Study On Galloping Of A Pylon With The Square Section And Its Aerodynamic Mitigation Measure

Along with the augment of bridge span in these years, the height of main pylons is raised correspondingly. Generally the sections of pylons are bluff, which leads to poor performance of wind resistance. The problems of wind-induced vibrations are severe especially for self-support pylons. A pylon with the square chamfer section was chosen as the experimental project, the galloping characteristics of the section and the pylon were investigated by aero-elastic model and section model wind tunnel tests. Afterward, some meaningful conclusions were drawn. The research contents of the thesis consist of several aspects as follows:(1) In the uniformity velocity field, the three component coefficients of square sections with or without chamfers were obtained by section model wind tunnel test, and the coefficient curves varying with attack angles were used as the theoretical basis of establishing galloping phenomenon. According to the linear galloping theory, the galloping performances of the square section were discussed in uniformity velocity field.(2) The galloping performances of square chamfer sections were studied, by introducing the flutter derivative H1,* (influence coefficient of aerodynamic damping on self-excited lift) which considers the unsteady effects of galloping.(3) Two aerodynamic measures were used on the square chamfer section, the improvement conditions on the galloping performances were investigated, based on the three component forces curves varying with attack angles and flutter derivatives curves varying with dimensionless velocity obtained from section model wind tunnel test.(4) Based on Den Hartog quasi-steady theory and the computational mode of the unsteady effects by introducing the flutter derivatives H1*, the critical galloping velocity was calculated. The calculated critical galloping velocities were compared with the velocity obtained from the wind tunnel tests comprehensively.(5) Wind-induced vibration performances of the pylon in two wind field were investigated, by the single pylon aero-elastic model wind tunnel test in uniformity and turbulent velocity field. The improvement conditions on the galloping in the aero-elastic model wind tunnel test were studied, from the aspects of structural damping and aerodynamic measures. Besides, the coupling situation of galloping and vortex-induced vibration observed in the test was analyzed.