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回顾了对预应力混凝土构件长期反拱变化规律的研究及认识过程;提出了一个经验公式,大大简化了预应力混凝土构件长期反拱的精确计算工作。该经验公式既能适用于“全”预应力,也能适用于“部分”预应力混凝土构件长期反拱值的计算。同时,对预应力混凝土构件长期挠度的估算也提出了一个经验公式。长期反拱和挠度的两个经验公式都考虑了四个主要影响因素作为自变量(即钢筋的配筋率及其位置与混凝土的徐变和收缩)。用试验数据全面地进行了对比,给出长期反拱系数θp(t→∞)的终极值的可变范围为-3～+3.5,其通常变动范围是-0.5～+2.8,而不是固定的值+2.0。长期挠度也不能简单地简化为短期挠度的2倍。给出了实际工程的检测结果和计算例题并提出了对现行《混凝土结构设计规范》第8.2.5条和第8.2.6条的修改建议。
Reviewing the research and cognition of long-term inverse arching of prestressed concrete members, an empirical formula is proposed, which greatly simplifies the accurate calculation of long-term reverse arching of prestressed concrete members. The empirical formula can be applied both to “all” prestress and to the calculation of the long-term inverse camber of “part” prestressed concrete members. At the same time, an empirical formula is also proposed for estimating the long-term deflection of prestressed concrete members. Long-term inverse arching and deflection of the two empirical formulas have considered four major influencing factors as independent variables (ie reinforcement ratio and location of concrete and concrete creep and shrinkage). The experimental data are compared in a comprehensive way. The final value of the long-term arched coefficient θp (t → ∞) is given by a variable range of -3 ~ + 3.5. The typical range of variation is -0.5 ~ + 2.8 instead of fixed Value +2.0. Long-term deflection can not simply be reduced to 2 times the short-term deflection. The test results and calculation examples of the actual project are given and the suggestions for modification of the existing 8.2.5 and 8.2.6 of “Code for design of concrete structures” are put forward.