DNV-RP-F105

Covers — assessment of free-spanning submarine pipelines: span screening, vortex-induced vibration (VIV) response to current/wave flow, and fatigue-life assessment to set allowable span lengths.

Does NOT cover (exclusions) — the pipeline design basis → DNV-ST-F101; on-bottom stability → DNV-RP-F109; global buckling → DNV-RP-F110.

F105 handles the free-span VIV/fatigue problem within the DNV subsea framework.

F105 provides assessment methods for free spans:

• Span Screening — identify spans requiring detailed VIV assessment.
• VIV Response — in-line and cross-flow vibration from current and wave loading.
• Fatigue — accumulated fatigue damage and allowable span length/life.

DNV-RP-F105 assesses free-spanning submarine pipelines, where a line crosses uneven seabed and hangs unsupported. Current and wave flow past the suspended span can excite vortex-induced vibration (VIV), which accumulates fatigue damage. F105 screens spans, models the VIV response, and evaluates fatigue life to set allowable span lengths, all within the DNV-ST-F101 design framework.

Engineering Note: Long free spans that pass a static-strength check can still fail by VIV fatigue — always assess dynamic response, and consider span-correction (rock dumping, supports) where fatigue life is inadequate.