| Concrete-filled steel tube arch bridge fully exerts the performance of steel and concrete,and has many advantages such as low cost,good appearance and high bearing capacity,and has been developed vigorously in China.At present,domestic and international research on seismic response of concrete-filled steel tube arch bridges mainly focuses on span less than 500 m.With the increasing span of the arch bridge,the effects of material nonlinearity,traveling wave effect,seismic input dimension and nearfield pulse ground motion on the seismic response of the structure can not be ignored.Based on the research of the experimental design of 700 m span CFST arch bridge,this dissertation preliminarily studied the dynamic characteristics,seismic response characteristics and damage mode of the structure under earthquake with the help of SAP2000 and Madas/Civil.The damping scheme applicable to this structure was explored.The main work done in this dissertation is as follows:(1)A numerical analysis model of 700 m span mid-span concrete-filled steel tube(CFST)arch bridge was established by finite element software.Its dynamic characteristics were calculated by eigenvector method and analyzed.It is found that the bridge has weak transverse rigidity,dense first 10 modes,obvious coupling between adjacent modes and complex dynamic response.On this basis,the influence of brace arrangement(I-brace,K-brace and rice brace),brace stiffness and section form(I-shaped,rectangular and circular)of arch rib webs on the dynamic characteristics of the structure was studied.(2)Through direct integration method in linear and non-linear time history analysis,the effects of material nonlinearity,traveling wave velocity,seismic input dimension and near-field pulsed ground motion on seismic response of the structure were investigated respectively.On this basis,the seismic behavior of arch rib chordal tube,inter-rib transverse brace,arch upright column and boom were studied by using N-M correlation curve and demand-capacity ratio method respectively,and the damage status of each component under different PGA(peak acceleration)was analyzed,and the damage mode of the structure under weak seismic position and seismic action was revealed.(3)Considering the characteristics of seismic response of 700 m span CFST arch bridge and the damage mode under seismic action,the idea of applying BRB(buckling restraint brace)damping member in building field to 700 m span mid-span CFST arch bridge was put forward,and the arrangement principle and scheme of BRB were discussed.Taking the linear stiffness of anti-buckling brace as the parameter,three kinds of vibration reduction layout schemes were proposed.By comparing the internal force response,displacement response and BRB hysteresis curve of arch bridge at weak seismic position under three schemes,the damping effect of different damping schemes was comprehensively evaluated,and a set of relatively optimal damping schemes was given. |
