(A) study on the buckling strength of cylindrical shells with various initial imperfections subjected to axial compression

다국어 초록 (Multilingual Abstract)

Thin-walled cylindrical structure under compression should always be checked for stability against buckling, which is one of the primary design considerations in structural engineering. The study and analysis of the initial imperfection, which has the most sensitive effect on the buckling strength, has been continuously studied by many researchers. However, the influence of the initial imperfection has been considered based on the empirical results through the cylindrical shell buckling test. There is still a significant difference between the predicted buckling strength and the buckling strength obtained through experiments.
Eurocode provides a generalized buckling capacity curve that can predict the buckling strength of cylindrical shells. The buckling capacity curve conservatively evaluates the elastic buckling strength when the amplitude of the imperfection is small and does not accurately track the change in the elastic buckling behavior depending on the imperfection. On the other hand, when the amplitude of the imperfection is large, the plastic strength is overestimated.
In this study, the cylindrical buckling strength with various amplitudes of geometric imperfections was evaluated by performing geometric and material nonlinear structural analysis. Through this, the key factors of the buckling capability curve are newly proposed as a function of the geometric imperfection. By applying the newly proposed factor, it is possible to more accurately evaluate the lower-boundary buckling strength of the cylindrical shell, which can cover the effects of various imperfections, and to track the change in buckling behavior according to imperfections.

목차 (Table of Contents)

• Chapter 1 Introduction 1
• Chapter 2 Background & Objective 3
• 2.1 Equilibrium equation for buckling of cylindrical shells 3
• 2.2 Imperfection sensitivity 9
• 2.3 Comparison of various cylindrical buckling evaluations 11
• 2.3.1 Empirical knockdown factors 11
• 2.3.2 The design buckling capacity curve 13
• 2.3.3 Linear buckling mode-shaped imperfection 17
• 2.3.4 Realistic measured geometric imperfecions 17
• 2.3.5 Summary 18
• 2.4 Design criteria (EN 1993-1-6) 19
• 2.4.1 Types of analysis 19
• 2.4.2 Buckling capacity curve 20
• 2.5 Research objective 25
• 2.5.1 Idea 25
• 2.5.2 Objectives & scope 28
• Chapter 3 Structural Analysis 29
• 3.1 Analysis model scheme 29
• 3.1.1 Material properties 30
• 3.1.2 Boundary & loading condition 31
• 3.2 Preliminary analysis 33
• 3.2.1 Cylinder length effects with imperfections 33
• 3.2.2 Classification criteria for short and long length cylinders 44
• 3.3 Linear bifurcation analysis (LBA) 48
• 3.4 Geometrically and materially nonlinear analysis with imperfections 51
• 3.4.1 Considered parameters 51
• 3.4.2 Load-displacement curve 53
• 3.4.3 Buckling capacity curve 65
• Chapter 4 Modified Design Factors 67
• 4.1 Modified buckling capacity curve 67
• 4.2 Elastic imperfection reduction factor 71
• 4.3 Plastic range factor 77
• 4.4 Geometric nonlinearity factor 84
• 4.5 Application and verification 96
• 4.5.1 Comparison of the proposed three factor application 96
• 4.5.2 Verification of the proposed three factor application 99
• Chapter 5 Conclusion 101
• Reference 103

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