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J. K. Hong - One of the best experts on this subject based on the ideXlab platform.
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Fatigue of Tubular Joints: Hot Spot Stress Method Revisited
Journal of Offshore Mechanics and Arctic Engineering, 2012Co-Authors: Pingsha Dong, J. K. HongAbstract:A series of well-known tubular joints tested in UKSORP II have been re-evaluated using the mesh-insensitive structural Stress method as a part of the on-going Battelle Structural Stress JIP efforts. In this report, the structural Stress based analysis procedure is first presented for applications in tubular joints varying from simple T joints, double T Joints, YT joints with overlap, and K joints with various internal stiffening configurations. The structural Stress based SCFs are then compared with those obtained using traditional surface extrapolation based hot Spot Stress methods. Their abilities in effectively correlating the fatigue data collected from these tubular joints are demonstrated. These tests are also compared with the T curve typically used for fatigue design of tubular joints as well as the structural Stress based master S-N curve adopted by ASME Section VIII Div 2. Finally, some of the implications on fracture mechanics based remaining life assessment for tubular joints are discussed in light of the results obtained in this investigation.
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Fatigue of Tubular Joints: Hot Spot Stress Method Revisited
Volume 5: Materials Technology; CFD and VIV, 2008Co-Authors: Pingsha Dong, J. K. HongAbstract:A series of well-known tubular joints tested in UKSORP II have been re-evaluated using the mesh-insensitive structural Stress method as a part of the on-going Battelle Structural Stress JIP efforts. In this report, the structural Stress based analysis procedure is first presented for applications in tubular joints varying from simple T joints, double T Joints, YT joints with overlap and K joints with various internal stiffening configurations. The structural Stress based SCFs are then compared with those obtained using traditional surface extrapolation based hot Spot Stress methods. Their abilities in effectively correlating the fatigue data collected from these tubular joints are demonstrated. These tests are also compared with the T curve typically used for fatigue design of tubular joints as well as the structural Stress based master S-N curve adopted by ASME Section VIII Div 2. Finally, some of the implications on fracture mechanics based remaining life assessment for tubular joints are discussed in light of the results obtained in this investigation.Copyright © 2008 by ASME
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Analysis of Hot Spot Stress and Alternative Structural Stress Methods
Volume 3: Materials Technology; Ocean Engineering; Polar and Arctic Sciences and Technology; Workshops, 2003Co-Authors: P. Dong, J. K. HongAbstract:There is a growing need for robust finite element based fatigue assessment procedures for welded joints in offshore/marine structures. Although widely accepted in tubular structures, the applications of the conventional hot Spot Stress (HSS) procedures in plate structures have proven to be problematic in some joint types. There are a series of on-going international efforts that are intended to address some of the issues to improve the consistency of the HSS calculation procedures for plate structures. In this regard, alternative structural Stress (SS) procedures that share some similarities to conventional HSS methods have been developed. The SS method has been shown to be effective in calculating structural Stresses directly at failure locations such as at weld toes with minimum mesh-sensitivity. In this paper, detailed analysis and assessments of the conventional HSS and the alternative SS procedures are presented. Starting with the fundamental definitions of both HSS and SS parameters, the underlying mechanics associated with the two types of the Stress analysis methods will be discussed by considering series of typical joint types, particularly on some of the important Stress concentration characteristics that separate tubular joints from plate joints. Then, the necessary and sufficient conditions required for a Stress definition relevant to fatigue and its calculation procedures will be demonstrated for both methods. Areas of concerns and improvements for both methods will be demonstrated by using a series of selected joint types typical of those in marine/offshore structures. Finally, the corresponding S-N data will be used to demonstrate the relative effectiveness of HSS and SS methods in consolidating the data from drastically different joint types into a single S-N curve.© 2003 ASME
Gary Marquis - One of the best experts on this subject based on the ideXlab platform.
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fatigue assessment of high frequency mechanical impact hfmi improved fillet welds by local approaches
International Journal of Fatigue, 2013Co-Authors: Halid Can Yildirim, Gary Marquis, Zuheir BarsoumAbstract:Local fatigue assessment methods like the structural hot Spot Stress and effective notch Stress methods as defined by the International Institute of Welding are widely used by design engineers and researchers to assess the fatigue strength of welded components. This paper provides a comprehensive evaluation of published data for welded joints which had been improved using high frequency mechanical impact (HFMI) treatment. All of the published data for HFMI-treated welds are presented in terms of nominal Stress. The goal of the current paper is to establish local fatigue assessment procedures for improved fillet welds. In total, 160 published experimental results for longitudinal and cruciform welds subjected to R = 0.1 axial loading are evaluated. Local Stress quantities for each joint were assessed based on the finite element analyses and reported nominal Stress values. A correction procedure for yield strength that was previously verified for nominal Stress-based fatigue assessment is also applied to the local Stress methods studied in this paper. For both the structural hot Spot Stress and effective notch Stress methods, sets of characteristic fatigue strength curves as functions of yield strength are proposed and verified. The structural hot Spot Stress method includes one set of fatigue strength curves for load-carrying welds and a second set for non-load carrying welds. The effective notch Stress method includes a single set of curves for all welds. All of the design curves proposed in this study are conservative with respect to available fatigue test data.
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Improving the accuracy of structural hot-Spot Stress approach
steel research international, 2006Co-Authors: Iikka Poutiainen, Gary MarquisAbstract:A method for extending the applicability of the structural hot-Spot Stress method for fatigue assessment of welded structures is discussed. The structural hot-Spot Stress method for plate structures, as currently presented in commonly used design guidance documents, cannot account for the effect of weld size, and load carrying fillet welds are assessed using a different S-N curve as compared to non-load carrying fillet welds. This paper presents a proposal to linearize the local Stress distribution through the plate thickness in the plane of the weld toe. This proposal considers the forces transmitted by the weld itself. A bilinear Stress distribution, which partially captures the local effect of the weld, is derived from the non-linear Stress distribution. The non-linear distribution is based on equilibrium and the Stress in the fillet weld. A simple procedure is presented to determine the bilinear curve from the nominal weld Stress. This is a great advantage in finite element analysis when only nominal base plate Stress and nominal weld Stresses need to be determined. When compared to the more conventional structural Stress approach, the new method also has the advantage that extrapolation is not required. The same weld Stresses can also be used in the analysis of the root cracks. The proposed method was scaled to correspond to the traditional structural hot-Spot Stress method using detailed linear elastic fracture mechanics simulations. The method is only applied to fully load-carrying welds here but can also be used for partial load-carrying welds. A symmetric splice plate having a fully loaded fillet weld is presented as an example case. The influence of base plate thickness is studied as well.
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finite element methods for structural hot Spot Stress determination a comparison of procedures
International Journal of Fatigue, 2004Co-Authors: Ilkka Poutiainen, Pasi Tanskanen, Gary MarquisAbstract:Three methods for determining the structural hot Spot Stress for fatigue analysis of welded structures are presented. These include linear surface extrapolation (LSE), through thickness at the weld toe (TTWT), and the Dong method. The methods were applied to evaluate finite element analysis results obtained for a simple 2D structure and 3D structural detail. The limits and accuracy of the methods were investigated. LSE and TTWT are based on normal Stresses while the Dong method also requires that shear Stresses are correct. For 2D models, TTWT and the Dong methods gave uniform results for virtually all mesh variations used in this study. For 3D structures, the Dong method requires more care during meshing and is numerically more demanding during post-processing than other methods. When TTWT is used for 3D structures, the computed structural Stress is virtually identical to that found using Dong method, but the meshing requirements are somewhat easier and the post-processing requires only that nodal averaging be considered.
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Finite element methods for structural hot Spot Stress determination—a comparison of procedures
International Journal of Fatigue, 2004Co-Authors: Ilkka Poutiainen, Pasi Tanskanen, Gary MarquisAbstract:Three methods for determining the structural hot Spot Stress for fatigue analysis of welded structures are presented. These include linear surface extrapolation (LSE), through thickness at the weld toe (TTWT), and the Dong method. The methods were applied to evaluate finite element analysis results obtained for a simple 2D structure and 3D structural detail. The limits and accuracy of the methods were investigated. LSE and TTWT are based on normal Stresses while the Dong method also requires that shear Stresses are correct. For 2D models, TTWT and the Dong methods gave uniform results for virtually all mesh variations used in this study. For 3D structures, the Dong method requires more care during meshing and is numerically more demanding during post-processing than other methods. When TTWT is used for 3D structures, the computed structural Stress is virtually identical to that found using Dong method, but the meshing requirements are somewhat easier and the post-processing requires only that nodal averaging be considered.
Tommy H.t. Chan - One of the best experts on this subject based on the ideXlab platform.
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A Multi-scale Finite Element Model of Tsing Ma Bridge for Hot Spot Stress Analysis
2007Co-Authors: Tommy H.t. Chan, K.y. Wong, L. GuoAbstract:Failure due to fatigue damage is an important failure mode for large suspension bridges and welded connections are usually identified as the most vulnerable locations for accumulative fatigue damage of existing bridges. The hot-Spot Stress approach has been successfully applied in fatigue evaluation of the welded joints. Traditionally a structural analysis using a global FE model is first conducted to determine the critical locations, based on which a local analysis is then carried out to obtain the hot-Spot Stress distribution that is the basis of fatigue status assessment process. Alternatively, a multi-scale model is proposed by using the mixed dimensional coupling method merging typical detailed joint geometry models into the global model so that the hot-Spot Stress can be directly output through a single step of analysis. As a case study, a multi-scale model of Tsing Ma Bridge was developed accordingly and the calculated results were compared with those of the global structural model and the structural health monitoring data with respect to first few order natural frequencies and vertical displacement at GPS level sensor-installed locations, and hot Spot Stress situation combined with Stress concentration factors at a typical intersection joint. The comparison results show that the multi-scale model output agrees well with those of global model and monitoring data within the acceptable range, indicating that, at the same engineering level, the developed multi-scale model is more convenient and yet appropriate for the purpose of hot Spot Stress analysis in fatigue evaluation.
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Hot Spot Stress analysis of fatigue for Tsing Ma Bridge critical members under traffic using finite element method
2007Co-Authors: Taiquan Zhou, Tommy H.t. ChanAbstract:The suspension bridge has more flexibility and repetitive vehicles produce Stress cycles in members. Then fatigue of the member is accumulated with the daily traffic loadings. In order to evaluate the working condition of the Tsing Ma Bridge, the online monitoring health system has been installed in long suspension bridge. The location of the strain sensor is not exactly at the critical member locations. The hot Spot Stress analysis for critical members is necessary for accurate fatigue evaluation of the bridge. The global finite element analysis of the Tsing Ma Bridge under traffic loading is performed to determine the critical fatigue member locations. A detailed local finite element analysis for the welded connections is performed to determine the hot Spot Stress of critical fatigue location. As a case for study, the calculated Stress concentration factor is combined with the nominal representative Stress block cycle to obtain the representative hot Spot Stress range cycle block under traffic loading from online health monitoring system. The comparison result shows that the nominal Stress approach cannot consider the most critical Stress of the fatigue damage location and the hot Spot Stress approach is more appropriate for fatigue evaluation.
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Hot Spot Stress approach for fatigue evaluation using finite element method
2005Co-Authors: Tommy H.t. Chan, T.q. Zhou, L. GuoAbstract:Fatigue design rules commonly used in practice are mainly based on the nominal Stress approach. An alternative method for the complicated welded steel joints fatigue design is the hot Spot Stress approach. To apply the hot Spot Stress approach for fatigue evaluation of long span suspension bridges, a finite element method is used to determine the hot Spot Stress of critical fatigue locations. Using the local finite element models of the Tsing Ma Bridge, typical joints are developed and the Stress concentration factors are then determined. As a case for study, the calculated Stress concentration factor is combined with the nominal representative Stress block cycle to obtain the representative hot Spot Stress range cycle block under traffic loading from the online health monitoring system installed on the Tsing Ma Bridge. A comparison is made between the nominal Stress approach and the hot Spot Stress approach for fatigue life evaluation of the Tsing Ma Bridge. The comparison result shows that the hot Spot Stress approach is more appropriate for fatigue evaluation.
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Hot Spot Stress approach for Tsing Ma bridge fatigue evaluation under traffic using finite element method
2005Co-Authors: Tommy H.t. Chan, Taiquan Zhou, L. GuoAbstract:The hot Spot Stress approach is usually adopted in the fatigue design and analysis of tubular welded joints. To apply the hot Spot Stress approach for fatigue evaluation of long span suspension bridges, the FEM is used to determine the hot Spot Stress of critical fatigue location. Using the local finite element models of the Tsing Ma Bridge, typical joints are developed and the Stress concentration factors are determined. As a case for study, the calculated Stress concentration factor is combined with the nominal representative Stress block cycle to obtain the representative hot Spot Stress range cycle block under traffic loading from online health monitoring system. A comparison is made between the nominal Stress approach and the hot Spot Stress approach for fatigue life evaluation of the Tsing Ma Bridge. The comparison result shows that the nominal Stress approach cannot consider the most critical Stress of the fatigue damage location and the hot Spot Stress approach is more appropriate for fatigue evaluation.
C. Guedes Soares - One of the best experts on this subject based on the ideXlab platform.
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Effect of weld shape imperfections on the structural hot-Spot Stress distribution
Ships and Offshore Structures, 2011Co-Authors: B. Gaspar, Yordan Garbatov, C. Guedes SoaresAbstract:This paper presents a probabilistic study of the effect of the weld shape imperfections on the structural hot-Spot Stress distribution along the weld toe using the Monte Carlo simulation and the finite element analysis method. A structural detail consisting of a plate strip with a transverse butt-welded joint and a tapered thickness step is used as a case study. The weld shape is modelled based on the weld profile parameters defined as random variables allowing the simulation of typical imperfections as a function of the imperfection level of welding. The analysis uses a linear finite element model built with the second-order solid elements. A finite element analysis program is used to calculate the Stress distribution on the vicinity of the weld toe and a standard extrapolation procedure is used to obtain the structural hot-Spot Stresses. Different weld shape imperfections are generated and their effect on the hot-Spot Stresses is calculated afterwards. The notch effect of weld toe is not included in the...
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Hot Spot Stress and Stress concentration factors due to different fabrication imperfections in deck structures
International shipbuilding progress, 2008Co-Authors: K. Chakarov, Yordan Garbatov, C. Guedes SoaresAbstract:This work deals with the Stress analysis of a longitudinally stiffened welded panel and evaluates the hot Spot Stress distributions and Stress concentration factors that result from different types of imperfections. The hot Spot Stresses and the Stress concentration factors are defined at locations adjacent to the transverse weld. Numerous calculations are performed representing realistic conditions of imperfections and various comparisons of hot Spot Stress distributions are presented. The Stress concentration factor for the cases of pure thickness step changes and for vertical angular imperfections are fit to a quadratic polynomial function.
Pingsha Dong - One of the best experts on this subject based on the ideXlab platform.
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Fatigue of Tubular Joints: Hot Spot Stress Method Revisited
Journal of Offshore Mechanics and Arctic Engineering, 2012Co-Authors: Pingsha Dong, J. K. HongAbstract:A series of well-known tubular joints tested in UKSORP II have been re-evaluated using the mesh-insensitive structural Stress method as a part of the on-going Battelle Structural Stress JIP efforts. In this report, the structural Stress based analysis procedure is first presented for applications in tubular joints varying from simple T joints, double T Joints, YT joints with overlap, and K joints with various internal stiffening configurations. The structural Stress based SCFs are then compared with those obtained using traditional surface extrapolation based hot Spot Stress methods. Their abilities in effectively correlating the fatigue data collected from these tubular joints are demonstrated. These tests are also compared with the T curve typically used for fatigue design of tubular joints as well as the structural Stress based master S-N curve adopted by ASME Section VIII Div 2. Finally, some of the implications on fracture mechanics based remaining life assessment for tubular joints are discussed in light of the results obtained in this investigation.
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Fatigue of Tubular Joints: Hot Spot Stress Method Revisited
Volume 5: Materials Technology; CFD and VIV, 2008Co-Authors: Pingsha Dong, J. K. HongAbstract:A series of well-known tubular joints tested in UKSORP II have been re-evaluated using the mesh-insensitive structural Stress method as a part of the on-going Battelle Structural Stress JIP efforts. In this report, the structural Stress based analysis procedure is first presented for applications in tubular joints varying from simple T joints, double T Joints, YT joints with overlap and K joints with various internal stiffening configurations. The structural Stress based SCFs are then compared with those obtained using traditional surface extrapolation based hot Spot Stress methods. Their abilities in effectively correlating the fatigue data collected from these tubular joints are demonstrated. These tests are also compared with the T curve typically used for fatigue design of tubular joints as well as the structural Stress based master S-N curve adopted by ASME Section VIII Div 2. Finally, some of the implications on fracture mechanics based remaining life assessment for tubular joints are discussed in light of the results obtained in this investigation.Copyright © 2008 by ASME
