Stress and flexibility factors for multi-mitred bends subjected to out-of-plane bending

1971 ◽  
Vol 6 (4) ◽  
pp. 213-225 ◽  
Author(s):  
M P Bond ◽  
R Kitching
Keyword(s):  
Theoretical Analysis ◽  
Maximum Stress ◽  
Large Diameter ◽  
Stress Distributions ◽  
Factors Associated ◽  
Out Of Plane ◽  
Thin Walled ◽  
Plane Bending ◽  
Stress Ratios

A theoretical analysis has been developed to predict stress distributions and flexibility factors associated with out-of-plane bending of multi-mitred pipe bends. The estimated range of validity of the analysis is sufficient to include most practical multi-mitred pipe bends. Tests on a large-diameter, thin-walled, three-weld right-angled multi-mitred bend were undertaken and the results closely agreed with computations based on the analysis. Predictions for both flexibility factors and overall maximum-stress ratios from the analysis were almost identical with those given by an in-plane bending theory that had been developed from a similar method of approach.

Stress and flexibility factors for multi-mitred pipe bends subjected to internal pressure combined with external loadings

1972 ◽  
Vol 7 (2) ◽  
pp. 97-108 ◽  
Author(s):  
M P Bond ◽  
R Kitching
Keyword(s):  
Internal Pressure ◽  
Large Diameter ◽  
Pipe Bend ◽  
Bending Tests ◽  
Bending Load ◽  
Out Of Plane ◽  
Thin Walled ◽  
Plane Bending ◽  
Internal Pressures ◽  
Stress Patterns

The stress analysis of a multi-mitred pipe bend when subjected to an internal pressure and a simultaneous in-plane or out-of-plane bending load has been developed. Stress patterns and flexibility factors calculated by this analysis are compared with experimental results from a large-diameter, thin-walled, three-weld, 90° multi-mitred bend which was subjected to in-plane bending tests at various internal pressures.

Stresses in Curved, Circular Thin-Wall Tubes

1963 ◽  
Vol 30 (1) ◽  
pp. 134-135
Author(s):  
E. A. Utecht
Keyword(s):  
Thin Wall ◽  
Bending Moments ◽  
Circular Tubes ◽  
Out Of Plane ◽  
Thin Walled ◽  
Plane Bending

Curves are presented which give stress intensification factors for curved, thin-walled circular tubes under various combinations of in-plane and out-of-plane bending moments.

Out-of-Plane Bending (Opb) Test of Large Diameter Mooring Chains

2021 ◽  
Author(s):  
m.r. Karimi ◽  
J. Braun ◽  
E. Gooijer ◽  
P. Barros ◽  
E. Carlberg ◽  
...  
Keyword(s):  
Large Diameter ◽  
Out Of Plane ◽  
Plane Bending

Bend Flexibility Factors of Piping Elbows and Piping Elbows With Trunnion Attachments Using the Boundary Element Method

2009 ◽  
Author(s):  
Manuel Martinez ◽  
Johane Bracamonte ◽  
Marco Gonzalez
Keyword(s):  
Boundary Element Method ◽  
Numerical Method ◽  
Bending Moment ◽  
Piping System ◽  
Thin Walled Structures ◽  
Out Of Plane ◽  
Thin Walled ◽  
Plane Bending ◽  
Flexibility Factor ◽  
Element Method

Flexibility Factor is an important parameter for the design of piping system related to oil, gas and power industry. Elbows give a great flexibility to piping system, but where a trunnion is attached to an elbow in order to support vertical pipe sections, the piping flexibility is affected. Generally, determination of elbow flexibility factors has been performed by engineering codes such as ASME B31.3 or ASME B31.8, or using the Finite Element Method (FEM) and Finite Difference Method (FDM). In this work, bend flexibility factors for 3D models of piping elbows and piping elbows with trunnion attachments using the Boundary Element Method (BEM) are calculated. The BEM is a relatively new numerical method for this kind of analysis, for which only the surface of the problem needs to be discretized into elements reducing the dimensionality of the problem. This paper shows the simulation of 9 elbows with commercially available geometries and 29 geometries of elbows with trunnion attachments, 10 of them using commercial elbow dimensions, with applied in-plane and out-of-plane bending moments. Structured meshes are used for all surfaces, except the contact surface of elbow-trunnion joints, and no welded joints are simulated. The results show smaller values of flexibility factors of elbow and elbow–trunnion attachments in all loading cases if are compared to ASME B31.3 or correlations obtained from other works. The results also indicate that flexibility factor for elbow-trunnion attachment subjected to in-plane bending moment is greater than flexibility factor for out-of plane bending moment. Accuracy of BEM’s results were not good when flexibility characteristic values are lesser than 0.300, which confirm the problems of this numerical method with very thin-walled structures. The method of limit element could be used as tool of alternative analysis for the design of made high-pitched system, when the problem with very thin-walled structures is fixed.

Exact Matching Condition at a Joint of Thin-Walled Box Beams Under Out-of-Plane Bending and Torsion

2012 ◽  
Vol 79 (5) ◽  
Author(s):  
Soomin Choi ◽  
Gang-Won Jang ◽  
Yoon Young Kim
Keyword(s):  
Beam Theory ◽  
Matching Condition ◽  
Higher Order ◽  
Transformation Matrix ◽  
Exact Matching ◽  
Box Beam ◽  
Out Of Plane ◽  
Box Beams ◽  
Thin Walled ◽  
Plane Bending

To take into account the flexibility resulting from sectional deformations of a thin-walled box beam, higher-order beam theories considering warping and distortional degrees of freedom (DOF) in addition to the Timoshenko kinematic degrees have been developed. The objective of this study is to derive the exact matching condition consistent with a 5-DOF higher-order beam theory at a joint of thin-walled box beams under out-of-plane bending and torsion. Here we use bending deflection, bending/shear rotation, torsional rotation, warping, and distortion as the kinematic variables. Because the theory involves warping and distortion that do not produce any force/moment resultant, the joint matching condition cannot be obtained just by using the typical three equilibrium conditions. This difficulty poses considerable challenges because all elements of the 5×5 transformation matrix relating the field variables of one beam to those in another beam should be determined. The main contributions of the investigation are to propose additional necessary conditions to determine the matrix and to derive it exactly. The validity of the derived joint matching transformation matrix is demonstrated by showing good agreement between the shell finite element results and those obtained by the present box beam analysis in various angle box beams.

Theoretical Analysis of the Stresses in Pipe Bends Subjected to Out-of-Plane Bending

1967 ◽  
Vol 9 (2) ◽  
pp. 115-123 ◽  
Author(s):  
R. T. Smith
Keyword(s):  
Theoretical Analysis ◽  
Digital Computer ◽  
Design Procedure ◽  
Theoretical Work ◽  
Theoretical Treatment ◽  
Bending Moments ◽  
Out Of Plane ◽  
Plane Bending ◽  
Comparison Of The Results ◽  
Maximum Stresses

Most of the experimental and theoretical work on the flexure of pipe bends has concerned bending in the plane of the bend but comparison of the results of some experiments using out-of-plane bending with calculations based on existing theories indicated a need for a more exact theoretical analysis of this form of loading. In this paper a comprehensive theoretical treatment of the elastic flexure of curved tubes already published for in-plane bending has been adapted to deal with out-of-plane bending. The equations for both forms of loading have been programmed for solution by a digital computer and a design procedure is suggested to find the maximum stresses due to combined in-plane, out-of-plane and torsional bending moments.

Out-of-Plane Bending Moment-Induced Hotspot Stress Evaluation Using Advanced Numerical Technique

2018 ◽  
Author(s):  
Jae-bin Lee ◽  
Weoncheol Koo ◽  
Joonmo Choung
Keyword(s):  
Numerical Technique ◽  
Bending Moment ◽  
Stress Distributions ◽  
Empirical Formulas ◽  
Element Analysis ◽  
Simulation Techniques ◽  
Analysis Technique ◽  
Out Of Plane ◽  
Plane Bending ◽  
Hotspot Stress

There have been various studies to predict out-of-plane bending (OPB) moment-induced stresses in mooring chain links. Recently, the BV guideline as one of the deliverables from OPB JIP reported empirical formulas to predict the nominal OPB moment-induced stress with suitable concentration factors (SCFs) so that prediction of the OPB moment-induced hotspot stresses can be available. A non-linear finite element analysis technique has been developed to more accurately estimate the OPB moment-induced hotspot stress. There has been no choice but to apply prescribed rotation to generate the OPB moment in this numerical technique (existing approach). Pointing out some disadvantages in the BV guideline and existing approach, an advanced numerical was proposed to simulate more realistic tension-induced OPB mechanism. In the present paper, basic differences were presented in terms of numerical simulation techniques, nominal OPB moments, and hotspot OPB stresses. In order to show differences of the stress distributions and the hotspot OPB stresses between existing and advanced approaches, a benchmark chain link model was constructed in which the nominal diameter was 107mm. From the comparison of stress distributions in straight parts of the link, significant differences were found between the existing and advanced approaches. The existing approach more developed the compressive stresses due to the prescribed rotation-induced OPB moment than the advanced approach. This also led to more increased hotspot OPB moments.

The Effects of Geometric Irregularities on the Design Analysis of Thin-Walled Piping Elbows

1980 ◽  
Vol 102 (4) ◽  
pp. 410-418 ◽  
Author(s):  
K. Thomas
Keyword(s):  
Internal Pressure ◽  
Maximum Stress ◽  
Numerical Data ◽  
Thickness Variation ◽  
Polynomial Functions ◽  
Pressure Loading ◽  
Thin Walled ◽  
Plane Bending ◽  
Longitudinal Welds ◽  
Comparable Magnitude

Geometric irregularities, such as ovality, in thin-walled elbows are known to give additional stresses under internal pressure loading. This paper presents results of detailed analyses, using the STAGS program, of a range of elbow geometries which have specified nonuniformities. Nonuniformities considered were thickness variation, initial ovality, intrados wrinkling and shrinkage of longitudinal welds. Loadings were in-plane bending and internal pressure. Results show that stresses due to in-plane bending are not significantly affected by the nonuniformities. However, stresses due to internal pressure are amplified by through-the-wall bending due to noncircularity of the cross section. Ovality, wrinkling and longitudinal weld shrinkage produce stress perturbations of comparable magnitude under internal pressure. Numerical data from the analyses are reduced to polynomial functions which give the maximum stress in the elbow as a function of pressure, radius-thickness ratio and degree of nonuniformity for long and short radius elbows.

Out-of-Plane Bending (OPB) Test of Large Diameter Mooring Chains

2020 ◽  
Author(s):  
P. Barros ◽  
E. Carlberg ◽  
I. S. Høgsæt ◽  
M. R. Karimi ◽  
J. Braun ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Large Diameter ◽  
Element Model ◽  
Maximum Diameter ◽  
Test Results ◽  
Test Setup ◽  
Out Of Plane ◽  
Plane Bending ◽  
A Chain

Abstract Chevron Corporation and Bluewater Energy Services (BES) performed a chain out-of-plane bending (OPB) test, called OPB MAX hereafter, at DNV GL’s laboratory in Høvik-Norway. The test was performed to study the OPB phenomenon for a chain diameter which was larger than the maximum diameter tested by the OPB JIP. The goal was to understand chain OPB physics for such a large diameter, measure interlink stiffness and maximum sliding moments and validate BES’ in-house finite element model. The current study is a collaboration between all involved parties and the results will be presented in three papers. The first paper summarizes the test setup and instrumentation. The second paper describes the test results, compares them with the OPB JIP estimations and tries to describe the chain OPB physics. The third and the last paper presents the FEA results performed by BES’ in-house finite element model. This paper is the first of the three and focuses on the test setup and instrumentation. The testing machine has been developed by DNV GL and is capable of applying tensions up to 350 t and interlink rotations in the range of ±3 degrees. Two 7-link chain specimens of R4 and R4s grades, both with the nominal diameter of 168 mm were tested at five tension levels from 150, to 350 t. Testing was performed in both wet and dry conditions. Twenty strain gauges were used to measure 3 OPB and 2 IPB moments at 5 mid-link positions. Twelve strain gauge rosettes were used on 3 links to evaluate SCF’s on the OPB hotspots. Seven inclinometers were used to monitor link rotations. DNV GL utilized a digital image processing tool to capture relative movements of chain links and developed a specific data processing tool to calculate the interlink stiffness, perform statistical analysis and provide several levels of data evaluation and comparison between the tests. The paper will provide a description of the test matrix and test objectives are given with the background of the previously performed OPB tests. Next a detailed description of the test rig is presented including the utilized instrumentation. Finally, an explanation of the implemented real-time test monitoring and the performed post-processing on the readings, in line with the test objectives is mentioned. The initial test results are briefly provided at the end.

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