Aerodynamic Parameters And Aerodynamic Interference Characteristics Of Twin Box Girder

In order to make the bridge structure able to meet the current traffic demand of vehicles,or improve the wind resistance of long-span bridges,the existing technology usually designs the bridge as a twin-box girder or with twin separate parallel decks which separated from each other.Due to small net distance,under the action of the incoming wind,the upstream deck and the downstream deck will affect each other.This effect is also called “aerodynamic interference effect”,which will lead to a big difference on the wind-induced vibration comparing to the single bridge deck.Therefore,it is necessary to study the aerodynamic interference effect on this bridge section.This thesis selects the twin-box girder section from a practical project,using numerical calculations to assist the wind tunnel test.Interference factor of the static coefficient is defined as a ratio of the static coefficient of the upstream(downstream)sections and the static coefficient of the single section,so that we can study the aerodynamic parameters and aerodynamic interference effect of the upstream and downstream sections of twin-box girderFirstly,the construction of the twin-box girder and the bridges with twin separate parallel decks at domestic and abroad was introduced.The research status of aerodynamic interference of this type of bridges was summarized.The calculation theory of the wind load on bridge structures is briefly described.The overview of the recognition of aerodynamic admittance of the bridge section and the test measurement methods are summarized.Then,numerical calculations and wind tunnel tests were used to compare and study the aerodynamic interference effects of the three-component coefficient of the upstream and downstream sections of the twin-box girder with different spacings of attack at zero degrees and the interference law was summarized.Through the wind tunnel test,the variation law of the static coefficient of the upstream and downstream sections of the twin-box girder with different spacings under different wind angles of attack was studied.Subsequently,through the wind tunnel test,the variation of the three-component coefficient of the downstream box girder section under the action of oblique wind was studied.By designing different wind angles and different distances between the upstream and downstream sections to combine them into corresponding test conditions,the aerodynamic interference effects of the three-component force coefficients of the upstream and downstream sections of the twin-box girder under inclined wind were studied and some rules were summarized.Finally,a wind tunnel test was conducted under the turbulent flow field of the grid.Simultaneously acquiring aerodynamic forces of upstream and downstream bridge segment models with two high-frequency dynamic balances to study the variation of the aerodynamic admittance of the upstream and downstream sections of the twin-box girder with spacing.