Project Phase

This is the 'normal' start option, where both the pipeline and surrounding soil and supports are considered to be 'stress-less'.

This option transfers the pipeline shape in the same way as is the case when in design function 5 the unlock option is used. This means, that the external supports (soil included), specified in this database, are attached to the pipeline at their original 'zero'-deformation points.

In case the support system and the loadings and the pipeline properties are the same as in the database from which the deformation shape is taken, then the transferred shape will be the equilibrium state in the new situation as well.

This equilibrium results because the set of external support reactions F(e) generated in the new situation equals the imaginary set F(i). The facility may be used for an 'intelligent guess' to start a new series of calculations. Or to study the influence of small changes in support or pipeline conditions, which cannot be done with the unlock facility because that facility only allows the loading magnitudes and combination to be altered.

A further application is the situation that due to a long calculation time or iteration process with difficulty in the Parent project the iteration process is reset leading hopefully to a faster result.

Continue calculations are only allowed if the setting in the Parent is Initial because after Phasing the results may be unreliable and after Pre-Displacement the calculation is useless as the displacements are fixed. Continue is, however, possible in case the calculations in the Parent are material non-linear.

The phasing option allows the initialisation of the pipe/soil structure by means of import of pipeline displacements and soil reactions from another design project containing the results of a previous (construction) phase. So the pipeline at the end of the previous phase (n) is transferred to the new phase (n+1) as a deformed structure kept in that deformed shape by a set of (imaginary) external forces R(n). The external (soil) supports specified in the new phase are attached to the pipeline at such a 'zero' deformation point, that the local R(n+1) force is generated only elastically by the new (soil) support system.This starting point determines the plastic soil deformation Vp. See soil displacement/reaction relation below.

The R(n)-axis is shifted over the distance Vp at the start of the new phase resulting in the R(n+1)-axis. If the new soil cannot deliver the reaction R(n) — i.e. R(n+1) < R(n) — the difference R(n) - R(n+1) is put on the pipeline as a 'disequilibrium' force.
So the displacements and forces at the start of the new phase are determined in such a way that there is equilibrium with the situation at the end of the previous phase.

In the new phase it is started from the origin of the new soil curves defined by the R(n+1)-displacement axes.
The plastic soil deformation Vp is treated as a kind of settlement occurring in the new phase. The complete loadings as exerted on the pipeline in the new phase have to be input to the new project and are placed on the pipeline structure by the program.

The facility may specifically be used for the analysis of a pipeline through a series of consecutive loadings (e.g. cyclic pressure and temperature loadings) taking into account soil hysteresis.
Or in consecutive phases the soil support system may change due to various stages of construction or natural behaviour of the surrounding soil (e.g. moving sand waves).

Design Function 5 should have been processed properly.

Phasing calculations cannot take place after a material non-linear calculation in the previous phase.

This option transfers the pipeline shape in the same way as is the case when the 'Continue'-option is applied, however, with the difference that in the new situation the pipeline is fixed in its transferred shape.

The external supports (soil included), specified in this database, are attached to the pipeline at their original 'zero'-deformation points.

In case the support system and the loadings and the pipeline properties are the same as in the database from which the deformation shape is taken, then the transferred shape will be the equilibrium state in the new situation too.

If the new local (soil)support can deliver only a force F(e) < F(i), then the remaining force is treated as reaction force from some imaginary external support and reported in the output table SUPREA. The facility may specifically be used for the analysis of a 'composed' pipeline structure for instance as they are sometimes used for hot medium transport. If it is a pipeline consisting of two concentric pipelines (e.g. an inner steel, medium pipeline and an outer plastic, jacket tube), than the outer pipe stressing can be calculated in a new database using the deformation of the original steel pipe. A similar situation may be analysed in case the composed line is a Steel-in-Steel pipeline. In that case an 'equivalent' pipeline is analysed and the result is transferred to two new databases, representing each pipeline separately.

Pre-Displacement calculations after material non-linear calculations in the Parent are not possible.