Operational modal analysis (OMA) is a powerful tool in structural health monitoring (SHM), enabling the estimation of dynamic characteristics (natural frequencies, mode shapes, and damping ratios) of structures based on their vibration response under operational conditions. The performance of OMA techniques depends on specific structural characteristics and identification procedure selected. To this aim, a variety of OMA techniques, including enhanced frequency domain decomposition (EFDD), stochastic subspace identification (SSI-COV and SSI-DATA), PolyMAX, and Ibrahim time domain (ITD), are implemented in a new computationally efficient Python library, Modalyzer, developed and presented here for the first time to unify and streamline the application of OMA techniques to different structural contexts. Flexibility and robustness of Modalyzer are demonstrated by applications to three different case-study structures with different conditions and measurement systems, and results obtained by Modalyzer are compared to those obtained by independent calculations and methods for validation purposes. The results highlight strengths and limitations of each method in different structural scenarios, offering guidance on selecting the most suitable OMA technique for specific SHM applications. Moreover, Modalyzer demonstrates significant time efficiency compared to longer computational times of established tools like ARTeMIS Modal, and incorporates user-friendly features further facilitating its adoption within the SHM community.
AgdasDRiceJAMartinezJR, et al. (2016) Comparison of visual inspection and structural-health monitoring as bridge condition assessment methods. Journal of Performance of Constructed Facilities30(3): 04015049.
2.
AlaggioRAloisioAAntonacciE, et al. (2021) Two-years static and dynamic monitoring of the Santa Maria di Collemaggio basilica. Construction and Building Materials268: 121069.
3.
AllemangRJBrownDL (2022) Experimental modal analysis methods. In: Handbook of Experimental Structural Dynamics. Springer New York, 1–81.
4.
AloisioADi PasqualeAAlaggioR, et al. (2022) Assessment of seismic retrofitting interventions of a masonry palace using operational modal analysis. International Journal of Architectural Heritage16(5): 692–704.
5.
ARTeMIS (2015) Structural Vibration Solutions A/S, NOVI Science Park, Niels Jernes Vej 10, DK-9220. ARTeMIS modal application manual.
AvciOAbdeljaberOKiranyazS, et al. (2018) Wireless and real-time structural damage detection: a novel decentralized method for wireless sensor networks. Journal of Sound and Vibration424: 158–172.
8.
AvciOAbdeljaberOKiranyazS, et al. (2025) A new benchmark problem for structural damage detection: bolt loosening tests on a large-scale laboratory structure. In: Dynamics of Civil Structures. River Publishers, Vol. 2, 15–22.
9.
BrinckerRVenturaC (2015) Introduction to Operational Modal Analysis. John Wiley and Sons, Inc.
10.
BrinckerRZhangLAndersenP (2000) Modal identification from ambient responses using frequency domain decomposition. In: IMAC 18: Proceedings of the International modal analysis conference (IMAC), San Antonio, Texas, USA, 7-10 February 2000, Aalborg Universitet, 625–630.
11.
BrinckerRZhangLAndersenP (2001) Modal identification of output-only systems using frequency domain decomposition. Smart Materials and Structures10(3): 441–445.
12.
BrownjohnJMWMagalhaesFCaetanoE, et al. (2010) Ambient vibration re-testing and operational modal analysis of the humber bridge. Engineering Structures32(8): 2003–2018.
13.
CaubergheB (n.d.) Applied frequency-domain System Identification in the Field of Experimental and Operational Modal Analysis. Vrije Universiteit Brussel.
14.
Computer and Structures, Inc. (2023) SAP2000 Analysis Reference Manual. CSI Berkeley.
15.
DarbreGRde SmetCAMKraemerC (2000) Natural frequencies measured from ambient vibration response of the arch dam of mauvoisin. Earthquake Engineering & Structural Dynamics29(5): 577–586.
16.
De DomenicoDMazzeoMMessinaD, et al. (2025) Structural health assessment of concrete half-joint bridges: from load testing to FEM simulation accounting for material uncertainties. Structure and Infrastructure Engineering1–20. doi: 10.1080/15732479.2025.2468199.
17.
DiaoYLvJWangQ, et al. (2023) Structural damage identification based on variational mode decomposition–Hilbert transform and CNN. Journal of Civil Structural Health Monitoring13(6–7): 1415–1429.
18.
DoeblingSWFarrarCRPrimeMBShevitzDW (1996) Damage identification and health monitoring of structural and mechanical systems from changes in their vibration characteristics: a literature review. LA-13070-MS. LosNM: Alamos National Laboratory.
19.
EwinsDJ (2000) Modal Testing: Theory, Practice, and Application. Research Studies Press.
20.
FarrarCRJamesGHIII (1997) System identification from ambient vibration measurements on a bridge. Journal of Sound and Vibration205(1): 1–18.
21.
FarrarCRWordenK (2012) Structural Health Monitoring. Wiley.
22.
FigueiredoEParkGFigueirasJFarrarCWordenK (2009) Structural health monitoring algorithm comparisons using standard data sets (No. LA-14393). Los Alamos, NM (United States): Alamos National Laboratory (LANL).
23.
GattulliVChiaramonteL (2005) Condition assessment by visual inspection for a bridge management system. Computer-Aided Civil and Infrastructure Engineering20(2): 95–107.
24.
GentileCGallinoN (2008) Ambient vibration testing and structural evaluation of an historic suspension footbridge. Advances in Engineering Software39(4): 356–366.
25.
HansenJBBrinckerRLópez-AenlleM, et al. (2017) A new scenario-based approach to damage detection using operational modal parameter estimates. Mechanical Systems and Signal Processing94: 359–373.
26.
HermansLVan der AuweraerH (1999) Modal testing and analysis of structures under operational conditions: industrial applications. Mechanical Systems and Signal Processing13(2): 193–216.
27.
IbrahimSR (1977) Random decrement technique for modal identification of structures. Journal of Spacecraft and Rockets14(11): 696–700.
28.
IbrahimSR (1999) Fundamentals of time domain modal identification. In: Modal Analysis and Testing. Springer Netherlands, 241–250.
29.
IbrahimSRAsmussenJCBrinckerR (1996) Modal parameter identification from responses of general unknown random inputs. In: Proceedings of the 14th international modal analysis conference, Dearborn, 12 February 1996. Aalborg Universitet.
30.
JacobsenN-JAndersenPBrinckerR (2006) Using enhanced frequency domain decomposition as a robust technique to harmonic excitation in operational modal analysis. In: Proceedings of ISMA2006: international conference on noise & vibration engineering, Lueven, 18–20 september 2006, Katholieke Universiteit.
31.
JuangJ-N (1994) Applied System Identification. Prentice Hall.
32.
La MazzaDLongoMChiariottiP, et al. (2023) Nuove sfide per il monitoraggio strutturale di infrastrutture: analisi modale con architetture distribuite. new challenges for structural monitoring of infrastructures. Structural Magazine, 246, May-June 2023. doi: 10.12917/STRU246.13.
33.
LiJWenFPanY, et al. (2024) Experimental study on the damage identification of bridge expansion joints. Journal of Civil Structural Health Monitoring14(3): 575–590.
34.
LievenNEwinsD (1988) Spatial correlation of mode shapes: the coordinate modal assurance criterion (COMAC). In: Proceedings of the 6th international modal analysis conference (IMAC), Kissimmee, Florida, 1–4 February 1988, vol 1, pp. 690–695.
35.
LorenzoniFDe ContoNda PortoF, et al. (2019) Ambient and free-vibration tests to improve the quantification and estimation of modal parameters in existing bridges. Journal of Civil Structural Health Monitoring9(5): 617–637.
36.
MatsubaraMSaitoAKawamuraS (2021) Estimation of modal parameters by using the ratios of imaginary to real parts of frequency response functions. Archive of Applied Mechanics91(3): 1179–1191.
37.
MazzeoMDe DomenicoDQuarantaG, et al. (2023) Automatic modal identification of bridges based on free vibration response and variational mode decomposition technique. Engineering Structures280: 115665.
38.
MazzeoMDe DomenicoDQuarantaG, et al. (2024) An efficient automatic modal identification method based on free vibration response and enhanced empirical Fourier decomposition technique. Engineering Structures298: 117046.
39.
ModakSV (2023) Analytical and Experimental Modal Analysis. CRC Press.
40.
MohantyPRixenDJ (2004) A modified Ibrahim time domain algorithm for operational modal analysis including harmonic excitation. Journal of Sound and Vibration275(1–2): 375–390.
41.
NguyenDHAbdel WahabM (2023) Damage detection in slab structures based on two-dimensional curvature mode shape method and faster R-CNN. Advances in Engineering Software176: 103371.
42.
PascaDPAloisioARossoMM, et al. (2022) PyOMA and PyOMA_GUI: a python module and software for operational modal analysis. SoftwareX20: 101216.
43.
PascaDPMargoniDFRossoMMAloisioA (2024) PyOMA2: An open-source python software for operational modal analysis. In: Rainieri, C., Gentile, C., Aenlle López, M. (eds.). Proceedings of the 10th International Operational Modal Analysis Conference (IOMAC 2024). IOMAC 2024. Lecture Notes in Civil Engineering514: 423–434. doi: 10.1007/978-3-031-61421-7_42.
PeetersBDe roeckG (1999) Reference-based stochastic subspace identification for output-only modal analysis. Mechanical Systems and Signal Processing13(6): 855–878.
46.
PeetersBVan der AuweraerH (2005) PolyMax: a revolution in operational modal analysis. In: 1st International Operational modal analysis conference, Copenhagen, Denmark, January 2005, pp. 1–12.
47.
PeetersBVan der AuweraerHGuillaumeP, et al. (2004) The PolyMAX frequency‐domain method: a new standard for modal parameter estimation?Shock and Vibration11(3–4): 395–409.
48.
PeetersBVan der AuweraerHVanhollebekeF, et al. (2007) Operational modal analysis for estimating the dynamic properties of a stadium structure during a football game. Shock and Vibration14(4): 283–303.
49.
RafieiMHAdeliH (2017) A novel machine learning‐based algorithm to detect damage in high‐rise building structures. The Structural Design of Tall and Special Buildings26(18): e1400.
50.
RainieriCFabbrocinoG (2014) Operational Modal Analysis of Civil Engineering Structures. Springer New York.
51.
ReyndersE (2012) System identification methods for (operational) modal analysis: review and comparison. Archives of Computational Methods in Engineering19(1): 51–124.
52.
ReyndersEHoubrechtsJDe RoeckG (2012) Fully automated (operational) modal analysis. Mechanical Systems and Signal Processing29: 228–250.
53.
RossingT (2007) Modal analysis. In: Springer Handbook of Acoustics. Springer New York, 1127–1138.
54.
SchulzePCThompsonPDanowskyBP, et al. (2013) System identification and modal extraction from response data. In: AIAA atmospheric flight mechanics (AFM) conference, Reston, Virginia, 19 August 2013. American Institute of Aeronautics and Astronautics.
55.
SujathaC (2023) Basics of experimental modal analysis. In: Vibration, Acoustics and Strain Measurement. Springer International Publishing, 465–533.
56.
Van OverscheePDe MoorB (1993) Subspace algorithms for the stochastic identification problem. Automatica29(3): 649–660.
57.
Van OverscheePDe MoorB (1996) Subspace Identification for Linear Systems. Springer US.
58.
VerbovenPGuillaumePCaubergheB, et al. (2004) Frequency-domain generalized total least-squares identification for modal analysis. Journal of Sound and Vibration278(1–2): 21–38.
59.
ZanariniA (2019) Full field optical measurements in experimental modal analysis and model updating. Journal of Sound and Vibration442: 817–842.
