A practical way to calculate the response of laminated glass is to consider both glass and polymeric interlayer as linear elastic materials; the viscoelastic behavior of the polymer is evaluated assuming equivalent elastic moduli, that is, the relaxed moduli under constant strain after a time equal to the duration of the design action. Here, we analytically solve the time-dependent problem of simply-supported laminated-glass beams, modeling the response of the polymer by a Prony’s series of Maxwell elements. The obtained results, in agreement with a full 3-D viscoelastic finite-element numerical analysis, emphasize that there is a noteworthy difference between the state of strain and stress calculated in the full-viscoelastic case or in the aforementioned “equivalent” elastic problem. The second approach gives in general results that are on the side of safeness, but the design may be too conservative for short-time actions, whose duration
depends upon the polymer type
