Abstract
AbstractFatigue is a governing design limit state for marine structures. Welded joints are important in that respect. The weld notch stress (intensity) distributions contain essential information and formulations have been established to obtain a total stress fatigue damage criterion and corresponding fatigue resistance curve; a total stress concept. However, the involved weld load carrying stress model does not provide the required estimates and trends for varying geometry dimensions and loading & response combinations. A new one has been developed and performance evaluation for T‐joints and cruciform joints in steel marine structures shows that in comparison with the nominal stress, hot spot structural stress and effective notch stress concept based results up to 50% more accurate fatigue design life time estimates can be obtained. Taking advantage of the weld notch stress formulations, the effective notch stress concept performance has improved adopting a stress‐averaged criterion rather than a fictitious notch radius‐based one.
Highlights
Marine structures active in inland, coastal, offshore and deep-sea waters are exposed to cyclic mechanical loading, both environment and service induced
Since marine structures are traditionally structural member assemblies in stiffened panel, truss, or frame set-up, particular attention is paid to arc-welded joints typically
The arc-welded double-sided T-joint is a characteristic one in marine structures, showing non-symmetry with respect to half the base plate thickness
Summary
Marine structures active in inland, coastal, offshore and deep-sea waters are exposed to cyclic mechanical loading, both environment (wind and waves) and service (operations and machinery) induced. The marine structural stiffness distribution is predominantly orthotropic (stiffened panels) or member orientation defined (trusses and frames), meaning the uniaxial crack opening mode-I component dominates the welded joint fatigue damage process. Double-sided T-joint and double-sided cruciform joint fatigue resistance data from literature will be used to investigate the total stress concept performance in comparison with the nominal stress concept hot spot structural stress concept and effective notch stress concept results. To calculate the (cyclic) mechanical loading induced global marine structural response, a relatively coarse meshed shell/plate finite element (FE) model is typically sufficient to estimate the far-field stress.[12,13] The local weld geometry is not included, meaning that corresponding notch information is missing. Turning an intact geometry parameter into a cracked geometry equivalent, the acquired damage criterion takes the complete distribution into account.[7,11]
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