Elastic-plastic response of plates subjected to cleared blast loads

A commonly used approach for the engineering analysis of structures subjected to explosive loads is to approximate the problem as an equivalent Single-Degree-of-Freedom (SDOF) system and to use elastic–plastic response spectra. Currently, the response spectra that exist in the literature do not take into account the fact that blast wave clearing will occur if the target is not part of a reflecting surface that is effectively infinite in lateral extent. In this article, response spectra for equivalent SDOF systems under cleared blast loads are obtained by solving the equation of motion using the linear acceleration explicit dynamics method, with the clearing relief approximated as an acoustic pulse. The charts presented in this article can be used to predict the peak response of finite targets subject to explosions, and are found to be in excellent agreement with a finite element model, indicating that the response spectra can be used with confidence as a first means for predicting the likely damage a target will sustain when subjected to an explosive load. Blast wave clearing generally serves to reduce the peak displacement of the target, however it is shown that neglecting clearing may be unsafe for certain arrangements of target size, mass, stiffness and elastic resistance.