Page 201 - Pipelines and Risers
P. 201

174                                                               Chapter 11

        As  long as the  pullover  load  used  as input  to the  analysis  is  a  strong  function  of  the  gap
        height,  other variables  such  as span  length  and axial force in  the  10-inch flowline prior to
        impact, did not significantly affect the response.


        The pullover loads and durations, based on Eqs. (1 1.19) to (1 1.26) for a 10-inch flowline, are
        presented in Figure 11.7 below.
        Among others, the following parameters influence the pullover loads:
           Flexibility,  which  is  governed  by  pipeline  diameter,  wall-thickness,  span  length  and
           supporting condition.
           Geometrical effects, for instance due to the relative position and motion between the trawl
           gear and the pipeline, front geometrical shape of  trawl gear and the location where wire
           rope is attached. See Figure 11.8.



                                      Trawl pull-over loads
















                                        Span height
       Figure 11.7 Pullover loads and duration for different span heights.



















       Figure 11.8 Geometrical effect on pull-over loads for pipelines on seabed and on a free-spanning pipeline.
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