Study On Wind Characteristics And Aerostatic Performance Of Pedestrian Suspension Bridge In The Mountainous Valleys

The main aim of this thesis is to investigate the wind characteristics of a valley in the mountainous area and analyze the influence on the aerostatic performance of pedestrian suspension bridges.The wind characteristics of the bridge sites in mountainous area has been investigated over semicentury,and numerous paper and thesis has been published.But the research findings almost only suited for the studied terrain.Though some researchers used simplified valleys model to carry out wind tunnel test.The number of tests is limited to get mathematical relation between wind characteristics and valley dimensions.Therefore,in this thesis CFD is used to simulate the airflow over a series of dimensionally varying valley to conduct general-applicable conclusion and mathematical model.These results along the bridge span should be non-homogenous and give rise to the unusual aerostatic performance of pedestrian suspension bridges.The main work and objective of this thesis are organized as follows:(1)The wind characteristics of a bridge site in a Y-shaped valley are studied by wind tunnel test.A4.5 km diameter area at the center of the field station was selected for modelling at a scale of 1:1500.The wind characteristics,including average wind profile,accelerating effect,the wind attack angle,and the turbulence and power spectral density are discussed,especially for some sites such as the bottom of the valley center,on both sides of the slope and the mountaintop of peak.(2)A long–period field measurement has been carried by a Model VT-1 Phased-Array Doppler Sodar System and a Gill 2-D sonic anemometer.The observation data is analyzed and the differences between field measurements and wind tunnel test is discussed.(3)CFD simulation with the standard k-?,k-? and SST turbulence models are run by CFX package in ANSYS to model the airflow over the Y-shaped valley.The k-? turbulence model is optimal by comparing with wind tunnel test.(4)CFD simulation with k-? turbulence model is employed to model the airflow over the simplified V-shape valley with section of Sine function.The influence on wind characteristics by slope of the valley,approaching flow direction and the curving valley are investigated.As results,some general conclusion and mathematical models are conducted.(5)The aerostatic performance of a long-span pedestrian suspension bridge is analyzed under a series of non-homogenous wind characteristics of mountainous valley.An additional criterion is put forward with a view to the pedestrian safety.Preliminarily,the torsional displacement limitations of bridge girder is proposed based on the slips and fall of pedestrian.The research achievement could be significant for engineering application,which provides guidance for bridge design in mountainous area.Also,it gives a reference for aerostatic performance analysis of long-span pedestrian suspension bridge straddled a valley.