• 제목/요약/키워드: Eccentric Moment

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Thermotherapy and Dynamic Warm-up on the Kinetic Parameters during Drop-landing (드롭랜딩 시 국소부위 온열처치와 동적 준비운동이 하지의 운동역학적 변인에 미치는 영향)

  • Kim, Sungmin;Song, Jooho;Han, Sanghyuk;Moon, Jeheon
    • Korean Journal of Applied Biomechanics
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    • 제31권4호
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    • pp.297-307
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    • 2021
  • Objective: The aim of this study was to analyze kinetic variables between thermotherapy and dynamic warm-up during drop-landing. Method: Twenty male healthy subjects (Age: 21.85 ± 1.90 years, Height: 1.81 ± 0.06 cm, Weight: 68.5 ± 7.06 kg) underwent three treatments applied on the thermotherapy of femoral muscles and a dynamic warm-up. The thermotherapy was performed for 15 minutes while sitting in a chair using an electric heating pad equipped with a temperature control device. Dynamic warm-up performed 14 exercise, a non-treatment was sitting in a chair for 15 minutes. Core temperature measurements of all subjects were performed before landing at a height of 50 cm. During drop-landing, core temperature, joint angle, moment, work of the sagittal plane was collected and analyzed. All analyses were performed with SPSS 21.0 and for repeated measured ANOVA and Post-hoc was Bonferroni. Results: Results indicated that Thermotherapy was increased temperature than other treatments (p = .000). During drop-landing, hip joint of dynamic warm-up was slower for angular velocity (p < .005), and left ankle joint was fastest than other treatments (p = .004). Maximum joint moment of dynamic warm-up was smaller for three joints (hip extension: p = .000; knee flexion/extension: p = .001/.000; ankle plantarflexion: p = .000). Negative work of dynamic warm-up was smaller than other treatments (p = .000). Conclusion: In conclusion, the thermotherapy in the local area doesn't affect the eccentric contraction of the thigh. The dynamic warm-up treatment minimized the joint moment and negative work of the lower joint during an eccentric contraction, it was confirmed that more active movement was performed than other treatment methods.

Alterations in the Neuro-Mechanical Properties of Human Ankle Dorsiflexor after Maximum Eccentric Exercise (최대 신장성 수축운동에 따른 인체 하지 족배굴곡근의 신경-기계학적 특성 변화)

  • Lee, Hae-Dong;Kim, Seung-Jae;Kawakami, Yasuo
    • Korean Journal of Applied Biomechanics
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    • 제18권4호
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    • pp.21-30
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    • 2008
  • The purpose of this study was to investigate changes in mechanical properties of human tibialis anterior following eccentric exercise. Healthy subjects (n=12) performed 120 maximum eccentric contraction of ankle dorsiflexor. Before and 1- and 24- hour after the eccentric exercise, ankle dorsiflexion moment-angle relationships were obtained. Along with significant decrease in maximum isometric muscle strength, the shift of the optimum ankle joint angle toward the longer muscle length direction was observed, independent of the ranges of motion of the eccentric exercise. The results of this study demonstrated that eccentric exercise-induced micro muscle damage(Morgan & Allen, 1999) does rut seem to be a sole mechanism of eccentric contraction-induced muscle damage, suggesting further investigation for the better understandings of this phenomenon.

Effect of Torsional Eccentricity on the Seismic Response of High-Rise RC Bearing-Wall Structures with Vertical Irregularity (고층 RC 벽식 비정형 구조물의 지진반응에 대한 비틀림 편심의 효과)

  • 고동우;이한선
    • Proceedings of the Korea Concrete Institute Conference
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    • 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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    • pp.145-150
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    • 2003
  • The objective of this study is to investigate the effect of torsional eccentricity on the seismic response of high-rise RC bearing-wall structures with vertical irregularity. For this purpose, two 1:12 scale 17-story RC model structures, the one has concentric shear wall and the other has eccentric shear wall, were constructed and then subjected to a series of earthquake excitations. The test result shows the followings: 1) the layout of shear wall has the negligible effect on the natural period and the base shear coefficient, 2) the eccentric model behaves in the first and second mode while the concentric model has the first mode predominantly, 3) the stiff frame in the eccentric model resists most of overturning moment in the severe earthquake though both frames (the stiff and flexible frames) resist almost equally in the design earthquake.

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Eccentric compressive behavior of novel composite walls with T-section

  • Qin, Ying;Chen, Xin;Xi, Wang;Zhu, Xingyu;Chen, Yuanze
    • Steel and Composite Structures
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    • 제35권4호
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    • pp.495-508
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    • 2020
  • Double skin composite walls are alternatives to concrete walls to resist gravity load in structures. The composite action between steel faceplates and concrete core largely depends on the internal mechanical connectors. This paper investigates the structural behavior of novel composite wall system with T section and under combined compressive force and bending moment. The truss connectors are used to bond the steel faceplates to concrete core. Four short specimens were designed and tested under eccentric compression. The influences of the thickness of steel faceplates, the truss spacing, and the thickness of web wall were discussed based on the test results. The N-M interaction curves by AISC 360, Eurocode 4, and CECS 159 were compared with the test data. It was found that AISC 360 provided the most reasonable predictions.

Buckling behavior of stainless steel square hollow columns under eccentric loadings

  • Jang, Ho-Ju;Seo, Seong-Yeon;Yang, Young-Sung
    • Structural Engineering and Mechanics
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    • 제23권5호
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    • pp.563-577
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    • 2006
  • This study involves a series of experiments on the buckling strength of eccentrically compressed cold-formed stainless steel square hollow-section columns. The principal parameters in this study are slenderness ratios ($L_k/r$ = 30, 50, 70) and magnitude of eccentricity e (0, 25, 50, 75, 100 mm) on the symmetrical end-moment. The objectives of this paper are to obtain the buckling loads by conducting a series of experiments and to compare the behavior of the eccentrically compressed cold-formed stainless steel square hollow-section columns with the results of the analysis. The ultimate buckling strength of the square-section members were determined with the use of a numerical method in accordance with the bending moment-axial force (M-P) interaction curves. The behavior of each specimen was displayed in the form of a moment-radian (M-${\theta}$) relationship. The numerically obtained ultimate-buckling interaction curves of the beam columns coincided with the results of the experiments.

Strength of Interior Plat Plate-Column Connections Subjected to Unbalanced Moment (불균등 휨모멘트를 받는 플랫 플레이트-기둥 접합부의 강도산정모델)

  • 최경규;박홍근
    • Journal of the Korea Concrete Institute
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    • 제14권6호
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    • pp.961-972
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    • 2002
  • Flat plate structures under lateral load are susceptible to the brittle shear failure of plate-column connection. To prevent such brittle failure, strength and ductility of the connection should be ensured. However, according to previous studies, current design methods do not accurately estimate the strength of plate-column connection. In the present study, parametric study using nonlinear finite element analysis was performed for interior connections. Based on the numerical results, a design method for the connection was developed. At the critical sections around the connection coexist flexural moment and shear developed by lateral and gravity loads, and maximum allowable eccentric shear stresses were proposed based on the interactions between the flexural moment and shear, The proposed method can precisely predict the strength of the connection, compared with the current design provisions. The predictability of the proposed method was verified by the comparisons with existing experiments and nonlinear numerical analyses.

Experimental Study on Secondary Moment of High-Strength RC Slender Columns under Eccentric Loads (편심을 받는 고강도콘크리트 장주의 2차모멘트에 관한 실험적 연구)

  • 박동규;배성용;이재훈
    • Proceedings of the Korea Concrete Institute Conference
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    • 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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    • pp.571-576
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    • 1998
  • This paper is a part of a research plan aimed at the verification of basic design rules of high-strength concrete columns. A total of 19 slender column specimens were tested to measure secondary moment and stiffness of eccentrically loaded reinforced concrete tied columns. Main variables included in this test program were concrete compressive strength, steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 356kg/$\textrm{cm}^2$ to 951kg/$\textrm{cm}^2$, the longitudinal steel ratios were between 1.13% and 5.51%, and slenderness ratios were 40 and 61. Calculated moment magnification factors and column stiffness based on design codes are higher than the test results for high axial load under small eccentricity, for higher slenderness ratio, for lower longitudinal steel ratio, and for high-strength concrete. The moment magnification method of the current design codes may provide a very conservative design for high-strength concrete slender column.

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Creep analysis of concrete filled steel tube arch bridges

  • Wang, Y.F.;Han, B.;Du, J.S.;Liu, K.W.
    • Structural Engineering and Mechanics
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    • 제27권6호
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    • pp.639-650
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    • 2007
  • Applying the method calculating creep of Concrete Filled steel Tube (CFT) members based on the Elastic Continuation and Plastic Flow theory for concrete creep with the finite element method, the paper develops a new numerical method for the creep of CFT arch bridges considering effects of bending moment. It is shown that the method is feasible and reasonable through comparing the predicted stresses and deflection caused by the creep with the results obtained by the method of Gu et al. (2001) based on ACI209R model and experimental data of an actual CFT arch bridge. Furthermore, nine CFT arch bridges with different types are calculated and analyzed with and without the effects of bending moment. As a result, the bending moment has considerable influences on long-term deformations and internal forces of CFT arch bridges, especially when the section of arch rib is subjected to a large bending moment.

Elasto-plastic behaviour of perforated steel plates subjected to compression and bending

  • Maiorana, Emanuele;Pellegrino, Carlo;Modena, Claudio
    • Steel and Composite Structures
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    • 제11권2호
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    • pp.131-147
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    • 2011
  • The aim of this work is to provide some insights into the elasto-plastic behaviour of plate girder web square and rectangular panels with centred and eccentric holes under both compression and in-plane bending moment. The numerical study was validated comparing the numerical results obtained for one simple steel plate configuration with the corresponding experimental results, obtained at the University of Padova, observing the influence of the initial out-of-plane imperfections on the force vs. displacement relationship and ultimate strength. Once validated the numerical approach, the effect of bending moment on the stability of the plate is studied and some differences with respect to the uniform compression load case are shown. The influence of dimension and position of the hole, the plate aspect ratio and the steel grade on elasto-plastic behaviour is observed. Some indications regarding the critical slenderness (at which transition from elastic to plastic collapse occurs) are given for square and rectangular plates with symmetric and eccentric holes having small, medium and large diameter.

Shear strength formula of CFST column-beam pinned connections

  • Lee, Seong-Hui;Kim, Young-Ho;Choi, Sung-Mo
    • Steel and Composite Structures
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    • 제13권5호
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    • pp.409-421
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    • 2012
  • Recently, as the height of building is getting higher, the applications of CFST column for high-rise buildings have been increased. In structural system of high-rise building, The RC core and exterior concrete-filled tubular (CFST) column-beam pinned connection is one of the structural systems that support lateral load. If this structural system is used, due to the minimal CFST column thickness compared to that of the CFST column width, the local moment occurred by the eccentric distance between the column flange surface from shear bolts joints degrades the shear strength of the CFST column-beam pinned connections. This study performed a finite element analysis to investigate the shear strength under eccentric moment of the CFST column-beam pinned connections. The column's width and thickness were used as variables for the analysis. To guarantee the reliability of the finite element analysis, an actual-size specimens were fabricated and tested. The yield line theory was used to formulate an shear strength formula for the CFT column-beam pinned connection. the shear strength formula was suggested through comparison on the results of FEM analysis, test and yield lime theory, the shear strength formula was suggested.