Stability Of Single-layer Spherical Reticulated Shell Structures With Random Initial Defects

As a typical representative of the new structures,the large-span spherical reticulated shell structure is widely used because of its advantages of lightweight,large span,beautiful shape and reasonable force.Those benefits can be regarded as the results of structural optimization,while the stability of the structure becomes more prominent.Besides,the single-layer spherical reticulated shell is very sensitive to the initial defect,and slight deviations can lead to a significant decrease in the stability capacity.Therefore,the stability of single-layer spherical reticular structure with defects is an important problem in the design of the reticulate structure.Compared to the existing Consistent Imperfection Mode Method(CIMM)with the Stochastic Imperfection Mode Method(SIMM)in this thesis,it may be concluded that the initial geometric defects inherent in the shell structure should be considered as randomness.However,the application of the SIMM is limited by the large number of calculations of random sampling.In addition,the study shows that the high-order buckling modes of the structure have a great influence on the stability of the structure.In contrast,the CIMM only takes the lowest order buckling mode as the initial defect of the structure is not the worst case.In view of those limitations of the present defect methods,this thesis proposes a method for calculating the stability capacity of the reticulated shell structure with random initial defect.The computational method mainly contains two steps:First step:The existing SIMSM is improved in this thesis,which is taken as the initial geometric defect simulation method for the single-layer spherical shell structure.The SIMSM take the randomness of the initial geometric imperfection and the influence of the high order mode into account.Compared with SIMM,the number of random variables in SIMSM is greatly reduced.The simulation of the random defect of the structure becomes a low dimensional problem.Second step:This thesis proposes a stability capacity computational method based on reliability,and this method not only greatly reduces the number of deterministic finite element calculations,but also ensures high accuracy in the low dimensional problem.The stability capacity of the spherical shell structure can be regarded as a random variable with respect to random defects.In order to ensure the reliability of the single-layer reticulated shell structure,the distribution of random stability capacity is generally required.This method can accurately predict the stability capacity of the single-layer spherical reticulated shell structure in combination with the SIMSM.Finally,by using the proposed stable bearing capacity computational method of single-layer spherical reticulated shell structure with random initial defects,the stability of the single-layer spherical reticulated shell of different parameters with random initial defect has been investigated.Meanwhile,we have drawn some valuable conclusions.