Study On Nonstationary Buffeting Response Of Long Span Arch Bridge In Mountainous Area During Construction

With the span of the arch bridge increasing,the stiffness of the structure in the construction phase is relatively decreasing and tends to be light and flexible,and it is more sensitive to the effect of wind.In recent years,many scholars at home and abroad through the statistical analysis of the measured wind speed samples,found that the wind field in the mountainous area and other complex environment has significant nonstationary characteristics,and the wind speed is composed of time-varying average wind and non-stationary fluctuating wind.At this time,it will be more complex to study the wind-induced vibration behavior of long-span arch bridge under the complex wind field in mountainous area.However,the traditional buffeting analysis method based on the assumption of stationary random process can not accurately predict the buffeting response of long-span bridges under non-stationary wind field in mountainous areas.Therefore,it is necessary to study the non-stationary buffeting response of long-span arch bridge during construction based on the analysis of the characteristics of non-stationary wind field in mountainous area and the non-stationary buffeting analysis theory of long-span bridge.This thesis will focus on the non-stationary characteristics of complex wind field in mountainous area and the wind-induced vibration of long-span arch bridge during construction,and carry out the research on the non-stationary buffeting response of longspan arch bridge during construction under complex wind field in mountainous area.The main research contents are as follows:(1)Dynamic characteristics analysis of long span arch bridge during construction stage.Based on ANSYS,the three-dimensional finite element model of four typical construction stages is established based on the background of a long span up bearing concrete filled steel tubular arch bridge in mountainous area.The first ten modes and frequencies are extracted by subspace iteration method.The vibration mode characteristics of each construction stage are analyzed in detail.(2)Identification of three component force coefficient of arch rib of long span arch bridge.Based on the theory of computational fluid dynamics,a two-dimensional fluid simplified model of three-dimensional space truss CFST arch rib element is established,and the reliability of the simplified model is investigated.On this basis,the threedimensional static force coefficients of a quarter span CFST arch rib section of a longspan CFST arch bridge are identified by using the two-dimensional simplified model.(3)Non stationary characteristics analysis and numerical simulation of wind field in mountainous area.The time-varying mean wind is extracted from the measured wind speed samples by WT method,and its time-varying characteristics are analyzed.Meanwhile,the measured power spectrum of downwind and vertical fluctuating wind is analyzed.Finally,based on the harmonic synthesis method and the evolution spectrum theory proposed by Priestley,the non-stationary fluctuating wind field of a long-span CFST arch bridge is successfully simulated,and its power spectrum is tested to investigate the reliability of the numerical simulation method of non-stationary fluctuating wind field.(4)Analysis of non-stationary buffeting response of long-span arch bridge during construction.The paper analyzes the non-stationary buffeting response of four typical construction stages,obtains their respective displacement time history and displacement RMS value,and makes a detailed comparison and analysis of the displacement RMS value of the four construction stages;at the same time,it analyzes the steady buffeting response of the four typical construction stages,and makes a comparison of the nonstationary buffeting response,which reflects the buffeting of the long-span arch in the construction process under the complex wind environment in mountainous areas It is necessary to consider the non-stationary characteristics of the response.Finally,the effects of inclination angle of arch rib,rise span ratio,different cross brace arrangement,wind attack angle and nonlinear effect on the non-stationary buffeting response of arch bridge in construction stage are analyzed.