• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.2
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• pp.12-17
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• 2017

Manned aircraft structural design is based on structural safety factor of 1.5, and this safety factor is equivalent to a probability of failure of between 10-2 and 10-3. The target failure probability of FARs is between 10-6 and 10-9 per flight according to aircraft type. NATO released STANAG 4703 to established the airworthiness requirements for small UAV which is less than 150kg. STANAG 4703 requires the Target Level of Safety according to MTOW. The requirements of failure probability for small UAV is between 10-4 and 10-5. In this paper, requirements of airworthiness certification for small UAV were investigated and the relationship of safety factors to the probability of structural failure is analyzed to reduce measure of safety factor and structural weight of unmanned aircraft.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.2
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• pp.112-119
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• 2010

A Monte-Carlo simulation method is proposed which can evaluate the target failure/safety levels on any failure modes of harbor structures as a function of central safety factor. Unlike the calibration method based on the average safety level of conventional design criteria, the target failure/safety level can be directly evaluated by only using central safety factors of the harbor structures which have been designed by safety factor method during the past several decade years. Several mathematical relationships are represented to straightforwardly connect the conventional safety factor design method with reliability-based design method. Even though limited data have been used in applying Monte-Carlo simulation method to sliding failure mode of the vertical breakwaters, it is found that target reliability indices evaluated by the suggested method in this paper is satisfactorily agreement with new criteria of reliability index of Japan.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.62-68
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• 2009

Life Cycle Cost(LCC) is adopted to decide the target of safety level in designing suspension bridges. The LCC are evaluated considering two types of uncertainty; aleatory and epistemic. The nine alternative designs of suspension bridge are simulated to decide the safety level which can minimize the LCC. The LCC is calculated through the probability of failure and safety index including the uncertainty. This method results in the useful tool deciding the optimum safety level with minimal LCC as the main design factor.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.4
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• pp.267-277
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• 2009

Partial safety factors of the load, resistance, and reliability function are evaluated according to the target probability of failure on sliding mode of monolithical vertical caisson of composite breakwaters. After reliability function is formulated for sliding failure mode of caisson of composite breakwaters regarding bias of wave force, uncertainties of random variables related to loads, strengths are analyzed. Reliability analysis for the various conditions of water depth, geometric, and wave conditions is performed using Level II AFDA model for the sliding failure. Furthermore, the reliability model is also applied to the real caisson of composite breakwaters of Daesan, Dong- hae, and Pohang harbor. By comparing the required width of caisson of composite breakwater according to target probability of failure with the other results, the partial safety factors evaluated in this study are calibrated straightforwardly. Even though showing a little difference on the 1% of target probability, it may be found that the present results agree well with the other results in every other target probability of failure.

• Journal of Korea Water Resources Association
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• v.51 no.7
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• pp.543-554
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• 2018

A methodology has been presented for evaluating the partial safety factors on the sliding failure mode of vertical caissons of composite breakwaters and for determining the cross sections of those by Level I reliability-based design method. Especially, a mathematical model has been suggested for the sake of a consistency of code format as well as convenience of application in practical design, for which the uncertainties associated with buoyancy and its own weight can be taken into account straightforwardly. Furthermore, design criteria equation has been derived by considering accurately the effect of uplift pressure, so that the cross sections of caissons can be assessed which must be safe against the sliding failure. It has been found that cross sections estimated from partial safety factors proposed in this paper are in very good agreement with the results of Level II AFDA and Level III MCS under the same target probability of failure. However, partial safety factors of the Technical Standards and Commentaries for Port and Harbour Facilities in Japan and Coastal Engineering Manual in USA tend to estimate much bigger or smaller cross sections in comparison to the present results. Finally, many reliability re-analyses have been performed in order to conform whether the stability level of cross section estimated by Level I reliability-based design method is satisfied with the target probability of failure of partial safety factors or not.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.64-69
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• 2012

The concept of SIL is applied in the most of all standards relating to functional system safety. However there are problems for the people to apply SIL to their plants. as these standards don't include sufficient informations. In this regards, this paper will suggest the direction of SIL application and concept based on IEC 61508 and IEC 61511. A Safety Integrity Level(SIL) is the discrete level(one out of possible fours), corresponding to a range of the probability of an E/E/PE (Electric/Electrical/Programmable Electrical) safety-related system satisfactorily performing the specific safety functions under all the stated conditions within a stated period of time. SIL can be divided into the target SIL(or required SIL) and the result SIL. The target SIL is determined by the risk analysis at the analysis phase of safety lifecycle and the result SIL is calculated during SIL verification at the realization phase of safety lifecycle. The target SIL is determined by the risk analysis like LOPA(Layer Of Protection Analysis), Risk Graph, Risk Matrix and the result SIL is calculated by HFT(Hardware Fault Tolerance), SFF(Safe Failure Fraction) and PFDavg(average Probability of dangerous Failure on Demand). SIL is applied to various areas such as process safety, machinery(road vehicles, railway application, rotating equipment, etc), nuclear sector which functional safety is applied. The functional safety is the part of the overall safety relating to the EUC and the EUC control system that depends on the correct functioning of the E/E/PE safety-related systems and other risk reduction measures. SIL is applied only to the functional safety of SIS(Safety Instrumented System) in safety. EUC is the abbreviation of Equipment Under Control and is the equipment, machinery, apparatus or plant used for manufacturing, process, transportation, medical or other activities.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.191-201
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• 2010

The breakwaters are designed by considering the cost optimization because a human risk is seldom considered. Most breakwaters, however, were constructed without considering the cost optimization. In this study, the optimum return period, target failure probability and the partial safety factors were evaluated by applying the cost optimization to the rubble mound breakwaters in Korea. The applied method was developed by Hans F. Burcharth and John D. Sorensen in relation to the PIANC Working Group 47. The optimum return period was determined as 50 years in many cases and was found as 100 years in the case of high real interest rate. Target failure probability was suggested by using the probabilities of failure corresponding to the optimum return period and those of reliability analysis of existing structures. The final target failure probability is about 60% for the initial limit state of the national design standard and then the overall safety factor is calculated as 1.09. It is required that the nominal diameter and weight of armor are respectively 9% and 30% larger than those of the existing design method. Moreover, partial safety factors considering the cost optimization were compared with those calculated by Level 2 analysis and a fairly good agreement was found between the two methods especially the failure probability less than 40%.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.157-165
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• 2008

Level II AFDA and Level III MCS reliability models are applied to analyze the stability of armor units on trading and coastal harbors in Korea. Hudson's formula and Van der Meer's formula are used in this reliability analysis. Also, probability density functions of reliability index and probability of failure are derived by the additional analysis. In addition, the partial safety factors of all harbors related to armor units can be straightforwardly evaluated by the inverse-reliability method. The upper and lower limits and average level of partial safety factors can be statistically investigated with the results of all cases applied in this paper. Therefore, it may be possible to design armor units of new breakwaters including the uncertainty of random variable and target level by using the present results.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.3
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• pp.157-165
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• 2022

As the number of the installed escalators in Korea continues to increase, the accident rate is also increasing. Therefore, it would be necessary to proactively secure safety. PESSRAE is a controller that implements safety functions as electric/electronic/programmable electronic devices to respond to risks that may occur in escalators. Safety Integrity Level (SIL) is assigned to the safety functions of PESSRAE and it must be verified that the quantitative target value according to the SIL level is satisfied. In this paper, the initial PESSRAE is analyzed using the FMEDA (Failure Mode, Effects and Diagnostic Analysis), which is a quantitative safety analysis method, and design improvement specifications are derived from the analysis in order to satisfy the quantitative target values. Based on the derived design specifications, the improved PESSRAE controller was manufactured. And the appropriateness of the design was verified experimentally in a testbed environment simulating the real environment.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.5-15
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• 2014

Target reliability index in the limit state design indicated the safety margin and it is important to determine the partial factor. To determine the target reliability index which is needed in the limit state design, the six design and construction case histories of gravel compaction piles (GCP) were investigated. The limit state functions were defined by bulging failure for the major failure mode of GCP. The reliability analysis were performed using the first order reliability method (FORM) and the reliability index was calculated for each ultimate bearing capacity formulation. The reliability index of GCP tended to be penportional to the safety factor of allowable stress design and average value was ${\beta}$=2.30. Reliability level that was assessed by reliability analysis and target reliability index for existing structure foundations were compared and analyzed. As a result, The GCP was required a relatively low level of safety compared with deep and shallow foundations and the currd t reliability level were similar to the target reliability in the reinforced earth retaining-wall and soil-nailing. Therefore the target reliability index of GCP suggested as ${\beta}_T$=2.33 by various literatures together with the computed reliability level in this study.