• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.463-473
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• 2000

This paper presents the results of the experimental and analytical investigation for the fatigue strength of welded details frequently used in steel bridges, especially for the details with relatively lower fatigue strength. The welded details included four kinds of welded details corresponding to the categories C, D, E and E' which represent the flange attachment details, web attachment details, transverse stiffeners and cover-plate details. Tensile fatigue tests were performed. The test results were compared with other available test results and the fatigue criteria of AASHTO, JSSC and Eurocode specifications. Generally, our test results were well agreed with other test results and satisfied with above-mentioned fatigue design provisions. However, it was found that transversely loaded weld-details showed lower fatigue strength than longitudinally loaded weld-details in transverse stiffener detail, and the test results of those details were not satisfied with AASHTO fatigue provisions. Examining the effect of length of gusset plate attachment details, welded details with longer attachment showed relatively lower fatigue strength, especially for the out-of-plane gusset plate details. It is recommended to perform additional fatigue tests with various loading and detail parameters and to establish the more detailed fatigue categories such as Eurocode or JSSC

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.1-8
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• 1991

Recently the use of steel fibers has been increased in flexural members and columns of concrete structures subjected to cyclic loadings; such as bridge decks, highway roads, runway of airport, buildings, etc.. However only a few experimental tests have been carried out under fatigue loading. In the present study, the reinforced concrete beams with 1% and 2% steel fiber volume fraction are investigated with and without stirrups. It has been found that in fatigue tests, the failure of the beam is usually due to breaking of fibers rather than fiber pull-out. A comparison of experiments and numerical analysis using the nonlinear F.E.M. program (ADINA) is also presented herein.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.209-223
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• 2013

This study was to evaluate the stress distributions of prefabricated, customized abutments and fixtures according to their material and shape by three-dimensional finite element analysis. And to investigate the fatigue life and fracture characteristics. Mandibular models were fabricated by reconstruction of the CT scan of patients with normal occlusion. A total of six finite element models were designed, a load of 100 N was applied on the buccal cusps vertically, and 30 degree obliquely. 10 specimens each were fabricated for the more clinically widely used 4 type abutments and were loaded according to ISO 14801. Differences in stress distribution patterns were not found according to the materials of the abutments and fixtures. But a slight difference in the stress level was detected. Customized abutment groups showed lower crown stress levels. One-piece zirconia implant showed the lowest bone stress levels. In the fatigue test, highest values were measured in group 7. Prefabricated abutments showed less variation of fatigue life (P<0.05). Use of customized abutments can improve the fracture resistance of restorations. Especially, use of customized zirconia abutments reinforced by titanium screw connecting parts is recommended.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.363-375
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• 1997

This study encompasses the performance of static and fatigue test for the 8 large scale test specimens to clarify the fatigue behavior of coped stringer and the effect of the repair and strengthening on the damaged stringer of the floor system in steel railway bridges. For the purpose of the research, the actual stress wave for the existing bridge was measured, the basic stress range frequency histogram was made and the equivalent stress range was calculated. Using the result from the equivalent stress range made by adjusting the stress range, the static and fatigue test was carried out by identifying the previous rehabilitation and after. As the result of the static tests, it was revealed that the level of local stress under the S1 specimen test of the real equivalent stress range was similar to tensile strength of the test material, and it was consistent with the requirement of the initiation condition of the fatigue crack. Through the various rehabilitation methods to the damaged specimens, the effects of the repair and reinforcement were analyzed. According to the results of the repair of effect, bolting the high tension bolt over the stop hole was confirmed to be more adequate method than drilling only stop hole to delay the fatigue crack growth. Futhermore, in case of the stringer subjected by bending moment, the reinforcement over the upper flange side was determined to be a useful strengthening method, and the reinforcement to the web of the stringer was not appropriate to accomodate as a adequate strengthening method. Also it was confirmed that the category of the fatigue design for the coped stringer met with the category E specified on the fatigue design criteria of the Highway Standard Specification in Korea.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.187-199
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• 1998

The highspeed railway bridge which support continuous and high moving mass evalute the dynamic state and make the displacement of the bridge makes more or less, but up to this time the bridges are designed by the static design concept. for example when we design bridge we use impact factor, which only times the static load makes dynamic load. But becouse it simples. it can't express all of the effects. And so, in this report we study the modeling method of the moving mass and the dynamic factor.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.443-449
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• 2004

Methods for mixing variable types of steel fibers have been developed recently to suppress outbreak of crack or to control the width of crack and improve the load resistible capacity at the same time. On the other hand, uncertainty by complex nature of destruction dynamics of steel fiber reinforced concrete(SFRC) is included. In this study, analysis of reliance considering uncertainty of SFRC beam is done. For this, intensity limit state model was proposed. Moreover, characteristic values about almost every kinds of probability variables were collected and presented according to home and foreign references. Process of improving uncertainty from the result of experiments by Bayseian updating method is also proposed on the purpose of offering better statistical characteristic values with more data in the new future. Fatigue fracture probability equation is proposed and needed statistical characteristic values were presented to analyze fatigue reliance

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.997-1004
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• 2017

The life of elevator wire ropes is one of the most important characteristics of an elevator, which is closely related to the safety of users and its maintenance policy. It is not cost effective to measure the lifetime of elevator wire ropes during their use. In this study, the life estimation of elevator wire ropes (8x19W-IWRC) is considered using accelerated degradation test data. A bending fatigue tester is used to perform the accelerated degradation tests, incorporating the acceleration factor of tensile force. Assuming that the life of wire ropes is log-normally distributed, two life estimation methods are suggested and their results are compared. The first method estimates the life of wire ropes utilizing the accelerated life model with pseudo lives obtained from a linear regression model. The second method estimates the life using a logistic model based on failure probability.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.186-186
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• 2010

개별 블레이드 피치 제어(individual blade pitch control)는 각각의 로터 블레이드의 피치각을 독립적으로 조정함으로써 블레이드에 작용하는 공력을 변화시키는 원리로 풍력 터빈 구조물에 발생하는 동적 피로하중을 저감시키기 위한 제어기법이다. 그러나 개별 피치 제어에 의해 발생하는 각 블레이드의 독립적인 피치 운동은 풍력 터빈 회전자에 비대칭성을 야기하고 구조물의 동적 불안정 현상을 발생시킬 수 있기 때문에 이에 대한 정확한 동적 해석이 선행되어야 한다. 하지만 블레이드의 피치 운동이 반영된 풍력 터빈은 시변계로 간주되어 기존의 시불변계 해석기법을 직접 적용할 수 없기 때문에 동적 해석에 어려움이 있다. 이 논문에서는 각각의 블레이드 피치운동을 주기함수로 근사화 함으로써 풍력 터빈을 주기 시변계로 모형화한다. 그리고 효율적으로 주기 시변계의 근사해를 구하기 위한 변조 좌표 변환(modulated coordinate transformation)기법을 적용하여 블레이드의 피치운동이 반영된 풍력 터빈의 동적 안정성 해석을 수행하였다. 그리고 현재 풍력 터빈의 동적 해석에 활용되는 대표적인 해석 기법인 다중 블레이드 좌표변환(multi-blade coordinate transformation)기법을 이용한 해석보다 정확한 결과를 얻을 수 있음을 보였다.

• Journal of Korean Society of Steel Construction
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• v.13 no.4
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• pp.337-349
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• 2001

This study present an optimum deck and girder system design for minimizing the life-cycle cost (LCC) of orthotropic steel deck bridges. The problem of optimum LCC design of orthotropic steel deck bridges is formulated as that of minimization of the expected total LCC that consists of initial cost, maintenance cost, expected retrofit costs for strength, deflection, and fatigue. To demonstrate the effect of LCC optimum design of orthotropic steel deck bridges, the proposed optimum LCC design is compared with the conventional method for orthotropic steel deck bridges design. From the numerical investigations, it may be positively stated that the proposed optimum design procedure for orthotropic steel deck bridges based on the LCC will lead to more rational, economical and safer design.

• International Journal of Highway Engineering
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• v.2 no.2
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• pp.139-148
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• 2000

Currently existing Accelerated Pavement Testing (APT) systems developed in several countries have been employed mainly to test the performance of asphalt pavement. Meanwhile, the length of concrete pavement is similar to that of asphalt pavement in expressways of Korea. and is expected to increase due to its durability and compatibility to our weather condition. To meet the society's demand of having our own APT system which can examine the long-term performance of concrete pavement, a contract study to develop Korea Accelerated Loading and Environment Simulator (KALES) for concrete pavement has been performed for 3 years from 1997 through 1999. Through the project, a detailed design was Peformed for the KALES system in which the entire structure of KALES, loading mechanism, wandering mechanism, suspension system, driving system were proposed. Also in advance to design a full-scale KALES system, a sample scale model was manufactured and tested for operating motion and force distribution. It is evident that the proposed prototype KALES system will provide higher degree of traffic simulation and durable operation, based on the satisfactory fatigue analysis.