Multi-layered laminated glass panels are those with at least three monolithic glass layers and two viscoelastic interlayers. Multi-layered laminated glass panels are commonly used in floors, roofs and other horizontal glazing accessible to the public where a high level of security is required. Although the glass can be consider as a linear-elastic material, the viscoelastic interlayers determine a non-linear behavior of the laminated structure that must be taken into consideration. In this paper, a dynamic effective thickness is proposed to predict the natural frequencies and damping ratios of multi-layered laminated glass beam-like structures with different boundary conditions and at different temperatures. Furthermore, the presented dynamic effective thickness can be also used to any frequency domain calculations such as displacements and stresses. To validate the proposed model, operational modal analysis was carried out on a multi-layered laminated glass beam to obtain the experimental natural frequencies and damping ratios at 20, 25, 30 and 35℃. Moreover, a finite element model of the beam was also assembly for the sake of comparison. The proposed model predicts the natural frequencies with errors less than 5%, whereas the discrepancies in damping ratios are less than 50%.