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Author:Huhtala, Antti
Title:Locating damage in a structure using measurements of vibrational parameters
Rakenteen vaurion paikallistaminen värähtelymittauksista
Publication type:Master's thesis
Publication year:2009
Pages:61      Language:   eng
Department/School:Informaatio- ja luonnontieteiden tiedekunta
Main subject:Mekaniikka   (Mat-5)
Supervisor:Stenberg, Rolf
Instructor:Bossuyt, Sven
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark T80     | Archive
Keywords:structural health monitoring
inverse problem
Bayesian inference
damage identication
nite element method
dynamics of structures
modal damping
rakenteiden kunnonvalvonta
käänteisongelma
Bayesiläinen tilastotiede
vaurion tunnistaminen
elementtimenetelmä
rakenteiden dynamiikka
moodikohtainen vaimennus
Abstract (eng): In a structural health monitoring system, a structure's behavior is monitored using several sensors attached to it.
Information about the health of the structure is then deduced from the measured data.
Several methods for identifying structural damage based on the sensor measurements have been proposed in the literature.
These methods seek to identify at least one of the following properties of the damage: the presence of the damage, the magnitude of damage and/or the location of damage.

In this thesis, a method based on Bayesian inference is derived.
Using knowledge of the vibrational behavior of the structure, the proposed method can potentially identify all of the three presented properties of damage.
A statistical approach is taken as the measurements produced by the sensors always contain uncertainties in the form of measurement error.
Being able to take uncertainties directly into account is a benet of the proposed method compared to many methods presented in the literature.

The method proposed in this thesis is based on a discretized model of the structure, which is assumed to match the actual structure as accurately as possible.
In order to reach an accuracy high enough, the structure model can be updated using model updating schemes as presented in the literature.
In addition to a model of the structure, a model of the damage is also needed.
The damage model predicts how the properties of the structure change in an arbitrary damage state and also states how probable the damage state is.

To verify the method, it is first applied to identify damage in a cantilever beam simulated in a nite element modelling program.
Finally, it is used to identify damage in a real steel cantilever.
Abstract (fin): Rakenteiden kunnonvalvontajärjestelmässä rakenteen käyttäytymistä tarkkaillaan useiden siihen kiinnitettyjen anturien avulla.
Rakenteen käyttäytymisen perusteella lopulta pyritään saamaan tietoa rakenteen kunnosta.
Rakennevaurioiden selvittämiseen anturien antaman tiedon perusteella on kirjallisuudessa esitetty monenlaisia menetelmiä.
Nämä menetelmät pyrkivät tunnistamaan ainakin yhden seuraavista vaurion ominaisuuksista: vaurion läsnäolon, vaurion suuruuden ja/tai vaurion sijainnin.

Tässä työssä johdetaan Bayesiläistä tilastotiedettä käyttäen menetelmä, joka rakenteen värähtelykäyttäytymistä tarkkailemalla kykenee potentiaalisesti tunnistamaan kaikki kolme esitettyä vaurion ominaisuutta.
Tilastollista lähestymistapaa sovelletaan, koska anturien tuottamat mittaukset sisältävät aina epävarmuutta mittausvirheen muodossa.
Epävarmuuksien lähtökohtainen huomiointi on esitetyn menetelmän etu moniin kirjallisuudessa julkaistuihin menetelmiin nähden.

Esitetty menetelmä perustuu elementtimenetelmällä diskretoituun malliin rakenteesta, jonka oletetaan vastaavan todellista rakennetta mahdollisimman hyvällä tarkkuudella.
Riittävän tarkkuuden saavuttamiseksi malliin voidaan soveltaa kirjallisuudessa esitettyjä mallinpäivitysmenetelmiä.
Rakenteen mallin lisäksi menetelmää varten tarvitaan vauriomalli, joka ennustaa rakenteen ominaisuuksien muutoksen mielivaltaisessa vauriotilanteessa ja ottaa kantaa siihen miten todennäköinen tämä vauriotila on.

Menetelmän toimivuuden tarkistamiseksi sitä sovelletaan elementtimenetelmäohjelmistolla simuloidun ulokepalkin vaurion tunnistamiseen, ja lopulta todellisen teräksisen ulokepalkin vaurion tunnistamiseen.
ED:2010-01-20
INSSI record number: 38773
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