The shock spectrum dip effect

The shock spectrum dip effect, for a structure subject to transient excitation, is investigated, with use being made of controlled laboratory shock experiments. A rough understanding of the phenomenon is provided by observing that a structure on a non-rigid foundation tends to act as a dynamic vibration absorber for frequencies corresponding to its fixed base natural frequencies. The two mathematical models used provide information helpful in distinguishing between ordinary shock spectra and design shock spectra, and thus in developing shock design values for future structures.