平行双幅桥气动干扰效应对颤振和涡振的影响

Aerodynamic Interference Effects on Flutter and Vortex-excited Resonance of Bridges with Twin-separate Parallel Box Decks

摘要:

以主跨310m的天津塘沽海河既有独塔斜拉桥拓宽工程的初步设计方案为背景，通过一系列弹簧悬挂节段模型风洞试验研究了箱形分离平行双幅桥之间的气动干扰效应对其颤振稳定性能和涡激共振特性的影响。结果显示：气动干扰效应使得箱形分离平行双幅桥与既有单幅桥相比，颤振临界风速明显降低，主要气动导数 曲线递减至递增的转折点也明显提前，颤振稳定性能变差；气动干扰效应还使得箱形分离平行双幅桥与既有单幅桥相比，竖弯和扭转涡激共振最大幅值和风速锁定区间都比的值显著增大，涡激共振起振风速降低，斯脱罗哈数有所提高。结果还显示：气动干扰效应对箱形分离平行双幅桥下风侧桥的颤振和涡振性能的影响要比对上风侧桥的影响更大。因此，在将既有桥拓宽成分离平行双幅桥时必须要考虑气动干扰效应对其颤振稳定性能和涡激共振特性的影响。

Abstract:

Taking a preliminary design alterative for the broadening engineering of the existent single-tower cable-stayed bridge, Tanggu Haihe Bridge in Tianjin, with a main span of 310m, the aerodynamic interference effects on flutter and vortex-excited resonance of cable-stayed bridges with twin-separate parallel box decks were investigated via a series of wind tunnel tests of spring-suspended sectional model. The results show that: because of the aerodynamic interference between the two adjacent separate box deck, the flutter critical wind speeds of the twin-separate box deck bridge drops evidently and the turning point of the corresponding aerodynamic derivative curve from descending to ascending is brought forward, compared with those of the existent single-deck bridge. This indicates the decline of bridge flutter stability due to the aerodynamic interference of this type. The results also demonstrated that the maximal amplitudes of the vortex-excited resonance of the of the twin-separate box deck bridge in both the vertical and torsional directions increase due to the aerodynamic interference of this type, compared with those of the existent single-deck bridge. Correspondingly, the lock-in zone of wind speed is widened, and the onset wind speed decreases making the Strouhal numbers increased slightly. It is also found that the aerodynamic interference effect between the two adjacent separate box decks is more significant on the flutter and vortex-excited resonance of the leeward deck than on those of the windward deck. In sum, it is necessary to consider the aerodynamic interference effect when broadening the existent bridge into a twin-separate parallel deck bridge.