Nonlinear compressibility effects in fluid-structure interaction and their implications on the air-blast loading of structures

Abstract

The impulse imparted by a blast wave to a freestanding solid plate is studied analytically and numerically focusing on the case in which nonlinear compressibility effects in the fluid are important, as is the case for explosions in air. The analysis furnishes, in effect, an extension of Taylor’s pioneering contribution to the understanding of the influence of fluid-structure interaction (FSI) on the blast loading of structures [The Scientific Papers of Sir Geoffrey Ingram Taylor, edited by G. K. Batchelor (Cambridge University Press, Cambridge, 1963), Vol. III, pp. 287–303] to the nonlinear range. The limiting cases of extremely heavy and extremely light plates are explored analytically for arbitrary blast intensity, from where it is concluded that a modified nondimensional parameter representing the mass of compressed fluid relative to the mass of the plate governs the FSI. The intermediate asymptotic FSI regime is studied using a numerical method based on a Lagrangian formulation of the Euler equations of compressible flow and conventional shock-capturing techniques. Based on the analytical and numerical results, an approximate formula describing the entire range of relevant FSI conditions is proposed. The main conclusion of this work is that nonlinear fluid compressibility further enhances the beneficial effects of FSI in reducing the impulse transmitted to the structure. More specifically, it is found that transmitted impulse reductions due to FSI when compared to those obtained ignoring FSI effects are more significant than in the acoustic limit. This result can be advantageously exploited in the design and optimization of structures with increased blast resistance.

The Negative Phase of the Blast Load

“…0.25 kg PE4 hemispherical explosive charges were detonated 4 m, 6 m, 8 m and 10 m away from and orthogonal to the external wall of a reinforced concrete bunker, forming a large, effectively rigid target, such that fluid-structure interaction effects [26,27] could be ignored. The charges were detonated on a 50 mm thick steel plate, placed on a level, flat concrete ground slab, enabling the detonation to be considered as a hemispherical surface burst.…”

Response of metallic pyramidal lattice core sandwich panels to high intensity impulsive loading in air

“…Recent analytical [9] and numerical [18,19] assessments indicate the FSI effect is much weaker in air and only becomes significant when (i) the overpressure is high, (ii) the core crush strength is small and (iii) the face sheet exposed to the impulse has a very low mass (inertia) per unit area. Even so, recent experiments and confirmatory numerical simulations have shown that sandwich panels with thick, strong square honeycomb cores and thick face sheets still showed significantly reduced back face deflections compared to equivalent solid plates subjected to the same very high intensity (20-35 kPa.s) impulsive loads in air [1].…”

Dynamic response and robustness of tall buildings under blast loading

“…In United States, FEMA 426 [4] provides the design measurements to reduce physical damage to the structural and non-structural components of building and related infrastructures during conventional bomb attacks, as well as attacks using chemical, biological and CBR agents. Kambouchev et al [5] discussed the nonlinear compressibility effects in fluid-structure interaction and their implications on the air-blast loading of structures. Blanc et al [6] discussed empirical method to estimate the blast loading.…”