• Title/Summary/Keyword: Kinematical conditions

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Diagonal Tension Failure Model for RC Slender Beams without Shear Reinforcement Based on Kinematical Conditions (I) - Development

  • You, Young-Min;Kang, Won-Ho
    • Journal of Ocean Engineering and Technology
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    • v.21 no.6
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    • pp.7-15
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    • 2007
  • A mechanical model was developed to predict the behavior of point-loaded RC slender beams (a/d > 2.5) without stirrups. It is commonly accepted by most researchers that a diagonal tension crack plays a predominant role in the failure mode of these beams, but the failure mechanism of these members is still debatable. In this paper, it was assumed that diagonal tension failure was triggered by the concrete cover splitting due to the dowel action at the initial location of diagonal tension cracks, which propagate from flexural cracks. When concrete cover splitting occurred, the shape of a diagonal tension crack was simultaneously developed, which can be determined from the principal tensile stress trajectory. This fictitious crack rotates onto the crack tip with load increase. During the rotation, all forces acting on the crack (i.e, dowel force of longitudinal bars, vertical component of concrete tensile force, shear force by aggregate interlock, shear force in compression zone) were calculated by considering the kinematical conditions such as crack width or sliding. These forces except for the shear force in the compression zone were uncoupled with respect to crack width and sliding by the proposed constitutive relations for friction along the crack. Uncoupling the shear forces along the crack was aimed at distinguishing each force from the total shear force and clarifying the failure mechanism of RC slender beams without stirrups. In addition, a proposed method deriving the dowel force of longitudinal bars made it possible to predict the secondary shear failure. The proposed model can be used to predict not only the entire behavior of point-loaded RC slender shear beams, but also the ultimate shear strength. The experiments used to validate the proposed model are reported in a companion paper.

The Kinematical Analysis of Supported Athlete's Technical Motion in Javelin Throw (창던지기기 남자 국가대표 중점지원 선수의 기술동작 분석)

  • Lee, Soon-Ho
    • Korean Journal of Applied Biomechanics
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    • v.23 no.1
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    • pp.1-9
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    • 2013
  • The purpose of this study was to provide information on athletes' characteristics and advantages and disadvantages by analyzing the kinematic factors having a decisive influence on competitive abilities such as release conditions in the delivery phase on major Korean javelin athletes. Two supported javelin throwers of the Korean national team participated in this study. The total average time required of the delivery phase was 0.31(${\pm}0.016$). The athletes' release angle was 33.2 to 41.7 degrees. The attack angle varied widely from -3.5 to 5.9 degrees. The Javelin heights of Subject A and B were 95.9 and 89.2%Ht. The average stride length were 180.6 and 176.7cm. The center of mass velocity of LFD and REL was relatively low in all the subjects. The average deceleration rates of center of mass velocity of Subject A and B were 57.2 and 48.9%lose. The left knee angles of Subject A and B were 160.1 and 155.5 degrees in LFD, 153.0 and 164.0 degrees in REL. The joint velocity of upper limb segments was relatively low in all the subjects. The maximum average wrist velocity of Subject A and B was 18.2 and 16.3 m/s in REL.

Diagonal Tension Failure Model for RC Slender Beams without Shear Reinforcement Based on Kinematical Conditions (II) - Verification

  • You, Young-Min;Kang, Won-Ho
    • Journal of Ocean Engineering and Technology
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    • v.21 no.6
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    • pp.16-25
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    • 2007
  • In a companion paper, a rational mechanical model to predict the entire behavior of point-loaded RC slender beams (a/d > 2.5) without shear reinforcement was developed. This paper presents the test results of 9 slender shear beams and compares them with analytical results performed by the proposed model. They are grouped by two parameters, which are shear span ratio and concrete strength. Three kinds of concrete strength the 26.5, 39.2, and 58.8 MPa were included as a major experimental parameter together with different shear span ratios ranging from 3 to 6 depending on the test series. Tests were set up as a traditional 3 point bending test. Various measurements were taken to monitor abrupt shear failure. Test results were not only compared with analytical results from the proposed model, but also other formulas, to consider the various aspects of shear failure such as kinematical conditions or shear capacity. Finally, a review of the proposed model is presented with respect to the shear transfer mechanisms and the effect of test parameters. Results show that several assumptions and proposals adopted in the proposed model are rational and reasonable.

The Kinematical Analysis of Straddle Jump to Push up Motion on Sports Aerobics (스포츠 에어로빅스 Straddle Jump to Push up 동작의 운동학적 분석)

  • Kim, Cha-Nam
    • Korean Journal of Applied Biomechanics
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    • v.12 no.2
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    • pp.77-90
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    • 2002
  • This study serves the purpose of understanding about correct jump and landing motion through Kinematical Analysis of Straddle Jump to Push up Motion at target by four elite sports aerobics athletes have more than four years career. And further more that make good assistance for coaches effective guidance through an offer basic data and correct diagnosis, evaluate of motions. It was picture-taked by two-video camera for Straddle Jump to Push up Motions. Camera speeds are 60 frame/sec. There are Kinematical Variation elements for analysis, the displacement of COG, each angle displacement left/right of shoulder-joint, each angle displacement left/right of knee-joint and each speed left/right of tip of the toes. Every each person accomplished severaly 3 times and we have acquired this conclusion. The conclusions were as follows; 1. Each situation for displacement of COG showed low height of COG by phase 1, 4, 5(79.05${\pm}9.07,\;46.41{\pm}3.65,\;18.66{\pm}0.54cm$) and It showed high height of COG by phase 2, 3($120.80{\pm}6.13,\;148.12{\pm}9.19cm$). 2. Each displacement left, right of shoulder-joint flexion by phase 1($91.07{\pm}8.30,\;90.77{\pm}5.72$deg/sec)and It showed maximal extension angles by phase 2($102.48{\pm}10.00,\;102.39{\pm}10.51$deg/sec). in part of phase 3, left of shoulder-joint angle($94.43{\pm}4.12$deg/sec) showed flexion phase 1, the other right shoulder-joint angle(88.38${\pm}$4.98deg/sec) showed more a little lower than phase 1, in last phase that showed most low by phase 4($70.58{\pm}13.72,\;54.24{\pm}11.58$deg/sec). 3. Each displacement left, right of hip joint showed maximal extent conditions by phase 2, 3($160.35{\pm}22.68,\;1534.77{\pm}5.40$deg/sec, $150.04{\pm}12.79,\;145.54{\pm}13.00$deg/sec) beside, ankle-joint showed minimal angle by phase 1, 4($93.59{\pm}18.92,\;85.37{\pm}13.23$deg/sec, $66.60{\pm}15.77,\;80.60{\pm}16.57$deg/sec). 4. Each displacement left, right of hip joint showed maximal extent conditions by phase 2($157.15{\pm}9.13,\;163.52{\pm}8.18$deg/sec), and right of hip joint showed minimal angle by phase 3($110.87{\pm}13.81,\;77.53{\pm}8.95$deg/sec) It showed alike condition of low angle by phase 1, 4($91.04{\pm}2.31,\;96.26{\pm}2.20$deg/sec). 5. Each displacement left, right of knee-joint showed maximal extent conditions by phase 1, 3, 4($173.46{\pm}2.95,\;171.51{\pm}5.44$deg/sec, $172.24{\pm}4.49,\;171.26{\pm}0.65$deg/sec, $162.78{\pm}2.13,\;164.10{\pm}5.97$deg/sec) but It showed flexion only left of knee-joint by phase 2($164.45{\pm}7.51,\;159.38{\pm}3.48$deg/sec). 6. Each speed left, right of the tip of the toes showed most fastest when someone jumped with lift up leges by phase 1, 2($321.32{\pm}67.91,\;316.90{\pm}41.97$cm/sec, $410.06{\pm}153.06,\;399.77{\pm}189.34$cm/sec), It showed more less speed than phase 1,2 by phase 3($169.74{\pm}67.17,\;150.00{\pm}63.80$cm/sec) and It showed most slow speed than phase 1,2,3 by phase 4($87.22{\pm}34.90,\;85.72{\pm}52.23$cm/sec).

Analysis and Design of Steep Slope Reinforced by Soil Nail (Soil Nail에 의하여 보강된 급경사면의 해석 및 설계)

  • 이승래;김주용
    • Proceedings of the Korean Geotechical Society Conference
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    • 1993.10a
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    • pp.63-68
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    • 1993
  • Soil nailing is a method of reinforcing natural deposits of soil with passive inclusions, called nails, of steel or other materials. Its purpose is mainly to increase the tensile and shear strength of the soil mass. This method has been widely used during the last two decades to stabilize steep slopes in several countries (France, Germany, USA, Japan, etc.). The design methods that have been mostly used are Davis method, German method, and French method which are based on limit equilibrium approaches, and Juran method which utilizes the kinematical limit equilibrium design concept. This paper is focussed on the evaluation of the available design methods(especially, the France, Davis and German design methods) through comparison with each different assumption for the failure surface, the concept of failure mechanism and the definition of safety factor. The parametric study to identify the effects of design parameters on the overall factor of safety has also been conducted. By considering the results along with the associated assumptions which have been postulated in the several methods, the applicability of the method for a given soil and nail conditions has been evaluated.

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Hydroelastic vibration analysis of wetted thin-walled structures by coupled FE-BE-Procedure

  • Rohr, Udo;Moller, Peter
    • Structural Engineering and Mechanics
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    • v.12 no.1
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    • pp.101-118
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    • 2001
  • The reliable prediction of elastic vibrations of wetted complex structures, as ships, tanks, offshore structures, propulsion components etc. represent a theoretical and numerical demanding task due to fluid-structure interaction. The paper presented is addressed to the vibration analysis by a combined FE-BE-procedure based on the added mass concept utilizing a direct boundary integral formulation of the potential fluid problem in interior and exterior domains. The discretization is realized by boundary element collocation method using conventional as well as infinite boundary element formulation with analytical integration scheme. Particular attention is devoted to modelling of interior problems with both several separate or communicating fluid domains as well as thin-walled structures wetted on both sides. To deal with this specific kind of interaction problems so-called "virtual" boundary elements in areas of cut outs are placed to satisfy the kinematical conditions in partial connected fluid domains existing in realistic tank systems. Numerical results of various theoretical and practical examples demonstrate the performance of the BE-methodology presented.

Evaluation of Effective Orthotropic Creep Parameters for Perforated Sheets (다공질 박판의 유효 직교 이방성 크리프 파라미터 계산)

  • Chung Ilsup
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.2
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    • pp.79-88
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    • 2005
  • Evaluating the effective properties of materials containing various types of in-homogeneities is an important issue in the analysis of structures composed of those materials. A simple and effective method for the purpose is to impose the periodic displacement boundary conditions on the finite element model of a unit cell. Their theoretical background is explained based on the purely kinematical relations in the regularly spaced in-homogeneity problems, and the strategies to implement them into the analysis and to evaluate the homogenized material constants are introduced. The creep behavior of a thin sheet with square arrayed rectangular voids is characterized, where the orthotropy is induced by the presence of the voids. The homogenization method is validated through the comparison of the analysis of detailed model with that of the simplified one with the effective parameters.

Development of a Mathematical Model for Effect of Scoliosis Surgical Correction (구조해석을 통한 척추측만증 교정 분석에 필요한 모델 개발)

  • 김영은;최형연;손창규;이광희;이춘기
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.1059-1061
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    • 2002
  • A FE model is to develop a personalized biomechanical model of the scoliotic spine that will allow the design of clinical test providing optimal estimation of the post-operation results. A flexible multi-body model of the spine including rib cage, clavicle, and scapular was developed to simulate several mobility simulations. Vertebrae, clavicle and scapular were represented using rigid bodies and ribs and sternum were modeled as flexible bodies. Kinematical Joints and spring elements were used to represent the intervertebral disc and ligaments respectively. Postero-anterior and lateral radiographics of a scoliotic spine were used to represent a 3D reconstruction. CT data for same patient were also used to verify vertebrae rotation driven from postero-anterior and lateral radiographic images. Simulated results showed good reducibility almost uniformly distributed along the spinal segments. It was also found that boundary and loading conditions, required to mimic the operation procedures, were proven to be very sensitive parameters to its results rather than its mechanical properties

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Vibration Analysis of a Beam Translating over Supports in Vertical Motion (수직운동하는 지지대 상에서 직진운동하는 보의 진동해석)

  • 정찬교;김창부
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.10a
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    • pp.189-196
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    • 1996
  • Vibration of a beam translating over supports in vertical motion is investigated in this paper. Equations of motion are formulated using the virtual work principle by regarding the supports as kinematical constraints imposed on an unrestrained beam and by discretizing the beam via the assumed mode method. Differential-algebraic equations of motion are derived and reduced to differential equations in independent generalized coordinates by the generalized coordinate partitioning method. Geometric stiffness of the beam due to translating motion is considered and how the geometric stiffness of beam affects dynamic stability is also investigated. Instability of the beam. in various conditions is also investigated using Floquet theory and then the results are verified through the dynamic response analysis. Results of numerical simulation are presented for various prescribed motions of the beam.

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Shape sensing with inverse finite element method for slender structures

  • Savino, Pierclaudio;Gherlone, Marco;Tondolo, Francesco
    • Structural Engineering and Mechanics
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    • v.72 no.2
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    • pp.217-227
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    • 2019
  • The methodology known as "shape sensing" allows the reconstruction of the displacement field of a structure starting from strain measurements, with considerable implications for structural monitoring, as well as for the control and implementation of smart structures. An approach to shape sensing is based on the inverse Finite Element Method (iFEM) that uses a variational principle enforcing a least-squares compatibility between measured and analytical strain measures. The structural response is reconstructed without the knowledge of the mechanical properties and load conditions but based only on the relationship between displacements and strains. In order to efficiently apply iFEM to the most common structural typologies of civil engineering, its formulation according to the kinematical assumptions of the Bernoulli-Euler theory is presented. Two beam inverse finite elements are formulated for different loading conditions. Depending on the type of element, the relationship between the minimum number of required measurement stations and the interpolation order is defined. Several examples representing common applications of civil engineering and involving beams and frames are presented. To simulate the experimental strain data at the station points and to verify the accuracy of the displacements obtained with the iFEM shape sensing procedure, a direct FEM analysis of the considered structures is performed using the LUSAS software.