Hydromechanics of submarine pipelines: design problems

1985 ◽  
Vol 12 (4) ◽  
pp. 863-874 ◽  
Author(s):  
John B. Herbich
Keyword(s):  
Field Measurements ◽  
External Pressure ◽  
Pressure Effects ◽  
Bottom Current ◽  
Wave Forces ◽  
Ocean Environment ◽  
Scour Protection ◽  
Hydrodynamic Wave ◽  
Pipeline Failures ◽  
Design And Construction

In recent years, the size, number, and applications of offshore pipelines have been steadily increasing. The design and construction of pipelines in offshore cold regions calls for special measures (such as deep burial) because of seabed scouring caused by ice.Various societies and associations have pointed out the deficiencies in the state-of-the-art areas of environmental, design, and construction factors, particularly those dealing with structural, external pressure effects, and depth of burial. It has also been recommended that more data be obtained in order to fully evaluate pipeline–soil interaction. Also, field measurements of velocities, accelerations, and forces causing scour around pipelines would greatly enhance our understanding of offshore pipeline behavior.Offshore pipelines fail in many different ways, and each mode of failure should be examined individually. Because of the complexity of the ocean environment it is quite difficult to evaluate pipeline failures in detail.Environmental factors such as hydrodynamic wave forces and currents, buoyancy forces due to liquefaction of sediment, and scouring potential are presented. The dynamics of scour, incipient sediment motion, depth of scour, and scour patterns around pipelines are also reviewed as well as the maximum scour depths as a function of bottom current velocity.Methods for scour protection in shallow and deep water are described as well as the need for inspection and maintenance to prevent failures. Key words: pipelines, offshore, hydrodynamic forces, cover, scour.

scholarly journals Rational Modeling of Ultimate Pipe Strength Under Bending and External Pressure

2000 ◽  
Author(s):  
André C. Nogueira ◽  
Glenn A. Lanan
Keyword(s):  
Deep Water ◽  
Limit State ◽  
Local Buckling ◽  
External Pressure ◽  
Pressure Effects ◽  
Combined Loading ◽  
Empirical Prediction ◽  
Limit State Design ◽  
Controlled Conditions ◽  
Offshore Pipeline

The capacity of pipelines to resist collapse or local buckling under a combination of external pressure and bending moment is a major aspect of offshore pipeline design. The importance of this loading combination increases as oil and gas projects in ultra deep-water, beyond 2,000-m water depths, are becoming reality. The industry is now accepting, and codes are explicitly incorporating, limit state design concepts such as the distinction between load controlled and displacement controlled conditions. Thus, deep-water pipeline installation and limit state design procedures are increasing the need to understand fundamental principles of offshore pipeline performance. Design codes, such as API 1111 (1999) or DNV (1996, 2000), present equations that quantify pipeline capacities under combined loading in offshore pipelines. However, these equations are based on empirical data fitting, with or without reliability considerations. Palmer (1994) pointed out that “it is surprising to discover that theoretical prediction [of tubular members under combined loading] has lagged behind empirical prediction, and that many of the formula have no real theoretical backup beyond dimensional analysis.” This paper addresses the ultimate strength of pipelines under combined bending and external pressure, especially for diameter-to-thickness ratios, D/t, less than 40, which are typically used for deep water applications. The model is original and has a rational basis. It includes considerations of ovalization, anisotropy (such as those caused by the UOE pipe fabrication process), load controlled, and displaced controlled conditions. First, plastic analysis is reviewed, then pipe local buckling under pure bending is analyzed and used to develop the strength model. Load controlled and displacement controlled conditions are a natural consequence of the formulation, as well as cross section ovalization. Secondly, external pressure effects are addressed. Model predictions compare very favorably to experimental collapse test results.

scholarly journals WAVE ACTION ON LARGE OFF-SHORE STRUCTURES

1976 ◽  
Vol 1 (15) ◽  
pp. 129 ◽  
Author(s):  
C.J. Apelt ◽  
A. Macknight
Keyword(s):  
Numerical Methods ◽  
Water Surface ◽  
Theoretical Method ◽  
Wave Force ◽  
Wave Action ◽  
Tidal Range ◽  
Scale Model ◽  
Wave Forces ◽  
Accurate Calculation ◽  
Scour Protection

The paper describes investigations carried out in order to design for the wave action, both wave force and scour, on large off-shore berthing structures sited approximately 1.3 miles (2.1 km) off-shore near Hay Point, North Queensland, in 56 feet (17 m) of water at low tide, the tidal range being 20 feet (6 m). The region is a cyclone area and the structures must be capable of withstanding attack from maximum predicted waves with period of 8.25 seconds and amplitude of 24 feet (7.3 m). The main units in the berthing structures are concrete caissons sunk on to the ocean bed and the largest of these have plan dimensions of approximately 150 feet (46.7 m) by 135 feet (41.4 m) with four columns approximately 40 feet (12.2 m) square projecting through the water surface. No theoretical method available at the time of the investigation was capable of accurate calculation of wave forces on these structures. A scale model was tested to obtain wave forces and the paper compares results from the model with those of numerical methods and discusses the application of the results to the design functions. Scour effects were also modelled and the results used as the basis for design of scour protection.

Pipe Response Under Concentrated Lateral Loads and External Pressure

2005 ◽  
Author(s):  
Spyros A. Karamanos ◽  
Charis Eleftheriadis
Keyword(s):  
Three Dimensional ◽  
External Pressure ◽  
Absorption Capacity ◽  
Pressure Effects ◽  
Analytical Models ◽  
Dimensional Case ◽  
Two Dimensional ◽  
Lateral Loads ◽  
Offshore Pipelines ◽  
Different Levels

The present paper examines the denting deformation of offshore pipelines and tubular members (D/t≤50) subjected to lateral (transverse) quasi-static loading in the presence of uniform external pressure. Particular emphasis is given on pressure effects on the ultimate lateral load of tubes and on their energy absorption capacity. Pipe segments are modeled with shell finite elements, accounting for geometric and material nonlinearities, and give very good predictions compared with test data from non-pressurized pipes. Lateral loading between two rigid plates, a two-dimensional case, is examined first. Three-dimensional case, are also analyzed, where the load is applied either through a pair of opposite wedge-shaped denting tools or a single spherical denting tool. Load-deflection curves for different levels of external pressure are presented, which indicate that pressure has significant influence on pipe response and strength. Finally, simplified analytical models are proposed for the two-dimensional and three-dimensional load configurations, which yield closed-form expressions, compare fairly well with the finite element results and illustrate some important features of pipeline response in a clear and elegant manner.

Mechanics Analysis and Construction Method of Prestressed Concrete Pipe

2013 ◽  
Vol 351-352 ◽  
pp. 30-33
Author(s):  
Wei Wu ◽  
Jing Ji
Keyword(s):  
Prestressed Concrete ◽  
Simulation Analysis ◽  
External Pressure ◽  
Construction Process ◽  
Work Process ◽  
Finite Element Software ◽  
Concrete Pipe ◽  
Mechanics Analysis ◽  
Analysis Design ◽  
Design And Construction

Simulation analysis on prestressed concrete pipe was carried out by using finite element software ANSYS. The internal and external pressure which the pipeline is subject to is simulated in real work process, and deformation and stress distribution of building pipeline structure are got. We have great understanding in the mechanical properties, at the same time give a detailed introduction for the prefabrication and on-site construction process. Three aspects in this paper for analysis, design and construction can provide safe and reliable reference for design and construction of similar pipeline structure.

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.

scholarly journals ANALYSIS OF FLUID FLOW IMPACT OSCILLATORY PRESSURES WITH AIR ENTRAPMENT AT STRUCTURES

2017 ◽  
pp. 31 ◽  
Author(s):  
Robert Brian Mayon ◽  
Zoheir Sabeur ◽  
Mingyi Tan ◽  
Kamal Djidjeli
Keyword(s):  
Fluid Flow ◽  
Numerical Model ◽  
Air Entrainment ◽  
Pressure Effects ◽  
Impact Pressure ◽  
Wave Loading ◽  
Air Entrapment ◽  
Wave Impact ◽  
Hydrodynamic Wave ◽  
The Impact

Hydrodynamic wave loading at coastal structures is a complex phenomenon to quantify. The chaotic nature of the fluid flow field as waves break against such structures has presented many challenges to Scientists and Engineers for the design of coastal defences. The provision of installations such as breakwaters to resist wave loading and protect coastal areas has evolved predominantly through empirical and experimental observations. This is due to the challenging understanding and quantification of wave impact energy transfer processes with air entrainment at these structures. This paper presents a numerical investigation on wave loading at porous formations including the effects of air entrapment. Porous morphologies generated from cubic packed spheres with varying characteristics representing a breakwater structure are incorporated into the numerical model at the impact interface and the effect on the pressure field is investigated as the wave breaks. We focus on analysing the impulse impact pressure as a surging flow front impacts a porous wall. Thereafter we investigate the multi-modal oscillatory wave impact pressure signals which result from a transient plunging breaker wave impinging upon a modelled porous coastal protective structure. The high frequency oscillatory pressure effects resulting from air entrapment are clearly observed in the simulations. A frequency domain analysis of the impact pressure responses is undertaken. We show that the structural morphology of the porous assembly influences the pressure response signal recorded during the impact event. The findings provide good confidence on the robustness of our numerical model particularly for investigating the air bubbles formation and their mechanics at impact with porous walls.

Effect of Ice and Wave Forces on the Design of Canadian Offshore Lighthouses

1975 ◽  
Vol 2 (2) ◽  
pp. 138-153
Author(s):  
J. V. Danys
Keyword(s):  
Wave Forces ◽  
Contact Areas ◽  
Impact Forces ◽  
The Pacific ◽  
Principal Factors ◽  
Main Factors ◽  
Ice Forces ◽  
Design And Construction

Wave and ice forces are the main factors to be considered when designing offshore lighthouses. With the exception of the Pacific and the southern part of the Atlantic coasts, the design of the majority of Canadian lighthouses is governed by the ice forces. For many years very little was known about the magnitude of ice forces. Experience and judgement were the principal factors in the design and construction of such unique structures as lighthouses in the middle of a lake. Even now knowledge of these forces is not complete and there are still no Canadian design standards.Sloped surfaces and cylindrical or conical shapes are used for the substructures of the lightpiers and the ice-structure contact areas are designed as small as practical to reduce ice impact forces.

Metal–insulator transition in NiS2−xSex: chemical vs external pressure effects

2011 ◽  
Vol 31 (1) ◽  
pp. 18-22 ◽  
Author(s):  
C. Marini ◽  
M. Valentini ◽  
A. Perucchi ◽  
P. Dore ◽  
D. D. Sarma ◽  
...  
Keyword(s):  
External Pressure ◽  
Insulator Transition ◽  
Pressure Effects ◽  
Metal Insulator Transition ◽  
Metal Insulator

scholarly journals THE DESIGN AMD CONSTRUCTION OF THE NEW OIL PORT IN DALIAN, C.P.R.

1980 ◽  
Vol 1 (17) ◽  
pp. 125
Author(s):  
Zhu Zhuang
Keyword(s):  
Mooring Line ◽  
Wave Forces ◽  
Exciting Forces ◽  
The Impact ◽  
Design And Construction

The construction of New Oil Port in Dalian, C.P.R., was started around the end 1974 and completed in autumn 1976.In this paper a summary of the essential considerations in design and construction of this oil port, such as the planning of the pier, the determination of exciting forces (namely wave forces, forces due to earthquake, mooring line forces and berthing forces due to the impact of tanker on the fenders)on structures, the design of the large cylindrical cassion with a diameter of 9m and a height up to 19.7m and the construction of connecting bridges by two types, is presented.

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