Continuous ambient vibration measurements: experimental setup and first results on an arch dam Acquiring data over several years with different tidal ranges will allow us to refine the estimation of the


hydrostatic effect calculated from these initial data. Another observation (shown in Figure 9) is made regarding the relationship between the variation of the


frequency of the natural modes and the external temperature. Indeed, during the summer period, the two parameters seem to be in phase, with an increase in frequency corresponding to an increase in the external temperature averaged over 5 days. However, during the winter period, this relationship appears to be out of phase. There is no explanation for this observation at this stage, and data acquisition over several years will allow, once again, to verify this observation.


Figure 9. Opposition of the frequency variation compared to temperature during winter time


4. Data Analyses with Multi-Sensor Approach Mutli-sensor analyses using in-house software.


4.1. Description of Data Analytics for an operational modal analysis Data Analytics is an in-house software developed by EDF. It is a tool dedicated to vibration analysis of a structure using a multi-sensor / multi-reference approach. For this case, the operational modal analysis (OMA) tool will be used for the present study. The OMA approach implemented by Data_Analytics largely builds upon the PolyMax algorithm: PolyMax


is a frequency-domain modal parameter estimation algorithm that employs a right matrix-fraction model approach to derive clear stabilization diagrams, leading to robust pole estimations. A pole-residue model is then used to estimate the mode shapes[8]


. PolyMax is complemented by a series of methods designed to enhance the reliability and robustness of OMA. These include:


• Pole Selection via Stabilization Diagram (used to evaluate modes frequency and damping in muti- sensor configuration): The choice of the constraint leading to pole estimation from the right fraction-


Vol XXXIII Issue 3 | Dam Engineering | 147


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