Monitoring-based evaluation of unsymmetric dynamic response of a suspension bridge due to railway traffic and wind loading

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Monitoring-based evaluation of unsymmetric dynamic response of a suspension bridge due to railway traffic and wind loading

 

Author: Zhang, Chi
Title: Monitoring-based evaluation of unsymmetric dynamic response of a suspension bridge due to railway traffic and wind loading
Degree: M.Sc.
Year: 2014
Subject: Hong Kong Polytechnic University -- Dissertations
Suspension bridges -- Testing
Wind-pressure
Dynamic testing
Department: Faculty of Construction and Environment
Pages: x, 79 leaves : illustrations (some color) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2759229
URI: http://theses.lib.polyu.edu.hk/handle/200/7616
Abstract: A good understanding of normal modal variability of civil structures due to varying environmental conditions such as railway loads and wind is important for reliable performance of vibration-based damage detection methods. It is well known that long-span cable-supported bridges are flexible structures vulnerable to unsymmetric loadings such as railway traffic and strong wind. The unsymmetric dynamic response of long-span cable-supported bridges under running trains and/or strong winds may deform the railway track laid on the bridge deck and affect the running safety of trains and the comfort of passengers, and even make the bridge collapse. Therefore, it is eager to figure out the unsymmetric dynamic response of long-span cable-supported bridges under running trains and/or strong winds. Located at latitude N22.2° and longitude E114.1 ° which is one of the most active III typhoon prone regions in the world, Tsing Ma Suspension Bridge has a total span of 2,132 m and carries a dual three-lane highway on the upper level of the bridge deck and two railway tracks and two protected carriageways on the lower level within the bridge deck. The main span across the Tsing Yi Island and the Ma Wan Island is 1,377 m long, and is currently the world's longest suspension bridge carrying both highway and railway loading. Just because this bridge is located in one of the most active typhoon prone regions in the world, a wind and structural health monitoring system (WASHMS) was installed in the Tsing Ma suspension bridge in Hong Kong in 1997, the SHM system deployed on the Tsing Ma Bridge has operated continuously and steadily for seventeen years, and a wealth of high-quality data about the structural responses, loadings and environmental conditions has been collected. The goal of this dissertation is to make the evaluation of the unsymmetric dynamic response of the Tsing Ma Bridge due to railway traffic and wind loading by using the monitoring data.
Using one-year monitoring data acquired by the WASHMS, the unsymmetric vertical displacement and the rotation of the bridge deck under railway traffic and strong wind are analyzed. The one-year data can be classified into two categories: the data under weak wind and the data under typhoons. The field measurement data recorded by the WASHMS were therefore analyzed and the three particular cases were identified and discussed for each data set: (1) the bridge without any train; (2) the bridge with one train; (3) the bridge with two trains running in opposite directions. The comparison among the three cases has been analyzed in this dissertation. For these three different railway cases, wind conditions, bridge acceleration responses and bridge displacement responses (both vertical and lateral) were analyzed by using the measurement data from anemometers, accelerometers and level sensing systems respectively. The number of trains running on the bridge, train speed, running direction and train location could also be confirmed by analyzing the data from strain gauges. The measurement results clearly demonstrated the dynamic responses of the bridge deck with running trains in the weak wind conditions and during typhoon.

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