中文摘要：

基于任一时段内的结构时变可靠度可通过求解一等效的单个功能函数来获得的认识，提出了一种改进的时变可靠度计算方法。首先以简单的梁柱构件为例，分析了结构功能函数为非线性的原因。接着揭示了满足结构非线性极限状态方程的荷载解可能会存在着两个值的特殊现象。然后通过引入一假想的综合各抗力因素的变量来缩减响应面方程中的变量数目，使得响应面方程能简洁地表达出来。最后应用该思路对一承受全跨永久荷载和半跨可变荷载作用下的混凝土拱结构进行了分析，结果表明极限荷载曲线具有较高的非线性程度，且该方法具有较高的精度。

英文摘要：

Based on the knowledge that the structural time-dependent reliability can be calculated by solving a single equivalent performance function for a certain period, an improved method is proposed for time-dependent reliability calculation. First, the reason why the performance function is nonlinear is discussed for the simple beam and column members. Second, a specific phenomenon is found that there are two possible load values to satisfy the nonlinear limit state equation. Then, an imaginary variable is introduced, which considers the influences of resistant factors, thus to reduce the number of variables in response surface equation. So the equation can be expressed compactly. Finally, a concrete arch under full-span dead load and half-span live load is analyzed according to the proposed method. It shows that the ultimate load curves are highly nonlinear and the method is accurate.