Time-variant reliability problems commonly occur in practical engineering due to the deterioration in material properties, external disturbance and other uncertain factors. Considering the non-probabilistic method can effectively deal with the uncertainties in reliability analysis. Based on the stress–strength interference method and interval method, a time-variant stress–strength interference interval model is established by considering the stress and strength as time-variant intervals. And then, the stress and strength intervals are converted into the normalized intervals to define the non-probabilistic time-variant reliability index [Formula: see text] according to the different relationships between the limit state function and the normalized intervals. The structural state at any time can be described by the non-probabilistic time-variant reliability index [Formula: see text]. In addition, a strength power exponential degradation model is given as an example to clearly verify the non-probabilistic time-variant method, and the analysis results are compared with the interval method, the uniform distribution stress–strength interference method and the normal distribution stress–strength interference method, which confirm that the non-probabilistic time-variant method is feasible and valid to analyze the structural time-variant reliability without the probability density functions of the parameters.

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The propagation of TNT blast wave in the air is simulated by using the LS-DYNA finite element analysis software, to study the influence of boundary condition on the overpressure of blast shock wave. In the simulation, three kinds of blast equivalent are selected, which are 5.12 kg, 51.2 kg and 512kg. Angles between four groups of measuring points which are selected and positive X axis are 0°, 30°, 45°, 60° respectively. In addition, two boundary conditions are selected in the simulation, the zero displacement constraint boundary and the non-reflective boundary. The results indicate that simulation results have better stability when the scaled-distance Z>1.2. Secondly, different boundary conditions have different influences on shock wave overpressure, and non-reflective boundary condition will reduce the overpressure value in the vicinity of the boundary. What's more, reasonable selection of measuring points should be emphasized. For example, to select the measurement point of 45 °angle with positive X axis to obtain the overpressure value is more accurate for a 1/4 cylinder model.