부하의 전압 내성 특성을 고려한 순간전압강하 평가 연구

채하경(Hakyung Chae),박창현(Chang-Hyun Park) 대한전기학회 2021 전기학회논문지 Vol.70 No.2

This paper presents a novel method to assess voltage sags by taking into account the voltage tolerance characteristic of loads. In general, the tolerance characteristic is expressed in the form of a two-dimensional curve of voltage magnitude and duration. Also, the shape of characteristic curves depend on the type of loads. In order to estimate the expected sag frequency affecting sensitive loads, it is necessary to perform a voltage sag assessment considering the voltage tolerance curves of loads. However, because most existing methods of voltage sag assessment only focus on voltage sag magnitudes, these methods have limitations in reflecting various types of tolerance curves. In this paper, an effective method for reflecting various thresholds of sag magnitude and duration is proposed. The proposed method performs voltage sag assessment based on the area of vulnerability for given voltage thresholds and sag durations are estimated using a probability model on the historical operation data of protection system. In addition, we propose an effective assessment scheme based on the concept of measuration by division for a slope-shape tolerance curve.

ESTIMATED S-N CURVE FOR NODULAR CAST IRON: A STEERING KNUCKLE CASE STUDY

M. JIMENEZ,J. MARTINEZ,U. FIGUEROA,L. ALTAMIRANO 한국자동차공학회 2014 International journal of automotive technology Vol.15 No.7

Durability assessment is performed to establish the damage applied by loads and the number of load cyclesversus S-N curves. This information is evaluated using a fatigue damage hypothesis. A new relationship is proposed toestimate the S-N curve of nodular cast iron, based on its ultimate strength, using a case study of a steering knuckle componentunder bending load. Finite element simulation was performed to obtain the maximum stresses in the component using PatranV2012.2 and Nastran V2008 software. Correction factors accounted for surface finish, type of load and level of reliability. Actual and proposed predictions were evaluated using experimental results. The main aim of this work was to design a fatiguetest, with a limited amount of information, through finite element simulation and tensile strength. The main advantage of thisrelationship over the other methods for estimating an S-N curve, is to improve life prediction at the boundary of low and highcycle fatigue with a simple relationship and without a series of tests to identify the S-N curve, thus simplifying durabilityassessment with a limited amount of information. The proposed relationship improved the life prediction by an average of10% in the case study.

해군함정 화재 위험도 평가에 관한 연구

전계룡,김동진 한국화재소방학회 2008 한국화재소방학회논문지 Vol.22 No.5

With the huge navy projects such KDX-III, LPX, bigger and more complicated vessel constructions are being underway in navy. In this paper, considering these trends, we performed a risk analysis on the navy vessel for the fatality of soldiers on board and presented the risk level with FN curve. Assuming a fire occurs in one of the soldier bedrooms, we established event tree to visualize the possible development scenarios and calculated the fatality for each scenario. The critical condition to survive inside the bedroom was obtained through CFAST program. 최근 KDX-III, LPX 등 대형함 건조사업의 진행으로 예전과 달리 함정 규모가 커지고 함정 내 승조원 수 및 승조 인원 구성도 다양화 되고 있는 상황을 반영하여 화재로 인한 해군함정의 위험도를 정량적으 로 평가 분석하였다. 이를 위해 해군 함정의 복잡한 화재 전파양상을 사건수목분석(ETA)기법으로 모델링 하였고, 승조원 침실 내 화재해석을 위해 CFAST 프로그램을 이용하여 화재 전파양상 및 화재구역 내 거주가능시간(임계시간)을 예측하였다. 이를 승조원 탈출 시간과 비교하여 상황별 사망자 수를 산출하였으 며 FN-curve로 전반적인 위험도를 도식하여 화재 위험도의 수용여부를 판단할 수 있는 방법을 제시하였 다. 본 연구에서 제시된 방법론을 바탕으로 새롭게 건조되는 함정 설계단계에서 화재 발생시 함정에서의 인명위험성을 적절하게 평가할 수 있는 도구로 활용이 가능할 것으로 사료된다.

A Quantitative Assessment on a Tension of Securing Rope to evade Marine Accidents caused by Improper Cargo-Securing

Young-Du Kim 해양환경안전학회 2015 海洋環境安全學會誌 Vol.21 No.3

To prevent cargo accidents by repeated loads, a continuous monitoring for securing rope or additional safety measures are needed, but most of prevention measures have been conducted only by operator's own experience not a quantitative assessment. Hence, the Load-Displacement curve and approximation formula of securing rope were drawn in this research for a quantitative assessment and simplified measurement on a tension of securing rope using a tensiometer. Moreover, a com parison was conducted between m easuring tension and calculated tension on securing rope with portable tensiometer, 'Load-Displacement' approximation formula. The calculated tension of securing rope is obtained 153.3kfg using the formula and that result has not much difference with initial tension 150.0kgf. Lastly, an analysis of the characteristics of various ropes was suggested to enhance the reliability about quantitative assessment of securing rope's tension through further research.

A Quantitative Assessment on a Tension of Securing Rope to evade Marine Accidents caused by Improper Cargo-Securing

김영두 해양환경안전학회 2015 海洋環境安全學會誌 Vol.21 No.3

To prevent cargo accidents by repeated loads, a continuous monitoring for securing rope or additional safety measures are needed, but most of prevention measures have been conducted only by operator's own experience not a quantitative assessment. Hence, the Load-Displacement curve and approximation formula of securing rope were drawn in this research for a quantitative assessment and simplified measurement on a tension of securing rope using a tensiometer. Moreover, a comparison was conducted between measuring tension and calculated tension on securing rope with portable tensiometer, 'Load-Displacement' approximation formula. The calculated tension of securing rope is obtained 153.3kfg using the formula and that result has not much difference with initial tension 150.0kgf. Lastly, an analysis of the characteristics of various ropes was suggested to enhance the reliability about quantitative assessment of securing rope's tension through further research.

A new methodology of the development of seismic fragility curves

Lee, Young-Joo,Moon, Do-Soo Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

There are continuous efforts to mitigate structural losses from earthquakes and manage risk through seismic risk assessment; seismic fragility curves are widely accepted as an essential tool of such efforts. Seismic fragility curves can be classified into four groups based on how they are derived: empirical, judgmental, analytical, and hybrid. Analytical fragility curves are the most widely used and can be further categorized into two subgroups, depending on whether an analytical function or simulation method is used. Although both methods have shown decent performances for many seismic fragility problems, they often oversimplify the given problems in reliability or structural analyses owing to their built-in assumptions. In this paper, a new method is proposed for the development of seismic fragility curves. Integration with sophisticated software packages for reliability analysis (FERUM) and structural analysis (ZEUS-NL) allows the new method to obtain more accurate seismic fragility curves for less computational cost. Because the proposed method performs reliability analysis using the first-order reliability method, it provides component probabilities as well as useful byproducts and allows further fragility analysis at the system level. The new method was applied to a numerical example of a 2D frame structure, and the results were compared with those by Monte Carlo simulation. The method was found to generate seismic fragility curves more accurately and efficiently. Also, the effect of system reliability analysis on the development of seismic fragility curves was investigated using the given numerical example and its necessity was discussed.

A new methodology of the development of seismic fragility curves

이영주,Do-Soo Moon 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

There are continuous efforts to mitigate structural losses from earthquakes and manage risk through seismic risk assessment; seismic fragility curves are widely accepted as an essential tool of such efforts. Seismic fragility curves can be classified into four groups based on how they are derived: empirical, judgmental, analytical, and hybrid. Analytical fragility curves are the most widely used and can be further categorized into two subgroups, depending on whether an analytical function or simulation method is used. Although both methods have shown decent performances for many seismic fragility problems, they often oversimplify the given problems in reliability or structural analyses owing to their built-in assumptions. In this paper, a new method is proposed for the development of seismic fragility curves. Integration with sophisticated software packages for reliability analysis (FERUM) and structural analysis (ZEUS-NL) allows the new method to obtain more accurate seismic fragility curves for less computational cost. Because the proposed method performs reliability analysis using the first-order reliability method, it provides component probabilities as well as useful byproducts and allows further fragility analysis at the system level. The new method was applied to a numerical example of a 2D frame structure, and the results were compared with those by Monte Carlo simulation. The method was found to generate seismic fragility curves more accurately and efficiently. Also, the effect of system reliability analysis on the development of seismic fragility curves was investigated using the given numerical example and its necessity was discussed.

A Quantitative Assessment on a Tension of Securing Rope to evade Marine Accidents caused by Improper Cargo-Securing

Kim, Young-Du The Korean Society of Marine Environment and safet 2015 海洋環境安全學會誌 Vol.21 No.3

To prevent cargo accidents by repeated loads, a continuous monitoring for securing rope or additional safety measures are needed, but most of prevention measures have been conducted only by operator's own experience not a quantitative assessment. Hence, the Load-Displacement curve and approximation formula of securing rope were drawn in this research for a quantitative assessment and simplified measurement on a tension of securing rope using a tensiometer. Moreover, a com parison was conducted between m easuring tension and calculated tension on securing rope with portable tensiometer, 'Load-Displacement' approximation formula. The calculated tension of securing rope is obtained 153.3kfg using the formula and that result has not much difference with initial tension 150.0kgf. Lastly, an analysis of the characteristics of various ropes was suggested to enhance the reliability about quantitative assessment of securing rope's tension through further research.

A New Method for Developing Seismic Collapse Fragility Curves Grounded on State-Based Philosophy

Aref Baharvand,Abdolrasoul Ranjbaran 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.2

Since the current process to achieve the collapse fragility curve in practical applications seems too complicated, also time-consuming to dominant by structure designers, the focus of this study is on introducing of a new approach for establishing collapse fragility curves which requires less analytical effort. To achieve this goal, state-based philosophy (SBP) has been taken into consideration. This theory benefits from some similarities in the nature of every failure process in solid mechanics regardless of its source. In this study these similarities are used intelligently in procedure of formulating new fragility function which has couple of unknown parameters. Next, it will be shown that these parameters can be attained from two different sources: the pushover curves of the structure, some selective damage data from incremental dynamic analysis analyses. Finally a complete form of new collapse fragility function which is called "SBP fragility function" proposed as a substitute for conventional collapse fragility function. The most important advantage of this new fragility function is its non-probabilistic structure that will make a huge difference in the amount of effort required to achieve the fragility curves. In this research, in order to ensure the efficiency, accuracy of this fragility function all steps of SBP fragility analyses are done on some special moment frames models, their results are presented.

Bridge classes for regional seismic risk assessment: Improving HAZUS models

Mangalathu, Sujith,Soleimani, Farahnaz,Jeon, Jong-Su Elsevier 2017 ENGINEERING STRUCTURES Vol.148 No.-

<P><B>Abstract</B></P> <P>Recent efforts are oriented towards the regional risk assessment of bridge inventories by grouping bridge classes which are expected to have similar performance or damage measures during a seismic event. Although HAZUS represents the current state of the art in grouping the bridge classes, it suffers many drawbacks such as grouping based on traditional subjective approach, failure in explicitly addressing the effect of design and geometric attributes, and neglecting the effect of abutment type. A critical review of the HAZUS grouping and associated fragilities highlights the need for a more refined sub-binning of bridge classes for a reliable estimate of the seismic risk. Towards the objective of a performance-based grouping of bridge classes, a new grouping technique rooted in the statistical technique called analysis of variance is suggested in this paper. The approach is used to improve the HAZUS grouping through the case studies of California box-girder bridges. The proposed approach identifies more sub-classes than the HAZUS grouping, and the significance of the proposed grouping is demonstrated through the comparison of fragility curves of three bridge classes identified by the proposed grouping methodology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Critical review of HAZUS grouping of bridge classes and HAZUS fragilities. </LI> <LI> A novel methodology to group the bridge classes. </LI> <LI> Performance-based grouping of bridge classes. </LI> <LI> Revised grouping of bridge classes in California. </LI> </UL> </P>