An analytical method on circumferential cracked submarine pipe-in-pipe system

For cracked submarine pipe-in-pipe system, as a typical three-dimensional finite boundary composite structure, a new and very simple method to determine the stress intensity factors has been proposed by using a new concept of crack surface widening energy release rate and the principle of virtual work. This kind of energy release rate can be defined by the curved surface integral and the work done by the external loads. From the present discussions a series of stress intensity factors are derived for the circumferential cracked pipeline. The practical examples show schematically that uncracked inner pipe may delay failure for the pipe-in-pipe structures.