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 $\eta$ 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 $\eta \in [0,+\infty )$. 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.

由于材料性能，外部干扰和其他不确定因素的影响，在实际工程中通常会出现时变可靠性问题。考虑非概率方法可以有效处理可靠性分析中的不确定性。基于应力-强度干涉法和区间法，以应力和强度为时变区间，建立了时变应力-强度干涉区间模型。然后，将应力和强度区间转换为归一化区间，以定义非概率时变可靠性指标$\eta$根据极限状态函数和归一化间隔之间的不同关系。任何时候的结构状态都可以用非概率时变可靠性指标来描述$\eta \in [0，+\infty ）$。另外，以强度幂指数退化模型为例，清晰地验证了非概率时变方法，并将分析结果与区间法，均匀分布应力-强度干涉法和正态分布应力进行了比较。 -强度干扰法，证实了非概率时变方法在分析结构时变可靠性时不需要参数的概率密度函数，是可行和有效的。