Keywords: laminated glass, polyvinyl butyral, viscoelastic behaviour, operational modal analysis, finite element method, system identification.

Laminated glass is usually composed of two glass layers and an interlayer of polyvinyl butyral (PVB). The static behaviour of laminated glass is nowadays well understood and several design codes such as [1] are available. However, as a result of its complex nature, the dynamic response of laminated glass is an important research topic. In modern cities the number of buildings including structural glazing systems is increasing and there is clearly a need to understand the dynamic behaviour of both the whole building and that of its components. Wind loads may cause important vibrations of window panes and the maximum amplitude of these vibrations is influenced by the amount of damping of the window pane. The failure of a glass panel usually does not lead to the collapse of a building however, falling glass pieces may injure pedestrians that walk by [2].

This paper reviews the results obtained from measurements taken at different points of a window pane which is 1015 mm in length by 472 mm in width. Measurements were carried out subjecting the structure to different actions:

• Impulse force generated by the impact of a metallic marble
• Ambient vibration test at different temperatures
• Sound excitation generated by two loudspeakers

The objective of the paper is to set up a suitable three-dimensional finite element model in order to predict the dynamic behaviour of laminated glass. Power spectral densities (PSD) were calculated in order to identify intermittent excitation sources such as people walking by. The acceleration time histories corresponding to the ambient vibration test and the one with sound excitation were processed using the stochastic subspace identification method and the enhanced frequency domain decomposition to estimate vibration mode shapes and damping values.

A three-dimensional model has been set up for the numerical simulation of the tests. The commercial FEA software ANSYS has been used for the simulations. The agreement between experimental and predicted fundamental vibration frequency and damping ratio is quite good.

1

ASTM E1300-09a, "Standard Practice for Determining Load Resistance of Glass in Buildings".

2

E. Byrnes, "Falling glass injures pedestrian", Toronto National Post, 15 Aug 2011.

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