凸出架空肋梁对大跨悬挑屋盖风荷载影响研究

Study on the influence of protruding overhead rib beams on wind load of large span cantilever roof

摘要

针对某带有凸出架空肋梁的大跨悬挑屋盖，采用RANS方法开展风压分布模拟研究，并基于风向变化，通过定义风压干扰因子IF，探究凸出肋梁对屋盖风荷载的影响特性。结果表明:屋盖总体呈现负压，受到气流分离和锥形涡的共同作用，屋盖迎风檐口及其角部风压较大；0°～165°、180°～345°风向段屋盖上表面风压变化呈对称性，而屋盖下表面不同区域风压随风向变化具有不同步性。对比有无凸出肋梁的情况，0°风向下2种情况风场结构差异较小，但肋梁会阻止其后方涡量增值区的形成；270°风向下凸出肋梁的干扰作用显著，2种情况的屋盖上方两者风速差异明显，尾流区存在涡旋回冲屋盖，无肋梁时风速梯度大且涡量分布集中。肋梁对屋盖风压总体起到遮蔽减小效应，且对屋盖顶部区域效应更明显，270°风向减小效应最显著；在肋梁与来流夹角较小的风向段屋盖IF值对风向变化较敏感，其峰值达到-3.8和3.7，导致局部风压增大及正负压交替，0°风向下此效应更显著。

Abstract

For a large span cantilever roof with protruding overhead rib beams，the RANS method is used to simulate the wind pressure distribution. Based on the change of wind direction，the influence characteristics of protruding rib beams on the roof wind load are explored by defining the wind pressure interference factor（IF）. The results show that the overall roof shows negative pressure，due to the comprehensive effect of airflow separation and conical vortex，the wind pressure at the windward eaves of the cantilever roof and its corners is higher. The wind pressure on the upper surface of the roof varies symmetrically from 0° to 165° and from 180° to 345°，while the wind pressure at different areas on the lower surface of the roof varies asynchronously with the wind direction. Comparing the cases with and without protruding rib beam，the difference of wind field structure between the two cases is small in 0° wind angle，but the rib beam can prevent the formation of vortex value-added area behind it. The interference effect of protruding rib beam is significant in 270° wind angle，and the difference of wind speed between the two cases above the roof is obvious. There is vortex back to the roof in the tail flow area，and the wind speed gradient is large and the vortex distribution is concentrated when there is no rib beam. The rib beams have an overall shielding effect on the roof wind pressure，and the effect is more obvious on the top area of the roof，with the most notable reduction effect being in the 270° wind angle. In the wind direction section where the angle between the rib beam and the incoming flow is small，the IF value of the roof is more sensitive to the change of wind direction，and its peak value reaches -3.8 and 3.7，which leads to an increase of local wind pressure and the alternation of positive and negative pressure，and this effect is more significant in the wind angle of 0°.

关键词

大跨屋盖 / 凸出肋梁 / 数值模拟 / 屋盖风压 / 干扰因子

Key words

large span roof / protruding rib beam / numerical simulation / wind pressure on roof / interference factor

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基金资助

亚热带建筑科学国家重点实验室开放课题(2020ZB24)