Study On Buffeting Response And Equivalent Wind Load Of Long-span Cantilever Cast-in-situ Arch Under Construction Condition

In view of the safety issues during the construction of high-level bridges,taking into account the bluff body characteristics of the arch rib section of long-span arch bridges and the increasing trend of the length of the main span,and my country’s current "Highway Bridge Wind Resistance Code" adopts the wind resistance of mountain bridges The gust equivalent static wind load is actually force equivalent,and it cannot reflect the characteristics of the equivalent static wind load and the structural stiffness and quality,nor can it guarantee the equivalent response of the structure.In order to ensure the safety of the arch bridge structure under the wind load during the construction phase and facilitate the preliminary design of the large-span arch bridge,this paper will take a large-span concrete arch bridge with cantilever casting as the research object and analyze its maximum cantilever state during the cantilever casting construction phase The buffeting response problem of the long-span suspension cast-in-place arch bridge is studied in depth,and the equivalent static wind load is studied,which provides a reference for the wind-resistant design of the large-span suspension cast-in-place arch.The main research contents of this paper are as follows:(1)Taking a large-span concrete cantilever arch and a large-span concrete-filled steel tube cantilever arch as the engineering background,the Euler-Bernoulli beam model is used to derive the out-of-plane differential control equation of the cable-cantilever curved beam structure,and the transfer matrix is used The method is used to solve the out-of-plane differential vibration governing equation of the cable-cantilever curved beam structure,which is written as a first-order matrix differential equation,and then a power series is used to express the solution of the matrix differential equation.Finally,the frequency equation is derived according to the boundary conditions of the cable-cantilever curved beam structure.In order to facilitate the engineering application,the displacement function assumed based on the boundary conditions of the cable-cantilever curved beam structure is used,and the approximate calculation formula of the natural frequency of the basic structure is deduced by the Galerkin method.(2)In order to explore the mechanism of buffeting response of long-span suspended cast-in-place arches,the horizontal wind spectrum Kamal spectrum,vertical wind spectrum Lumley-Panofsky spectrum and exponential wind field are adopted according to the completely quadratic combined CQC method and background resonance response method.The coherence function respectively calculates the buffeting response RMS value of the power spectrum of the long-span suspended cast-in-place arch under different design reference wind speeds and the contribution of each modal response to the buffeting response.(3)In order to simplify the calculation process of buffeting response of long-span cantilevered arches,based on the analysis results of the completely quadratic combined CQC method and the background resonance response method,according to the inertial wind load theory adopted in my country’s "Building Load Code",The background factor and resonance factor are used to derive the practical simplified calculation formula for buffeting response equivalent wind load of a large-span suspended cast-in-place arch.