| With the rapid development of high-speed railways,attention to the research of high-speed railways been massively increasing as safety evaluation and health monitoring of high-speed railway bridges is a very important research topic.Train driving at high-speed will have a dynamic impact on the bridge,thus affecting the working state and the life span of the bridge.At the same time,the vibration of the bridge will affect the comfort and safety of the train during operation.With the continuous development of the high-speed railway system,under certain complicated terrain conditions,the construction of high-speed railway bridges with high piers has become inevitable.This has also brought many problems to the construction and health monitoring of bridges.Under the heavy payloads with added high-speed,the bridges are subjected to large dynamic effects.Therefore,there are increased demands on advancing railway bridge structures.Along multiple parameters,the speed of trains is a very important influencing factor for the dynamic responses of the bridge.The dynamic responses increase with increasing speed.In addition,the bridge structure may be damaged during service and operation process,which will directly affect the service life of the bridge and the safety and comfort of the train.The research on dynamic analysis and health monitoring system on high-speed railway bridges with high piers is an important means to identify bridge structural damage as early as possible.Through the early diagnosis about the bridge structure health state,a timely maintenance plan is proposed to ensure the safety of the high-speed railway bridge structure and also extend the service life of the bridge structure.Therefore,the research about the dynamic behavior of high-speed railway bridge with high piers under the effect of high-speed train at different speeds andthe optimization placement of the bridge health monitoring system during the operation process have a very important significance.This thesis analyzes the bridge dynamic response under train speed under load at multiple speeds as 120 km/h,180 km/h,240 km/h,300 km/h.Based on the time history analysis method,Midas civil finite element software is used to model the bridge with high piers structure and perform dynamic analysis of the bridge structure.According to the bridge structure dynamic analysis results,based on the principle of economic efficiency and simplicity,the health monitoring system on high-speed railway bridges with high piers has been designed.Its optimization mainly focused on number and position for vertical acceleration sensor and vertical strain sensor.Through the above studies,the main conclusions obtained include:(1)The results of bridge structure dynamic time history analysis are much bigger than the static analysis.When the train crosses the bridge at 120 km/h,the vertical displacement of bridge mid-main span dynamic time history result is 1.4 mm,and the static result is 1.29 mm.(2)The speed of the train is a very important parameter that affects the dynamic response of the bridge structure.In general,the dynamic response increases as the speed increases.When the speed of the train was increased from 120 km/h to 300 km/h,the vertical displacement of bridge mid-main span increased from 1.4 mm to 4.7 mm.In the range of speeds of the train considered in this thesis,there is no resonance phenomenon.(3)With the health monitoring system on high-speed railway bridge with high piers,optimal sensor placement proceeds designs.Finally,two placement plans of the vertical acceleration sensor and the strain sensor are proposed.For each placement plan about twenty sensors are placed,which are mainly distributed in five areas: the side span middle area,the main span quarter area,the main span middle area,the pier top and the pier bottom.The results show that the proposed placements could completely reflect the vertical characteristics of the bridge structure and ensure economic efficiency. |
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