Vertical Vibration And Fatigue Analysis Of Steel Truss Girder Cable-stayed Bridge Under Wind And Train Load

At present, there is no railway steel truss girder cable-stayed bridge opened to traffic in our country, therefore, research on vertical vibration and fatigue of steel truss girder cable-stayed bridge under wind and train loads is relatively few. With the support of the National Nature Science Foundation of China(NO.51178471),this paper analyses vertical vibration and fatigue of Yujiang steel truss girder cable-stayed bridge under wind and train load, the main research contents are as follows.(1) Time-domain buffeting analysis. Spatial fluctuating wind field of bridge site is simulated using Deodatis WAWS method in MATLAB, then static wind and buffeting force is computed. Aerodynamic stiffness matrix and damping matrix are obtained according to the relationship between self-excited force and nodal displacement, therefore,self-excited force could be taken into account using Matrix27elements. Time-domain buffeting analysis is done by ANSYS transient dynamic analysis.(2) Vehicle-bridge vertical coupling vibration. Track irregularity is simulated using German low interference power spectrum. Motion equations of two suspension systems vehicle model are derived according to the D’Alembert’s principle. The analysis method of vehicle-bridge vertical coupling vibration introduced this paper is relatively easy compared with previous studies, that is, motion equations of vehicle and bridge are solved respectively in MATLAB and ANSYS, and through multiple iterations to satisfy the geometric and mechanical coupling relationship between vehicle and bridge.(3) Vehicle-bridge vertical coupling vibration under crosswind. Only static wind force and buffeting force is computed for vehicle, then motion equations of vehicle model under crosswind are derived according to the D’Alembert’s principle. The analysis method is same as above, vertical vibration of the bridge is analyzed when train running on the windward side of the bridge.(4) Fatigue analysis of cable-stayed bridge under wind and train load. Stress time history of cables considering local bending stress and stress time history of key members are obtained through above analysis results. The rain flow counting method is used to get stress spectrum, then fatigue damage and fatigue life is computed according to linear fatigue cumulative damage theory considering the influence of the mean stress.