零风速下桥梁主梁断面的自由振动响应

Free vibration response of bridge deck section at zero wind speed

基于ANSYS FLUENT12.0,采用任意拉格朗日-欧拉(ALE)方法和弱耦合方法搭建了求解气动弹性问题的数值计算模型,提出了零风速下桥梁断面气动力的理论表达式,模拟了薄平板断面和大贝尔特桥主梁断面在零风速下的自由振动响应.基于所提出的气动力模型识别出了相应的气动力系数,进而计算出模型的振动频率和阻尼比,并分析了气动力对零风速下桥梁断面的自由振动响应的影响.结果表明:零风速下模型在振动时,对周围空气的干扰作用最小的是侧弯,其次是扭转,最大的是竖弯.当模型在竖弯振动时,若忽略周围空气的气动干扰作用,将会带来较大的误差.

Based on ANSYS FLUENT12.0, numerical simulation model for solving aeroelastic problems is presented by using Arbitrary Lagrange-Euler （ALE） method and weak coupled method. The theoretical expression of the aerodynamic forces for vibrating deck section at zero wind speed is proposed. The free vibration responses of thin plate section and Great Belt Bridge deck section at zero wind speed are numerically simulated. The corresponding aerodynamic coefficients are identified based on the proposed aerodynamic force model; and then the vibration frequencies and damping ratios are calculated. The effects of aerodynamic forces on the free vibration responses of bridge decks are also analyzed. The results indicate that, when the deck section is vibrating at zero wind speed, the interference to the ambient air for the lateral motion is minimum, the torsional motion is in middle followed by the lateral motion. The effects of aerodynamic forces on the vertical vibration responses cannot be neglected, otherwise the error will be increased.