Riser Stability Under External Pressure and Axial Compression Observing Geometrical Imperfections

2005 ◽  
Author(s):  
He´ctor A. Sa´nchez Sa´nchez ◽  
Carlos Corte´s Salas
Keyword(s):  
Axial Compression ◽  
Critical Pressure ◽  
External Pressure ◽  
Theoretical Methods ◽  
Steel Pipes ◽  
Geometrical Imperfections ◽  
Critical External Pressure ◽  
Empty Condition ◽  
Theoretical Results ◽  
Numerical Approaches

Steel pipes are studied considering external pressure, axial compression and bending actions to empty condition, taking into account the initial geometrical imperfections. The main objective is to study the behavior and structural stability of these pipes submitted to combine loads, considering the influence of the geometrical imperfections and to estimate the critical external pressure. Critical pressure of buckling, and modal configurations are evaluated by theoretical methods and numerical approaches such as finite element method (FEM). The numerical results are compared with theoretical results.

Buckling of Circular Cylindrical Shells Using a Displacement Function

1974 ◽  
Vol 96 (4) ◽  
pp. 1322-1327
Author(s):  
Shun Cheng ◽  
C. K. Chang
Keyword(s):  
Boundary Conditions ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
External Pressure ◽  
Displacement Function ◽  
Combined Loading ◽  
Trial Solution ◽  
Governing Differential Equation ◽  
Circular Cylindrical Shells ◽  
The Stability

The buckling problem of circular cylindrical shells under axial compression, external pressure, and torsion is investigated using a displacement function φ. A governing differential equation for the stability of thin cylindrical shells under combined loading of axial compression, external pressure, and torsion is derived. A method for the solutions of this equation is also presented. The advantage in using the present equation over the customary three differential equations for displacements is that only one trial solution is needed in solving the buckling problems as shown in the paper. Four possible combinations of boundary conditions for a simply supported edge are treated. The case of a cylinder under axial compression is carried out in detail. For two types of simple supported boundary conditions, SS1 and SS2, the minimum critical axial buckling stress is found to be 43.5 percent of the well-known classical value Eh/R3(1−ν2) against the 50 percent of the classical value presently known.

Effet des imperfections géométriques sur la stabilité des coques élastiques cylindriques

2004 ◽  
Vol 31 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Abdellatif Khamlichi ◽  
Mohammed Bezzazi ◽  
Larbi Elbakkali ◽  
Ali Limam
Keyword(s):  
Critical Load ◽  
Axial Symmetry ◽  
A Priori ◽  
Severe Case ◽  
Thin Shells ◽  
Geometrical Imperfections ◽  
Localized Defects ◽  
Shell Equations ◽  
Selection Of ◽  
Numerical Approaches

The effects of geometrical imperfections on the critical load of elastic cylindrical shells when subjected to axial compression are studied through analytical modelling. In addition to distributed defects of both axisymmetric or asymmetric forms, emphasis is put on the more severe case of localized defects satisfying the axial symmetry. The Von Kármán – Donnell shell equations were used. The obtained results show that shell strength at buckling varies very much with the defect amplitude. These variations are not monotonic in general. They indicate however a clear reduction of the shell critical load for some defects revealed as the most dangerous ones. The proposed method does not consider the complete coupled situation that may arise from interactions between several localized defects. It facilitates nevertheless straightforward initializing of closer analyses if such couplings are to be taken into account by means of special numerical approaches, because it enables fast a priori selection of the most hazardous isolated defects.Key words: stability, buckling, imperfections, thin shells, silos, localized defects.

Bemessung von beulgefährdeten Druckschachtpanzerungen unter Außendruck – Teil 1: Unversteifte Stahlrohre/Buckling design of steel liners under external pressure – part 1: unstiffened steel pipes

Bauingenieur ◽  
2019 ◽  
Vol 94 (10) ◽  
pp. 366-377
Author(s):  
Harald Unterweger ◽  
Alexander Ecker
Keyword(s):  
External Pressure ◽  
Steel Pipes ◽  
Pressure Part

Zusammenfassung Bei der statisch konstruktiven Auslegung der stählernen Druckschachtpanzerungen von Triebwasserwegen wird mitunter nicht die Innendruckbelastung maßgebend, sondern die Außendruckbelastung infolge Bergwasserdruck. Dieser führt im Revisionsfall bei entleerter Druckrohrleitung zu einer hohen Beulgefährdung, bedingt durch die ausgeführten großen Rohrschlankheiten. Die Bemessungsregeln in der Praxis basieren auf analytischen und empirischen Modellen, die im Wesentlichen bereits in den 1960er-Jahren entwickelt wurden. Dieser Beitrag fasst die Gesamtergebnisse eines Forschungsprojektes zusammen, dass das Ziel hatte durch nun verfügbare realitätsnahe numerische Modelle zusätzliche Effekte, wie verschiedene Imperfektionsformen, auftretende Längsdruckkräfte im Rohr infolge Reibschluss sowie die radiale Gebirgsnachgiebigkeit, mit zu berücksichtigen. Teil 1 beinhaltet die Ergebnisse für unversteifte Stahlrohre. Es werden einleitend die in der Praxis üblichen Bemessungsmodelle zur Ermittlung der kritischen Außendruckbelastung p0,cr erläutert und hinsichtlich ihrer Ergebnisse miteinander verglichen. Aus dem zusätzlichen Vergleich mit den numerischen Berechnungsergebnissen wird das zutreffendste Bemessungsmodell für die Praxis dargestellt und auch in Form von Bemessungsdiagrammen aufbereitet.

Nonlinear Stability Analysis of the Vaulted Roofs With Corrosion Defects of Oil Storage Tank

2009 ◽  
Author(s):  
Baosheng Dong ◽  
Xinwei Zhao ◽  
Hongda Chen ◽  
Jinheng Luo ◽  
Zhixin Chen ◽  
...  
Keyword(s):  
Spherical Shell ◽  
Nonlinear Stability ◽  
Storage Tank ◽  
Critical Pressure ◽  
External Pressure ◽  
Shallow Spherical Shell ◽  
Nonlinear Stability Analysis ◽  
Spherical Shells ◽  
Oil Storage ◽  
Oil Storage Tank

The vaulted roofs of oil storage tank are usually designed as the shallow spherical shells subjecting to a uniform external pressure, which have been widely observed that these shallow spherical shells undergo various levels of corrosion in their employing conditions. It is important to assess the stability of these local weaken shallow spherical roofs due to corrosion for preventing them from occurring unexpected buckling failure. In this paper, the uniform eroded part of a shallow spherical oil tank vaulted roof is simplified as a shallow spherical shell with elastic supports. Based on the simplification, a general pathway to calculate the critical pressure of eroded shallow spherical shell is proposed. The modified iteration method considering large deflection of the shell is applied to solve the problem of nonlinear stability of the shallow spherical shells, and then the second-order approximate analytical solution is obtained. The critical pressure calculated by this method is consistent with the classical numerical results and nonlinear finite element method, and the calculation errors are less than 10%. It shows that it is feasible to apply the method proposed here.

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