Theoretical analysis of stress and strain propagation during impact

ConclusionsWith some exaggeration it can be said that we now have at hand the necessary tools to analyse the sequence of events when a building is subjected to impact or impulsive loadings. The degree of precision in our analysis may be very poor, however, since we often do not know the relevant parameters well enough and, even if we did, the computation costs might be prohibitive. To obtain useful solutions for the practice much more research work is needed.To begin with one example, the damping effect of debris, floorings etc on top of an impacted floor slab has not been studied. Likewise, some highly non-linear phenomena, such as the crushing and cracking occurring in the contact zone at high impact velocities, are poorly understood. To proceed from there, little has been published on spalling from the surface opposite an impact, and only crude predictions of local penetration are possible. Some additional information may exist here in classified papers from defence research.Wave propagation in simple elastic media can be predicted but the presence of complex boundaries severely complicates the analysis and non-linearities in material behaviour and geometry further cut down the number of solvable cases. With the aid of numerical methods, primarily the finite element method, complex cases have been handled. The efforts of program location, data preparation, running costs, and data presentation are nevertheless considerable.For some situations such as designs against external and internal blasts, design formulas and diagrams already exist in the literature, though more detailed methods may be expected to emerge in these areas as well as in others in the future.

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