טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentJabareen Mahmood
SubjectStatic and Dynamic Stability of Imperfect Conical Shell
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Emeritus Izhak Sheinman


Abstract

Loss of stability by buckling in shell-like structures is one of the most important and crucial failure phenomena which may lead to a disaster. The present research deals with the static and dynamic stability of shells to determine the parameters that affect the imperfection sensitivity of the shell. For that purpose, the conical shell was chosen as a representative for the entire range of sensitivity to imperfection: from the extra-sensitive, cylinder, to the completely insensitive, annular plate, where the transition from sensitivity to insensitivity can be followed by varying the cone semi-vertex angle. Shell-like structures is generally characterized by a limit point rather than by a bifurcation point, and the load capacity of such structures is greatly affected by the initial imperfection pattern. With regard to those structures, there are two different main approaches in investigating their behavior: I. investigating the imperfection sensitivity in terms of the initial post buckling behavior. II. tracing of the entire nonlinear equilibrium path with emphasis on the level and direction of change of the stiffness during loading. In the present research, the sensitivity to imperfection and the static stability were investigated in terms of the full nonlinear behavior.

The analytical model was derived by the variational principle, and the solution is separated into Fourier series (circumferential direction) and finite differences (axial direction). The non-linear algebraic equations are solved by the Newton-Raphson procedure and Riks method. The above described solution procedure is implemented in a symbolic code written in MAPLE compiler, whose output is the FORTRAN code.

The results obtained in this study reveal that the cone semi-vertex angle, the imperfection shape and amplitude significantly affect the static and dynamic stability.