تحلیل مدال تجربی شبکه دو لایه با سیستم اتصال گویسان به روش ورودی-خروجی و تنها-خروجی

Dynamic characteristics of structures including natural frequencies, damping ratios and mode shapes are among the most important characteristics expressing the behavior of a structure that have many applications in civil engineering. These characteristics are usually determined through modal analysis of the structure, for which several experimental and non-experimental methods have been developed. In the present work, the dynamic characteristics of a laboratory model of double layer grids with ball joint system were identified through experimental modal analysis. By applying appropriate dynamic stimulation to the laboratory model, frequency response functions and power spectral density functions were measured in different degrees of freedom. Then, from the rational fractional polynomial input-output modal analysis method and the stochastic subspace identification output-only modal analysis method, the dynamic characteristics of seven vibration modes of the grid in the frequency range of 0 to 100 Hz were identified from the two modal analysis methods. The results showed that while the modal damping ratios identified from input-output and output-only methods do not show a good agreement, but the natural frequencies have a very good agreement, so that the maximum relative difference of the identified frequencies is 2%. In addition, the mode shapes obtained from the two methods have a modal assurance criterion of at least 0.8, which indicates their good compatibility.