Bending Capacity of Corroded Pipeline Subjected to Internal Pressure and Axial Loadings

2018 ◽  
Author(s):  
Jie Gao ◽  
Zengli Peng ◽  
Xin Li ◽  
Jing Zhou ◽  
Wenxing Zhou
Keyword(s):  
Internal Pressure ◽  
Local Buckling ◽  
Compressive Force ◽  
Bending Moment ◽  
Corrosive Media ◽  
Element Analysis ◽  
Axial Compressive Force ◽  
Offshore Pipelines ◽  
Bending Capacity ◽  
The Moment

Offshore pipelines operating in a harsh environment are usually subjected to combinations of bending moment and axial loadings in addition to internal pressure. Due to the corrosive media transported in the pipelines and corrosive substances within seawater and soil outside the pipelines, local corrosion defects will generate on the pipeline’s inner and outer walls, reducing its ultimate bearing capacity. This paper presents a series of full-scale failure tests and nonlinear finite element analysis (FEA) to study the bending capacity and failure mode of corroded pipelines with outside locally-thinned-areas (LTAs) subjected to combinations of internal pressure, axial compressive force and bending moment. The LTAs are loaded in compression to simulate corrosion. Material tests of API 5L X56 seamless pipe steel were conducted and the stress-strain relationship was obtained. FEA results of the moment versus curvature relation, bending capacity and local buckling behavior of each specimen model matched the experimental results very well, validating the accuracy of this simulation. Additional FEA is then performed to investigate the effect of corrosion geometric parameters, such as corrosion depth, corrosion width, and corrosion length, on the ultimate moment. Among them, the width is of the greatest impact, followed by is the depth, the length impact can be ignored.

EFFECTS OF THE INITIAL DEFLECTION SHAPE ON THE MOMENT AMPLIFICATION FACTOR OF BEAM-COLUMNS

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Haruna Utsunomiya ◽  
Masayuki Haraguchi ◽  
Masae Kido ◽  
Keigo Tsuda
Keyword(s):  
Amplification Factor ◽  
Slenderness Ratio ◽  
Compressive Force ◽  
Bending Moment ◽  
Load Ratio ◽  
Longitudinal Direction ◽  
Initial Deflection ◽  
Axial Compressive Force ◽  
Beam Columns ◽  
The Moment

In the design of slender steel beam-columns, the moment amplification factor is used to estimate the maximum moment along with the longitudinal direction. While formulas for evaluating the factor have been presented on the basis of elastic or elastic-plastic analysis, the initial deflection of the column is not considered. The effect that the initial deflection on the strength and behavior of the column has been shown only when the initial deflection shape is half sine wave. This paper discusses the effect of the initial deflection shape on the value of the moment amplification factor by performing the analytical work. The analytical model is the hinged-end beam-column subjected to constant axial compressive force and end moments. First of all, the equilibrium differential equation which governs the problem is solved and the formula for calculating the bending moment is presented. In the parametric study, magnitude of initial deflection, initial deflection shape, axial load ratio, slenderness ratio and end moment ratio are selected as the parameters. In this paper, we discuss the effects of the amount of the initial deflection and the initial deflection shape.

Study of Bending Capacity of an HPHT CRA-Lined Seamless Pipeline

2014 ◽  
Author(s):  
Cyprian Gil ◽  
Knut Tørnes ◽  
Per Damsleth
Keyword(s):  
Internal Pressure ◽  
Strain Localization ◽  
Local Buckling ◽  
Bending Moment ◽  
Design Criteria ◽  
Design Codes ◽  
Moment Capacity ◽  
Wide Range ◽  
Global Buckling ◽  
The Moment

A study has been performed to better understand ultimate bending moment and strain capacities of pipelines in relation to criteria defined in the design codes. An 18″ HPHT flowline was designed to undergo global buckling on uneven seabed and to resist trawl gear interference. The high temperature (155 degC) and pressure (300 bar) posed considerable design challenges for material selection and design criteria. A CRA-lined X60 CMn pipeline was selected for the project. The pipeline was of seamless manufacture for which the stress/strain characteristics are subject to the effect of Lüders bands. The DNV-OS-F101 code covers a wide range of D/t but does not specifically address Lüder’s material behaviour which could significantly reduce the bending moment capacity of pipe. The global buckling and trawl pull-over FE analysis results indicated the pipe was highly utilized, requiring excessive amounts of seabed intervention at great cost to meet the DNV LCC criteria. Detailed FE simulation of limit states for local buckling and strain localization of a 3D solid element pipe model was performed, with both Roundhouse and Lüders material properties, to investigate pipe capacity in relation to that stipulated by the design codes. The pipe moment capacity was established by obtaining the moment curvature relationship by bending the local pipe section subject to internal pressure until the maximum resistance was reached. Imperfections were introduced to initiate local buckling at the desired location. To determine strain concentration factors and strain localization, the effects of thickness changes and weld misalignment were also studied. The DNV OS-F101 LCC moment criterion formulation computes a decreasing moment capacity for increasing internal pressure. It has been suggested in the literature that this is correct for higher D/t but the criterion may be conservative for pipes with lower D/t. The combination of Lüders material with low D/t is not specifically addressed by any design code. Clarification of these aspects will provide a better understanding of the risk of failure for highly utilized seamless pipelines and allow for modified design criteria that will reduce seabed intervention costs. The results of the study showed that a higher bending moment criterion and associated strain criterion could be adopted for the design that allows for the higher initial strain caused by Lüder’s plateau. The ultimate bending moment capacity of low D/t pipe with Lüder’s material was found to be similar to that of Roundhouse material due to work hardening. In addition, it was demonstrated that the potential strength of the CRA liner could enhance the moment capacity of the seamless pipe.

scholarly journals Buckling Knockdown Factors of Composite Cylinders under Both Compression and Internal Pressure

Aerospace ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 346
Author(s):  
Do-Young Kim ◽  
Chang-Hoon Sim ◽  
Jae-Sang Park ◽  
Joon-Tae Yoo ◽  
Young-Ha Yoon ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Axial Compression ◽  
Shell Thickness ◽  
Slenderness Ratio ◽  
Compressive Force ◽  
Thickness Ratio ◽  
Element Analysis ◽  
Axial Compressive Force ◽  
Thin Walled ◽  
Composite Cylinders

The internal pressure of a thin-walled cylindrical structure under axial compression may improve the buckling stability by relieving loads and reducing initial imperfections. In this study, the effect of internal pressure on the buckling knockdown factor is investigated for axially compressed thin-walled composite cylinders with different shell thickness ratios and slenderness ratios. Various shell thickness ratios and slenderness ratios are considered when the buckling knockdown factor is derived for the thin-walled composite cylinders under both axial compression and internal pressure. Nonlinear post-buckling analyses are conducted using the nonlinear finite element analysis program, ABAQUS. The single perturbation load approach is used to represent the geometric initial imperfection of thin-walled composite cylinders. For cases with the axial compressive force only, the buckling knockdown factor decreases as the shell thickness ratio increases or as the slenderness ratio increases. When the internal pressure is considered simultaneously with the axial compressive force, the buckling knockdown factor decreases as the slenderness ratio increases but increases as the shell thickness ratio increases. The buckling knockdown factors considering the internal pressure and axial compressions are higher by 2.67% to 38.98% compared with the knockdown factors considering the axial compressive force only. The results show the significant effect of the internal pressure, particularly for thinner composite cylinders, and that the buckling knockdown factors may be enhanced for all the shell thickness ratios and slenderness ratios considered in this study when the internal pressure is applied to the cylinder.

Closed-Form Collapse Moment Equations of Elbows Under Combined Internal Pressure and In-Plane Bending Moment

2000 ◽  
Vol 122 (4) ◽  
pp. 431-436 ◽  
Author(s):  
J. Chattopadhyay ◽  
D. K. Nathani ◽  
B. K. Dutta ◽  
H. S. Kushwaha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Closed Form ◽  
Rotation Curve ◽  
Bending Moment ◽  
Loading Conditions ◽  
Moment Equations ◽  
Element Analysis ◽  
The Moment

Elastic-plastic finite element analysis has been carried out to evaluate collapse moments of six elbows with elbow factors varying from 0.24 to 0.6. The loading conditions of combined in-plane closing/opening bending moment and varying degree of internal pressure are considered in the analysis. For each case, collapse moment is obtained by twice elastic slope method from the moment versus end-rotation curve. Based on these results, two closed-form equations are proposed to evaluate the collapse moments of elbows under combined internal pressure and in-plane closing and opening bending moment. [S0094-9930(00)00103-7]

MOMENT AMPLIFICATION FACTOR OF BEAM-COLUMNS WITH INITIAL DEFLECTION

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Haruna Utsunomiya ◽  
Masayuki Haraguchi ◽  
Masae Kido ◽  
Keigo Tsuda
Keyword(s):  
Amplification Factor ◽  
Slenderness Ratio ◽  
Compressive Force ◽  
Bending Moment ◽  
Load Ratio ◽  
Initial Deflection ◽  
Axial Compressive Force ◽  
Beam Columns ◽  
Moment Ratio ◽  
The Moment

In the design of slender steel beam-columns, the moment amplification factor is used to estimate the maximum bending moment. The formulas for evaluating the factor have been presented on the basis of the elastic or elastic-plastic analysis, however the initial deflection of beam-columns is not considered. This paper discusses the effect of initial deflection on the value of the moment amplification factor by performing the analytical work. The analytical model is a simply supported beam-column subjected to constant axial compressive force and end moments. First of all, the equilibrium differential equation which governs the problem is solved and the formula for calculating the bending moment is obtained. In the parametric study, magnitude of the initial deflection, the axial load ratio, the slenderness ratio and the end moment ratio are selected as the parameters. The effects of magnitude of the initial deflection and the end moment ratio on the moment amplification factor are discussed.

Biomechanical Study of Lumbar Spine (L2-L4) Using Hybrid Stabilization Device - A Finite Element Analysis

2020 ◽  
Vol 10 (1) ◽  
pp. 20-32 ◽  
Author(s):  
Pushpdant Jain ◽  
Mohammed Rajik Khan
Keyword(s):  
Finite Element ◽  
Compressive Force ◽  
Element Model ◽  
Biomechanical Study ◽  
Bottom Surface ◽  
Element Analysis ◽  
Axial Compressive Force ◽  
Hybrid Stabilization ◽  
Flexion Extension ◽  
Lumbar Segment

Spinal instrumentations have been designed to alleviate lower back pain and stabilize the spinal segments. The present work aims to evaluate the biomechanical effect of the proposed Hybrid Stabilization Device (HSD). Non-linear finite element model of lumbar segment L2-L4 were developed to compare the intact spine (IS) with rigid implant (RI) and hybrid stabilization device. To restrict all directional motion vertebra L4 bottom surface were kept fixed and axial compressive force of 500N with a moment of 10Nm were applied to the top surface of L2 vertebrae. The results of range of motion (ROM), intervertebral disc (IVD) pressure and strains for IVD-23 and IVD-34 were determined for flexion, extension, lateral bending and axial twist. Results demonstrated that ROM of HSD model is higher than RI and lower as compared to IS model. The predicted biomechanical parameters of the present work may be considered before clinical implementations of any implants.

Strength and Deformation Capacity of Corroded Pipes: The Joint Industry Project

2013 ◽  
Author(s):  
Erik Levold ◽  
Andrea Restelli ◽  
Lorenzo Marchionni ◽  
Caterina Molinari ◽  
Luigino Vitali
Keyword(s):  
Failure Modes ◽  
State Of The Art ◽  
Local Buckling ◽  
Bending Moment ◽  
External Pressure ◽  
Fe Model ◽  
Deformation Capacity ◽  
Offshore Pipelines ◽  
Strength And Deformation ◽  
Bending Loading

Considering the future development for offshore pipelines, moving towards difficult operating condition and deep/ultra-deep water applications, there is the need to understand the failure mechanisms and better quantify the strength and deformation capacity of corroded pipelines considering the relevant failure modes (collapse, local buckling under internal and external pressure, fracture / plastic collapse etc.). A Joint Industry Project sponsored by ENI E&P and Statoil has been launched with the objective to quantify and assess the strength and deformation capacity of corroded pipes in presence of internal overpressure and axial/bending loading. In this paper: • The State-of-the-Art on strength and deformation capacity of corroded pipes is presented; • The full-scale laboratory tests on corroded pipes under bending moment dominated load conditions, performed at C-FER facilities, are shown together with the calibrated ABAQUS FE Model; • The results of the ABAQUS FEM parametric study are presented.

Procedure for Plastic Collapse Assessment of a Local Thin Area Near Vessel and Nozzle Intersections Subjected to Internal Pressure and External Loadings

2015 ◽  
Author(s):  
Shinji Konosu ◽  
Kenta Ogasawara ◽  
Kenji Oyamada
Keyword(s):  
Internal Pressure ◽  
Critical Region ◽  
Pressure Ratio ◽  
Branch Pipe ◽  
Bending Moment ◽  
Plastic Collapse ◽  
Element Analysis ◽  
Diagram Method ◽  
External Moment ◽  
Collapse Assessment

This paper develops a procedure for plastic collapse assessment of vessel (run pipe) - nozzle (branch pipe) intersections with an arbitrarily positioned local thin area (LTA) under different loading conditions, namely internal pressure, external moment on a nozzle applied along various directions with respect to the vessel main axis, and pure bending moment on a vessel. Although simplified procedures for plastic collapse assessment based on the p-M (internal pressure ratio and external bending moment ratio) diagram method have been previously proposed for straight cylindrical vessels and pipe bends with an LTA, very few studies have dealt with the determination of plastic collapse load for an LTA in the critical region of intersecting vessels subjected to internal pressure and external moment loading. This is likely due to the complexity of the stresses caused by the applied loads in the critical region, which arises from geometric discontinuities. In this paper, simple and empirical formulae for predicting conservative plastic collapse loads for an LTA in the critical region of the intersecting vessels are proposed based on the analytical results of stresses at defect-free vessel-nozzle intersections by using linear finite element analysis (FEA). Localized elastic stress retardation factors are taken into account in the evaluation by the results of a non-linear FEA. Consequently, a p-M diagram method is developed for application to vessel-nozzle intersections with an LTA.

Analytical Model for a Superelastic SMA Beam

2017 ◽  
Author(s):  
N. V. Viet ◽  
Wael Zaki ◽  
Rehan Umer
Keyword(s):  
Analytical Model ◽  
Bending Moment ◽  
Analytical Relation ◽  
Beam Model ◽  
Element Analysis ◽  
Austenitic Phase ◽  
Martensite Variant ◽  
The Moment ◽  
Reversible Phase ◽  
Good Agreement

We propose an analytical model for a superelastic shape memory alloy (SMA) beam. The model considers reversible phase transformation between austenite and a single martensite variant driven by mechanical loading/unloading. In particular, we consider a cantilever beam subjected to a concentrated transverse force acting at the tip. The force is gradually increased from zero to a maximum value sufficient to cause complete transformation of the initially austenitic phase into martensite away from the beam core. The force is then gradually removed, resulting in complete strain recovery. In each stage of the loading/unloading process, an analytical relation is established between bending moment and curvature in terms of position along the axis of the beam. The model is compared to a uniaxial numerical beam model and to finite element analysis (FEA) results for the same beam in 3D, with very good agreement in each case. The moment-curvature relation is then integrated to obtain a nonlinear expression for the deflection and stress distribution in terms of position along the length of the beam. The expression is validated against 3D simulation results.

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