One of the most important problems in deep water pipelaying consists in the analysis of the configuration at the installation stage. In fact it is well known from practical experience that most pipelines are likely to encounter their highest stresses during the laying process. From a mechanical point of view the problem is one of large displacements and is furthermore complicated by the fact that the length of the suspended span is a priori unknown, as well as some boundary conditions at the seabed touchdown point and at the connection to the laybarge. In the case of deep waters, additional problems become significant. In fact the curvature of the pipeline during the installation process tends to cause the ovalisation of the cross-section according to the well known von Kàrmàn effect and in turn the consequent reduction of the bending stiffness influences the pipeline axis configuration. Thus the rod equilibrium problem becomes non-linear also in the bending moment-curvature relationship even for a linear elastic material. The present paper proposes an analytical approach for the calculation of the elastic deflection of submerged pipelines laid with a stinger which takes into account the overall effects of the ovalisation of the cross-section. The analysis is performed by means of a singular perturbation technique and the analytical solution obtained turns out to present some advantages over the finite element method. A practical example is discussed and a comparison with the results obtained by means of a well-known commercial finite element package (ABAQUS v. 5.7) is performed.
Analysis of submerged pipelines during installation: influence of the ovalization
MALLARDO, Vincenzo
1999
Abstract
One of the most important problems in deep water pipelaying consists in the analysis of the configuration at the installation stage. In fact it is well known from practical experience that most pipelines are likely to encounter their highest stresses during the laying process. From a mechanical point of view the problem is one of large displacements and is furthermore complicated by the fact that the length of the suspended span is a priori unknown, as well as some boundary conditions at the seabed touchdown point and at the connection to the laybarge. In the case of deep waters, additional problems become significant. In fact the curvature of the pipeline during the installation process tends to cause the ovalisation of the cross-section according to the well known von Kàrmàn effect and in turn the consequent reduction of the bending stiffness influences the pipeline axis configuration. Thus the rod equilibrium problem becomes non-linear also in the bending moment-curvature relationship even for a linear elastic material. The present paper proposes an analytical approach for the calculation of the elastic deflection of submerged pipelines laid with a stinger which takes into account the overall effects of the ovalisation of the cross-section. The analysis is performed by means of a singular perturbation technique and the analytical solution obtained turns out to present some advantages over the finite element method. A practical example is discussed and a comparison with the results obtained by means of a well-known commercial finite element package (ABAQUS v. 5.7) is performed.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
