Responses of Submarine Pipelines to Impacts in Soft Clay

2016 ◽  
Author(s):  
Yi Wang ◽  
Jixiang Yue ◽  
Menglan Duan ◽  
Zhang Yu ◽  
Yi Zhao
Keyword(s):  
Internal Pressure ◽  
Soft Clay ◽  
Local Deformation ◽  
Offshore Pipelines ◽  
Environmental Consequences ◽  
Deformation And Fracture ◽  
Subsea Pipelines ◽  
The Impact ◽  
Impact Damages ◽  
Dent Depth

Subsea pipelines have been widely used to transfer oil from platforms to the mainland near harbor anchorage zone, and they become increasingly susceptible to risks stemming from dropped object impact damages. The impact from dropped objects may lead to local deformation and fracture in the pipeline and vast economic and environmental consequences. In this research, the responses of continuously supported offshore pipelines subjected to transverse impacts caused by dropped objects are studied. For this, the impact on an internally pressurized pipeline resting on a flexible bed has been numerically simulated. A relatively extensive parametric study has then been carried out to examine effects from variations in the cement coating thickness, internal pressure, indenter shape, impact velocity and subsoil mechanical properties on the pipeline response. It has been noticed that the presence of internal pressure results in substantial decrease in the impact dent depth, causing the deformation to become spatially more localized. It has also been shown that the flexibility of pipe bed plays an important role in the impact energy dissipation.

Numerical Evaluation on Lateral Impact Resistance of Thermoplastic Composite Pipes in Terms of Internal Pressure Capacity

2020 ◽  
Author(s):  
J. Wang ◽  
C. Shi ◽  
G. Fu ◽  
Z. Liu ◽  
X. Bao ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Minimum Energy ◽  
Impact Resistance ◽  
Thermoplastic Composite ◽  
Economic Losses ◽  
Lateral Impact ◽  
Composite Pipes ◽  
Subsea Pipelines ◽  
The Impact ◽  
Static Simulation

Abstract Subsea pipelines are prone to be damaged by the falling objects from ships or offshore platforms, which may result in economic losses and pollution. The dimensions of dent were commonly used to evaluate the impact resistance of pipes made from carbon steel. Thermoplastic composite pipes (TCPs), due to their superior properties including corrosion resistance, thermal insulation, fast installation, etc., are increasingly used as the subsea pipelines. The TCP is made from thermoplastic resins and reinforced by continuous fibers. Because of the brittle nature of carbon fibers and glass fibers, the dimensions of dent are not suitable for assessment of impact resistance of a TCP. In the present work, a procedure was proposed using the internal pressure capacity as an indicator to evaluate the lateral impact resistance of a TCP. First, the internal pressure capacity of an intact TCP was evaluated. Second, a quasi-static simulation was conducted by applying a lateral compression force on the intact TCP using a rigid ball, until one of the composite plies in the reinforcement layer failed. The quasi-static simulation provided an initial estimate of the minimum energy that causes the start of damage of the TCP. Third, the impact simulations were performed by using a rigid ball hitting the TCP and, then, the internal pressure capacity of the damaged TCP was evaluated. Finally, the internal pressure capacity of the damaged pipe, compared with that of the intact pipe, was used as an indicator to evaluate the lateral impact resistance of the TCP. In this study, a glass-fiber reinforced polyethylene (PE) pipe of an inner diameter of 150 mm was modeled by ABAQUS to illustrate the procedure. A theoretical method was proposed to calculate the impact energy of a dropped object in a shallow water. The example studied in the present work showed that the modeled TCP was not strong enough to survive the lateral impact caused by the dropped object and should be buried to a certain depth beneath the seabed if used as a subsea pipeline.

New Limit State Functions for Determining the Puncture Resistance to External Force

2002 ◽  
Author(s):  
Jianhui Liu ◽  
Andrew Francis
Keyword(s):  
Internal Pressure ◽  
Failure Mode ◽  
External Force ◽  
Maximum Stress ◽  
Limit State ◽  
Pipe Material ◽  
Stress Strain ◽  
Indentation Force ◽  
The Impact ◽  
Dent Depth

Traditionally, a key component of the design philosophy applied to high-pressure pipelines has been the stipulation that the nominal hoop stress is less than some fraction of the specified minimum yield strength (SMYS). However, more recently both designers and operators have recognised that whilst this approach generally leads to conservatively safe designs, there may be some situations in which the conservatism is not adequate. This has resulted in a move towards limit state, and structural reliability based, methods that address actual failure modes, and consequently the contributions to structural integrity of other factors in addition to stress. One such failure mode is the puncture of a pipeline wall due an external force. This situation can arise from the impact of excavating machinery for onshore pipelines or drop objects and anchors for offshore lines. A limit state function describing this failure mode is given in DNV guidelines No 13. However, this function does not take account of the internal pressure. In this paper the influence of pressure on the pipeline indentation is addressed using both theoretical and finite element analyses. A closed-form solution of force-deformation relationship based on a consideration of rigid-plastic deformation theory, that gives a good agreement with results from both FE analyses and experimental tests, is presented. The analytical results show that indentation force, and the maximum stress/strain, required to produce a given dent depth, increase with increasing internal pressure. However, the relationship between indentation force and maximum stress/strain is not sensitive to internal pressure. The analysis therefore shows that an indentation force criterion governed solely by the dent depth, such as that given in DNV guidelines No. 13, may be highly unconservative when the pressure in the pipeline is high. Consequently, a new local denting criterion for puncture of pressurised pipes, which is based the maximum acceptable strain of the pipe material, and thereby removes the above unconservatsim, has been proposed and is presented in this paper.

Pipe-Soil Interactions for a Pipeline With Strakes on a Furrowed Seabed

2014 ◽  
Author(s):  
Mark Brunner ◽  
Qiang Bai
Keyword(s):  
Soft Clay ◽  
Pipeline System ◽  
Test Case ◽  
Element Analysis ◽  
Beam Elements ◽  
User Subroutine ◽  
Viv Suppression ◽  
Subsea Pipelines ◽  
The Impact ◽  
Penetration Depths

Although significant pipe-soil interaction information is now available in the industry for shallowly-embedded, cylindrical pipelines on a flat seabed, there is little information available for subsea pipelines with vortex-induced vibration (VIV) suppression strakes on a furrowed seabed. A heavily furrowed seabed may have multiple free spans that are subjected to seabed currents and potential VIV. To suppress VIV at the free spans, strakes are often applied to the pipeline over the entire length of the furrowed area. At the tops of the furrows, the pipeline will penetrate further into a soft clay seabed due to the weight of adjacent free spans. Significantly different pipe-soil interactions are possible in these areas, especially with the presence of VIV suppression strakes. Accounting for these differences is essential when assessing thermal expansion issues, such as global lateral buckling and pipeline walking. This paper presents the findings for a test case of a pipeline with strakes on a furrowed seabed and provides suggestions for a user subroutine to be used for a pipeline system with beam elements in a finite-element analysis. The CEL method is first used to assess the impact of straked-pipeline penetration into a flat, soft-clay seabed, then to assess lateral and axial pipe resistances at different penetration depths. This information is used to develop a user subroutine for beam elements to further assess the pipeline on a furrowed seabed, in which the effects of vertical pipeline load and penetration on the lateral soil resistance are included. The test case also considers a typical analysis for a pipeline subjected to elevated temperature and pressure cycles.

Assessment of the impact of ice gouging on the Arctic marine pipeline systems

2021 ◽  
pp. 284-292
Author(s):  
Ирина Георгиевна Силина ◽  
Вадим Андреевич Иванов ◽  
Сергей Валерьевич Знаменщиков
Keyword(s):  
Oil And Gas ◽  
Systems Design ◽  
The Arctic ◽  
Burial Depth ◽  
Offshore Pipelines ◽  
Offshore Pipeline ◽  
Distribution Features ◽  
Pipeline Systems ◽  
Subsea Pipelines ◽  
The Impact

Для исследования методик оценки влияния ледовой экзарации на подводные трубопроводы проанализирована отечественная и зарубежная нормативно-техническая база в области проектирования, строительства и эксплуатации морских трубопроводных систем, подробно рассмотрены общие подходы к решению данного вопроса. Систематизирован опыт строительства и эксплуатации трубопроводов в условиях замерзающих акваторий, представлены способы их защиты от повреждений в результате дрейфа ледовых образований. Дана оценка характера формирования и особенностей распределения ледово-экзарационных форм по глубине акваторий. Показано, что существующая методология оценки воздействия ледовой экзарации на морские трубопроводы не позволяет в полной мере учесть льдогрунтовое взаимодействие. Установлена целесообразность разработки критериев для определения минимальной безопасной глубины заложения подводных трубопроводов в районах с дрейфующими льдами. Обозначены направления дальнейших исследований механизмов ледового выпахивания, деформаций прилежащего к трубе грунтового массива и поведения заглубленного трубопровода. Полученные результаты позволят дополнить существующую методологию учета воздействия ледовой экзарации на морские трубопроводы, прокладываемые в замерзающих акваториях, с целью обеспечения их безопасности и надежности. To consider the methods of assessing the impact of ice gouging phenomenon on subsea oil and gas pipelines, the authors analyzed Russian and foreign codes and standards in the field of offshore pipeline systems design, construction and operation, and also considered in detail scientific approaches to investigate this issue. Within the framework of the analysis of peculiarities of offshore pipelines operation in areas with ice gouging, systematization of experience gained from pipeline systems operation in freezing waters was carried out, and methods of pipeline protection from damages caused by drifting ice formations were considered. The assessment of ice induced gouges formation and distribution features is performed. It is shown that the assessment methods presented in current codes and standards to determine the ice gouging impact on marine pipelines do not allow to directly take into account the ice-soil interaction. The feasibility of developing criteria for determining the minimum required burial depth for subsea pipelines in areas with ice gouging is determined. The directions of further research to ensure safe and failure-free operation of subsea pipeline systems in freezing water areas are presented.

Ratcheting assessment of corroded elbow pipes subjected to internal pressure and cyclic bending moment

2021 ◽  
pp. 030932472198989
Author(s):  
Ali Salehi ◽  
Armin Rahmatfam ◽  
Mohammad Zehsaz
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Internal Pressure ◽  
Bending Moment ◽  
Axial Direction ◽  
Hoop Strain ◽  
Cyclic Bending ◽  
High Fatigue ◽  
The Impact ◽  
Cyclic Bending Moment

The present study aimed to study ratcheting strains of corroded stainless steel 304LN elbow pipes subjected to internal pressure and cyclic bending moment. To this aim, spherical and cubical shapes corrosion are applied at two depths of 1 mm and 2 mm in the critical points of elbow pipe such as symmetry sites at intrados, extrados, and crown positions. Then, a Duplex 2205 stainless steel elbow pipe is considered as an alternative to studying the impact of the pipe materials, due to its high corrosion resistance and strength, toughness, and most importantly, the high fatigue strength and other mechanical properties than stainless steel 304LN. In order to perform numerical analyzes, the hardening coefficients of the materials were calculated. The results highlight a significant relationship between the destructive effects of corrosion and the depth and shape of corrosion, so that as corrosion increases, the resulting destructive effects increases as well, also, the ratcheting strains in cubic corrosions have a higher growth rate than spherical corrosions. In addition, the growth rate of the ratcheting strains in the hoop direction is much higher across the studied sample than the axial direction. The highest growth rate of hoop strain was observed at crown and the highest growth rate of axial strains occurred at intrados position. Altogether, Duplex 2205 material has a better performance than SS 304LN.

Coda Waves for Health Monitoring of Composites Under Low-Velocity Impact

2021 ◽  
Author(s):  
Subal Sharma ◽  
Vinay Dayal
Keyword(s):  
Ultrasonic Waves ◽  
Coda Waves ◽  
Low Velocity Impact ◽  
Coda Wave ◽  
Low Velocity ◽  
Fibrous Composite Material ◽  
Velocity Impact ◽  
Isotropic Composite ◽  
The Impact ◽  
Impact Damages

Abstract Coda waves have been shown to be sensitive to lab-controlled defects such as very small holes in fibrous composite material. In the real world, damages are subtler and more irregular. The main objective of this work is to investigate coda wave capability to detect low-velocity impact damages. The emphasis is to detect the presence of barely visible impact damages using ultrasonic waves. Detection of incipient damage state is important as it will grow over the life of the structure. Differential features, previously used in similar work, have been utilized to detect realistic impact damages on carbon fiber composites. Quasi-isotropic composite laminates were subjected to low-velocity impact energy ranging from 2J to 4.5J. Two differential features reported could be used detect the presence of damage. It is also observed that ply orientation can be a deterministic factor for indicating damages. The size and shape of the impact damage has been characterized using ultrasonic C-scans. Results indicate that coda waves can be used for the detection of damage due to low-velocity impact.

Fatigue Behaviour of Dented Pipes Under Internal Pressure: A Numerical-Experimental Approach

2018 ◽  
Author(s):  
Mario A. Polanco-Loria ◽  
Håvar Ilstad
Keyword(s):  
Fatigue Life ◽  
Internal Pressure ◽  
Fatigue Behavior ◽  
Crack Depth ◽  
Fatigue Behaviour ◽  
Experimental Methodology ◽  
Experimental Program ◽  
Metal Loss ◽  
Life Predictions ◽  
Dent Depth

This work presents a numerical-experimental methodology to study the fatigue behavior of dented pipes under internal pressure. A full-scale experimental program on dented pipes containing gouges were achieved. Two types of defects were studied: metal loss (plain dent) and sharp notch. Both defects acting independently reduce the fatigue life performance but their combination is highly detrimental and must be avoided. We did not find a severity threshold (e.g. dent depth or crack depth) where these defects could coexist. In addition, based on numerical analyses we proposed a new expression for stress concentration factor (SCF) in line with transversal indentation. This information was successfully integrated into a simple fatigue model where the fatigue life predictions were practically inside the window of experimental results.

scholarly journals A copula-based assessment of Bartlett–Lewis type of rainfall models for preserving drought statistics

2013 ◽  
Vol 10 (6) ◽  
pp. 7469-7516 ◽  
Author(s):  
M. T. Pham ◽  
W. J. Vanhaute ◽  
S. Vandenberghe ◽  
B. De Baets ◽  
N. E. C. Verhoest
Keyword(s):  
Time Series ◽  
Important Variable ◽  
Drought Severity ◽  
Test Case ◽  
Rainfall Time Series ◽  
Climate Data ◽  
Drought Duration ◽  
Environmental Consequences ◽  
Stochastic Point Process ◽  
The Impact

Abstract. Of all natural disasters, the economic and environmental consequences of droughts are among the highest because of their longevity and widespread spatial extent. Because of their extreme behaviour, studying droughts generally requires long time series of historical climate data. Rainfall is a very important variable for calculating drought statistics, for quantifying historical droughts or for assessing the impact on other hydrological (e.g. water stage in rivers) or agricultural (e.g. irrigation requirements) variables. Unfortunately, time series of historical observations are often too short for such assessments. To circumvent this, one may rely on the synthetic rainfall time series from stochastic point process rainfall models, such as Bartlett–Lewis models. The present study investigates whether drought statistics are preserved when simulating rainfall with Bartlett–Lewis models. Therefore, a 105 yr 10 min rainfall time series obtained at Uccle, Belgium is used as test case. First, drought events were identified on the basis of the Effective Drought Index (EDI), and each event was characterized by two variables, i.e. drought duration (D) and drought severity (S). As both parameters are interdependent, a multivariate distribution function, which makes use of a copula, was fitted. Based on the copula, four types of drought return periods are calculated for observed as well as simulated droughts and are used to evaluate the ability of the rainfall models to simulate drought events with the appropriate characteristics. Overall, all Bartlett–Lewis type of models studied fail in preserving extreme drought statistics, which is attributed to the model structure and to the model stationarity caused by maintaining the same parameter set during the whole simulation period.

Energy Efficiency of Vehicles

2020 ◽  
Author(s):  
Doug Carroll
Keyword(s):  
Energy Efficiency ◽  
Scientific Knowledge ◽  
Fuel Economy ◽  
Environmental Consequences ◽  
Energy Models ◽  
The World ◽  
Different Types ◽  
The Impact ◽  
The Relationship ◽  
Rational Decisions

Energy Efficiency of Vehicles educates readers about energy and the environment and the relationship between the energy we use and the environment. The world is at a point in time when people need to make very important decisions about energy in the next few decades. This book enables readers to utilize our scientific knowledge to make good rational decisions. Energy Efficiency of Vehicles provides information on: Calculations related to energy, power, and efficiency, and the impact of using different types of energy on the environment. Environmental consequences of consuming energy. Models related to impact of city driving on the energy efficiency and fuel economy of cars and trucks.

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