• 제목/요약/키워드: Short Fatigue Crack

검색결과 62건 처리시간 0.019초

부식효과를 고려한 선체구조 검사계획안의 최적화 (Optimization for Inspecdtion Planning of Ship Structures Considering Corrosion Effects)

  • 김성찬;윤장호;등본유기부
    • 대한조선학회논문집
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    • 제36권4호
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    • pp.137-146
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    • 1999
  • 선체구조는 많은 수의 구조부재로 이루어져 있으며, 구조물의 안정성을 확보하기 위해 모든 부위의 검사를 위해서는 경제적, 사회적인 많은 비용이 필요하므로, 검사시기 및 검사방법의 최적화는 선체구조의 안정성확보 및 경제적 관점에서 매우 중요한 부분이 되고 있다. 선체구조 손상중 많은 부분이 균열이며 이러한 미세한 균열이 성장하여 대규모 파괴로 진전되기 전에 검사를 통하여 균열을 검출하고 수리하는 과정을 Markov 연쇄모델에 의해 이상화 시켰으며, 검사 계획안의 최적화는 유전적 알고리즘을 통하여 구현하였다. 특히 선박은 부식환경하에서 운항하므로 부식에 의한 선체구조부재의 치수가 감소하기 때문에 응력이 변하고 균열진전의 확률적인 특성 또한 변한다. 정상 Markov 연쇄모델로서는 이러한 부식에 의한 영향을 고려할수 없기 때문에 비정상 Markov 연쇄모델에 의해 부식의 영향을 고려하였다. 여러개의 부재군에 대한 검사 계획안의 최적화에 대하여 수치계산을 실시하여 그 특성을 비교하였고, 부식영향하의 부재군에 대하여 검사기간중에 발생되는 고정비용의 정도에 따른 경제성 분석 및 목표 파괴확률의 정도에 따른 검사계획의 차이를 살펴보았다. 수치계산 예를 통하여 전체비용을 줄이기 위해서는 피로수명이 짧은 부재군에 대한 피로수명을 향상시키는 방안이 가장 효율적임을 알 수 있다.

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축하중 분포 변화가 콘크리트 포장의 공용성 예측결과에 미치는 영향 연구 (Influence on Predicted Performance of Jointed Concrete Pavement with Variations in Axle Load Spectra)

  • 이경배;권순민;이재훈;손덕수
    • 한국도로학회논문집
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    • 제16권1호
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    • pp.11-19
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    • 2014
  • PURPOSES : The purpose of this article is to investigate the predicted life of jointed concrete pavement (JCP) with two variables effecting on axle load spectra (ALS). The first variable is different data acquisition methods whether using high-speed weigh-in-motion (HS-WIM) or not and the other one is spectra distribution due to overweight enforcement on main-lane of expressway using HS-WIM. METHODS : Three sets of ALS had been collected i) ALS provided by Korea Pavement Research Program (KPRP), which had been obtained without using HS-WIM ii) ALS collected by HS-WIM before the enforcement at Kimcheon and Seonsan site iii) ALS collected after the enforcement at the same sites. And all ALS had been classified into twelve vehicle classes and four axle types to compare each other. Among the vehicle classes, class 6, 7, 10 and 12 were selected as the major target for comparing each ALS because these were considered as the primary trucks with a high rate of overweight loading. In order to analyze the performance of JCP based on pavement life, fatigue crack and International Roughness Index (IRI) were predicted using road pavement design program developed by KPRP and each ALS with same annual average daily traffic (AADT) was applied to design slab thickness. RESULTS : Comparison ALS of KPRP with those of HS-WIM shows that the ALS of KPRP has a low percentage of heavy spectra such as 6~9 tonnes for single axle, 18~21 tonnes for tandem axle and 27~30 tonnes for tridem axle than other two ALS of HS-WIM in most vehicle classes and axle types. It means that ALS of KPRP was underestimated. And after the enforcement, percentage of heavy spectra close to 10 tonnes per an axle are lowered than before the enforcement by the effect of overweight enforcement because the spectra are related to overweight regulation. Prediction results of pavement life for each ALS present that the ALS of HS-WIM collected before the enforcement makes the pavement life short more than others. On the other hand, the ALS of KPRP causes the longest life under same thickness of slab. Thus, it is possible that actual performance life of JCP under the traffic like ALS of HS-WIM could be short than predicted life if the pavement was designed based on ALS provided by KPRP. CONCLUSIONS : It is necessary to choose more reliable and practical ALS when designing JCP because ALS can be fairly affected by acquisition methods. In addition, it is important to extend performance life of the pavement in service by controlling traffic load such as overweight enforcement.