• Title, Summary, Keyword: Viaduct

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Structural noise mitigation for viaduct box girder using acoustic modal contribution analysis

  • Liu, Linya;Qin, Jialiang;Zhou, Yun-Lai;Xi, Rui;Peng, Siyuan
    • Structural Engineering and Mechanics
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    • v.72 no.4
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    • pp.421-432
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    • 2019
  • In high-speed railway (HSR) system, the structure-borne noise inside viaduct at low frequency has been extensively investigated for its mitigation as a research hotspot owing to its harm to the nearby residents. This study proposed a novel acoustic optimization method for declining the structure-borne noise in viaduct-like structures by separating the acoustic contribution of each structural component in the measured acoustic field. The structural vibration and related acoustic sourcing, propagation, and radiation characteristics for the viaduct box girder under passing vehicle loading are studied by incorporating Finite Element Method (FEM) with Modal Acoustic Vector (MAV) analysis. Based on the Modal Acoustic Transfer Vector (MATV), the structural vibration mode that contributes maximum to the structure-borne noise shall be hereinafter filtered for the acoustic radiation. With vibration mode shapes, the locations of maximum amplitudes for being ribbed to mitigate the structure-borne noise are then obtained, and the structure-borne noise mitigation performance shall be eventually analyzed regarding to the ribbing conduction. The results demonstrate that the structural vibration and structure-borne noise of the viaduct box girder mainly occupy both in the range within 100 Hz, and the dominant frequency bands both are [31.5, 80] Hz. The peak frequency for the structure-borne noise of the viaduct box girder is mainly caused by $16^{th}$ and $62^{th}$ vibration modes; these two mode shapes mainly reflect the local vibration of the wing plate and top plate. By introducing web plate at the maximum amplitude of main mode shapes that contribute most to the acoustic modal contribution factors, the acoustic pressure peaks at the field-testing points are hereinafter obviously declined, this implies that the structure-borne noise mitigation performance is relatively promising for the viaduct.

Dynamic analysis of metro vehicle traveling on a high-pier viaduct under crosswind in Chongqing

  • Zhang, Yunfei;Li, Jun;Chen, Zhaowei;Xu, Xiangyang
    • Wind and Structures
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    • v.29 no.5
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    • pp.299-312
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    • 2019
  • Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train under crosswind. Compared with the conditions of no-wind, crosswind triggers severer vibration of the dynamic system; compared with the short-pier viaduct, the high-pier viaduct has worse stability under crosswind. For these reasons, the running safety of the metro vehicle traveling on a high-pier viaduct under crosswind is analyzed to ensure the safe operation in metro lines in mountain cities. In this paper, a dynamic model of the metro vehicle-track-bridge system under crosswind is established, in which crosswind loads model considering the condition of wind zone are built. After that, the evaluation indices and the calculation parameters have been selected, moreover, the basic characteristics of the dynamic system with high-pier under crosswind are analyzed. On this basis, the response varies with vehicle speed and wind speed are calculated, then the corresponding safety zone is determined. The results indicate that, crosswind triggers drastic vibration to the metro vehicle and high-pier viaduct, which in turn causes running instability of the vehicle. The corresponding safety zone for metro vehicle traveling on the high-pier is proposed, and the metro traffic on the high-pier bridge under crosswind should not exceed the corresponding limited vehicle speed to ensure the running safety.

A study of CWR on railway viaduct with sharp curves (철도고가교 급곡선부 레일장대화 방안연구)

  • 이상진;김기훈;신순호;이주헌
    • Proceedings of the KSR Conference
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    • pp.415-422
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    • 2000
  • The Seoul Subway Line 4 crossing downtown diagonally constructed in February 1980 and opened on October 11, 1983. The line 4 is thus able to link southern and northern parts of Seoul with the downtown as well as with the Seoul outskirts. More than 810,000 people use it everyday. Line 4 was constructed like Line 1,2,3 with ballast track system causing much maintenance cost gradually and espicially much public discontent due to wheel and rail contact noise by railway viaduct with sharp curves. CWR on railway viaduct with sharp curves, 180m$\leq$R$\leq$300m, hasn't been designed and constructed ever in domestic. Therefore in order to reduce noise and vibration caused by interaction between wheel and rail the possibility and the methods of CWR(Continuous Welded Rail) on railway viaduct with sharp curve less than R300 will lead it to the maintenance free system.

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Study on Enhancing Lightning Protection Scheme of Catenary in Subway Viaduct Section

  • Li, Rui-Fang;Chen, Kui;Chen, Li-Sheng;Cao, Xiao-Bin;Wu, Guang-Ning;Zhang, Xue-Qin
    • Journal of Electrical Engineering and Technology
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    • v.12 no.2
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    • pp.950-958
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    • 2017
  • Viaduct increases the height of subway catenary, namely magnifies lightning attraction scope that lead to higher possibility of suffering lightning stroke. Therefore, it is necessary to analyze performance of lightning striking to catenary of subway in viaduct section and propose an improving lightning protection scheme. In this paper, using ATP-EMTP simulation software to establish an associated model to evaluate lightning withstand level of catenary with existing lightning protection schemes including arrester and grounding point, an improving lightning protection scheme is proposed - every pillar ground earth and arresters are installed with some installing spacing between 200m to 400m based on lightning damage degree and reliability requirements - according to analyzing results: while lightning withstand level is lowest for lightning striking to the neutral pillar, lightning withstand level is greatest for lightning striking to the both-ends pillar that arrester and grounding point are both installed; grounding point could obviously improve lightning withstand level for lightning striking to ground wire while arrester could obviously improve the lightning withstand level for lightning striking to catenary; every pillar ground earth could enhance the lowest lightning withstanding level up to 2.5 times than of that pillar ground earth across every 200m.

The Behaviors of Earthquake Monitoring System for Gyungbu High Speed Railroad on the Odaesan Earthquake (오대산지진 시 경부고속철도 지진감시시스템 거동)

  • Kim, Dae-Sang;Kim, Sung-Il;Choi, Su-Hyun;You, Won-Hee
    • 한국방재학회:학술대회논문집
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    • pp.537-540
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    • 2008
  • This paper reviews the operation standards and manuals of earthquake monitoring system for Gyungbu high speed railroad. The domestic earthquake monitoring system detects the acceleration data at the locations of lower part of pier and deck of viaducts and bridges, not like foreign system to do the surface ground accelerations. For the purpose of evaluating the behaviors of the domestic earthquake monitoring system, measured acceleration data on the Odaesan earthquake at Iwon viaduct were analysed. The values of maximum acceleration level of the viaduct were increased from 0.0089g(EW component) of the lower part of pier to 0.014g(EW component) on the deck of the viaduct. And also the predominant periods and frequencies were analysed by the frequency domain analysis.

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The Design of Viaduct Girder of Incheon Bridge (인천대교 고가교 상부거더 설계)

  • Kang, Dang-Ok;Cho, Ik-Sun;Kim, Yeong-Seon;Yang, Jang-Ho;Shin, Hyun-Yang;Yoon, Man-Geun
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.294-297
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    • 2006
  • The purpose of this study is to introduce design practice for prestressed concrete box girder with AASHTO LRFD Design Specification. Distinctive features of viaduct girder of Incheon Bridge are pre-tensioned transverse tendon, 3-dim. transverse analysis, enlarged opening in diaphragm and so on.

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An Experimental Study of Seismic Retrofit on the Viaduct Bridge of Rail Transit (철도 고가교 기둥의 내진성능에 관한 실험적 연구)

  • Kim, Jinho;Shin, Hongyoung;Park, Yeonjun;Hur, Jinho
    • Journal of the Korean Society for Railway
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    • v.15 no.6
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    • pp.616-622
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    • 2012
  • Earthquake damage of viaduct bridge of railroad may give rise to social loss due to transport restrictions greater than cost of structural recovery. Therefore, viaduct bridge of railroad should have ensure adequate seismic performance. But, results of seismic performance evaluation, many of seismic retrofit was required. In this study, five scale models of columns were made and four of them were reinforced by HT-A(HyperTex & perforate Aluminum) which is improved than existing method. Testing the columns by constant axial load and cyclic lateral displacements, seismic performance of columns has been verified from the result of evaluating the stiffness, ductility and energy dissipation capacity.

Estimation of modal correlation coefficients from background and resonant responses

  • Denoel, V.
    • Structural Engineering and Mechanics
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    • v.32 no.6
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    • pp.725-740
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    • 2009
  • A new simple relation for the estimation of modal correlation coefficients is presented. It is obtained from the decomposition of covariances of modal responses into background and resonant contributions, as it is commonly done for the variances. Thanks to appropriate assumptions, the modal correlation coefficients are estimated as weighted sums of two limit values, corresponding to the background and resonant responses respectively. The weighting coefficients are expressed as functions of the background-to-resonant ratios, which makes the proposed formulation convenient and easily accessible. The simplicity of the mathematical formulation facilitates the physical interpretation. It is for example proved that modal correlation coefficients can be non negligable even in case of well separated natural frequencies, which is sometimes unclear in the litterature. The new relation is mainly efficient in case of large finite element models. It is applied and validated on a finite element buffeting analysis of the Viaduct of Millau, the highest bridge deck ever built so far.

Assessment of traffic-induced low frequency sound radiated from a viaduct by field experiment

  • Kawatani, M.;Kim, C.W.;Nishitani, K.
    • Interaction and multiscale mechanics
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    • v.3 no.4
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    • pp.373-387
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    • 2010
  • This study is intended to assess low frequency sound radiated from a viaduct under normal traffic. The bridge comprises steel box girders and wide cantilever decks on which vehicles pass. The low frequency sound and the acceleration response of the bridge under normal traffic are measured to investigate how bridge vibrations affect the low frequency sound observed near the bridge. Observations demonstrate that strong relationships exist between frequency characteristic of bridge's acceleration response and the sound pressure level of low frequency sound. A noteworthy point is that the dynamic feature of the sound pressure level is mostly affected by dynamic feature of the span locating near the observation point.

Viaduct seismic response under spatial variable ground motion considering site conditions

  • Derbal, Rachid;Benmansour, Nassima;Djafour, Mustapha;Matallah, Mohammed;Ivorra, Salvador
    • Earthquakes and Structures
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    • v.17 no.6
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    • pp.557-566
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    • 2019
  • The evaluation of the seismic hazard for a given site is to estimate the seismic ground motion at the surface. This is the result of the combination of the action of the seismic source, which generates seismic waves, the propagation of these waves between the source and the site, and site local conditions. The aim of this work is to evaluate the sensitivity of dynamic response of extended structures to spatial variable ground motions (SVGM). All factors of spatial variability of ground motion are considered, especially local site effect. In this paper, a method is presented to simulate spatially varying earthquake ground motions. The scheme for generating spatially varying ground motions is established for spatial locations on the ground surface with varying site conditions. In this proposed method, two steps are necessary. Firstly, the base rock motions are assumed to have the same intensity and are modelled with a filtered Tajimi-Kanai power spectral density function. An empirical coherency loss model is used to define spatial variable seismic ground motions at the base rock. In the second step, power spectral density function of ground motion on surface is derived by considering site amplification effect based on the one dimensional seismic wave propagation theory. Several dynamics analysis of a curved viaduct to various cases of spatially varying seismic ground motions are performed. For comparison, responses to uniform ground motion, to spatial ground motions without considering local site effect, to spatial ground motions with considering coherency loss, phase delay and local site effects are also calculated. The results showed that the generated seismic signals are strongly conditioned by the local site effect. In the same sense, the dynamic response of the viaduct is very sensitive of the variation of local geological conditions of the site. The effect of neglecting local site effect in dynamic analysis gives rise to a significant underestimation of the seismic demand of the structure.