The Experts below are selected from a list of 5610 Experts worldwide ranked by ideXlab platform
Wei Zhang - One of the best experts on this subject based on the ideXlab platform.
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Long-term Fatigue Damage Assessment for a floating offshore wind turbine under realistic environmental conditions
Renewable Energy, 2020Co-Authors: Wei ZhangAbstract:Abstract Offshore wind energy has gained widespread attention and experienced a rapid development due to the significantly increasing demand for renewable energy over the past few years. Currently, the development of offshore floating wind turbines attracts lots of attention to harvest more energy from a sustained higher speed of offshore wind away from the coastline. With stronger cyclic wind and wave loadings, the floating wind turbine could possibly experience severe Fatigue Damages at certain critical locations, which might lead to a catastrophic failure. Evaluating accumulated Fatigue Damage for a floating wind turbine during its entire lifetime, therefore, becomes essential and urgent. As demonstrated in the codes, specifications, or design practices, Fatigue Assessments require massive computational costs and pose challenges to numerical simulations since lots of dynamic analyses under different environmental scenarios need to be performed. To reduce the calculation cost for this time-consuming process while maintaining high accuracy, a probabilistic long-term Fatigue Damage Assessment approach is proposed in the present study by implementing a C-vine copula model and a surrogate model. The C-vine copula model provides a multivariate dependency description for the on-site wind and wave-related environmental parameters. Two surrogate models, including the Kriging model and the artificial neural network (ANN), are implemented to efficiently predict the short-term Fatigue Damages at critical locations of the floating wind turbine. The proposed long-term Fatigue Damage Assessment framework is accurate and suitable for evaluating structural long-term Fatigue Damages accumulated in a real environment especially when effects from more environmental parameters are to be considered. Based on surrogate models, sensitivity analyses are carried out to investigate the relative significance of each environmental parameter on short-term Fatigue Damages. In addition, uncertainties from short-term Fatigue Damages are also incorporated into the probabilistic Fatigue evaluation framework to assess the accumulated long-term Fatigue Damages for a spar type floating wind turbine.
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Fatigue Damage Assessment of orthotropic steel deck using dynamic bayesian networks
International Journal of Fatigue, 2019Co-Authors: Wei Zhang, X LiAbstract:Abstract Current health monitoring of orthotropic steel deck (OSD) subjected to Fatigue Damage mainly relies on deterministic physical models and the field measurements through inspections and monitoring. Nevertheless, various aleatory (random) and epistemic (lack of knowledge) uncertainties exist due to empirical justifications, model simplifications, inaccurate statistics of model parameter, measurement error, etc. The present study proposes a probabilistic model for Fatigue Damage diagnosis and prognosis of an OSD through integrating the physical model with field inspections while accounting for the associated uncertainties, using the dynamic Bayesian network (DBN). The DBN is suitable for representation and reasoning under uncertainty in various fields. The proposed framework aims to fulfill two interdependent tasks (1) diagnosis: track the time-dependent variable (i.e., the crack growth) and calibrate the time-independent variables (i.e., the geometric parameters and the multiplier for the crack shape factor); and (2) prognosis: predict the crack growth in the future. The particle filter (PF) is employed as the Bayesian inference algorithm for the established non-Gaussian DBN composed of continuous variables of various distribution types, as well as nonlinear conditional dependence between them. In addition, a Gaussian process (GP) surrogate model is established to relate the output stress response of the physical model (OSD) under the input truck load and model parameters, which is further implemented as the conditional probability distribution (CPD) in the DBN model. Finally, the proposed framework is illustrated by a numerical example of Fatigue crack growth on the OSD subjected to truck load.
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Nonlinear Fatigue Damage Assessment of existing bridges considering progressively deteriorated road conditions
Engineering Structures, 2013Co-Authors: Wei Zhang, C.s. Cai, Fang PanAbstract:Variable stress ranges from dynamic vehicle loads can induce Fatigue Damage accumulations at certain bridge components and accelerate the road surface deterioration in bridges’ life cycle. The interactions of the road surface deterioration and random dynamic vehicle loads might accelerate the Fatigue Damage accumulations and lead to serious Fatigue failures when such Damages increase to a certain limit. This paper presents a nonlinear Fatigue Damage Assessment approach for existing bridges to include the progressive road surface deterioration and the nonlinear effects of the Fatigue Damage accumulation due to random dynamic vehicle loads. In each stress block for Fatigue Damage calculation, vehicle types and speeds and road profiles for a certain road roughness coefficient are randomly generated for the vehicle–bridge dynamic system. Fatigue Damage and cumulative probability of Fatigue failures due to these variable stress ranges are calculated based on a nonlinear cumulative Fatigue Damage rule. Nevertheless, the vehicle types, numbers, and weights are used to predict the road roughness coefficient for the next stress block. The predicted Fatigue Damages are different when using the linear and nonlinear Fatigue Damage rules. The effects from the random variables in the vehicle–bridge dynamic system are discussed, as well.
Hiroshi Masuya - One of the best experts on this subject based on the ideXlab platform.
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The impact vibration-based Fatigue Damage Assessment of steel and steel fiber reinforced concrete composite girder
International Journal of Steel Structures, 2016Co-Authors: Saiji Fukada, Hiroshi MasuyaAbstract:The steel-concrete composite girder has been usually applied in the civil structures. The current Fatigue Damage Assessment on the composite girder, especially the negative bending region, mainly bases on the crack observation and deflection measurement. It is not stable sometimes, thus the impact vibration-based Fatigue Damage Assessment was considered instead. A 3.3m steel-steel fiber reinforced concrete (SFRC) composite girder was designed and tested. The Fatigue load, the impact load, and the static load were applied in the test. It showed that the local Fatigue Damage reflected by the tensile SFRC cracks may not be easily evaluated through observing the global mechanical change. However, the vibration modal parameters such as the vibration frequency, vibration mode, damping ratio might be useful for this. In particular, the vibration mode variation, which can be expressed by the Modal Assurance Criterion (MAC) value, may reflect the local Fatigue Damage on the composite girder.
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The Vibration Based Fatigue Damage Assessment of Steel and Steel Fiber Reinforced Concrete (SFRC) Composite Girder
MATEC Web of Conferences, 2015Co-Authors: Saiji Fukada, Hiroshi MasuyaAbstract:The steel-concrete composite girder has been usually applied in the bridge and building structures, mostly consisting of concrete slab, steel girder, and shear connector. The current Fatigue Damage Assessment for the composite girder is largely based on the strain values and concrete crack features, which is time consuming and not stable. Hence the vibration-based Fatigue Damage Assessment has been considered in this study. In detail, a steel-steel fiber reinforced concrete (SFRC) composite girder was tested. The steel fiber reinforced concrete is usually considered for dealing with the concrete cracks in engineering practice. The composite girder was 3.3m long and 0.45m high. The Fatigue load and impact excitation were applied on the specimen sequentially. According to the test results, the concrete crack development and global stiffness degradation during the Fatigue test were relatively slow due to the favourable performance of SFRC in tension. But on the other hand, the vibration features varied significantly during the Fatigue Damage development. Generally, it confirmed the feasibility of executing Fatigue Damage Assessment of composite bridge based on vibration method.
Yordan Garbatov - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Damage Assessment of fixed offshore wind turbine tripod support structures
Engineering Structures, 2015Co-Authors: B. Yeter, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract The objective of this work is to carry out a Fatigue Damage Assessment of a fixed offshore wind turbine support structure due to combined wave and wind – induced loading. Considering the operational mode of the wind turbine 3 loading conditions are identified and for each loading condition 4 critical regions located in different zones of the supporting structure are studied. The stress transfer function is obtained by carrying out dynamic finite element analysis in the frequency domain. A wave scatter diagram of the North Atlantic is used in order to account for the environmental effects. The stress transfer function is formulated such that a sufficient number of frequencies can be used in the Inverse Fast Fourier Transform with random phase angles in order to obtain the stress time histories. An up-to-date rainflow cycle counting method is adopted to count the total number of cycles related to stress range bins. The S–N approach is employed to estimate Fatigue Damage.
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spectral Fatigue Damage Assessment of tanker deck structural detail subjected to time dependent corrosion
International Journal of Fatigue, 2013Co-Authors: Tran K Nguyen, Yordan Garbatov, Guedes C SoaresAbstract:Abstract The paper presents a spectral Fatigue Damage analysis of a double hull tanker structural detail accounting for corrosion wastage over time. The cyclic load of the wave-induced vertical bending moment, analysis using a strip theory on the frequency domain, is considered for two loading conditions. The influence of sea environment parameters and operational profiles including the use of different scatter diagrams, and wave variance spectra have been analyzed. The effect on the time-dependent cumulative Fatigue Damage as a function of corrosion deterioration is calculated.
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Fatigue Damage Assessment of corroded oil tanker details based on global and local stress approaches
International Journal of Fatigue, 2012Co-Authors: K. Tran Nguyen, Yordan Garbatov, C. Guedes SoaresAbstract:Abstract Fatigue Damage Assessment of double hull oil tanker structural details is performed, based on global and local structural finite element models. The wave-induced vertical and horizontal bending moments, as well as local pressure loads are accounted for in the Fatigue Damage calculations. Local stress analyses are considered based on the notch stress approach. Time-dependent stresses as a function of corrosion deterioration are analyzed based on nonlinear corrosion wastage during the design life of ship. The effective notch stress approach is applied for analyzing the stress distributions and the Fatigue Damage of the welded joint at two hotspots. The hotspots are located between the flat bar stiffener of a transverse web frame and the flange of a longitudinal stiffener at the side shell of a tanker ship hull. The details under consideration are modeled separately in a fine mesh employing the sub model techniques. Finally the Fatigue Damage Assessment accounting for corrosion deterioration of the considered hotspots is analyzed.
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Fatigue Damage Assessment of a Converted FPSO Hull
2004Co-Authors: Stipe Tomašević, Yordan Garbatov, Carlos Guedes SoaresAbstract:This work deals with the Fatigue Assessment of a FPSO converted from a tanker based on a finite element analysis. The finite element calculations are performed on two levels including global and local detailed analysis. Due to the difference of sea state conditions and wide of operations of the initial and converted vessels two different models are used for modelling entire operational life of the ship initially built as a tanker and 20 years later converted to a FPSO. The models cover all particularities of the vessels including environment, sea state conditions and structural differences achieved after the conversion and they are used to conduct a complete stochastic spectral Fatigue analysis for entire service life of an already converted 25 year FPSO. Two hot spots are analyzed accounting for the combination of all loading conditions and Fatigue Damage of entire operational life is assessed.
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Fatigue Damage Assessment of Side Shell Longitudinals based on Spectral Approach
Brodogradnja, 2003Co-Authors: Smiljko Rudan, Yordan Garbatov, C. Guades SoaresAbstract:A work is presented for the Fatigue Damage Assessment of side shell longitudinals. The potential Damages are considered to occur in the side shell of the hull, at the connections between longitudinal stiffeners and transverse web frame. The long-term stress range acting on the elements is defined within a stochastic analysis as a function of wave induced pressure stresses that are combined with the stresses resulting from the vertical wave induced bending moment of the ship hull. Structural analysis is performed by the finite element method utilizing sub-model techniques. Fatigue Damage is calculated based on the Palgrem-Miner approach.
Vikas Kumar - One of the best experts on this subject based on the ideXlab platform.
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high temperature low cycle Fatigue Damage Assessment in near alpha imi 834 titanium alloy
Fatigue & Fracture of Engineering Materials & Structures, 2011Co-Authors: Jalaj Kumar, Kartik Prasad, Vikas KumarAbstract:In the present work, evolution of Damage under high-temperature (823 K) low cycle Fatigue loading condition in near α IMI-834 titanium alloy has been studied. The in situ Damage has been experimentally measured during cyclic deformation using the alternating current potential drop (ACPD) technique. The measured Damage curve has been compared with the Damage curves calculated through mechanical variables such as cyclic modulus and stress amplitude. The ACPD Damage curve has been found most sensitive towards high-temperature low cycle Fatigue Damage evolution.
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High‐temperature low cycle Fatigue Damage Assessment in near alpha IMI‐834 titanium alloy
Fatigue & Fracture of Engineering Materials & Structures, 2011Co-Authors: Jalaj Kumar, Kartik Prasad, Vikas KumarAbstract:In the present work, evolution of Damage under high-temperature (823 K) low cycle Fatigue loading condition in near α IMI-834 titanium alloy has been studied. The in situ Damage has been experimentally measured during cyclic deformation using the alternating current potential drop (ACPD) technique. The measured Damage curve has been compared with the Damage curves calculated through mechanical variables such as cyclic modulus and stress amplitude. The ACPD Damage curve has been found most sensitive towards high-temperature low cycle Fatigue Damage evolution.
Saiji Fukada - One of the best experts on this subject based on the ideXlab platform.
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The impact vibration-based Fatigue Damage Assessment of steel and steel fiber reinforced concrete composite girder
International Journal of Steel Structures, 2016Co-Authors: Saiji Fukada, Hiroshi MasuyaAbstract:The steel-concrete composite girder has been usually applied in the civil structures. The current Fatigue Damage Assessment on the composite girder, especially the negative bending region, mainly bases on the crack observation and deflection measurement. It is not stable sometimes, thus the impact vibration-based Fatigue Damage Assessment was considered instead. A 3.3m steel-steel fiber reinforced concrete (SFRC) composite girder was designed and tested. The Fatigue load, the impact load, and the static load were applied in the test. It showed that the local Fatigue Damage reflected by the tensile SFRC cracks may not be easily evaluated through observing the global mechanical change. However, the vibration modal parameters such as the vibration frequency, vibration mode, damping ratio might be useful for this. In particular, the vibration mode variation, which can be expressed by the Modal Assurance Criterion (MAC) value, may reflect the local Fatigue Damage on the composite girder.
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The Vibration Based Fatigue Damage Assessment of Steel and Steel Fiber Reinforced Concrete (SFRC) Composite Girder
MATEC Web of Conferences, 2015Co-Authors: Saiji Fukada, Hiroshi MasuyaAbstract:The steel-concrete composite girder has been usually applied in the bridge and building structures, mostly consisting of concrete slab, steel girder, and shear connector. The current Fatigue Damage Assessment for the composite girder is largely based on the strain values and concrete crack features, which is time consuming and not stable. Hence the vibration-based Fatigue Damage Assessment has been considered in this study. In detail, a steel-steel fiber reinforced concrete (SFRC) composite girder was tested. The steel fiber reinforced concrete is usually considered for dealing with the concrete cracks in engineering practice. The composite girder was 3.3m long and 0.45m high. The Fatigue load and impact excitation were applied on the specimen sequentially. According to the test results, the concrete crack development and global stiffness degradation during the Fatigue test were relatively slow due to the favourable performance of SFRC in tension. But on the other hand, the vibration features varied significantly during the Fatigue Damage development. Generally, it confirmed the feasibility of executing Fatigue Damage Assessment of composite bridge based on vibration method.
