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混凝土结构徐变应力分析目前主要采用初应变法,在每一时段内假定应力为常量,为了保证计算精度,必须把时间步长取得比较小,因而要消耗较多的计算时间。本文假定在每一时段内应力为线性变化,应力的时间导数为常量,给出一套隐式解法。文中主要包括三部分内容:(一)假定在一个时段内应力的时间导数为常量,利用指数函数的特性,给出弹性应变、可复徐变及不可复徐变的应变增量的算式;(二)给出非均质混凝土结构的隐式解法;(三)给出混凝土松弛系数的隐式算法。从文中给出的结果可见,与显式解法相比,隐式解法并不复杂,在每一步的计算中,两种解法的计算量基本相同,但由于假定每一时段内应力是线性变化的,隐式解法比显式解法具有高一级的计算精度。如果保持同样的计算精度,隐式解法可采用较大的时间步长,从而可节省大量计算时间。
The creep stress analysis of concrete structures mainly adopts the initial strain method. In each time period, it is assumed that the stress is constant. In order to ensure the calculation accuracy, the time step must be obtained relatively small, and therefore it takes more calculation time. This paper assumes that the stress is linear in each period, and the time derivative of the stress is constant, giving a set of implicit solutions. The article mainly includes three parts: (a) Assume that the time derivative of the stress is constant in a period of time, and use the characteristics of the exponential function to give the formula of the strain increment for elastic strain, creep and irreducibility creep; b) Give an implicit solution to the heterogeneous concrete structure; (c) Give an implicit algorithm for the relaxation coefficient of concrete. From the results given in the article, we can see that compared with the explicit solution, the implicit solution method is not complicated. In each step of the calculation, the two kinds of solution have basically the same amount of calculations, but it is assumed that the stress is linearly changed in each period. The implicit solution has a higher level of computational accuracy than the explicit solution. If the same calculation accuracy is maintained, the implicit solution can use larger time steps, which can save a lot of calculation time.