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Loading of bridges and accumulation of fatigue damage
Rieger, M. ; Marek, Pavel
The article presents discussion and recommendation in connection with influence and evaluation methods of bridge loading events. Newly, according to Eurocode 3, two reliability concepts may be considered: damage tolerant concept and safe life concept. Fatigue life assessment may be based on fully probabilistic concept, too. The loading as well as response history should be taken into consideration and a fatigue criterion, based on the stress-range concept, should be applied. Crack grown may be modeled using LEFM procedures, initial crack size ai may be determined as input random variable with log-normal distribution.
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Fatigue parameters of cement based composited: measuring and modeling
Keršner, Z. ; Seitl, Stanislav ; Pukl, R.
This paper introduces the basic fracture mechanics parameters of advanced building materials –selected glass fibers reinforced cement based composites and their fracture and fatigue behavior is investigated. Specimens tested were prepared as high performance concrete/mortar developed by ZPSV, a.s. company for production of thin-walled panels/elements. The dosage of cement CEM I 42.5R Mokra was 1000 kg per m3 of fresh mixture, water to cement ratio was 0.28, superplasticizer Spolostan; sand aggregates of 4 mm maximum size were used. . Alkali-resistant glass fibers (glass with high content of zirconium oxide) are applied with a dosage of 5 kg per m3. The introductory study was introduced by the authors, the study is performing in matter of the project Basic fatigue characteristic and fracture of advanced building materials.
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Výpočtová analýza růstu únavové trhliny v kole testovaném podle normy EN 13262
Hutař, Pavel ; Náhlík, Luboš ; Knésl, Zdeněk ; Kunz, Ludvík ; Matušek, P.
In this paper, the experimental set up corresponding to the test unit used for the full-scale fatigue test has been modeled and the numerical method for reliable estimation of residual fatigue lifetime of wheel web tested according to EN 13 262 Standard has been developed. Numerical calculations are based on finite element method utilizing the system ANSYS. The experimentally observed cracks in the wheel web have been taken as the initial crack configuration. Numerical calculations simulating the initial crack growth in the wheel web loaded by experimental set up have been performed. Under assumptions of linear elastic fracture mechanics the residual fatigue life of the cracked wheel has been predicted. The material properties necessary for numerical modeling were determined from the fatigue tests performed on small specimens taken from real wheel webs. The results obtained can be used for more reliable design of railway wheels.
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Assessment of the fatigue damage of steel bridges
Rieger, M. ; Marek, Pavel
This paper turns attention to the long term recording of the response to the traffic load of a steel freeway bridges using special monitoring devices. The application of such monitoring system allows for the reliability assessment corresponding to the accumulation of fatigue damage of the main components of steel load carrying systems considering the actual loading history as well as the dynamic response of the bridge loading. The safety assessment, referring to the accumulated damage, is performed using the probabilistic to SBRA method.
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Kalibrace potenciálové metody pro měření růstu únavové trhliny
Kotecký, Ondřej ; Degallaix, S. ; Polák, Jaroslav
The DC potential drop method widely used to follow long crack growth, was adapted to measure the growth and to estimate the shape of mechanically short fatigue cracks initiated on a small defect in an austenitic-ferritic stainless steel. The paper deals with problems of calibration of the method by the means of finite element analysis. A comparison between measured and actual crack length and crack front in notched specimens is presented.
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