Applying Finite Element Based Limit Load Analysis Methods to Structures Under Dynamic Loads

2014 ◽  
Author(s):  
Martin R. Booth
Keyword(s):  
Finite Element ◽  
Limit Load ◽  
Dynamic Loads ◽  
Plastic Collapse ◽  
Strength Assessment ◽  
Dynamic Events ◽  
Applied Loading ◽  
Analysis Technique ◽  
Dynamically Loaded ◽  
Load Analysis

To conduct an ASME III NG-3200 limit load strength assessment, it is required to determine the structure’s limit load under a particular loading configuration, and compare it against the applied loading represented as a static equivalent. Typically, the process is applied to static problems which have well-defined loading characteristics. When the limit load has been determined, often through the use of finite element (FE) based methods, the margin against plastic collapse is simple to calculate. For dynamically loaded structures, however, the process is more complicated since there are no ASME guidelines for expressing dynamic loads as their static equivalent. Thus, relating limit load analyses to dynamic events is not clear. This paper proposes an analysis technique which makes use of FE methods to apply the principles of limit load analysis to dynamically loaded structures. The primary benefit is that reserve factors against plastic collapse, in accordance with ASME III NG-3200 assessment criteria, can be calculated.

Estimate of the Ultimate Load on Structural Members Subjected to Lateral Loads

2001 ◽  
Vol 38 (03) ◽  
pp. 169-176
Author(s):  
L. Belenkiy ◽  
Y. Raskin
Keyword(s):  
Finite Element ◽  
Limit Analysis ◽  
Ultimate Load ◽  
Limit Load ◽  
Plastic Behavior ◽  
Lateral Loads ◽  
Ship Structures ◽  
Strength Assessment ◽  
Stiffened Panels ◽  
Plate Elements

This paper examines plastic behavior of typical ship structures, specifically beams, grillages, and plates subjected to predominantly lateral loads. The ultimate loads, determined on the basis of the theorems of limit analysis [1,2], are evaluated using nonlinear finite-element plastic analysis. The relationships between analytical and finite-element models for prediction of ultimate loads of beams, stiffened panels, and grillages are illustrated. It has been shown that the ultimate loads, obtained from the theorems of limit analysis, can be successfully used for strength assessment of stiffened ship structures subjected to lateral loads. The effect of shear force on ultimate load is analyzed using the finite-element method. This paper confirms that in the case of beams and grillages under lateral loading, the ultimate load may characterize the threshold of the load at which a stiffened ship's structure fails by the development of excessive deflections. For plate elements, on the other hand, the plastic deflections represent the permissible limit of external load better than the ultimate limit load.

scholarly journals Collapse load analysis for circumferentially cracked cylinder subjected to combined torsion and bending moments

2018 ◽  
Vol 192 ◽  
pp. 02024
Author(s):  
Sutham Arun ◽  
Thongchai Fongsamootr
Keyword(s):  
Finite Element Analysis ◽  
Limit Load ◽  
Failure Strength ◽  
Bending Moments ◽  
Collapse Load ◽  
Welding Zone ◽  
Element Analysis ◽  
Strength Assessment ◽  
Load Analysis ◽  
Cracked Cylinder

Cylinder is one of the most commonly used components which has a risk of having circumferential cracks, especially in the welding zone. When cracks are discovered, it is necessary to perform the failure strength assessment of cracked cylinder and the limit load play an important part as the input of the assessment. At present, the limit load solution for circumferential cracked cylinder under combined bending and torsion can be estimated by using the methods of equivalent moment or biaxial failure parameter. However, these methods still have some limitations. The main aim of this paper is to propose the alternative method for predicting the failure moment of circumferential cracked cylinder under combined bending and torsion. The method used in this paper is based on the modification of biaxial failure parameter and the data from finite element analysis. Details of this method is presented in this paper.

Effect of Mechanical Model on Limit Load Analysis of High Pressure Heater Tubesheet

2017 ◽  
Author(s):  
Yan-Nan Du ◽  
Xiao-Ying Tang ◽  
Jia-huan Wang ◽  
Zhi-Gang Yang ◽  
Yi-Feng Ren ◽  
...  
Keyword(s):  
High Pressure ◽  
Mechanical Model ◽  
High Stress ◽  
Local Stress ◽  
Limit Load ◽  
Element Model ◽  
Plastic Collapse ◽  
Analysis Design ◽  
Load Analysis ◽  
Collapse Assessment

Tubesheet is the main part of high pressure heater, which is very thick based on chinese code GB151 for the design of heat exchangers. Increased tubesheet with large thermal stress are not conducive to manufacture, heat transmission and detection. The stress and structure of tubesheet are so complex that the time costs too large during the analysis design, and stress classification exists uncertainty. Limit load method contributes to tubesheet lightweight. 3-D finite element model used for analysis design should be simplified reasonably. In this paper, the effect of mechanical model on limit load analysis of high pressure heater tubesheet conforming to the design-by-analysis code is researched. It is found that the tubesheet could pass the plastic collapse assessment, and the thickness of tubesheet could be decreased. The difference between the equivalent sold tubesheet model and the whole tubesheet model exists during plastic collapse assessment. Though the local stress distribution is different, the limit load results occurred plastic collapse by the equivalent sold tubesheet model is close to that by the whole tubesheet model. The limit load occurred plastic collapse is influenced by max circular diameter of tube layout little. The reason is attributed to original tubesheet owning enough rigidity related to thickness, and high stress appeares on the inner wall of jointing of tubesheet with head. The equivalent sold tubesheet model could be used for primary evaluation of limit load, and the whole tubesheet model is suited for partial analysis. The results provide some reference for the design-by-analysis of high pressure heater tubesheet.

Limit Load Analysis of Pressurized Containers

2014 ◽  
Author(s):  
C. Sklorz ◽  
F. Otremba ◽  
F. Reich
Keyword(s):  
Finite Element ◽  
Flow Stress ◽  
Yield Strength ◽  
Large Scale ◽  
Limit Load ◽  
Experimental Results ◽  
Small Scale ◽  
Finite Element Calculations ◽  
Load Analysis ◽  
Design Pressure

Limit load analysis is a well known method to calculate the allowable design pressure of container components. A limit load of a pressurized container is achieved, when the stress of a wall and the flow stress are equal. In the following paper the transferability of limit load analysis from small scale tank containers up to large scale containers (railway tank) are investigated. Finite element calculations are carried out and compared with experimental results. It can be concluded that the limit load analysis works very well. Furthermore, the yield strength of the material should be used as flow stress.

Limit Load Finite Element Analysis of Thick-Walled Cylinders with Surface Cracks under Combined Internal Pressure and Axial Tension

2011 ◽  
Vol 341-342 ◽  
pp. 416-420 ◽  
Author(s):  
Mahdi Maarefdoust ◽  
Pooria Akbarzade
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Surface Defects ◽  
Axial Loading ◽  
Limit Load ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Applied Loading ◽  
Approximate Analytical Solutions

Limit load analysis of defect free thick walled pipes and cylinders subjected to internal pressure and combined internal pressure and axial loading is commonly performed as part of integrity assessment procedures for transmission pipelines and pressure vessels across the industry. Moreover the potential impact of environmental assisted or accidental damage that result in creation of surface defects and consequently affects the ability of vessel to withstand the applied loading conditions. This paper attempts to demonstrate the effect of surface defects on the limit load of cylinders by use of finite element method. ABAQUS software has been used for FE analysis and modeling. Approximate analytical solutions for benchmark model have been used for validation/verification of numerical results.

Review of ASME III Code Case for the Application of Finite Element Based Limit Load Analysis

2011 ◽  
Author(s):  
Michael Martin ◽  
Chris Watson ◽  
Keith Wright
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Limit Analysis ◽  
Pressure Vessel ◽  
Load Capacity ◽  
Limit Load ◽  
Step Procedure ◽  
Load Analysis ◽  
Division 2 ◽  
Selection Of

The use of finite element based limit load analysis for the assessment of the primary load capacity of a pressure vessel is well established and numerous papers on the subject, including experimental results, have been published in the last decade. Finite element based limit load analysis is often used in the context of NB-3228.1 Limit Analysis to demonstrate a margin against ductile burst as an alternative to satisfaction of the NB-3200 limits on general, local and primary membrane plus bending stress intensity. However, although NB-3200 permits the use of ‘limit analysis’, no specific guidance on the use of finite element methods for this purpose is provided. Other pressure vessel codes, including ASME VIII Division 2 and EN13445 contain explicit guidance on the use of finite element methods for limit load analysis. To address this, a Code Case is currently under development to provide technical guidance on the use of finite element based limit load analysis within the context of NB-3200 assessments. The Code Case provides a step-by-step procedure which guides the analyst in the application of limit load analysis and ensures that a valid analysis has been undertaken. The topics of geometric weakening, yield surface selection, tentative wall thickness, element selection and selection of Sm are accounted for in the Code Case and discussed. This paper provides a detailed review of the Code Case and shows how it can be used in practice.

Inclusion of Torsion Loads in Section XI Flaw Evaluation Procedures for Pipes Containing Circumferential Planar Surface Crack-Like Flaws on the Basis of Limit Load Analysis

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Bostjan Bezensek ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Phuong H. Hoang
Keyword(s):  
Finite Element ◽  
Limit Load ◽  
Planar Surface ◽  
Straight Pipe ◽  
Evaluation Procedures ◽  
Piping Systems ◽  
Planar Crack ◽  
Bending Loads ◽  
Load Analysis ◽  
Bending Loading

Piping systems in power plant may experience combined bending-torsion loads in the presence of planar crack-like flaws. ASME Boiler and Pressure Vessel Code Section XI nonmandatory Appendix C provides flaw evaluation procedures for pipes with flaws. These are currently limited to straight pipes under pressure and bending loads and no provision is made for torsion loading. The working group on pipe flaw evaluation is developing guidance for including the torsion load within the existing solutions provided in the Appendix C for bending loading on a straight pipe under fully plastic fracture regime. This paper reports on the finite element limit load analyses performed on the straight pipe containing a circumferential planar crack-like flaw. Pipe diameters were ranging from 4 in. (100 mm) to 24 in. (600 mm) nominal diameter (OD) and R/t ranging from 6 to 40. For the purpose of nonmandatory Appendix C flaw evaluation, it is concluded that the torsion loads can be combined with bending loads using the root of the sum of the squares (RSS) method of Section III of the ASME Boiler Code, without any additional weighting on torsion.

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