• Title/Summary/Keyword: 피로모형

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Development of Fatigue Model for Asphalt Black Base by Accelerated Pavement Testing (포장가속시험을 이용한 아스팔트 안정처리층의 피로모형 개발)

  • Yeo, In-Soo;Suh, Young-Chan;Mun, Sung-Ho
    • International Journal of Highway Engineering
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    • v.9 no.4
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    • pp.11-20
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    • 2007
  • This thesis develops a fatigue model for the asphalt black base using the APT(Accelerated Pavement Testing) and analyzes the correlation of the APT analysis result with results of previous laboratory tests. For the APT testing, aggregate of the maximum grain size of 25mm(BB-3) was used as the material for the asphalt black base. The result of the APT revealed that the variable of the fatigue model, i.e. the maximum tensile stress on the bottom part of the pavement, increased as the number of loading increased while the modulus of elasticity for the pavement layer decreased gradually. The tensile strain was obtained from a strain gauge, and it was used to derive the values of $k_1=1.29{\times}10^{-6}$ and $k_2=3.02$ from the basic equation of the asphalt fatigue model, $N_f=k_1(\frac{1}{\epsilon})^{k_2}$. The fatigue life predicted from the asphalt fatigue model was greater than that obtained from laboratory experiments, given the same tensile strain. Additionally, a theory to estimate the remaining life of the pavement was developed using FWD, a non-destructive experiment.

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Analysis of Fatigue Truck Model for LRFD Code (LRFD 설계기준(안) 피로설계트럭 모형 분석)

  • Cho, Eun Young;Shin, Dong Ku
    • Journal of Korean Society of Steel Construction
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    • v.21 no.3
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    • pp.331-342
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    • 2009
  • A reliability analysis of the fatigue failure of highway steel bridges was performed by applying the Miner's fatigue damage rule for the fatigue design truck proposed for the LRFD code and for the current DB 24 truck. The limit state function for fatigue failure is expressed as a function of various random variables that affect fatigue damage. Among these variables, the statistical parameters for the equivalent moment, the impact factor, and the loadometer were obtained by analyzing recently measured domestic traffic data, and the parameters for the fatigue strength, the girder distribution factor, and the headway factor were obtained from the measured data reported in literature. Based on the reliability analysis, the fatigue truck model for the LRFD code was proposed. After applying the proposed fatigue truck to the LRFD code, 16 composite plate and box girder bridges were designed based on the LRFD method, and the LRFD design results for the fatigue limit state were compared with those by the current KHBDC.

Development of Fatigue Model of Concrete Pavement Considering Environmental Loading (환경하중을 고려한 콘크리트 포장 피로모형의 개발)

  • Lim, Jin Sun;Kim, Yeon Bok;Jeong, Jin Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.6D
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    • pp.819-829
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    • 2008
  • Fatigue cracking occurs over long time period because dynamic strength of slab continuously decreases by vehicle loading repetitively applied to the concrete pavement. To more accurately predict the fatigue life of the concrete pavement, the stress due to environmental loading should be considered prior to calculating the stress due to the vehicle loading because the stress due to temperature and moisture distribution always exists within the slab. Accordingly, a new fatigue model considering the environmental loading was developed in this research by evaluating factors of existing fatigue models most widely used and by making data points from the models. The applicability of the new model was evaluated by performing a fatigue analysis on the general concrete pavement structure using local climatic and traffic conditions in Korea. It was concluded that the top-down cracking due to the tensile stress at top of the slab is dominant cause of the fatigue failure than the bottom-up cracking occurred at bottom of the slab. More advanced fatigue analysis considering vehicle speed is expected by developing this study.

Improvement of Fatigue Model of Concrete Pavement Slabs Using Environmental Loading (환경하중을 이용하는 콘크리트 포장 슬래브 피로모형의 개선)

  • Park, Joo-Young;Lim, Jin-Sun;Kim, Sang-Ho;Jeong, Jin-Hoon
    • International Journal of Highway Engineering
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    • v.13 no.4
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    • pp.103-115
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    • 2011
  • Concrete slab curls and warps due to the uneven distribution of temperature and moisture and as the result, internal stress develops within the slab. Therefore, environmental loads must be considered in addition to the traffic loads to predict the lifespan of the concrete pavement more accurately. The strength of the concrete slab is gradually decreases to a certain level at which fatigue cracking is generated by the repetitive traffic and environmental loadings. In this study, a new fatigue regression model was developed based on the results from previously performed studies. To verify the model, another laboratory flexural fatigue test program which was not used in the model development, was conducted and compared with the predictions of other existing models. Each fatigue model was applied to analysis logic of cumulative fatigue damage of concrete pavement developed in the study. The sensitivity of cumulative fatigue damage calculated by each model was analyzed for the design factors such as slab thickness, joint spacing, complex modulus of subgrade reaction and the load transfer at joints. As the result, the model developed in this study could reflect environmental loading more reasonably by improving other existing models which consider R, minimum/maximum stress ratio.

A Practical Model for the Fatigue Reliability Analysis of Steel Highway Bridges (강도로교의 피로신뢰성 해석을 위한 실용적 모형)

  • 신재철;장동일;이성재;조효남
    • Computational Structural Engineering
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    • v.1 no.1
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    • pp.113-122
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    • 1988
  • A practical model for predicting the risk of fatigue failure of steel highway bridges is developed in this study. The proposed model is derived from fatigue reliability methods by incorporating various factors which may affect the fatigue life of bridges. The fatigue reliability function is assumed to follow the Weibull distribution. The computational form of the Weibull is adopted from Ang-Munse's approach that includes all the statistical uncertainties of the fatigue life of steel members and the stress ranges under variable amplitude loadings. The model accounts for the variation in ADTT, the change in stress history and the effects of inspections, which may occur during the serivce life of bridges. Stress range histograms are collected from the random stress spectra based on the field measurements of an existing bridge, and, thus, the resulting stress range frequency distribution is modelled with a beta distribution. The results of applications of the proposed fatigue analysis methods to an existing bridge show that the proposed models with the computer program developed for numerical computations can be used as a practical tool for the fatigue rating or for the predictions of the remaining fatigue life of deteriorated existing steel bridges.

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Study on Fatigue Damage Model and Multi-Stress Level Fatigue Life Prediction of Composite Materials (II) -Fatigue Damage Model using Reference Modulus- (복합재료의 피로손상 모형 및 다응력 수위 피로수명 예측 연구 (II) - 참고계수를 이용한 피로 손상 모형 -)

  • 이창수;황운봉;한경섭
    • Composites Research
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    • v.12 no.2
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    • pp.62-69
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    • 1999
  • During fatigue loading of composite materials, damage accumulation can be monitored by measuring their material properties. In this study, fatigue modulus is used as the damage index. Fatigue life of composite materials may be predicted analytically using damage models which are based on fatigue modulus and resultant strain. Damage models are propesed as funtions of applied stress level, number of fatigue cycle and fatigue life. The predicted life was comparable to the experimental result obtained using E-glass fiber reinforced epoxy resin materials and pultruded glass fiber reinforce polyester composites under two-stress level fatigue loading.

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Optimum Designs of Fatigue Life Tests for Inverse Gaussian Distribution (역정규분포에 대한 피로수명시험의 최적설계)

  • 최규명;이낙영
    • The Korean Journal of Applied Statistics
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    • v.12 no.2
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    • pp.621-631
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    • 1999
  • 재료의 피로 파괴과정은 균열의 발생과 전파 및 성장의 과정을 거쳐 마침내 결정적 균열의 크기가 일정한도를 넘어서면 재료의 파괴가 일어난다. 이 때까지의 시간, 즉 피로 수명이 역정규분포를 따를 때 재료의 수명과 스트레스 수준과 관계를 나타 내는 S-N곡선에 대한 대수선형모형(log-linear model)을 제시하고, 이 모형하에서 피로수명시험에 대한 통계적 최적시험설계방법을 찾는다. 통계적 최적여부에 대한 판단기준으로 설계 스트레스 수준하의 특정 시점에서의 신뢰도에 대한 최우추정량의 점근분산을 최소화하는 방법을 사용하였다.

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A Study on Fatigue Safety Estimation of Cross Frame of Suspension Bridge(I) - Estimation by Nominal Stress - (현수교 횡프레임의 피로안전성 평가에 관한 연구(I) - 공칭응력에 의한 평가 -)

  • Kyung, Kab Soo;Jeon, Jun Chang;Su, Seok Ku;Yong, Hwan Sun
    • Journal of Korean Society of Steel Construction
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    • v.11 no.4 s.41
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    • pp.397-407
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    • 1999
  • In this paper, the fatigue safety in the suspension bridge is investigated by using nominal and variable stress, respectively. The technique on structural modeling and the fatigue evaluation using nominal stress are mainly dealt with in this paper. To make the finite element analysis model reflecting the actual structural behavior of the suspension bridge with cross frame, the parametric study is carried out. In this study, the influence of supporting condition. the difference of the results of 2- and 3-D analysis and the number of cross frames modelled in are considered. The nominal stress under the real traffic flow of the bridge is calculated by the combination of the stresses due to the unit DB-24 loading. The nominal stresses for details under consideration are compared with allowable stress ranges specified in the codes and the results are discussed.

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The Effects of Roll Misalignment Errors, Shooting Distance, and Vergence Condition of 3D Camera on 3D Visual Fatigue (시각피로 모형: 카메라의 회전오차, 촬영 거리, 수렴 조건이 입체 시각피로에 미치는 영향)

  • Li, Hyung-Chul O.;Park, JongJin;Kim, ShinWoo
    • Journal of Broadcast Engineering
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    • v.18 no.4
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    • pp.589-598
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    • 2013
  • In order to understand 3D visual fatigue, it is necessary to examine the visual fatigue induced by camera parameters as well as that induced by a pre-existing 3D content. In the present study, we examined the effects of camera parameters, such as roll misalignment error, shooting distance and vergence condition on 3D visual fatigue and we modelled it. The results indicate that roll misalignment error, shooting distance and vergence condition affect 3D visual fatigue and the effect of roll misalignment error on 3D visual fatigue is evident specifically when screen disparity is relatively small.