Research On Flutter Characteristics Of Long-span Stressed Ribbon Bridge

With the rapid development of socio-economic,stressed ribbon bridge structure,as a new-type structure,has been widely used in urban construction or mountain development by virtue of its unique advantages.Among all kinds of stressed rib bon bridges,the traditional suspension bridge has the simplest structure and the strongest spanning capability.However,with the increase of span,the wind-induced vibration problem of stressed ribbon bridge will become more and more obvious.Flutter is the most important part in the wind-resistance design of long-span bridges,which should be avoided.Due to the special shape of stressed ribbon bridges,its dynamic property and flutter characteristic are different from that of the traditional suspension bridge.In view of the flutter characteristics of traditional stressed ribbon bridge,this paper takes a domestic stressed ribbon bridge with 618 m span as the research background,and the flutter characteristics of the stressed ribbon bridge are studied comprehensively through the combination of numerical analysis and wind tunnel test.The main research work of this paper is:(1)With the help of ANSYS,the modal analysis is carried out on the stressed ribbon bridge with a span of 618 m and the suspension br idge with the same span,and the differences in the dynamic properties of the two types of bridges are compared.This study considers the influence of hanger length and rise-span ratio,and analyzes the modes of several finite element models of stressed ri bbon bridges.It is speculated that the change of the hanger length could lead to the curved distribution of the main beam axis,which is the cause of the coupling vibration mode of the stressed ribbon bridge.(2)Based on the flutter derivative of the ideal plate and with the help of the 3D finite element flutter analysis method,the flutter characteristics of the stressed ribbon bridge and the suspension bridge is analyzed.The result shows that the flutter of the stressed ribbon is driven by the lateral-torsional coupling mode,while the flutter of suspension bridge is driven by the torsional mode.Based on the quasi-steady theory,this study considers aerodynamic derivatives associated with lateral motion,and th e3 D flutter characteristics of the stressed ribbon bridge and the suspension bridge is analyzed comparatively.It is found that the lateral self-excited force will be generated when the stressed ribbon bridge vibrates,but it has little influence on the f lutter prediction results of most streamlined sections,while the suspension bridge will not generate the lateral self-excited force.(3)A 2DOF flutter analysis mathematical model of stressed ribbon is derived,and five mode combinations of the stressed ribbon bridge and one mode combination of the stressed ribbon bridge are selected respectively.Then,the 2DOF flutter analysis for the stressed ribbon bridge and suspension bridge are carried out,and the results are compared with those of 3D flutter analysis.The result shows that the multi-mode participation effect of the real flutter modality of the stressed ribbon bridge and the suspension bridge is weak,while the multi-mode participation effect of the high-order flutter modality of stressed ribbon bri dge is strong,and the mode selection method of the 2DOF flutter analysis of stressed ribbon bridges is greatly different from that of traditional suspension bridge.(4)Based on the actual section of the stressed ribbon bridge,the aerodynamic derivatives identified by CFD technology was used for the 2DOF flutter analysis and3 D flutter analysis,and the sectional model wind tunnel test was carried out.The result shows that the multi-mode participation effect is still weak when the stressed ribbon bridge with actual section vibrates.The mode selection of wind tunnel test is very important,and the numerical results are in good agreement with the experimental results,and the aerodynamic derivatives identified by CFD technology has enough accuracy.