Structure Dynamic Characterization Considering Non-Proportional Damping

Heydari, Shahram and Gholizad, Amin and Shakeri, Kazem (2016) Structure Dynamic Characterization Considering Non-Proportional Damping. Masters thesis, University of Mohaghegh Ardabili.

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Abstract

System identification method with the development of dynamic modal testing are one of the most useful tools for assessment of vibrating loads in the past few decades. so that the system cannot properly evaluate its dynamic behaviour without information and dynamic characteristics (natural frequency, damping ratio, etc.). In addition to the detailed behaviour of structures close to reality, knowing their health and free of any damage is not possible without understanding the dynamic properties of structures so these objectives will not be available except by identifying and estimating the structural dynamics parameters. A structure during construction, and during its operation can be under different vibration with different intensities. Based on vibrating load, the response can be different. This vibrational response is depend on the intrinsic and dynamic structures properties such as mass matrix, stiffness, damping, natural frequency and etc. As the result, the identification and estimation of the parameters for analysis and design of structures under dynamic loads is required. On the other hand, in the dynamic analysis of structures, assuming proportional damping is unrealistic and is used to simplify matters. In other words, engineers in the dynamic analysis of structures assuming a constant damping ratio for all modes to determine Riley coefficients that this situation is unrealistic, because structural damping of higher modes increases so considering a proportional damping matrix could be an error in determining the structural response. As mentioned above, in this thesis, firstly modal parameters such as natural frequency, damping ratio and mode shapes having physical characteristics (mass, stiffness and damping matrixes) for proportional and non-proportional damping structures is determined by Veletsos’s method. In the second step by using the response of structure(nodal displacements), modal characterisation and physical model of structures determined by modified Lancaster’s method.

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