1. Seafloor contact specification

This data group must be given for Arbitrary Systems AR-sytems with IBTANG = 3.

1.1. Data group identifier, one input line

SEAFloor CONTact SPECification

1.2. Seafloor contact specification

NSPEC

  • NSPEC: integer > 0: Number of input lines to be given with seafloor contact specification

NSPEC input lines

CMPTYP-ID LINE-ID ISEG1 ISEG2 … ISEGn

  • CMPTYP-ID: character(8): Reference to a seafloor contact component identifier. Must be of type SPRI or SOIL.

  • LINE-ID: character(8): Reference to a line identifier

  • ISEG1: integer >= 0, default: 0: Segment for which seafloor contact of type CMPTYP-ID is possible.

    • ISEG1 = 0: Seafloor contact is possible for all segments in line LINE-ID

    • ISEG1 > 0: First segment for which seafloor contact is possible.

  • ISEG2: integer != 0: Segment for which seafloor contact of type CMPTYP-ID is possible.

    • ISEG2 > 0: Second segment for which seafloor contact is possible.

    • ISEG2 < 0: Seafloor contact is possible for all segments from ISEG1 to ABS(ISEG2).

  • ISEGn: integer !=0: Last segment for which seafloor contact of type CMPTYP-ID is possible.

    • ISEGn > 0: Last segment for which seafloor contact is possible.

    • ISEGn < 0: Seafloor contact is possible for all segments from the previous specified segment to ABS(ISEGn).

Pairs of a positive and a negative segment number may be given anywhere in the sequence.

Note that a segment may only have one seafloor contact.

2. Elastic contact surface

This data group is optional and is available as additional information for Arbitrary Systems only. It enables the user to model contact effects between lines. For normal riser systems this data group should not be considered.

The main intention of this data group is to enable modelling of pipelines during laying operations. This includes contact forces between the pipe and rollers on the lay barge/stinger and applied tension from a tensioner.

Contact between roller and pipe is modelled by a bi-linear or non-linear spring and a bi-linear dash pot damper. The contact force acts normal to the pipe and the roller. It is treated as a discrete element load acting on the pipe, while the contact load acting on the roller is transferred as a nodal force to the stinger. The last includes possible torsional moment.

The term contact surface is introduced to cover stinger modelling. The stinger may be fixed or hinged to the vessel. Generally it is curved and may consist of a rigid part following the vessel motions and a flexible part.

The term contact point is defined as the location of rollers or tensioner on the stinger.

um ii fig41
Figure 1. Elastic contact surface

2.1. Contact surface modelling

A complete model of an elastic contact surface includes the following information:

  • Number of lines describing the surface The surface may consist of several adjacent lines. By introducing several adjacent lines it is possible to model a contact surface which has a curved stress-free initial configuration. In addition boundary conditions for the super-nodes at the line intersections can be specified. This is necessary to model prescribed displacements due to vessel motions.

  • Type and location of contact points Contact points can be of roller and/or tensioner type and have to be located at ends of line segments.

  • Identification of lines which may experience contact with the contact surface. The line identification is used to limit the number of elements that have to be checked for contact during program execution.

Supplementary information is specified in the following data groups: