A simplified numerical method for both lower and upper-bound limit analyses of 3-D structure has been developed in our previous work. The load-carrying capacities of 3-D pipelines with either one or two part-through defects of various geometrical configurations were calculated by the proposed method. In the present paper, the effects of the distance between two defects on the load-carrying capacity of pressure vessels are evaluated and discussed in details. Using curve-fitting schemes, an empirical formula for obtaining the load-carrying capacity of pressure vessels with double defects from that of pressure vessels with a single defect are proposed. Some engineering suggestions are presented simultaneously. All the numerical results confirm the applicability of the simplified numerical method. [S0094-9930(00)00102-5]

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