smart technologies for safety engineering

50 Smart Technologies for Safety Engineering
(a)
Figure 3.10 Experimental stand for a three-dimensional truss structure: (a) general view, (b) piezosensor
problem becomes underdetermined. Therefore the search zone needs to be confined to as
many members as there are accurate measurements collected. This means that the limit is one
eight-element segment of the truss structure.
A replacement of two elements in the selected segment has been investigated as a modification
scenario. Two horizontal steel members (see Figure 3.12) were replaced with other ones
of significantly increased cross-section μ46 = μ48 = 2.04 (A46 = A48 = 1.344 cm 2 ). Results
of the inverse analysis for the experimental data recorded for this modification scenario are
depicted in Figure 3.13. It is apparent that the location of the introduced modifications has
been found correctly. The intensity in one member is very close to the assumed change (4 %
difference). The deviation in the other member reaches 20 %. This result can be improved by
measuring strains, which are less sensitive to noise. Also, a more sophisticated optimization
algorithm should lead to a better quality of identification in a shorter time.
(a)
..
u
i
(b)
..
u
i
1.5
1
0.5
0
1
0.5
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
node no.
1 4 6 11 17
node no.
18 19 20
(b)
measured
numerical
Figure 3.11 Matching the model to experiment: (a) initial 22 measurements, (b) selected 8 measurements