SIMPLIFIED FATIGUE DESIGN ASSESSMENT (FDA) PROCEDURE FOR SLOTS/CUTOUTS BASED ON A STRESS CONCENTRATION FACTOR (SCF) APPROACH

摘要

The Fatigue Design Assessment (FDA) procedure is a part of ShipRight design, construction and lifetime ship care procedures developed by Lloyds Register. The work presented in this paper is on the application of a Stress Concentration Factor (SCF) approach to the FDA procedure to develop an effective and user friendly tool for the assessment of fatigue performance of cut-outs in transverse web frames for longitudinal stiffeners. Investigation of hull damage statistics has identified that fatigue cracking in way of cut-outs and end brackets of longitudinal stiffeners affects a reasonable proportion of ships in service. This can become an ongoing 'through life' maintenance issue as defects can re-occur if the design of the structural detail has insufficient fatigue performance. A spectral fatigue assessment of this structural detail has traditionally been based on localised mesh refinement applied to a global finite element (FE) model and hydrodynamic calculated using first principle methods. These traditional methods are time, resource and labour intensive processes and therefore limited in its application. The SCF approach developed offers a faster and simpler method for the determination of hotspot stresses for standardised cut-out details.