Page 186 - Pipelines and Risers

Trawl Impact, Pullover and Hooking Loads 159

Perform static analysis.
Denting face includes effect
of bawl board geometry at
impact point and possible
coating.

Farce A

Establish force-dmt

Trawl board stiffness

Perform dynamic analysis.

3 global bending stiffness included
by use of beam elements. Soil stiffiess
modelled with discrete pnnd springs
(both vertical and lateral).
I

Force A
Calculate impact energy
absorbed by the pipe shell,
based on Ihe maximum
------ impacting force and the
established force-dent
relationship.
tine

Figure 11.2 Scheme for Simulation of Impact Between Trawl Board and Pipeline (STATOIL, 1996).
The energy absorption process will be simulated applying dynamic global pipe model.
Nonlinear beam elements with pipe section can be used for the simulation of pipeline global
behavior. The indentation curve for steel pipe and insulation coating are modeled using non-
linear spring elements capable of accommodating compression forces only. The dynamic
analysis is carried out assuming the steel and added masses of the trawl board with an initial
velocity. The finite element modeling will be similar to that described in Chapter 7. The