Analysis Of The Mechanical Properties And Seismic Response Of A Steel-Concrete Composite Beam Bridge

Steel-concrete composite beam bridge is widely used in China.It holds the advantages of large span capacity and good seismic performance.Besides,its main beam is light in weight,so it has broad prospects for development.China has a wide range of earthquakes.The earthquakes in China are large in magnitude and high in frequency.Once bridges are severely damaged in earthquakes,the traffic in the earthquake-stricken areas will be cut off,which interferes the normal earthquake relief work,causing immeasurable impacts on national property and people’s lives.Therefore,it is of great significance to study the seismic performance of bridges.Currently,the research on the seismic performance of beam bridges is mostly directed at concrete bridges,while the research on the seismic performance of steel-concrete composite beam bridges is less.So it is necessary to analyze the seismic response of steel-concrete composite beam bridges.Based on the above situation,a steel box concrete composite beam bridge is taken as the research object in this thesis.Through static load tests,the strain and deflection of the main beam under load are measured,and the finite element model is established for comparison and verification.It is found that the finite element model data are basically consistent with the experimental data,which indicates the correctness of the parameters of the main beam model.Then the dynamic finite element model of the bridge is established by using the main beam parameters of the above model,and the seismic performance of the bridge is studied.The main contents of this thesis are as follows.(1)Static load tests of a steel box concrete composite bridge are carried out.The strain and deflection of the main beam section at the top and mid-span position of the fixed piers are measured,and the finite element model is established for comparison and verification.The result shows that the finite element model data are in good agreement with the experimental data,indicating the correctness of the selection of model parameters.Therefore,the main beam parameters are used in the subsequent seismic research of the bridge,which paves the way for the study of seismic performance of the bridge.(2)The dynamic finite element model of the steel box concrete composite beam bridge is established,the dynamic characteristics of the bridge are analyzed,and the response spectrum of the bridge is analyzed.Besides,the longitudinal and transverse seismic responses of the bridge under the acceleration response spectrum are calculated,and the most disadvantageous position of the bridge under the earthquake is studied.Then the dynamic non-linear time history analysis of the bridge is carried out.Considering the non-linearity of the support and pier,the seismic response of the bridge pier under the action of along-bridge artificial seismic wave is calculated.(3)Through the analysis of non-linear time history response,the seismic response of the bridge before and after using the friction pendulum seismic isolation bearings is compared,and the effect of the friction pendulum seismic isolation bearings on the vibration reduction of the steel box concrete composite beam bridge is studied.It is found that the seismic response of the fixed pier decreases significantly,the seismic response of the movable pier decreases,and the relative displacement of the pier and beam increases after the friction pendulum seismic isolation bearings are adopted.(4)The influence of pier height on the seismic isolation effect of the bridge and the influence of the parameters of the friction pendulum seismic isolation bearings on the seismic isolation effect are studied.It is found that with the increase of the pier height,the seismic isolation effect of the bridge is gradually reduced.And with the increase of the friction coefficient of the friction pendulum seismic isolation bearings,the seismic response of the pier increases,but the relative displacement of pier and beam decreases.