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The determination of the blast protection level of civil engineering buildings components
against explosive effects represents a topic of crucial importance, in current practice. However, some key aspects of blast resistant structures design have been only marginally considered in the last decade, and currently still require appropriate regulations. This is especially true in the case of windows and facades, where the intrinsic material brittleness is the major influencing parameter for blast-resistant assemblies. While blast assessment of buildings and systems is usually achieved by means of experimental investigations, as well as numerical simulations, general regulations and guidelines are currently missing.
In this regard, the European Reference Network for Critical Infrastructure Protection (ERNCIP) Thematic Group “Resistance of Structures to Explosion Effects” attempts to develop guidelines and recommendations aimed to harmonise test procedures in experimental testing of glass windows under blast, as well as standardized approaches for their vulnerability assessment via numerical modelling. In this paper, major Thematic Group outcomes and next challenges are briefly summarized.
Due to the market needs on steel for high demanding applications non-destructive methods for the determination of steel cleanliness using ultrasound have to be adapted to increase sensitivity respectively.
The basic idea is that the new standard proposal should follow the basic line outs from SEP 1927 and ASTM E588. Additional to these relatives the standard should be open to different types of specimen and inspection frequencies to cover a wide range from bars, rings and plates as well as different inspection sensitivities. For an enhance in resolution the standard draft focuses on immersion focal beam probes which should be selected according to the geometry of the specimen. The selection should be proved with the aid of simulation tools. The frequency shall be at least 10 MHz. For specimen thicknesses of less than 6 mm a frequency of at least 25 MHz shall be used.
Calibration procedures had to be improved significantly compared to the old standards to allow proper sizing of indications. Therefore calibration procedures shall take signal processing into account. For detailed evaluation of the amplitude dependency and for calibration a reference block with a sufficient number of reflectors has to be used. The recorded echo height shall be directly transferred into an equivalent disc shaped reflector EDSR by a distance amplitude curve.
The novelty in this standard draft will be that based on 3D measurements and 3D evaluation the amplitude criterion of an indication becomes just one among some other criteria. This standard takes the signal amplitude, signal amplitude distribution and signal travel time for classification into account.
The standard draft will be open to the definition of the volume to be investigated to be set by the user. This will make evaluation more comparable to other methods because the inspected area has to be user defined.
We recommend CEN/TC 138 to decide on a work item for this proposal to become an EU and an ISO standard using Vienna agreement.
The research leading to these results has received funding from the European Union's Research Fund for Coal and Steel (RFCS) research programme under grant agreement n° RFSR-CT-2013-00014.