Modal Jumping Behavior And Its Effects On Vortex-induced Vibration Of Cable-stayed Bridges

The developments in materials science, manufacturing technology and construction techniques prompted the structure of cable-stayed bridges turn towards to extra-long span and becoming light-mass. This kind of complex structure with low structural damping, high-flexibility, and long-span is easily generate complicated wind-induced vibration under the effect of moving vehicles, wind and rain. Wind-induced vibration of long-span bridge structure have becoming one of the safety factor that cannot be ignored in the design of bridge engineering. Vortex induced vibration is a kind of wind-induced vibration with self-induced properties, often occurs in the lower wind speed, which is likely to affect comfort of traffic current and pedestrian, in serious cases, and may even reduce the structure endurance of cable-stayed bridges. Therefore, the study vortex induced vibration response of cable-stayed bridge has important significance.Structure composed by multi-component composition, with the characteristics of global structures symmetry or local substructures symmetry, which has a complex dynamic behaviors. The disturbance variation of physical parameter in the complicated systems will result in model jumping phenomenon which performed as mode exchange of two adjacent mode. Inherent frequency with the specific characteristics of sensitivity to parameter, on which will inevitably leads to significant difference between the actual situations and the calculated vibration response that depends. In this paper, the modal jumping behavior of cable-stayed bridge and its influence on the response of vortex induced vibration are studied. Content includes:(1) the bridge deck is modeled by using Euler-Bernoulli beam method. The nonlinear and linear partial differential equations that govern transverse and longitudinal vibrations of the stay cables and transverse vibrations of segments of the deck beam, respectively, are established, as well as their boundary and matching conditions;(2) the frequency equation of the undamped linearized cable-stayed bridge is derived. Numerical analysis the minor variations of stay-cable physical parameter, the length and initial sags of cable, effects on the natural frequencies and mode shapes of the cable-stayed bridge which has the properties of global symmetry and local symmetry;(3) with consideration of the directional boundary conditions, researched dynamic behaviors of the cable-stayed bridge, which is take into consideration of the combined influences of mode jumping caused by minor variations of the effective length and vortex induced vibration.Results of numerical calculated yield the following conclusions:(1) there are closed natural frequencies of the cable-stayed bridge;(2) the phenomenon of mode jumping and mode localization that occurs on the cable-stayed bridge, which are accompanied by curve veering for natural frequency of the cable-stayed bridge;(3) the mode jumping phenomenon occurs easily in symmetric structure than asymmetric structure;(4) the vortex induced vibration response of the cable-stayed bridge with the increasing of wind speed will be repeatedly switched between period doubling bifurcation and inverse period-doubling bifurcation under take consideration the situation of mode jumping.