This paper presents an analytical mathematical model for the thermal expansion analysis of pipe-in-pipe systems with multiple bulkheads. This analytical method is extended to study the effects on thermal expansion of multiple bulkheads for given internal installation temperature, operating temperature, tie-in spool piece arrangement, pipe submerged weight, seabed friction, pipe cross sectional area, pressure and axial stiffness of the pipes. The advantage of this method is that it yields purely analytical solution and that the analysis results provide the interaction forces in any cross section of the pipe-in-pipe system as well as the stresses and strains in both the inner and outer pipes, which provide enough information to optimize the pipe-in-pipe system design, especially at the bulkhead location. The examples illustrated in the paper show that with the application of multiple bulkheads in the pipe-in-pipe system, the interaction forces between bulkheads and pipes can be reduced, which allow less onerous bulkhead design.
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