Page 125 - Pipelines and Risers

98 Chapter 7

Impact loads.

This chapter is based on a M.Sc. thesis, Ose (1998), supervised by the author and the work
has been influenced by the papers presented in the conferences, Nystrom et al. (1997), TQmes
et al. (1998) and Kristiansen et al. (1998).

7.2 Description of the Finite Element Model
In order to make a model like described above, some investigation of the problem had to be
performed. This section deals with this process and describes some of the decisions that were
made and problems that were to be solved during the work with this thesis.

7.2.1 Static Analysis Problems
Installation
Since the model may be used to analyze a pipeline situated on the seabed, it had to include
some sort of installation process in order to find the pipeline configuration when placed on the
three-dimensional seabed. This configuration would then serve as an initial configuration for
the subsequent parts of the analysis.

Primarily it was not the behavior of the pipeline during the installation process that may be
investigated. The important thing was to make sure that the lay-tension and lay-angle from the
installation process was represented in such a way that the build-up of residual forces in the
pipeline, due to friction when the pipeline lands on the seabed, was accounted for.

Figure 7.1 The established finite-element model before and under instauation.