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以某流线型钢箱梁断面为例,详细研究了主梁气动外形变化对桥梁颤振和涡振性能的影响。基于1∶50节段模型风洞试验,分别研究了箱梁的栏杆、检修车轨道、风嘴、导流板,以及斜腹板对桥梁颤振及涡振性能的影响。研究表明,栏杆和检修车轨道将弱化桥梁断面的气动性能,而风嘴和导流板则对桥梁的颤振和涡振性能有利。值得提出的是,在其他气动外形保持不变,而斜腹板倾角变为15°时,桥梁的颤振性能不仅获得了较大提升,且涡振现象还可得到消除。此现象的初步机理为:较小的斜腹板倾角可阻碍和延后流线型箱梁下风侧漩涡的形成和脱落,从而显著削弱漩涡脱落对桥梁涡振和颤振的影响。详细的气动机理还有待深入研究。此点发现对于大跨度桥梁的抗风设计具有重大的参考价值和实际意义,并已经成功应用于国内多座大跨度桥梁的气动外形设计中。
Taking the section of a streamlined steel box girder as an example, the influence of the aerodynamic shape of the main girder on the flutter and vortex performance of the bridge is studied in detail. Based on the 1: 50 section wind tunnel test, the influence of the balustrades, car track, tuyere, deflector and web on the flutter and vortex performance of the bridge was studied. The research shows that the railings and the car track will weaken the aerodynamic performance of the bridge section, while the tuyere and the deflector are good for the flutter and vortex performance of the bridge. It is worth mentioning that, while other aerodynamic shapes remain unchanged, and the inclined web inclination becomes 15 °, the flutter performance of the bridge not only obtained a large increase, but also vortex-induced vibration can be eliminated. The initial mechanism of this phenomenon is that the smaller inclined web inclination can hinder and delay the formation and shedding of the vortex on the leeward side of the streamlined box girder, which significantly weakens the influence of vortex shedding on the vortex and flutter of the bridge. Detailed pneumatic mechanism remains to be further studied. The discovery of this point has great reference value and practical significance for the wind-resistant design of long-span bridges, and has been successfully applied to the aerodynamic shape design of several large-span bridges in China.