Study On Measured Wind Field Characteristics And Study On Buffeting For Long Span Suspension Bridges

Mass to carry out the construction of infrastructure in China in recent years,more and more large-span bridge structure across vast hinterland of the land in our country,especially in the western region valley and relief varies greatly,wind field characteristics of mountainous environment is very complex,in many cases the specification design wind parameters not well in the design of wind resistance.At present,in the wind resistance design of long-span Bridges,the most accurate first-hand data is usually obtained through the field measurement.This is because the wind field characteristics are the direct cause of the wind-induced vibration of structures.Whether the actual wind parameters at the bridge position can be accurately obtained will directly affect the safety of the wind resistance design of the bridge.The main contents of this paper is as follows:(1)At present,most of the existing wind observation studies are aimed at the wind characteristics of coastal or inland hilly areas,while there are few studies on the riverbank landform in mountainous areas.In this paper,the riverbank landform of the Yumen area is taken as the research object,and observation instruments are set up at different observation positions to establish temporary observation stations to collect the measured data for more than one year.Matlab was used to process the measured data during the observation period,mainly including the segmentation,screening,statistical analysis of data samples,as well as the work of parameter fitting and mapping,etc.,and the average wind characteristics and pulsating wind characteristics of the region were obtained.By comparing with the norm,it is found that there is a big deviation between the measured wind field characteristics and the norm.(2)An important research object of wind-induced vibration analysis of Bridges is wind characteristic parameters.The main reason for the errors in wind-induced vibration analysis is the determination and simulation of wind characteristic parameters.Pulsating wind is very complex,so it is necessary to compare and study the effects of different wind parameters on wind-induced vibration of Bridges.In this paper,parameters such as power spectrum,surface category and average wind speed,which are significantly different from those in the actual measurement study,are selected to simulate the pulsating wind field of the main beam,bridge tower and main cable respectively by using harmonic synthesis method.Meanwhile,the simulation results are tested,and the simulation results that meet the requirements are used in the next step of bridge chattering calculation.(3)Taking a long-span suspension bridge as the research object,the beam4 single girder model was established with ANSYS software to obtain the dynamic characteristics of the bridge.The three-component force coefficient and aerodynamic derivative of the girder section of the bridge are obtained by wind tunnel force and vibration tests.The stiffness matrix and damping matrix representing the aerodynamic stiffness term and aerodynamic damping term of the main beam are defined by using a custom matrix27 unit to express the chattering self-excitation force.On this basis,the chattering force load was loaded into the ANSYS chattering analysis model by introducing the simulation of the pulsating wind time history with different wind parameters,and the chattering response in the bridge-forming stage was compared.