A Numerical Lab to Predict the Strength Capacity of Offshore Pipelines

2005 ◽  
Author(s):  
Roberto Bruschi ◽  
Lorenzo Bartolini ◽  
Maurizio Spinazze` ◽  
Enrico Torselletti ◽  
Luigino Vitali
Keyword(s):  
Failure Modes ◽  
Limit State ◽  
Design Procedure ◽  
Point Load ◽  
Fe Analysis ◽  
Quantitative Prediction ◽  
Load Force ◽  
Line Pipe ◽  
Offshore Pipelines ◽  
Strength Capacity

In the recent years, the offshore pipeline industry has been under pressure to provide solutions for demanding material and line pipe technology problems, installation technology to safely tackle the ultra-deep waters challenge, quantitative prediction of reliable operating lifetime for pipelines under high pressure/high temperature conditions and remedial measures to tackle considerable geo-morphic and human activity related hazards. Future pipelines are being planned in very difficult environments, i.e. crossing ultra-deep water and difficult geo-seismic-morphic conditions. In these circumstances, it is of crucial importance (1) to adopt advanced design procedure and criteria, possibly based on limit state principles recently implemented in the design codes, and (2) to use advanced engineering tools for predicting the strength capacity and the pipeline behaviour during the installation and operational phase, in order to design the pipeline safely and to assess properly the technic-economical feasibility of the project. This paper discusses the relevant failure modes for offshore pipelines, the FE analysis results relevant to the sectional capacity of thick-walled pipes, and the FE analysis results relevant to the global and local response effect of a pipeline, laid on the sea bottom, and subject to a point-load force.

Influence of Human Error on Structural Reliability

2017 ◽  
Author(s):  
Eric Brehm ◽  
Robert Hertle ◽  
Markus Wetzel
Keyword(s):  
Human Error ◽  
Structural Reliability ◽  
Failure Modes ◽  
Structural Model ◽  
Limit State ◽  
Design Procedure ◽  
Material Strength ◽  
Limit States ◽  
The Impact

In common structural design, random variables, such as material strength or loads, are represented by fixed numbers defined in design codes. This is also referred to as deterministic design. Addressing the random character of these variables directly, the probabilistic design procedure allows the determination of the probability of exceeding a defined limit state. This probability is referred to as failure probability. From there, the structural reliability, representing the survival probability, can be determined. Structural reliability thus is a property of a structure or structural member, depending on the relevant limit states, failure modes and basic variables. This is the basis for the determination of partial safety factors which are, for sake of a simpler design, applied within deterministic design procedures. In addition to the basic variables in terms of material and loads, further basic variables representing the structural model have to be considered. These depend strongly on the experience of the design engineer and the level of detailing of the model. However, in the clear majority of cases [1] failure does not occur due to unexpectedly high or low values of loads or material strength. The most common reasons for failure are human errors in design and execution. This paper will provide practical examples of original designs affected by human error and will assess the impact on structural reliability.

Evaluation of the Effect of Yield to Tensile (Y/T) Ratio on the Structural Integrity of Offshore Pipeline by Limit State Design Approach

2006 ◽  
Author(s):  
Gianluca Mannucci ◽  
Giuliano Malatesta ◽  
Giuseppe Demofonti ◽  
Marco Tivelli ◽  
Hector Quintanilla ◽  
...  
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Structural Integrity ◽  
Limit State ◽  
Minor Effect ◽  
Offshore Pipelines ◽  
Limit State Design ◽  
A Minor ◽  
Probabilistic Failure Analysis ◽  
Failure Probabilities

Nowadays specifications require strict Yield to Tensile ratio limitation, nevertheless a fully accepted engineering assessment of its influence on pipeline integrity is still lacking. Probabilistic analysis based on structural reliability approach (Limit State Design, LSD) aimed at quantifying the yield to tensile strength ratio (Y/T) influence on failure probabilities of offshore pipelines was made. In particular, Tenaris seamless pipe data were used as input for the probabilistic failure analysis. The LSD approach has been applied to two actual deepwater design cases that have been on purpose selected, and the most relevant failure modes have been considered. Main result of the work is that the quantitative effect of the Y/T ratio on failure probabilities of a deepwater pipeline resulted not so big as expected; it has a minor effect, especially when Y only governs failure modes.

Minimum Wall Thickness Requirements for Ultra Deep-Water Pipelines

2003 ◽  
Author(s):  
Enrico Torselletti ◽  
Luigino Vitali ◽  
Roberto Bruschi ◽  
Leif Collberg
Keyword(s):  
Wall Thickness ◽  
Deep Water ◽  
Failure Modes ◽  
Limit State ◽  
Strain Curve ◽  
External Pressure ◽  
Design Guidelines ◽  
Compressive Yield Strength ◽  
Pipe Material ◽  
Line Pipe

The offshore pipeline industry is planning new gas trunklines at water depth ever reached before (up to 3500 m). In such conditions, external hydrostatic pressure becomes the dominating loading condition for the pipeline design. In particular, pipe geometric imperfections as the cross section ovality, combined load effects as axial and bending loads superimposed to the external pressure, material properties as compressive yield strength in the circumferential direction and across the wall thickness etc., significantly interfere in the definition of the demanding, in such projects, minimum wall thickness requirements. This paper discusses the findings of a series of ultra deep-water studies carried out in the framework of Snamprogetti corporate R&D. In particular, the pipe sectional capacity, required to sustain design loads, is analysed in relation to: • The fabrication technology i.e. the effect of cold expansion/compression (UOE/UOC) of TMCP plates on the mechanical and geometrical pipe characteristics; • The line pipe material i.e. the effect of the shape of the actual stress-strain curve and the Y/T ratio on the sectional performance, under combined loads; • The load combination i.e. the effect of the axial force and bending moment on the limit capacity against collapse and ovalisation buckling failure modes, under the considerable external pressure. International design guidelines are analysed in this respect, and experimental findings are compared with the ones from the application of proposed limit state equations and from dedicated FE simulations.

Nonlinear Dynamic and Bilinear Fatigue Performance of Composite Marine Risers in Deep Offshore Fields

2020 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Failure Modes ◽  
Thermal Protection ◽  
Growth Models ◽  
Limit State ◽  
Design Procedure ◽  
Crack Size ◽  
Unstable Fracture ◽  
Fatigue Reliability

Abstract Composite materials have drawn considerable consideration from the offshore business, basically because of their high explicit quality. Notwithstanding weight decrease, composites offer extra advantages, for example, fatigue resistance, damping, and thermal (protection) properties, and high erosion resistance. As a part of design procedure there are requirements of mechanical strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. Three dimensional nonlinear assessment of riser is carried out in time domain using ABAQUS/Aqua. The response time histories so obtained are used for the study of fatigue safety assessment of riser. It is based on a bi-linear approach to model fatigue crack growth and incorporates a failure limit to describe the interaction between rupture and plastic failure. Using Monte Carlo Simulation, tests of fatigue reliability and fatigue crack size evolution are obtained. It is observed that bilinear S-N curve and crack growth models leads to higher estimate of fatigue life. Sensitivity behavior pertinent to limit state adopted has been thoroughly examined. These outcomes implicate assessment of components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

Load Testing to Collapse Limit State of Barr Creek Bridge

2000 ◽  
Vol 1696 (1) ◽  
pp. 92-102 ◽  
Author(s):  
Nicholas Haritos ◽  
Anil Hira ◽  
Priyan Mendis ◽  
Rob Heywood ◽  
Armando Giufre
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Flexural Rigidity ◽  
Load Capacity ◽  
Limit State ◽  
Dynamic Test ◽  
Service Condition ◽  
Flat Slab ◽  
Testing Program ◽  
Static Testing

VicRoads, the road authority for the state of Victoria, Australia, has been undertaking extensive research into the load capacity and performance of cast-in-place reinforced concrete flat slab bridges. One of the key objectives of this research is the development of analytical tools that can be used to better determine the performance of these bridges under loadings to the elastic limit and subsequently to failure. The 59-year-old Barr Creek Bridge, a flat slab bridge of four short continuous spans over column piers, was made available to VicRoads in aid of this research. The static testing program executed on this bridge was therefore aimed at providing a comprehensive set of measurements of its response to serviceability level loadings and beyond. This test program was preceded by the performance of a dynamic test (a simplified experimental modal analysis using vehicular excitation) to establish basic structural properties of the bridge (effective flexural rigidity, EI) and the influence of the abutment supports from identification of its dynamic modal characteristics. The dynamic test results enabled a reliably tuned finite element model of the bridge in its in-service condition to be produced for use in conjunction with the static testing program. The results of the static testing program compared well with finite element modeling predictions in both the elastic range (serviceability loadings) and the nonlinear range (load levels taken to incipient collapse). Observed collapse failure modes and corresponding collapse load levels were also found to be predicted well using yield line theory.

Design and Analysis of Viscoelastic Seismic Dampers

2002 ◽  
Author(s):  
N. Shimizu ◽  
H. Nasuno ◽  
T. Yazaki ◽  
K. Sunakoda
Keyword(s):  
Finite Element ◽  
Constitutive Relation ◽  
Time Domain ◽  
Dynamic Properties ◽  
Design Procedure ◽  
Fe Analysis ◽  
Damping Capacity ◽  
Element Formulation ◽  
Element Analysis ◽  
Equivalent Viscous Damping

This paper describes a methodology of design and analysis of viscoelastic seismic dampers by means of the time domain finite element analysis. The viscoelastic constitutive relation of material incorporating with the fractional calculus has been derived and the finite element formulation based on the constitutive relation has been developed to analyze the dynamic property of seismic damper. A time domain computer program was developed by using the formulation. Dynamic properties of hysteresis loop, damping capacity, equivalent viscous damping coefficient, and equivalent spring constant are calculated and compared with the experimental results. Remarkable correlation between the FE analysis and the experiment is gained, and consequently the design procedure with the help of the FE analysis has been established.

Girth Weld Strength Matching Effect on Tensile Strain Capacity of Grade X70 High Strain Line Pipe

2018 ◽  
Author(s):  
Hisakazu Tajika ◽  
Takahiro Sakimoto ◽  
Tsunehisa Handa ◽  
Rinsei Ikeda ◽  
Joe Kondo
Keyword(s):  
High Strain ◽  
Limit State ◽  
Full Scale ◽  
Bending Test ◽  
High Grade ◽  
Line Pipe ◽  
Bending Tests ◽  
Strain Capacity ◽  
Pipeline Project ◽  
Pipe Bending

Recently high grade pipeline project have been planned in hostile environment like landslide in mountain area, liquefaction in reclaimed land or the frost heave in Polar Regions. Geohazards bring large scale ground deformation and effect on the varied pipeline to cause large deformation. Therefore, strain capacity is important for the pipeline and strain based design is also needed to keep gas transportation project in safe. High grade steel pipe for linepipe tends to have higher yield to tensile (Y/T) ratio and it has been investigated that the lower Y/T ratio of the material improves strain capacity in buckling and tensile limit state. In onshore pipeline project, pipe usually transported in 12 or 18m each and jointed in the field. Girth weld (GW) is indispensable so strength matching of girth weld towards pipe body is important. In this study strain capacity of Grade X70 high strain pipes with size of 36″ OD and 23mm WT was investigated with two types of experiments, which are full scale pipe bending tests and curved wide plate tests. The length of the specimen of full scale bending tests were approximately 8m and girth weld was made in the middle of joint length. A fixed internal pressure was applied during the bending test. Actual pipe situation in work was simulated and both circumferential and longitudinal stress occurred in this test. Test pipes were cut and welded, GTAW in first two layer and then finished by GMAW. In one pipe, YS-TS over-matching girth weld (OVM) joint was prepared considering the pipe body grade. For the other pipe, intentionally under-matching girth weld (UDM) joint was prepared. After the girth welding, elliptical EDM notch were installed in the GW HAZ as simulated weld defect. In both pipe bending tests, the buckling occurred in the pipe body at approximately 300mm apart from the GW and after that, deformation concentrated to buckling wrinkle. Test pipe breaking locations were different in the two tests. In OVM, tensile rupture occurred in pipe body on the backside of buckling wrinkle. In UDM, tensile rupture occurred from notch in the HAZ. In CWP test, breaking location was the HAZ notch. There were significant differences in CTOD growth in HAZ notch in these tests.

Development of Ultimate Strength Evaluation Method for Piping Subjected to Seismic Loads

2013 ◽  
Author(s):  
Hideo Machida ◽  
Hiromasa Chitose ◽  
Tatsuhiro Yamazaki
Keyword(s):  
Power Plants ◽  
Evaluation Method ◽  
Failure Modes ◽  
Limit State ◽  
Seismic Loading ◽  
Earthquake Resistance ◽  
State Function ◽  
Limit State Function ◽  
Input Acceleration ◽  
Resistance Tests

This paper reports the results of the study on the failure modes and limit loads of piping in nuclear power plants subjected to cyclic seismic loading. By investigating the past fracture tests and earthquake resistance tests, it became clear that dominant failure mode of piping was fatigue, and the effect of ratchet strain was negligible. Until now, the stress generated with the acceleration of an earthquake was classified into the primary stress. However, the relationship between the input acceleration and the seismic response displacement of the pipe observed from earthquake resistance tests is non-linear, and increasing rate of displacement is lower than that of input acceleration in elastic-plastic stress condition. Therefore, the seismic loading can be treated as displacement controlled loading. To evaluate the reliability-based critical acceleration, a limit state function was defined taking the variations in the fatigue strength or some parameters into consideration. By using the limit state function, the reliability was evaluated for the typical piping of boiling water reactor (BWR) plants subjected to cyclic seismic loading, and a partial safety factors were calculated. Based on these results, a fatigue curve corresponding to the target reliability was proposed.

Reliability analysis of wood I-joists

1993 ◽  
Vol 20 (4) ◽  
pp. 564-573 ◽  
Author(s):  
R. O. Foschi ◽  
F. Z. Yao
Keyword(s):  
Reliability Analysis ◽  
Carrying Capacity ◽  
Failure Modes ◽  
Limit State ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Element Analysis ◽  
Strength Limit ◽  
Reliability Method ◽  
Load Carrying

This paper presents a reliability analysis of wood I-joists for both strength and serviceability limit states. Results are obtained from a finite element analysis coupled with a first-order reliability method. For the strength limit state of load-carrying capacity, multiple failure modes are considered, each involving the interaction of several random variables. Good agreement is achieved between the test results and the theoretical prediction of variability in load-carrying capacity. Finally, a procedure is given to obtain load-sharing adjustment factors applicable to repetitive member systems such as floors and flat roofs. Key words: reliability, limit state design, wood composites, I-joist, structural analysis.

Effects of Local Metal Loss on Deformability of Line Pipes Subjected to Compressive Load

2005 ◽  
Author(s):  
Yoshikazu Hashimoto ◽  
Hiroshi Yatabe ◽  
Naoto Hagiwara ◽  
Noritake Oguchi
Keyword(s):  
Analytical Method ◽  
Compressive Load ◽  
Fe Analysis ◽  
Ground Movement ◽  
Metal Loss ◽  
Line Pipe ◽  
Parametric Studies ◽  
Scale Experiment ◽  
The Relationship ◽  
Good Agreement

In this paper, the deformability of line pipe with local metal loss was examined. A full-scale experiment and a finite element (FE) analysis were carried out for line pipe with local metal loss subjected to an axial compressive load. As a result, a good agreement was obtained between the analytical and experimental results. This indicated that the present analytical method was applicable to evaluate the deformability of line pipes with local metal loss subjected to a large ground movement. Parametric studies were then conducted to clarify the relationship between the geometry of the local metal loss and the deformability using the FE analytical method.

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