Structural stability and reliability of cylindrical shells under axial compression based on random field of geometric imperfections

• Applicant: Dr.-Ing. Zheng Li
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454652824

Silo structure is usually constructed in the form of a cylindrical steel shell. It has the advantages of being lightweight, having a short construction period, and possessing a large storage space. However, due to the strong sensitivity of the cylindrical thin-walled structures, the initial geometric imperfections of the silos must also be considered within the nonlinear analysis. The geometric imperfections of cylindrical shells used in steel structures are randomly distributed and unknown. The "worst" form of imperfection used in actual structural design cannot accurately describe and quantify real geometric imperfections. This may cause safety problems and eventually lead to the collapse of shell structures. This paper proposes a calculation approach for buckling loads of cylindrical shells that can consider the randomness of initial geometric imperfections and describe long-standing differences between theoretical analysis and test results. The research objectives are addressed through the following tasks: 1) a random field of initial geometric imperfections is established based on experimental measurements and theoretical analysis; 2) statistical results of the buckling bearing capacity of the cylindrical shell are obtained using the stochastic finite element method and verified using experimental results; 3) an optimal distribution function of the buckling bearing capacity is fitted based on the maximum entropy principle; and 4) the knock-down factor of the shell bearing capacity is modified based on a structural reliability analysis. First, the real specimen dimensions of the cylindrical shells are obtained through three dimensional laser scanning technology. Then, the randomness of geometric imperfections and the spatial correlation relationship are analysed based on statistical theory. The statistical characteristics of shell buckling bearing capacity are investigated using quasi-static axial compression tests. Finally, parameter studies are conducted using validated numerical methods. It is anticipated that the outcomes of this study will further improve the safety of shell structures and have important scientific and engineering significance.

• DFG Programme: Research Grants