• Title/Summary/Keyword: 일계신뢰도법

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Reliability Analysis of Caisson Type Breakwater using Load Surface (하중면을 이용한 케이슨식 방파제의 신뢰성해석)

  • Kim, Dong-Hyawn
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.21 no.3
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    • pp.209-215
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    • 2009
  • A new load surface method for reliability of caisson type breakwater was proposed. Linear functions for horizontal wave force and uplift force were estimated by using water level and wave height then they were applied to the reliability analysis of breakwater using first order reliability method(FORM). In the numerical example, sliding and overturning failure probability of caisson type breakwater were analyzed by using load surface and they were compared with those by Monte Carlo simulation.

Reliability Analysis of Tripod Support Structure for Offshore Wind Turbine using Stress Concentration Factor (응력집중계수를 이용한 해상풍력터빈 트라이포드 지지구조물의 신뢰성해석)

  • Lee, Sang Geun;Kim, Dong Hyawn
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.28 no.2
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    • pp.92-100
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    • 2016
  • Reliability analysis of tripod support structure for offshore wind turbine was performed. Extreme distribution function of peak response due to wind and wave loads was estimated by applying peak over threshold(POT) method. Then, stress based limit state function was defined by using maximum stress of support structure which was obtained by multiplying beam stress and concentration factor. The reliability analysis result was compared when maximum stress was calculated from shell element. Reliability index was evaluated using first order reliability method(FORM).

Reliability Analysis Offshore Wind Turbine Support Structure Under Extreme Ocean Environmental Loads (극한 해양 환경하중을 고려한 해상풍력터빈 지지구조물의 신뢰성 해석)

  • Lee, Sang Geun;Kim, Dong Hyawn
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.26 no.1
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    • pp.33-40
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    • 2014
  • Reliability analysis of jacket type offshore wind turbine (OWT) support structure under extreme ocean environmental loads was performed. Limit state function (LSF) of OWF support structure is defined by using structural dynamic response at mud-line. Then, the dynamic response is expressed as the static response multiplied by dynamic response factor (DRF). Probabilistic distribution of DRF is found from response time history under design significant wave load. Band limited beta distribution is used for internal friction angle of ground soil. Wind load is obtained in the form of thrust force from commercial code called GH_Bladed and then, applied to tower hub as random load. In a numerical example, the response surface method (RSM) is used to express LSF of jacket type support structure for 5MW OWF. Reliability index is found using first order reliability method (FORM).

Reliability Based Design of Caisson type Quay Wall Using Partial Safety Factors (부분안전계수를 이용한 케이슨식안벽의 신뢰성설계법)

  • Kim, Dong-Hyawn;Yoon, Gil-Lim
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.21 no.3
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    • pp.224-229
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    • 2009
  • Partial safety factors(PSFs) for Level I reliability based design of caisson type quay walls were calculated. First order reliability method(FORM) based PSFs are the functions of sensitivities of limit state function with respect to design random variables, target reliability index, characteristic values and first moment of random variables. Modified PSFs for water level and resilient water level are newly defined to keep consistency with the current design code. In the numerical example, PSFs were calculated by using a target reliability index. Seismic coefficient is defined to show extreme distribution. It was found that PSFs for seismic coefficient becomes smaller as the return period for design seismic coefficient grows longer.

Reliability Analysis of Gravity-based Offshore Wind Turbine Foundation Considering Ocean Environmental Loads and Soil Uncertainty (해양환경하중 및 지반의 불확실성을 고려한 중력식 해상풍력 기초의 신뢰성 해석)

  • Lee, Sang Geun;Kim, Dong Hyawn
    • Journal of Ocean Engineering and Technology
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    • v.29 no.5
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    • pp.359-365
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    • 2015
  • A reliability analysis of the gravity-based foundation of anoffshore wind turbine was performed by considering the uncertainties of the design variables, including environmental loads. The limit state functions of the gravity-based foundation were defined using the response limits of the support structures suggested in the DNV standard. The wind load couldbe obtained using the GH_bladed software, and the wave load was calculated using the Morison equation. Then, the extreme distributions of the wind and wave loads were estimated by applying the peak over threshold (POT) method to the wind and wave load data. The probability distribution characteristics of the soil properties were defined with reference to a southwest coast geotechnical survey report. The reliability index was evaluated for each failure mode using a first-order reliability method.

Reliability Estimation of Static Design Methods for Driven Steel Pipe Piles in Korea (국내 항타강관말뚝 설계법의 신뢰성평가)

  • Huh, Jung-Won;Park, Jae-Hyun;Kim, Kyung-Jun;Lee, Ju-Hyung;Kwak, Ki-Seok
    • Journal of the Korean Geotechnical Society
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    • v.23 no.12
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    • pp.61-73
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    • 2007
  • As a part of Load and Resistance Factor Design(LRFD) code development in Korea, in this paper an intensive reliability analysis was performed to evaluate reliability levels of the two static bearing capacity methods for driven steel pipe piles adopted in Korean Standards for Structure Foundations by the representative reliability methods of First Order Reliability Method(FORM) and Monte Carlo Simulation(MCS). The resistance bias factors for the two static design methods were evaluated by comparing the representative measured bearing capacities with the design values. In determination of the representative bearing capacities of driven steel pipe piles, the 58 data sets of static load tests and soil property tests were collected and analyzed. The static bearing capacity formula and the Meyerhof method using N values were applied to the calculation of the expected design bearing capacity of the piles. The two representative reliability methods(FORM, MCS) based computer programs were developed to facilitate the reliability analysis in this study. Mean Value First Order Second Moment(MVFOSM) approach that provides a simple closed-form solution and two advanced methods of FORM and MCS were used to conduct the intensive reliability analysis using the resistance bias factor statistics obtained, and the results were then compared. In addition, a parametric study was conducted to identify the sensibility and the influence of the random variables on the reliability analysis under consideration.

Partial Safety Factors for Geotechnical Bearing Capacity of Port Structures (항만구조물 지반지지력 산정을 위한 부분안전계수 결정)

  • Yoon, Gil-Lim;Yoon, Yeo-Won;Kim, Hong-Yeon;Kim, Baeck-Oon
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.22 no.3
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    • pp.156-162
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    • 2010
  • When eccentric or inclined load acts on foundation of the port & harbor structures, partial safety factors of bearing capacity limit state were estimated using reliability analysis. Current Korean technical standards of port and harbor structures recommend to estimate the geotechnical bearing capacity using the simplified Bishop method. In practice, however, simple method of comparing ground reaction resistance with allowable bearing capacity has been mostly used by design engineers. While the simple method gives just one number fixed but somewhat convenient, it could not consider the uncertainty of soil properties depending on site by site. Thus, in this paper, partial safety factors for each design variable were determined so that designers do perform reliability-based level 1 design for bearing capacity limit state. For these, reliability index and their sensitivities were gained throughout the first order reliability method(FORM), and the variability of the random variables was also considered. In order to verify partial safety factors determined here, a comparison with foreign design codes was carried out and were found to be reasonable in practical design.

Probabilistic Optimization for Improving Soft Marine Ground using a Low Replacement Ratio (해상 연약지반의 저치환율 개량에 대한 확률론적 최적화)

  • Han, Sang-Hyun;Kim, Hong-Yeon;Yea, Geu-Guwen
    • The Journal of Engineering Geology
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    • v.26 no.4
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    • pp.485-495
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    • 2016
  • To reinforce and improve the soft ground under a breakwater while using materials efficiently, the replacement ratio and leaving periods of surcharge load are optimized probabilistically. The results of Bayesian updating of the random variables using prior information decrease uncertainty by up to 39.8%, and using prior information with more samples results in a sharp decrease in uncertainty. Replacement ratios of 15%-40% are analyzed using First Order Reliability Method and Monte Carlo simulation to optimize the replacement ratio. The results show that replacement ratios of 20% and 25% are acceptable at the column jet grouting area and the granular compaction pile area, respectively. Life cycle costs are also compared to optimize the replacement ratios within allowable ranges. The results show that a range of 20%-30% is the most economical during the total life cycle. This means that initial construction cost, maintenance cost and failure loss cost are minimized during total life cycle. Probabilistic analysis for leaving periods of shows that three months acceptable. Design optimization with respect to life cycle cost is important to minimize maintenance costs and retain the performance of the structures for the required period. Therefore, more case studies that consider the maintenance costs of soil structures are necessary to establish relevant design codes.