Inversion Method of Vortex-Induced Vibration Amplitude for Long-Span Bridges with Partially Installed Noise Barrier
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摘要:
大跨桥梁的涡激共振常采用节段模型风洞试验进行测量,但节段模型试验建立在二维理论上,当桥梁由于分段式声屏障导致沿跨向存在多种气动外形时,涡振响应难以通过节段试验直接测量. 本文基于线性涡激力模型提出考虑多气动外形影响的节段-实桥涡振幅值反演方法. 首先,分别对带屏障与无屏障段截面进行节段模型风洞试验;然后,通过ANSYS谐响应分析,反演全跨布置与不布置屏障两种工况的实桥涡振幅值,获得对应的涡激荷载幅值;最后,根据声屏障实际布置位置分段施加涡激荷载,得到设置分段式声屏障桥梁的实桥涡振响应,并基于本文方法对不同声屏障布置方案进行了参数分析与讨论. 试验结果表明:全封闭声屏障会显著降低主梁抗风性能,屏障的分段布置对整体涡振影响较大;本文方法可通过节段模型试验结果直接估算多气动外形桥梁的全桥涡振响应,声屏障布置应在满足降噪条件下尽量布置于边跨,若布置长度超过桥塔位置,须尽量缩短布置长度以减小涡振响应.
Abstract:The sectional model test in wind tunnels is often used to measure the vortex-induced vibration (VIV) of long-span bridges. Since the sectional model test is based on two-dimensional theory, when the bridge has different aerodynamic configurations along the span due to the partial installation of noise barriers, it is difficult to measure the VIV response directly through the sectional model test. Based on the empirical linear VIV model, an assessment method of VIV between the sectional model and prototype bridge that considers the effects of multiple aerodynamic configurations is proposed. Firstly, the sectional model test is performed on the models with and without barriers respectively. Then, the prototype response of the noise barriers installed and not installed along the span is investigated by ANSYS harmonic analysis, and the corresponding amplitude of the vortex-induced force is obtained. Finally, according to the actual installation position of the noise barrier along the span, the vortex-induced force is imposed on the bridge and the prototype response with the partially installed noise barrier is obtained. In addition, based on the method in this paper, various noise barrier installation schemes are numerically simulated. The results indicate that fully enclosed noise barrier will significantly reduce the aerodynamic performance of the main girder and the overall VIV will be affected by partial installation of barrier to a large degree. The method in this paper can estimate the prototype response of multi-aerodynamic configurations bridges through the results of sectional model tests. The installation of the noise barrier should be arranged on the side span as far as possible under the conditions of noise reduction. If the arrangement length exceeds the position of the bridge tower, it should be shortened as much as possible to reduce the vortex-induced response.
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表 1 涡激力反演结果
Table 1. Amplitude of vortex induced force
风攻角/(°) 对应风速/(m·s−1) $A_1^* $/kN $A_0^* $/kN −3 18.8 6566.2 0 0 17.5 7198.1 0 +3 15.9 11404.8 2706.8 表 2 实桥跨中涡振幅值
Table 2. Amplitude of VIV at mid-span
风攻角/
(°)全跨无屏障幅值 全跨带屏障幅值 分段布置幅值 竖弯/
mm扭转/
(°)竖弯/
mm扭转/
(°)竖弯/
mm扭转/
(°)−3 未起振 未起振 175.6 0.079 10.4 0.017 0 未起振 未起振 192.5 0.147 11.4 0.031 +3 72.4 0.039 305.0 0.063 86.1 0.044 -
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