An upper-bound approach to static stress analysis of pipelines

In the stress analysis of pipelines, it is common practice to ignore the effect of shearing and axial forces on the design section and consider only the bending moment, the torque, and sometimes the internal pressure. But in a pipeline network, which is a complex system, the shearing and/or axial forces may be great enough to considerably contribute to the design stress. Consideration of all the above loads in the stress analysis of pipelines requires the application of finite element methods. This paper describes a simple approach to the problem which covers the effect of all the above loads and provides the designer with an upper-bound design stress. Alternatively, it may be used to quickly locate the design section and then apply finite element methods to this section only, to determine a more exact design stress. The upper-bound design stress may be considered as a lower-bound to the yield stress of the pipeline material. The approach requires no illustration of loads on the design section, therefore it can be easily incorporated into a computer program without any graphical aid and interaction of the designer.