A brief review of experimental methods for testing blast effects on structures is presented. Methods are classified in four groups: field tests, shock tubes, pendulum systems, and new techniques (blast simulator). Description of each method is given together with overall specification of possible instruments used in each test. In today’s modern era of computers which are becoming powerful tool implemented in all aspects of life and also scientific research, comparison of experimental and numerical techniques is also given. Comparison of data obtained from different experimental methods show that careful planning and execution leads to reliable results in terms of pressure, impulse, stress, and damage quantification.
Various expressions have been given in the literature for calculating blast wave parameters. Without experimental testing, it is difficult to determine which expression will predict the actual measurements more realistically. In this paper, a statistical analysis of two blast wave parameters, maximum overpressure and pressure-time diagram decay coefficient, was conducted based on field tests of the cylindrical TNT charge free-air detonation. Simple numerical simulation was also performed in order to compare the obtained maximum overpressures with the field test measurements. A comparison of the maximum free-field overpressures provided insights on the influence of the air mesh size as this proved to be a critical parameter. Statistically obtained blast wave decay coefficient and the maximum overpressure was compared with the analytical expressions given by different authors to determine the most appropriate description of experimental tests. Expressions are given depending on the scaled distance, i.e. the ratio of standoff distance to measuring sensors and cubic root of the charge mass. Expressions for blast wave parameters are used for a quick approximation of blast load for further analysis of structural elements, so their accurate determination ensures more realistic blast analysis and safer design.
Blast wave intensity depends on several parameters, namely: explosive material type, charge weight, shape and orientation, detonation point position, detonation initiator type (primary explosive type), the position (distance) of the explosive charge in relation to the intended target (standoff distance) and ground surface. Environmental conditions, particularly air temperature, humidity and atmospheric pressure, also influence blast pressures. It is difficult to accurately predict the blast wave action on target structures if all of these parameters are considered. This research concentrates on the influence of the shape of the explosive charge on blast pressure measurements. Spherical and hemispherical charge shapes are considered usual and, as such, accurate and reliable analytical expressions for the blast wave pressure approximation are available. The form and propagation of spherical charge blast waves are considered to have been thoroughly studied and known. In today's urban and guerrilla warfare, speed of action is a crucial factor. Rendering the careful shaping of explosive charges is time consuming and unnecessary, hence the need for investigating different charge shapes, other than spherical. This investigation consisted of field range experimental measurements of the incident (freefield) and reflected pressures caused by detonating differently shaped charges. The shapes considered were: spherical, cylindrical and rectangular. The experiments were numerically validated and verified using ANSYS Autodyn hydrocode software. Numerical simulations utilised a coupled Euler-Lagrange planar solver, using an ideal air environment and PEP500 explosive material. Charge shapes varied, according to the experimental outline, and the measuring points were constant, to allow comparison of the measured data.
The ever-present threat of terrorist attacks in recent decades gives way to research towards blast-resistant design of structures. Columns, as one of the main load-bearing elements in residential buildings and bridges, are becoming interesting targets in bombing attacks. Research of column blast load behavior leads toward increased safety by identifying shortcomings and problems of those elements and acting accordingly. Field tests and numerical simulations lead to the development of new blast load mitigation technics, either in the design process or as a retrofit and strengthening of existing elements. The article provides a state-of-the-art literature review of filed blast load tests and numerical simulations of a bridge and building columns.
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