Gaps in the post-breakage out-of-plane bending stiffness assessment of 2-ply partially damaged laminated glass elements under short-term quasi-static loads

The mechanical response of partially fractured laminated glass elements is rather challenging to assess and quantify. In this paper, the attention is focused on the contribution that fractured glass can offer to the out-of-plane bending stiffness of a partially broken 2-ply laminated glass element. Literature and technical standard assumptions are briefly recalled and discussed, pointing out the effect of cracked glass removal in structural calculations. Original experimental tests in beam-like setup are then introduced, for a total of 60 deflection measurements, to focus on the out-of-plane bending response of 2-ply laminated glass samples bonded by EVA films, and composed of annealed (AN), heat-strengthened (TVG) or fully tempered (ESG) glass panes, respectively. With the support of numerical modelling, the quasi-static response of the tested specimen is verified and used as a reference for the calibration of an equivalent cracked modulus for fractured glass only, which is able to account for the type of glass, size and type of fragments and loading setup. Literature bending test results for 2-ply laminated glass elements are also used in support of the parametric analysis. Comparative analyses are presented based on other simplified strategies of literature, with a critical discussion of possible effects and limits.