Dependence of the blast load penetrating into a structure on initial conditions and internal geometry

• Factors affecting the load penetrating a structure were investigated experimentally.
• Pressures and impulses at frontal façades generated different initial conditions.
• The pressure history on the target wall is mostly effected by the inner geometry complexity.
• Waves diffraction inside the structure filters out high-frequency pressure changes.
• Scalable time constant can characterize the load developing inside a complex structure.

An experimental study investigated the dependence of the blast load penetrating into a structure on initial conditions and internal geometry. The imposed pressure and impulse profiles at the structures’ frontal façades were varied to generate initial conditions with very different pressures but similar peak impulses to which structural models of varying complexity were exposed. Results show that the peak impulse recorded at the models’ back wall, the target wall, is independent of internal geometry. However, the pressure profiles at the target wall depend heavily on internal geometry in terms of both peak overpressure and wave diffraction pattern. Moreover, the pressure profile developed inside the structure depends strongly on the imposed impulse rather than the imposed pressure profile at the frontal façade. Repeated reflections inside the structure were found to effectively filter out high-frequency pressure changes inside the structure, leading to the possibility of rapid prediction tools for more complex structures. For the first time, a strong indication was found that a scalable time constant can be attributed to a complex structure that characterizes the load developing inside. Based on these findings, an application is presented in which forming a similar impulse is sufficient for correctly simulating large explosions in scaled-down models.