Buffeting Response And Wind-resistant Measures Of A Triple-tower Cable-stayed Bridge In Typhoon Area During Construction

With the development of the national economy,the construction of cable-stayed bridges worldwide has made rapid progress.At the same time,in order to improve the spanning capacity of the cable-stayed bridge and obtain better economic benefits,bridge engineers are constantly improving the span of the cable-stayed bridge,and at the same time designing the cable-stayed bridge into a multi-tower form.The increase of the span of the cable-stayed bridge will inevitably reduce the structural stiffness and damping,increase the sensitivity to wind,and buffeting will inevitably occur under the action of turbulent wind.The modern long-span cable-stayed bridge generally use segmental cantilever construction methods.As the length of the assembled cantilever increases,the structure becomes more and more flexible,especially in the largest cantilever construction stage during the construction process,with lower stiffness and damping,this makes the structure more sensitive to the effect of wind than in the bridge stage.Excessive buffeting response in the construction phase will not ensure the safety of construction personnel and machinery,and may even cause direct damage to the structure.In this dissertation,temporary piers are used as wind-resistant measures to control the buffeting response of a triple-tower cable-stayed bridge across the sea in the construction stage,and the frequency domain method is used to analyze the buffeting response during the construction stage to find out the reasonable positions imposed by the temporary piers and analyze the damping effect of temporary pier.The main research contents of this dissertation are:1.The research status of wind-resistant measures in the construction stage of long-span cable-stayed bridges and put forward the significance of the research done in this dissertation is introduced.Then summarized the turbulence related characteristics of the atmospheric boundary layer and the simulation of the turbulence wind field in the aerodynamic admittance function identification test.In addition,the buffeting analysis theory of long-span bridges is introduced,including classic buffeting force theory,theoretical analysis method of buffeting response,aerodynamic admittance function,etc.2.With a triple-tower cable-stayed bridge under construction as the engineering background,the large-scale finite element analysis software ANSYS was used to establish the finite element model of each cantilever construction stage of the side and middle towers of the triple-tower cable-stayed bridge over the sea,and analyze its dynamic characteristics.Based on the wind tunnel laboratory of Southwest Jiaotong University,the triple-component force coefficient and aerodynamic derivative of the main beam of the background project were measured.In addition,the aerodynamic admittance function of the main girder of the tripletower cable-stayed bridge across the sea was identified by the pressure measurement method.Finally,the frequency domain method is used to calculate the buffeting response of the tripletower cable-stayed bridge over the sea in each construction stage with the length of the construction cantilever,and the influence of various parameters on the buffeting response of the bridge structure is analyzed.3.The triple-tower cable-stayed bridge across the sea is located in a typhoon area.The design wind speed is high and the structure has a large buffeting response.According to the results of the buffeting response research during the construction stage,temporary piers are used as wind-resistant measures to analyze the vibration reduction of the construction process.For the cantilever construction process of a long-span cable-stayed bridge,when the construction reaches a certain cantilever length but does not reach the maximum cantilever length,the structure may have excessive response to the buffeting displacement of the main girder,excessive response of the internal force response of the tower bottom and construction comfort does not meet the requirements and other issues.In order to find a reasonable location for temporary piers,the anchoring positions of each pair of stay cables and the main girder were taken as a reference,and combined with typical construction stages,the number of construction stages of the cantilever construction process of the triple-tower cable-stayed bridge over the sea was divided.The cantilever construction stages of the side tower and the middle tower are 25 and 24 respectively.Through the analysis of buffeting response in each cantilever construction stage,the law of structural buffeting response changing with the length of the construction cantilever is obtained during the construction process,and the reasonable location of temporary piers are obtained,and the vibration reduction effect of temporary piers is analyzed.