• Title/Summary/Keyword: Moment Arm

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Eccentric Axial Loading Test for Concrete-Encased L-section Columns using 800MPa Steel and 100MPa Concrete (800MPa 강재 및 100MPa 콘크리트를 적용한 ㄱ형 강재 매입형 합성기둥의 편심압축실험)

  • Kim, Chang-Su;Park, Hong Gun;Lee, Ho Jun;Choi, In Rak
    • Journal of Korean Society of Steel Construction
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    • v.25 no.2
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    • pp.209-222
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    • 2013
  • Eccentric axial loading test was performed for concrete-encased columns using 800MPa steel and 100MPa concrete. To maximize the contribution of the high-strength steel, L-shaped steel sections were placed at four corners, and connected to each other by lattices, links, or battens. Compared to a H-section of the same area, the moment-arm and strain of the L-sections are increased. Also, the corner L-sections provide good lateral confinement to concrete core. The test results showed that the peak strength and effective flexural stiffness of the L-section columns were increased by more than 1.4 times those of the H-section column.

Convergence of Comparison of Muscle Activities of Healthy Adults' trunk and Lower Extremities according to wearing/not-wearing and forms of backpack (백팩 착용 유무 및 형태에 따른 건강한 성인의 몸통과 하지의 근 활성도 비교분석의 융합연구)

  • Kim, Kyung-Hun;Jang, Sang-Hun
    • Journal of the Korea Convergence Society
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    • v.10 no.11
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    • pp.225-232
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    • 2019
  • This study aims to compare muscle activities of trunk and lower extremities according to wearing/not-wearing and forms of backpack. Twenti-six healthy adults were participated in the study. In the backpack with 10% body weight, trunk and lower extremities were measured during carrying the no backpack state(NBs), general backpack state(GBs), a decrease moment arm backpack state(DMBs). The muscle activity in a fore muscles(Obilique, Quadriceps, Tibialis anterior, Gastrocnemius) were analyzed with using wireless electromyogram measuring system. DMBs showed significant improvemet in obilique, quadriceps and gastrocnemius muscle RVC.

Biomechanical and Physiological Comparative Analysis of the Single-Radius Knee Arthroplasty Systems and Multi-Radius Knee Arthroplasty Systems (무릎인공관절 단축범위(Single-Radius) 수술자와 다축범위(Multi-Radius) 수술자의 운동역 학적 및 운동생리학적 비교분석)

  • Jin, Young-Wan;Kwak, Yi-Sub
    • Journal of Life Science
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    • v.18 no.11
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    • pp.1532-1537
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    • 2008
  • The purpose of this study was to investigate the effect of different arthroplasty designs on knee kinematic and lower limb muscular activation for up-stair and down-stair movement. 3-D video analysis of whole body and joint kinematics and EMG analysis of quadriceps and hamstrings were conducted. One-way ANOVAs were used for statistical analyses (p=0.05). The single-radius group exhibited more arthroplasty limb quadriceps EMG and hamstring coactivation EMG than the multi-radius group. Single-radius demonstrated more abduction angular displacement and reached peak abduction earlier than the multi-radius arthroplasty limb. The single- radius the percent body fat showed similar values in the Elderly, Single and Multi-radius group among the periods, however Control group was Lowered among the periods. Single-radius group limb also increased the quadriceps muscle activation level to produce more knee extension moment to compensate for the short quadriceps moment arm. Resting metabolic rate was significantly increased in control group in the period of LI. Energy expenditure was extremely increased in all groups except control group among the periods. We can say this is the exercise effects.

Kinematic Analysis on Giant Swing Backward to Handstand on Parallel Bars (평행봉 뒤 휘돌리기 동작의 운동학적 분석)

  • Ahn, Wan-Sik
    • Korean Journal of Applied Biomechanics
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    • v.14 no.2
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    • pp.27-40
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    • 2004
  • The objective of this study is to identify the kinematic variables of giant swing backward to handstand as well as individual variations of each athlete performing this skill, which in turn will provide the basis for developing suitable training methods and for improving athlete's performance in actual games. For this end, 3 male athletes, members of the national team, who are in ${\Box}{\Box}H{\Box}{\Box}$ University, have been randomly chosen and their giant swing backward to handstand performance was recorded using two digital cameras and analyzed in 3 dimensional graphics. This study came to the following conclusion. 1. Proper time allocation for giant swing backward to handstand are: Phase 1 should provide enough time to attain energy for swing track of a grand round movement. The phase 3 is to throw the body up high in the air and stay in the air as long as possible to smoothen up the transition to the next stage and the phase 4 should be kept short with the moment arm coefficient of the body reduced. 2. As for appropriate changes of locations of body center, the phase 1 should be comprised of horizontal, perpendicular, compositional to make up a big rotational radius. Up to the Phase 3 the changes of displacements of vertical locations should be a good scale and athlete's body should go up high quickly to increase the perpendicular climbing power 3. When it comes to the speed changes of body center, the vertical and horizontal speed should be spurred by the reaction of the body in Phase 2 and Phase 3. In the Phase 4, fast vertical speed throws the body center up high to ensure enough time for in-the-air movement. 4. The changes of angles of body center are: in Phase 2, shoulder joint is stretching and coxa should be curved up to utilize the body reaction. In the Phase 4, shoulder joint and coxa should be stretched out to get the body center as high as possible in the air for stable landing. 5. The speeds of changes in joints angles are: in the Phase 2 should have the speed of angles of shoulder joints increase to get the body up in the air as quickly as possible. The Phase 3 should have the speed of angles in shoulder joint slow down, while putting the angles of a knee joint up to speed as quickly as possible to ensure enough time for in-the-air movement.

A Study on The Multi-point Signal and It's Directivity detection of FBG Hydrophone Using Hopper WDM be in The Making (Hopper WDM을 이용한 FBG(Fiber Bragg Grating) 하이드로폰(Hydrophone)의 다중점신호검출 및 지향성 연구)

  • Kim, Kyung Bok
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.11
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    • pp.156-163
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    • 2015
  • In the using of FBG(Fiber Bragg Grating) developed in home land, we designed and manufactured united FBG acoustic transducers the first in Korea. they are being applied to multi-point signal detection of FBG Hydrophone used Hopper WDM(national patent NO 10-1502954) in the underwater. On united FBG transducers manufactured, we made an demonstrated on respective frequency response peculiarities in the underwater and analyzed the special characters. As the experimental result on frequency response peculiarities, we made it possible underwater acoustic detection on united FBG acoustic transducers type to maximum 30Hz~2.5KHz. it's the optimum conditions of 1.2KHz frequency in detection. And for the purpose of realization on multi-point signal detection on wide scope in the underwater, in the using of WDM(Wavelength Division Multiplexing) method and passive band-pass filter system, established arrays system and succeeded in multi-point underwater acoustic signal detection to the frequency 200Hz~1.3KHz out of the two united type FBG transducers. Additionally, it would be possible directivity detection for the object of its source as the intensity of detection signal varies with the sound source's direction and angle. From now on we prepared a new moment on the practical use study on FBG hydrophone in the future.

KNEE: Basic Science and Injury of Bone (슬관절 주위 글격의 기초과학 및 스포츠 손상)

  • Kim Hee-Chun
    • Journal of Korean Orthopaedic Sports Medicine
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    • v.2 no.2
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    • pp.77-81
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    • 2003
  • Purpose: The biomechanics and kinematics of knee joint were reviewed in this article. And then the common sports injuries were presented. Anatomy and Kinetics: None of the pairs of bearing surfaces in the knee joint is exactly congruent This allows the knee six degrees of freedom of motion. Tibiofemoral Kinematics: In flexion and extension, the axis of motion is not perpendicular to the medial-lateral plane of the joint, nor is it perpendicular to the axis of longitudinal rotation. This results in coupled varus angulation and internal rotation with flexion and in valgus angulation and external rotation with extension. Patellofemoral Articulation: Loads across the patellofemoral joint are indirectly related to the angle of knee flexion and directly related to the force generated within the quadriceps mechanism. Fractures of the Patella: Nonoperative treatment is indicated if the extensor mechanism is intact and if displacement of fragment is minimal. The specific type of internal fixation depends on the fracture pattern. It is important to repair retinaculum. Acute and Recurrent Patellar Instability: The degree of dysplasia and the extent of the instability play a large part in determining the success of nonoperative treatment. Patients who experience recurrent dislocations and patients with major anatomic variations require surgery to minimize their instability. Sports Injuries in School-age Atheletes: Patellar pain in young athletes groups a number of conditions, including Idiopathic Adolescent Anterior Knee Pain, Osgood- Schlatter Disease, and Sinding-Larsen-Johansson Disease.

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Pseudo-Static Behaviors of U-shaped PSC Girder with Wide Flanges (확폭플랜지를 갖는 U형 프리스트레스 거더의 유사정적거동)

  • Rhee, In-Kyu;Lee, Joo-Beom;Kim, Lee-Hyeon;Park, Joo-Nam;Kwak, Jong-Won
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.993-999
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    • 2008
  • A girder height limitation is the critical parameter for rapid construction of bridge deck and construction space limitation especially in urban area such as high population area and high density habitats. A standard post-tensioned I-shaped concrete girder usually demands relatively higher girder height in order to retain sufficient moment arm between compression force and tensile force. To elaborate this issue, a small U-shaped section with wide flanges can be used as a possible replacement of I-shaped standard girder. This prestressed concrete box girder allows more flexible girder height adjustment rather than standard I-shaped post-tensioned girder plus additional torsion resistance benefits of closed section. A 30m-long, 1.7m-high and 3.63m-wide actual small prestressed concrete box girder is designed and a laboratory test for its static behaviors by applying 6,200kN amount of load in the form of 4-point bending test was performed. The load-deflection curve and crack patterns at different loading stage are recorded. In addition, to extracting the dynamic characteristics such as natural frequency and damping ratio of this girder, several excitation tests with artificial mechanical exciter with un-symmetric mass are carried out using operational frequency sweep-up. Nonlinear finite element analysis of this 4 point bending test under monotonic static load is investigated and discussed with aids of concrete damaged plasticity formulation using ABAQUS program.

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A Study on the Evaluation Method to Flexural-bonding Behavior of FRP-Rebar Concrete Member (FRP를 보강근으로 사용한 콘크리트 부재의 휨-부착 거동 평가방법에 관한 연구)

  • Choi, So-Yoeng;Choi, Myoung-Sung;Kim, Il-Sun;Yang, Eun-Ik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.5
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    • pp.149-156
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    • 2021
  • FRP has been proposed to replace the steel as a reinforcement in the concrete structures for addressing the corrosion issue. However, FRP-Rebar does not behave in the same manner as steel because the properties of FRP are different. For example, FRP-Rebar has a high tensile strength, low stiffness, and linear elastic behavior which results in a difference bonding mechanism to transfer the load between the reinforcement and the surrounding concrete. Therefore, bonding behavior between FRP-Rebar and concrete has to be investigated using the bonding test. So, Pull-out test has been used to estimate bond behavior because it is simple. However, the results of pull-out test have a difference with flexural-boding behavior of FRP-Rebar concrete member. So, it is needed to evaluate the real fleuxral-bonding behavior. In this study, the evaluation method to flexural-bonding behavior of FRP-Rebar concrete member was reviewed and compared. It was found that the most accurate evaluation method for the fleuxral-bonding behavior of FRP-Rebar concrete member was splice beam test, however, the size and length of specimen have to increase than other test method and the design and analysis of splice beam is complex. Meanwhile, characteristics of concrete could be reflected by using arched beam test, unlike hinged beam test which is based on the ignored change of moment arm length in equilibrium equation. However, the possibility of shear failure exists before the flexural-bonding failure occur.