Fatigue Reliability Evaluation of Old Steel Bridges Based on Probabilistic Fracture Mechanics

2006 ◽  
Vol 324-325 ◽  
pp. 435-438 ◽  
Author(s):  
Chun Sheng Wang ◽  
Jian Guo Nie ◽  
Ai Rong Chen ◽  
Wei Zhen Chen ◽  
Yue Xu
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Steel Bridges ◽  
Bridge Management ◽  
Fatigue Reliability ◽  
Original Design ◽  
Probabilistic Fracture Mechanics ◽  
Evaluation Models ◽  
Remaining Fatigue Life

There are many old steel bridges on Chinese transportation lines, which keep their normal traffic service function. The old bridges are often required to carry an increasing volume of traffic and heavier vehicles than the original design, so bridge management departments pay more attention to the actual remaining fatigue life of such structures. Based on probabilistic fracture mechanics theory, the member and the system fatigue failure evaluation models for old steel bridges are all proposed, and the fatigue reliability analysis program is developed using Monte-Carlo. As a case study, the evaluation models are used to predicate the fatigue reliability of Zhejiang Street Bridge. According to evaluation results, the probabilistic remaining fatigue life, safe inspection intervals and maintenance strategy are determined.

Prediction Approach for Corrosion Fatigue Life of Aircraft Structure Based on Probabilistic Fracture Mechanics

2006 ◽  
Vol 324-325 ◽  
pp. 943-946
Author(s):  
Xiao Ming Tan ◽  
Yue Liang Chen ◽  
Ping Jin
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Corrosion Fatigue ◽  
Failure Process ◽  
Short Crack ◽  
Aircraft Structure ◽  
Probabilistic Fracture Mechanics ◽  
Fracture Failure ◽  
Reliability Method ◽  
Prediction Approach

The corrosion, corrosion fatigue and fracture failure process of aircraft structure is directly concerned with combined effect of many factors, such as load, material characteristics, corrosive environment and so on. The process is very complicated, and there is typical randomness. Based on probabilistic fracture mechanics, with consideration of the limitation of the conventional probabilistic approaches for prediction of corrosion fatigue life of aircraft structure at present, and a new reliability approach under loading spectrum was proposed, in which corrosion damage and fatigue crack damage was united as a same damage parameter. Short crack and long crack growth behavior was separately discussed, and influence of short crack aspect ratio on structure life was discussed. The Advanced First-Order Reliability Method, Importance Sampling Method and iteratively advanced Second-Order Reliability Method were used to compute the fracture failure probability. The results show that the model is feasible. By sensitivity analysis of random parameter, the important parameter was obtained, which helped to monitor the structure fatigue life.

On Remaining Fatigue Life Fracture Mechanics Analysis of Free-Spanning Pipelines Using Shell and Line-Spring Elements

2002 ◽  
Author(s):  
F. Redaelli ◽  
B. Skallerud ◽  
B. J. Leira
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Cross Flow ◽  
Finite Element Program ◽  
Shell Elements ◽  
Cyclic Stresses ◽  
Vortex Induced Vibrations ◽  
Element Program ◽  
Remaining Fatigue Life

The present paper addresses fatigue crack-growth for free-spanning pipelines. The main sources of cyclic stresses which cause the crack-growth are vortex-induced vibrations (VIV) of the pipeline in the cross-flow and in-line directions. In the presence of initial weld defects, such cyclic stresses may lead to leakage and sudden fracture. The crack-growth process is modelled using so-called line-spring elements. These are matched with shell elements which are applied for modelling the pipe itself. The crack-growth is simulated by performing several simulations with different crack sizes. The shape of the crack also allowed to vary during the growth (i.e a/c-ratio). The static equilibrium position of the pipeline for a specific free span is first established by the non-linear Finite Element program ABAQUS. The line-spring elements are matched to interface with the shell elements which represent the pipe outside the region where the crack is located. Based on such simulations, the stress intensity factors at the crack-tip are computed. These calculations are performed for several different crack-sizes. Finally, the remaining fatigue life is estimated by means of fracture mechanics in terms of analytical and semi-empirical approaches.

Research on Fatigue Life of Autofrettaged Thick-Walled Cylinder in Probabilistic Fracture Mechanics

2012 ◽  
Vol 249-250 ◽  
pp. 36-39 ◽  
Author(s):  
Ai Jun Chen ◽  
Zi Chu Cha ◽  
Zhi Qun Wang
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Bauschinger Effect ◽  
Fatigue Cracks ◽  
Analysis Method ◽  
Intensity Factors ◽  
Probabilistic Fracture Mechanics ◽  
Best Fit ◽  
Elliptical Cracks ◽  
Walled Cylinder

Based on the theory of probabilistic fracture mechanics and Monte Carlo simulation, reliability analysis method for fatigue life of autofrettaged thick-walled cylinder was given. The forms of fatigue cracks in bore of autofrettaged thick-walled cylinder were considered as semi-elliptical cracks. The autofrettage residual stress solution was suitable for the thick-walled cylinder made of steel with strain hardening and Bauschinger effect. The stress intensity factors of thick-walled cylinder were calculated according to weight function method. The analysis of the examples showed that lognormal distribution is the best fit for fatigue life. Finally, the fatigue life of autofrettaged thick-walled on the condition of different reliabilities and confidences were presented.

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