DNVGL-ST-F101 Combined Loading Criterion: Range of Application and Comparison With Other Criteria

2016 ◽  
Author(s):  
Olav Fyrileiv ◽  
Leif Collberg ◽  
Olav Aamlid
Keyword(s):  
Axial Force ◽  
Bending Moment ◽  
Design Criterion ◽  
Combined Loading ◽  
Moment Capacity ◽  
Offshore Pipeline ◽  
Global Buckling ◽  
Current Criterion ◽  
Set Up ◽  
Pipeline Design

The most essential pipeline design criterion is, of course, the pressure containment or bursting criterion normally determining the pipe wall thickness. When the pressure containment is ensured, the concern is often towards the action of the combined loading; pressure, axial force and bending moment. The combined loading criterion typically governs the installation and also set up requirements for other design issues such as seabed intervention and global buckling. The combined loading criterion of DNV GL submarine pipeline systems standard, DNV-OS-F101 or DNVGL-ST-F101 which is its new name [1], has been modified several times, and the current version was introduced in its present form in the 2007 revision of the offshore pipeline standard. This paper discusses the current criterion for combined loading, i.e. bending moment capacity, when the pipeline is under influence of axial force and internal over-pressure. The criterion is compared with several other similar criteria from previous revisions of the DNV GL pipeline and riser standards and from other offshore pipeline standards. In addition a comparison with physical and numerical tests is given, while the background and derivation of the criterion are given in an accompanying paper by Collberg and Levold [2].

Influence of Pressure in Pipeline Design: Effective Axial Force

2005 ◽  
Author(s):  
Olav Fyrileiv ◽  
Leif Collberg
Keyword(s):  
Axial Force ◽  
Local Buckling ◽  
External Pressure ◽  
Pressure Effects ◽  
Offshore Pipeline ◽  
Local Stresses ◽  
Global Buckling ◽  
The One ◽  
Pipeline Design ◽  
Force Concept

This paper discusses use of the effective axial force concept in offshore pipeline design in general and in DNV codes in particular. The concept of effective axial force or effective tension has been known and used in the pipeline and riser industry for some decades. However, recently a discussion about this was initiated and doubt on how to treat the internal pressure raised. Hopefully this paper will contribute to explain the use of this concept and remove the doubts in the industry, if it exists at all. The concept of effective axial force allows calculation of the global behaviour without considering the effects of internal and/or external pressure in detail. In particular, global buckling, so-called Euler buckling, can be calculated as in air by applying the concept of effective axial force. The effective axial force is also used in the DNV-RP-F105 “Free spanning pipelines” to adjust the natural frequencies of free spans due to the change in geometrical stiffness caused by the axial force and pressure effects. A recent paper claimed, however, that the effect was the opposite of the one given in the DNV-RP-F105 and may cause confusion about what is the appropriate way of handling the pressure effects. It is generally accepted that global buckling of pipelines is governed by the effective axial force. However, in the DNV Pipeline Standard DNV-OS-F101, also the local buckling criterion is expressed by use of the effective axial force concept which easily could be misunderstood. Local buckling is, of course, governed by the local stresses, the true stresses, in the pipe steel wall. Thus, it seems unreasonable to include the effective axial force and not the true axial force as used in the former DNV Pipeline Standard DNV’96. The reason for this is explained in detail in this paper. This paper gives an introduction to the concept of effective axial force. Further it explains how this concept is applied in modern offshore pipeline design. Finally the background for using the effective axial force in some of the DNV pipeline codes is given.

Combined Loading Criteria for Titanium Risers

2002 ◽  
Author(s):  
Olav Aamlid ◽  
Kristoffer Aronsen ◽  
Knut Olav Ronold ◽  
Kim Mo̸rk ◽  
Carl Baxter
Keyword(s):  
Axial Force ◽  
State Of The Art ◽  
Bending Moment ◽  
Uncertainty Modeling ◽  
Combined Loading ◽  
Design Equation ◽  
Data Basis ◽  
Load Effects ◽  
Calibration Study ◽  
Pipeline Design

DNV has, in cooperation with partners from the industry, carried out a joint industry project with the aim to develop recommended practice with respect to the design of titanium risers. As a part of this work, calibrated design formulae for combined loading have been established. The considered load situation is a combination of internal overpressure, bending moment and axial force. The data basis for the calibration study encompasses results from 12 finite element simulations with varying diameter to thickness ratio and internal pressure exposed to bending moment and axial force. With the design equation for steel risers, taken from the DNV Offshore Standard (OS-F201) Dynamic Risers, as a basis, the titanium data basis was investigated using state-of-the art methodology with an uncertainty modeling for load effects in compliance with recent research and development projects for risers and pipeline design. The outcome of this work is a design equation with reliability based calibration of safety factors that comply with the overall safety objective in the above offshore standard.

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.

Pipeline Design Methodology With Respect to Internal Corrosion

2009 ◽  
Author(s):  
Lars Lo̸berg Brækstad ◽  
Morten Hval ◽  
Vidar Henrik Halvorsen ◽  
Ole Magnus Holden
Keyword(s):  
Wall Thickness ◽  
Combined Loading ◽  
Design Criteria ◽  
Design Calculation ◽  
General Corrosion ◽  
Internal Corrosion ◽  
Corrosion Depth ◽  
Design Life ◽  
Global Buckling ◽  
Pipeline Design

The present paper originating from the Ormen Lange project, presents a methodology on how to treat the local wall thickness reduction due to internal corrosion with respect to different design criteria for production flowlines and spools. The methodology presented was implemented in pipeline design for the deepwater part of the project where water depth ranged from 250 m to 875 m. The combination of long design life and mildly corrosive well fluid requires a rather high corrosion allowance. With up to 10 mm general corrosion allowance accumulated over the 50 years design life of the pipelines, together with deep water, free spans, global buckling and possibilities for hydrate/ice formation inside the pipe, it would result in a much too conservative design if the full corrosion allowance is used for all aspects of pipeline design. In order to achieve a more realistic estimate of the effect of internal corrosion and a more optimal pipeline design, the internal corrosion was treated in different ways depending on where the corrosion is expected, and what design criteria is considered. By carrying out 2D and 3D finite element analyses of the pipe cross section with the predicted local corrosion distribution, where also the combined loading effects are included, it can be shown that for local buckling and propagating buckling during operation, a significant reduction in the average corrosion depth can be considered in design calculation. Therefore an equivalent corrosion depth, where the corrosion is distributed evenly for the different sections of the route can be estimated. This value can be used directly in the design calculations and allows optimisation of nominal wall thickness, on-bottom stability calculations, free span lengths, global buckling and cost driving factors such as pre- and post-lay seabed intervention and installation methodology.

Postbuckling Analysis of Snaked-Lay Pipelines Based on a New Deformation Shape

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Yuxiao Liu ◽  
Xin Li ◽  
Jing Zhou ◽  
Hualing Song
Keyword(s):  
Control Method ◽  
Compressive Force ◽  
Bending Moment ◽  
Element Model ◽  
Design Criterion ◽  
Lateral Buckling ◽  
Axial Compressive Force ◽  
Nonlinear Finite Element Model ◽  
Pipeline Design ◽  
Control Criterion

Lateral buckling must be considered in exposed HP/HT pipeline design. The snaked-lay method is an effective lateral buckling control method, a new deformation shape of snaked-lay pipeline is presented, and a control criterion of offset angle is also presented. When the offset angle is small or offset angle is large while the pipeline length of snaked-lay is too short or long, the maximum moments of postbuckling pipeline are large. For these problems, a new controlling method combined with snaked-lay and sleeper is proposed, which is named the SS method. Using Ansys, a nonlinear finite element model considering the interaction of seabed-sleeper-pipeline is established. The SS method is proved to be feasible to control lateral buckling for submarine pipelines. Based on critical axial compressive force and maximum bending moment, a design criterion of sleeper height is suggested.

scholarly journals 3D Centrifuge Modeling of the Effect of Twin Tunneling to an Existing Pile Group

2017 ◽  
Vol 7 (5) ◽  
pp. 2030-2040
Author(s):  
M. A. Soomro ◽  
M. A. Keerio ◽  
M. A. Soomro ◽  
D. K. Bangwar
Keyword(s):  
Axial Force ◽  
Urban Areas ◽  
Load Transfer ◽  
Three Dimensional ◽  
Bending Moment ◽  
Pile Group ◽  
Centrifuge Modeling ◽  
Pile Groups ◽  
Moment Capacity ◽  
Centrifuge Tests

In densely built urban areas, it is inevitable that tunnels will be constructed near existing pile groups. The bearing capacity of a pile group depends on shear stress along the soil-pile interface and normal stress underneath the pile toe while the two would be adversely affected by the unloading process of tunneling. Although extensive studies have been conducted to investigate the effects of tunnel construction on existing single piles, the influence of twin tunnel advancement on an existing pile group is merely reported in the literature. In this study, a series of three-dimensional centrifuge tests were carried out to investigate the response of an existing pile group under working load subjected to twin tunneling at various locations in dry Toyoura sand. In each twin tunneling test, the first tunnel is constructed near the mid-depth of the pile shaft, while the second tunnel is subsequently constructed either next to, below or right underneath the pile toe (Tests G_ST, G_SB and G_SU, respectively). Among the three tests, the 2nd tunnel excavated near the pile toe (Test G_ST) results in the smallest settlement but the largest transverse tilting (0.2%) of pile group. Significant bending moment was induced at the pile head (1.4 times of its bending moment capacity) due to the 2nd tunnel T. On the contrary, tunneling right underneath the toe of pile (i.e., Test G_SU) results in the smallest tilting but largest settlement of the pile group (4.6% of pile diameter) and incremental mobilisation of shaft resistance (13%). Due to stress release by the twin tunneling, the axial force taken by the front piles close to tunnels was reduced and partially transferred to the rear piles. This load transfer can increase the axial force in rear piles by 24%.

The Influence of Loads Superposition, Deterioration Due to Cracks and Residual Stresses on the Strength of Tubular Junction

2017 ◽  
Vol 68 (6) ◽  
pp. 1267-1273
Author(s):  
Valeriu V. Jinescu ◽  
Angela Chelu ◽  
Gheorghe Zecheru ◽  
Alexandru Pupazescu ◽  
Teodor Sima ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Residual Stresses ◽  
Bending Moment ◽  
Combined Loading ◽  
Torsional Moment ◽  
Calculation Methods ◽  
State Of Stress ◽  
Cracked Structures ◽  
Total Participation ◽  
Theoretical Results

In the paper the interaction of several loads like pressure, axial force, bending moment and torsional moment are analyzed, taking into account the deterioration due to cracks and the influence of residual stresses. A nonlinear, power law, of structure material is considered. General relationships for total participation of specific energies introduced in the structure by the loads, as well as for the critical participation have been proposed. On these bases: - a new strength calculation methods was developed; � strength of tubular cracked structures and of cracked tubular junction subjected to combined loading and strength were analyzed. Relationships for critical state have been proposed, based on dimensionless variables. These theoretical results fit with experimental date reported in literature. On the other side stress concentration coefficients were defined. Our one experiments onto a model of a pipe with two opposite nozzles have been achieved. Near one of the nozzles is a crack on the run pipe. Trough the experiments the state of stress have been obtained near the tubular junction, near the tip of the crack and far from the stress concentration points. On this basis the stress concentration coefficients were calculated.

scholarly journals Design and analysis of concrete-filled tubular flange girders under combined loading

2021 ◽  
pp. 136943322110015
Author(s):  
Rana Al-Dujele ◽  
Katherine Ann Cashell
Keyword(s):  
Finite Element ◽  
Axial Force ◽  
Failure Modes ◽  
Numerical Study ◽  
Combined Loading ◽  
Torsional Stiffness ◽  
Fe Model ◽  
Combined Effects ◽  
Element Analysis ◽  
Hollow Section

This paper is concerned with the behaviour of concrete-filled tubular flange girders (CFTFGs) under the combination of bending and tensile axial force. CFTFG is a relatively new structural solution comprising a steel beam in which the compression flange plate is replaced with a concrete-filled hollow section to create an efficient and effective load-carrying solution. These members have very high torsional stiffness and lateral torsional buckling strength in comparison with conventional steel I-girders of similar depth, width and steel weight and are there-fore capable of carrying very heavy loads over long spans. Current design codes do not explicitly include guidance for the design of these members, which are asymmetric in nature under the combined effects of tension and bending. The current paper presents a numerical study into the behaviour of CFTFGs under the combined effects of positive bending and axial tension. The study includes different loading combinations and the associated failure modes are identified and discussed. To facilitate this study, a finite element (FE) model is developed using the ABAQUS software which is capable of capturing both the geometric and material nonlinearities of the behaviour. Based on the results of finite element analysis, the moment–axial force interaction relationship is presented and a simplified equation is proposed for the design of CFTFGs under combined bending and tensile axial force.

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