Study On Seismic Performance And Isolation Measures Of Double Deck Steel Truss Continuous Beam Bridge

As the traffic becomes more and more congested,the double deck bridges also appear,which effectively relieves the traffic pressure.Compared to single layer bridge,the structure of double deck bridge is complicated,and the structural damage is complicated under the action of earthquake.Therefore,it is necessary to study the seismic performance of the double deck bridge and take some measures to reduce the seismic response of the structure.In this paper,the structural dynamic characteristics of the double deck steel truss continuous beam bridge are analyzed.On this basis,the seismic performan ce and seismic isolation measures of the double deck steel truss bridge are studied.The contents of this paper are as follows.(1)The relevant literature on double deck bridges at home and abroad is consulted,and the research status of seismic and seismic isolation of double deck bridges is summarized.Taking the Dao Qing Zhou Bridge double deck steel truss continuous girder bridge as the engineering background,The finite element analysis model of double steel truss continuous beam bridge is established and the dynamic characteristics of double steel truss continuous beam bridge are analyzed by SAP2000.(2)According to the site conditions of the real bridge,the appropriate ground motion is chosen to simulate the earthquake action.Through nonlinear time history analysis,seismic response of the structure shows that the elastic state of fixed piers can not be maintained under the action of rare earthquakes,and the relative deformation of the upper and lower steel truss structure is relatively large in the original design scheme(no seismic isolation measures are taken).Therefore,it is necessary to take the seismic isolation measures to reduce the seismic response of the structure and ensure the safety of the structure.(3)Through the analysis of the mechanical model of the FPB support,the performance of the shock isolation depends on the radius of curvature R and the friction coefficient of the FPB support.The research is as follows:the optimization of the layout of the friction pendulum support is carried out,and the whole bridge isolation scheme is adopted by comparative analysis;With the increase of R,the seismic response of the pier bottom decreases,but the main beam displacement increases.With the increase of uranium,the seismic response of pier bottom increases,but the main beam displacement decreases.In general,a large number of R and micron are optimized so that the isolation performance of FPB supports is optimal.(4)When the bridge is isolated from the whole bridge,the height difference of the vertical displacement will be produced by the support under the action of temperature and external load,which may produce additional stress.In order to get better isolation effect,a combined seismic isolation scheme is considered:fixed pier FPB bearing+other pier viscous dampers,and the damping performance of viscous dampers depends on damping coefficient C and damping exponent alpha.With the increase of C,the seismic response of the bottom of the pier increases,but the displacement of the main beam decreases.With the increase of the alpha,the seismic response of the bottom of the pier decreases,but the displacement of the main beam is increased.This indicates that the combination of the vibration isolation scheme can also effectively reduce seismic response.The study of the seismic performance and seismic isolation measures of the double deck steel truss continuous beam bridge is hoped to provide some help for the seismic design of the double steel truss bridge.At the same time,the next step of the double steel truss continuous beam bridge is prospected.