New Procedures for the Residual Strength Assessment of Corroded Pipe Subjected to Combined Loads

1996 ◽  
Author(s):  
Marina Q. Smith ◽  
Stephen C. Grigory
Keyword(s):  
Finite Element ◽  
Failure Criterion ◽  
Failure Modes ◽  
Model Development ◽  
Metal Loss ◽  
General Corrosion ◽  
Moment Capacity ◽  
Strength Assessment ◽  
Global Buckling ◽  
Buckling Failure

Motivated by the inability to accurately address non-pressure related stresses within the framework of current assessment guidelines, a three phase study aimed at the progressive development of a reliable and readily-useable procedure suitable for the analysis of internally pressurized degraded pipes which sustain large settlement and/or axial loads was performed. To ensure accuracy of the resulting procedure, full-scale experiments and finite element numerical simulations of artificially corroded 48-inch (122-cm) diameter X65 pipes subjected to combined loadings were designed to produce upper and lower bound rupture and global buckling failure envelopes for a given set of representative corrosion dimensions. The evaluation model accommodates combined stresses arising from internal pressure, axial bending, and axially compressive loadings to predict operational margins of safety for a pipe containing discrete or multiple metal loss regions guided by failure criteria which considers two critical failure modes: 1) a von Mises type failure criterion for rupture moment capacity determination, and 2) a global buckling failure criterion for identification of the critical moment capacity approximating collapse of the pipe mid-section due to a reduction in bending stiffness attributed in part to ovalization of the cross-section. The new methodology has been incorporated in the personal computer based program SAFE (Shell Analysis Failure Envelope), developed by Southwest Research Institute (SwRI) for the Alyeska Pipeline Service Company. The user-friendly program allows for definition of combined applied stresses and geometry of the degraded region through implementation of field-obtainable pre-or post-excavation measurements, and employs unique features which provide for the examination of pipe sections exhibiting distinct areas of general corrosion, or “patches,” separated both longitudinally and circumferentially, in a single analysis run. This paper outlines the model development and validation with supporting experiments and numerical analyses, and extension of the new procedure through sophisticated numerical techniques embodied in SAFE to actual corrosion profiles and service loadings. Detailed information included in the review are the finite element and SAFE program failure predictions for pipes analyzed with a given set of corrosion dimensions and load magnitudes, and a thorough discussion of the practical application of the SAFE program.

scholarly journals Cyclic Load Test and Finite Element Analysis of NOVEL Buckling-Restrained Brace

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5103
Author(s):  
Robel Wondimu Alemayehu ◽  
Youngsik Kim ◽  
Jaehoon Bae ◽  
Young K. Ju
Keyword(s):  
Finite Element ◽  
Parametric Study ◽  
Cyclic Load ◽  
Failure Modes ◽  
Slenderness Ratio ◽  
Load Test ◽  
American Institute ◽  
Element Analysis ◽  
Global Buckling ◽  
Buckling Failure

Compared to concrete or mortar-filled Buckling-Restrained Braces (BRBs), all-steel BRBs provide weight and fabrication time reductions. In particular, all-steel buckling braces with H-section cores are gaining attention in cases where large axial strength is required. In this paper, an all-steel BRB, called NOVEL (Noise, CO2 emission, Vibration, Energy dissipation and Labor), is presented. It comprises an H-section core encased in a square casing, and its behavior was studied through full-scale subassembly and brace tests, followed by a finite element parametric study. Two failure modes were observed: global buckling and flange buckling of the H-section core, which occurred in test specimens with Pcr/Py ratios of 1.68 and 4.91, respectively. Global buckling occurred when the maximum moment in the casing reached its yielding moment, although the test specimens had sufficient stiffness to prevent global buckling. Failure by core flange buckling occurred at a core strain of 1.2%. The finite element parametric study indicated that adjusting the width-to-thickness ratio of the core flange is more feasible than stiffening the flange or adjusting the unconstrained-length end stiffeners. The value of 5.06 was the minimum flange slenderness ratio that provided a stable hysteresis to the end of the loading protocol of the American Institute of Steel Construction standard.

Remaining Local Buckling Resistance of Corroded Pipelines

2010 ◽  
Author(s):  
Qishi Chen ◽  
Heng Aik Khoo ◽  
Roger Cheng ◽  
Joe Zhou
Keyword(s):  
Finite Element ◽  
Wall Thickness ◽  
Phase 1 ◽  
Compressive Strain ◽  
Research Work ◽  
Local Buckling ◽  
Model Verification ◽  
Metal Loss ◽  
General Corrosion ◽  
Buckling Resistance

This paper describes a multi-year PRCI research program that investigated the local buckling (or wrinkling) of onshore pipelines with metal-loss corrosion. The dependence of local buckling resistance on wall thickness suggests that metal-loss defects will considerably reduce such resistance. Due to the lack of experimental data, overly conservative assumptions such as a uniform wall thickness reduction over the entire pipe circumference based on the defect depth have been used in practice. The objective of this research work was to develop local buckling criteria for pipelines with corrosion defects. The work related to local buckling was carried out in three phases by C-FER and the University of Alberta. The first phase included a comprehensive finite element analysis to evaluate the influence of various corrosion defect features and to rank key parameters. Based on the outcome of Phase 1 work, a test matrix was developed and ten full-scale tests were carried out in Phase 2 to collect data for model verification. In Phase 3, over 150 parametric cases were analyzed using finite element models to develop assessment criteria for maximum moment and compressive strain limit. Each criterion includes a set of partial safety factors that were calibrated to meet target reliabilities selected based on recent research related to pipeline code development. The proposed criteria were applied to in-service pipeline examples with general corrosion features to estimate the remaining load-carrying capacity and to assess the conservatism of current practice.

Integrity Assessment of Subsea Pipeline Dent / Buckle Using ILI Data

2019 ◽  
Author(s):  
Gurumurthy Kagita ◽  
Gudimella G. S. Achary ◽  
Mahesh B. Addala ◽  
Balaji Srinivasan ◽  
Penchala S. K. Pottem ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Failure Modes ◽  
Structural Integrity ◽  
Mechanical Damage ◽  
Metal Loss ◽  
Stress Concentrations ◽  
Subsea Pipeline ◽  
Integrity Assessment ◽  
Finite Element Software

Abstract Mechanical damage in subsea pipelines in the form of local dents / buckles due to excessive bending deformation may severely threaten their structural integrity. A dent / buckle has two significant effects on the pipeline integrity. Notably, residual stresses are set up as result of the plastic deformation and stress concentrations are created due to change in pipe geometry caused by the denting / buckling process. To assess the criticality of a dent / buckle, which often can be associated with strain induced flaws in the highly deformed metal, integrity assessment is required. The objective of this paper is to evaluate the severity of dent / buckle in a 48” subsea pipeline and to make the rerate, repair or replacement decision. This paper presents a Level 3 integrity assessment of a subsea pipeline dent / buckle with metal loss, reported in in-line inspection (ILI), in accordance with Fitness-For-Service Standard API 579-1/ASME FFS-1. In this paper, the deformation process that caused the damage (i.e. dent / buckle) with metal loss is numerically simulated using ILI data in order to determine the magnitude of permanent plastic strain developed and to evaluate the protection against potential failure modes. For numerical simulation, elastic-plastic finite element analyses (FEA) are performed considering the material as well as geometric non-linearity using general purpose finite element software ABAQUS/CAE 2017. Based on the numerical simulation results, the integrity assessment of dented / buckled subsea pipeline segment with metal loss has been performed to assess the fitness-for-service at the operating loads.

Designing Hierarchical IsoTruss Column Based on Controlling Multi-Buckling Behaviors

2021 ◽  
Author(s):  
Changliang Lai ◽  
Qianqian Sui ◽  
Hualin Fan
Keyword(s):  
Finite Element ◽  
Parametric Design ◽  
Local Buckling ◽  
Fe Model ◽  
The Finite Element Method ◽  
Buckling Modes ◽  
Buckling Behavior ◽  
Global Buckling ◽  
Buckling Failure ◽  
Theoretical Analyses

To develop large-span but ultralight lattice truss columns, a hierarchical IsoTruss column (HITC) was proposed. The multi-buckling behavior of the axially compressed HITC was analyzed by the finite element method (FEM) using a parametric approach in the framework of ANSYS parametric design language (APDL). It was demonstrated that the program enables efficient generation of the finite element (FE) model, while facilitating the parametric design of the HITC. Using this program, the effects of helical angles and brace angles on the buckling behavior of the HITC were investigated. Depending on the helical angles and brace angles, the HITCs mainly have three buckling modes: the global buckling, the first-order local buckling and the second-order local buckling. Theoretical multi-buckling models were established to predict the critical buckling loads. Buckling failure maps based on the theoretical analyses were also developed, which can be useful in preliminary design of such structures.

Buckling analyses of double-shell octagonal lattice truss composite structures

2017 ◽  
Vol 52 (9) ◽  
pp. 1227-1237 ◽  
Author(s):  
Qianqian Sui ◽  
Changliang Lai ◽  
Hualin Fan
Keyword(s):  
Failure Mode ◽  
Composite Structures ◽  
Failure Modes ◽  
Local Buckling ◽  
Buckling Mode ◽  
One Dimensional ◽  
Load Carrying ◽  
Global Buckling ◽  
Buckling Failure ◽  
Equivalent Continuum

To reveal the compression failure modes of one-dimensional hierarchical double-shell octagonal lattice truss composite structures (DLTCSs), finite element modeling and equivalent continuum models were developed. DLTCS has three typical failure modes: (a) fracture of the strut, (b) global buckling, and (c) local buckling. Failure mode maps were constructed. It is found that column of long enough length will collapse at global buckling. When the column length decreases, the failure mode will turn to local buckling and strut fracture successively. Bay length greatly influences the buckling mode. Longer bay length could change the buckling mode from global buckling to local buckling. Compared with single-shell lattice truss composite structure, DLTCS has advantage in load carrying when the column fails at strut fracture or global buckling, while local buckling tolerance of DLTCS is smaller.

Calculating Failure Pressure Under Different Failure Modes in the Roof-to-Shell of a Vaulted Tank

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yuqi Ding ◽  
Jubao Liu ◽  
Zengtao Chen ◽  
Feng Qiu ◽  
Qifa Lu
Keyword(s):  
Finite Element ◽  
Theoretical Calculation ◽  
Relative Error ◽  
Failure Criterion ◽  
Failure Modes ◽  
Maximum Relative Error ◽  
Failure Pressure ◽  
Compression Ring ◽  
Strength Failure ◽  
Ring Section

In this study, two failure modes, yield buckling of the compression ring section and strength failure in the roof-to-shell of the tank, have been proposed for a vertical vaulted tank. The failure criteria of the two failure modes in the roof-to-shell of vault tanks are established via finite element analysis of three tanks of 640 m3, 3200 m3, and 6800 m3 in volume. The finite element models are built with axisymmetric elements and spatial multi-elements. Based on the strength failure criterion, the failure pressure formula in the vaulted tank roof-to-shell is derived. The maximum relative error between the theoretical calculation and numerical simulation is 9.7%. Finally, we verify the strength failure criterion through a tank failure test; the maximum relative error between the test and theoretical calculation is 9.6%. The failure pressure of both failure modes has been compared and analyzed. The failure pressure of the yield buckling in the compression ring section is about 1.65 times that of the strength failure in the roof-to-shell of the tank.

In-Situ Compressive Strength of Carbon/Epoxy AS4/3501-6 Laminates

1993 ◽  
Vol 115 (1) ◽  
pp. 122-128 ◽  
Author(s):  
G. E. Colvin ◽  
S. R. Swanson
Keyword(s):  
Test Specimen ◽  
Failure Modes ◽  
Failure Strain ◽  
Free Edge ◽  
Experimental Program ◽  
Compression Behavior ◽  
Failure Data ◽  
Global Buckling ◽  
Buckling Failure

An experimental program has been conducted to evaluate how changes in laminate lay-up can influence the compression behavior of fiber-dominated, resin-based composites. The testing utilized a cylindrical, 3.81 cm (1.5 in.) diameter test specimen because it provides inherent resistance to global buckling failure modes and lack of free edge effects. Seven different laminates representing 0° dominated lay-ups, axial bias lay-ups, and quasi-isotropic lay-ups were tested. The measured macroscopic stress strain failure data showed a strong in-situ dependence of the 0° failure strain on the lay-up. The quasi-isotropic laminate failure strains were nearly twice the 0° dominated laminate failure strains. Photomicrographs of the failure zone from sections of failed specimens showed the presence of fiber kinking in all the laminate failures.

Finite Element Analysis on the Failure Behavior of Straight Pipe With Wall Thinning

2004 ◽  
Author(s):  
Ken Inoue ◽  
Koji Takahashi ◽  
Kotoji Ando ◽  
Seok Hwan Ahn ◽  
Ki Woo Nam ◽  
...  
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Local Buckling ◽  
Metal Loss ◽  
Failure Behavior ◽  
Straight Pipe ◽  
Element Analysis ◽  
Deformation And Failure ◽  
Wall Thinning ◽  
Local Wall Thinning

Monotonic four-point bending tests were conducted using straight pipe specimens 102 mm in diameter with local wall thinning in order to investigate the effects of the depth, shape, and location of wall thinning on the deformation and failure behavior of pipes. The local wall thinning simulated erosion/corrosion metal loss. The deformation and fracture behavior of the straight pipes with local wall thinning was compared with that of non wall-thinning pipes. The failure modes were classified as local buckling, ovalization, or crack initiation depending on the depth, shape, and location of the local wall thinning. Three-dimensional elasto-plastic analyses were carried out using the finite element method. The deformation and failure behavior, simulated by finite element analyses, coincided with the experimental results.

scholarly journals Partial Strength Beam-to-column Connection of Cold-formed Single Channel Section: Numerical and Experimental Study

2021 ◽  
Vol 14 ◽  
pp. 1-11
Author(s):  
Faisal Amsyar Redzuan
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Single Channel ◽  
Three Dimensional ◽  
Analysis Data ◽  
Numerical Approach ◽  
Realistic Model ◽  
Nonlinear Material ◽  
Structural Behaviour ◽  
Moment Capacity

A full understanding of complex structural behaviour can be developed perfectly by using the combination of experimental and numerical approach. Although the basic method to determine the moment-rotation responses of the beam-to-column CFS joints has recently established from the full-scale testing, practising the finite element modelling (FEM) nowadays could explore in-depth on the number of variables and potential failure modes. In this paper, three-dimensional (3-D) model to simulate the actual behaviour of the beam-to-column CFS joints has been proposed by using multi-purpose finite element package ABAQUS version 6.14 in order to validate analysis data against the experimental works. The approach of nonlinear material characteristics, contact and sliding between different components and adopting C3D8R solid elements are proposed in this model. A total of three (3) beam-to-column CFS connections consisting of three different types of beam depths were tested in isolation in order to observe the structural behaviour based on its strength and stiffness. Comparisons between experimental and FE analysis results in term of ultimate moment capacity have shown a good correlation with strength ratios ranging from 1.12 to 1.17. Therefore, it is possible to develop a realistic model for future parametric studies such as type and configurations of the connections.

A New Method for Analyzing X-Cor Sandwich’s Shear Strength

2012 ◽  
Vol 510 ◽  
pp. 356-361
Author(s):  
Xu Dan Dang ◽  
Shao Jie Shi ◽  
Yi Guo ◽  
Jun Xiao
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Failure Criterion ◽  
Failure Modes ◽  
Failure Process ◽  
Stiffness Degradation ◽  
Strength Analysis ◽  
Finite Element Software ◽  
Pull Out ◽  
Comparison Results

The finite element software was used to get the X-cor sandwich’s shear strength. During the shear strength analysis, the failure criterion and materials stiffness degradation rules fitting for the analysis of X-cor sandwich’s failure mechanism were proposed and the X-cor sandwich’s failure process and modes were also clarified. According to the failure criterion we used the elements with stiffness degradation and their distributions in the finite element model to simulate the types and propagation path of the failure and the failure mechanisms of X-cor sandwich under shear were explained. The finite element analysis indicates during the shear firstly the resin regions fail and then the multiple failure modes of Z-pin pull-out from the face-sheet, Z-pin shear off and Z-pin buckling all exist. The propagation paths of the failure elements are dispersive. By contrasting the finite element results and test results the values are consistent well and the error range is -10.4%~7.4%. The comparison results show that the failure criterion and stiffness degradation rules are reasonable and this method can be used to predict the X-cor sandwich’s shear strength.

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