PSI - Issue 78

Eleonora Massarelli et al. / Procedia Structural Integrity 78 (2026) 317–324

322

Table 1: Summary of the modal parameters identified by the AOMA MATLAB code for the relevant modes in the instrumented spans in case study A (left) and B (right), with average and standard deviation values (St.Dev).

Case study A

Case study B

Mode 1 Mode 2a Mode 2b Mode 3

Mode 1a

Mode 1b

Mode 2a

Mode 2b

Mode 3 15.169

Span 1

f [Hz] 8.148 9.205

10.084 15.873

4.300

4.847

12.821 13.352

ξ [-]

0.016 0.019

0.021

0.010

0.027

0.045

0.015

0.012

0.021

Span 2

f [Hz] 8.117

4.301

4.799

12.829 13.349

15.104

9.181

10.112

16.020

ξ [-]

0.019 0.017

0.014

0.011

0.026

0.036

0.012

0.014

0.019

Span 3

f [Hz] 8.126 9.142

10.123

15.907

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

n.a. n.a.

ξ [-]

0.026 0.016

0.020

0.012

Average f [Hz] 8.130

9.176

10.106

15.933

4.300

4.823

12.825 13.351

15.136

ξ [-]

0.020 0.017

0.018 0.020 0.004

0.010 0.077 0.001

0.027

0.041

0.014

0.013

0.020

St.Dev.

f [Hz] 0.016 0.032

0.0005 0.034

0.006

0.002

0.046

ξ [-]

0.005 0.002

0.001

0.007

0.002

0.002

0.001

Figure 5: Identified mode shapes for one span for each structure with an indication of the measurement points in red, the top part refers to case study A [mode 1 (a), modes 2a (b), and 2b (c), and possibly a plate-like mode 3 (d)]; and for case study B in the bottom part [modes 1a (e) and 1b (f), modes 2a (g), and 2b (h), and mode 3 (i) of higher order]. 4.2. ARTeMIS benchmark results To validate the results, the same datasets were processed using ARTeMIS using the Stochastic Subspace Identification variant with Unweighted Principal Component (SSI-UPC) algorithm † . The signals relative to ambient vibrations used are those from the pre-processing phase described in Section 2.2, hence ensuring comparable results. Identical model order ranges and stabilisation parameters were used for consistency. The same double identifications were again observed, confirming that the phenomenon is almost certainly physically meaningful and not due to some technical issue in the identification algorithm developed in MATLAB. The results are reported in Table 2. This can be compared to the ones from the previous Table 1. In general, ARTeMIS produced slightly higher damping ratios compared to the Authors’ estimates, reflecting known

† https://www.svibs.com/resources/ARTeMIS_Modal_Help_v3/SSI_ssi.htm