Lower and upper bound limit analyses for pipeline with multi-slots of various configurations

Using the finite element method and mathematical programming techniques, a simplified numerical method for both lower and upper bound limit analyses of a 3-D structure has been developed in our previous work. In this paper, the lower and upper bound limit loads of the 3-D pipeline with one or two part-through slots of various geometrical configurations are calculated by the proposed method. The slots considered here are small spherical slots, circumferential slots, axial slots and large area slots. The loading considered includes internal pressure, axial tension and bending moment at both ends, and the radial loading path scheme is adopted. The effects of slot number and type on the load carrying capacity of the pipeline are discussed in detail. The discrepancy between lower and upper bounds is below 20%. All the numerical results confirm the applicability of the procedure.