Abstract
Motivated by practical engineering applications, the present study investigates the structural behavior and stability of thin-walled steel cylindrical shells with lateral confinement under two main types of loading, namely external pressure and longitudinal bending, both resulting in structural failure. The present work emphasizes on structural stability in terms of buckling, post-buckling and imperfection sensitivity. The investigation is computational using advanced finite element tools through the employment of a general-purpose finite element program. The cylindrical shells under consideration and the corresponding confinements are simulated with nonlinear finite elements that account for both geometric and material nonlinearities. An extensive literature review on the examined mechanical issues is conducted for the evaluation and assessment of available analytical solutions and experimental data. A numerical simulation methodology is developed and verified in order to model the sh ...
Motivated by practical engineering applications, the present study investigates the structural behavior and stability of thin-walled steel cylindrical shells with lateral confinement under two main types of loading, namely external pressure and longitudinal bending, both resulting in structural failure. The present work emphasizes on structural stability in terms of buckling, post-buckling and imperfection sensitivity. The investigation is computational using advanced finite element tools through the employment of a general-purpose finite element program. The cylindrical shells under consideration and the corresponding confinements are simulated with nonlinear finite elements that account for both geometric and material nonlinearities. An extensive literature review on the examined mechanical issues is conducted for the evaluation and assessment of available analytical solutions and experimental data. A numerical simulation methodology is developed and verified in order to model the shell and the interaction with the confinement. Shells of elastic material are considered first, offering the possibility of comparing the numerical results with available closed-form or simplified analytical predictions. Subsequently, the buckling response of steel shells is examined and the results are compared with available experimental data.For the case of external pressure loading, the numerical results are presented in the form of pressure-deformation equilibrium paths, and show an unstable post-buckling response beyond the point of ultimate pressure capacity, indicating significant imperfection sensitivity on the value of the maximum pressure. The effects of the diameter-to-thickness ratio (D/t), the yield stress, the interface friction, and the medium deformability on the structural response are examined. It is demonstrated that even for rigid confinement medium, the maximum (buckling) pressure is well below the pressure that causes plastification of the entire cylinder (referred to as yield pressure). Finally, based on the numerical results, a simplified and efficient methodology is developed which is compatible with the recent general provisions of European design recommendations for shell buckling, and could be used for design purposes.For the case of longitudinal bending loading of confined cylinders, the analysis refers to the case of the so-called lined pipes, focusing on the behavior of the thin-walled inner pipe (liner) which interacts with the outer pipe. Using a numerical simulation, the stresses and deformations in the compression zone are monitored, with emphasis on possible detachment of the liner from the confining medium, and on the formation of wrinkles. Furthermore, the development of liner ovalization, bending moment, local hoop curvature, axial stress, and hoop stress with increasing level of bending are investigated. The effects of liner thickness, friction, liner prestressing, and stiffness of the confining medium on the buckling curvature and wavelength are examined. The sensitivity of response on the presence of initial wrinkling imperfections is investigated. Finally, the effect of external pressure on the mechanical response is discussed.The present study aims at establishing the theoretical basis for understanding and solving a significant number of structural instabilities related to confined cylindrical shells, which are encountered often in numerous practical engineering applications.
show more
