• 한국지반공학회논문집
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• 제34권5호
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• pp.5-17
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• 2018

본 연구에서는 풍화암에 근입된 강관 매입말뚝의 안전율 제안을 위하여 정재하시험과 동재하시험을 수행하였다. 현장재하시험은 직경이 0.508, 0.457m 인 시험말뚝을 제작하여 정재하시험(14회)과 동재하시험(EOID 14회, Restrike 14회)을 실시하였다. 이때, 재하시험은 시험말뚝 시공완료 후 (1)초기동재하시험(EOID)을 수행하였으며, (2)시공완료 28일 후 정재하시험을 시행하였으며, (3)정재하시험 완료 후 15일 후에 재항타동재하시험(Restrike)을 실시하였다. 본 연구 결과 Davisson 판정법의 동재하시험을 이용한 지지력 산정 결과 정재하시험 대비 재항타동재하시험은 약 15% 낮게 나타났다. 정재하시험과 동재하시험의 지지력 분석을 통하여 안전율을 비교하였고, 최종적으로 동재하시험 안전율을 기존 2.0에서 1.75로 수정 제안하였다.

• 전기학회논문지P
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• 제58권2호
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• pp.108-115
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• 2009

Recent advances in computer technology have brought more dependence on software to train control systems. Hence, the safety assurance of the vital software running on the railway system is very critical task and yet, not many works have been done. While much efforts have been reported to improve electronic hardware's safety, not so much systematic approaches to evaluate software's safety, especially for the vital software running on board train controllers. In this paper, we have developed the static software testing tool for railway signaling, especially Fagan Inspection module and checklists supporting module. This static testing tool for railway signaling can be utilized at the assessment phase, and also usefully at the software development stage also. It is anticipated that it will be greatly helpful for the evaluation on the software for railway signalling system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.475-480
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• 1997

It is common to assum identical allowable safety factors in static strength, defined by mean stress and in fatigue, defined by stress amplitude. Under the load with asymmetrical cycles the safety factor is not the same. In this paper, with the consideration of unequal allowable safety factors a general method for estimating fatigue reliability of a machine element under a combined state of stress is derived based on the theory proposed by Prof. Kececioglu and normal distribution. The calculation of fatigue reliability for limited life is discussed with example.

• International Journal of Safety
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• 제6권1호
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• pp.22-25
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• 2007

Damping out high frequency low amplitude structural vibrations using PZT bimorph is presented. Static and Dynamic analyses of the piezoelectric bimorph bender were performed. Three layer piezoelectric actuators were modeled with SOLID5 coupled-field elements using ANSYS. Static deflection and modal analyses of the piezoelectric bimorph bender are presented. Proper tuning of the values of the resistor and inductor in the shunt circuit is required for maximum vibration suppression.

• Journal of Biosystems Engineering
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• 제41권3호
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• pp.153-160
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• 2016

Purpose: This study was conducted to experimentally investigate the structural safety of and identify critical locations in a front-end loader under impact loads. Methods: Impact and static tests were conducted on a commonly used front-end loader mounted on a tractor. In the impact test, the bucket of the front-end loader with maximum live load was raised to its maximum lift height and was allowed to free fall to a height of 500 mm above the ground where it was stopped abruptly. For the static test, the bucket with maximum live load was raised and held at the maximum lift height, median height, and a height of 500 mm from the ground. Strain gages were attached at twenty-three main locations on the front-end loader, and the maximum stresses and strains were measured during respective impact and static tests. Results: Stresses and strains at the same location on the loader were higher in the impact test than in the static test, for most of measurement locations. This indicated that the front-end loader was put under a severe environment during impact loading. The safety factors for stresses were higher than 1.0 at all locations during impact and static tests. Conclusions: Since the lowest safety factor was higher than 1.0, the front-end loader was considered as structurally safe under impact loads. However, caution must be exercised at the locations having relatively low safety factors because failure may occur at these locations under high impact loads. These important design locations were identified to be the bucket link elements and the connection elements between the tractor frame and front-end loader. A robust design is required for these elements because of their high failure probability caused by excessive impact stress.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.236-240
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• 2013

Due to difficulty of considering dynamic load in side of a computer resource and computing time, it is common that external load is assumed as ideal static load. However, structural analysis under static load cannot guarantee the safety of structural design. Recently, the systematic method to construct equivalent static load from the given dynamic load has been proposed. Previous study has calculated equivalent static load through the optimization procedure under displacement constraints. And previously reported works to distribute equivalent static load were based on ad hoc methods. However, it is appropriate to take into account the stress constraint for the safety design. Moreover, the improper selection of loading position may results in unreliable structural design. The present study proposes the methodology to optimize an equivalent static which distributed on the primary DOFs, DOFs of the constraint elements, DOF of an external load as positions. In conclusion, the reliability of proposed method is demonstrated through a global optimization.

• 자동차안전학회지
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• 제11권2호
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• pp.29-34
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• 2019

This paper presents a new method for construction of a static obstacle map. A static obstacle is important since it is utilized to path planning and decision. Several established approaches generate static obstacle map by grid method and counting algorithm. However, these approaches are occasionally ineffective since the density of LiDAR layer is low. Our approach solved this problem by applying probability theory. First, we converted all LiDAR point to Gaussian distribution to considers an uncertainty of LiDAR point. This Gaussian distribution represents likelihood of obstacle. Second, we modeled dynamic transition of a static obstacle map by adopting the Hidden Markov Model. Due to the dynamic characteristics of the vehicle in relation to the conditions of the next stage only, a more accurate map of the obstacles can be obtained using the Hidden Markov Model. Experimental data obtained from test driving demonstrates that our approach is suitable for mapping static obstacles. In addition, this result shows that our algorithm has an advantage in estimating not only static obstacles but also dynamic characteristics of moving target such as driving vehicles.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.205-212
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• 2002

It was performed that the stability evaluation using pseudo-static method and modified pseudo-static method for rockfill and rockfill-concrete section of composite dam. As a results of pseudo-static and modified pseudo-static analysis using seismic coefficient 0.154g, the maximum displacement at dam crest was occurred about 14~18cm on rockfill section and about 5~9cm on rockfill-concrete section, respectively. Also, that the factor of safety of down slope was more than 1.0~1.5. the rockfill and rockfill-concrete section of composite dam did not show any stability problems for 0.154g. Further research is still necessary in seismic safety of composite dam.

• 한국안전학회지
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• 제15권4호
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• pp.20-27
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• 2000

The hat shaped section members, spot welded strength resisting structures are the most energy absorbing ones of automobile components during the front-end collision. Under the static axial collapse load in velocity of 10mm/min and quasi-static collapse load in velocity of 1000mm/min, the collapse characteristics of the hat shaped section and double hat shaped section member have been analyzed by axial collapse tests with respect to the variations of spot weld pitches on the flanges. In addition, the quasi-static collapse simulations have been implemented in the same condition to the experiment's using FEM package, LS-DYNA3D. The simulated results have been verified in comparison with these from the quasi-static axial collapse tests. With the computational approaches the optimal energy absorbing structures can be suggested. Simulations are so helpful that the optimized data be supplied in designing vehicles in advance.

• 오토저널
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• 제8권3호
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• pp.55-67
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• 1986

The safety and comfort of car seats wee studied by utilization of engineering analysis/ experiment and human engineering data. As important factors of the static seating comfort, static spring constant, body pressure distribution, driving posture were discussed. In connection with the dynamic seating comfort, vibrational characteristics of domestic car seats(natural frequencies, damping, frequency spectrum, transmission ratio)were measured and discussed. Finally, the safety of the seat was analyzed and evaluated through calculation and experiments.