Study On Wind Characteristics Of Long-span Bridge Site In Coastal Area During Typhoon Mangkhut Landing

Affected by the subtropical climate,the southeast coast of China has become a typhoon-prone area.The statistics show that typhoon and typhoon-related disasters cause serious loss of life and property annually to these regions.With continuous construction of the traffic and road network,a series of extra-large span bridge construction projects have emerged.With the increase of bridge span,the bridge structure tends to be slender and gentle,which is more susceptible to typhoon load.The effect of wind load on the structure and the estimation of the result can only be accurately simulated through wind characteristics analysis,so the research on the wind field characteristics of the bridge site in typhoon affected area is extremely important.However,there is a lack of research on non-stationary characteristics of strong wind of long-span Bridges,and most of the national codes are established according to the normal wind.Moreover,the strong wind data simulated through wind tunnel tests cannot accurately describe the influence of topographic conditions.Therefore,in order to understand the effects of typhoon disaster and provide a scientific basis for the design and operation of Bridges in the typhoon-affected areas,it is necessary to carry out measured research on typhoon characteristics.By using anemometers located at the Shipping Channel Bridges of the long-span bridge,time histories of wind speed and direction corresponding to Typhoon Mangkhut are recorded.This paper analyzes the non-stationary model,wind characteristic parameters and time-frequency characteristics of the typhoon wind field.The main work of this paper are as follows:(1)The formation process and movement of typhoon Mangkhut,the location and geographical environment of the bridge site,and the measurement point location are briefly introduced.(2)Stationarity test of typhoon wind field at the 1# Shipping Channel Bridge site and comparative study of non-stationarity model and traditional model.Run-distance analysis method is used to test the stationarities of wind field at different heights at the bridge site,and the influence of basic time interval and window time interval on the proportion of non-stationarities of wind field is explored respectively.The empirical mode decomposition(EMD)and discrete wavelet transform(DWT)models are compared with the traditional stationary models,and the numerical differences of turbulence intensity,gust factor,peak factor,turbulence integral scale and other wind characteristic parameters are summarized under different test heights and different calculation models.(3)Analysis of non-stationary wind characteristics of typhoon at the 2# Channel Bridge site.The mean wind characteristics of the wind field at the bridge site and the fluctuating wind characteristics under the non-stationary model are summarized.and the corresponding characteristic models are established.Mean wind characteristics include mean wind speed,mean wind direction,fluctuating wind characteristics include turbulence intensity,gust factor,probability density distribution of fluctuating wind speed,peak factor,autocorrelation of fluctuating wind speed,turbulence integral scale.(4)Time-frequency analysis of typhoon at 3# Channel Bridge site.Based on the Hilbert-Huang transform,the time-frequency and amplitude energy characteristics of the wind field at the bridge site are summarized.Through power spectrum estimation,a wind spectrum model suitable for this region is obtained.Based on Priestley’s theory,the EPSD estimation of the typhoon wind field was carried out,and the evolution power spectral density model of the wind field is established.