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大直径薄壳钢管在部分充水情况下,由于荷载函数不连续,管壳中将出现很大的局部应力与变形,必须依靠加劲环的约束作用来消除。这个问题可用经典的圆柱壳理论来作精确分析,但计算工作过分繁冗,不切实用。本文建议从特解出发,交替使用“对称情况小本征值解”和“局部影响大本征值解”来依次满足四组边界条件中的各两组,使计算工作量可减到最少。但即使作了这样的努力,手算工作仍嫌繁琐。经过系统的分析和比较后,本文指出只要按适当间距布置加劲环并使之具有足够刚度,管壳中的局部应力及变形就能减少到可以忽略的程度,不必详细分析。设计时只须按经验拟定加劲环的间距和断面,然后复核环的变形及应力,使之具有所需的刚度并保持应力在容许范围即可。
In the partial water-filled case, the large-diameter thin-walled steel pipe will have a great local stress and deformation due to the discontinuous load function, and must be eliminated by the restraining action of the stiffening ring. This problem can be accurately analyzed by the classical cylindrical shell theory, but it is impractical to calculate the work too much. In this paper, we propose to use “small eigenvalue solution in symmetric case” and “large eigenvalue solution in local influence” alternately from the special solution to satisfy each of the four sets of boundary conditions in turn so that the computational workload can be reduced to a minimum. But even with such efforts, the manual work is still too complicated. After systematic analysis and comparison, this paper points out that the local stress and deformation in the shell can be reduced to a negligible degree as long as the stiffener ring is arranged at a proper spacing and has sufficient rigidity, without having to analyze in detail. Design time only by experience to develop the spacing and cross-section of the stiffener, and then review the ring deformation and stress, so that they have the required stiffness and keep the stress in the allowable range.