Study On Static And Dynamic Stability Of Central Steel Pylon Of Multi-pylon Suspension Bridge

Putting thousand-meter scale multi-pylon suspension bridge into engineering practice is the industrious and intelligent Chinese engineers' creative contribution to the world's bridge engineering.Due to the addition of central pylon(s),static and dynamic mechanical behavior of this type of bridge is quite different from that of traditional single-span suspension bridges,the key and difficult point in design is the treatment of central pylon(s).In this thesis,static and dynamic stability of central steel pylon of multi-pylon suspension bridge were systematically studied by the engineering background of Taizhou Yangtze River Highway Bridge,which can provide a reference for design of this type of structures.In order to investigate the issue of elastic stability of central pylon of multi-pylon suspension bridge,a continuous variable cross-section column with the bottom end fixed and the upper end elastic constraint was simplified,which leads to the issue of solving the elastic constraint stiffness of the upper end and the law of change under loading condition.Based on the traditional parabola theory of cable curve,the expression of cable restraint stiffness was derived,combined with finite element method,the law of change under loading condition was given.A practical calculation method for internal force and deformation of cable structures was established,the conclusions and solutions for the elastic stability of central pylon under two limit loading modes were derived respectively by using the above findings.On this basis,a simplified method of finite element analysis for the ultimate bearing capacity of central pylon of multi-pylon suspension bridge was established.For interaction of local and overall buckling issue,based on the thinking of solving as a whole,by accurately considering relative constraint of adjacent plate,the solution equations for local buckling of the segment(interaction buckling of plates)was derived.Possibility of interference constraint of plates and stiffener stiffness limits in design of flexible stiffener were analyzed in segment design.Based on a large number of finite element analysis results,suggested value for separation distance of diaphragm in pylon pillar was given.Based on the concept of relative slenderness ratio and precision control value in the review criteria,influence of initial geometric imperfections on the ultimate bearing capacity of the central pylon was analyzed.Preliminary study was made on the connection way between segments of pylon,locally refined multiscale finite element model for connection way of metal contact in end face combined with high tensile bolts connection was established and solved,according to the calculation results,the influence of this connection way on the ultimate bearing capacity of pylon was analyzed.Dynamic characteristics of the free-standing pylon was analyzed by using the finite element software ANSYS,moreover,the erecting process of stiffening girders was simulated by using the software BNLAS,combined with the measured data of static and dynamic field and the macroscopic performance of the whole structure during the construction of the bridge,some mechanical properties of this connection way were investigated.Based on IDA method,combined with B-R criterion which widely used in practical engineering,a method of structural dynamic stability analysis under earthquake action was established by using ANSYS finite element programming technique.According to the actual situation of the research object,dynamic stability of central pylon in longitudinal and crossbridge of horizontal earthquake were analyzed by inputing artificially generated seismic waves.