How dissipative devices could enhance the capacity of glazed surfaces under impacting blast waves

摘要

Dissipative devices, interposed between a glazed surface and its supporting back structure, can efficiently contribute to safeguard the integrity of glass under the impinging action of a shock wave generated by an explosion. This is theoretically demonstrated with reference to a paradigmatic model problem, in which a glass pane is connected to a load-bearing structure via a dissipative unit. This is composed of a movable piston in unilateral contact, on its two opposite sides, with shock absorbers capable of plastic dissipation, which are activated respectively in the compression and suction phases of the blast wave, modeled by Friedlander equation. The nonlinear dynamic equations are solved by a customized algorithm, which detects the various yielding stages of the shock absorbers and considers the possible impacts of the piston with the back structure, and the consequent energy loss, when the device reaches the end of its stroke. Through a parametric analysis, criteria are proposed for the optimal design of the shock absorbers as a function of the form of the blast wave and the type of supporting structure, especially to limit the rebounds deriving from impacts, which can compromise the integrity of the glass. The proposed technical solution is compared with a more classical dissipator consisting of a linear viscous dashpot, which is not as efficient as the previous one in limiting the effects of the first compression phase of the blast wave, but can considerably reduce subsequent oscillations. A hybrid device, where viscous dampers and shock absorbers are integrated in parallel, represents the best compromise.