Abstract
Fortification structures, both military and civilian, are designed to resist a blast explosion to some extent. Their technical condition after a blast load must be assessed in a fast and reliable way to enable the users’ decision about the future use of the structure. Preferably, for the assessment of the protective structure, the non-destructive testing method should be used. To assess the suitability of ultrasound testing method for fortification structures built from steel fiber reinforced concrete, an investigation in a laboratory and in situ was conducted, together with numerical simulation and statistical evaluation. The numerical simulation of the blast load of a steel fiber reinforced concrete slab was conducted using multiphysics simulation software with the aim to verify basic parameters of the field experiment. During the field tests, several slabs were loaded by plastic explosive and changes in the structure of the slabs, before and after the blast load, were examined using the ultrasound pass-through method. After the field tests, the slabs were subjected to a destructive laboratory test to determine their residual strength. Subsequently, the data sets obtained from the measurements were tested using functional data analysis. The results from the ultrasound pulse method show that specimens after a dynamic blast load can in some cases increase the strength of their cement matrix.
Highlights
The change in the safety environment is an increasingly topical issue of design and construction of structures that would be able to withstand permanent and variable load but especially accidental action, which acts briefly
Based on the results of measurement by the ultrasound pulse method, there were observable changes in the velocity of the ultrasound wave passing through the specimens after the previous blast load, i.e., there was an increase in the speed of the ultrasound waves
It is possible to deduce a partial conclusion that there was a blast loading failure, and simultaneously the formation of cracks in the internal structure of the concrete slab was confirmed by NDT
Summary
The change in the safety environment is an increasingly topical issue of design and construction of structures that would be able to withstand permanent and variable load but especially accidental action, which acts briefly. Their value is significant [1,2], the ability to withstand loads such as t military fortifications and defense infrastructure. The assessment of the condition of critical infrastructure usually does not take into account repeated blast load, as this kind of load is considered rare For these reasons, design evaluation methods are based on a combination of non-destructive and semi-destructive methods [3]. If it is assumed, in the case of military fortifications, that their further availability can sustain repeated load, it is not possible to disrupt the integrity of the envelope of the structure, for example, by a core bore
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