An accurate material representation of polymeric interlayers in laminated glass panes has proved fundamental for a reliable prediction of their response in both static and dynamic loading regimes. This issue is addressed in the present contribution by examining the time–temperature sensitivity of the shear stiffness of two widely used interlayers made of polyvinyl butyral (TROSIFOL BG R20) and ethylene-vinyl acetate (EVALAM 80-120). To that end, an experimental program has been executed to compare the applicability of two experimental techniques, (i) dynamic torsional tests and (ii) dynamic single-lap shear tests, in providing data needed in a subsequent calibration of a suitable material model. Herein, attention is limited to the identification of material parameters of the generalized Maxwell chain model through the combination of linear regression and the Nelder–Mead method. The choice of the viscoelastic material model has also been supported experimentally. The resulting model parameters confirmed a strong material variability of both interlayers with temperature and time. While higher initial shear stiffness was observed for the polyvinyl butyral interlayer in general, the ethylene-vinyl acetate interlayer exhibited a less pronounced decay of stiffness over time and a stiffer response in long-term loading.

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Many examples of glass loadbearing structures such as handrails, panes, beams and columns can be found in modern architecture. Most of these elements are made of laminated glass panels. There is a general lack of knowledge about the transfer of shear forces between the glass plies in perpendicularly-loaded laminated panels. This transfer depends significantly on the stiffness of the polymeric interlayer, which is timedependent and temperature-dependent. There are several computational methods for the design of laminated glass that take the shear coupling of the glass plies into account, e.g. analytical methods, numerical modeling and also the draft of European code. These methods need to be verified experimentally. This paper reports on rectangular double-laminated glass panels in a shortterm displacement controlled four-point bending test with an EVA and with a PVB interlayer under a constant temperature. These tests were performed at CTU in Prague. Our experimental results show that panels with an EVA interlayer had greater bending stiffness than panels laminated with PVB and achieved higher ultimate load values. The experimental data were further compared with simplified analytical methods, such as the European draft prEN 16612 and the Enhanced Effective Thickness approach and also a numerical FEM model. Numerical and EET methods results were in good agreement with the experimental data. The way in which the specimens broke was a characteristic feature of laminated glass. The shards remained attached to the interlayer, proving that laminated glass panels can be used safely above the heads of users of the structure. Simplified methods and numerical models validated by experimental tests on perpendicularly-loaded laminated glass panels enable these structures to be designed safely and economically for practical uses.

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