Dynamic structural system identification using observability techniques
Estadístiques de LA Referencia / Recolecta
Inclou dades d'ús des de 2022
Cita com:
hdl:2117/103203
Correu electrònic de l'autorballester.ramirez.davidgmail.com
Realitzat a/ambUniversidad de Castilla-La Mancha
Tipus de documentProjecte Final de Màster Oficial
Data2016-06-23
Condicions d'accésAccés obert
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continguts d'aquesta obra estan subjectes a la llicència de Creative Commons
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Reconeixement 3.0 Espanya
Abstract
Structures are complex systems with several stages within their service life. Firstly,
engineers have to design the structure with some of the many available mathematical
and computational tools. In most cases, the designed structures are discretized within
finite elements method (FEM). The equations implemented in this method relate the
external actions (e.g. forces, accelerations, imposed displacements) with the output
response of the structure (e.g. nodal displacements) by means of the geometric and
mechanical parameters of the structural elements (e.g. beams' areas, inertias, Young's
Modulus), leading to large systems of equations. Generally, for a given structure in a
design stage, the structural parameters are assumed as known, allowing thus to
compute a direct solution for the structure.
Nevertheless, during the following stages of construction and operation, the structures
are subjected to different elements (e.g. humidity, temperature, chemical products) and
actions (construction errors, loads, earthquakes) that in most cases can be assumed as
random and unknown. These, may lead to a change in the value of the structural
parameters and turn them to be uncertain too. Thus, for the sake of security and
structural control, the actual uncertain parameters must be identified. In order to
identify them, many techniques are available. Particularly, this paper deals with an
inverse analysis called Structural System Identification (SSI). Within all the techniques
inside the SSI techniques, this paper is implementing the observability technique. This
technique is nailed to the null space theory for a given system of equations in order to
determine which of the unknowns can be assessed uniquely. Meaning that a unique
solution can be found for each of them. Also, in this paper, an algebraic matricial
methodology in order to allow the identification of the unknown parameters is
proposed. In order to do so, a set of experimental measurements taken from the
structure must be input into the method.
The observability technique has been implemented in many fields of engineering and
for many different equations. A special mention is deserved to the implementation of
this technique to the stiffness matrix method which observes the static parameters of a
given structure from static measurements of load test. In this thesis, the observability
technique is going to be applied on the eigenvalue equation and an algorithm is going
to be developed in order to carry out the computations. The dynamic character of the
method requires the inputs measurements to be the modal displacements and the
eigenfrequencies for the different natural modes of vibration. These data is assessed
through the implementation of modal experimental analysis over the structures which
computes the actual modal data. Finally, the method is applied within a symbolical
approach, obtaining for the first time in the literature the symbolic equations of the
identified parameters and their numerical errors for a dynamic approach.
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