Full text
| |
| Author(s): |
Alfredo Gay Neto
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Escola Politécnica (EP/BC) |
| Defense date: | 2012-08-27 |
| Examining board members: |
Clóvis de Arruda Martins;
José Augusto Penteado Aranha;
Breno Pinheiro Jacob;
Paulo de Mattos Pimenta;
Melquisedec Francisco dos Santos
|
| Advisor: | Clóvis de Arruda Martins |
| Abstract | |
Catenary risers can show a very low tension level close to the seabed. This can occur in some launching conditions, in which the structure can be almost vertical. When dealing with flexible pipes or umbilical cables, their internal composition includes the helical tension armors. These can induce an axial rotation to the riser when it is tensioned. If this movement is constrained, a torsion moment will act upon the structure. The low tension level present in the catenary configuration combined with the torsion moment that occurs during the riser launching can lead to a structural instability, resulting in a loop formation. This is undesirable since, if the loop is present, depending on the loads applied to the riser it is possible that it turns into a kink, causing damage. The present work analyzes the loop formation conditions in catenary riser. For that, stability criteria were applied to a finite element model that takes into account the geometric nonlinearities and also the contact between the riser and the seabed. A kinematically-exact beam formulation was adopted, dealing correctly with the large rotations that are imposed to the riser, in order to induce the torsion moment. It is showed that an analytical expression based on Greenhills formula can predict the phenomenon with a good agreement with numerical results, even including phenomena as frictional unilateral contact and sea currents. Furthermore, a parametric analysis was done to predict the loop formation to some catenary geometries, in order to generalize the obtained conclusions. (AU) | |
| FAPESP's process: | 06/06277-0 - Linear and nonlinear dynamic analysis of submerged cables |
| Grantee: | Alfredo Gay Neto |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |