Fatigue Assessment of Work-Over Risers Through Physical Testing

2014 ◽  
Author(s):  
Gerhard Gundersen ◽  
Rolf Hugo Kirkvik ◽  
Christopher Hoen-Sorteberg
Keyword(s):  
Structural Response ◽  
Fe Analysis ◽  
Bending Test ◽  
Measurement Technology ◽  
Fatigue Assessment ◽  
Inner Work ◽  
Physical Testing ◽  
Bending Loads ◽  
Operational Criteria ◽  
Variable Internal Pressure

Critical sections of work over strings, with respect to integrity, are components located close to end terminations, near well heads and above drill floors, where recurring bending moments are prevalent. The lifetime of these components are strongly dependent on the stiffness in the components of the string. Connections between these components are often complex, and of a type where the stiffness is unknown, or hard to reveal based on theoretical analysis. This paper considers the feasibility of applying state-of-the-art measurement technology for testing of the physical behavior of specific connections on a landing string to be used for work over operations in harsh environmental conditions, where low fatigue life of components have proven to be a recurring problem. Behavior of joint-connections revealed through measured response from physical testing serve as input for the global finite element (FE) analysis, where accumulated fatigue damage for each sea state is calculated based on site specific met-ocean data. The present work was carried out in advance of an operation on the Norwegian shelf, where a four-point bending test of the actual landing string to be used during the offshore campaign were performed on a section containing two critical couplings, in order to reveal the actual stiffness of the connections. The test string was subject to variable internal pressure, axial tension and bending loads, representative for the applicable work-over riser operational loads. The performance of the system was monitored through strain, displacement and force sensors, in order to relate applied loads to structural response. The results from these tests where later recreated from local FE analysis, where non linear springs was implemented and modified to fit the experimental results at the connections of interest. These springs was later input to the global fatigue analysis, where the complete system, including marine riser and inner work over string, was implemented in one model. Results from the fatigue assessment where used to determine the operational criteria for the work over operations.

A Theoretical and Experimental Analysis of the Bending Behavior of Unbonded Flexible Pipes

2014 ◽  
Author(s):  
Tatiana Vargas-Londoño ◽  
José Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Structural Response ◽  
Experimental Tests ◽  
Theoretical Models ◽  
External Pressure ◽  
Local Behavior ◽  
Flexible Pipes ◽  
Floating System ◽  
Bending Loads

Due to its compound cross-section, the prediction of the structural response of flexible pipes to loads such as their self-weight, internal and external pressure, movements imposed by the floating system and environmental loads such as currents, waves and wind is quite complex. All these loads generate stresses and strains in the cross section of the pipe that have to be properly evaluated in order to ensure integrity of the line. Research has been done on the local behavior of flexible pipes under combined axisymmetric loads as well as under bending loads. However, there is a lack of research combining both axisymmetric and bending loads, as also in the study of the strains in the tensile amour layers of the pipes, aspects which are important for the calibration of theoretical models to predict such behavior. Based on that, this study aims to evaluate the local behavior of flexible pipes under combinations of axisymmetric (tension, and internal pressure) and bending loads via a series of experimental tests in a 9.13″ I.D pipe. In the experimental tests, the behavior of the pipe was studied for three load combinations: i) bending combined with tension; ii) bending combined with internal pressure; and iii) bending combined with tension and internal pressure. Based on these tests, the authors obtained the strains in the tensile armor layer, axial elongation due to tension, axial reaction forces due to internal pressure, and deflection due to bending. These measurements were used to calibrate a theoretical model devoted to simulate the pipe’s response, getting accurate results for stiffness and stresses of the pipe in each scenario.

Post-Buckling Failure Modes of X65 Steel Pipe: An Experimental and Numerical Study

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Nima Mohajer Rahbari ◽  
Mengying Xia ◽  
Xiaoben Liu ◽  
J. J. Roger Cheng ◽  
Millan Sen ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Failure Modes ◽  
Bending Test ◽  
Bending Load ◽  
Post Buckling ◽  
X65 Steel ◽  
Bending Loads ◽  
Buckling Failure ◽  
Longitudinal Strains

In service pipelines exhibit bending loads in a variety of in-field situation. These bending loads can induce large longitudinal strains, which may trigger local buckling on the pipe's compressive side and/or lead to rupture of the pipe's tensile side. In this article, the post-buckling failure modes of pressurized X65 steel pipelines under monotonic bending loading conditions are studied via both experimental and numerical investigations. Through the performed full-scale bending test, it is shown that the post-buckling rupture is only plausible to occur in the pipe wall on the tensile side of the wrinkled cross section under the increased bending. Based on the experimental results, a finite element (FE)-based numerical model with a calibrated cumulative fracture criterion was proposed to conduct a parametric analysis on the effects of the internal pressure on the pipe's failure modes. The results show that the internal pressure is the most crucial variable that controls the ultimate failure mode of a wrinkled pipeline under monotonic bending load. And the post-buckling rupture of the tensile wall can only be reached in highly pressurized pipes (hoop stress no less than 70% SMYS for the investigated X65 pipe). That is, no postwrinkling rupture is likely to happen below a certain critical internal pressure even after an abrupt distortion of the wrinkled wall on the compressive side of the cross section.

An Efficient Direct Calculation Approach for Fatigue Assessment of Container Ships Concerning Bending and Warping Stresses

2014 ◽  
Author(s):  
Zhiyuan Li ◽  
Wengang Mao ◽  
Jonas W. Ringsberg
Keyword(s):  
Beam Theory ◽  
Direct Calculation ◽  
Fe Analysis ◽  
Hydrodynamic Simulation ◽  
Fatigue Assessment ◽  
Hull Girder ◽  
Torsional Loads ◽  
Warping Stress

Container ships are particularly susceptible to torsional loads. The distribution of torsion-induced warping stress in a container ship hull is more complicated and difficult to be expressed by beam theory formulas. In practice, finite element (FE) analysis is typically used to calculate the stress response to wave-loading conditions. However, it is time consuming to compute hull girder stresses for all relevant sea conditions through FE analyses. In this paper, an efficient and robust approach is proposed by combining beam theory and FE analyses in the determination of hull girder stresses. The parameters required by beam theory can be regressed through matching stress records from a FE analysis with the corresponding sectional and pressure loads from the hydrodynamic simulation. Stress records obtained using the proposed method are utilized in fatigue assessment of a case study container vessel. The results show that the accuracy of the regression approach is satisfactory compared with the full FE analyses.

Full-scale physical testing of a buried reinforced concrete pipe under axle load

2014 ◽  
Vol 51 (4) ◽  
pp. 394-408 ◽  
Author(s):  
G.R. Lay ◽  
R.W.I. Brachman
Keyword(s):  
Reinforced Concrete ◽  
Soil Cover ◽  
Limit State ◽  
Structural Response ◽  
Bending Moment ◽  
Full Scale ◽  
Surface Load ◽  
Burial Depth ◽  
Concrete Pipe ◽  
Physical Testing

The structural response of a 600 mm inner diameter reinforced concrete pipe buried in a dense, well-graded sand and gravel soil and subjected to surface load from a single design truck axle with 0.3, 0.6, and 0.9 m of soil cover above the pipe crown is quantified using full-scale physical testing. The pipe did not crack at its minimum burial depth of 0.3 m under working CL-625 and CL-800 single-axle highway design loads as the largest tensile strains were only 50%–60% of those at the onset of cracking. Application of the fully factored CL-625 single-axle load at a burial depth of 0.3 m resulted in a tensile crack and a maximum circumferential bending moment of 6 kN·m/m; however, no limit state was reached as the crack width was around one-half the value used to define pipe serviceability and the maximum moment was around 70% of the theoretical ultimate capacity. The decrease in pipe demand from surface load with increasing soil cover is also quantified. At 400 kN of single-axle force, the crown moment decreased to 65% and 35% of the value at 0.3 m burial when the depth of soil cover was increased to 0.6 and 0.9 m, respectively.

scholarly journals NONLINEAR FINITE ELEMENT ANALYSIS OF DAMAGED AND STRENGTHENED REINFORCED CONCRETE BEAMS

2014 ◽  
Vol 20 (2) ◽  
pp. 201-210 ◽  
Author(s):  
Muharrem Aktas ◽  
Yusuf Sumer
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Structural Response ◽  
Experimental Tests ◽  
Reinforced Concrete Beams ◽  
Bending Test ◽  
Element Analysis ◽  
Finite Element Program ◽  
Moment Capacity

Bending test of seven reinforced concrete beams are modeled in finite element program to validate the modeling strategies by comparing the structural response of the beams. Three beams in the set are pre-damaged and strengthened with fiber reinforced composites before the bending tests. Cracks are implemented into the model by inserting geometrical discontinuities to represent the pre-damaged beams. Parametric variables such as crack width, length and interval are chosen to simulate different pre-damage levels. Once the proposed modeling strategies are validated by real experimental tests then 196 finite element models are created to study the effects of pre-damage levels on the moment capacity of reinforced concrete beams repaired with CFRP. Results indicate that inclusion of pre-damage levels by means of cracks into the cross sections have significant effect on beams moment capacity.

Reeling of Tight Fit Pipe (TFP)

2007 ◽  
Author(s):  
E. S. Focke ◽  
E. Karjadi ◽  
A. M. Gresnigt ◽  
J. Meek ◽  
H. Nakasugi
Keyword(s):  
Compressive Stress ◽  
Bonding Strength ◽  
Fe Analysis ◽  
Bending Test ◽  
Outer Diameter ◽  
Stress Tests ◽  
Bending Tests ◽  
Definition Of ◽  
Mechanical Bonding ◽  
Pipe Bending

A 12.75 inch outer diameter single walled pipe bending test was executed and theoretical and FE analysis of this test was performed as preparation for 12.75 inch outer diameter TFP bending tests. The main objective of the TFP bending tests was to determine the initiation and degree of liner wrinkling occurring during the TFP spooling-on phase when simulating the reeling pipelay installation method. Due to lack of a definition of liner wrinkling initiation, the crossing of a certain threshold of the liner wrinkle height was defined as liner wrinkling initiation. The bending tests results indicated that (1) the extent of liner wrinkling decreased if TFP with a high mechanical bonding strength was used. (2) The presence of a circumferential weld in the highly bonded TFPs initiated higher liner wrinkles at lower curvatures than in case no circumferential weld was present. (3) The ERW outer pipe longitudinal weld did not result in higher liner wrinkles. API residual compressive stress tests showed that the initial mechanical bonding strength in the 12.75 inch TFP used in this research was significantly reduced, irrespective of whether a high or a low initial mechanical bonding strength had been used prior to spooling-on. These findings justify further research into this phenomenon as the eventual mechanical bonding strength after reeling installation may be vital for its anticipated application during operation.

scholarly journals Validation and Verification of Fatigue Assessment using FE Analysis: A Study Case on the Notched Cantilever Beam

2021 ◽  
Vol 33 ◽  
pp. 11-18
Author(s):  
Aprianur Fajri ◽  
Aditya Rio Prabowo ◽  
Eko Surojo ◽  
Fitrian Imaduddin ◽  
Jung Min Sohn ◽  
...  
Keyword(s):  
Cantilever Beam ◽  
Fe Analysis ◽  
Validation And Verification ◽  
Fatigue Assessment ◽  
Study Case

scholarly journals Physical and Mechanical Properties of Cassava-Bamboo Composite Lumber

2018 ◽  
Vol 2 (6) ◽  
pp. 6-9
Author(s):  
Ros Syazmini Mohd Ghani ◽  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Testing ◽  
Compression Test ◽  
Basic Density ◽  
Physical And Mechanical Properties ◽  
Modulus Of Rupture ◽  
Bending Test ◽  
Bambusa Vulgaris ◽  
Physical Testing ◽  
Composite Lumber

The study was carried out to determine the physical and mechanical properties of composite lumber made from cassava (Mahinot esculenta Crantz) and bamboo (Bambusa vulgaris) in different ratios which is 100% cassava with 0% bamboo, 75% cassava with 25% bamboo, 50% cassava with 50% bamboo, 25% cassava with 75% bamboo and 0% cassava with 100% bamboo. The tests samples for determining the strength properties were divided into two categories namely mechanical testing and physical testing. Basic density of the samples was carried out for physical testing. The lowest basic density was in samples with 100% cassava which is 0.49 g/cm3 and highest in samples with 100% bamboo which is 0.68 g/cm3 . Two tests for the mechanical testing are bending test and compression test. In bending test, modulus of elasticity (MOE) and modulus of rupture (MOR) were both highest for samples with 100% bamboo which the reading of MOE was 16794.03 N/mm2 and 122.52 N/mm2 for MOR. Similar to the bending test, compression test is the highest for the samples with 100% bamboo which are 65.58 N/mm2 . From statistical analysis, the basic density, static bending can compression strength give significant value at 95% confidence interval.

ERRATA: CORRIGENDA TO VIRTUAL HULL MONITORING: CONTINUOUS FATIGUE ASSESSMENT WITHOUT ADDITIONAL INSTRUMENTATION

2021 ◽  
Vol 161 (A4) ◽  
Author(s):  
I M Thompson
Keyword(s):  
Structural Response ◽  
Fatigue Assessment

Following publication of this study, work continued to enable more efficient structural response calculations. As part of that effort, two errors were identified and fixed.

ERRATA: Corrigenda to ‘Virtual Hull Monitoring: Continuous Fatigue Assessment Without Additional Instrumentation’: Technical Notes

2019 ◽  
Vol 161 (A4) ◽  
Keyword(s):  
Structural Response ◽  
Fatigue Assessment

Following publication of this study, work continued to enable more efficient structural response calculations. As part of that effort, two errors were identified and fixed.

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