Structural Response To A Train Of Blast Pulses

Abstract

Air blast acting on structures in the real world rarely takes the idealised form of instantaneous pressure rise followed by smooth exponential decay. Reducing a composite load history to a simple equivalent pulse in calculations to determine damage risks overlooking additional damage that may result as a coincidence of repetitive blast pulses with the dynamic behaviour of the structure. This paper describes the response of a model structure to a train of explosively generated pressure pulses. Air-blast frequency content is analysed by means of Fourier transformation and related to structural response as a possible complement to existing methods. Correlation is sought between blast energy spectral density and structural response. Results indicate that whilst the model structure accumulated energy when successive blast pulses were in phase with the dominant mode of vibration, the interval between blast pulses need not be regular and there are limits on phase difference. Consequently blast energy spectral density may give misleading indication as to how a structure responds to a train of pulses. The conclusions are relevant to how structures might respond to internal explosions, blast in high-rise urban areas, multiple-charge demolitions and hazard assessment for distributed explosive storage sites.