• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.10a
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• pp.59-64
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• 1989

On this condition of steel bridge member having a crack, occasionaly it is improssible to measure of stress history and to extract test specimen. Under this situation, tried to estimate remaining service life from statistical data on traffic and existing results of fatigue test without measuring of stress history and fatigue test. The main results are as following (1) Stress history of simple beam estimated from Montecallo simulation method with probabilistic model of traffic can be use to estimate remaining fatigue life instead of measuring of stress history. (2) In such a case measuring of remaining fatigue life at bridge member haying a crack, influences of RMS model and RMC model on fatigue crack growth rate are not differ without difference of applied stress range. (3) Application of cut off method may be overestimate remaining fatigue life.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.11-16
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• 1989

This paper presents a fatigue reliability model for the reliability-based evaluation of remaining fatigue life of existing rail-road bridges. It is demonstrated that the simple fatigue reliability model based on the Weibull distribution of fatigue life can be extended by incorporating various effects due to the rate of the train-traffic increase and in-service Inspections. The paper also suggests the system fatigue reliability analysis using an approximate formulation and 2nd-order bound solutions. The application of the proposed model to existing rail-road brdiges based on field load tests shows that it may be practically used for the assessment of fatigue reliability, remaining life, and in-service inspection scheduling of existing rail-road bridges.

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.489-497
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• 2010

The remaining life estimation of the level luffing crane component, which has operated for about 20 years is examined carefully, especially on the crane structures. To analyse the crane sructures, the basic load and load combination needed to be considered. We modeled various parts of the level luffing crane to analyse fatigue. Fatigue analysis results showed that the level luffing crane is in the fatigue life so that the crane is in the safe state in fatigue cumulative damage. Analysis results show that the remaining life of a jib upper beam would be about 10 years therefore, the level luffing crane should be stable for fatigue for that period.

• Structural Engineering and Mechanics
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• v.53 no.4
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• pp.681-702
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• 2015

Fracture analysis and remaining life prediction has been carried out for aluminium alloy (Al 2014A) plate panels with concentric stiffener by varying sizes and positions under fatigue loading. Tension coupon tests and compact tension tests on 2014A have been carried out to evaluate mechanical properties and crack growth constants. Domain integral technique has been used to compute the Stress intensity factor (SIF) for various cases. Generalized empirical expressions for SIF have been derived for various positions of stiffener and size. From the study, it can be concluded that the remaining life for stiffened panel for particular size and position can be estimated by knowing the remaining life of corresponding unstiffened panel.

• Structural Engineering and Mechanics
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• v.23 no.6
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• pp.651-674
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• 2006

The fatigue cracks initiate and propagate in the Armored Vehicle Launch Bridge (AVLB) components, especially like the splice doubler angle, splice plate, and bottom chord, due to the cyclic loading by repeated AVLB-launchings and tank-crossings. In this study, laboratory fatigue tests were conducted on six aluminum 2014-T6, four aluminum 7050-T76511, and four ASTM A36 steel compact-tension specimens to evaluate the crack growth behavior of the materials used for the components. The experimental results provide the relationship (Paris Law) between crack growth rate, da/dn, and stress intensity range, ${\Delta}K$, whose material dependent constants C and m can later be used in the life estimation of the components. Finite Element Method (FEM) was used to obtain the stress intensity factor, K, of the components with cracks. Because of the complexity of loading conditions and component geometry, several assumptions and simplifications are made in the FEM modeling. The FEM results, along with the results obtained from laboratory fatigue tests, are then utilized to estimate critical crack length and remaining life of the components.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.329-338
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• 1999

A systematic procedure to evaluate fatigue damages and to predict remaining fatigue lives is introduced for a steel railway bridge. Fatigue damages are evaluated by using the currently available fatigue damage theory. Fatigue lives with the condition of fatigue crack initiation are estimated by the probabilistic approach based on the reliability theory as well as the simplified procedure. A equivalent deterministic procedure is also suggested to assess the remaining fatigue life under various traffic conditions. Numerical simulations are used to assess dynamic stress histories with correction factors. Loading models are obtained from the passenger volume data. Train coincidences are also considered. Based on the results, the fatigue life is found to be underestimated by without considering the coincidence of trains on the bridge. The simplified method proposed in this study are found to yield approximately the same results as the systematic procedure.

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.120-128
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• 1995

The fatigue failure of rail is a principal source of derailment accidents. The reduction of fatigue failures can be achieved by Intensive track maintenance and periodic safety assessments for the railway. For the safety assessments, it is required to have more accurate knowledge for fatigue behavior such as the crack initiation, propagation, crack growth rate and the remaining service life in rail. In this paper, the mean stress effects for the fatigue behavior of rail steel are studied. For this study, the fatigue test is conducted and some equations for fatigue evaluation are applied and compared. From the results, we can see that the fatigue crack growth rate is the more increased as the men stress Is the more increased, the mean stress effect is represented well by the combination of stress intensity factor range and maximum stress intensity factor and Crooker and Range's equation represented by ${\Delta}K, K_{max}$ is the best fit for fatigue evaluation and safety assessment of rail.

• Structural Engineering and Mechanics
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• v.32 no.3
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• pp.459-475
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• 2009

This paper presents analytical methodologies for remaining life prediction of plain concrete structural components considering tension softening and size effects. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. Size effect has been accounted for by modifying the Paris law, leading to a size adjusted Paris law, which gives crack length increment per cycle as a power function of the amplitude of a size adjusted stress intensity factor (SIF). Details of tension softening effects and size effect in the computation of SIF and remaining life prediction have been presented. Numerical studies have been conducted on three point bending concrete beams under constant amplitude loading. The predicted remaining life values with the combination of tension softening & size effects are in close agreement with the corresponding experimental values available in the literature for all the tension softening models.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.1-7
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• 2018

The Continuous Ship Unloader (CSU) is an equipment that unloads freight from the ship docked in the port to the land. And the design target life time is designed to be 30 to 50 years, and it is classified as a semi-permanent large facility. However, cracks may occur due to structural defects, abnormal loads, and corrosion, and fatigue failure may occur before the design life is reached. In this study, we predicted the remaining life time of the main component of the CSU considering crack. And also proposed inspection cycle for maintenance of CSU based on the results of the remaining life time prediction. For this purpose, the structure, operational stresses of the CSU were analyzed and main members were selected. And tensile tests and fatigue crack propagation tests were performed with SM490YA and SM570TMC, which are used as main materials for CSU.

• Computers and Concrete
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• v.5 no.3
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• pp.261-277
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• 2008

This paper presents methodologies for remaining life prediction of plain concrete structural components considering tension softening effect. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. A methodology to account for tension softening effects in the computation of SIF and remaining life prediction of concrete structural components has been presented. The tension softening effects has been represented by using any one of the models mentioned above. Numerical studies have been conducted on three point bending concrete structural component under constant amplitude loading. Remaining life has been predicted for different loading cases and for various tension softening models. The predicted values have been compared with the corresponding experimental observations. It is observed that the predicted life using bi-linear model and power curve model is in close agreement with the experimental values. Parametric studies on remaining life prediction have also been conducted by using modified bilinear model. A suitable value for constant of modified bilinear model is suggested based on parametric studies.