Fundamentals of dynamics and experimental and operational modal analysis of structures

Engineering Headquarters — Salita alla Rocca, 44, San Marino

The monitoring of existing civil structures and infrastructures is of great importance both for the assessment of damage following exceptional events, degradation phenomena, and static settlements and for the preparation of a maintenance plan. Alongside the more traditional static one, dynamic monitoring is gaining in recent years an ever-increasing interest both in the panorama of scientific research and in the professional field. The dynamic parameters, such as natural frequencies and vibration modes of a structure, constitute a snapshot of its current state and repeating the tests over time allows the identification of changes that cannot always be identified with static monitoring. The knowledge of the modal parameters also allows the calibration of finite element structural models that can be used both for the assessment of the seismic vulnerability of the structure and therefore for the design of any interventions, and for the identification of the causes that may have led to changes in the dynamic behavior, such as damage, degradation, changes in structural and non-structural components. Modal analysis is an identification approach of a system based on the determination of its main dynamic parameters: natural frequencies, damping and mode shapes. These parameters can be determined experimentally using two techniques called experimental and operational modal analysis. In the field of civil engineering, modal parameters are currently used for several purposes:

• Response estimation;
• Structural health monitoring;
• Damage identification;
• Refinement of FEM models (model updating).

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