• Title, Summary, Keyword: slender structure

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New vibration control device and analytical method for slender structures

  • Takabatake, Hideo;Ikarashi, Fumiya
    • Earthquakes and Structures
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    • v.4 no.1
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    • pp.11-39
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    • 2013
  • Since slender structures such as utility poles, radio masts, and chimneys, are essentially statically determinate structures, they often collapse during earthquakes. Although vibration control is the most logical method for improving the earthquake resistance of such structures, there are many practical problems with its implementation due to their very long natural vibration period. This paper proposes a new vibration control device to effectively prevent the collapse of slender structures subjected to strong earthquakes. The device consists of a pendulum, an elastic restraint and a lever, and is designed such that when it is attached to a slender structure, the second vibration mode of the structure corresponds to the first vibration mode of the same structure without the device attached. This is highly effective in causing the transverse motions of the device and the structure to oppose each other and so reduce the overall transverse vibration during an earthquake. In the present paper, the effectiveness of the vibration control device is first evaluated based on laboratory experiments and numerical studies. An example of applying the device to a tall chimney is then simulated. A new dynamic analytical method for slender structures with abrupt rigidity variations is then proposed.

Euler Parameters Method for Large Deformation Analysis of Marine Slender Structures (오일러 매개변수를 이용한 해양 세장체 대변위 거동 해석)

  • Hong, Sup
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.163-167
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    • 2003
  • A novel method for 3-dimensional dynamic analysis of marine slender structure gas been developed by using Euler parameters. The Euler parameter rotation, which is being widely used in aerospace vehicle dynamics and multi-body dynamics, has been applied to elastic structure analysis. Large deformation of flexible slender structures is described by means of Euler parameters. Euler parameter method is implemented effectively in incremental-iterative algorithm for 3D dynamic analysis. The normalization constraint of Euler parameters is efficiently satisfied by means of a sequential updating method.

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Dynamic Responses of a Slender Offshore Structure Subject to Level Ice Load (平坦氷荷重을 받는 細長形 해양구조물의 動的 거동)

  • Choi, Kyung-Sik
    • Journal of Ocean Engineering and Technology
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    • v.9 no.2
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    • pp.156-166
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    • 1995
  • Regrading the development of offshore natural gas field near Sakhalin Island which is an ice-infested area, this study aims to estimate the dynamic ice load for construction of offshore structures operating in this region. In this paper the design ice load and dynamic responses of a slender Arctic structure upon continuous ice movement are sutdied. Crushing agter a certain elastic deformation is assumed as a primary failure mechanism at the contact zone between semi-infinite level ice edge and the face of structure. Dynamic interaction forces are calculated using a modified Korzhavin's equation and a two-dimensional ice-structure interaction model is adopted. To verify the numerical model, dynamic analysis is performed for on of the Baltic Sea channel markers whose response patterns were presiously observed.

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A Study of Vibration Control of a Slender Structure Using a Multi-Degree-of-Freedom Manipulator (다 자유도 운동장치를 이용한 세장구조물의 진동제어 연구)

  • Kim, Nak-In;Lee, Jong-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.8
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    • pp.1227-1234
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    • 2001
  • A multi d.o.f robotic manipulator is considered for multi-axis vibration control of a slender structure, using the concept of the flow source based vibration control. In order not to cause the motion saturation of the manipulator system, a hybrid dynamics associated with the flexible and desired manipulator error dynamics is also modeled as the control object. It is numerically shown that the flexible vibrations and the base motions of a test structure can be effectively controlled with the proposed hybrid dynamics.

Seismic Performance Evaluation of Steel Moment Frame Factory Building with Slender Braces (세장한 가새가 사용된 철골모멘트골조 공장시설물의 내진 성능평가)

  • Kim, Dong Yeon;Cho, Jae Chul;Hwang, Sunwoo;Kim, Taejin;Kim, Jong Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.22 no.1
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    • pp.33-43
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    • 2018
  • 'Seismic Performance Evaluation Method for Existing Buildings (2013)' developed in accordance with the overseas guidelines ASCE 41 - 06 is the most widely used procedure among domestic seismic performance evaluation guidelines in Korea. However, unlike ASCE 41 - 06, it stipulates that the final performance should be derived as the gravity load distribution ratio of the lateral force resistance system in the guideline. Therefore, in the case of a dual steel structure system with slender braces, where the internal moment frame is mostly responsible for the gravity load, the evaluation of slender braces based on gravity load distribution ratio is difficult to be achieved. In this research, we propose an objective evaluation process for such system by evaluating seismic performance for large-scale factory facilities as an example.

Study on the Measurement System of Behavior of a Slender Structure using an Underwater Camera which is applied in DOEB (심해공학수조에 적용되는 수중카메라를 이용한 세장체의 연속 거동 측정방법에 관한 연구)

  • Jung, Dong-Ho;Kwon, Yong-Ju;Park, Byeong-Won;Jung, Jae-Hwan;Choi, Jong-Su;Cho, Seok-Kyu;Sung, Hong-Gun
    • Journal of Navigation and Port Research
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    • v.42 no.1
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    • pp.1-8
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    • 2018
  • This study covers the selection of systems measuring the behaviour of the slender structure in the underwater environment and its performance assessment. From a comparison of an instrumentation system that can measure the continuous behaviour along the entire length of the slender structure, the underwater camera system is finally selected as the most appropriate semi-permanent measurement system for Deep-sea Ocean Engineering Basin of KRISO. An experiment on the rigid pipes for a basic performance evaluation of the underwater camera is conducted in this study. The motion of a top excited rigid pipe is measured with the utilization of the underwater camera system. The performance of the underwater camera is evaluated by comparing the movement of a pipe measured by the underwater camera with the measured input signals. Through the top excitation experiment for the slender structure, the real-time three-dimensional measurement of the underwater camera system is qualitatively evaluated in this case. The developed underwater camera system can apply to the system to measure dynamic behaviour of a slender structure and mooring line in Deep Ocean Engineering Basin.

Vortex-Induced Vibration of Simple Slender Structure Using Cartesian Mesh (직교격자를 이용한 단순 세장 구조물의 와유기 진동 해석)

  • Han, Myung-Ryoon;Ahn, Hyung-Teak
    • Journal of the Society of Naval Architects of Korea
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    • v.48 no.3
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    • pp.260-266
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    • 2011
  • For long slender offshore structures, such as cables and pipe lines, their interaction with surrounding fluid flow becomes an important issue for global design of ocean systems. We employ a long circular cylinder as a representative case of slender offshore structure. A flexibly mounted cylinder in cross-flow generates complex vortex shedding and results in oscillation of the structure. In this paper, flow behind a circular cylinder at Re=100 is simulated. The vortex shedding pattern and flow induced motion are examined in the cross flow configuration as well as with various yaw-angled configurations. The "Lock-in" phenomenon is also observed when reduced velocity is approximately 4.0. The MAC Grid system, which is the typical grid system for Cartesian mesh and pressure correction methods, are used for solving the incompressible Navier-Stokes equations. Predictor/Corrector method is applied for obtaining a non-linear response of structure at the flexibly mounted. The existance and motion of the body is represented by the immersed boundary technique.

Modal Identification of a Slender Structure using the Proper Orthogonal Decomposition Method (Proper Orthogonal Decomposition 기법을 이용한 세장한 구조물의 모드인자 파악)

  • Ham, Hee-Jung
    • Journal of Industrial Technology
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    • v.28 no.B
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    • pp.135-141
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    • 2008
  • In this paper, the Proper Orthogonal Decomposition (POD) method, which is a statistical analysis technique to find the modal characteristics of a structure, is adapted to identify the modal parameters of a tall chimney structure. A wind force time history, which is applied to the structure, is obtained by a wind tunnel test of a scale down model. The POD method is applied on the wind force induced responses of the structure, and the true normal modes of the structure can be obtained. The modal parameters including, natural frequency, mode shape, damping ratio and kinetic energy of the structure can be estimated accurately. With these results, it may be concluded that the POD method can be applied to obtain accurate modal parameters from the wind-induced building responses.

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Vortex excitation model. Part I. mathematical description and numerical implementation

  • Lipecki, T.;Flaga, A.
    • Wind and Structures
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    • v.16 no.5
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    • pp.457-476
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    • 2013
  • This paper presents theoretical background for a semi-empirical, mathematical model of critical vortex excitation of slender structures of compact cross-sections. The model can be applied to slender tower-like structures (chimneys, towers), and to slender elements of structures (masts, pylons, cables). Many empirical formulas describing across-wind load at vortex excitation depending on several flow parameters, Reynolds number range, structure geometry and lock-in phenomenon can be found in literature. The aim of this paper is to demonstrate mathematical background of the vortex excitation model for a theoretical case of the structure section. Extrapolation of the mathematical model for the application to real structures is also presented. Considerations are devoted to various cases of wind flow (steady and unsteady), ranges of Reynolds number and lateral vibrations of structures or their absence. Numerical implementation of the model with application to real structures is also proposed.

A comprehensive FE model for slender HSC columns under biaxial eccentric loads

  • Lou, Tiejiong;Lopes, Sergio M.R.;Lopes, Adelino V.;Sun, Wei
    • Structural Engineering and Mechanics
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    • v.73 no.1
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    • pp.17-25
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    • 2020
  • A finite element (FE) model for analyzing slender reinforced high-strength concrete (HSC) columns under biaxial eccentric loading is formulated in terms of the Euler-Bernoulli theory. The cross section of columns is divided into discrete concrete and reinforcing steel fibers so as to account for varied material properties over the section. The interaction between axial and bending fields is introduced in the FE formulation so as to take the large-displacement or P-delta effects into consideration. The proposed model aims to be simple, user-friendly, and capable of simulating the full-range inelastic behavior of reinforced HSC slender columns. The nonlinear model is calibrated against the experimental data for slender column specimens available in the technical literature. By using the proposed model, a numerical study is carried out on pin-ended slender HSC square columns under axial compression and biaxial bending, with investigation variables including the load eccentricity and eccentricity angle. The calibrated model is expected to provide a valuable tool for more efficiently designing HSC columns.