• Title, Summary, Keyword: cable stiffness

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Comparison Study of Elastic Catenary and Elastic Parabolic Cable Elements for Nonlinear Analysis of Cable-Supported Bridges (케이블교량의 비선형해석을 위한 탄성현수선 및 탄성포물선 케이블요소의 비교연구)

  • Song, Yo Han;Kim, Moon Young
    • Journal of The Korean Society of Civil Engineers
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    • v.31 no.5A
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    • pp.361-367
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    • 2011
  • This study introduces an elastic parabolic cable element for initial shaping analysis of cable-supported structures. First, an elastic catenary cable theory is shortly summarized by deriving the compatibility condition and the tangent stiffness matrices of the elastic catenary cable element. Next, the force-deformation relations and the tangent stiffness matrices of the elastic parabolic cable elements are derived and discussed under the assumption that sag configuration under self-weights is small. In addition the equivalent cable tension is defined in the chord-wise direction. Finally, to demonstrate the accuracy of the elastic parabolic cable element, nonlinear relationships of nominal cable tension-chord length and nominal cable tension-tangential stiffness for a single element are presented and compared with results using an elastic catenary cable theory as the slope is varied.

Equivalent stiffness method for nonlinear analysis of stay cables

  • Xia, G.Y.;Cai, C.S.
    • Structural Engineering and Mechanics
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    • v.39 no.5
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    • pp.661-667
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    • 2011
  • In the famous equivalent elasticity modulus method proposed by Ernst for the geometrical nonlinear analysis of stay cables, the cable shape was assumed as a parabolic curve, and only a part of the gravity load normal to the chord was taken into account with the other part of gravity load parallel to the chord being ignored. Using the actual catenary curve and considering the entire gravity load of stay cables, the present study has derived the equivalent stiffness method to analyze the sag effect of stay cables in cable-stayed bridges. The derived equivalent stiffness can be degenerated into Ernst's equivalent elasticity modulus method with some approximations. Therefore, the Ernst's method is a special and approximate formulation of the present method. The derived equivalent stiffness provides a theoretical explanation for the famous Ernst's formula.

Experimental Study on the Dynamic Characteristics of Porcelain Surge Arrestor Considering the Variation of Cable's Tension and Arrestor's Stiffness (케이블 장력 및 피뢰기의 강성 변화를 고려한 애자형 피뢰기의 동특성 시험 연구)

  • Jang, Jung Bum;Hwang, Kyeong Min;Yun, Kwan Hee
    • Journal of the Earthquake Engineering Society of Korea
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    • v.18 no.5
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    • pp.253-259
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    • 2014
  • Porcelain surge arrestor is very vulnerable to earthquake but there is very few information on its dynamic characteristics which are necessary to the seismic design. Therefore, the dynamic characteristics of the porcelain surge arrestor are evaluated considering the variation of its cable tension and stiffness by shaking table test. The test results show that the first natural frequencies are 5.3 Hz and 5.2 Hz in the horizontal x- and y-axis directions, respectively, and higher than 30 Hz in the vertical z-axis direction, respectively. The installation of cable on the surge arrestor reduces the horizontal natural frequencies due to the constraint effect of the cable but cable tension has no effect on the natural frequency. Also, the natural frequency is proportional to the stiffness of the surge arrestor. This test result will be used for the seismic design and seismic capacity assessment of domestic substations and contribute to the stability of the electric power supply under earthquake event.

Full-scale test of dampers for stay cable vibration mitigation and improvement measures

  • Zhou, Haijun;Xiang, Ning;Huang, Xigui;Sun, Limin;Xing, Feng;Zhou, Rui
    • Structural Monitoring and Maintenance
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    • v.5 no.4
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    • pp.489-506
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    • 2018
  • This paper reported test of full-scale cables attached with four types of dampers: viscous damper, passive Magneto-Rheological (MR) damper, friction damper and High Damping Rubber (HDR) damper. The logarithmic decrements of the cable with attached dampers were calculated from free vibration time history. The efficiency ratios of the mean damping ratios of the tested four dampers to theoretical maximum damping ratio were derived, which was very important for practical damper design and parameter optimization. Non-ideal factors affecting damper performance were discussed based on the test results. The effects of concentrated mass and negative stiffness were discussed in detail and compared theoretically. Approximate formulations were derived and verified using numerical solutions. The critical values for non-dimensional concentrated mass coefficient and negative stiffness were identified. Efficiency ratios were approximately 0.6, 0.6, and 0.3 for the viscous damper, passive MR damper and HDR damper, respectively. The efficiency ratio for the friction damper was between 0-1.0. The effects of concentrated mass and negative stiffness on cable damping were positive as both could increase damping ratio; the concentrated mass was more effective than negative stiffness for higher vibration modes.

Nonlinear impact of negative stiffness dampers on stay cables

  • Shi, Xiang;Zhu, Songye
    • Structural Monitoring and Maintenance
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    • v.5 no.1
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    • pp.15-38
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    • 2018
  • Negative stiffness dampers (NSDs) have been proven an efficient solution to vibration control of stay cables. Although previous studies usually assumed a linear negative stiffness behavior of NSDs, many negative stiffness devices produce negative stiffness with nonlinear behavior. This paper systematically evaluates the impact of nonlinearity in negative stiffness on vibration control performance for stay cables. A linearization method based on energy equivalent principle is proposed, and subsequently, the impact of two types of nonlinear stiffness, namely, displacement hardening and softening stiffness, is evaluated. Through the Hilbert transform (HT) of free vibration responses, the effects of nonlinear stiffness of an NSD on the modal frequencies, damping ratios and frequency response functions of a stay cable is also investigated. The HT analysis results validate the accuracy of the linearization method.

Stabilities of cable-stiffened cylindrical single-layer latticed shells

  • Li, Pengcheng;Wu, Minger
    • Steel and Composite Structures
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    • v.24 no.5
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    • pp.591-602
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    • 2017
  • A cable-stiffened cylindrical single-layer latticed shell that is reinforced by cable-stiffened system has superior stability behaviour compared with the ordinary cylindrical latticed shell. The layouts of cable-stiffened system are flexible in this structural system, and different layouts contribute different stiffness to the structure. However, the existed few research primarily focused on the simplest type of cable layouts, in which the grids of the latticed shell are diagonally stiffened by prestressed cables in-plane. This current work examines the stability behaviour of the cable-stiffened cylindrical latticed shells with two different types of cable layouts using nonlinear finite element analysis. A parametric study on the effect of cross-sectional of the cables, pretension in cables, joint stiffness, initial imperfections, load distributions and boundary conditions is presented. The findings are useful for the reference of the designer in using this type of structural system.

Analysis of dry friction hysteresis in a cable under uniform bending

  • Huang, Xiaolun;Vinogradov, Oleg
    • Structural Engineering and Mechanics
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    • v.2 no.1
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    • pp.63-80
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    • 1994
  • A cable is considered as a system of helical wires and a core with distributed dry friction forces at their interfaces. Deformations of the cable subjected to a uniform bending are analyzed. It is shown that there is a critical bending curvature when a slip at the wire-core interface occurs. It originates at the neutral axis of the cross section of the cable and then spreads symmetrically over the cross section with the increase of bending. The effect of slippage on the cable stiffness is investigated. This model is also used to analyze a cable under the quasi-static cyclic bending. Explicit expression for the hysteretic losses per cycle of bending is derived. Numerical examples are given to show the influence of dry friction and helix angle on the bending stiffness and hysteretic losses in the cable.

A general method for active surface adjustment of cable net structures with smart actuators

  • Wang, Zuowei;Li, Tuanjie
    • Smart Structures and Systems
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    • v.16 no.1
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    • pp.27-46
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    • 2015
  • Active surface adjustment of cable net structures is becoming significant when large-size cable net structures are widely applied in various fields, especially in satellite antennas. A general-duty adjustment method based on active cables is proposed to achieve active surface adjustment or surface profile reconfiguration of cable net structures. Piezoelectric actuators and voice coil actuators are selected for constructing active cable structures and their simplified mechanical models are proposed. A bilevel optimization model of active surface adjustment is proposed based on the nonlinear static model established by the direct stiffness method. A pattern search algorithm combined with the trust region method is developed to solve this optimization problem. Numerical examples of a parabolic cable net reflector are analyzed and different distribution types of active cables are compared.

Analysis of thermally induced vibration of cable-beam structures

  • Deng, Han-Qing;Li, Tuan-Jie;Xue, Bi-Jie;Wang, Zuo-Wei
    • Structural Engineering and Mechanics
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    • v.53 no.3
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    • pp.443-453
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    • 2015
  • Cable-beam structures characterized by variable stiffness nonlinearities are widely found in various structural engineering applications, for example in space deployable structures. Space deployable structures in orbit experience both high temperature caused by sun's radiation and low temperature by Earth's umbral shadow. The space temperature difference is above 300K at the moment of exiting or entering Earth's umbral shadow, which results in structural thermally induced vibration. To understand the thermally induced oscillations, the analytical expression of Boley parameter of cable-beam structures is firstly deduced. Then, the thermally induced vibration of cable-beam structures is analyzed using finite element method to verify the effectiveness of Boley parameter. Finally, by analyzing the obtained numerical results and the corresponding Boley parameters, it can be concluded that the derived expression of Boley parameter is valid to evaluate the occurrence conditions of thermally induced vibration of cable-beam structures and the key parameters influencing structural thermal flutter are the cable stiffness and thickness of beams.

A Study on the Shape Optimization of the Cable-Truss Hybrid Structures (케이블-트러스 복합구조물의 형상최적화에 관한 연구)

  • Han, Sang-Eul;Jo, Nam-Chul
    • Journal of the Korean Association for Spatial Structures
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    • v.3 no.3
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    • pp.75-83
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    • 2003
  • The purpose of this study is to obtain the optimum shape of cable domes by using the real coding genetic algorithm. Generally, the structural performance of the cable domes is influenced very sensitively by pre-stress, geometry and length of the mast because of flexible system. So, it is very important to decide the optimum shape to get maximum stiffness of cable domes. We use the analytical model to verify the usefulness of this algorithm for shape optimization and analyze the roof system of Seoul olympic gymnastic arena as analytical model of a practical structures. It is confirmed lastly that the optimum shape domes have more stiffness than initial shape ones.

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