Stability of Open Top Cylindrical Steel Storage Tanks: Design of Top Wind Girder

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
E. Azzuni ◽  
S. Guzey
Keyword(s):  
Design Methodology ◽  
Geometrically Nonlinear ◽  
Storage Tanks ◽  
Element Analysis ◽  
Geometrically Nonlinear Analysis ◽  
Buckling Loads ◽  
Upper Limit ◽  
Current Design ◽  
Cylindrical Steel ◽  
Different Diameters

Design of the top wind stiffeners of aboveground storage tanks designed to the requirements of API 650 is investigated. The current design methodology is based on intuition and experience without a sound technical justification. This paper investigates a diameter limit to be used in the design of the top stiffener ring by using finite-element analysis (FEA) in a parametric study. Linear bifurcation analysis (LBA) and geometrically nonlinear analysis including imperfections (GNIA) were performed on cylindrical storage tanks. By modeling tanks with different diameters and limiting the design of top stiffener ring for a diameter of 170-ft (52-m), the buckling loads are investigated. It was found that the 170-ft (52-m) diameter is a suitable upper limit to design the top stiffener rings for larger diameters.

Stability of Open-Topped Storage Tanks With Top Stiffener and One Intermediate Stiffener Subject to Wind Loading

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Tianlong Sun ◽  
Eyas Azzuni ◽  
Sukru Guzey
Keyword(s):  
Wind Loading ◽  
Geometrically Nonlinear ◽  
Storage Tanks ◽  
Element Analysis ◽  
Design Rules ◽  
Geometrically Nonlinear Analysis ◽  
Buckling Modes ◽  
Intermediate Stiffener ◽  
Wind Profiles ◽  
Design Pressure

Aboveground vertical steel storage tanks use stiffener rings to prevent their shell wall from buckling under wind loading. The existing stiffener rings design rules from API 650 standard is known to be overly conservative. This study investigates the possibility of modifying the design rules by reducing the required size of the top stiffener ring to the same size as the intermediate stiffener ring. In this study, we used finite element analysis (FEA) to perform linear bifurcation analysis (LBA) and geometrically nonlinear analysis including imperfections (GNIA) to obtain failure load of modeled tanks. The buckling pressure load was obtained to ensure it is larger than the design pressure. Moreover, the effects of higher strength materials, different buckling modes, and various wind profiles were also studied to ensure the design suggested by this study is practical and universal to different situations. The results show that for cylindrical storage tanks, which only needs one intermediate stiffener ring, the size of the top stiffener ring can be set to the same size as the intermediate stiffener ring.

scholarly journals Comparison between exact and approximate methods for geometrically nonlinear analysis prescribed in design standards for steel and reinforced concrete structures

2022 ◽  
Vol 15 (1) ◽  
Author(s):  
Laís De Bortoli Lecchi ◽  
Walnório Graça Ferreira ◽  
Paulo Manuel Mendes Pinheiro da Providência e Costa ◽  
Arlene Maria Cunha Sarmanho
Keyword(s):  
Reinforced Concrete ◽  
Nonlinear Analysis ◽  
Structural Engineering ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Geometrically Nonlinear ◽  
Approximate Methods ◽  
Element Analysis ◽  
Geometrically Nonlinear Analysis ◽  
Coefficient Method

abstract: Current practices in structural engineering demand ever-increasing knowledge and expertise concerning stability of structures from professionals in this field. This paper implements standardized procedures for geometrically nonlinear analysis of steel and reinforced concrete structures, with the objective of comparing methodologies with one another and with a geometrically exact finite element analysis performed with Ansys 14.0. The following methods are presented in this research: Load Amplification Method, from NBR 8800:2008; the γ z coefficient method, from NBR 6118:2014; the P-Delta iterative method and the α c r coefficient method, prescribed in EN 1993-1-1:2005. A bibliographic review focused on standardized approximate methods and models for consideration of material and geometric nonlinearities is presented. Numerical examples are included, from which information is gathered to ensure a valid comparison between methodologies. In summary, the presented methods show a good correlation of results when applied within their respective recommended applicability limits, of which, Eurocode 3 seems to present the major applicability range. The treated approximate methods show to be more suitable for regular framed structures subjected to regular load distributions.

A CO-ROTATIONAL FORMULATION FOR GEOMETRICALLY NONLINEAR FINITE ELEMENT ANALYSIS OF SPATIAL BEAMS

1994 ◽  
Vol 18 (1) ◽  
pp. 65-88 ◽  
Author(s):  
L. Jiang ◽  
M.W. Chernuka
Keyword(s):  
Finite Element ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Internal Force ◽  
Beam Element ◽  
Geometrically Nonlinear ◽  
Element Analysis ◽  
Finite Element Program ◽  
Geometrically Nonlinear Analysis ◽  
Spatial Beams

A co-rotational procedure is presented in this paper for handling arbitrarily large three-dimensional rotations associated with geometrically nonlinear analysis of spatial beam structures. This procedure has been incorporated into two commonly used 3-D beam elements, the 2-node cubic beam element and the 3-node superparametric beam element, in our in-house general purpose finite element program, VAST. In the present procedure, the element tangent stiffness matrices are generated by using the standard updated Lagrangian formulation, while a co-rotational formulation is employed to update the internal force vectors during the Newton-Raphson iterations, A number of example problems have been analyzed and the result are in good agreement with analytical or published numerical solutions.

Frequently Overlooked Heat Exchanger Design Conditions

2013 ◽  
Author(s):  
Andrey Gutkovsky ◽  
Jaan Taagepera
Keyword(s):  
Heat Exchanger ◽  
Loading Condition ◽  
Design Methodology ◽  
Bending Stress ◽  
Allowable Stress ◽  
Element Analysis ◽  
Design Rules ◽  
Channel Geometry ◽  
Heat Exchanger Design ◽  
Current Design

This paper explores the current design methodology for heat exchanger channel pass partition plates using ASME and TEMA design rules. Unanticipated elevated stress levels above allowable stress may exist at the channel pressure boundary due to differential pressure. In performing finite element analysis on two-pass heat exchanger channel geometry, elevated bending stress magnitudes were identified on the channel pressure boundary in the vicinity of the pass partition plate. These elevated stresses are induced by the pressure drop across channel passes, which load the pass partition plate and subject the channel pressure boundary to a bending stress which is frequently not evaluated. The combined membrane and bending stress may exceed allowable limits. This paper is intended to highlight this potentially overlooked loading condition in the design of heat exchanger channels.

Consistent co-rotational framework for Euler-Bernoulli and Timoshenko beam-column elements under distributed member loads

2021 ◽  
pp. 136943322098663
Author(s):  
Yi-Qun Tang ◽  
Wen-Feng Chen ◽  
Yao-Peng Liu ◽  
Siu-Lai Chan
Keyword(s):  
Coordinate System ◽  
Stiffness Matrix ◽  
Traditional Method ◽  
Local Coordinate System ◽  
Frame Structures ◽  
Global Coordinate System ◽  
Single Element ◽  
Geometrically Nonlinear ◽  
Geometrically Nonlinear Analysis ◽  
Geometric Stiffness

Conventional co-rotational formulations for geometrically nonlinear analysis are based on the assumption that the finite element is only subjected to nodal loads and as a result, they are not accurate for the elements under distributed member loads. The magnitude and direction of member loads are treated as constant in the global coordinate system, but they are essentially varying in the local coordinate system for the element undergoing a large rigid body rotation, leading to the change of nodal moments at element ends. Thus, there is a need to improve the co-rotational formulations to allow for the effect. This paper proposes a new consistent co-rotational formulation for both Euler-Bernoulli and Timoshenko two-dimensional beam-column elements subjected to distributed member loads. It is found that the equivalent nodal moments are affected by the element geometric change and consequently contribute to a part of geometric stiffness matrix. From this study, the results of both eigenvalue buckling and second-order direct analyses will be significantly improved. Several examples are used to verify the proposed formulation with comparison of the traditional method, which demonstrate the accuracy and reliability of the proposed method in buckling analysis of frame structures under distributed member loads using a single element per member.

scholarly journals Stator Non-Uniform Radial Ventilation Design Methodology for a 15 MW Turbo-Synchronous Generator Based on Single Ventilation Duct Subsystem

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2760
Author(s):  
Ruiye Li ◽  
Peng Cheng ◽  
Hai Lan ◽  
Weili Li ◽  
David Gerada ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Design Methodology ◽  
Large Scale ◽  
Synchronous Generator ◽  
Axial Direction ◽  
Scale Model ◽  
Element Analysis ◽  
Axial Temperature ◽  
Ventilation Duct

Within large turboalternators, the excessive local temperatures and spatially distributed temperature differences can accelerate the deterioration of electrical insulation as well as lead to deformation of components, which may cause major machine malfunctions. In order to homogenise the stator axial temperature distribution whilst reducing the maximum stator temperature, this paper presents a novel non-uniform radial ventilation ducts design methodology. To reduce the huge computational costs resulting from the large-scale model, the stator is decomposed into several single ventilation duct subsystems (SVDSs) along the axial direction, with each SVDS connected in series with the medium of the air gap flow rate. The calculation of electromagnetic and thermal performances within SVDS are completed by finite element method (FEM) and computational fluid dynamics (CFD), respectively. To improve the optimization efficiency, the radial basis function neural network (RBFNN) model is employed to approximate the finite element analysis, while the novel isometric sampling method (ISM) is designed to trade off the cost and accuracy of the process. It is found that the proposed methodology can provide optimal design schemes of SVDS with uniform axial temperature distribution, and the needed computation cost is markedly reduced. Finally, results based on a 15 MW turboalternator show that the peak temperature can be reduced by 7.3 ∘C (6.4%). The proposed methodology can be applied for the design and optimisation of electromagnetic-thermal coupling of other electrical machines with long axial dimensions.

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