中文摘要：

既有结构当前的抗力客观上是确定的，但其在未来时间里的变化具有随机性，宜采用随机过程概率模型描述。从概率论的角度讲，既有结构抗力的概率密度函数实际上是拟建结构抗力的条件概率密度函数。基于这一点，提出一种由拟建结构抗力的概率模型建立既有结构抗力随机过程概率模型的新方法。该模型继承了拟建结构抗力独立增量过程概率模型的优点，克服了自相关系数统计方面的困难，同时能够合理考虑既有结构当前实际具有的抗力，使既有结构的可靠度分析能够得到更为有利的结果。

英文摘要：

The resistance of existing structures at current time is determinate, but a model of stochastic process should be adopted to characterize it due to its randomness in the future. The function of probability density for the resistance of existing structures is actually the function of conditional probability density for the resistance of designed structures from the probability point of view. A method by which the model for the stochastic resistance of existing structures can be deduced from that for the stochastic resistance of designed structures is proposed. The new deduced model not only possesses the advantages of the model of independent increment process for the stochastic resistance of the designed structures, which may overcome the difficulty in determining the coefficient of auto-correlation, but also make it capable of taking the actual resistance of existing structures at present into account reasonably. This contributes to the benefit result of reliability analysis of existing structures.