• Title/Summary/Keyword: dynamic column

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Seismic analysis of AL2O3 nanoparticles-reinforced concrete plates based on sinusoidal shear deformation theory

  • Amoli, Abolfazl;Kolahchi, Reza;Bidgoli, Mahmood Rabani
    • Earthquakes and Structures
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    • v.15 no.3
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    • pp.285-294
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    • 2018
  • In this study, nonlinear dynamic response of a concrete plate retrofit with Aluminium oxide ($Al_2O_3$) under seismic load and magnetic field is investigated. The plate is a composite reinforced by Aluminium oxide with characteristics of the equivalent composite being determined using Mori-Tanka model considering agglomeration effect. The plate is simulated with higher order shear deformation plate model. Employing nonlinear strains-displacements, stress-strain, the energy equations of column was obtained and using Hamilton's principal, the governing equations were derived. Differential quadrature method (DQM) in conjunction with Newark method is applied for obtaining the dynamic response of structure. The influences of magnetic field, volume percent of nanoparticles, geometrical parameters of column, agglomeration and boundary conditions on the dynamic response were investigated. Results showed that with increasing volume percent of nanoparticles, the dynamic deflection decreases.

Dynamic Stability Analysis of Clamped-Hinged Columns with Constant Volume (일정체적 고정-회전 기둥의 동적안정 해석)

  • Kim, Suk-Ki;Lee, Byoung-Koo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.10 s.115
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    • pp.1074-1081
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    • 2006
  • This paper deals with the dynamic stability analysis of clamped-hinged columns with constant volume. Numerical methods are developed for solving natural frequencies and buckling loads of such columns, subjected to an axial compressive load. The parabolic taper with the regular polygon cross-section is considered, whose material volume and column length are always held constant. Differential equations governing both free vibrations and buckled shapes of such columns are derived. The Runge-Kutta method is used to integrate the differential equations, and the Regula-Falsi method is used to determine natural frequencies and buckling loads, respectively. The numerical methods developed herein for computing natural frequencies and buckling loads are found to be efficient and robust. From the numerical results, dynamic stability regions, dynamic optimal shapes and configurations of strongest columns are reported in figures and tables.

Identification of progressive collapse pushover based on a kinetic energy criterion

  • Menchel, K.;Massart, T.J.;Bouillard, Ph.
    • Structural Engineering and Mechanics
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    • v.39 no.3
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    • pp.427-447
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    • 2011
  • The progressive collapse phenomenon is generally regarded as dynamic. Due to the impracticality of nonlinear dynamic computations for practitioners, an interest arises for the development of equivalent static pushover procedures. The present paper proposes a methodology to identify such a procedure for sudden column removals, using energetic evaluations to determine the pushover loads to apply. In a dynamic context, equality between the cumulated external and internal works indicates a vanishing kinetic energy. If such a state is reached, the structure is sometimes assumed able to withstand the column removal. Approximations of these works can be estimated using a static computation, leading to an estimate of the displacements at the zero kinetic energy configuration. In comparison with other available procedures based on such criteria, the present contribution identifies loading patterns to associate with the zero-kinetic energy criterion to avoid a single-degree-of-freedom idealisation. A parametric study over a family of regular steel structures of varying sizes uses non-linear dynamic computations to assess the proposed pushover loading pattern for the cases of central and lateral ground floor column failure. The identified quasi-static loading schemes are shown to allow detecting nearly all dynamically detected plastic hinges, so that the various beams are provided with sufficient resistance during the design process. A proper accuracy is obtained for the plastic rotations of the most plastified hinges almost independently of the design parameters (loads, geometry, robustness), indicating that the methodology could be extended to provide estimates of the required ductility for the beams, columns, and beam-column connections.

Kinematic Analysis of Dynamic Stability Toward the Pelvis-spine Distortion during Running (달리기 시 체간의 골반-척추구조변형이 동적안정성에 미치는 연구)

  • Park, Gu-Tae;Yoo, Kyoung-Seok
    • Korean Journal of Applied Biomechanics
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    • v.23 no.4
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    • pp.369-376
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    • 2013
  • The purposes of this study were to assess dynamic stability toward pelvis-spine column distortion during running and to compare the typical three-dimensional angular kinematics of the trunk motion; cervical, thoracic, lumbar segment spine and the pelvis from the multi-segmental spine model between exercise group and non-exercise group. Subjects were recruited as exercise healthy women on regular basis (group A, n=10) and non-exercise idiopathic scoliosis women (group B, n=10). Data was collected by using a vicon motion capture system (MX-T40, UK). The pelvis, spine segments column and lower limbs analysiaed through the 3D kinematic angular ROM pattern. There were significant differences in the time-space variables, the rotation motion of knee joint in lower limbs and the pelvis variables; obliquity in side bending, inter/outer rotation in twisting during running leg movement. There were significant differences in the spinal column that is lower-lumbar, upper-lumbar, upper-thoracic, mid-upper thoracic, mid-lower thoracic, lower thoracic and cervical spine at inclination, lateral bending and twist rotation between group A and group B (<.05, <.01 and <.001). As a results, group B had more restrictive motion than group A in the spinal column and leg movement behaved like a 'shock absorber". And the number of asymmetry index (AI) showed that group B was much lager unbalance than group A. In conclusion, non-exercise group was known to much more influence the dynamic stability of equilibrium for bilateral balance. These finding suggested that dynamic stability aimed at increasing balance of the trunk ROM must involve methods and strategies intended to reduce left/right asymmetry and the exercise injury.

Characteristics of Hysteretic Behavior of Circular Steel Column using SM490 for Loading Rate (재하속도에 따른 SM490강재 원형강기둥의 이력거동 특성)

  • Jang, Gab Chul;Chang, Kyong Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.6A
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    • pp.935-941
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    • 2006
  • The hysteretic behavior of steel structure under cyclic and dynami loading such as earthquake is different to that under static loading. Because structural steels on dynamic deformation is different to static deformation with respect with mechanical characteristics and stress-strain relationship. Therefore, to accurately predict the hysteretic behavior of steel structures such as circular steel columns under cyclic and dynamic loading, the difference of loading carrying capacity and deformation according to loading rate, assumed static and dynamic deformation state, must be investigated. In this study, numerical analyses of circular steel column using SM490 for change of loading rate and diameter-thickness ratio(D/t) were carried out by using three-dimensional elastic-plastic finite element analysis and dynamic cyclic plasticity model of SM490 developed by the authors. Characteristics of hysteretic behavior of circular steel column using SM490, load carrying capacity and energy dissipation ratio, were clarified by analysis results.

Characteristics of Dynamic Properties of Granite Specimen from Chungnam Yeongi Area (충남 연기군 지역 화강암 시험편의 동적물성 특성에 관한 연구)

  • Min, June-Hyun;Lee, Seung-Joong;Choi, Sung-O.
    • Tunnel and Underground Space
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    • v.21 no.6
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    • pp.480-493
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    • 2011
  • Dynamic rock property is one of most important parameters in design of earthquake-resistant structures. In this study, free-free resonant column test has been conducted to obtain dynamic Young's modulus, dynamic shear modulus, and damping ratio among dynamic properties with granite specimen of Chungnam Yeongi area. The dynamic properties obtained from this test were compared with the physical properties from static rock tests, and their relationship has been analyzed. From our study, it has been concluded that the dynamic Young's modulus and the dynamic shear modulus are linearly proportional to the elastic wave velocity. And also the damping ratio has been identified to be in non-linear inverse proportion to the elastic wave velocity.

Dense Optical flow based Moving Object Detection at Dynamic Scenes (동적 배경에서의 고밀도 광류 기반 이동 객체 검출)

  • Lim, Hyojin;Choi, Yeongyu;Nguyen Khac, Cuong;Jung, Ho-Youl
    • IEMEK Journal of Embedded Systems and Applications
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    • v.11 no.5
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    • pp.277-285
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    • 2016
  • Moving object detection system has been an emerging research field in various advanced driver assistance systems (ADAS) and surveillance system. In this paper, we propose two optical flow based moving object detection methods at dynamic scenes. Both proposed methods consist of three successive steps; pre-processing, foreground segmentation, and post-processing steps. Two proposed methods have the same pre-processing and post-processing steps, but different foreground segmentation step. Pre-processing calculates mainly optical flow map of which each pixel has the amplitude of motion vector. Dense optical flows are estimated by using Farneback technique, and the amplitude of the motion normalized into the range from 0 to 255 is assigned to each pixel of optical flow map. In the foreground segmentation step, moving object and background are classified by using the optical flow map. Here, we proposed two algorithms. One is Gaussian mixture model (GMM) based background subtraction, which is applied on optical map. Another is adaptive thresholding based foreground segmentation, which classifies each pixel into object and background by updating threshold value column by column. Through the simulations, we show that both optical flow based methods can achieve good enough object detection performances in dynamic scenes.

Static and Dynamic Optimal Shapes of Both Clamped Columns with Constant Volume (일정체적 양단고정 기둥의 정·동적 최적형상)

  • Lee, Byoung Koo;Kim, Suk Ki
    • Journal of Korean Society of Steel Construction
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    • v.19 no.1
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    • pp.99-106
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    • 2007
  • This paper deals with the static and dynamic optimal shapes of both clamped columns with constant volume. The parabolic taper with the regular polygon cross-section is considered, whose material volume and column length are held constant. Numerical methods are developed for solving natural frequencies and buckling loads of columns subjected to an axial compressive load. Differential equations governing the free vibrations of such column are derived. The Runge-Kutta method is used to integrate the differential equations, and the Regula-Falsi method is used to determine natural frequencies and buckling loads, respectively. From the numerical results, dynamic stability regions, dynamic optimal shapes and configurations of strongest columns are presented in figures and tables.

An Efficient Service Function Chains Orchestration Algorithm for Mobile Edge Computing

  • Wang, Xiulei;Xu, Bo;Jin, Fenglin
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.15 no.12
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    • pp.4364-4384
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    • 2021
  • The dynamic network state and the mobility of the terminals make the service function chain (SFC) orchestration mechanisms based on static and deterministic assumptions hard to be applied in SDN/NFV mobile edge computing networks. Designing dynamic and online SFC orchestration mechanism can greatly improve the execution efficiency of compute-intensive and resource-hungry applications in mobile edge computing networks. In order to increase the overall profit of service provider and reduce the resource cost, the system running time is divided into a sequence of time slots and a dynamic orchestration scheme based on an improved column generation algorithm is proposed in each slot. Firstly, the SFC dynamic orchestration problem is formulated as an integer linear programming (ILP) model based on layered graph. Then, in order to reduce the computation costs, a column generation model is used to simplify the ILP model. Finally, a two-stage heuristic algorithm based on greedy strategy is proposed. Four metrics are defined and the performance of the proposed algorithm is evaluated based on simulation. The results show that our proposal significantly provides more than 30% reduction of run time and about 12% improvement in service deployment success ratio compared to the Viterbi algorithm based mechanism.

Experimental Study on Natural Period for Arch Structure with Column (하부기둥에 따른 아치구조물의 고유주기 변화에 관한 실험적 연구)

  • Kang, Joo-Won;Seok, Keun-Yung;Lee, Sang-Hoon;Kim, Gee-Cheol
    • Journal of Korean Association for Spatial Structures
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    • v.9 no.2
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    • pp.83-90
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    • 2009
  • The previous studies for dynamic behavior of spatial structure have been zoomed in on roof structure by numerical analytic method. But the roof structure of real spatial structures is supported by lower structure as column and wall. So, when earthquake is occurred, it is predicted that dynamic behavior of roof structure is affected by lower structure. Therefore, on this study, natural period characteristics of arch structures are analyzed according to section, length and the modulus of elasticity of brass column and polycarbonate column and additional mass of roof structure by the scale-down model of arch structure as the most simple structure of spatial structures. The changes of natural periods are generally alike. But, when Polycarbonate column is connected to roof structure, the change of natural period for change of section is relatively large. That means that change of section and section and length of column and additional mass of roof structure have less influence on change of stiffness because the modulus of elasticity of brass is relatively large.

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