• Title, Summary, Keyword: cable stiffness

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Lagrangian Formulation of a Geometrically Exact Nonlinear Frame-Cable Element (기하 비선형성을 엄밀히 고려한 비선형 프레임-케이블요소의 정식화)

  • Jung, Myung-Rag;Min, Dong-Ju;Kim, Moon-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.3
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    • pp.195-202
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    • 2012
  • Two nonlinear frame elements taking into account geometric nonlinearity is presented and compared based on the Lagrangian co-rotational formulation. The first frame element is believed to be geometrically-exact because not only tangent stiffness matrices is exactly evaluated including stiffness matrices due to initial deformation but also total member forces are directly determined from total deformations in the deformed state. Particularly two exact tangent stiffness matrices based on total Lagrangian and updated Lagrangian formulation, respectively, are verified to be identical. In the second frame element, the deformed curved shape is regarded as the polygon and current flexural deformations in iteration process are neglected in evaluating tangent stiffness matrices and total member forces. Two numerical examples are given to demonstrate the accuracy and the good performance of the first frame element compared with the second element. Furthermore it is shown that the first frame element can be used in tracing nonlinear behaviors of cable members.

Approximate calculation of the static analysis of a lifted stay cable in super-long span cable-stayed bridges

  • Zhao, Xinwei;Xiao, Rucheng;Sun, Bin
    • Structural Engineering and Mechanics
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    • v.74 no.5
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    • pp.635-655
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    • 2020
  • The sag effect of long stay cables is one of the key factors restricting further increase in the span of cable-stayed bridges. Based on the formerly proposed concept of long stay cables lifted by an auxiliary suspension cable in cross-strait cable-stayed bridges, corresponding static approximate calculations and analytical theory based on catenary and parabolic cable configurations are established. Taking a main span 1400 m cable-stayed bridge as the research object, three typical lifting conditions and the whole process of auxiliary cable lifting are analyzed and discussed. The results show that the sag effect is effectively reduced. The support efficiency is only improved when the cables are lifted above the original cable chord. Reduction of the horizontal component force of the cable is limited. The equivalent elastic modulus and the vertical support stiffness of the lifted cables are significantly increased with increased horizontal projection length and not sensitive to the change of the lifting point position. The scheme of lifting the cable to the chord midpoint is more economical because of the less steel required for the auxiliary suspension cable, but its effect on improving the vertical support efficiency is limited. The support efficiency is better when the cable is lifted to the cable end tangential to the original cable chord, but the lifting force and the cross-sectional area of the auxiliary suspension cable are doubled. The approximate calculation results of the lifted cables are very close to the numerical analysis results, which verifies the applicability of the approximation method proposed in this study. The results of parabolic approximation calculations are approximately equal to that of catenary cable geometry. As the parabolic approximation analysis theory of lifted cables is more convenient in mathematical processing, it is feasible to use parabolic approximation analysis theory as the analytical method for the conceptual design of lifted cables of super-long span cable-stayed bridges.

Nonlinear Behaviors of Cable Spoke Wheel Roof Systems (케이블 스포크 휠 지붕 시스템의 비선형 거동)

  • Park, Kang-Geun;Lee, Mi-Hyang;Park, Mi-Jin
    • Journal of the Korean Association for Spatial Structures
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    • v.17 no.1
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    • pp.31-40
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    • 2017
  • The objective of this study is to analysis the mechanical characteristics and nonlinear behaviors on the geometric nonlinear behavior of a cable spoke wheel roof system for long span lightweight roof structures. The weight of a cable spoke wheel roof dramatically can reduce and the cable roof system can easily make the required rigidity and shape by the sag ratio and pretension forces. Determining the pretension and initial sag of cable roof system is essential in a design process and the shape of roof is changed by pretension. The nonlinear behavior of flexible cable system has greatly an affect on the sag and pretension. This paper will be carried out analyzing and comparing the tensile forces and deflection of a cable spoke wheel system for the large span retractable roof, and analyzed to deflections and tensile forces by the post height of center hub. The double arrangement of a spoke wheel system with reverse curvature works more effectively as a load bearing system, the pretension can easily increase the structural stiffness. The cable truss system can carry vertical load in up and downward direction, and act effectively as load bearing elements.

Stiffiness Analysis and Optimization of Strand and Wire Rope (스트랜드와 와이어 로프의 강성해석 및 최적화)

  • Heo, Seong-Pil;Yang, Won-Ho;Seong, Gi-Deuk;Jo, Myeong-Rae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.5
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    • pp.1246-1253
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    • 2000
  • Wire ropes are widely used in cable car, suspension bridge and elevator, etc. and there has been a growing need for ropes of large diameter. The theoretical procedures to obtain the stiffness coefficients of wire ropes, using previously reported theory, are programmed and the verification of the program is made. The effects of lay angle on the stiffness of strand are researched and comparisons on stiffness of rope are made according to the lay type. Axial stiffness optimization problems with coupling and torsional stiffness constraints are formulated and the effects of constraints on other stiffness coefficients on axial stiffness optimization are investigated.

Seismic Protection of Cable-stayed Bridges Using LRB and MR Damper (납-고무받침과 자기유변유체 감쇠기를 이용한 사장교의 내진제어)

  • 정형조;박규식;이인원
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.241-245
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    • 2003
  • This paper presents the LRB-based hybrid base isolation system employing additional semiactive control devices for seismic protection of cable-stayed bridges by examining the ASCE first generation benchmark problem for a cable-stayed bridge. In this study, ideal magnetorheological dampers (MRDs) are considered as additional semiactive control devices. Numerical simulation results show that the hybrid base isolation system is effective in reducing the structural responses of the benchmark cable-stayed bridge under the historical earthquakes considered. The simulation results also demonstrate that the hybrid base Isolation system employing semiactive MRDs is robust to the stiffness uncertainty of the structure. Therefore, the LRB-based hybrid base isolation system employing MRDs could be appropriate in real applications for full-scale civil infrastructures.

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Stress Properties for Anchorage Zone of Cable Stayed Bridge Prestress Concrete (프리스트레스트 콘크리트 사장교 정착부의 응력특성)

  • 조병완;변윤주;최준혁;태기호
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.531-536
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    • 2002
  • The design of anchorage zone in prestressed concrete cable stayed bridges is very important area due to the more accurate analysis is needed to estimate the behavior. In the study, since the cable anchorage zone in the prestressed concrete cable-stayed bridge is subject to a large amount of concentrated tendon forces, it shows very complicated stress distributions and causes a serious local cracks. Accordingly, It is necessary to investigate the parameters of affecting the stress distribution, such as the cable inclination, the position of anchor plate, the modeling method and the three dimensional effect. The tensile stress distribution of anchorage zone is compared to the actual design condition by varing the stiffness of spring element in the local modeling and an appropriate position of anchor plate is determined. These results would be elementary data to the stress state of anchorage zone and more efficient design.

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A Study on the Static Instability Behaviour of the Zetlin Type Cable Dome Structures (Zetlin형 케이블 돔 구조물의 정적 불안정 거동에 관한 연구)

  • 김형석;김승덕;강문명
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.541-548
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    • 2002
  • Membrane, cable structure and membrane-cable structural system are more lighter than another common structural system, and these are able to be effectively build Lip spatial structures using axial stiffness. However when the load reach at critical load level, it might be happened snap-through or bifurcation according to the structure's shape, and these collapse mechanism should be very important in the design of structures. So, In this paper we study static instability of Zetlin-type cable dome, one of the hybrid cable dome. Moreover, as the unstable behavior of shell structures are very sensitive to the initial condition, we seek to find the effect of initial condition.

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Geometrically Nonlinear Dynamic Analysis of Cable Domes (케이블 돔의 기하학적 비선형 동적해석)

  • 한상을;서준호;김종범
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.61-68
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    • 2003
  • Cable domes deform very largely because of the characteristics of flexible hybrid system and pre-tension, and include geometrical non-linearity in those structural behavior. Especially wind load is more dominant than seismic loads, because cable domes are flexible structures whose stiffness is very small and self-weight is very light. Therefore, in this paper, Modified Stiffly Stable Method is applied to analyze the nonlinear dynamic behavior of cable domes and compared these results with ones of Newmark-β Method which is generally used. The Seoul Olympic Gymnastic Arena is taken as an numerical example and three kinds of models with giving each different intensity of pre-tension are selected. And dynamic nonlinear behavior of cable domes are analyzed by artificial spectrum of wind velocity wave which is similar to actual wind loads.

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A Study on the Slipping Problem for Cable-Membrane Structures (케이블-막구조물의 요소이동(slip)에 관한 연구)

  • Kim, Jae-Yeol;Kang, Joo-Won;Park, Sang-Min
    • Journal of the Korean Association for Spatial Structures
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    • v.8 no.5
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    • pp.95-105
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    • 2008
  • The objective of this study is find out the stressed condition, slipped direction and slipped dimension when some elements of cable-membrane structures are slipped from it's initially designed coordinates by external loads as wind or non uniform load and so on. In order to search the slipped behaviors of cable-membrane structures, a ALE finite element formulation is introduced. In these procedures, a stiffness matrix related with ALE concept is formulated and a FE analysis program for cable-membrane structures with slipped elements is developed.

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Impact of cable sag on the efficiency of an inertial mass damper in controlling stay cable vibrations

  • Wang, Zhi-hao;Gao, Hui;Xu, Yan-wei;Chen, Zheng-qing;Wang, Hao
    • Smart Structures and Systems
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    • v.24 no.1
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    • pp.83-94
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    • 2019
  • Passive negative stiffness dampers (NSDs) that possess superior energy dissipation abilities, have been proved to be more efficient than commonly adopted passive viscous dampers in controlling stay cable vibrations. Recently, inertial mass dampers (IMDs) have attracted extensive attentions since their properties are similar to NSDs. It has been theoretically predicted that superior supplemental damping can be generated for a taut cable with an IMD. This paper aims to theoretically investigate the impact of the cable sag on the efficiency of an IMD in controlling stay cable vibrations, and experimentally validate superior vibration mitigation performance of the IMD. Both the numerical and asymptotic solutions were obtained for an inclined sag cable with an IMD installed close to the cable end. Based on the asymptotic solution, the cable attainable maximum modal damping ratio and the corresponding optimal damping coefficient of the IMD were derived for a given inertial mass. An electromagnetic IMD (EIMD) with adjustable inertial mass was developed to investigate the effects of inertial mass and cable sag on the vibration mitigation performance of two model cables with different sags through series of first modal free vibration tests. The results show that the sag generally reduces the attainable first modal damping ratio of the cable with a passive viscous damper, while tends to increase the cable maximum attainable modal damping ratio provided by the IMD. The cable sag also decreases the optimum damping coefficient of the IMD when the inertial mass is less than its optimal value. The theoretically predicted first modal damping ratio of the cable with an IMD, taking into account the sag generally, agrees well with that identified from experimental results, while it will be significantly overestimated with a taut-cable model, especially for the cable with large sag.