Research Of Aerodynamic Interference Effects On Long-span Bridges With Twin Separate Parallel Decks

In recent years, the bridges with Twin Separate Parallel decks(TSP decks) aredesigned frequently in order to accommodate increase of traffic volume for theirspacious visual effect and good driving conditions. Due to complex section and smallnet distance, there exist aerodynamic interferences between TSP decks. Static wind load,characteristic of vortex-induced vibration, flutter stability of TSP decks are differentfrom those of single deck because of such aerodynamic interferences. Aerodynamicinterferences have become one of the key problems in wind-resistant design oflong-span bridges with TSP decks.The research status of aerodynamic interferences of long-span bridges with TSPdecks was firstly summarized in detailed in present paper, then aerodynamicinterferences of a Yangtze river bridge under construction with TSP decks was studiedsystematically based on computational fluid dynamics(CFD) method. The main contentsof this thesis are as follows.1. First, Using the k SST turbulence model to simulate the three representativesections(rectangular section, Π shaped section and streamlined section), thencompared with the results of wind tunnel experiments to verify the reliability ofnumerical simulation. And by changing the spacing of tandem TSP decks of the threerepresentative sections to study the variation law of aerodynamic coefficients underdifferent conditions.2. Taking a Yangtze river bridge under construction as a prototype, usingcomputational fluid dynamics(CFD) method to simulate the aerodynamic interferenceand consider the impact of wind attack angle, rostrum and guide wing on the threecomponent coefficients. The results show that the Reynolds number have an effect onthe three component coefficients of twin decks bridges with long span, and the dragcoefficient decreases with increasing Reynolds number and vibrates heavily in the lowReynolds number region. The aerodynamic interference weakened after additionalaerodynamic measures(rostrum, guide wing) made, and in a certain range the liftcoefficient, torque coefficient decrease over the bridge of the original section. Withdifferent aerodynamic measures, it is similar to the law of Reynolds number effectingon the aerodynamic coefficients of bridge section, and the flow field characteristics arebasically the same in different Reynolds numbers.3. It is easy to occur vortex-induced vibration(VIV) under comparative low wind speed, and this is also our focus. Because of the complexity of the VIV problem, there isnot a systematical theory and method formed, and still using the wind tunnelexperiments to see whether the VIV exists in the design stage. Aerodynamicinterference effects between the windward and the leeward of TSP decks were simulatedby computational fluid dynamics(CFD) method through Fluent, and consider the impactof wind attack angle, rostrum and guide wing on VIV. Considering the practicalengineering, the blunt body section is a process of interaction in the flow field, byintroducing User Define Function(UDF) to consider the influence of the aerodynamiccoupling, and find the calculated results is approach and prove the aerodynamiccoupling has less effects.The research results of the article can provide reference and guidance for the furtherstudy of aerodynamic interference effects on long-span bridges with Twin SeparateParallel decks and the wind resistance design of practical engineering.