Explosively generated air presuure waves for structural forcing

The aerial blast wave generated by a small explosion may be used to produce impulsive forcing of structures with natural periods longer than approximately 1 msec; the free response of such structures may then be determined. A technique has been developed using spatial distributions of explosive whereby it is possible to generate waves of much longer durations and of a much wider range of shapes, so that studies of the forced response of structures are made feasible. The technique has been applied to the generation of a blast waveform of the same shape as that of the sonic bang, for example, thus permitting studies of response to sonic bangs to be carried out without the necessity of flying supersonic aircraft and without recourse to scaled model experiments. Certain differences between the simulated and real sonic bang waveforms raise questions as to the adequacy of the simulant, and criteria for acceptability of simulation are discussed. To provide information relevant to these questions, the Fourier transforms of the simulant waves are compared with those of sonic bangs. The results lend support to the use of the simulants in structural response studies.