Research On The Identification Methods Of Distributed Stochastic Dynamic Load In Time Domain

The dynamic load information on engineering structures is often hard to be obtained via direct measurement,research on the indirect identification method to acquire the real dynamic load on structures from measured structural response is drawn much attentions.Existed researches on dynamic load identification are mainly focusing on deterministic concentrate dynamic load,however,the real external load on engineering sturctures,such as the wind load,the aerodynamic loading,etc.have the charactoristics of distributed and stochastic.The deterministic dynamic load identification method can not directly be applied on the identification of such kind of dynamic loads,new methods on distributed stochastic dynamic load identification are needed to be investigated.Research works on the distributed stochastic dynamic load identification in time domain have been conducted in this thesis;the details can be summarized in the following parts:(1)Research on the distributed stochastic dynamic load identification method in time domain based on the modal method and Monte Carlo method is conducted.The distributed stochastic dynamic load is firstly expanded in modal space to decompose the space and time domain which enable to identify the whole dynamic load by using orthogonal basis function.Via a simulation example of a simply supported beam,the correctness of the identification method is verified;the parameters such as the order of modes,the number of measurement locations and the noise level,etc.which may affect the accuracy of the distributed stochastic dynamic load identification stochasticmethod are discussed.(2)To improve the computational efficiency of the Monte Carlo method,research on the distributed stochastic dynamic load identification in time domain based on the modal method and K-L expansion is conducted.Utilizing the K-L expansion to replace the Monte Carlo simulation,combining the modal method,the basic theory of the identification method is proposed.Via a simulation example of a simply supported beam,the correctness of the identification method is verified;the parameters such as the order of the K-L vector,the order of modes,the number of measurement locations and the noise level,etc.which may affect the accuracy of the distributed stochastic dynamic load identification stochasticmethod are discussed.A comparison of computational efficiency between the proposed method and the method based on the Monte Carlo method is also conducted.(3)To overcome the generality of the modal method,the orthogonal polynomials are adopted to replace the modal functions for representing the space distribution of the dynamic load,a distributed stochastic dynamic load identification algorithm based on the K-L expansion and finite element method is proposed.Via a simulation example of a simply supported beam,the correctness of the identification method is verified;the parameters such as the order of polynomials,the number of measurement locations and the noise level,etc.which may affect the accuracy of the distributed stochastic dynamic load identification stochasticmethod are discussed,and the method is compared with the previous methods.(4)Research on the applications of the three methods mentioned above on the stochastic fluctuating wind load identification of a high-rise structure is carried out.Based on the simulation of fluctuating wind load according to the Davenport Spectrum,the statistics and distribution of the wind load on a real wind power tower are identified.Numerical simulation results show the engineering applicability of the proposed distributed stochastic dynamic load identification method.