| With the development of heavy haul transportation of freight railway in China,the noise pollution caused by large axle load and long marshalling train is becoming more and more serious.The installation of noise barriers has become one of the main measures to reduce the noise pollution in the sensitive area near the railway.However,most of the heavy haul railway bridges upgraded by capacity expansion have been in service for a long time,and the influence of adding noise barriers on the bridge structure has not been considered in the original design.Therefore,this thesis takes a 32 m prestressed concrete simply supported T-beam as the main research object,taking into account the noise reduction and acoustic design requirements of the noise barriers,and carries out the adaptability analysis of the main,the location of the connection between the noise barriers and the bridge and the ballast tank under different load combinations.For the parts that do not meet the requirements of the specification,the methods of deloading noise barriers and strengthening the T-beam flange plate are studied respectively,and a reasonable treatment scheme for installing the noise barriers is proposed.The main work and research contents are as follows:The noise reduction principle,acoustic design principle and structure selection principle of noise barriers are summarized,and the case of installing noise barriers on a heavy haul railway is selected for noise reduction application analysis.The results have shown that the noise barrier’s insertion loss exceeds the required insertion loss for the sensitive area surrounding the investigated target bridge in this thesis.Consequently,the height,thickness,and type of the noise barriers have been chosen as the fundamental input parameters for the noise barriers installation on the target bridge.The overall finite element model of 32 m prestressed concrete T-beam is established.Considering the particularity of curved bridge,the overall adaptability analysis of the main beam before and after the installation of noise barriers is carried out with bending resistance,shear resistance,crack resistance,prestress degree and concrete compressive stress as the main parameters.The results have shown that,when compared with the relevant provisions of the Code for Design of Concrete Structures of Railway Bridge and Culvert(TB 10092-2017),the aforementioned key static analysis indexes have a certain safety margin.Additionally,the installation of the noise barriers has minimal impact on the overall T-beam structure.The theoretical analysis combined with numerical simulation is used to analyze the connection position between the noise barrier and the T-beam and the adaptability of the ballast tank,and the potential weak position of the flange plate and the noise barrier structure is analyzed.The research has shown that,with reference to the relevant design specifications,the ballast tank still retains an ideal safety margin even under the most unfavorable load combination.However,under the influence of certain load combinations,the safety margin of the connection position between the noise barrier and the bridge may become insufficient.The damage order of the T-beam is as follows:embedded chemical anchor,retaining wall,the junction of noise barrier column and horizontal bar,the height of ballast tank,and the root of flange plate.In order to address the issue of T-beam sections that do not meet the requirements for installing noise barriers,a feasibility study was conducted on deloading noise barriers and reinforcement of T-beam ballast walls using high-strength concrete.The research has shown that: 1.The load shedding optimization method was unable to make the T-beam adapt to the installation of noise barriers.2.The proposed method of reinforcing and retrofitting the ballast wall was validated through numerical simulation analysis,enabling the T-beam to accommodate the installed noise barriers.This provides a valuable reference for the retrofitting of similar problems. |
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