Study On Dynamic Characteristics And Seismic Performance Of Simply Supported Continuous Skew Small Box Girder Bridge

Skew girder bridges are more and more used in the design of highways and urban roads because they can better meet the requirements of environment and terrain.The particularity of it’s own structure leads to complex mechanical characteristics under earthquake and different failure characteristics from orthogonal bridges.At the same time,the construction method of simply supported continuous girder bridge is widely used in the construction of medium and small-span continuous girder bridges because of its convenience,low cost and short construction period.Therefore,simply supported continuous skew girder bridge has become one of the most popular structural forms in recent years.This project is mainly based on a simply supported continuous skew small box girder bridge.On the basis of summarizing current seismic research status of skew bridges,whole bridge model is established in Midas civil.The influence of different parameters on the dynamic characteristics and seismic performance of the structure is analyzed.The main contents are as follows:(1)The influence of different parameters(section form,construction method,pier setting,bearing type and skew angle)on the dynamic characteristics of the structure is analyzed.Taking the skew angle as the main parameter,the fundamental frequency calculation formula of the impact coefficient calculated in the current code is modified.Finally,the correctness of the formula is verified by the dynamic load experiment of the real bridge.(2)The seismic analysis model of the whole bridge is established for pier components,and relevant operations such as wave selection are carried out.(3)Response spectrum analysis and time-history analysis are respectively carried out on the bridge model,and the calculation results of the two analysis methods are compared to verify the correctness of the seismic analysis model.The internal force and displacement responses of the structure are calculated and analyzed under the load conditions of unidirectional and bidirectional seismic action.Finally,the influence of the most unfavorable seismic input direction,different skew Angle and site type on the seismic response of skew continuous beam Bridges is determined.(4)Taking different oblique angles,site types and seismic intensity as parameters,the displacement ductility demand and displacement ductility capacity of the structure are calculated and compared.On this basis,combined with the hysteretic curve of pier element under different skew angles,the seismic performance of the structure is analyzed and judged.(5)In view of the fact that the ductility capacity of the structure exceeds the ductility demand,the design optimization research is carried out from the structural design of piers and the selection of seismic isolation bearings.