Sensitivity Analysis For Single-layer Latticed Shell Structure Deformation Based On Reliability Theory

The deformation of shell structure is related to various factors, and the sensitivity of the deformation varies alongside different parameters’change. There are random errors existing in practical engineering applications. The cross-section specifications of elements and the geometric size do not always coincide exactly with the design requirements due to material manufactures and constructional assembly. The influences arisen from these random errors on the structural stiffness are usually difficult to be determined. Based on the principles of reliability and finite element method the deformation sensitivity factors of the single-layer latticed shell structure are investigated and related programs by Matlab are developed.The basic theory and method of sensitivity analysis of structure based on the principles of reliability are-introduced. And combined with the characteristics of latticed shell structure, two programs for analyzing the sensitivity of the deformation of the single-layer latticed shell structure are developed. The first program is based on response surface method (RSM) combined with JC method, the second program is based on response surface method (RSM) combined with sequential quadratic programming (SQP). And the correctness of the programs is verified.Using the first program to analyze a Kiewitt8pattern single-layer spherical latticed shell and a foppl pattern single-layer cylindrical latticed shell, the deformation reliability indices of several geometric factors, such as vector height, wall thickness of members, initial geometric imperfections, elastic modulus and gravity load are obtained and compared. The results show that for Kiewitt8pattern single-layer spherical latticed shell, the wall thickness of members plays significant role with respect to the deformation; and for foppl pattern single-layer cylindrical latticed shell, the initial geometric imperfections play significant role with respect to the deformation. Further more, the sensitivity analyses for both random variables and their statistical characteristics uniformly show that for Kiewitt8pattern single-layer spherical latticed shell, the initial geometric imperfection is more sensitive to the reliability index of deformation than that of the vector height; and for foppl pattern single-layer cylindrical latticed shell, the wall thickness of members is more sensitive to the reliability index of deformation than that of the vector height.Using the second program to analyze the same models again, the results and conclusions obtained by the first program are tested and verified. Also the explanation for the differences has been given.