물류보관 랙선반시설물의 시스템신뢰성 해석

옥승용 ( Seung Yong Ok ),김동석 ( Dong Seok Kim ) 한국안전학회(구 한국산업안전학회) 2014 한국안전학회지 Vol.29 No.4

This study proposes a system reliability analysis of rack storage facilities subjected to forklift colliding events. The proposedsystem reliability analysis consists of two steps: the first step is to identify dominant failure modes that most contribute to the failure ofthe whole rack facilities, and the second step is to evaluate the system failure probability. In the first step, dominant failure modes areidentified by using a simulation-based selective searching technique where the contribution of a failure mode to the system failure isroughly estimated based on the distance from the origin in the space of the random variables. In the second step, the multi-scale systemreliability method is used to compute the system reliability where the first-order reliability method (FORM) is initially used to evaluatethe component failure probability (failure probability of one member), and then the probabilities of the identified failure modes and theirstatistical dependence are evaluated, which is called as the lower-scale reliability analysis. Since the system failure probability iscomprised of the probabilities of the failure modes, a higher-scale reliability analysis is performed again based on the results of thelower-scale analyses, and the system failure probability is finally evaluated. The illustrative example demonstrates the results of thesystem reliability analysis of the rack storage facilities subjected to forklift impact loadings. The numerical efficiency and accuracy of theapproach are compared with the Monte Carlo simulations. The results show that the proposed two-step approach is able to provideaccurate reliability assessment as well as significant saving of computational time. The results of the identified failure modes additionallylet us know the most-critical members and their failure sequence under the complicated configuration of the member connections.

Reliability Estimation of Buried Gas Pipelines in terms of Various Types of Random Variable Distribution

Lee Ouk Sub,Kim Dong Hyeok The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.6

This paper presents the effects of corrosion environments of failure pressure model for buried pipelines on failure prediction by using a failure probability. The FORM (first order reliability method) is used in order to estimate the failure probability in the buried pipelines with corrosion defects. The effects of varying distribution types of random variables such as normal, lognormal and Weibull distributions on the failure probability of buried pipelines are systematically investigated. It is found that the failure probability for the MB31G model is larger than that for the B31G model. And the failure probability is estimated as the largest for the Weibull distribution and the smallest for the normal distribution. The effect of data scattering in corrosion environments on failure probability is also investigated and it is recognized that the scattering of wall thickness and yield strength of pipeline affects the failure probability significantly. The normalized margin is defined and estimated. Furthermore, the normalized margin is used to predict the failure probability using the fitting lines between failure probability and normalized margin.

Identification of Primary Failure Modes of Tunnel System and Influence of Supporting Structures on Tunnel System Reliability using Multiple Response Surfaces

Zhiliang Liu,Liang Li,Guangming Yu,Jun Hu,Houlai Lin,Chunli Li,Shibao Lu,Kaiqi Meng,Jun Lei 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

A method of calculating the failure probability of the tunnel system combining finite element numerical simulation with multiple response surface method (MRSM) and Monte-Carlo simulation (MCS) is presented. The applicability of the proposed methodology is verified through a subway interval soft rock tunnel in Qingdao, China. The sensitivity of Monte-Carlo sampling number and coefficients of variation for rock masses on the failure probability of tunnel system is conducted. The primary failure modes in tunnel system are identified by reanalyzing the failure samples. The simulation results demonstrate that the failure probability of a tunnel system within soft upper and hard lower surrounding rock mass is mainly attributed to the soft upper part of the surrounding rock. The coefficients of variation of the elastic modulus E1 and the internal friction angle ϕ1 of the pebble layer (soft upper part) have significant effect on the failure probability. The failure probability of tunnel system increases as the coefficients of variation of E1 and ϕ1 increase. Two primary failure modes are found to contribute to the tunnel system reliability. The effect of rock bolt length L and pipe-roof thickness H on tunnel system reliability and two primary failure modes as well are investigated. The simulation results indicate that both the enhancements in L and H tend to be more effective than the enhancement in either L or H if a small target failure probability of tunnel system is expected. The supporting structures design can be performed based on the potential sets of (L, H) satisfying target failure probability.

심층혼합처리공법이 적용된 항만 구조물의 파괴확률과위험도 평가에 관한 사례 연구

김병일,박언상 한국지반신소재학회 2018 한국지반신소재학회 논문집 Vol.17 No.4

본 연구에서는 안정성과 위험도 평가의 중요성이 증대되고 있는 DCM(Deep Cement Mixing, 이하 DCM) 보강 지반상의항만 구조물에 대하여 위험도 평가를 위한 파괴확률을 산정하였다. DCM 개량 지반의 위험도에 영향을 미치는 확률변수로개량체의 설계기준강도와 시공중첩, 원지반의 강도 및 내부마찰각, 개량지반의 단위중량을 선정하고 관련 통계치를 산정하여적용하였다. 또한, 상시 조건과 지진시 조건에서의 전체 시스템에 대한 파괴확률을 분석하였다. 본 연구를 통해 DCM 개량지반의 위험도 평가를 위한 확률변수에서 변동계수가 가장 큰 것은 설계기준강도이나 안전율의 변동성 즉, 시스템의 위험도에는큰 영향을 미치지는 않는 것을 알 수 있었다. DCM 보강 지반에 대한 시스템의 파괴확률 영향인자 즉, 주된 위험요소는 상시및 지진시 모두 외적안정의 경우 수평활동, 내적안정의 경우 압축파괴인 것으로 평가되었다. 또한, 수평활동에 대해서는 상시파괴확률이 지진시 파괴확률보다 높고 압축파괴에 대해서는 상시 파괴확률이 지진시 파괴확률보다 낮은 것으로 나타났다. 전체 시스템의 상시 파괴확률과 지진시 파괴확률은 유사하지만, 본 사례의 경우 지진시 위험도가 다소 높은 것으로 나타났다. In this study, the evaluation to probability of failure for risk assessment of port structures on DCM reinforced soils, where stability and risk assessment are increasing in importance, was performed. As a random variables affecting the risk of DCM improved ground, the design strength, superposition (overlap) of construction, strength of the natural ground, internal friction angle and unit weight of the modified ground were selected and applied to the risk assessment. In addition, the failure probability for the entire system under ordinary conditions and under earthquake conditions were analyzed. As a result, it was found that the highest coefficient of variation in the random variable for the risk assessment of the DCM improved ground is the design strength, but this does not have a great influence on the safety factor, ie, the risk of the system. The main risk factor for the failure probability of the system for the DCM reinforced soils was evaluated as horizontal sliding in case of external stability and compression failure in case of internal stability both at ordinary condition and earthquake condition. In addition, the failure probability for ordinary horizontal sliding is higher than that for earthquake failure, and the failure probability for ordinary compression failure is lower than that for earthquake failure. The ordinary failure probability of the entire system is similar to the failure probability on earthquake condition, but in this case, the risk of earthquake is somewhat higher.

한국 펀드 시장에서의 생존분석에 관한 연구

김성신(Sungsin Kim) 대한경영학회 2016 大韓經營學會誌 Vol.29 No.12

파괴확률을 활용한 항 외곽시설 Hybrid 설계법에 관한 제언

조용준(Yong Jun Cho) 한국연안방재학회 2021 한국연안방재학회지 Vol.8 No.4

Lately, many efforts have been made to address the problem concerned with deterministic design using reliability-based design, and the research results are significant. However, there is considerable confusion in the design practice regarding how to use failure probability, the main output of reliability-based design. In this rationale, this study aims to develop a robust hybrid deterministic design method for outer port facilities using the failure probability. To this end, we first reviewed the design process of Eulleungdo East Breakwater, some of which were recently damaged. It was revealed that the exceeding probability of design wave height of 5.2 m was merely 0.65, which corresponds to a return period of 1.53 years, showing that the outer port facilities of Ulleungdo were considerably underdesigned. In an effort to find an alternative that can overcome the limitations of the deterministic design method, which is highly likely to involve subjective judgment, a Level III reliability design was carried out. In doing so, tri-modal Gaussian wave slope distribution was used as a probabilistic model for wave slope. Numerical results show that failure probability was excessively estimated in the Gaussian distribution, and even if the TTP size was slightly reduced, the failure probability increased rapidly. Although failure probability is sensitive to the change in nominal diameter, there is a gradually increasing zone where the failure probability change rapidly decreases when the nominal diameter is larger than the critical value. The presence of a Gradually Increasing Zone mentioned above implies that it is uneconomical and has no physical background to adjust the nominal diameter to be larger than the critical value. Therefore, it can be easily conceived that outer port facility design should be performed using a failure probability provided by Level III reliability-based design.

토사 적체에 따른 우수관의 성능불능확률

권혁재 대한상하수도학회 2010 상하수도학회지 Vol.24 No.5

Statistical distribution of annual maximum rainfall intensity of 18 cities in Korea was analyzed and applied to the reliability model which can calculate the probability of performance failure of storm sewer. After the analysis, it was found that distribution of annual maximum rainfall intensity of 18 cities in Korea is well matched with Gumbel distribution. Rational equation was used to estimate the load and Manning's equation was used to estimate the capacity in reliability function to calculate the probability of performance failure of storm sewer. Reliability analysis was performed by developed model applying to the real storm sewer. It was found that probability of performance failure is abruptly increased if the diameter is smaller than certain size. Therefore, cleaning the inside of storm sewer to maintain the original diameter can be one of the best ways to reduce the probability of performance failure. In the present study, probability of performance failure according to accumulation of debris in storm sewer was calculated. It was found that increasing the amount of debris seriously decrease the capacity of storm sewer and significantly increase the probability of performance failure.

상수관망의 신뢰도 산정을 위한 개별 관의 파괴 확률을 고려한 상수관 파괴모의 기법

전환돈,Jun. Hwandon 한국방재학회 2012 한국방재학회논문집 Vol.12 No.4

상수관망의 신뢰도 산정은 상수관망의 정확한 운영상황을 파악하기 위해서 중요지만 널리 받아들여지는 상수관망의 신뢰도 산정을 위한 방법은 없다. 관파괴와 이에 따른 영향을 바탕으로 한 Jun 등이 제안한 모델은 상수관망의 운영주체에서 실질적으로 활용이 가능한 기법이다. 그러나, Jun 등의 모델에서는 각 관의 파괴확률을 같게 설정하여 관파괴 모의를 실시하였기 때문에 실제 상수관망에서 발생하는 관파괴 양상을 정확하게 반영하지 못하였다. 따라서 본 연구에서는 각각의 관별 파괴확률을 고려하여 관파괴 모의를 가능케 Jun 등의 모델을 개선하여 상수관망의 신뢰도를 산정할 수 있는 모델을 제안하였다. 각각의 관별 파괴확률을 관경과 관길이를 바탕으로 산정하는 회귀식을 이용하여 산정한 후 이를 상수관망 신뢰도 산정을 위한 관파괴 모의에 적용하였다. 제안된 모델을 실제 상수관망에 적용하여 Jun 등의 모델과 본 연구에서 제안된 모델에 의해 산정되는 상수관망의 신뢰도를 비교하였다. 비교 결과 개별 관의 관파괴 확률을 반드시 고려하여야만 정확한 상수관망의 신뢰도 산정이 가능한 것으로 나타났다. Estimation of the reliability of a Water Distribution System(WDS) is important to understand the current operating condition of the system. Although, there is no widely accepted method to estimate the reliability of a WDS, the Jun`s model which is based on the pipe failure simulation and its impact can be efficiently adopted for the purpose by the water utility. In the model, however, it is assumed that the pipe failure probability of each pipe is even and this assumption may bring unrealistic estimation of the reliability of a WDS since with this assumption, the actual pipe failure characteristics occurred in the WDS cannot be simulated. For this reason, in this study, we suggest a modified method of the Jun`s model to consider the individual pipe`s failure probability. The regression equation which is based on diameter and length of the pipe is used to estimate the failure probability of the individual pipe and then, the pipe failure simulation is performed. The suggested model is applied to a real WDS to compare the results of the two models. Comparing them, it is concluded that the failure probability of the individual pipe should be considered to estimate the accurate reliability of a WDS when it is estimated by the pipe failure simulation.

매설배관의 파손압력기준 모델의 경계조건이 신뢰성 평가에 미치는 영향

이억섭(Ouk Sub Lee),편장식(Jang Sik Pyun) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

This paper presents the effect of boundary condition of failure pressure model for buried pipelines on failure prediction by using a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with each corrosion defect for long exposure periods in year. A failure pressure model based on a failure function composed of failure pressure and operation pressure is adopted for the assessment of pipeline failure. The effects of random variables Such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically studied by using a failure probability model for the corrosion pipeline.

사면의 구역 및 절리의 연장성을 고려한 암반사면의 안정성 확률해석

장보안 ( Bo An Jang ),성숙경 ( Suk Kyung Sung ),장현식 ( Hyun Sic Jang ) 대한지질공학회 2010 지질공학 Vol.20 No.2

사면의 안정성 분석에 결정론적인 방법이 최근까지 많이 사용되어 왔으나, 암반의 불확실성과 가변성을 고려하는 확률론적인 방법이 더욱 효과적인 것으로 알려지면서 확률론적인 방법의 사용이 점차 증가하는 추세이다. 그러나 현재까지의 방법들은 절리의 특성이나 암반의 풍화 특성 등과 같은 암반의 특성이 사면 전체에서 균질한 것으로 가정하고 있으며, 암반 사면의 파괴에 가장 결정적인 변수인 절리의 연장성을 고려하지 않은 상태에서 안전율 혹은 파괴확률을 계산하여 사면의 안정성을 분석하고 있어서 정확한 사면 안정성 분석에 한계를 보이고 있는 실정이다. 이 연구에서는 모델 사면을 설정한 후, 사면이 균질하다고 가정한 경우와 사면을 암반 및 절리의 상태에 따라 구역으로 분할한 경우의 파괴확률을 계산하여 비교하였고, 또한 위의 각각의 경우에 절리의 연장성을 변수로 고려한 파괴확률을 계산하였다. 또한 강원도 홍천군에 위치한 사면을 구역으로 분할한 후 절리의 연장성을 고려한 파괴확률을 계산하여 모델 분석의 적용성을 검증하였다. In analysis of slope stability, deterministic analysis which yields a factor of safety has been used until recently. However, probability of failure is considered as a more efficient method because it deals with the uncertainty and variability of rock mass. In both methods, a factor of safety or a probability of failure is calculated for a slope although characteristics of rock mass, such as characteristics of joints, weathering degree of rock and so on, are not uniform throughout the slope. In this paper, we divided a model slope into several zones depending on conditions of rock mass and joints, and probabilities of failure in each zone are calculated and compared with that calculated in whole slope. The persistence of joint was also used as a parameter in calculation of probability of failure. A rock slope located in Hongcheon, Gangwondo was selected and the probability of failure using zoning and persistence as parameter was calculated to confirm the applicability of model analysis.