Fatigue Evaluation of a Steel Bridge in Service through Stress History Measurement and Consideration of Stress Category

Increased running speed and axle weight in the transportation network lead to significant dynamic interactions between the vehicles and bridges. It is essential to capture these interactions in fatigue analysis of steel bridges. This paper presents a framework for fatigue evaluation of critical steel bridge details through multi-scale dynamic analysis of the train-track-bridge system and linear elastic fracture mechanics. The multi-scale coupled dynamic analysis allows accurate and efficient computation of fatigue stresses produced by the moving trains in structural details based on a vehicle-bridge analysis model composed of a 3D vehicle model, multi-scale bridge finite element model including the track system, and a wheel–rail interaction model. Field data from an existing steel-truss railway bridge are used to validate the multi-scale analysis method. Enhanced fatigue evaluation of the bridge detail is performed using the computed fatigue load effects and linear elastic fracture mechanics. The effects of the track irregularity and operating train speed on fatigue crack propagation life are investigated. The presented framework is general and can be applied to other types of steel bridges such as the steel-box girder bridge with orthotropic decks.

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Fatigue Evaluation of Rib-to-Deck Welded Joints of Orthotropic Steel Bridge Deck

Journal of Bridge Engineering ◽

10.1061/(asce)be.1943-5592.0000181 ◽

2011 ◽

Vol 16 (4) ◽

pp. 492-499 ◽

Cited By ~ 84

Author(s):

Samol Ya ◽

Kentaro Yamada ◽

Toshiyuki Ishikawa

Keyword(s):

Welded Joints ◽

Bridge Deck ◽

Steel Bridge ◽

Orthotropic Steel Bridge Deck ◽

Fatigue Evaluation

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Environmental Fatigue Evaluation Considering Transient Stress History for Piping

Volume 1A: Codes and Standards ◽

10.1115/pvp2016-63478 ◽

2016 ◽

Author(s):

Youn-Jung Kim ◽

Sun-Yeh Kang ◽

Byung-Jong Park ◽

Gee-Seok Kim ◽

Hyun-Min Kim

Keyword(s):

Three Dimensional ◽

Element Model ◽

Strain History ◽

Piping System ◽

Stress History ◽

Transient Stress ◽

Transient Strain ◽

Asme Code ◽

Fatigue Evaluation ◽

The Cost

The environmental fatigue evaluation for piping is performed based on conservative formulas and environmental correction factors (Fen) calculation because of the difficulty of finding transient strain history and to reduce the cost of the analysis. Therefore, more sophisticated analyses using a finite element model of piping would be required to meet Code requirement (cumulative fatigue usage factor including the environmental effects, CUFen < 1). The environmental fatigue evaluation was performed considering the transient stress history for pressurizer surge and spray piping. The stress histories due to the thermal moment and thermal gradient through the wall thickness were evaluated using a three-dimensional piping system model. The strain rate for Fen calculation was calculated in accordance with draft Code Case 10-293 and 14-1177. For the purpose of comparison, environmental fatigue usage factors and Fen are calculated based on the ASME Code NB-3600 rules. The differences of Fen, CUF, and CUFen are reviewed between the methods using NB-3200 rule and NB-3600 rule. Finally, this paper shows that environmental fatigue evaluation considering transient history is an effective method in lowering the environmental CUF value of the piping.

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Symptom Validity Testing

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2018.novdec03 ◽

2018 ◽

Vol 23 (6) ◽

pp. 14-15

Author(s):

Lee H. Ensalada

Keyword(s):

Memory Deficits ◽

Symptom Validity ◽

Sensory Cues ◽

Validity Testing ◽

Symptom Validity Testing ◽

Tunnel Vision ◽

Blurry Vision ◽

The Common ◽

Fatigue Evaluation ◽

Choice Testing

Abstract Symptom validity testing (SVT), also known as forced-choice testing, is a means of assessing the validity of sensory and memory deficits, including tactile anesthesias, paresthesias, blindness, color blindness, tunnel vision, blurry vision, and deafness. The common feature among these symptoms is a claimed inability to perceive or remember a sensory signal. SVT comprises two elements: a specific ability is assessed by presenting a large number of items in a multiple-choice format, and then the examinee's performance is compared to the statistical likelihood of success based on chance alone. These tests usually present two alternatives; thus the probability of simply guessing the correct response (equivalent to having no ability at all) is 50%. Thus, scores significantly below chance performance indicate that the sensory cues must have been perceived, but the examinee chose not to report the correct answer—alternative explanations are not apparent. SVT also has the capacity to demonstrate that the examinee performed below the probabilities of chance. Scoring below a norm can be explained by fatigue, evaluation anxiety, inattention, or limited intelligence. Scoring below the probabilities of chance alone most likely indicates deliberate deceptions and is evidence of malingering because it provides strong evidence that the examinee received the sensory cues and denied the perception. Even so, malingering must be evaluated from the total clinical context.

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Impairment Questions and Answers

Guides Newsletter ◽

10.1001/amaguidesnewsletters.1999.julaug02 ◽

1999 ◽

Vol 4 (4) ◽

pp. 4-4

Keyword(s):

Symptom Validity ◽

Validity Testing ◽

Symptom Validity Testing ◽

Negative Results ◽

Tunnel Vision ◽

Questions And Answers ◽

Blurry Vision ◽

Fatigue Evaluation ◽

Choice Testing ◽

Rule Out

Abstract Symptom validity testing, also known as forced-choice testing, is a way to assess the validity of sensory and memory deficits, including tactile anesthesias, paresthesias, blindness, color blindness, tunnel vision, blurry vision, and deafness—the common feature of which is a claimed inability to perceive or remember a sensory signal. Symptom validity testing comprises two elements: A specific ability is assessed by presenting a large number of items in a multiple-choice format, and then the examinee's performance is compared with the statistical likelihood of success based on chance alone. Scoring below a norm can be explained in many different ways (eg, fatigue, evaluation anxiety, limited intelligence, and so on), but scoring below the probabilities of chance alone most likely indicates deliberate deception. The positive predictive value of the symptom validity technique likely is quite high because there is no alternative explanation to deliberate distortion when performance is below the probability of chance. The sensitivity of this technique is not likely to be good because, as with a thermometer, positive findings indicate that a problem is present, but negative results do not rule out a problem. Although a compelling conclusion is that the examinee who scores below probabilities is deliberately motivated to perform poorly, malingering must be concluded from the total clinical context.

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