Recent Developments in Fatigue Assessment of Ships and Offshore Structures

A review is provided of various approaches that have been adopted recently to assess the fatigue of ships and offshore structures.The relevant fatigue loading is reviewed first,focusing on the successive loading and unloading of the cargo and the transient loadings.The factors influencing fatigue strength are discussed,including the geometrical parameters,material,residual stress,and ones related to the environment.Different approaches for fatigue analyses of seam-welded joints are covered,i.e.,the structural stress or strain approach,the notch stress or strain approach,notch intensity approach,and the crack propagation approach.

Fatigue Reliability Assessment of Correlated Welded Web-frame Joints

The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using the 20-node solid elements is generated. A linear elastic finite element analysis was performed, hotspot stresses in a web-frame joint were analyzed and fatigue damage was quantified employing the S-N approach. The statistical descriptors of the fatigue life of a non-correlated web-frame joint containing several critical hotspots were estimated. The fatigue reliability of a web-frame joint wasmodeled as a series system of correlated components using the Ditlevsen bounds. The fatigue reliability of the entire welded structure with multiple web-frame joints, modeled as a parallel system of non-correlated web-frame joints was also calculated.

Review on Artificial Intelligence-aided Life Extension Assessment of Offshore Wind Support Structures

The primary objective of the present literature review is to provide a constructive and systematical discussion based on the relevant development,unsolved issues,gaps,and misconceptions in the literature regarding the fields of study that are building blocks of artificial intelligence-aided life extension assessment for offshore wind turbine support structures.The present review aims to set up the needed guidelines to develop a multi-disciplinary framework for life extension management and certification of the support structures for offshore wind turbines using artificial intelligence.The main focus of the literature review centres around the intelligent risk-based life extension management of offshore wind turbine support structures.In this regard,big data analytics,advanced signal processing techniques,supervised and unsupervised machine learning methods are discussed within the structural health monitoring and condition-based maintenance planning,the development of digital twins.Furthermore,the present review discusses the critical failure mechanisms affecting the structural condition,such as high-cycle fatigue,low-cycle fatigue,fracture,ultimate strength,and corrosion,considering deterministic and probabilistic approaches.

Fatigue Reliability of Deck Structures Subjected to Correlated Crack Growth

The objective of this work is to analyse fatigue reliability of deck structures subjected to correlated crack growth.The stress intensity factors of the correlated cracks are obtained by finite element analysis and based on which the geometry correction functions are derived.The Monte Carlo simulations are applied to predict the statistical descriptors of correlated cracks based on the Paris-Erdogan equation.A probabilistic model of crack growth as a function of time is used to analyse the fatigue reliability of deck structures accounting for the crack propagation correlation.A deck structure is modelled as a series system of stiffened panels,where a stiffened panel is regarded as a parallel system composed of plates and are longitudinal.It has been proven that the method developed here can be conveniently applied to perform the fatigue reliability assessment of structures subjected to correlated crack growth.

Numerical Analysis of Stress Concentration in Non-uniformly Corroded Small-Scale Specimens

A numerical evaluation of stress concentrations of corroded plate surfaces of small-scale corroded steel specimens is compared with the experimentally estimated ones.Eleven specimens were cut from a steel box girder,which was initially corroded in real seawater conditions.The surface of all corroded specimens was analysed applying photogrammetry techniques,and a statistical description of an idealised corroded surface of each specimen was established.Fatigue lives of specimens are determined from the fatigue tests.Based on experimentally obtained fatigue lives,the stress concentration factors are calculated concerning the ideally smooth specimens.The correlation between the statistical parameters of the corroded specimen surfaces and the estimated stress concentration factors is analysed.Idealised corroded surfaces,converted in graphical format,are then used for the finite element modelling in ABAQUS software,and stress concentration factors are estimated from the finite element results.A convergence study is performed to determine the appropriate finite element mesh density.Comparison between experimentally obtained and numerically estimated stress concentration factors is performed as well as correlation analysis between actual and finite element predicted crack locations.

Review of Ultimate Strength Assessment of Ageing and Damaged Ship Structures

The objective of this work is to provide an overview of the ultimate strength assessment of ageing and damaged ship structures in the last decades.Particular attention is paid to the ultimate strength of plates,stiffened panels,box girders,and entire ship hull structures subjected to corrosion degradation,fatigue cracking,and mechanical damage caused by accidental loading or impact.A discussion on the effect of the cyclic load on the plate rigidity,re-yielding,and ultimate load capacity on the ship hull girder is also part of the present study.Finally,some conclusions and discussions about potential future work are provided,identifying that more studies about the impact of corrosion degradation on the structural behaviour of the stiffened panels and the overall hull girders are needed.Studies related to the dynamic collapse behaviour of corroded and damaged ship structures under time-variant load also requires additional attention.