J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS Accidental Explosions Design criteria

J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS  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

J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS  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

J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS  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

J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS  Pressure  Time  Area distribution NORSOK STANDARD (S-001) Explosion load to be described wrt: p t p max > 5bar

J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS  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

J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS  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

J. Amdahl,, NTNU Dept, Marine Technology Beregning av ulykkeslaster for offshore stålkonstruksjoner – NFS Explosion pressure versus area  Not explicitly stated  High pressure for local design of plates  Low pressure for systems  Analogy with ice?