Introduction1.1 Operational Modal Analysis: A New Discipline?The use of experimental tests to gain knowledge about the dynamic response of civil structures is a well-established practice. In particular, the experimental identification of the modal parameters can be dated back to the middle of the Twentieth Century (Ewins 2000). Assuming that the dynamic behavior of the structure can be expressed as a combination of modes, each one characterized by a set of parameters (natural frequency, damping ratio, mode shape) whose values depend on geometry, material properties, and boundary conditions, Experimental Modal Analysis (EMA) identifies those parameters from measurements of the applied force and the vibration response.In the last decades the principles of system identification and the experimental estimation of the modal parameters have provided innovative tools for the under¬standing and control of vibrations, the optimization of design, and the assessment of performance and health state of structures. In fact, even if the Finite Element (FE) method and the fast progress in computing technologies have made excellent analysis tools available to the technical community, the development of new high- performance materials and the increasing complexity of structures have required powerful tools to support and validate the numerical analyses. In this context the experimental identification of the modal properties definitely supports the engineers to get more physical insight about the dynamic behavior of the structure and to discriminate between the errors due to discretization and those due to simplified or even wrong modeling assumptions. Moreover, since the vibration response originates from the modes, which are inherent properties of the structure, forces exciting the structure at resonant frequencies yield large vibration responses that can result in discomfort or even damage. Regular identification of modal para¬meters and analysis of their variation can support the assessment of structural performance and integrity.Since the origin of EMA, testing equipment and data processing algorithms have significantly evolved. EMA is currently a well-established field, based on a soundC. Rainieri and G. Fabbrocino, Operational Modal Analysis of Civil Engineering 1 Structures: An Introduction and Guide for Applications, DOI 10.1007/978-1-4939-0767-0_1, # Springer Science+Business Media New York 2014
Introduction<br>1.1 Operational Modal Analysis: A New Discipline?<br>The use of experimental tests to gain knowledge about the dynamic response of civil structures is a well-established practice. In particular, the experimental identification of the modal parameters can be dated back to the middle of the Twentieth Century (Ewins 2000). Assuming that the dynamic behavior of the structure can be expressed as a combination of modes, each one characterized by a set of parameters (natural frequency, damping ratio, mode shape) whose values depend on geometry, material properties, and boundary conditions, Experimental Modal Analysis (EMA) identifies those parameters from measurements of the applied force and the vibration response.<br>In the last decades the principles of system identification and the experimental estimation of the modal parameters have provided innovative tools for the under¬standing and control of vibrations, the optimization of design, and the assessment of performance and health state of structures. In fact, even if the Finite Element (FE) method and the fast progress in computing technologies have made excellent analysis tools available to the technical community, the development of new high- performance materials and the increasing complexity of structures have required powerful tools to support and validate the numerical analyses. In this context the experimental identification of the modal properties definitely supports the engineers to get more physical insight about the dynamic behavior of the structure and to discriminate between the errors due to discretization and those due to simplified or even wrong modeling assumptions. Moreover, since the vibration response originates from the modes, which are inherent properties of the structure, forces exciting the structure at resonant frequencies yield large vibration responses that can result in discomfort or even damage. Regular identification of modal para¬meters and analysis of their variation can support the assessment of structural performance and integrity.<br>Since the origin of EMA, testing equipment and data processing algorithms have significantly evolved. EMA is currently a well-established field, based on a sound<br>C. Rainieri and G. Fabbrocino, Operational Modal Analysis of Civil Engineering 1 Structures: An Introduction and Guide for Applications, DOI 10.1007/978-1-4939-0767-0_1, # Springer Science+Business Media New York 2014
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