Buckling of Ring Stiffened Pontoons of Floating Roofs in Aboveground Oil Storage Tanks

2007 ◽  
Author(s):  
Shoichi Yoshida ◽  
Kazuhiro Kitamura
Keyword(s):  
Large Diameter ◽  
Bending Moment ◽  
Bottom Plate ◽  
Storage Tanks ◽  
Element Analysis ◽  
Linear Elastic ◽  
Structural Problems ◽  
Oil Storage ◽  
Bifurcation Buckling ◽  
Shell Finite Element

The 2003 Tokachi-Oki earthquake caused severe damage to oil storage tanks due to liquid sloshing. Six single-deck floating roofs had experienced structural problems as evidenced by sinking failure in large diameter tanks at the refinery in Tomakomai, Japan. The pontoon of floating roof might be buckled due to circumferential bending moment during the sloshing. The content in the tank was spilled on the floating roof from small failures which might be caused in the lap-welded joints or in the stress concentrated parts of the pontoon bottom plate by the buckling. Then the floating roof began to lose buoyancy and submerged into the content slowly. The failure of the roof expanded gradually in the sinking process. It is presumed that the initial small failures were caused by the elastic buckling of the pontoon due to circumferential bending moment. In this paper, the buckling strength of the pontoon is presented using axisymmetric shell finite element analysis. Linear elastic bifurcation buckling analyses are carried out and the buckling characteristics of ring stiffened pontoons are investigated.

Buckling Characteristics of Floating Roof Pontoons in Aboveground Storage Tanks Subjected to Bending Load in Two Directions

2008 ◽  
Author(s):  
Shoichi Yoshida ◽  
Kazuhiro Kitamura
Keyword(s):  
Large Diameter ◽  
Bending Moment ◽  
Bottom Plate ◽  
Storage Tanks ◽  
Buckling Strength ◽  
Linear Elastic ◽  
Structural Problems ◽  
Oil Storage ◽  
Bending Load ◽  
Shell Finite Element

The 2003 Tokachi-Oki earthquake caused severe damage to aboveground oil storage tanks due to liquid sloshing. Seven single-deck floating roofs had experienced structural problems as evidenced by sinking failure in large diameter tanks at the refinery in Tomakomai, Japan. The pontoons of the floating roofs might be buckled due to circumferential bending moment during the sloshing. The content in the tank was spilled on the floating roof from small failures which were caused at the welding joints of pontoon bottom plate by the buckling. Then the floating roof began to lose buoyancy and submerged into the content slowly. The authors had reported the buckling strength of the pontoons with and without ring stiffeners subjected to circumferential bending load in the previous papers. This paper presents the buckling strength of the pontoons subjected to both circumferential and radial bending load. The axisymmetric shell finite element method is used in the analysis. Linear elastic bifurcation buckling analysis is carried out and the buckling characteristics of the pontoon with and without ring stiffeners are investigated.

Buckling of Single-Deck Floating Roofs in Aboveground Oil Storage Tanks Due to Circumferential Bending Load

2006 ◽  
Author(s):  
Shoichi Yoshida ◽  
Kazuhiro Kitamura
Keyword(s):  
Large Diameter ◽  
Bending Moment ◽  
Bottom Plate ◽  
Storage Tanks ◽  
Element Analysis ◽  
Buckling Strength ◽  
Structural Problems ◽  
Oil Storage ◽  
Bending Load ◽  
Shell Finite Element

The 2003 Tokachi-Oki earthquake caused severe damage to oil storage tanks due to liquid sloshing. Six single-deck floating roofs had experienced structural problems as evidenced by sinking failure in large diameter tanks at the refinery at Tomakomai, Japan. The pontoon of floating roof might be buckled due to circumferential bending moment during the sloshing. The content in the tank was spilled on the floating roof from small failures which were caused in the rap welding joints of pontoon bottom plate by the buckling. Then the floating roof began to lose buoyancy and submerged into the content slowly. The failure of the roof expanded gradually in the sinking process. It is presumed that the initial small failures were caused by the elastic buckling of the pontoon due to circumferential bending moment. This paper presents the buckling strength of the pontoon using axisymmetric shell finite element analysis. Linear elastic bifurcation buckling analysis is carried out and the buckling characteristics of the pontoon are investigated. The result shows that the thickness of both pontoon roof and bottom plates have significantly affect the buckling strength.

Buckling Characteristics of Floating Roof Pontoons in Aboveground Storage Tanks Subjected to Both Compressive and Bending Load

2009 ◽  
Author(s):  
Shoichi Yoshida
Keyword(s):  
Large Diameter ◽  
Compressive Load ◽  
Bending Moment ◽  
Bottom Plate ◽  
Storage Tanks ◽  
Buckling Strength ◽  
Structural Problems ◽  
Oil Storage ◽  
Bending Load ◽  
Shell Finite Element

The 2003 Tokachi-Oki earthquake caused severe damage to oil storage tanks due to liquid sloshing. Seven single-deck floating roofs had experienced structural problems as evidenced by sinking failure in large diameter tanks at a refinery in Tomakomai, Japan. The pontoons of the floating roofs might be buckled due to circumferential bending moment during the sloshing. The content in the tank was spilled on the floating roof from small failures which were caused in the welding joints of pontoon bottom plate by the buckling. Then the floating roof began to lose buoyancy and sank into the content slowly. The authors had reported the buckling strength of the pontoons subjected to circumferential bending load first and that of the pontoons subjected to both circumferential and radial bending load next in the previous papers. This paper presents the buckling strength of the pontoons subjected to both circumferential bending load and circumferential compressive load. The axisymmetric shell finite element method is used in the analysis. Linear elastic bifurcation buckling analysis is carried out and the buckling characteristics of the pontoon both with and without ring stiffeners are investigated.

Lower Bound Buckling Load of a Floating Roof Pontoon

2010 ◽  
Author(s):  
Shoichi Yoshida
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Large Diameter ◽  
Buckling Load ◽  
Bottom Plate ◽  
Element Analysis ◽  
Oil Storage ◽  
Bending Load ◽  
Stiffness Method ◽  
Shell Finite Element

The 2003 Tokachi-Oki earthquake caused severe damage to oil storage tanks due to liquid sloshing. Seven single-deck floating roofs had experienced sinking failures in large diameter tanks at a refinery in Tomakomai, Japan. The pontoons of the floating roofs might be buckled due to bending load during the sloshing. The content in the tank was spilled on the floating roof from small failures which were caused in the welding joints of pontoon bottom plate by the buckling. Then the floating roof began to lose buoyancy and sank into the content slowly. The elastic buckling of the pontoon is important from the viewpoint of the single-deck floating roof sinking. The authors had reported the buckling strength of the pontoons subjected to bending and compressive loads in the published literatures. The axisymmetric shell finite element method for linear elastic bifurcation buckling was used in the analysis. The buckling characteristics of the pontoon both with and without ring stiffeners were investigated. The initial geometrical imperfection may diminish the buckling load. This paper presents the lower bound buckling load according to the reduced stiffness method proposed by Croll and Yamada. The lower bound buckling loads of the pontoon subjected to circumferential bending load are evaluated from the axisymmetric finite element analysis which includes the reduced stiffness method.

Sloshing Characteristics of Single Deck Floating Roofs in Aboveground Storage Tanks: Natural Periods and Vibration Modes

2009 ◽  
Author(s):  
Shoichi Yoshida ◽  
Kazuyoshi Sekine ◽  
Katsuki Iwata
Keyword(s):  
Structural Integrity ◽  
Oil Refining ◽  
Vibration Modes ◽  
Storage Tanks ◽  
Severe Damage ◽  
Element Analysis ◽  
Linear Elastic ◽  
Oil Storage ◽  
Hydrodynamic Coupling ◽  
Roof Design

The floating roofs are widely used to prevent evaporation of content in large oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. The structural integrity of the floating roofs for the sloshing is urgent issue to establish in the petrochemical and oil refining industries. This paper presents the sloshing characteristics of the single deck floating roofs in cylindrical storage tanks. The hydrodynamic coupling of fluid and floating roof is taken into consideration in the axisymmetric finite element analysis. It is assumed that the fluid is incompressible and inviscid, and the floating roof is linear elastic while the sidewall and the bottom are rigid. The basic vibration characteristics, natural periods and vibration modes, of the floating roof due to the sloshing are investigated. These will give engineers important information on the floating roof design.

Behavior of Localized Bottom Bulge in Aboveground Oil Storage Tanks Under Liquid Pressure

2001 ◽  
Vol 124 (1) ◽  
pp. 59-65
Author(s):  
Shoichi Yoshida
Keyword(s):  
Plastic Strain ◽  
Plate Thickness ◽  
Deformation Analysis ◽  
Bottom Plate ◽  
Storage Tanks ◽  
Liquid Pressure ◽  
Element Analysis ◽  
Oil Storage ◽  
Relationship Of ◽  
The Relationship

The bottom plate of aboveground oil storage tanks can bulge, separating from the foundation due to welding deformation. When such a bulge is subjected to liquid pressure, it deforms continuously to make contact with the foundation from the edge, and the remaining area of the bulge decreases with increasing liquid pressure. As a result, the deformation is extremely localized and plastic strain occurs at the bulge. This paper presents a plane strain finite element analysis for the evaluation of localized bottom bulges in aboveground oil storage tanks. Load-incremental, elastic-plastic large deformation analysis is carried out considering the bottom plate contact with the foundation. The relationship of the plastic strain at the bulged bottom plate to the liquid pressure is discussed together with the deformation of the bulge. As a result, the bottom plate thickness has a significant effect on the deformation, but the bulged height does not. After the bulged center makes contact with the foundation, the stress and strain do not increase with increasing liquid pressure. In addition, the permissible bulged profile specified by API Standard 653 elastically deforms to make contact with the foundation under low liquid pressure.

Behavior of Localized Bottom Depression in Aboveground Oil Storage Tanks Under Liquid Pressure

2004 ◽  
Author(s):  
Shoichi Yoshida
Keyword(s):  
Finite Element Analysis ◽  
Deformation Analysis ◽  
Bottom Plate ◽  
Storage Tanks ◽  
Liquid Pressure ◽  
Element Analysis ◽  
Large Deformation Analysis ◽  
Oil Storage ◽  
Relationship Of ◽  
The Relationship

When constructing the bottom of aboveground oil storage tanks, the bottom plates are first laid out on the flat foundation, and they then are joined by welding the joints in sequence. As the foundation is difficult to be made completely homogeneous over the bottom area, the settlement of the bottom plates is not uniform under liquid pressure. The depressions of the bottom plates are sometimes found at the first internal inspection which is usually made about 10 years after the oil storage. This paper presents plane strain finite element analysis for the localized bottom depression in aboveground oil storage tanks. Load-incremental, elastic-plastic large deformation analysis is carried out considering contact with the foundation. The relationship of the stress at the depressed bottom plate to the liquid pressure is discussed together with the deformation of the depression.

The linear elastic in-plane bending of curved hollow profiles having a thin-walled rectangular section

1992 ◽  
Vol 27 (3) ◽  
pp. 145-149 ◽  
Author(s):  
F J M Q De Melo ◽  
M A P Vaz
Keyword(s):  
Cross Section ◽  
Thin Shell ◽  
Transverse Section ◽  
Accurate Solution ◽  
Rectangular Section ◽  
Element Analysis ◽  
Linear Elastic ◽  
Graphical Result ◽  
Thin Walled ◽  
Shell Finite Element

This paper presents a simple solution for the flexibility calculation of curved profiles having a rectangular thin-walled cross-section. Some assumptions related to geometric details about the shape of the deformed structure are included in the present analysis, aiming at an economic and accurate solution. Results concerning the distortion of the transverse section are compared with the corresponding data from the solution with a thin shell finite element analysis. A flexibility factor for the structure analysed here is presented as a graphical result.

Deformation in Multilayer Stacked Assemblies

1990 ◽  
Vol 112 (1) ◽  
pp. 30-34 ◽  
Author(s):  
Tsung-Yu Pan ◽  
Yi-Hsin Pao
Keyword(s):  
Thermal Loading ◽  
Bending Moment ◽  
Radius Of Curvature ◽  
Element Analysis ◽  
First Order ◽  
Strain Behavior ◽  
Linear Elastic ◽  
Nonlinear Stress ◽  
Order Polynomial ◽  
Vertical Displacements

A linear-elastic analytical model has been developed to describe the deformed geometry of a multi-layered stack assembly subject to thermal loading. The model is based on Timoshenko’s bimetal thermostat analysis [1] and consists of a series of first-order polynomial equations. The radius of curvature, bending moment, force, horizontal and vertical displacements can be determined numerically. These quantities match well with finite element analysis. Calculations for silicon power transistor stacks are presented in order to demonstrate the model capability. The results from this analyitcal model have been found to correlate well with experimental measurements when an appropriate secant modulus is used to represent the nonlinear stress-strain behavior of solder.

Axisymmetric Finite Element Analysis for Floating Roofs of Aboveground Storage Tanks Under Accumulated Rain Water Condition

2011 ◽  
Author(s):  
Shoichi Yoshida
Keyword(s):  
Finite Element ◽  
Load Condition ◽  
Rain Water ◽  
Water Volume ◽  
Deformation Analysis ◽  
Storage Tanks ◽  
Element Analysis ◽  
Water Condition ◽  
Incremental Method ◽  
Shell Finite Element

The floating roofs are used in large aboveground storage tanks to prevent evaporation of the content. The single-deck floating roof, which is considered herein, consists of a thin circular plate called a deck attached to a buoyant ring of box-shaped cross section called a pontoon. Under the accumulated rain water condition, the deck is deflected largely, and both its edge part and the pontoon are compressed circumferentially. Since the load condition due to the rain water depends on the deflected deck shape, it is difficult to find the unique equilibrium condition. This paper describes the deformation analysis for the single-deck floating roofs under the accumulated rain water condition using the geometrically nonlinear axisymmetric shell finite element method. The load incremental method, in which the equivalent nodal forces due to the rain water converges to coincide with the rain water load derived from both the current rain water volume and the deflected deck shape, is used.

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