Research On Dynamic Testing And Model Updating Of Spatial Grid Structure

Space grid structure is widely used in large span structures such as stadiums and conference halls.Accurate simulation and calculation of the dynamic and static characteristics of this kind of grid structure is the premise of efficient design and safe use of this kind of structure.Firstly,based on the finite element software of ANSYS,the finite element model of LINK8 bar element and BEAM189 beam element was selected in this paper to simulate the articulation and rigid connection of nodes,seek the most suitable modeling mode and element type for the grid,and preliminarily determine the size of the grid structure and the size of the bar through static and dynamic analysis.The optimal element of grid structure is Link8 element.Secondly,from the experiment preparation,component design,sensors,data acquisition,parameter extraction of grid structure dynamic test was carried out relatively complete study,analysis of the traditional fast Fourier transform method and complex index method in the identification of modal parameters,provide suitable for finite element model updating is modal parameters to provide effective methods.The analysis shows that the complex exponential method has the advantages of high accuracy and less data.Finally,the finite element model of the grid structure is modified based on the modal parameters of dynamic test.By calculating the frequency relative sensitivity of six different design parameters of the finite element model,four parameters which are sensitive are selected as correction variables.Based on modal frequency and modal vibration mode error as the objective function,the density of chord and bottom chord above on elastic modulus,density and the density of the web for variable quadratic programming problem,and by using the ANSYS first-order optimization algorithm to solve the quadratic programming problem,through iteration finally to optimize the design of the model and the corresponding model parameters are obtained.The results show that the sensitivity analysis of the design parameters can reduce the workload of the correction process,and the combined mode frequency and modemode corresponding MAC value correction method has high accuracy,fast convergence and no distortion matrix,which can provide a reference for researchers and engineers to correct the finite element model.