Modern standards and codes of design practice require the evaluation of the response of glazed surfaces with respect to impulsive dynamic actions in order to avoid brittle failure. The soft-body impact test allows to reproduce the effect of the accidental impacts of human. This is a free-boundary value problem, since the imprint of the impinging mass changes with the resultant of the contact force. Firstly, the dynamic problems is analyzed with a simplified approach based upon an equivalent and non-linear 2-DOF system. The maximum stress in the panel, possibly taking in account the geometric non-linearities, can be directly obtained via energetic considerations, with reasonable assumption. Successively, in order to analyze complex problems in real structures, an engineered FEM tool has been developed, which uses non-linear unilateral beam elements that can be implemented in most commercial software for structural analysis. The prediction of the aforementioned methods is compared with experiments and results obtained with specific software for structural glass, with in general an excellent agreement. The limits of applicability of the simplified approach are investigated. The developed FEM tool is very accurate and represents an improvement with respect to dedicated software allowing to consider multiple impacts, damping and high structural complexity.