• Title, Summary, Keyword: cable stiffness

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Seismic analysis of half-through steel truss arch bridge considering superstructure

  • Li, Ruiqi;Yuan, Xinzhe;Yuan, Wancheng;Dang, Xinzhi;Shen, Guoyu
    • Structural Engineering and Mechanics
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    • v.59 no.3
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    • pp.387-401
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    • 2016
  • This paper takes a half-through steel truss arch bridge as an example. A seismic analysis is conducted with nonlinear finite element method. Contrast models are established to discuss the effect of simplified method for main girder on the accuracy of the result. The influence of seismic wave direction and wave-passage on seismic behaviors are analysed as well as the superstructure and arch ring interaction which is mostly related with the supported bearings and wind resistant springs. In the end, the application of cable-sliding aseismic devices is discussed to put forward a layout principle. The main conclusions include: (1) The seismic response isn't too distinctive with the simplified method of main girder. Generally speaking, the grillage method is recommended. (2) Under seismic input from different directions, arch foot is usually the mostly dangerous section. (3) Vertical wave input and horizontal wave-passage greatly influence the seismic responses of arch ring, significantly increasing that of midspan. (4) The superstructure interaction has an obvious impact on the seismic performance. Half-through arch bridges with long spandrel columns fixed has a less response than those with short ones fixed. And a large stiffness of wind resistant spring makes the the seismic responses of arch ring larger. (5) A good isolation effectiveness for half-through arch bridge can be achieved by a reasonable arrangement of CSFABs.

Dispersion Characteristics of Wave Forces on Interlocking Caisson Breakwaters by Cross Cables (크로스 케이블로 결속된 인터로킹 케이슨 방파제의 파력분산특성)

  • Seo, Ji Hye;Yi, Jin Hak;Park, Woo Sun;Won, Deck Hee
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.27 no.5
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    • pp.315-323
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    • 2015
  • Damage level of coastal structures has been scaled up according to increase of wave height and duration of the storm due to the abnormal global climate change. So, the design criteria for new breakwaters is being intensified and structural strengthening is also conducted for the existing breakwaters. Recently, interlocking concept has been much attention to enhance the structural stability of the conventional caisson structure designed individually to resist waves. The interlocking caisson breakwater may be survival even if unusual high wave occurs because the maximum wave force may be reduced by phase lags among the wave forces acting on each caisson. In this study, the dispersion characteristics of wave forces using interlocking system that connect the upper part of caisson with cable in the normal direction of breakwater was investigated. A simplified linear model was developed for computational efficiency, in which the foundation and connection cables were modelled as linear springs, and caisson structures were assumed to be rigid. From numerical experiments, it can be found that the higher wave forces are transmitted through the cable as the angle of incident wave is larger, and the larger the stiffness of the interlocking cable makes larger wave dispersion effect.

Behaviour of Truss Bridges by Using the Post-tensioning (후긴장을 이용한 트러스의 성능 향상 평가)

  • Jeung, Bae-Keun;Han, Kyung-Bong;Eom, Jun-Sik;Park, Sun-Kyu
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.7 no.2
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    • pp.247-261
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    • 2003
  • The technique of posttensioning has been used successfully to improve the performance of existing concrete structures. However, very few applications of this technique can be found in steel structures. Posttensioning by means of high strength cable or bar can be used to effectively increase the working load capacity of Truss Bridges. The benefits of posttensioning trusses can be achieved in strengthening of existing structures as well as in the design of new structures. In this paper, the elastic behavior of posttensioned trusses with straight and draped tendon profiles is examined. For the analysis of posttensioned trusses in the elastic range of behavior, two methods are presented, namely, the flexibility method and the mixed-method, i.e., a combination of the stiffness and flexibility methods. Using the presented methods, the effects of design variables such as the tendon profile, truss type, prestress force, and tendon eccentricity on the working load and deflection of trusses are studied. The results show that the allowable load of truss increases proportionally with increase in prestress force and eccentricity. Posttesioning enlarges the elastic range, increases redundancy, and reduces deflection and member stresses. Thus, the remaining life of a truss bridge can be increased relatively inexpensively.

Vertical Seismic Vibration of Suspension Bridges (지진을 받는 현수교의 수직진동)

  • Choi, Jee-Hoon;Lee, Jon-Ja;Kim, Su-Bo;Lee, Yong-Jae
    • Journal of Korean Society of Steel Construction
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    • v.12 no.5
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    • pp.581-593
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    • 2000
  • In this study, vertical dynamic analyses on the suspension bridges under seismic load are developed. Time domain analysis, random vibration analysis, and spectral analysis are formulated theoretically. The random nitration analysis is checked by numerical integration and the mathematical integration with correlation coefficient which include CQC and SRSS method in the conditions of white noise and filtered white noise. Beam, truss and frame elements are used in order to model the suspension bridge. Geometric stiffness due to dead load is considered for cable and tower.

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A Study on the Shape Analysis of Membrane Structures Using Line Elements (선재 요소를 이용한 막 구조물의 형상해석에 관한 연구)

  • Kim, Seung-Deog;Lee, Shin-Woo
    • Journal of the Korean Association for Spatial Structures
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    • v.10 no.2
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    • pp.45-60
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    • 2010
  • Nonlinear problems for membrane structures are very sensitive in convergence procedure in nonlinear iterations. Therefore many researchers have suggested a lot of ideas in published papers. In this study, authors are trying to get easier solution for taking membrane shape by initial stresses from substitution of the membrane to line elements. To obtain nonlinear stiffness, the nonlinear finite element method is used for both membrane and cable elements, and only geometric nonlinear terms are taken for shape analysis. By some examined models, we can find that the substituted models show better results to get, initial shape in which the concentrating phenomenon is removed at edge parts.

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Contact Stress Analysis of Stick Type Ignition Coil Jacket PET (Stick Type Ignition Coil Jacket PET의 접촉응력 해석)

  • Kim Yang-Sul
    • Journal of the Korean Society of Safety
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    • v.20 no.1
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    • pp.1-6
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    • 2005
  • Stick type ignition coil is new development that connect directly with ECU(Electronic control unit), without needing a spark plug cable and distributor. Glass-fiber reinforced ploymeric composites provide the desirable properties of high stiffness and strength as well as low specific weight. Stick type ignition coil jacket is using PBT CF30 resin. PBT CF30 resin is a kind of electric insulation which is a superior engineering plastic that is used to prevent the leakage of the electrical current. If PET receive a mistake of design or excessive force when HV terminal oppress on jacket, it can happen to crack. Local stress concentrations occurring on the contact surface, the contact phenomenon becomes a direct cause to the wear and failure of mechanical structures. When it is cracked, it can allow a leakage of the electrical current. So, in this study, we analyze the contact stress to PBT jacket using ANSYS program, when HV terminal oppress on jacket. We suppose PBT to be Jacket and we analyzed contact stress that happens in PET like PBT analysis method. We compared the use of PBT and PET.

Analytical and numerical algorithm for exploring dynamic response of non-classically damped hybrid structures

  • Raheem, Shehata E. Abdel
    • Coupled systems mechanics
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    • v.3 no.2
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    • pp.171-193
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    • 2014
  • The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of hybrid structure with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. A numerical algorithm capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to explore the dynamic response of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified model of 2 coupled lumped masses to investigate the effects of subsystems different damping, mass ratio, frequency ratio on dynamic characteristics and equivalent modal damping; the second approach employs a detailed numerical step-by step integration procedure.

Mechanical performance and design optimization of rib-stiffened super-wide bridge deck with twin box girders in concrete

  • Wen, Xiong;Ye, Jianshu;Gai, Xuemei;Cai, C.S.
    • Structural Engineering and Mechanics
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    • v.48 no.3
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    • pp.395-414
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    • 2013
  • The present study fundamentally investigated the mechanical performance of the rib-stiffened super-wide bridge deck with twin box girders in concrete, which is a very popular application to efficiently widen the bridges with normal span. The shear lag effects of the specific cross-sections were firstly studied. The spatial stress distribution and local stiffness of the bridge deck with twin box girders were then investigated under several typical wheel load conditions. Meanwhile, a comparative study for the bridge deck with and without stiffening ribs was also carried out during the investigation; thereby, a design optimization for the stiffening ribs was further suggested. Finally, aiming at the preliminary design, an approximate methodology to manually calculate the bending moments of the rib-stiffened bridge deck was analytically proposed for engineers to quickly assess its performance. This rib-stiffened bridge deck with twin box girders can be widely applied for concrete (especially concrete cable-stayed) bridges with normal span, however, requiring a super-wide bridge width due to the traffic flow.

Flutter analysis of long-span bridges using ANSYS

  • Hua, X.G.;Chen, Z.Q.;Ni, Y.Q.;Ko, J.M.
    • Wind and Structures
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    • v.10 no.1
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    • pp.61-82
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    • 2007
  • This paper presents a novel finite element (FE) model for analyzing coupled flutter of long-span bridges using the commercial FE package ANSYS. This model utilizes a specific user-defined element Matrix27 in ANSYS to model the aeroelastic forces acting on the bridge, wherein the stiffness and damping matrices are expressed in terms of the reduced wind velocity and flutter derivatives. Making use of this FE model, damped complex eigenvalue analysis is carried out to determine the complex eigenvalues, of which the real part is the logarithm decay rate and the imaginary part is the damped vibration frequency. The condition for onset of flutter instability becomes that, at a certain wind velocity, the structural system incorporating fictitious Matrix27 elements has a complex eigenvalue with zero or near-zero real part, with the imaginary part of this eigenvalue being the flutter frequency. Case studies are provided to validate the developed procedure as well as to demonstrate the flutter analysis of cable-supported bridges using ANSYS. The proposed method enables the bridge designers and engineering practitioners to analyze flutter instability by using the commercial FE package ANSYS.

Buffeting Response Correction Method based on Dynamic Properties of Existing Cable-Stayed Bridge (공용 사장교의 동적특성을 반영하는 버페팅 응답보정법)

  • Kim, Byeong Cheol;Yhim, Sung Soon
    • Journal of The Korean Society of Civil Engineers
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    • v.33 no.1
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    • pp.71-80
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    • 2013
  • According to design specifications for structural safety, a bridge in initial design step has been modelled to have larger self-weight, external loads and less stiffness than those of real one in service. Thereby measured buffeting responses of existing bridge show different distributions from those of the design model in design step. In order to obtain accurate buffeting responses of the in-site bridge, the analysis model needs to be modified by considering the measured natural frequencies. Until now, a Manual Tuning Method (MTM) has been widely used to obtain the Measurement-based Model(MBM) that has equal natural frequencies to the real bridge. However, since state variables can be selected randomly and its result is not apt to converge exact rapidly, MTM takes a lot of effort and elapsed time. This study presents Buffeting Response Correction Method (BRCM) to obtain more exact buffeting response above MTM. The BRCM is based on the idea the commonly used frequency domain buffeting analysis does not need all structural properties except mode shapes, natural frequencies and damping ratio. BRCM is used to improve each modal buffeting responses of the design model by substituting measured natural frequencies. The measured natural frequencies are determined from acceleration time-history in ordinary vibration of the real bridge. As illustrated examples, simple beam is applied to compare the results of BRCM with those of a assumed MBM by numerical simulation. Buffeting responses of BRCM are shown to be appropriate for those of in-site bridge and the difference is less than 3% between the responses of BRCM and MTM. Therefore, BRCM can calculate easily and conveniently the buffeting responses and improve effectively maintenance and management of in-site bridge than MTM.