Study On Wind Induced Structural Dynamic Elastoplastic Deformation Based On Slepian Model

At present,only elastic response of structures under wind load is considered for wind resistant design of engineering structure.Structures usually enter elastic-plastic stage and even collapse when structures are subjected to rare strong winds.However,current structural wind resistance design does not consider the influence of elastic-plastic deformation on structural safety under rare strong wind.Since wind loads histories are random processes,it is necessary to evaluate the wind-induced elastic-plastic response of structures in a probabilistic view.If nonlinear dynamic elastic-plastic analysises of structures under wind loads are directly employed to calculate the plastic deformation,the time-consuming is serious.Therefore,it is of great significance to propose a simplified calculation method for the probability distribution of wind-induced elastic-plastic response.However,there is a lack of relevant research work at present.Some scholars have proposed a method to estimate the probability distribution of plastic deformation of single-degree-of-freedom model based on slepian model,but the method is only applicable to the zero mean and white noise excitation.Wind loads have the characteristics of non-white noise and non-zero average.The traditional slepian model method to estimate the probability distribution of plastic deformation of single-degree of freedom model can not be directly used to estimate the probability distribution of structure plastic deformation under wind loads.In this thesis,based on the slepian model proposed by predecessors to calculate plastic deformation probability distribution of single-degree-of-freedom model under white noise and zero mean loads excitation,an improved method was proposed to make the slepian model suitable for the probability distribution of wind-induced plastic deformation.The method proposed this thesis was used for estimating single story frame plastic deformation probability distribution.The influence of load parameters and structure parameters on the plastic deformation are studied.The results are as follows:(1)The basic principle of calculating probability distribution of plastic deformation based on slepian model is systematically introduced.The method takes the single-degree-of-freedom system as the research object.Based on the associate linear oscillator(ALO),the ideal elasto-plastic oscillator(EPO)plastic deformation was calculated.slepian model is used to solve the plastic deformation and plastic deformation probability distribution of EPO.This method is only suitable for white noise load with non-zero mean value.(2)Due to the non-white noise excitation of wind load,the slepian model can not be used to estimate the probability distribution of wind-induced elastoplastic effect.In this thesis,,narrow-band extremum theory is introduced based on the slepian model for flexible structures whose wind vibration response is mainly controlled by resonance response,and the plastic deformation estimation theory of slepian model is extended to the probability analysis of elasto-plastic effects of structures under wind loads.Based on the fact that mean wind loads don’t affect the extreme probability distribution of structural response under fluctuating wind loads since ALO is a linear elastic system,the formula of conditional extreme probability distribution of ALO displacement response under non-zero mean value loads are derived in this thesis.According to the assumption that the energy dissipation beyond the elastic limit of ALO and EPO is equal,the theoretical formula of probability distribution of plastic deformation of wind-induced EPO is obtained.(3)A method for probability assessment of wind-induced plastic deformation of single-layer frame structures based on slepian model was proposed,and an example was analyzed and verified.The influence of load parameters and structural parameters on the probability distribution of interlayer plastic deformation is also studied.With the increase of mean square error of mean wind load and fluctuating wind load,the plastic deformation and the mean plastic deformation both increases gradually when the same probability occurs.With the increase of natural frequency and damping ratio,the plastic deformation decreases.When the natural vibration frequency is small,the mean value changes greatly,and the plastic deformation of structure is very sensitive to the natural vibration frequency.