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Explosion scenarios in tunnels, the potential hazards from storage of high energetic materials and terrorist attacks have become important safety issues. The mechanical response of concrete structures exposed to impact loading can only be predicted with proper material modelling that includes the rate effect of concrete. The influence of moisture on the rate effect of concrete is studied with a Split Hopkinson Bar. The results are presented in this paper. A new testing device for very high loading rates is developed. The development of the device and a new measurement technique is presented. The first results on concrete are promising.

This report presents a new method to calculate the blast effects originating from an exploding vessel of liquefied gas. Adequate blast calculation requires full knowledge of the blast source characteristics, that is, the release and subsequent evaporation rate of the flashing liquid. Because the conditions that allow explosive evaporation are not entirely clear and the evaporation rate of a flashing liquid is unknown, safe assumptions have been adopted as the starting point in the modeling. The blast effects from a boiling liquid expanding vapor explosion (BLEVE) are numerically computed by imposing the vapor pressure of a flashing liquid as boundary condition for the gas dynamics of expansion. The numerical modeling is quantitatively explored just for liquefied propane. In addition, this paper demonstrates that often an estimate of BLEVE blast effects is possible with very simple acoustic volume source expressions. The modeling shows that the rupture of a pressure vessel containing a liquefied gas in free space develops a blast of significant strength only if the vessel nearly instantaneously disintegrates. Even if a rupture and the consequent release and evaporation of a liquefied gas extend over just a short period of time, the blast effects are minor. © 2005 American Institute of Chemical Engineers.

Dans un programme experimental, des essais de traction rapides ont ete executes sur une barre d'Hopkinson. Dans la plupart des specimens un trait de scie a ete fait. L'objectif etait la determination de l'energie de fracture dynamique du beton. Les resultats ont ete compares avec des essais quasi-statiques. Pour distinguer le comportement du materiau et de la construction, les experiences ont ete simulees numeriquement. Cela a resulte a l'observation que l'energie de fracture dynamique est approximativement equivalent a l'energie de fracture statique

In this paper shearing interferometry as used at the Prins Maurits Laboratory for studying shock wave diffraction around structures is reviewed. The performance of the shearing interferometer is illustrated by a number of applications. It is shown that, for not too complicated flow geometries, accurate density distributions of the flow field can be obtained from an analysis of the recorded interferograms. A comparison of results obtained with a numerical code, based on the flux-corrected transport (FCT) method, and experimental data also are presented.

The diffraction of weak shock waves (M

Former research showed that the rate effect on concrete tensile strength can be modelled by the description of crack extension in a fictitious fracture plane. The plane represents the initial, internal damage and the geometry of the final fracture plane. In the paper, the same approach is applied to model the failure envelope for the biaxial loading condition of static lateral compression and axial impact tensile load. The predicted failure envelope is compared with data from the experimental programme.

Experiments on concrete have shown a considerable increase of apparent tensile strength with increasing loading rate. This phenomenon can be attributed to various mechanisms such as kinetics of energy barriers and inertia effects in the vicinity of a running crack. After a general introduction into the behaviour of concrete under a uniaxial tensile stress, a model is presented which accounts for flaws in concrete and the inertia effects around a crack at high loading rates. It turns out that the quite crude model predicts rather accurately the relation between apparent strength and loading rate, the influence of concrete quality on this relation, and the relation between crack propagation velocity and loading rate.