The design of laminated glass under time-dependent loading

Laminated glass is a layered sandwich structures composed of elastic glass plies bonded by viscoelastic polymeric interlayers, which produce the mechanical shear-coupling of the plies under flexural loads. Here, we analytically solve the time-dependent problem of a simply-supported three-layered sandwich-beam with linear-viscoelastic interlayer under a loading/unloading history, showing that its gross response is strongly affected by the rheological properties of the polymer, here modeled by Wiechert–Maxwell units. The results, confirmed by numerical simulations, are compared with those obtainable with an approximate solution, commonly used in the design practice, where the interlayer is modeled by an equivalent linear-elastic material, whose properties are calibrated according to temperature and characteristic duration of the applied loads. For this, practical design rules to account for superimposition of applied loads are proposed. alitative properties of the two approaches are analytically discussed, evidencing those load-histories under which the approximate solution is, or is not, conservative for what stress and deflection evaluation is concerned.