• Title, Summary, Keyword: reliability index

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Development of LCCA Module Using STEP-based LCCA Data Structure (STEP 기반 LCC 분석 데이터구조를 이용한 LCC 분석모듈 개발)

  • Kim, Dong-Hyun;Huang, Meng-Gang;Kim, Bong-Geun;Lee, Sang-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.803-808
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    • 2007
  • LCCA module enabling to estimate LCC and analyze time-variant reliability index of a plate girder bridge was developed. The developed module was based on the designed data structure following the standardized methodology of ISO/STEP, LCCA module consisted of LCC estimation module, which is composed of six sub modules according to the cost category, and reliability index analysis module, which is composed of time-variant corrosion sub module, time-variant live load sub module, and element reliability analysis sub module, The effectiveness of the developed LCCA module was verified by estimating LCC and analyzing time-variant reliability index of a plate girder bridge on the basis of the constructed test database.

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Optimization of trusses under uncertainties with harmony search

  • Togan, Vedat;Daloglu, Ayse T.;Karadeniz, Halil
    • Structural Engineering and Mechanics
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    • v.37 no.5
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    • pp.543-560
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    • 2011
  • In structural engineering there are randomness inherently exist on determination of the loads, strength, geometry, and so on, and the manufacturing of the structural members, workmanship etc. Thus, objective and constraint functions of the optimization problem are functions that depend on those randomly natured components. The constraints being the function of the random variables are evaluated by using reliability index or performance measure approaches in the optimization process. In this study, the minimum weight of a space truss is obtained under the uncertainties on the load, material and cross-section areas with harmony search using reliability index and performance measure approaches. Consequently, optimization algorithm produces the same result when both the approaches converge. Performance measure approach, however, is more efficient compare to reliability index approach in terms of the convergence rate and iterations needed.

Development of Methodology of New Effective Installed Reserve Rate considering Renewable Energy Generators (신재생에너지전원을 고려한 새로운 유효설비예비율 평가방법의 개발)

  • Park, Jeong-Je;Choi, Jae-Seok
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.1
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    • pp.26-32
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    • 2010
  • This paper proposes a new effective installed reserve rate in order to evaluate reliability of power system considering renewable generators, which include uncertainty of resource supply. It is called EIRR(effective installed reserve rate) in this paper. It is developed with considering capacity credit based on ELCC by using LOLE reliability criterion. While the conventional installed reserve rate index yields over-evaluation reliability of renewable generators, the proposed EIRR describes actual effective installed reserve rate. However, it is not the probabilistic reliability index as like as LOLE or EENS but another deterministic effective reliability index. The proposed EIRR is able to evaluate the realistic contribution to the reliability level for power system considering wind turbine generators and solar cell generators with high uncertainty in resource supply. The case study in model system as like as Jeju power system size presents a possibility that the proposed EIRR can be used practically as a new deterministic reliability index for generation expansion planning or operational planning in future.

Reliability-Based Topology Optimization for Structures with Stiffness Constraints (강성구속 조건을 갖는 구조물의 신뢰성기반 위상최적설계)

  • Kim, Sang-Rak;Park, Jae-Yong;Lee, Won-Goo;Yu, Jin-Shik;Han, Seog-Young
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.6
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    • pp.77-82
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    • 2008
  • This paper presents a Reliability-Based Topology Optimization(RBTO) using the Evolutionary Structural Optimization(ESO). An actual design involves some uncertain conditions such as material property, operational load and dimensional variation. The Deterministic Topology Optimization(DTO) is obtained without considering the uncertainties related to the uncertainty parameters. However, the RBTO can consider the uncertainty variables because it has the probabilistic constraints. In order to determine whether the probabilistic constraints are satisfied or not, simulation techniques and approximation methods are developed. In this paper, the reliability index approach(RIA) is adopted to evaluate the probabilistic constraints. In order to apply the ESO method to the RBTO, sensitivity number is defined as the change in the reliability index due to the removal of the ith element. Numerical examples are presented to compare the DTO with the RBTO.

An improved response surface method for reliability analysis of structures

  • Basaga, Hasan Basri;Bayraktar, Alemdar;Kaymaz, Irfan
    • Structural Engineering and Mechanics
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    • v.42 no.2
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    • pp.175-189
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    • 2012
  • This paper presents an algorithm for structural reliability with the response surface method. For this aim, an approach with three stages is proposed named as improved response surface method. In the algorithm, firstly, a quadratic approximate function is formed and design point is determined with First Order Reliability Method. Secondly, a point close to the exact limit state function is searched using the design point. Lastly, vector projected method is used to generate the sample points and Second Order Reliability Method is performed to obtain reliability index and probability of failure. Five numerical examples are selected to illustrate the proposed algorithm. The limit state functions of three examples (cantilever beam, highly nonlinear limit state function and dynamic response of an oscillator) are defined explicitly and the others (frame and truss structures) are defined implicitly. ANSYS finite element program is utilized to obtain the response of the structures which are needed in the reliability analysis of implicit limit state functions. The results (reliability index, probability of failure and limit state function evaluations) obtained from the improved response surface are compared with those of Monte Carlo Simulation, First Order Reliability Method, Second Order Reliability Method and Classical Response Surface Method. According to the results, proposed algorithm gives better results for both reliability index and limit state function evaluations.

New Approaches for Calibrating Material Factors of Reinforced Concrete Members in Korean Highway Bridge Design Code (Limit State Design) and Reliability Analysis (도로교설계기준(한계상태설계법)의 콘크리트부재 설계를 위한 재료계수 결정법 및 신뢰도 분석)

  • Lee, Hae Sung;Song, Sang Won;Kim, Ji Hyeon
    • Journal of The Korean Society of Civil Engineers
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    • v.39 no.1
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    • pp.13-24
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    • 2019
  • This paper brings up fallacy of material factors specified for the design of concrete members in the current Korean limit state design code for highway bridges, and proposes new material factors based on a robust optimization scheme to overcome the fallacy. It is shown that the current load factors in the code and the proposed material factors lead to a much higher reliability index than the target index. The load factors are adjusted to yield the target reliability index using the inverse reliability analysis. A reliability-based approach following the basic concept of Eurocode is formulated to determine material factors as well as load factors. The load-material factors obtained by the proposed reliability-based approach yield a lower reliability level than the target index. Drawbacks of the basic concept of Eurocode are discussed. It is pointed out that differences in the uncertainties between materials and members may cause the lower reliability index of concrete member than the target.

Reliability analysis of circular tunnel with consideration of the strength limit state

  • Ghasemi, Seyed Hooman;Nowak, Andrzej S.
    • Geomechanics and Engineering
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    • v.15 no.3
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    • pp.879-888
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    • 2018
  • Probability-based design codes have been developed to sufficiently confirm the safety level of structures. One of the most acceptable probability-based approaches is Load Resistance Factor Design (LRFD), which measures the safety level of the structures in terms of the reliability index. The main contribution of this paper is to calibrate the load and resistance factors of the design code for tunnels. The load and resistance factors are calculated using the available statistical models and probability-based procedures. The major steps include selection of representative structures, consideration of the limit state functions, calculation of reliability for the selected structures, selection of the target reliability index and calculation of load factors and resistance factors. The load and resistance models are reviewed. Statistical models of resistance (load carrying capacity) are summarized for strength limit state in bending, shear and compression. The reliability indices are calculated for several segments of a selected circular tunnel designed according to the tunnel manual report (Tunnel Manual). The novelty of this paper is the selection of the target reliability. In doing so, the uniform spectrum of reliability indices is proposed based on the probability paper. The final recommendation is proposed based on the closeness to the target reliability index.

Reliability and Validity of the Diet Quality Index for 7-9-year-old Indian Children

  • Chamoli, Ritushri;Jain, Monika;Tyagi, Gargi
    • Pediatric Gastroenterology, Hepatology & Nutrition
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    • v.22 no.6
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    • pp.554-564
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    • 2019
  • Purpose: This study verified the reliability and validity of the Diet Quality Index for Indian children (DQIIC). Methods: The study sample included 100 school going boys and girls (7-9 years). The dietary behavior of children was studied using a questionnaire and 24-hour dietary recall. The DQIIC comprises 21 items which aimed to assess the diet of Indian children on the basis of variety, adequacy of consumption of dietary components, and moderation in the amount of nutrients that are associated with diseases and dietary habits. The reliability of the DQIIC was assessed using the split half method, Cronbach's alpha, and test retest reliability. Content validity was evaluated using content validity ratio (CVR). Results: The intake of iron was found to be less than the recommended dietary allowances. There was frequent consumption of empty calorie packaged foods and higher than the recommended amount of sodium. Reliability of the DQIIC was 0.85 by split half method and the correlation coefficient for test retest reliability was 0.87. Cronbach's alpha was 0.62 and CVR was 0.85 for this index. Most of the children fell in the moderately healthy category. Conclusion: The DQIIC is a reliable and valid tool to assess the diet quality of Indian children between 7-9 years.

Validity and Reliability of Korean Version of the Revised Stress Appraisal Measure (RSAM) (한국어판 수정된 스트레스 평가 도구(Revised Stress Appraisal Measure)의 타당도와 신뢰도)

  • Kim, Jeong Sun;Kim, Kye-Ha;Kang, Hyuncheol
    • The Journal of the Korea Contents Association
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    • v.15 no.3
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    • pp.290-302
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    • 2015
  • The study purpose was to test the validity and reliability of the Korean version of the Revised Stress Appraisal Measure (RSAM) to assess stress appraisal in undergraduate students. Internal consistency reliability, construct and criterion validity were calculated using IBM SPSS Statistics 21 and AMOS 21 program. Survey data were collected from a convenience sample of 296 undergraduate students enrolled in five universities in G city and C area, South Korea. The Korean version of RSAM categorized into 5 factors explaining 68.4% of the total variance. The model of five subscales was validated by confirmatory factor analysis (p<.001, Goodness of Fit Index, Adjusted Goodness of Fit Index, Normed Fit Index, Comparative Fit Index >.08, Root Mean Square Error of Approximation=.056). In criterion validity, the scores for the scale were significantly correlated with the Perceived Stress Scale-Korean. Cronbach's alpha coefficient for the 19 items was .73~.89. The Korean RSAM showed satisfactory construct and criterion validity and reliability. Thus it may be an appropriate instrument for measuring stress appraisal in Korean university students.