Local Limit Load Analytical Model for Thick-Walled Pipe With Axial Surface Defect

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Igor Orynyak ◽  
Sergii Ageiev ◽  
Sergii Radchenko ◽  
Maksym Zarazovskii
Keyword(s):  
Limit State ◽  
Plastic Hinge ◽  
Bending Moment ◽  
Local Limit ◽  
Limit Load ◽  
Crack Location ◽  
Axial Defects ◽  
Thin Walled Pipe ◽  
Analytical Formulas ◽  
Hoop Stresses

Based on the previous limit load analytical modeling for cracked thin-walled pipe (Orynyak, I. V., 2006, “Leak and Break Models of Pressurized Pipe With Axial Defects,” Proceedings of the 6th International Pipeline Conference (IPC), Calgary, Alberta, Canada, Paper No. IPC2006-10066, pp. 41–56), the limit load model for thick-walled pipe had developed. There are some additional peculiarities included in the proposed model. First, the distribution of radial stresses is taken into consideration in the limit state formulation using Tresca's criterion. Second, related to the crack location and interaction of hoop stresses (due to the inner pressure) and axial ones (caused by local bending moment) have been assessed in the limit state. Third, hoop stresses redistribution with possibility of plastic hinge formation in zone opposite to the crack is taken into account. Finally, the proposed easy to use analytical formulas have been verified by comparing with full-scale burst tests.

Local Limit Load Analytical Model for Thick-Walled Pipe With Axial Surface Defect

2014 ◽  
Author(s):  
Sergii Ageiev ◽  
Igor Orynyak ◽  
Sergii Radchenko ◽  
Maksym Zarazovskii
Keyword(s):  
Hoop Stress ◽  
Limit State ◽  
Plastic Hinge ◽  
Bending Moment ◽  
Local Limit ◽  
Limit Load ◽  
Crack Location ◽  
Thin Walled Pipe ◽  
Crack Zone ◽  
Analytical Formulas

Based on the previous limit load analytical modeling for cracked thin-walled pipe [1] the limit load model for thick-walled pipe had developed. There are some additional peculiarities included in proposed model. First, the radial stresses distribution and their accounting for the Tresca’s criterion. Second, the crack location and related to it the interaction of hoop stress (due to the inner pressure) and axial one (caused by local bending moment) in the limit state. Third, hoop stress redistribution with possibility of plastic hinge forming in the zone, which is opposite to the crack zone. Forth, an analysis of derived easy to use analytical formulas by comparing with results of full-scale burst test.

Elastic-plastic bending of the pipeline under combined loading

2021 ◽  
pp. 372-377
Author(s):  
Виктор Миронович Варшицкий ◽  
Евгений Павлович Студёнов ◽  
Олег Александрович Козырев ◽  
Эльдар Намикович Фигаров
Keyword(s):  
Internal Pressure ◽  
Limit State ◽  
Bending Moment ◽  
Axial Direction ◽  
Longitudinal Force ◽  
Combined Loading ◽  
Dimensional Problem ◽  
Elastic Plastic ◽  
Pipeline Section ◽  
Thin Walled Pipe

Рассмотрена задача упругопластического деформирования тонкостенной трубы при комбинированном нагружении изгибающим моментом, осевой силой и внутренним давлением. Решение задачи осуществлено по разработанной методике с помощью математического пакета Matcad численным методом, основанным на деформационной теории пластичности и безмоментной теории оболочек. Для упрощения решения предложено сведение двумерной задачи к одномерной задаче о деформировании балки, материал которой имеет различные диаграммы деформирования при сжатии и растяжении в осевом направлении. Проведено сравнение с результатами численного решения двумерной задачи методом конечных элементов в упругопластической постановке. Результаты расчета по инженерной методике совпадают с точным решением с точностью, необходимой для практического применения. Полученные результаты упругопластического решения для изгибающего момента в сечении трубопровода при комбинированном нагружении позволяют уточнить известное критериальное соотношение прочности сечения трубопровода с кольцевым дефектом в сторону снижения перебраковки. Применение разработанной методики позволяет ранжировать участки трубопровода с непроектным изгибом по степени близости к предельному состоянию при комбинированном нагружении изгибающим моментом, продольным усилием и внутренним давлением. The problem of elastic plastic deformation of a thin-walled pipe under co-binned loading by bending moment, axial force and internal pressure is considered. The problem is solved by the developed method using the Matcad mathematical package by a numerical method based on the deformation theory of plasticity and the momentless theory of shells. To simplify the solution of the problem, it is proposed to reduce a twodimensional problem to a one-dimensional problem about beam deformation, the material of which has different deformation diagrams under compression and tension in the axial direction. Comparison with the results of numerical solution of the two-dimensional problem with the finite element method in the elastic plastic formulation is carried out. The obtained results of the elastic-plastic solution for the bending moment in the pipeline section under combined loading make it possible to clarify criterion ratio of the strength of the pipeline section with an annular defect in the direction of reducing the rejection. Application of the developed approach allows to rank pipeline sections with non-design bending in the steppe close to the limit state under combined loading of the pipeline with bending moment, longitudinal force and internal pressure.

scholarly journals Combined rupture mechanisms in shallow foundations

2018 ◽  
Vol 55 (6) ◽  
pp. 829-838 ◽  
Author(s):  
A. Gajo ◽  
C.C. Smith
Keyword(s):  
Limit State ◽  
Load Condition ◽  
Bending Moment ◽  
Limit Load ◽  
Shallow Foundation ◽  
Ultimate Limit State ◽  
Rigid Plastic ◽  
Foundation Design ◽  
Full Analysis ◽  
Ultimate Limit

Conventional ultimate limit state (ULS) shallow foundation design is typically based on a simplified analysis that fails to consider the possible existence of a combined structural and geotechnical failure, which is shown here to significantly affect the limit load. Neglecting this occurrence may lead to unsafe design, whereas a full analysis can be beneficial for the dimensioning. With the emphasis on separate serviceability limit state and ULS design in modern design codes such as Eurocode 7 (EN 1997-1, 2004 edition), this paper explores unsafe loading scenarios and the benefits to be gained from a rigorous ULS design based on combined failure. For the sake of simplicity, a long foundation slab subjected to three different loading conditions is analysed using elastic, elasto-plastic, and rigid-plastic methods, and the results compared for a range of foundation strengths and stiffnesses. It is found that the limit load may be significantly influenced by plastic hinges in the structure and for each load condition it is possible to derive a curve relating ultimate load to plastic bending moment representing the ultimate limit state of the foundation.

Burst Pressure Predictions of Corroded Pipelines With Long Defects: Failure Criteria and Validation

2009 ◽  
Author(s):  
Mario S. G. Chiodo ◽  
Claudio Ruggieri
Keyword(s):  
Large Diameter ◽  
Local Limit ◽  
Limit Load ◽  
Plastic Instability ◽  
Failure Criteria ◽  
Burst Pressure ◽  
Instability Analysis ◽  
Diameter Pipe ◽  
Axial Defects ◽  
Ligament Instability

This study examines the applicability of a stress-based criterion based upon plastic instability analysis to predict the failure pressure of corroded pipelines with axial defects. A central focus is to gain additional insight into effects of defect geometry and material properties on the attainment of a local limit load to support the development of stress-based burst strength criteria. A verification study conducted on burst testing of large-diameter pipe specimens with different defect length shows the effectiveness of a stress-based criterion using local ligament instability in burst pressure predictions, even though the adopted burst criterion exhibits a potential dependence on defect geometry and possibly on material’s strain hardening capacity. Overall, the results presented here suggests that use of stress-based criteria based upon plastic instability analysis of the defect ligament is a valid engineering tool for integrity assessments of pipelines with axial corroded defects.

Combined flexure and torsion of I-shaped steel beams

1989 ◽  
Vol 16 (2) ◽  
pp. 124-139 ◽  
Author(s):  
Robert G. Driver ◽  
D. J. Laurie Kennedy
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Phase Behaviour ◽  
Inelastic Interaction ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Second Phase ◽  
Design Standards ◽  
Limit States ◽  
Interaction Diagram

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members. Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.

Anchor rod forces and maximum bending moments in sheet pile walls using the factored strength approach

1996 ◽  
Vol 33 (5) ◽  
pp. 815-821 ◽  
Author(s):  
A B Schriver ◽  
A J Valsangkar
Keyword(s):  
Water Pressure ◽  
Limit State ◽  
Bending Moment ◽  
Ultimate Limit State ◽  
Sheet Pile ◽  
Limit States ◽  
Working Stress ◽  
Geotechnical Design ◽  
Ultimate Limit State Design ◽  
Sheet Pile Wall

Recently, the limit states approach using factored strength has been recommended in geotechnical design. Some recent research has indicated that the application of limit states design using recommended load and strength factors leads to conservative designs compared with the conventional methods. In this study the influence of sheet pile wall geometry, type of water pressure distribution, and different methods of analysis on the maximum bending moment and achor rod force are presented. Recommendations are made to make the factored strength design compatible with conventional design. Key words: factored strength, working stress design, ultimate limit state design, anchored sheet pile wall, bending moment, anchor rod force.

Limit Load Analysis of Cracked Components Using the Reference Volume Method

2006 ◽  
Vol 129 (3) ◽  
pp. 391-399 ◽  
Author(s):  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Elastic Modulus ◽  
Three Dimensional ◽  
Local Limit ◽  
Limit Load ◽  
Multiple Cracks ◽  
Element Analysis ◽  
Limit Loads ◽  
Integrity Assessment ◽  
Reference Volume ◽  
Volume Method

Cracks and flaws occur in mechanical components and structures, and can lead to catastrophic failures. Therefore, integrity assessment of components with defects is carried out. This paper describes the Elastic Modulus Adjustment Procedures (EMAP) employed herein to determine the limit load of components with cracks or crack-like flaw. On the basis of linear elastic Finite Element Analysis (FEA), by specifying spatial variations in the elastic modulus, numerous sets of statically admissible and kinematically admissible distributions can be generated, to obtain lower and upper bounds limit loads. Due to the expected local plastic collapse, the reference volume concept is applied to identify the kinematically active and dead zones in the component. The Reference Volume Method is shown to yield a more accurate prediction of local limit loads. The limit load values are then compared with results obtained from inelastic FEA. The procedures are applied to a practical component with crack in order to verify their effectiveness in analyzing crack geometries. The analysis is then directed to geometries containing multiple cracks and three-dimensional defect in pressurized components.

Fully Plastic Failure Stresses and Allowable Crack Sizes for Circumferentially Surface Cracked Pipes Subjected to Tensile Loading

2021 ◽  
Author(s):  
Kunio Hasegawa ◽  
David Dvorak ◽  
Vratislav Mares ◽  
Bohumir Strnadel ◽  
Yinsheng Li
Keyword(s):  
Experimental Data ◽  
Bending Moment ◽  
Limit Load ◽  
Tensile Loading ◽  
Crack Size ◽  
Plastic Failure ◽  
Circumferential Crack ◽  
Asme Code ◽  
American Society ◽  
Better Than

Abstract Fully plastic failure stresses for circumferentially surface cracked pipes subjected to tensile loading can be estimated by means of limit load criteria based on the net-section stress approach. Limit load criteria of the first type (labelled LLC-1) were derived from the balance of uniaxial forces. Limit load criteria of the second type are given in Section XI of the ASME (American Society of Mechanical Engineering) Code, and were derived from the balance of bending moment and axial force. These are labelled LLC-2. Fully plastic failure stresses estimated by using LLC-1 and LLC-2 were compared. The stresses estimated by LLC-1 are always larger than those estimated by LLC-2. From the literature survey of experimental data, failure stresses obtained by both types of LLC were compared with the experimental data. It can be stated that failure stresses calculated by LLC-1 are better than those calculated by LLC-2 for shallow cracks. On the contrary, for deep cracks, LLC-2 predictions of failure stresses are fairly close to the experimental data. Furthermore, allowable circumferential crack sizes obtained by LLC-1 were compared with the sizes given in Section XI of the ASME Code. The allowable crack sizes obtained by LLC-1 are larger than those obtained by LLC-2. It can be stated that the allowable crack size for tensile stress depends on the condition of constraint of the pipe, and the allowable cracks given in Section XI of the ASME Code are conservative.

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