| In recent years,with the development of Performance-Based on Wind Engineering(PBWE),elastoplastic and ultimate bearing capacity of structures have gradually attracted the attention of scholars at home and abroad.Long duration is one of the characteristics of wind load,and it has a significant impact on the plastic development and bearing capacity of the structure under strong winds.However,there are few studies on the definition and statistics of the wind load duration.In order to solve this problem,a new definition of duration for wind load is proposed,which combines the current definition method of earthquake duration index.Furthermore,in order to explore the interaction and variation of duration,wind speed and direction,this paper uses Copula function and gives their joint distribution formula.Finally,taking portal frame and single-degree-of-freedom(SDOF)system as examples to explore the development trend of its ultimate bearing capacity and plastic deformation through the incremental dynamic analysis(IDA)method.The main contents and conclusions are as follows:(1)In order to consider the influence of energy on the structural response during the continuous process of the storm,the method proposed by Cook is used to separate storms from meteorological wind data.In the independent storm interval,the definition of the significant duration of ground motion is used,and the calculation formula of wind load intensity is derived in combination with the Arias earthquake intensity and wind load quasi-steady assumptions and turbulence intensity.The minimum duration interval of cumulative intensity exceeding a certain proportion of total storm intensity is used as the definition of storm duration.Correspondingly,the development process of strong wind can be determined,which lays the foundation for wind-induced fatigue and structural wind-induced elastoplastic analysis.(2)According to the principle of equal strength,the equivalent wind speed expression is proposed.Further,the Copula function is used to fit the two-dimensional and three-dimensional joint distribution of wind duration,speed and direction in the storm interval to explore the relationship between parameters.And based on the historical meteorological data of certain place in Texas,the United States,the joint distribution of duration and wind speed is analyzed.The results show that the wind speed is approximately proportional to the duration,and the probability of co-occurrence of low-medium wind speed and short duration is high.Due to the limited number of samples,there is a certain deviation in the statistics of small probability events,and the possibility of simultaneous occurrence of strong wind speed and short duration cannot be ignored.At the same time,according to the joint distribution of wind speed and direction,the wind directions corresponding to the high wind speed can be quickly obtained,which provides a basis for the design of building orientation.(3)Aiming to study the effect of duration on the structural bearing capacity and plastic development,this paper uses the IDA method to carry out the wind-induced elastic-plastic analysis for the portal frame and the SDOF system respectively.By simulating the steady wind speed,the influence trend of the duration change on the ultimate bearing capacity of the portal frame structure was preliminarily explored,and it was found that the ultimate bearing capacity of the structure decreased significantly with the increase of the duration.In the analysis of the SDOF system,the random effects of wind speed,wind direction,and duration are considered at the same time,and the probability of structural failure and residual deformation is obtained by combining the combined probability distribution of wind speed-wind direction-duration through different wind load time histories.105 figures,18 tables,and 69 references... |
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