• Title/Summary/Keyword: 폐합해석

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Closing Analysis of Symmetric Steel Cable-stayed Bridges and Estimation of Construction Error (대칭형 강 사장교의 폐합해석과 시공오차의 예측)

  • Lee, Min Kwon;Lee, Hae Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.1A
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    • pp.55-65
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    • 2006
  • This paper presents the closing analysis of a symmetric steel cable-stayed bridge erected by a free cantilever method. Two independent structural systems are formed before the closing procedure of a bridge is performed, and thus the compatibility conditions for vertical displacement and rotational angle are not satisfied at the closing section without the application of proper sectional forces. Since, however, it is usually impossible to apply sectional forces at the closing section, the compatibility conditions should be satisfied by proper external forces that can be actually applicable to a bridge. Unstrained lengths of selected cables and the pull-up force of a derrick crane are adjusted to satisfy nonlinear compatibility conditions, which are solved iteratively by the Newton-Raphson method. Cable members are modeled by the elastic catenary cable elements, and towers and main girders are discretized by linear 3-D frame elements. The sensitivities of displacement with respect to the unstrained lengths of selected cables and the pull-up force of the derrick crane are evaluated by the direct differentiation of the equilibrium equation. A Monte-Carlo simulation approach is proposed to estimate expected construction errors for a given confidence level. The proposed method is applied to the second Jindo Grand Bridge to demonstrate its validity and effectiveness.

Closing Step Analysis in Cable-Stayed Bridges to Produce Initial Equilibrium Condition (초기평형상태 구현을 위한 사장교의 폐합단계 해석)

  • Park, Yong Myung;Yun, Jae Sun;Cho, Hyun Jun;Park, Chung Gon
    • Journal of Korean Society of Steel Construction
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    • v.19 no.2
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    • pp.191-199
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    • 2007
  • This paper presents a closing method for a cable-stayed bridge erected by the free cantilever method to produce the initial equilibrium configuration at the final construction stage. To realize the initial equilibrium condition in cable-stayed bridge by the cantilever method, compatibility conditions for vertical displacements, rotational angles, and axial displacements at the closing section of both side girders should be satisfied. In this paper, it was shown that it can be accomplished by using some applicable loads during construction such as the pull-up force of the derrick crane, some cable tension forces, and jacking force at the pylon. The proposed method was applied to a construction stage analysis of a sample bridge to demonstrate its validity, and it was acknowledged that the tower was considerably affected by the compatibility condition for axial displacement in the closing step.

A Study on the Closure Ratio for Tunnel Face Stabilization during Tunnel Excavation in Sand Soil (사질토지반에서 터널굴착시 막장안정을 위한 폐합비에 관한 연구)

  • Kim, Sang-Hwan;Kim, Ji-Tae;Lim, Chae-Ho;Lee, In-Keun
    • Journal of the Korean Geotechnical Society
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    • v.28 no.4
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    • pp.79-89
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    • 2012
  • This paper presents experimental and numerical studies on the closure ratio of tunnel face to reduce pressure and displacement occurring at tunnel face during tunnel excavation. In experimental study, model tests are carried out according to the closure ratio of tunnel face and tunnel depth. Model test results are analyzed and interpreted by numerical calculation in order to verify results obtained from experimental and numerical studies. It is clearly found that tunnel face stability increases with the increase of the closure ratio of tunnel face. The results also show that tunnel face is stable when the closure ratio of tunnel face is larger than 80%. This research will be very useful to develop the economical tunnel face closing system.

A study on stresses and displacements of the ground according to the closure ratio of tunnel face during tunnel excavation (터널 막장폐합비에 따른 지반 응력 및 침하량에 대한 연구)

  • Kim, Sang-Hwan;Min, Byeong-Heon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.5
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    • pp.369-378
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    • 2010
  • This paper presents a new approach of closing the tunnel face with sprayed concrete to reduce the stress at the tunnel face and displacement occurring at the ground surface during tunnel excavation. In order to carry out this research, the experimental and numerical studies are performed. In the experimental study, the model tests are carried out according to the closure ratio of tunnel face, tunnel depth and tunnel excavation length. The model test results are analyzed and interpreted by numerical calculation in order to verify both results obtained from experimental and numerical studies. It is clearly found that the tunnel face stability is decreased in decreasing the closure ratio of tunnel face. The results also show that the tunnel face is stable when the closure ratio of tunnel face is larger than 80%. This research will be very useful to develop the economical tunnel face closing system.

New Key-Segment Closing Method Using Thermal Effect for Partially Earth-Anchored Cable-Stayed Bridges (온도 효과를 이용한 일부 타정식 사장교의 키-세그먼트 폐합법)

  • Won, Jeong Hun;Yoon, Ji Hyun;Cho, Kwang Il;Kim, Sang Hyo
    • Journal of Korean Society of Steel Construction
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    • v.20 no.1
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    • pp.121-129
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    • 2008
  • study proposes a new key-segment closing method using thermal effect as a substitute to the process of set-back and reset-back for the FCM construction of a partially earth-anchored cable-stayed bridge. The proposed method is to artificially heat up the inside of girders located in the main span before closing the key-segment in a cantilever state. Then, the heat is removed after finishing the closure in a continuous bridge state. Using the changes in boundary conditions and structural systems, the proposed method can generate new member forces that reflect the advantage of the partially earth-anchored cable system. From the construction sequence analysis, it is found that the proposed method increases the efficiency of a partially earth-anchored cable-stayed bridge by reducing the compressive axial forces on the girders.

Stability Analysis of Steel Cable-stayed Bridges under Construction Stage (폐합 전 강사장교의 안정성 해석)

  • Kim, Seung-Jun;Shim, Kyung-Suk;Won, Deok-Hee;Cho, Sun-Kyu;Kang, Young-Jong
    • Journal of Korean Society of Steel Construction
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    • v.23 no.1
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    • pp.99-111
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    • 2011
  • This paper presents an investigation of the structural stability of cable-stayed bridges in the construction stage, using geometric nonlinear finite-element analysis and considering various geometric nonlinearities, such as the sag effect of the cables, the P-${\Delta}$ effects of the girder and mast, and the large displacement effect. Initial shape analysis and construction-stage analysis were performed to determine the equilibrium of the structure in the construction stage. After that, geometric nonlinear analysis was performed to study structural stability. In this study, the weight of the derrick crane and the key segment were considered the main external loads, which were applied to the tip of the center span. The cable arrangement type and the stiffness ratios of the girder and mast were considered the main parameters of the analytic research. Based on the results of the analysis, the change in the buckling mode and critical load factors with respect to the cable arrangement type and the stiffness ratios of the girder and mast was investigated. The buckling modes of the steel cable-stayed bridges in the construction stage were classified, and the ranges of the stiffness ratios of the girder and mast, which show these classified buckling modes, were suggested.

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 Study for Ultimate Behavior of Steel Cable-stayed Bridges under Construction Stage (시공중 강사장교의 극한거동에 대한 해석적 연구)

  • Lee, Joo-Tak;Kim, Seung-Jun;Kim, Jong-Min;Choi, Jun-Ho;Kang, Young-Jong
    • Journal of Korean Society of Steel Construction
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    • v.23 no.6
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    • pp.691-704
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    • 2011
  • This paper presents an investigation on the ultimate behavior of steel cable-stayed bridges in the construction stage, considering various geometric nonlinearities and material nonlinearities. To numerically determine the state of cable-stayed bridges in the construction stage, initial shape analysis and construction stage analysis via backward process analysis were done sequentially. Then nonlinear analysis of the state under the construction load condition, considering the weight of the derrick crane and the key segment of the girder loaded onto the tip of the center span, was performed to investigate the ultimate behavior of the structure. The effects of the girder-mast stiffness ratio, the cable-arrangement types, and the area of the stay cables on the ultimate behavior were also extensively investigated. Moreover, the results of the ultimate analysis, considering both geometric nonlinearities and material nonlinearities, were compared with the results of the geometric nonlinear analysis, for a more meaningful investigation of the ultimate behavior of steel cable-stayed bridges in the construction stage.

A Study on Deformation Analysis of the Earth Retaining Wall (흙막이벽체의 변형해석에 관한 연구)

  • Lee, Song;Kim, Seong-Koo
    • Journal of the Korean Geotechnical Society
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    • v.24 no.2
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    • pp.27-36
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    • 2008
  • This paper analyzed the effects related to the difference of the geometrical shape of the ground excavation by comparing the displacements of the earth retaining wall of the strut resulting from the change of the excavation breadth B and the excavation length L, adopting the three dimensional FDM analysis. It appeared that the displacement of the earth retaining wall of the strut increases in accordance with the increase of L/B and it decreases as it becomes nearer from the center to the comer where the temporary structural system forms, and the wale member is closured because of the effects of the confining effect by the closure of the earth retaining wall and the wale member. This paper proposed a formula in which the results of three dimensional FDM analysis which considers the shape of the excavation plane can be obtained from those of two dimentional FDM analysis which does not consider the shape of the excavation plane. And the results of the formula were compared with those of the site instrumentation analysis.

Applications of Graph Theory for the Pipe Network Analysis (상수관망해석을 위한 도학의 적용)

  • Park, Jae-Hong;Han, Geon-Yeon
    • Journal of Korea Water Resources Association
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    • v.31 no.4
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    • pp.439-448
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    • 1998
  • There are many methods to calculate steady-state flowrate in a large water distribution system. Linear method which analyzes continuity equations and energy equations simultaneously is most widely used. Though it is theoretically simple, when it is applied to a practical water distribution system, it produces a very sparse coefficient matrix and most of its diagonal elements are to be zero. This sparsity characteristic of coefficient matrix makes it difficult to analyze pipe flow using the linear method. In this study, a graph theory is introduced to water distribution system analysis in order to prevent from producing ill-conditioned coefficient matrix and the technique is developed to produce positive-definite matrix. To test applicability of developed method, this method is applied to 22 pipes and 142 pipes system located nearby Taegu city. The results obtained from these applications show that the method can calculate flowrate effectively without failure in converage. Thus it is expected that the method can analyze steady state flowrate and pressure in pipe network systems efficiently. Keywords : pipe flow analysis, graph theory, linear method.

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