为了对既有结构的可靠性进行正确评估，必须考虑时间变化的影响，对目前可靠度分析中采用的只考虑荷载随时间变化的半随机过程模型进行改进。基于结构抗力和作用效应相互独立的基本假设，充分依据作用效应和抗力的时变特性，考虑结构抗力为独立增量过程，并计算了抗力的自相关系数，得到了计算结构失效概率的近似算法，建立了结构时变可靠度计算的全随机过程模型。通过实例验证，该方法简单易行，便于工程应用，为基于时变可靠度理论的既有结构评估和寿命预测提供理论依据。

In order to effectively evaluate existed bridges' reliability, the effect of bridge service time on bridge reliability was considered. To extend the so-called semi-stochastic process model for specified in the design code in analysis reliability for existing structure, assuming that the structural resistances and the action effects are independent, based on the characteristics of the resistance and action effects variation with time, considering the resistance is an independent increment process and calculating the self-revelation coefficient of resistance, an approximate algorithm of failure probability was developed. And a fully stochastic process model was developed to analysis time-dependent reliability. Through the example,this method is simple and convenient and can supply a basis for structural assessment and service life prediction.