Study On Dynamic Reliability Of Non-stationary Buffeting Of Long-span Suspension Bridges Based On First Exceeding-Probability

With the rapid development of today’s society,and in order to better meet the travel needs of the masses,the number of Bridges under the wind environment in complex mountainous areas will increase rapidly.In complex wind environment,the stiffness of bridge structure will decrease with the increase of span,so the response of bridge structure to wind will be more and more sensitive,and the reliability of bridge structure will be paid more and more attention by designers and people.However,when studying the fluctuating wind,most scholars often simulate the fluctuating wind as a stationary random process,which is not suitable in the actual situation.According to the measured data,the wind speed is a non-stationary and non-Gaussian random process under the complex wind environment,especially under the strong wind action.Therefore,the impact of non-stationary wind speed on the response of structure and the dynamic reliability of structure has become an important research topic,and most scholars also take the displacement response value as the Gaussian stationary random sample to calculate the dynamic reliability of structure,which is unreasonable.Therefore,based on a calculation method of first cross probability,this thesis calculates and analyzes the structural buffeting dynamic response of long-span suspension bridge under non-stationary wind speed.The specific work of this thesis is as follows:(1)Study the calculation method of reliability,select the failure criterion and failure mechanism of the first cross probability,and have an in-depth understanding of the crossing rate of the first cross probability mechanism,which lays a foundation for subsequent analysis.Based on WAWS to simulate the stationary random process,again according to the evolutionary spectrum theory to modulation of stationary random process,the formation of non-stationary wind speed samples,and then the measured wind speed is detected by runs-test,wavelet analysis of the measured wind speed samples after separation of time varying mean and fluctuating wind wind,in-situ pulsating wind spectrum analysis and fluctuating wind speed model,The rationality is verified by comparing with the corresponding standard spectrum.Wind speed loading was carried out on the simulated wind speed samples to obtain the load time history value applied on the bridge main beam nodes.The displacement response time history was obtained by solving the finite element software.The displacement time history was also detected by the runs-test,and finally the displacement response value was analyzed.(2)The time-history of non-stationary and non-Gaussian displacement response was calculated for structural reliability analysis.Based on the first cross probability mechanism,the non-stationary and non-Gaussian data of the time-history samples were processed by different methods,and then compared with the time-history reliability results obtained from the calculation of stationary wind speed.Analyzing the calculation result of stationary wind speed and non-stationary non-Gaussian random process transformation to obtain the results of reliability calculation of large,if continue to wind speed in the practical engineering consideration for stationary random process,will overestimate the reserves estimates,it is not suitable,at the same time for non-stationary wind speed of wind Angle of attack and modulation function of parametric analysis,It is found that the reliability of each node decreases to a certain extent with the increase of wind attack Angle,but it is not obvious.The reliability of the modulation function does not change significantly with the change of parameter α,but it also increases with the increase of parameter β.