• Title/Summary/Keyword: hanger tension

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Bayesian estimation of tension in bridge hangers using modal frequency measurements

  • Papadimitriou, Costas;Giakoumi, Konstantina;Argyris, Costas;Spyrou, Leonidas A.;Panetsos, Panagiotis
    • Structural Monitoring and Maintenance
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    • v.3 no.4
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    • pp.349-375
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    • 2016
  • The tension of an arch bridge hanger is estimated using a number of experimentally identified modal frequencies. The hanger is connected through metallic plates to the bridge deck and arch. Two different categories of model classes are considered to simulate the vibrations of the hanger: an analytical model based on the Euler-Bernoulli beam theory, and a high-fidelity finite element (FE) model. A Bayesian parameter estimation and model selection method is used to discriminate between models, select the best model, and estimate the hanger tension and its uncertainty. It is demonstrated that the end plate connections and boundary conditions of the hanger due to the flexibility of the deck/arch significantly affect the estimate of the axial load and its uncertainty. A fixed-end high fidelity FE model of the hanger underestimates the hanger tension by more than 20 compared to a baseline FE model with flexible supports. Simplified beam models can give fairly accurate results, close to the ones obtained from the high fidelity FE model with flexible support conditions, provided that the concept of equivalent length is introduced and/or end rotational springs are included to simulate the flexibility of the hanger ends. The effect of the number of experimentally identified modal frequencies on the estimates of the hanger tension and its uncertainty is investigated.

An Evaluation for Structural Performance of Suspension Bridge by using the Natural Frequency of Hanger Member (행거의 고유진동수를 이용한 현수교의 구조적 성능 평가)

  • Wu, Sang Ik;Kim, Kyoung Nam;Lee, Seong Haeng;Jung, Kyoung Sup
    • Journal of Korean Society of Steel Construction
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    • v.16 no.2 s.69
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    • pp.285-293
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    • 2004
  • As a special infrastructure, it is important that the suspension bridges which were designed by using the cable are carefully maintained and safely inspected after their construction, more than what is done in other cases of bridge structures. However, the structural analysis for their design and maintenance has considered only the simplified geometric shape of the structure. Particularly, it is not easy to make the modeling analyze the bridge structure including detailed steel deck plates. In this paper, we evaluated the structural behaviors and performances of the completed earth-anchored suspension bridge that was in a completed state through both the tension of hanger member and their computational analysis. We considered the frame system and the detailed steel deck plates that were especially added into the modeling to take more precision analysis about it. We also applied hanger tensions converted by the natural frequency and the natural frequency of the bridge when in normal vibration. Results of the vehicle loading test were used in the analysis. We compared the results by using our modeling with the result of the loading test and the hanger tension. Our prediction on the behavior of the structure emulates the behavior of the real structure. In applying the data measured by the typhoon "Maemi" which arrived in-land last year, we confirmed our analysis model for the possibility of applying effectively into the preliminary design and maintenance plan.

Hanger Tension Variation of Self-Anchored Suspension Bridge in Construction (시공중 자정식 현수교의 행거 장력변화)

  • Kim, Ho Kyung;Suh, Jeong In
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.6
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    • pp.1309-1317
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    • 1994
  • Because the stiffening girders are constructed after the installation of hangers for typical suspension bridge, no additional tensioning to hangers in construction is necessary for this bridge type in which main cable is earth-anchored. However, for self-anchored suspension bridge, hangers are installed after temporarily supporting stiffening girders constructed in previous stage. Therefore, initial tension is required on installing hangers. Tension of hangers varies as the construction proceeds. Hence, it is necessary to determine the most efficient method of installing hangers among several methods. This study presents finite element procedures and the algorithms of construction stage analysis to simulate construction processes. Geometric nonlinear analysis scheme is also included. The most effective method regarding the installation of hangers is presented through the examples of actual bridge model.

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Estimating Tensile Force of Hangers in Suspension Bridges Using Frequency Based SI Technique : III. Experimental Verification (진동기반의 SI 기법을 이용한 현수교 행어의 장력 추정 : III. 실험적 검증)

  • Jang, Han Teak;Kim, Byeong Hwa;Park, Taehyo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.2A
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    • pp.215-222
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    • 2008
  • This paper introduces an experimental verification of a tension estimation method based on system identification approach for a double hanger system on a suspension bridge. A laboratory model of such double hanger system has been made for this study. Total nine cases of the vibration tests have been conducted with respect to three levels of applied tension and three cases of the location of clamp. For a set of the collected acceleration response data, modal analysis has been followed in order to extract the natural frequencies and mode shapes of the selected cable systems. For the extracted modal parameters, the existing tension estimation methods based on the string theory and axially loaded beam theory have been firstly applied to estimate the tensile force on the double hanger cable system. Next, the tensile force on cables has been estimated by the system identification approach. It is seen that the errors in the tension estimation using the frequency-based system identification technique are about 3% for all cases while the estimation error using the existing method is up to 53.1%.

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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.