Research On Natural Vibration Characteristics And Seismic Response Of Small Radius Curved Steel Box-Concrete Composite Continuous Girder Bridges

Small radius curved concrete box girder bridges have complex irregularities and significant spatial effects due to their curvature.The bending and torsion coupling effect of the main girder is obvious under the action of an earthquake,and the piers are in a multi-directional coupling force state of compression,bending,shear and torsion.In the research statistics of many major earthquakes,serious earthquake damages have occurred in curved beam bridges.The mechanical characteristics of curved steel box-concrete composite continuous girder bridges are more complicated,but it is found through literature research that there are few practical applications and related seismic studies of this type of bridge.Based on the existing research,this paper analyzes the natural vibration characteristics,seismic response and seismic isolation control of the small radius curved steel box-concrete composite continuous girder bridge.The main research content,conclusions and results obtained are as follows:(1)The finite element model of the curved steel box-concrete composite continuous beam was established based on the ANSYS Workbench platform,and the influence of the curvature radius and the change of the middle beam on its natural vibration characteristics was analyzed.The full bridge model was established by Midas Civil,and the natural vibration characteristics of the full bridge were compared and analyzed.The radius of curvature and the sensitivity of pier height changes.The results show that the radius of curvature and the middle cross beam have a greater influence on the torsional mode of the curved continuous beam,which should be paid enough attention;the natural frequency and mode of the full bridge structure are less affected by the change in the radius of curvature,but are more affected by the change in the height of the bridge pier.(2)Using the seismic response spectrum analysis method,the influence of different input angles of ground motion on the seismic response of small-radius curved steel boxconcrete composite continuous girder bridges is explored;on this basis,the effect of structural parameters such as the radius of curvature and the height of the bridge pier is investigated.The most unfavorable input angle of ground motion and the influence of seismic dynamic response.The results show that the most unfavorable input angle of ground motion for curved steel box-concrete composite continuous girder bridges is affected by multiple factors,and the seismic demands of its key parts under different curvature radii and ground motion input angles are inconsistent,and comprehensive consideration is needed.In order to achieve a good seismic effect of the structure as a whole;the seismic response of the bridge is more sensitive to changes in the radius of curvature and the height of the bridge piers.Attention should be paid to the adverse effects of the bending-torsion coupling spatial effect when the curvature is small and the pier height difference of the curved continuous beam bridge.The harmful effects of great value.(3)Using dynamic time history analysis method,the influence of key ground motion parameters such as PGA/PGV value,peak ground acceleration and multi-dimensional ground motion input on the seismic response of a small radius curved steel box-concrete composite continuous girder bridge is studied.The results show that ground motions with smaller PGA/PGV values will generally lead to smaller radius curved girder bridges with greater main girder displacement response and pier internal force response,but the inplane torsion of the main girder has a smaller correlation with the PGA/PGV value;The increase in the peak acceleration of ground motion will not only cause greater seismic response of the curved girder bridge structure,but also cause greater in-plane torsion of the main girder of the structure;the seismic response and earthquake of the small radius curved steel box-concrete composite continuous girder bridge The dynamic dimension is closely related,and the seismic analysis should be carried out considering the multidimensional ground motion excitation.(4)The effects of lead rubber bearings and seismic blocks with different parameters on the seismic response and isolation effects of seismic isolation curve steel box-concrete composite continuous girder bridges under high-intensity earthquakes are explored.The structure shows that although the seismic isolation bearing can reduce the seismic response of the bridge pier,it will cause excessive bearing displacement.Properly optimizing the bearing parameters can reduce the bearing displacement to a certain extent and further improve the seismic reduction and isolation effect;The setting of the antivibration block can effectively limit the radial displacement of the support,the change of the strength of the stop and the gap,and the influence on the displacement of the support and the damping effect is mutually constrained,and the optimal parameter setting balance point needs to be determined.