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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 1 Accidental Explosions Design criteria
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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 2 Design Accidental Actions and associated performance criteria determined by Quantified Risk assessment (QRA) Main safety functions shall not be impaired –usability of escape-ways –integrity of shelter areas –global load bearing capacity Integrity normally for et least 1 hour NORSOK STANDARD DESIGN AGAINST ACCIDENTAL LOADS
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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 3 CharacteristicDesign Accidental Actions corresponding to annual probability of occurrence of ~10 -4 per installation Overall frequency 5·10 -4 all accidents often used impairment frequency limit NORSOK STANDARD Risk acceptance criteria
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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 4 Global collapse of structure Rupture or unacceptable deformation of explosion barriers Deformation of decks leading to unacceptable damage to equipment Deformation of HC equipment leading to unacceptable escalation Unacceptable damage to equipment of critical systems NORSOK STANDARD Dimensioning loads evaluated wrt unacceptable consequences/limit states
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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 5 Pressure Time Area distribution NORSOK STANDARD (S-001) Explosion load to be described wrt: p t p max > 5bar
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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 6 Pressure - Impulse surfaces Average pressure over predefined area’ Overrpressure drag CFD analyses (e.g. FLACS) to be used for probabilistic analysis NORSOK STANDARD (Z-013) Explosion load to be described wrt: t
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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 7 SDOF or NLFEA Dynamics and deformation characteristics important’ Explosion load: Triangular time dependent overpressure/drag Direct linearization of overpressure-time curve from CFD simulation CFD analyses (e.g. FLACS) to be used for probabilistic analysis NORSOK STANDARD (Z-013) Principles of analysis t
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J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS 15.04.2008 8 Explosion pressure versus area Not explicitly stated High pressure for local design of plates Low pressure for systems Analogy with ice?
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