PSI - Issue 64

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000–000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 64 (2024) 669–676

SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Cointegration technique to account for environmental variability in a concrete dam Marco Pirrò a *, Sérgio Pereira b , Carmelo Gentile a , Filipe Magalhães b , Álvaro Cunha b a DABC, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy b Construct-ViBest, Faculty of Engineering (FEUP), University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal Within Operational Modal Analysis (OMA) and Structural Health Monitoring (SHM) frameworks, novelty analysis aims to detect structural anomalies by inspecting the time evolution of the modal parameters of a structure subjected to ambient (unknown) excitations. However, real structures are subjected not only to structural anomalies, but also to environmental and operational variability (EOV), so it is necessary to remove EOV effects from damage-sensitive features. The paper presents an application of Cointegration technique to account for EOV on natural frequencies: given a set of non-stationary time-series, Cointegration builds a stationary linear combination of them, the cointegration residual , which is purged from the common trends mainly associated with EOV. The coefficients of the linear combination are determined by a maximum-likelihood multivariate technique, employing the natural frequencies within a training period, in which the structure is supposed to be in healthy conditions, under normal EOV. Once trained, the computed coefficients are used to test natural frequencies from unknown scenarios. The obtained cointegration residual will maintain its stationarity, as long as the structure behaves in normal conditions. Compared to traditional techniques, the Cointegration relies on more general operations, such as the construction of a linear combination given a set of modal parameters. The application of the presented procedure is exemplified with data measured in Baixo Sabor dam (Portugal) during the first two years of monitoring, which include the first filling of the reservoir. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers Abstract

Peer-review under responsibility of SMAR 2024 Organizers Keywords: SHM; OMA; Environmental effects; Cointegration; dam.

* Corresponding author. Tel.: +39 02 2399 4242. E-mail address: marco.pirro@polimi.it

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers 10.1016/j.prostr.2024.09.325