Introduction
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The Roche method makes it possible to evaluate a non-linear response from the results of linear calculations to which abatement coefficients are applied. The objective of this approach is to significantly reduce calculation times compared to a classical non-linear resolution approach for seismic calculations applied to pipe lines.

The abatement coefficients are calculated using spring effect factors. These factors represent an estimate of the difference between the calculated linear solution and the nonlinear solution sought.

The determination of moment reduction coefficients resulting from linear elastic analyses of flexibility of pipe lines follows the following specifications:


* chapters RB 3651.1132 and RB 3651.1142 from RCC - MRx (post-spectral Roche method),


* transitory method (uncodified post-transitory Roche method).

The determination of the equivalent stress, taking into account the moments down and the moments not knocked down, corresponds to all the loads in question.

These reduction coefficients are applicable to the secondary part of the moments, which is relaxing, the primary part being non-relaxable because of the spring effect.

The geometries concerned are:


* pipes with a constant diameter and a variable diameter (reductions),


* contiguous lines and branched lines.


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