Study On Span Suspension Bridge Straddle-Type Sling Confinement Stiffness, Damping And VIV Numerical Analysis

The sling is one of the main load-bearing members of the suspension bridge and also is a kind of typical flexible structure in low wind speed, it is easy to occur vortex-induced vibration. At present, the related research mainly use the finite element method to take the problem of the vortex-induced vibration of sling simplified into the two-dimensional fluid-structure interaction, equivalently taking a section in a certain position of sling, at the same time of simplifying the force of the slings as the quality-spring-damper system. Since the installation and tension of sling is after the erection of the stiffening girder and main cable, so the sling stiffness and sling damping ration are influenced by the sling stiffness when sling initial tension, length, diameter, wind speed, constraints and sling position changes. Therefore, the study of the stiffness and damping ration of the quality-spring-damper system is important to the influences of the vortex-induced vibration of straddle sling of long-span suspension bridge and master the two-dimensional fluid-structure interaction of three-dimensional structure. Therefore, the main research work are as follows:In order to determine the stiffness and factors of straddle sling of long-span suspension bridge, clearing the sling confinement stiffness of the two-dimensional fluid-structure numerical modeling. This article uses theoretical derivation and finite element method analysis the influence of the sling confinement stiffness when sling initial tension, length, diameter, wind speed, constraints and sling position changes. The conclusions are drawn as follows: Finite element numerical simulation results are consistent with the theoretical analysis. Finite element method and theoretical derivation have been confirmed to each other. When the initial tension and diameter of sling are increasing, its confinement stiffness will increase. When the length of confinement sling is increasing, its confinement stiffness will decrease. The confinement stiffness of sling is affected by wind speed. Comparing with the two ends of hinge constraint, the two ends of fixed constraint will be more beneficial to increase the confinement stiffness of sling. The confinement stiffness in the middle of sling is smallest. From the middle to the end, the confinement stiffness of sling is gradually increasing. Therefore, calculating sling Fluid-Solid Coupling, the value of sling confinement stiffness differ depending on sling initial tension, length, diameter, wind speed, constraints and sling position.The definition of galloping on straddle sling damping ratio of long-span suspension bridge and its influencing factors analysis is the key problems encountered in the design, and at the moment, the sling damping ratio of practical engineering significance in sling two-dimensional fluid-structure interaction is uncertain. To take advantage of the two-dimensional fluid-structure coupling calculation of wind vibration characteristics of sling in practical engineering, In which the stiffness and damping ration of the sling section is important, in order to study the damping characteristics of the sling section, using free damped vibration and finite element method analysis the influence of the sling damping ratio when sling initial tension, length, diameter, wind speed, constraints and sling position changes. The conclusions are drawn as follows: When the initial tension of sling are increasing, its damping ratio will increase, When the diameter and length of sling are increasing, its damping ratio will decrease. The damping ratio of sling is affected by wind speed. Comparing with the two ends of hinge constraint, the two ends of fixed constraint will be more beneficial to increase the damping ratio of sling. The damping ratio in the middle of sling is smallest. From the middle to the end, the damping ratio of sling is gradually increasing. Therefore, calculating sling Fluid-Solid Coupling, the value of sling damping ratio differ depending on sling initial tension, length, diameter, wind speed, constraints and sling position.On the basis of the clear method of sling stiffness and damping ratio of long-span suspension bridge, this article put forward a method of the two-dimensional fluid-structure interaction of three-dimensional structure of sling vortex-induced vibration, and using this method to analysis the characteristics of the sling vortex-induced vibration. By contrast with the existing literature, verifying the correctness of the two-dimensional fluid-structure interaction of three-dimensional structure of sling vortex-induced vibration. Building the finite element model of the sling, studied the sling stiffness and sling damping ratio impact the sling vortex-induced vibration. The results show that: with the decrease of sling stiffness, the dimensionless amplitude of sling increased; when it increases to a certain level, the amplitude of increase is slow, it conforms to the phenomenon of “self-defined” of sling vortex-induced vibration; with the decrease of sling damping, the dimensionless amplitude of sling increased; the greater of sling damping,the smaller of the sling dimensionless amplitude; at present, in most of the two-dimensional fluid-structure interaction of three-dimensional structure of sling vortex-induced vibration, the number of sling damping is bigger than the actual, the damping is different with the true damping of sling, therefore, the computational lock winds of the two-dimensional fluid-structure interaction of three-dimensional structure of sling vortex-induced vibration is bigger than the practical lock winds of the two-dimensional fluid-structure interaction of three-dimensional structure of sling vortex-induced vibration, and the computational dimensionless amplitude is also litter than the practical dimensionless amplitude of the two-dimensional fluid-structure interaction of three-dimensional structure of sling vortex-induced vibration...