• 한국안전학회지
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• 제24권2호
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• pp.76-82
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• 2009

The NIOSH lifting equation has been used as a dominant tool in evaluating the hazard levels of lifting tasks. Although it provides two different ways for each simple and complex lifting task, the NIOSH simple lifting equation is almost used for not only simple tasks but also complex tasks. However, most of lifting tasks in industries are in the form of complex lifting. Therefore some errors occur inevitably in the evaluation of complex lifting tasks. Among complex lifting tasks, a multi-stacking task is the most popular in lifting tasks. To compensate the error in the evaluation of multi-stacking tasks by using the NIOSH simple lifting equation, a set of calculations for finding LIs(Lifting Indices) was performed for the systematically varying multi-stacking tasks. Then a regression model which finds the equivalent height in simple lifting task for multi-stacking task was established. By using this model, multi-stacking tasks can be evaluated with less error. To validate this model, some real multi-stacking tasks were evaluated as examples.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.160-161
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• 2016

In tall building construction, lift car for worker lifting is a critical factor for construction productivity. To reduce worker lifting time, existing researches have been conducted on lift car planning. While, research on lift car operation is insufficient. For the efficient reduction of worker lifting time, lift car operation control is needed with lift car planning. Therefore, this research suggests operation control model of lift car to reduce worker lifting time. According to the result of a model test, the operation control model contributes to reasonable reduction of worker lifting time.

• 대한안전경영과학회지
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• 제4권2호
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• pp.11-22
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• 2002

In this study, an asymmetric lifting posture prediction model was developed, which was a three-dimensional model with 12 links and 23 degrees of freedom open kinematic chains. Although previous researchers have proposed biomechanical, psychophysical, or physiological measures as cost functions, for solving redundancy, they lack in accuracy in predicting actual lifting postures and most of them are confined to the two-dimensional model. To develop an asymmetric lifting posture prediction model, we used the resolved motion method for accurately simulating the lifting motion in a reasonable time. Furthermore, in solving the redundant problem of the human posture prediction, a moment weighted Joint Range Availability (JRA) was used as a cost function in order to consider dynamic lifting. However, it is known that the moment weighted JRA as a cost function predicted the lower extremity and L5/S1 joint motions better than the upper extremities, while the constant weighted JRA as a cost function predicted the latter better than the former. To compensate for this, we proposed a hybrid moment weighted JRA as a new cost function with moment weighted for only the lower extremity. In order to validate the proposed cost function, the predicted and real lifting postures for various lifting conditions were compared by using the root mean square(RMS) error. This hybrid JRA reduced RMS more than the previous cost functions. Therefore, it is concluded that the cost function of a hybrid moment weighted JRA can be used to predict three-dimensional lifting postures. To compare with the predicted trajectories and the real lifting movements, graphical validations were performed. The results also showed that the hybrid moment weighted cost function model was found to have generated the postures more similar to the real movements.

• 대한인간공학회지
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• 제30권5호
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• pp.597-603
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• 2011

Objective: The objective of this study was to compare one-hand and two-hands lifting activity in terms of biomechanical stress for the range of lifting heights from 10cm above floor level to knuckle height. Background: Even though two-hands lifting activity of manual materials handling tasks are prevalent at the industrial site, many manual materials handling tasks which require the worker to perform one-hand lifting are also very common at the industrial site and forestry and farming. Method: Eight male subjects were asked to perform lifting tasks using both a one-handed as well as a two-handed lifting technique. Trunk muscle electromyographic activity was recorded while the subjects performed the lifting tasks. This information was used as input to an EMG-assisted free-dynamic biomechanical model that predicted spinal loading in three dimensions. Results: It was shown that for the left-hand lifting tasks, the values of moment, lateral shear force, A-P shear force, and compressive force were increased by the average 43%, as the workload was increased twice from 7.5kg to 15.0kg. For the right-hand lifting task, these were increased by the average 34%. For the two-hands lifting tasks, these were increased by the average 25%. The lateral shear forces at L5/S1 of one-hand lifting tasks, notwithstanding the half of the workload of two-hands lifting tasks, were very high in the 300~317% of the one of two-hands lifting tasks. The moments at L5/S1 of one-hand lifting tasks were 126~166% of the one of two-hands lifting tasks. Conclusion: It is concluded that the effect of workload for one-hand lifting is greater than two-hands lifting. It can also be concluded that asymmetrical effect of one-hand lifting is much greater than workload effect. Application: The results of this study can be used to provide guidelines of recommended safe weights for tasks involved in one-hand lifting activity.

• 한국도로학회논문집
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• 제9권2호
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• pp.27-37
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• 2007

본 연구는 프리캐스트 콘크리트 포장 시공을 위하여 공장에서 미리 제작된 콘크리트 슬래브를 리프팅을 할 때 리프팅 위치에 따른 슬래브의 응력변화를 기준으로 슬래브의 손상을 최소화할 수 있는 가장 안전한 최적 리프팅 지점을 선정하기 위하여 수행되었다. 리프팅 시 슬래브의 응력분포를 분석하기 위하여 유한요소법을 이용한 모델을 사용하였으며 슬래브 규격은 시험시공에서 사용한 크기를 적용하였다. 리프팅은 항상 슬래브의 수직방향으로 수행하지는 않기 때문에 수직으로 리프팅 하였을 때와 $60^{\circ},\;30^{\circ}$로 경사각을 주어 리프팅 하였을 때의 응력변화 특성을 분석하였다. 또한 리프팅 지점은 항상 슬래브의 중간 깊이인 중립축의 위치가 아니기 때문에 중립축으로부터 7.5cm. 15cm만큼 수직편심을 주어 리프팅하였을 때의 응력변화 특성도 분석하였다. 그리고 실제 시공 시 지점부분에 보강을 하는 것을 염두하여 지점부 응력집중현상을 무시한 경우와 보강이 없을 경우의 응력집중현상을 고려한 경우로 나누어 분석하였다. 이러한 해석을 통해 리프팅 경사각과 편심에 따른 최적 리프팅 위치를 선정하였으며 미국의 PCI기준과도 비교 분석하였다.

• 한국안전학회지
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• 제8권4호
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• pp.82-90
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• 1993

Manual lifting, as a part of Manual Materials Handling Activities, is recognized by authorities in the field of occupational health and safety as a major hazard to industrial workers. The most important problem in applying fuzzy model of manual materials lifting is the decision of membership functions on each approaches. : Biomechanical, Physiological, Psychophysical. The primary objectives of this paper suggests to process deciding the most acceptable membership functions for establishing permissible weights on manual lifting activities using fuzzy sets.

• 산업경영시스템학회지
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• 제37권4호
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• pp.72-81
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• 2014

Even though two-hands lifting/lowering activity of manual materials handling tasks are prevalent at the industrial site, many manual materials handling tasks which require the worker to perform one-hand lifting/lowering are also very common at the industrial site, forestry, farming, and daily life. The objective of this study was to compare one-hand lowering activity to lifting activity in terms of biomechanical stress for the range of lowering heights from knuckle height to 10cm above floor level with two workload 7.5kg and 15.0kg. Eight male subjects with LMM were asked to perform lifting/lowering tasks using both a one-handed (left-hand and right-hand) as well as a two-handed technique. Spinal loading was estimated through an EMG-assisted free-dynamic biomechanical model. The biomechanical stress of one-hand lowering activity was shown to be 43% lower than that of one-hand lifting activity. It was claimed that the biomechanical stress for one-hand lifting/lowering activity is almost twice (194%) of the one for two-hands lifting/lowering activity. It was also found that biomechanical stress by one-hand lowering/lifting activity with the half workload of two-hands lowering/lifting activity was greater than that of the two-hands lowering/lifting activity. Therefore, it might be a risk to consider the RWL of one-hand lowering/lifting activity to simply be a half of the RWL of two-hands lowering/lifting activity recommended by NIOSH.

• 한국건축시공학회지
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• 제18권5호
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• pp.489-498
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• 2018

본 연구는 대공간 지붕철골공사의 양중공법 선정을 위한 의사결정지원모델 제안을 목적으로 한다. 이를 위해 이론적 고찰 및 전문가자문을 통해 6개의 상위요인과 19개의 하위요인으로 구성된 양중공법 선정 영향요인을 도출하였다. 이후 AHP분석을 통해 요인별 상대적 중요도를 산정한 결과, 6개의 상위요인 중 현장조건(0.237), 19개의 하위요인 중 여유공지의 유무(0.118)가 양중공법 선정에 있어 가장 중요한 영향요인으로 도출되었다. 이를 바탕으로 현장관리자가 공법대안을 평가할 수 있는 방법 및 절차를 수립하고 최종적으로 현장적합도지수를 제시해줌으로써 의사결정지원모델을 구축을 완료하였다. 구축모델의 검증을 위해 대공간 현장경험자를 대상으로 사례분석을 수행한 결과, 제시된 모델이 공법선정에 있어 유용하게 활용될 수 있을 것으로 판단되었다. 본 연구의 결과는 프로젝트 초기 공법선정 과정에서 현장관리자의 의사결정을 지원하는데 활용될 것으로 기대된다.

• 대한조선학회 특별논문집
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• 대한조선학회 2011년도 특별논문집
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• pp.82-89
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• 2011

In general, a number of lifting lugs have been used in shipbuilding industry and the D-type lugs are mainly used. The aim of this paper is to increase the cycle of the use and to reduce the size of lifting lugs to introduce lightweight shackle. In this study, nonlinear elasto-plastic analysis has been performed to confirm the ultimate strength of lifting lugs. In order to evaluate the proper design-load distribution around lug eye, the contact force between lifting lug and shackle pin has been realized by gab element model. Gap element modeling and nonlinear analysis are carried out using the finite element program MSC/PATRAN & ABQUS. Additionally the ultimate strength tests were performed to verify the structural adequacy of newly designed lifting lug and to insure safety of it. The D-10, 15, 20 & 40 ton models which are mainly used in the block erection are selected in the strength test. According to the results of the analysis and strength test, the ultimate strength of the newly designed lifting lugs has been estimated to exceed 3 times of design working load.

• 대한산업공학회지
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• 제21권4호
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• pp.581-591
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• 1995

The main objective of this study is to compare three representative methods predicting compressive forces on lumbosacral disc : LP-based method, double LP-based method and EMG-assisted method. Two subjects simulated lifting tasks performed in the refractories industry, in which vertical and horizontal distance, and weight of load were varied. To calculate the L5/S1 compressive forces, EMG signals from six trunk muscles were measured and postural data and locations of load were recorded using the Motion Analysis System. The EMG-assisted model was shown to reflect well all three factors considered here. On the other hand, the compressive forces of the LP-based model and the double LP-based model were only significantly affected by weight of load. In addition, lowly positive correlation was observed between compressive forces of the EMG-assisted model and lifting index(LI) of 1991 NIOSH lifting equation. From this results, it can be concluded that compressive forces on L5/S1 by the EMG-assisted method should be used as biomechanical criterion in order to evaluate risk of jobs precisely, and LI can not evaluate risk of lifting tasks fully.