Study On Wind-rain-induced Vibration And The Parametric Vibration Of Cable-bridge-tower Of Cable-Stayed Bridges

In recent years due to the steel material performance, large amounts of the tension members are applied to buildings, bridges and other structures, while the tensioning cable as the main form are widely used. The amplitude of Rain-wind-induced vibration and the parameter vibration is so big and its consequence is so grievous that bridge engineers are very concerned about the problem. So in this paper, the main contents are about these two aspects, the following jobs are done:1. This paper briefly introduces several kinds of common cable wind-induced vibration. The characteristic, research methods and present research situation of rain-wind-induced vibration are introduced such as the parametric vibration.2. The spatial mechanics model of rain-wind-induced vibration of cable is established with two different initial static sag curve equations. The most difficult problem of establish the model of the RWIV is the analysis and hypothesis of the rivulet's stress and characteristics of motion. In this paper, the comparative study of RWIV will be proceeding. Aim at the problem of the model of the rivulet, a kind of the sine function is accepted, whose frequency is equal to the first-order natural frequency of cable, and another kind of the rivulet model is established on the basis of analysis on the stress of the rivulet assuming that the damping between cable surface and rivulet as the Coulomb damping force forms. Then after solving different combined models respectively, the results can be obtained. It shows that the cable is vibrating with single mode, and the amplitude of in-plane vibration is about ten times than it's of out-planning vibration. That shows that the major threat to the security of the cable is in plane. The amplitude of cable is increasing and decreasing with the growing wind speed, it decreasing with the increasing Coulomb damping force. The position of rivulet is also changed at the same time. When the rivulet quality is about 0.16kg /m, the equilibrium position of computed and experimental is very close. The wind speed under which the amplitude of cable reaches its peak is smaller when the cable with moving rivulet. And the amplitude is also smaller than the cable with assumed rivulet. It shows that the condition of rain-wind-included vibration is easy to meet. And the amplitude is also reduced, this is mainly because the amplitude of rivulet is impacted by wind and external constraints, which fails to achieve such as putative size.In considering pylon overall vibration characteristics and the bridge connecting boundary conditions is not fully equivalent to the case study of simply supported beam, the characteristics of cable-bridge-tower parametric vibration system vibration are studied. And a comparative study on bridge deck under sinusoidal excitation, irregularity excitation of cable-stayed bridge and wind-rain-included excitation of cable and the response of bridge deck is carried out. Then this paper inspected the influence of the initial response of the deck, the stiffness of the bridge and tower stiffness, the ratio between natural frequency of the cable and bridge and other parameters related to. The results show that: the ratio between the bridge and the natural frequency of cable is the essential requirement of parametric vibration, the amplitude of cable is increasing with the increasing amplitude of bridge, and the response time is significantly shortened; and the tower stiffness, the pretension of cable also have relatively apparent influence; while in rain wind induced cable vibration, with an evident vibration phenomenon, and cable vibration by the three frequency, the vibration frequency of tower has two kind of superposition.