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Wind and Structures
  Volume 33, Number 1, July 2021 , pages 71-86
DOI: https://doi.org/10.12989/was.2021.33.1.071
 


Aerodynamic modeling for streamlined box girders using nonlinear differential equations and validation in actively generated turbulence
Lin Zhao, Shengyuan Liu, Junfeng Yan and Yaojun Ge

 
Abstract
    In classical buffeting analysis theory, aerodynamic forces are usually expressed by a linear quasi-steady formula, and they are improved by aerodynamic admittances suitable for streamlined bridge girders. Recent studies have shown that admittances change obviously with incoming flow characteristics and aerodynamic nonlinearity, such as the frequency multiplication phenomenon, and motion-induced amplitude-related aerodynamic effects cannot be ignored in some cases. To address these problems, a nonlinear condensed subsystem equation (NCSE) suitable for wind-induced aerodynamic force modeling is established in the time domain. It characterizes aerodynamic nonlinearity with series of nonlinear differential equations and data-driven parameters. The proposed framework can be used for complex aerodynamic re-illustration related to the strong nonlinearity of streamlined box girders. To validate the precision and feasibility of the framework, sectional model experiments performed on a streamlined box girder were carried out in an active turbulence generated wind tunnel in which an adjustable array of multiple fans was assisted by actively controlled vibrating wings for a 2D turbulence condition. The case study shows that the NCSE model can be used to predict nonlinear aerodynamic forces in the time and frequency domains, even under complex stochastic flow conditions. The proposed method provides an alternative way to predict possible aerodynamics based on the condition of incoming flow with sufficient accuracy, and it can illustrate multifrequency components of aerodynamic forces.
 
Key Words
    aerodynamic force; nonlinear condensed subsystem equation; streamlined box girder; multifrequency effect; actively controlled turbulence
 
Address
Lin Zhao: State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Key Laboratory of Transport Industry of Wind Resistant Technology for Bridge Structures, Tongji University, Shanghai 200092, China/ State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong University, Chongqing 400074, China

Shengyuan Liu: State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China

Junfeng Yan: China Railway Siyuan Survey and Design Group Co., Ltd., Wuhan 430063, China

Yaojun Ge: State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Key Laboratory of Transport Industry of Wind Resistant Technology for Bridge Structures, Tongji University, Shanghai 200092, China
 

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