avg trac CPC N in in ( ) (4.8) A siply-support ovrhanging stl ba is ol as a two-insional Eulr-Brnoulli ba, constrain by a hing support an a rollr support (s Figur 4.1). Th ol consists of 40 lnts an 41 nos with a total of 123 DOFs. Th ffct of th xcitr on th ba is ol by a ass lnt an a spring lnt in th FE ol. Th first svn frquncis ar 6.03, 8.42, 17.73, 41.60, 64.42, 71.75, an Hz. Figur 4.1 FE ol of siply-support ovrhanging ba (unit: ) All th lnt strains, noal vrtical isplacnts, an acclrations, xcpt for th locations at supports, ar consir as th y rsponss to b rconstruct. Thy ar also rgar as initial caniat locations for snsors. Thus, totally 118 snsor locations ar slct as th initial caniats, incluing 40 for strain gaugs, 39 for isplacnt transucrs, an 39 for acclrotrs. Th strain gaugs ar assu to b attach on th uppr fac at th cntr of ach lnt; isplacnt transucrs an acclrotrs ar install vrtically on th structur. A rano forc with frquncy ranging fro 0.5 Hz to 100 Hz is appli to no 18 to gnrat structural vibration. Th first svn os ar slct to trin th nubr an optial locations of th ulti-typ snsors an rconstruct th ulti-scal rsponss with th propos tho. Th stanar viations of th asurnt nois for th strain gaug, isplacnt transucr, an acclrotr ar assu as 0.201, 0.01, an /s2, rspctivly. Figur 4.2 Variation of rconstruction rrors with nubr of snsors Figur 4.2 shows variation of rconstruction rrors with nubr of snsors. With th cras in th snsor nubr, th rrors incras. By slcting an allowabl rspons rconstruction rror, th typ, nubr an optial location of th snsors can b trin. In this cas stuy, 11 snsor locations ar slct, incluing fiv locations for strain gaugs, two for isplacnt transucrs, an four for acclrotrs, as shown in Figur 4.3.

7 Displacnt transucrs Strain gaugs Acclrotrs Figur 4.3 Snsor locations on th siply-support ovrhanging ba Furthr stuis clarly inicat that th htrognous fusion of ata fro ulti-typ snsors provis a or tail an accurat rconstruction of ulti-scal structural rsponss, which can provi coprhnsiv inforation for SHM of larg civil structurs with liit nubr of snsors. Th xprintal wor carri out on th sa ba also confirs th thortical rsults [2]. 5. MULTI-SCALE DAMAGE DETECTION This sction provis a ulti-scal aag tction tho in conjunction with rspons rconstruction. Raial-basis-function (RBF) ntwor is aopt to stiat th strain an isplacnt o shaps of th structur at th unasur locations bas on th inforation asur by th snsors. Th natural frquncis an o shaps givn by th RBF ntwor ar thn us for th rspons rconstruction. Th iffrncs in th rconstruct rsponss btwn th unaag an aag structur ar finally us to intify th aag location an xtnt. A siply-support ovrhanging stl ba is analyz to onstrat th supriority of th propos aag tction tho RBF Ntwor for Rspons Rconstruction of Daag Structur It can b prov that RBF ntwor is capabl of proviing arbitrarily goo approxiation to any prscrib function using only a finit nubr of paratrs [4]. Th output of th ntwor is a function of th input vctor an it is givn by N j i i i1 f x w x c (5.1) whr N is th nubr of nurons in th hin layr; c i is th cntr vctor for nuron i; wi is th wight of nuron i in th linar output nuron; an is na as th raial basis function that pns only on th istanc fro a cntr vctor an it is raially sytric about that vctor. Th input of th ntwor is th frquncis an o shaps of th aag structur at th snsor locations, which can b xtract by xprintal ol analysis (EMA) fro th asur ata. Ths ata ar thn us to train th BRF ntwor to stiat th strain an isplacnt o shaps of th structur at th unasur locations. Th rspons rconstruction tho prsnt in Sction 4 is finally us to stiat th rsponss of th structur at th unasur locations. Th flow chart of rspons rconstruction of th aag structur is shown in Fig y, C, D sys A, B, C, D ˆq t y Figur 5.1 Flow chart of rspons rconstruction of aag structur 5.2. Rspons Snsitivity-Bas FE Mol Upating an Daag Dtction Sinc ynaic rspons is a nonlinar function of aag paratr θ, an itrativ procur using a graint-bas optiization can b ploy to obtain th aag paratr as 1 S θ Y (5.2) S Y θ θ ; whr S Sθ Yθ θ is th snsitivity atrix for th -th itration with Y Y Ya θ is th rspons rsiuals btwn th aag an unaag structur; an ij i j θ l 1 l θ is th cuulativ aag paratr in all th -th itrations. S an Y ar assbl by stacing th coluns of snsitivity squncs an rspons iscrpancy squncs, rspctivly. A stratgy of spars rgularization is us to fin th solution of Eq.(5.2) sinc aag usually occurs at vry fw coponnts or locations of a structur.

8 5.3. Cas Stuy Th siply-support ovrhanging stl ba iscuss in th last sction is us as a cas stuy. A broaban stochastic forc with a frquncy banwith ranging fro 2 Hz to 82 Hz an a stanar viation of 30 N is appli on no 18 vrtically. Th first two oal aping ratios ar st as Ti stp is 1/500s an sapl uration is 12s. Nois corruption is siulat by aing norally istribut rano nois to th 2 nois-fr rspons. Th nois aplitu is st as 0.201με, 0.01 an 0.04 s for strain, isplacnt an acclration, rspctivly, accoring to th laboratory asurnt ata. Th signal-nois-ratio (SNR) is approxiatly 2%~3%. Th aag is siulat as th ruction of lastic oulus of th lnt. A cas of 12% ruction of lastic oulus of lnt 7 an 23% ruction of lnt 23 is ploy hr to rprsnt a ulti-aag scnario to invstigat th ffctivnss of th propos ulti-scal aag tction tho with an without rspons N u rconstruction. Daag can b ol as K K K 1 0 whil inrtial proprtis ar assu unchang bfor an aftr aag. i i i i1 Daag Paratr Dtct valu Prst valu Daag Paratr Dtct valu Prst valu Elnt Nubr (a) with rspons rconstruction Elnt Nubr (b) without rspons rconstruction Figur 5.2 Daag intification rsult Th final aag intification rsults with rspons rconstruction ar shown in Figur 5.2. For th sa of coparison, th rsults of aag intification without rspons rconstruction, naly, only th rsponss at 11 snsors ar us, is also prsnt in th figur. It can b obsrv that without rspons rconstruction, although th aag on lnt 7 is alost corrctly intifi, th aag on 23 is falsly locat at th ajacnt lnt 24. Bsis, thr ar rarabl positiv-rrors in lnt 21 an lnt 25. Th rsults inicat that th propos tho has crtain supriority ovr th iiat utilization of rsponss rcor by liit snsors. 6. CONCLUSIONS Th ulti-scal structural halth onitoring (SHM) tchnologis for larg civil structurs hav bn prsnt in this papr. Th accuracy of th propos tchnologis has bn valiat by conucting various xprintal stuis. Th finings fro this stuy avanc th xisting SHM tchnologis, allow possibl aag tction of larg civil structurs, an nhanc our ability to nsur th functionality an safty of structurs. AKCNOWLEDGEMENTS Th authors wish to acnowlg th financial supports fro Rsarch Grant Council of Hong Kong (PolyU 5289/12E) an th hlps fro th PhD stunts of th first author in prparing this papr. REFERENCES 1. Wang F.Y., Xu Y.L., Qu. W.L. (2014). Mix-insional finit lnt coupling for structural ulti-scal siulation. Finit Elnts in Analysis & Dsign, 92, Zhu S., Zhang X.H., Xu Y.L. an Zhan S. (2013). Multi-typ snsor placnt for structural halth onitoring. Avancs in Structural Enginring, 16:10, Kalan R. E. (1960). A Nw Approach to Linar Filtring an Priction Probls, Transaction of th ASME Journal of Basic Enginring, 82, Par J., Sanbrg I. W. (1991). Univrsal approxiation using raial-basis-function ntwors. Nural Coputation. 3: 2,