For complex offshore problems, SHEAR7 is typically used in conjunction with an offshore systems modelling tool such as Orcaflex, Flexcom or Abaqus. SHEAR7 is a vortex-induced vibration prediction program that requires a structural dynamic input. For simple structures, such as linearly varying tensioned cylinders, SHEAR7 has its own internal capability to generate structural dynamics input. However most offshore structures have a degree of sophistication that requires the capability of a dedicated line dynamics program. Such sophistications can include stress joints, flex joints, clumped masses, connection details where fatigue is important, piggybacked systems. In situations such as these, the most appropriate way to evaluate VIV is by generating the structural model in a third party package and importing into SHEAR7.
The following details how SHEAR7 is integrated into some of these packages and the associated functionality with each third party software.
Orcaflex by Orcina
Orcaflex latest release v9.5 (October 2011) supports SHEAR7 v4.6, v4.5, v4.4 & v4.3. Orcaflex are currently working on integration with SHEAR7 v4.7.
Shear7 related features:
- can create input .dat files for SHEAR7
- can collate the output of multiple SHEAR7 load cases and sum fatigue damage.
- can use Orcaflex's detailed structural modelling capability and export the structural models (modeshape and natural frequency files “common.mds”) to SHEAR7
- can fully batch run SHEAR7 in the background, including pre and post processing as well as executing SHEAR7.
- OrcaFlex and SHEAR7 can produce a coupled structural/VIV solution that incorporates drag amplification due to VIV.
Flexcom and DeepRiser by MCS
Flexcom (Version 8.1) and DeepRiser (Version 3.1) by MCS support SHEAR7 v4.6.
SHEAR7 related features:
- The modal analysis modules in both programs can write a structural model file for subsequent reading by SHEAR7
- Flexcom and DeepRiser can read drag amplification factors from SHEAR7 output in analyses including current loading; this is typically of most importance in interference or clearance analyses, particularly in the context of wake interference where the effect of VIV- enhanced drag on one or both of the upstream and downstream structures
- Flexcom provides a further level of sophistication for the downstream structure analysis, in that users can tell Flexcom to repeatedly recalculate the modal solution for the downstream structure and to rerun SHEAR7 based on this solution as the wake interference analysis proceeds; in this way the effect of the actual current velocity ‘seen’ by that structure and the resulting tension distribution in the downstream structure can be accurately monitored
DeepLines is a riser analysis package distributed by Principia, developed at IFP. Deeplines can create .mds files for SHEAR7 from DeepLines modal analysis.
The latest release of Deeplies is Version 4.5 and DeepLines the planned release for Version 5.0 is early 2013. DeepLines are planning potential further integration with SHEAR7 in future versions.