Buckling Behavior of Elliptical Shells of Changing Thickness under Uniform Axial Compression

2013 ◽  
Vol 351-352 ◽  
pp. 492-496 ◽  
Author(s):  
Li Wan ◽  
Lei Chen
Keyword(s):  
Axial Compression ◽  
Cylindrical Shells ◽  
Imperfection Sensitivity ◽  
Buckling Mode ◽  
Buckling Strength ◽  
Shell Buckling ◽  
Buckling Behavior ◽  
Structural Applications ◽  
Post Buckling ◽  
Shell Geometry

Many elliptical shells are used in structural applications in which the dominant loading condition is axial compression. Due to the fact that the radius varies along the cross-section midline, the buckling behavior is more difficult to identify than those of cylindrical shells. The general concerned aspects in cylindrical shell buckling analyses such as the buckling mode, the pre-buckling deformation and post-buckling deformation are all quite different related to specific elliptical shell geometry. The buckling behavior of elliptical cylindrical shells with uniform thickness has been widely studied by many researchers. However, the thickness around the circumference may change for some specific structural forms, the femoral neck for example, which makes the buckling behavior more complex. It is known that the buckling strength of thin cylindrical shells is quite sensitive to imperfections, so it is natural to explore the imperfection sensitivity of elliptical shells. This paper explores the buckling behavior of imperfect elliptical shells under axial compression. It is hoped that the results will make a useful contribution in this field.

Nonlinear Buckling Behaviour of Imperfect Cylindrical Shells under Global Bending in the Elastic-Plastic Range

2012 ◽  
Vol 204-208 ◽  
pp. 1045-1052
Author(s):  
Lei Chen ◽  
Yi Liang Peng ◽  
Li Wan
Keyword(s):  
Cylindrical Shells ◽  
Plastic State ◽  
Plastic Range ◽  
Nonlinear Buckling ◽  
Buckling Strength ◽  
Elastic Plastic ◽  
Capacity Curves ◽  
Shell Buckling ◽  
Buckling Behavior ◽  
Structural Applications

Many thin cylindrical shells are used in structural applications in which the dominant loading condition is global bending. Key examples include chimneys, tubular piles, wind generation towers and tall silos. Their thickness lies in a tricky range which is extremely thin for the structural tube community and very thick for the shell buckling community. The buckling strength of these structures is dominated by extensive plasticity, but the fully plastic state is usually far from being attained. This paper explores the buckling strength of imperfect thin cylindrical shells under global bending in the elastic-plastic range. The capacity curves of the new Eurocode EN 1993-1-6 (2007) are used to match the final results. The results show that the capacity curves can capture this buckling behavior accurately and safely for different types of material models. It is assumed that the shell is held circular by rings or boundaries at reasonable intervals, effectively restraining ovalisation. It is hoped that these results will make a useful contribution towards resolving the misunderstandings and controversy that has been evident in this field in recent years.

Post-buckling Behavior of Stiffened Cross-Ply Cylindrical Shells

1994 ◽  
Vol 61 (4) ◽  
pp. 998-1000 ◽  
Author(s):  
M. Savoia ◽  
J. N. Reddy
Keyword(s):  
Axial Compression ◽  
Carrying Capacity ◽  
Shell Theory ◽  
Load Carrying Capacity ◽  
Imperfection Sensitivity ◽  
Buckling Modes ◽  
Geometric Imperfection ◽  
Buckling Behavior ◽  
Load Carrying ◽  
Post Buckling

The post-buckling of stiffened, cross-ply laminated, circular determine the effects of shell lamination scheme and stiffeners on the reduced load-carrying capacity. The effect of geometric imperfection is also included. The analysis is based on the layerwise shell theory of Reddy, and the “smeared stiffener” technique is used to account for the stiffener stiffness. Nu cylinders under uniform axial compression is investigated to merical results for stiffened and unstiffened cylinders are presented, showing that imperfection-sensitivity is strictly related to the number of nearly simultaneous buckling modes.

Background of ABS Buckling Strength Assessment Criteria for Cylindrical Shells in Offshore Structures

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Hai-Hong Sun ◽  
Pao-Lin Tan
Keyword(s):  
Cylindrical Shells ◽  
Experimental Studies ◽  
Theoretical Work ◽  
Offshore Structures ◽  
Assessment Criteria ◽  
Test Results ◽  
Strength Assessment ◽  
Buckling Strength ◽  
Shell Buckling ◽  
Buckling Behavior

Cylindrical shells, unstiffened or stiffened with rings and/or stringers, are commonly used in offshore structures as main loading-carrying members. Comprehensive theoretical work and experimental studies on the buckling behavior of cylindrical shells have been carried out in the past. The increasing offshore application of stiffened cylindrical shells has raised some new challenges that need to be addressed. This paper provides the fundamental principles and technical background of the ABS buckling strength assessment criteria for cylindrical shells applied in offshore structures. The accuracy of ABS buckling criteria for assessing the cylindrical shells is established by benchmarking the results against an extensive database of test results assembled by American Bureau of Shipping. The results are also compared against current recognized offshore standards, such as API Bulletins 2U and DnV CN30.1. It is demonstrated that the ABS criteria provide very effective and sufficiently accurate predictions for the cylindrical shell buckling calculations.

Koiter-Based Solution for the Initial Post-buckling Behavior of Moderately Thick Orthotropic and Shear Deformable Cylindrical Shells Under External Pressure

1997 ◽  
Vol 64 (4) ◽  
pp. 885-896 ◽  
Author(s):  
G. A. Kardomateas
Keyword(s):  
Cylindrical Shells ◽  
Shear Deformation Theory ◽  
External Pressure ◽  
Isotropic Case ◽  
Imperfection Sensitivity ◽  
Buckling Behavior ◽  
Load Carrying ◽  
Geometrical Imperfections ◽  
Post Buckling ◽  
Shear Deformable

The initial post-buckling behavior of moderately thick orthotropic shear deformable cylindrical shells under external pressure is studied by means of Koiter’s general post-buckling theory. To this extent, the objective is the calculation of imperfection sensitivity by relating to the initial post-buckling behavior of the perfect structure, since it is generally recognized that the presence of small geometrical imperfections in some structures can lead to significant reductions in their buckling strengths. A shear deformation theory, which accounts for transverse shear strains and rotations about the normal to the shell midsurface, is employed to formulate the shell equations. The initial post-buckling analysis indicates that for several combinations and geometric dimensions, the shell under external pressure will be sensitive to small geometrical imperfections and may buckle at loads well below the bifurcation predictions for the perfect shell. On the other hand, there are extensive ranges of geometrical dimensions for which the shell is insensitive to imperfections, and, therefore it would exhibit stable post-critical behavior and have a load-carrying capacity beyond the bifurcation point. The range of imperfection sensitivity depends strongly on the material anisotropy, and also on the shell thickness and whether the end pressure loading is included or not. For example, for the circumferentially reinforced graphite/epoxy example case studied, it was found that the structure is not sensitive to imperfections for values of the Batdorf length parameter z˜ above ≃270, whereas for the axially reinforced case the structure is imperfection-sensitive even at the high range of length values; for the isotropic case, the structure is not sensitive to imperfections above z˜ ≃ 1000.

Imperfection Sensitivity of Laminated Cylindrical Shells by Full and Initial Post-Buckling Analyses

Aerospace ◽  
2004 ◽  
Author(s):  
Izhak Sheinman ◽  
Mahmood Jabareen
Keyword(s):  
Structural Engineering ◽  
Cylindrical Shells ◽  
Nonlinear Behavior ◽  
Test Results ◽  
Imperfection Sensitivity ◽  
Buckling Behavior ◽  
Load Carrying ◽  
Post Buckling ◽  
Linear Buckling Analysis ◽  
Laminated Cylindrical Shells

Laminated cylindrical shells are already commonly used in structural engineering, and their buckling and post-buckling behavior is of vital importance in the design of such structures. The validity of linear buckling analysis in this context, has been questioned because of the discrepancy observed between theoretical prediction and test results. The cause of this discrepancy is the fact that the nonlinear behavior of shell-like structures is generally characterized by a limit point rather than by a bifurcation point. For such structures, the load-carrying capacity depends on the level of imperfection (hence the concept “imperfection sensitivity”). The motivation is, therefore, to reduce the sensitivity rather than preventing the imperfection. For that purpose insight into the post-buckling state is called for.

Background of ABS Buckling Strength Assessment Criteria for Cylindrical Shells in Offshore Structures

2006 ◽  
Author(s):  
Hai-Hong Sun ◽  
Pao-Lin Tan
Keyword(s):  
Cylindrical Shells ◽  
Experimental Studies ◽  
Theoretical Work ◽  
Offshore Structures ◽  
Assessment Criteria ◽  
Test Results ◽  
Strength Assessment ◽  
Buckling Strength ◽  
Shell Buckling ◽  
Buckling Behavior

Cylindrical shells, unstiffened or stiffened with rings and/or stringers are commonly used in offshore structures as main loading-carrying members. Comprehensive theoretical work and experimental studies on the buckling behavior of cylindrical shells have been carried out in the past. The increasing offshore application of stiffened cylindrical shells has raised some new challenges that need to be addressed. This paper provides the fundamental principles and technical background of the ABS buckling strength assessment criteria for cylindrical shells applied in offshore structures. The accuracy of ABS buckling criteria for assessing the cylindrical shells is established by benchmarking the results against an extensive database of test results assembled by American Bureau of Shipping. The results are also compared against current recognized offshore standards, such as API Bulletins 2U and DnV CN30.1. It is demonstrated that the ABS criteria provide very effective and sufficiently accurate predictions for the cylindrical shell buckling calculations.

Delamination Suppression in Sandwich Beams Using Translaminar Reinforcements

1999 ◽  
Author(s):  
Brian T. Wallace ◽  
Bhavani V. Sankar ◽  
Peter G. Ifju
Keyword(s):  
Axial Compression ◽  
Sandwich Beam ◽  
Sandwich Beams ◽  
Thickness Direction ◽  
Compression Tests ◽  
Honeycomb Core ◽  
Element Analysis ◽  
Buckling Loads ◽  
Buckling Behavior ◽  
Post Buckling

Abstract The present study is concerned with translaminar reinforcement in a sandwich beam for preventing buckling of a delaminated face-sheet under axial compression. Graphite/epoxy pins are used as reinforcement in the thickness direction of sandwich beams consisting of graphite/epoxy face-sheets and a Aramid honeycomb core. Compression tests are performed to understand the effects of the diameter of the reinforcing pins and reinforcement spacing on the ultimate compressive strength of the delaminated beams. A finite element analysis is performed to understand the effects of translaminar reinforcement on the critical buckling loads and post-buckling behavior of the sandwich beam under axial compression.

Towards imperfection insensitive buckling response of shell structures-shells with plate-like post-buckled responses

2016 ◽  
Vol 120 (1224) ◽  
pp. 233-253 ◽  
Author(s):  
S. C. White ◽  
P. M. Weaver
Keyword(s):  
Variable Stiffness ◽  
Axial Stiffness ◽  
Asymptotic Model ◽  
Imperfection Sensitivity ◽  
Asymptotic Results ◽  
Buckling Mode ◽  
Design Variables ◽  
Non Linear ◽  
Buckling Stability ◽  
Post Buckling

ABSTRACTThe imperfection sensitivity of cylindrical panels under compression loading is shown to be not only reduced but effectively eliminated using stiffness tailoring techniques. Shells are designed with variable angle-tow (VAT) laminae, giving their laminates variable-stiffness properties over the surface co-ordinates. By employing an asymptotic model of the non-linear shell behaviour and a genetic algorithm, the post-buckling stability was maximised with respect to the VAT design variables. Results for optimised straight-fibre and VAT shells are presented in comparison with quasi-isotropic designs. In the straight-fibre case, small improvements in the post-buckling stability are shown to be possible but at the expense of the buckling load. In the VAT case, on the other hand, considerable improvements in the post-buckling stability are obtained and drops in axial stiffness and load associated with buckling are reduced to negligible levels. The improvements are shown to be a result of a benign membrane stress distribution prior to buckling and a localisation of the buckling mode. The asymptotic results are compared with non-linear finite-element analyses and are found to be in good agreement. Potential future multi-objective optimisation studies are discussed.

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