Identification of the dynamic characteristics of nonlinear structures

DEGREES OF 
Fig.7.5 Relative Modeshape Error of Mode 1 (case 2)
Fig.7.6 Relative Modeshape Error of Mode 2 (case 2)

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and Limitations of Analytical Model Improvement
217
DEDREES OF 
Fig.7.7 Relative Modeshape Error of 
3 (case 2)
 
.
I
11
DEDREES OF 
Fig.7.8 Relative Modeshape Error of Mode 4 (case 2)
DEDREES OF 
Fig.7.9 Relative Modeshape Error of Mode 5 (case 2)

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and Limitations of Analytical Model Improvement
218
These expanded modes are then used to find the localised modelling errors based on the
location methods discussed in Chapter 5. All 5 modes are used respectively and the
location results are shown in 
(these are not strictly stiffness modelling
errors 
but are 
as 
explained in Chapter 5). When compared with the
stiffness error matrix of Fig.7.4, it can be seen that the location is quite successful since
for every mode, all the areas where the major modelling errors are placed, are clearly
located. However, it is difficult to identify the different amplitudes of these errors by
looking at these location results even if, in fact, the errors are considerably different in
amplitudes (figure 7.4). This adds difficulties for the next-step updating.
Located Stiffness Errors Using Mode 1 (case 2)

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7
Possibilities and Limitations of Analytical Model Improvement
219
X
Y
X
Located Stiffness Errors Using Mode 2 (case 2)
Located Stiffness Errors Using Mode 3 (case 2)

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Possibilities and Limitations of Analytical Model Improvement
220
Located Stiffness Errors Using Mode 4 (case 2)
Located Stiffness Errors Using Mode 5 (case 2)

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Possibilities and Limitations of 
Model