Natural frequencies and damping ratios of multi-layered laminated glass beams using a dynamic effective thickness

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 a linear-elastic material, the viscoelastic interlayers determine a non-linear behaviour of the laminated structure that must be taken into consideration. In this paper, an analytical model based on the effective thickness concept and the Ross, Kerwin and Ungar model is proposed to predict the dynamic behaviour of multi-layered laminated glass beam-like structures with different boundary conditions and at different temperatures. This analytical model allows the simplification of the calculus on this multi-layered laminated components opposite to use time-consuming numeric models. In this work, a study was carried out on a multi-layered laminated glass beam composed of three annealed glass layers and two polymeric interlayers. The analytical predictions are validated by numerical simulations and experimentally using operational modal analysis tests. The proposed model predicts the natural frequencies with errors less than 5% whereas the discrepancies in damping ratios are less than 50%