• Title/Summary/Keyword: 일계이차 모멘트법

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Reliability-Based Service Life Estimation of Concrete in Marine Environment (신뢰성이론에 기반한 해양환경 콘크리트의 내구수명 평가)

  • Kim, Ki-Hyun;Cha, Soo-Won
    • Journal of the Korea Concrete Institute
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    • v.22 no.4
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    • pp.595-603
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    • 2010
  • Monte-Carlo simulation technique is often used in order to predict service life of concrete structure subjected to chloride penetration in marine environment based on probability theory. Monte-Carlo simulation method, however, the method gives different results every time that the simulation is run. On the other hand, moment method, which is frequently used in reliability analysis, needs negligible computational cost compared with simulation technique and gives a constant result for the same problem. Thus, in this study, moment method was applied to the calculation of corrosion-initiation probability. For this purpose, computer programs to calculate failure probabilities are developed using first-order second moment (FOSM) and second-order second moment (SOSM) methods, respectively. From the analysis examples with the developed programs, SOSM was found to give a more accurate result than FOSM does. The sensitivity analysis has shown that the factor affecting the corrosion-initiation probability the most was the cover depth, and the corrosion-initiation probability was influenced more by its coefficient of variation than its mean value.

A Study on the Design Sea-state Determination Using the IFOSM Method (역 일계이차 모멘트법을 이용한 설계 해상상태의 결정에 관한 연구)

  • Lee, Jae-Ohk;Rho, Jun-Bumn
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.3
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    • pp.447-453
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    • 2010
  • Response-based approach is getting more preferred in determining the design sea-state for offshore structures because traditional environment-based approach is known to yield a much conservative design condition. This paper introduces the inverse first-order second-moment (IFOSM) method as a response-based approach, which is expected to give a more feasible design condition at the cost of reasonable number of motion analyses. The IFOSM method is based on the theory of probability and adopts an optimization scheme to determine the design point. Both the design maximum response and design sea state can be obtained straightforwardly from the optimum. The IFOSM method has been applied to a turret-moored FPSO's design problem and showed its effectiveness in practical use.

Matrix Structure Reliability Analysis using AFORM (개선된 일계이차모멘트법을 적용한 메트릭스 구조물 신뢰도 해석)

  • Lee, Seung-Gyu;Kim, Tae-Uk;Kim, Sung-Chan;Ahn, Lee-Ki
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.20 no.3
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    • pp.51-56
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    • 2012
  • The wing is a framework composed chiefly of skin, spars, ribs and can be simplified by matrix structure. In this paper, a displacement reliability of matrix structure is analysed by AFORM(Advanced First Order Reliability Method) and applicability is assessed.

Sensitivity Analysis of Parameters Affecting Seismic Response for RC Shear Wall with Age-Related Degradation (경년열화된 철근콘크리트 전단벽의 지진응답에 영향을 미치는 변수들의 민감도분석)

  • Park, Jun-Hee;Choun, Young-Sun;Choi, In-Kil
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.4
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    • pp.391-398
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    • 2011
  • After a concrete is poured, reinforced concrete structures were distressed by physical and chemical factor over time. It is in need to define important variables related to structural behavior for effectively conducting seismic analysis of structures with age-related degradation. In this study, a sensibility analysis using the first-order second moment method was performed to analyze an important variables for the reinforced concrete shear wall with age-related degradation. Because the seismic capacity of aging structures without a concrete hardening effect can be underestimated, the sensibility of analysis variables was analyzed according to the concrete hardening. Important variables for RC shear wall with age-related degradation was presented by using the tornado diagram.

Application of Probabilistic Fracture Mechanics Methodology (확률론적 파괴역학 수법의 적용성 검토)

  • 이준성;곽상록;김영진
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.667-670
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    • 2001
  • For major structural components periodic inspections and integrity assessments are needed for the safety. However, many flaws are undetectable because sampling inspection is carried out during in-service inspection. Probabilistic integrity assessment is applied to take into consideration of uncertainty and variance of input parameters arise due to material properties and undetectable cracks. This paper describes a Probabilistic Fracture Mechanics(PEM) analysis based on the Monte Carlo(MC) algorithms. Taking a number of sampling data of probabilistic variables such as fracture toughness value, crack depth and aspect ratio of an initial surface crack, a MC simulation of failure judgement of samples is performed. For the verification of this analysis, a comparison study of th PFM analysis using a commercial code, mathematical method is carried out and a good agreement was observed between those results.

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Flexural Reliability Assessment of PSC-I Girder Rail Bridge Under Operation (사용중 PSC-I 거더 철도 교량의 휨모멘트에 대한 신뢰도 분석)

  • Kim, Ki Hyun;Yeo, Inho;Sim, Hyoung-Bo
    • Journal of the Korean Society for Railway
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    • v.19 no.2
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    • pp.187-194
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    • 2016
  • It is necessary to determine reliability indexes of existing railway bridges prior to setting up a proper target reliability index that can be used to introduce a reliability based limit state design method to design practice. Reliability is evaluated for a six PSC-I girder railway bridge, which is one of many representative types of double-track railway bridges. The reliability assessment is carried out for an edge girder subjected to bending moment. In the assessment, the flexural resistance and the fixed-load effect were obtained using existing statistical values from previous research on the introduction of limit state design to road bridge design. On the other hand, the live-load effect was determined using statistical values obtained from field measurement for the Joong-ang corridor, on which heavy freight trains are frequently passing. The reliability assessment is performed by AFOSM(Advanced First Order Second Moment method) for the limit state equation, and a sensitivity analysis for the reliability is performed for each factor of the load and resistance effects.

Studies on Probabilistic Nonlinear First Ply Failure Loads and Buckling Loads of Laminated Composite Panels (적층복합재료 패널의 확률론적 비선형 초기파단하중 및 좌굴하중에 관한 연구)

  • Bang, Je-Sung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.6
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    • pp.1-10
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    • 2013
  • Probabilistic nonlinear first ply failure loads of flat composite panels and nonlinear buckling loads of curved composite panels with cutouts are estimated to provide the more reliable main load carrying structure in the renewable energy industry and offshore structures. The response surface method approximates limit state surface to a second order polynomial form of random variables with the results of deterministic finite element analyses at given sampling design points. Furthermore, the iterative linear interpolation scheme is used to obtain a more accurate approximation of the limit state surface near the most probable failure point (MPFP). The advanced first order second moment method and the Monte Carlo method are performed on an approximated limit state surface to evaluate the probability of failure. Finally, the sensitivity of the reliability index with respect to transformed random variables is investigated to figure out the main random variables that have an effect on failures.

Reliability Analysis of Chloride Ion Penetration based on Level II Method for Marine Concrete Structure (해양 콘크리트 구조물에 대한 Level II 수준에서의 염소이온침투 신뢰성 해석)

  • Han, Sang-Hun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.6
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    • pp.129-139
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    • 2008
  • Due to uncertainty of numerous variables in durability model, a probalistic approach is increasing. Monte Carlo simulation (Level III method) is an easily accessible method, but requires a lot of repeated operations. This paper evaluated the effectiveness of First Order Second Moment method (Level II method), which is more convenient and time saving method than MCS, to predict the corrosion initiation in harbor concrete structure. Mean Value First Order Second Moment method (MV FOSM) and Advanced First Order Second Moment method (AFOSM) are applied to the error function solution of Fick's second law modeling chloride diffusion. Reliability index and failure probability based on MV FOSM and AFOSM are compared with the results by MCS. The comparison showed that AFOSM and MCS predict the similar reliability index and MV FOSM underestimates the probability of corrosion initiation by chloride attack. Also, the sensitivity of variables in durability model to corrosion initiation probability was evaluated on the basis of AFOSM. The results showed that AFOSM is a simple and efficient method to estimate the probability of corrosion initiation in harbor structures.

Application of Probabilistic Fracture Mechanics Technique Using Monte Carlo Simulation (몬테카를로 시뮬레이션을 이용한 확률론적 파괴역학 수법의 적용성 검토)

  • Lee, Joon-Seong;Kwak, Sang-Log;Kim, Young-Jin
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.10
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    • pp.154-160
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    • 2001
  • For major structural components periodic inspections and integrity assessments are needed for the safety. However, many flaws are undetectable because sampling inspection is carried out during in-service inspection. Probabilistic integrity assessment is applied to take into consideration of uncertainty and variance of input parameters arise due to material properties and undetectable cracks. This paper describes a Probabilistic Fracture Mechanics(PFM) analysis based on the Monte Carlo(MC) algorithms. Taking a number of sampling data of probabilistic variables such as fracture toughness value, crack depth and aspect ratio of an initial surface crack, a MC simulation of failure judgement of samples is performed. for the verification of this analysis, a comparison study of the PFM analysis using a commercial code, mathematical method is carried out and a good agreement was observed between those results.

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A Comparative Study on Probabilistic Structural Design Optimization (확률론적 구조설계 최적화기법에 대한 비교연구)

  • 양영순;이재옥
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.14 no.2
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    • pp.213-224
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    • 2001
  • 확률론적 구조설계 최적화는 구조물의 역학적 특성이나 하중의 불확실성이나 임의성과 같은 변동성을 정량적이고 합리적으로 고려할 수 있다는 점에서 기존의 전통적인 확정론적 최적화와 비교된다. 확률론적 최적화의 방법론으로는 개선된 일계이차모멘트법을 이용하는 신뢰도지수에 기반한 접근법(MPFP search)이 널리 알려져 있으며, 최근 목표성능치에 기반한 접근법(MPTP search)이 새롭게 제안되었다. 본 논문에서는 이들 두 가지 접근법에 대한 정식화를 수행하고, 특히 탐색과정에서 소모적인 반복계산을 발견하고 제거하는 알고리즘을 제시하였다. 예제에서 두 접근법에 의한 확률론적 최적화를 수행하고 구조설계 최적화의 관점에서 두 접근법의 장단점을 비교·검토하였다.

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