• 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.

• 대한산업공학회지
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• 제9권2호
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• pp.9-25
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• 1983

The purpose of this study was to film up computerized analyses for both kinematic posture(film analysis) and muscle dynamics (EMG) during a weight-lifting motion. (Snatch, Clean and Jerk) Using a motor drive camera (3.5 frames/sec) and a Location Analyzer, motion tracks of 13 landmarks, which were attached to the major joints, during the motion were converted into digital values. At the same time, EMG amplitudes from 11 major muscle groups were recorded. Recorded data were processed via analog/hybrid computer (ADAC 480) and digital computer (PDP 11/44). Landmark locations and EMG amplitude were integrated by a computerized routine. Computer output included graphic reproductions on sepuential dislocations of body segments, center of gravity of body segments and the associated changes on EMG amplitude such as % EMG's of major muscle group during a weight lifting motion. The results strongly suggest that the computerized motion-EMG integration can provide a further working knowledge in selection and in training of workers and athletes. Suggestions for a further study include additional device for velocity measurement, expansion of the link model for biomechanical analysis and other implementations necessary for athletic application.

• 한국안전학회지
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• 제24권2호
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• pp.69-75
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• 2009

It is well-known that lifting capacity of a worker is influenced by body posture during the task. When a task analyst make use of RULA and REBA Trunk and upper arm angles are recorded in a separate item. It means that the interaction between the angles of two body segments may be ignored in a final score. The NLE(NIOSH Lifting Equation) has been used to supplement this problem. However, there is no study to validate the result of RWL (Recommended Workload Limit) under the existence of interactions between trunk and upper arm angles. The goal of this study was to assess the effect of the interaction between trunk and upper arm angles. Three responses, including NMVC(normalized maximum voluntary contraction), RWL(Recommended Weight Limit) and subjective judgment in psychophysical method (Borg's scale), were recorded according to the combinations of three trunk angles and nine upper arm angles. The results showed that lifting capacity is highly influenced by interaction of two body segments(trunk and upper arm). It means that the task workload has to be analyzed along with the interaction of trunk angles and upper arm angles when the task analyst assesses potential risk factors on the postures. This study may be able to be a fundamental study to develop an assessment method for lifting task analyses according to body postures.

• 대한인간공학회지
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• 제28권3호
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• pp.41-47
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• 2009

The purpose of this study, during the lifting task was researching the difference and a relationship between the ground reaction force and the grip strength by change of position. After grip strength has measured in symmetry position and asymmetry position at 45cm and 75cm of height of hand, ground reaction force was measured by same attitude lifting wooden box. We analyzed the difference of grip strength and ground reaction force in each position change. The results of grip strength, the grip strength of both hand were significant difference that in study subject symmetry and asymmetry position (p<0.01). The results of symmetry lifting task, the study subjects was significant difference of the ground reaction force difference by height (p<0.05). Asymmetry lifting task was significant difference of ground reaction force difference by direction of rotation was changed (p<0.01). The result of it will rotate with non-dominant hand side of lifting tasks from height 75cm where it easily maintains a balance possibility and decreasing the load of the hand. Therefore, from the workshop in the work people, it will be between the height 75cm and non-dominant hand side of trunk rotatory direction in the lifting tasks. Future study is necessary researched about the change of grip strength when the height of the hand is higher, and the difference of the ground reaction force when the change of weight.

• 한국산업보건학회지
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• 제15권2호
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• pp.104-113
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• 2005

A variety of ergonomic assessment methods of lifting tasks known as a major cause of work-related lower back pain have been used. But there is a limited information in choosing the most appropriate assessment method for a particular job and in finding out strengths and weakness of the methods. The purpose of this study was to assess and compare the ergonomic risks of lifting tasks in a marine diesel engine production industry by three lifting ergonomic assessment tools widely used: the National Institute for Occupational Safety and Health(NIOSH) Revised Lifting Equation(NLE), the Washington Administrative Code 296-62-0517(WAC), and the Snook Tables. Lifting index(weight of load/Recommended Weight Limit) of NLE($LI_{NLE}$) was above 1 at 34 tasks(75.6%) of a total number of 45 lifting tasks. LI of WAC($LI_{WAC}$) was above 1 at 11 tasks(24.4 %). LI of Snook Table($LI_{Snook}$) was above 1 at 29 tasks(64.4%). Thus, LI was high in orders of $LI_{NLE}$ > $LI_{Snook}$ > $LI_{WAC}$. There were significantly high correlations among three Lls(p<0.01). The correlation coefficients between $LI_{NLE}$and the other three Lls($LI_{WAC}$ and $LI_{Snook}$) were r=0.93 and r=0.88, respectively. The linear regression equations were y = 0.444x + 0.11(r=0.93) between $LI_{NLE}$ and $LI_{WAC}$, y = 0.93x + 0.008(r=0.88) between LI(NLE) and $LI_{Snook}$. The LI values by WAC was significantly lower than those by the other tools. The compared features, strength and limitation among these tools were described in this paper.

• 대한산업공학회지
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• 제33권1호
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• pp.44-51
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• 2007

The purpose of this study was to identify the relationship between the cumulative fatigue of trunk muscles andthe period of recovery time during repetitive lifting and lowering tasks with symmetric and asymmetric postures.Ten subjects participated in the experiment. Subjects had 1, 2, 3, 4 and 5 minutes recovery time respectivelywhile they were performing the lifting and lowering task repeatedly for 3 minutes with the weight equivalent to25% level of MVC. EMG signals from ten trunk muscles were collected and the fatigue level was analyzedquantitatively. In results, the local muscle fatigue was no longer accumulated when 5 minutes recovery time wasgiven in symmetric position. For asymmetric position, it took longer minutes to prevent the fatigue accumul-ation. Different trunk muscles indicated slightly different recovery patterns in terms of MPF (Mean Powerfrequency) value.This result would help ergonomist design the length of recovery time to control the cumulative fatigue of trunkmuscles in industry with repetitive lifting and lowering task.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1997년도 춘계학술대회논문집
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• pp.39-49
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• 1997

The objective of this study was to make comparison of the psychophysical MAWLs for different manual materials handling tasks. Lifting activities with four different lifting frequencies (2, 5, 8, 11 lifts/min) for one lifting range from floor to 76cm height were studied. The oxygen consumption rate and heart rate were measured or recorded while subjects were lifting their MAWLs. Psychophysical MAWL decreased from 22.38 kg to 7.48 kg, while th oxygen consumption rate with the MAWL increased from 717.8 ml/min to 1114.7 ml/min as the frequency increased from 2 to 11 Lifts/min. Heart rate also increased from 104.5 to 120.7 bpm. It was found that the relationship between MAWL and frequency can be described best by the exponentaial function with the R-sq value 0.9865 for this study. The percent ratio of oxygen consumption rate with the MAWL and PWC ranged from 28% to 43%.

• 대한의용생체공학회:의공학회지
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• 제32권4호
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• pp.328-335
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• 2011

For human factor engineering and wearable robot design, the quantitative assessment of physical workload is needed. Through measuring the surface EMG (sEMG) and analysis, the physical workload in overhead lifting posture is presented in quantitative manner. By normalizing sEMG activities with maximal voluntary contraction (MVC), the inter-subject variability is reduced. In all muscles, %MVC increased as the weight of lifting object increases. In anterior deltoid muscle, the %MVC was 3-4 times higher than the other muscles which imply that this muscle performs the major role in the overhead lifting posture. In fatigue analysis, %MVC and the mean frequency in muscle of anterior deltoid changed markedly when compared with other muscles. Through the suggested procedures and analysis, the physical workload for a specific posture can be represented in quantitative way but the clinical meaning for the value should be investigated further.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.563-570
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• 2022

Industrialized and modular construction is a growing construction technique that can transfer a large portion of the construction process to off-site fabrication yards. This method of construction often involves the fabrication, pre-assembly, and transportation of massive and long volumetric modules. The module weight keeps increasing as the modules become more complete (with infill) to minimize the work at the site and, as higher productivity can be achieved at the fabrication shop. Thus, a volumetric module delivery gets more challenging and risky. Despite its importance, past research paid relatively insufficient attention to the problem related to the lifting of heavy modules. This can be a complex and time-consuming problem with multiple lifting for transportation-and-installation operations both in fabrication yard and jobsite, and require complex crane operations (sometimes, more than one crane) due to crane load capacity and load balance/stability. This study investigates this problem by focusing on the structural perspective of lifting such long volumetric modules through simulation studies. Various scenarios of lifting a weighty module from the top using four lifting cables attached to crane hooks (either a single crane or double crane) are simulated in SAP software. The simulations account for various factors pertaining to structural indices, e.g., bending stress and deflection, to identify a proper method of module lifting from a structural point of view. The method can identify differences in structural indices allowing identification of structural efficiency and safety levels during lifting, which further allows the selection of the number of cranes and location of lifting points.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 추계학술대회 논문집(제1권)
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• pp.317-323
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• 2006

본 시험의 목적은 컨테이너터미널의 생산성을 향상시키기 위해서 기술개발 추진 중인 컨테이너 자기하역차량(ALV:Automated Lifting Vehicle)의 핵심 기술개발 요소 중 하나인 주행구동장치 (Gantry Travel Mechanism) 시제품을 제작하여, 무부하 및 부하 조건에서 각종 Test와 한계하중 실험 과정을 통하여 설게 Data의 확인과 상세 제작도면의 오류를 사전에 발견하여 최종 제작도면에 수정 반영함으로써 보다 완벽한 장비를 개발하는 것을 목적으로 한다.