为合理确定主跨680 m 的莫桑比克马普托大桥的主梁形式，利用节段模型风洞试验，分别研究了扁平钢箱梁、钢箱叠合梁和工字型叠合梁的气动性能。结果表明：扭转刚度较弱的工字型叠合梁颤振风速远低于检验风速，且涡激振动也不满足舒适性要求，在设计中不宜采用；钢箱叠合梁尽管颤振风速较高，但其在钢箱顶面凸起的混凝土桥面板会造成气流分离和漩涡脱落，可能存在较大涡激振动振幅的隐患，可在设计中选择性采用；扁平钢箱梁断面颤振临界风速高，且无明显涡激振动，为该大跨度悬索桥的优选主梁形式。试验结果还显示，若设置宽0．5 m 的风嘴导流板可进一步提高钢箱梁断面的颤振临界风速，但由于导流板直接影响造价并增加后期养护费用，而节段模型试验结果一般偏于保守，因此最后的取舍需要参考三维颤振计算或全桥气弹模型风洞试验结果。若在其斜腹板上外挂直径90 cm 的过桥水管，将显著弱化颤振性能和涡振性能，因此在设计中不宜采用。%To select a rational main girder type for the Maputo Bridge in Mozambique which is projected to have a main span of 680 m ,the aerodynamic behavior of three types of main girder ,in-cluding the flat steel box girder ,steel-concrete composite box girder and I-shaped composite girder were examined by the sectional model wind tunnel test .The results of the test indicate that the I-shaped composite girder with intrinsic low torsional stiffness is not a favorable solution in the de -sign ,for its flutter wind speed is much smaller than the testing wind speed and its vortex -induced vibration is not able to meet the requirements of physical and psychological comfort as well .The steel-concrete composite box girder can withstand higher flutter wind speed ,but the concrete deck slab humps on top of the steel box are prone to cause airflow separation and the concrete deck slab is likely to be shed by vortex flow ;therefore ,this type of main girder faces the latent risk of large-amplitude vortex-induced vibration ,which can be taken as an alternative solution in the design . The cross section of the flat steel box girder can bear a higher critical flutter wind speed and no sig -nificant vortex-induced vibration was found on it ,in this sense ,the flat steel box girder is regarded as the optimal main girder type for long-span suspension bridges .From the test results ,we also find that the critical flutter wind speed for the cross section of the steel box girder can be further improved by installing the 0 .5 m thick guide vanes .However ,the adoption of guide vanes will di-rectly influence the cost and will increase the later maintenance cost ,furthermore ,the results of the sectional model test are usually conservative ,thus ,the final decision should be made based on the three-dimensional flutter calculation and the results of the aeroelastic model wind tunnel test for the overall bridge .If the 90 cm diameter cross-the-bridge water pipes are hung outside the ob-lique webs ,the capacity of the main girder to counter flutter and vortex-induced vibration would be significantly weakened ,therefore this solution should be omitted in the design .
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