This paper presents a research about the monotonic and failure behaviours of bolted joints made of thin plates of S350GD and S355MC steels grades, which are used for rack structures. A full factorial ...test matrix was performed considering two joints configurations (1+1 and 4+4 double shear bolted joints), two material thicknesses (2 and 3mm), three coatings (“black steel”, zinc coating, zinc plus paint) and two preload levels (25%×70%Fu and 70%Fu). Tests were performed under static monotonic loading until failure. Slip tests were also performed according to the EN 1090-2 standard to evaluate joint slip factors for the three material surface conditions. In addition to the experimental tests, numerical simulation of static tests were performed using elastoplastic material behaviour, based on Mises yield theory and isotropic hardening identified with experimental tensile testing data. The models were able to reproduce conveniently the ultimate loads of the joints and failure modes, including clamping and friction effects.
Wind, as a sustainable and affordable energy source, represents a strong alternative to traditional energy sources. However, wind power is only one of the options, together with other renewable ...energy sources. Consequently, the core concerns for wind turbine manufacturers and operators are to increase its reliability and decrease costs, therefore enhancing commercial competitiveness. Among typical failure modes of wind turbines, fatigue is a common and critical source. Given the significance of fatigue reliability in wind turbine structural integrity, reliable probabilistic fatigue theories are necessary for design scheme optimization. By reducing the expenses on manufacturing, operation, and maintenance in reliability- and cost-optimal ways, the cost of energy can be significantly reduced. This study systematically reviews the state-of-the-art technology for fatigue reliability of wind turbines, and elaborates on the evolution of methodology in wind load uncertainty modelling. In addition, fatigue reliability assessment techniques on four typical components are summarized. Finally, discussions and conclusions are presented, intending to provide direct insights into future theoretical development and methodological innovation in this field.
•The state-of-the-art on fatigue reliability of wind turbines was systematically reviewed.•The method evolution in wind load uncertainty modeling is elaborated.•Fatigue reliability assessment techniques on four typical components are included.•Suggestions on aspects of future wind turbine fatigue reliability design and assessment are given.
Purpose
The purpose of this paper is to evaluate the fatigue process through the dynamic analysis of the global structural model and local static sub-modelling in a critical detail using the hot-spot ...stress approach. The detail was studied in three different positions at the “Alcácer do Sal” access viaduct, and the methodologies from the IIW and Eurocode EN 1993-1-9 were compared.
Design/methodology/approach
In this study, the fatigue life process based on the hot-spot stress approach was evaluated using a global dynamic analysis and a local sub-modelling based on a static analysis of welded connections in the “Alcácer do Sal” railway structure, Portugal, taking into consideration the recommendations from IIW and Eurocode EN 1993-1-9. The hot-spot stresses were calculated through the static analysis of the sub-model of the welded connection for each vibration mode with the aim to obtain the temporal stresses using the modal coordinates and modal stresses of the extrapolation points. The Ansys® and Matlab® softwares were used for the numerical analysis and the hot-spot stress calculations, respectively.
Findings
The proposed methodology/approach to obtain fatigue assessment is based on the modal analysis of the global structural model and local static sub-modelling. The modal analysis was used to extract the boundary conditions to be used in the local model to determine the temporal stresses of the extrapolation points. Based on the modal superposition method, the stresses as function of time were obtained for fatigue life evaluation of a critical detail by the hot-spot stress approach. The detail was studied in three different positions.
Originality/value
In the present study, a global-local fatigue methodology based on dynamic analysis of the global structural model and local static sub-modelling of the critical detail using the hot-spot stress approach is proposed. Herein, the modal analysis of the global structural model supported by the modal superposition method was used to obtain the matrix of modal coordinates. The static analysis of the local sub-model for each mode from the modal analysis of global structural model was done to estimate the hot-spot stresses. The fatigue damage calculation was based on S-N curve of the critical detail and rainflow method. The IIW recommendation proved to be more conservative compared to the proposed rules in the Eurocode EN 1993-1-9. The global-local modelling based on dynamic analysis is an important and effective tool for fatigue evaluation in welded joints.
•New methodology for fatigue damage screening of aging metallic railway bridges.•Integrated multiphase and multiscale fatigue assessment.•Advanced and well-organised calculation phase to implement ...fatigue local methods.•Improvements to standard and guidelines applicable to daily engineering tasks.•A real bridge is analysed, and the benefit of the multiphase methodology is shown.
This paper proposes an integrated methodology for fatigue assessment of existing metallic railway bridges, consisting of four sequential phases to be progressively implemented. Advanced fatigue life prediction tools based on local methods are suggested, aiming to analyse fatigue critical details, fully considering the local characteristics of the existing loading transfer mechanisms. A real case study is investigated using the new integrated methodology, demonstrating the relevance of efficient local fatigue analyses in this context, as well as the importance of data resulting from the multiphase fatigue assessment for the management authorities to optimise the maintenance of existing railway bridges.
A new formulation of a Logistic deterministic S-N curve is applied to fatigue data of metallic materials from ancient Portuguese riveted steel bridges. This formulation is based on a modified ...logistic relation that uses three parameters to fit the low-cycle- (LCF), finite-life- and high-cycle-fatigue (HCF) regions. This model is compared to the Kohout-Věchet fatigue model, which has a refined adjustment from very low-cycle fatigue (VLCF) to very high-cycle fatigue (VHCF). These models are also compared with other models, such as, Power law and fatigue-life curve from the ASTM E739 standard. The modelling performance of the S-N curves was made using the fatigue data considering the stress fatigue damage parameter for the materials from the Eiffel, Luiz I, Fão and Trezói riveted steel bridges. Using a qualitative methodology of graphical adjustment analysis and another quantitative using the mean square error, it was possible to evaluate the performance of the mean S-N curve formulation. The results showed that the formulation of the S-N curve using the Logistic equation applied to the metallic materials from the old bridges obtained superior performance to the analysed models, both in the estimation of fatigue behaviour in the low-cycle fatigue (LCF) region and in the lowest mean square error.
In Europe and North America there are a significant number of old riveted bridges still in operation, mainly due to economic reasons. Since these structures have been exposed to increasing traffic ...intensity, along their long operational lives, their damage levels need to be accurately assessed in order to decide about possible repairs. Fatigue failures are a concern for these riveted steel bridges since most of them were not originally designed taking into account fatigue. Also, there is a lack of comprehensive methodologies for the fatigue assessment of riveted bridges motivated by the limited knowledge on fatigue behavior of this type of construction as well as by a deficient understanding on fatigue behavior of the old materials (wrought-iron, puddle iron or old steels) and riveted connections. This paper presents an experimental study concerning the fatigue characterization of a puddle iron from the centenary Portuguese Fão bridge. Also, the fatigue behaviors of a type of riveted and bolted joints, made of the same puddle iron, are investigated. The effect of the clamping stress on bolted joints is investigated. Besides constant amplitude loading, variable amplitude fatigue loading is also investigated for the riveted joints in order to allow the critical assessment of the linear damage summation rule.
•A fatigue experimental program on puddle iron from an old bridge is carried out.•Strain-life and fatigue crack propagation data obtained for the material•Governing fatigue strength properties and high fatigue crack propagation rates•Riveted and bolted joints with distinct preloads fatigue tested•Variable amplitude S–N data of riveted joints showed consistency of Miner's rule.
In this paper, the failure probability of corroded pipelines made by X60 steel grade is evaluated. For this complex real engineering failure problem, the burst corroded performance function is ...developed using an M5Tree model based on calibration with real burst test database. In addition statistical analysis of ILI-report data is conducted for best modeling of corrosion defects geometries (i.e. defects length and depth) based on Anderson-Darling statistic where different PDFs (i.e. Normal, Lognormal, Frechet, Gumbel, Weibull) were tested. Moreover, the effect of defects geometries on the failure probability of the case-studies were investigated for various operating regimes. Then the influence of distributions on the reliability analysis were also illustrated. Results indicated that increases in defects depth are strongly reduced the safety levels of this problem, where miss-selection of defects distributions could lead to conservatives results.
•A Metamodel-based M5 tree algorithm is developed to simulate the burst pressure of X60 corroded pipeline.•Statistical analysis of real inspection data is carried out for the X60 gas pipeline.•The reliability analysis using hybrid model of M5Tree and MCS is used to evaluate the safe levels of corroded X60 steel.•The influence of different distributions for corrosion defect geometries on the failure probabilities is demonstrated.•The distribution information of corrosion defects are an important statistical parameter.
A procedure for estimation of probabilistic fatigue
S–N curves for notched structural components is described. Plain material strain–life data is used to identify a statistical Weibull strain–life ...model and, using an adequate elastoplastic analysis, material strain–life probabilistic curves are converted into probabilistic stress–life curves of the structural component. The performance of the proposed model is illustrated by a practical example of a riveted shear splice, from a Portuguese railway bridge, for which experimental resistance data is available. A simplified elastoplastic analysis based on the Neuber and the Glinka rules are used, supported by the results of an elastic finite element analysis of the riveted connection. The paper demonstrates the success of the proposed probabilistic model since it correlates satisfactorily with the available experimental data for the riveted connection. The achieved results confirm the proposed probabilistic model as well suited for notched structural components with a whole fatigue life dominated by crack initiation.
This paper presents an integrated fatigue analysis methodology for existing metallic railway bridges, progressively implementing global to local fatigue assessment methods, each requiring a different ...level of calculation detail. The former are adopted mainly for screening the fatigue-critical connections using nominal stress-based SN curves, which often oversimplify the characteristics of the loading transference mechanisms, relying on high safety factors. On the other hand, the latter methods are innovatively proposed to refine the fatigue evaluation of connections that present unsatisfactory remaining fatigue life according to the global assessment. A multiscale modelling is adopted, leveraged by modal superposition concepts for structural analysis, which allows efficiently bridging the difference between the scale related to the overall size of the bridge and the local one associated with the fatigue damage developed at hot-spots (e.g., rivet holes). A real case study is investigated to demonstrate the added value of the innovative and efficient progressive fatigue assessment of details that would otherwise not be accurately analysed, taking into account the local characteristics of the response, if only common global procedures were implemented.
•Innovative fatigue analysis methodology to analyse existing metallic railway bridges.•Local fatigue approaches to overcome limitations of the nominal stress method.•Two generalizable calculation routes to investigate multiple geometries.•A real bridge is analysed, demonstrating the value of the multiphase methodology.•Relevant improvements in the fatigue safety check are clearly obtained.
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