扭弯频率比对π型断面节段模型后颤振特性的影响  

Influences of the torsional-bending frequency ratio on post-flutter characteristics of aπ-shaped section model

作　　者：张志田 汪志雄 郄凯 谭卜豪 ZHANG Zhi-tian;WANG Zhi-xiong;QIE Kai;TAN Bu-hao(College of Civil Engineering and Architecture,Hainan University,Haikou 570228,China;College of Civil Engineering,Hunan University,Changsha 410082,China;Guangdong Communication Planning&Design Institute,Guangzhou 510507,China)

机构地区：[1]海南大学土木建筑工程学院,海南海口570228 [2]湖南大学土木工程学院,湖南长沙410082 [3]广东省交通规划设计研究院股份有限公司,广东广州510507

出　　处：《振动工程学报》2021年第6期1268-1275,共8页Journal of Vibration Engineering

基　　金：国家自然科学基金资助项目(51938012,51578233)。

摘　　要：以某π型断面桥梁为对象,通过弹性悬挂节段模型风洞试验,识别了机械阻尼随振幅的非线性演变特性。在此基础上,研究了扭弯频率比为0.872,0.971,0.988,1.035,1.085,1.245六种情况下的颤振临界风速及非线性后颤振振动特性。试验结果表明模型在来流风速超过临界风速后出现极限环振动,且极限环振动的幅值随风速增加而增大。扭弯频率比对模型气弹响应的多方面特性均有实质性的影响,包括颤振临界风速、后颤振极限环振动幅值、后颤振幅值随风速的演变路径、竖向与扭转的耦合程度以及颤振的“软硬”性质等等。研究结果表明,颤振发生时,竖向与扭转自由度以同频率但非零相位差的形式进行耦合,且相位差随风速与扭弯频率比的变化显著。受气动刚度影响,模型扭转振动频率随风速的增加单调下降,但即使对于初始扭弯频率比小于1的情况,颤振时仍然以竖向与扭转自由度耦合的形式发生,这一点与流线型断面的经典耦合颤振有明显的不同。该研究也反映了现行的公路桥梁抗风设计规范在体现扭弯频率比影响方面的不足。A bridge with a main girder ofπshaped sectional configuration is concerned in this paper.Nonlinear properties of mechanical damping with respect to motion amplitude are first determined by wind tunnel tests of an elastically suspended section model.On this basis,flutter thresholds and nonlinear post-flutter vibration characteristics with torsional-bending frequency ratios of 0.872,0.971,0.988,1.035,1.085 and 1.245 are investigated.The results show that the motion always ends up with limit cycle oscillations(LCO)beyond the flutter thresholds,and the LCO amplitudes of post-flutter increase with the wind speed.The torsionalbending frequency ratio has a substantial impact on the aeroelastic response of the model in many aspects,including flutter threshold,post-flutter LCO,evolution path of the post-flutter LCO with respect to the wind speed,extent of coupling between the vertical and torsional motions,and even the“soft”or“hard”nature of the flutter,etc.The vertical and torsional motions are coupled at the same frequency but with a non-zero phase angle which varies significantly with wind speed and torsional-bending frequency ratio in the post-flutter state.Due to the influence of aerodynamic stiffness,the frequency of the model torsion decreases monotonously as the wind speed increases.However,coupling occurs even when the initial torsional-bending frequency ratio is less than 1.0,which differs obviously from the classical coupled flutter characteristic of streamlined sections.This paper also shows that the current design code for wind resistance of highway bridges is insufficient in dealing with the influence of torsional-bending frequency ratios.

关 键 词：桥梁 风洞试验 后颤振 耦合特性 极限环振动 

分 类 号：U44.3[建筑科学—桥梁与隧道工程] TU311.3[交通运输工程—道路与铁道工程]