Research On Dynamic Performances Of Damaged Rc Railway Simply Supported Beam Bridge Under Alternating Load Of Passenger And Freight Train

The reinforced concrete simply supported beam bridge is widely used in China’s railway bridges.For more than 20 years,the repeated acceleration of passenger and freight trains has increased the cyclic load of the old bridges,resulting in increased damage to the old bridges,which brings hidden dangers to driving safety.According to the survey,more than 600,000 bridges have been built in China,and more than 200,000 are reinforced concrete bridges.The existing passenger and cargo collinear railway has 58,800 old bridges and 273,000 holes,and there are quite a few performances.Damaged concrete girder bridges,so it is very important to study the dynamic characteristics of damaged concrete railway bridges under the action of passenger and freight trains.This paper uses a combination of field testing,model testing and numerical simulation.Firstly,the cross-section measurement,dynamic performance test and forced vibration test were carried out on the NO.40 beam bridge of Xin-Tai railway.By comparing the test results with the specifications,the current service status of the bridge was evaluated,and the subsequent correction and verification models were provided.Secondly,the alternating load fatigue test of the scaled simply supported beam designed with the NO.40 bridge as the prototype was carried out,and the structural dynamic performance was reduced with the structural damage.Thirdly,the passenger train and freight were analyzed.The physical model of the train and the ballasted track realizes the interaction between the components inside the ballast track,the bridge and the ballasted track through the spring-damper unit,and introduces the bridge damage and the track irregularity as an external stimulus into the vehicle-In the rail-to-bridge coupled vibration model;finally,a dynamic coupled finite element model of the passenger-cargo-cable-trackbridge with consideration of the degree of damage of the bridge(0%~50%)and the irregularity of the track is established,and the model is calculated by simulation.The results are compared with the measured results of the NO.40 bridge of Xin-Tai railway,which verifies the correctness of the model.This paper draws the following conclusions:(1)Taking the real engineering of NO.40 Bridge of Xin-Tai railway as the background,by measuring its geometrical dimensions,modal information and bridge acceleration response and mid-span deflection response of train crossing bridge,the analysis results show that: XinTai railway NO.40 Bridge is in At present,there is still a certain safety reserve during normal operation;the test data can be used for subsequent modeling and model verification.(2)Through the fatigue test of RC simply supported beam under the alternation of passenger and cargo trains,the dynamic performance of the test beam under different damage levels is analyzed,and the dynamic performance of RC simply supported beam is improved with the increase of damage degree.Big and lower.(3)Taking the NO.40 bridge of Xin-Tai railway and the DF11 locomotive,YZ25 B type car and C70 gondola running on the prototype,a passenger-cargo train considering the bridge damage on the ANSYS platform Coupling finite element model.Based on the model built,the dynamic response of the vehicle body and the bridge when the train and the freight train cross the bridge are calculated and analyzed,and the comparison between the train and the freight train is verified.The correctness of the model built.(4)Summarize and analyze the safety of six types of bridge beam damage(0%~50%)and three kinds of vehicle models(passenger train,freight train,freightless freight train).Smoothness.The research shows that: based on the current service status of the bridge,when the damage degree exceeds 30%,the passenger and freight trains exceed the safety warning limit;the long-term passenger and freight train can be guaranteed by strictly controlling the train weight and monitoring the damage degree of the bridge.Operational safety and stability.The research results in this paper can provide a scientific basis for the safe service of the existing railway bridges.The innovations of this paper are as follows:(1)A dynamic coupled finite element model of a passenger-cargo train with a damaged orbital bridge is considered.(2)The safety and stability of passenger and freight train crossing bridges under different damage levels of bridges are studied.The safety criterion of passenger and freight trains is proposed.