• Title/Summary/Keyword: unstrained length

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A Study on Determination of Cable-Tension Using Unstrained-Length-Modification Method (초기길이 수정법(ULMM)을 이용한 케이블 장력 결정에 관한 연구)

  • Kong, Min Sik;An, Chan Hyeog;Yhim, Sung Soon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.2
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    • pp.113-120
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    • 2008
  • This study presents the ULMM(unstrained-length-modification method) to determine the cable tension consistent with target tension after arrangement of cable-members by controlling the unstrained length of cables. This method used to be shown to determine the exact unstrained length for cable-supported bridge with elastic catenary cable. The some verification examples show to determine the unstrained length that satisfies the target tension and to obtain the satisfactory result for cable-supported bridge. Accordingly this modification method of the unstrained length in this study is used to introduce the satisfactory target tension.

Construction Stage Analysis of Cable-Stayed Bridges Using the Unstrained Element Length Method (무응력길이법을 이용한 사장교의 시공단계 해석)

  • Park, Se Woong;Jung, Myung Rag;Min, Dong Ju;Kim, Moon Young
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.6
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    • pp.991-998
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    • 2016
  • The propose of this study is to demonstrate how efficiently and accurately the construction stages of cable-stayed bridges are analyzed using the unstrained length method (ULM) in which all unstrained element lengths are determined from a simplified analytical method (Jung et al., 2015). A forward analysis of cable-stayed bridges using the commercial FEA program, MIDAS is sequentially carried out considering the lack of fit force but the ULM is able to analyze a intermediate construction stage directly by taking the corresponding unstrained lengths of the construction stage model simply. The closing load step analysis is achieved by loading the pavement and counter weight forces in reverse. An Incheon bridge model is analyzed using the present ULM and the commercial program, respectively, and the two analysis results are compared.

Analytical methods for determining the cable configuration and construction parameters of a suspension bridge

  • Zhang, Wen-ming;Tian, Gen-min;Yang, Chao-yu;Liu, Zhao
    • Structural Engineering and Mechanics
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    • v.71 no.6
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    • pp.603-625
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    • 2019
  • Main cable configurations under final dead load and in the unloaded state and critical construction parameters (e.g. unstrained cable length, unstrained hanger lengths, and pre-offsets for tower saddles and splay saddles) are the core considerations in the design and construction control of a suspension bridge. For the purpose of accurate calculations, it is necessary to take into account the effects of cable strands over the anchor spans, arc-shaped saddle top, and tower top pre-uplift. In this paper, a method for calculating the cable configuration under final dead load over a main span, two side spans, and two anchor spans, coordinates of tangent points, and unstrained cable length are firstly developed using conditions for mechanical equilibrium and geometric relationships. Hanger tensile forces and unstrained hanger lengths are calculated by iteratively solving the equations governing hanger tensile forces and the cable configuration, which gives careful consideration to the effect of hanger weight. Next, equations for calculating the cable configuration in the unloaded state and pre-offsets of saddles are derived from the cable configuration under final dead load and the conditions for unstrained cable length to be conserved. The equations for the main span, two side spans and two anchor spans are then solved simultaneously. In the proposed methods, coupled nonlinear equations are solved by turning them into an unconstrained optimization problem, making the procedure simplified. The feasibility and validity of the proposed methods are demonstrated through a numerical example.

A Simplified Analysis Method for Determining an Optimized Initial Shape of Cable-Stayed Bridges (사장교의 최적 초기형상 및 무응력길이 결정을 위한 간략해석법)

  • Jung, Myung Rag;Park, Se Woong;Min, Dong Ju;Kim, Moon Young
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.6
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    • pp.947-954
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    • 2016
  • A simplified analysis method is first proposed in order to determine an optimized initial shape of cable-stayed bridges including all unstrained element lengths without using complicated nonlinear FE analysis. The unstrained-length based FE method is then presented using the unstrained lengths by the simplified analysis. To demonstrate validity and accuracy of the proposed method, Incheon bridge model having the fabrication camber is constructed and initial shaping analysis is performed using the presented method and commercial finite element analysis program, MIDAS. Resultantly it is shown that the initial solutions by the proposed algorithm are well optimized and in good agreement with those by MIDAS except for axial displacements of the main member.

An Improved Initial Force Method for Determining the Initial Configuration of Suspension Bridges (현수교 시스템의 초기형상 결정을 위한 개선된 초기부재력법)

  • Kim, Min;Kim, Ho-Kyung;Kim, Moon-Young
    • Journal of Korean Society of Steel Construction
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    • v.23 no.2
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    • pp.237-247
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    • 2011
  • This paper presents an improved initial force method for determining the initial shape of suspension bridges. After determining the initial shape factors through the force equilibrium conditions of each hanging point, the initial force method was applied with the computed values, each node's coordinates, and unstrained lengths of the cable element as inputs. The unstrained length of each cable element was regarded as a fixed value in each iteration step, unlike in the typical initial force method. This method can be applied to 2D and 3D suspension bridge models. The validity of the present method was demonstrated by comparing the results of the numerical examples.

Microscopic Analysis of Early Age Cement Paste Axially Compressed 20% (20% 축압축 시킨 초기재령 시멘트 페이스트 미세 분석)

  • 김성훈;김동완;양종석;김장호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.189-194
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    • 2002
  • Many researches in the past have shown that a majority initial cracking in concrete are caused during early age period. Therefore, the close examination of early age concrete behavior under various stress conditions is necessary to fully understand the cracking mechanism of concrete. In this study early age cement paste specimen is axially strained up to 20% of its original length by laterally reinforcing it. This type of test is called "Tube Squash Test" and has been previously used to apply up to 50% axial strain on concrete. Microscopic analyses (XRD, FESEM, EDS and DSE/TG) are performed on 20% axially strained early age cement paste specimen. The analysis results show that the microscopic structures and material characteristics of 20% axially strained cement paste remained same as the unstrained cement paste.

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Practical Determination Method of Initial Cable Forces in Cable-Stayed Bridges (사장교 시스템의 실용적인 초기형상 결정법)

  • Song, Yo-Han;Kim, Moon-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.1
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    • pp.87-95
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    • 2011
  • A rational method for determination of initial cable forces in cable-stayed bridges without complicated nonlinear analysis is presented. Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and vending moments of the deck and pylon. A presented method utilizing the idea of force equilibrium organizes initial shape analysis for each types of cable-stayed bridges. The results of that analysis were compared to several existing methods for 2D numerical examples. And for 3D actual bridges, the improved TCUD method was performed to demonstrate the accuracy of this study.

An Improved Method for Initial Shape Analysis of Cable-Stayed Bridges (사장교의 개선된 초기형상 해석법)

  • Kim, Moon Young;Kyung, Yong Soo;Lee, Jun Sok
    • Journal of Korean Society of Steel Construction
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    • v.15 no.2
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    • pp.175-185
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    • 2003
  • The extended tangent stiffness matrices and force-deformation relations of the elastic catenary element were initially derived through the addition of the unstrained length of cables to unknown nodal displacements. A beam-column element was then introduced to model the deck and pylon of cable-stayed bridges. The conventional geometric nonlinear analysis, initial force method, and TCUD method were summarized, with an effective method combining two methods presented to determine the initial shapes of cable-stayed bridges with dead loads. In this combined method, TCUD method was applied to eliminate vertical and horizontal displacements at cable-supported points of decks and on top of pylons, respectively. The initial force method was also adopted to eliminate horizontal and vertical displacements of decks and pylons, Finally, the accuracy and validity of the proposed combined method were demonstrated through numerical examples.

An Improved Method for Initial Shape Analysis of Subpension Bridges (현수교의 개선된 초기형상 해석법)

  • Kim, Moon Young;Kyung, Yong Soo;Lee, Jun Sok
    • Journal of Korean Society of Steel Construction
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    • v.15 no.2
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    • pp.219-229
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    • 2003
  • The extended tangent stiffness matrices and force-deformation relations of the elastic catenary element were initially derived through the addition of the unstrained length of cables to unknown nodal 'displacements. A beam-column element was then introduced to model the deck and pylon of cable-stayed bridges. The conventional geometric nonlinear analysis, initial force method, and TCUD method were summarized, with an effective method combining two methods presented to determine the initial shapes of cable-stayed bridges with dead loads. In this combined method, TCUD method was applied to eliminate vertical and horizontal displacements at cable-supported points of decks and on top of pylons, respectively. The initial force method was also adopted to eliminate horizontal and vertical displacements of decks and pylons. Finally, the accuracy and validity of the proposed combined method were demonstrated through numerical examples.

Comparison Study of An Improved Initial Force and TCUD Method for Initial Shape Analysis of Cable-Stayed Bridges (사장교의 초기형상해석을 위한 개선된 초기부재력법 및 TCUD법의 비교연구)

  • Kim, Dong-Yeong;Jo, Kyeong-Sik;Kim, Moon-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.1
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    • pp.101-108
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    • 2012
  • Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and bending moments of the deck and pylon. Comparison study of an improved initial force method and TCUD method for determination of initial cable forces in cable-stayed bridges is presented in this paper. For this purpose, an elastic catenary cable element and a nonlinear frame element are firstly described. And concepts and algorithm of two analysis methods are then presented. Finally to demonstrate the validity and the accuracy of two methods, numerical examples for initial state problems of cable-stayed bridges are given and compared based on these methods.